Nanoco Technologies Ltd. v. Samsung Electronics Co., Ltd. et al

Filing 1

COMPLAINT against Samsung Advanced Institute of Technology, Samsung Display Co., Ltd., Samsung Electronics America, Inc., Samsung Electronics Co., Ltd., Samsung Electronics Co., Ltd. Visual Display Division ( Filing fee $ 400 receipt number 0540-7664317.), filed by Nanoco Technologies Ltd.. (Attachments: # 1 Civil Cover Sheet, # 2 Exhibit 1, # 3 Exhibit 2, # 4 Exhibit 3, # 5 Exhibit 4, # 6 Exhibit 5, # 7 Exhibit 6, # 8 Exhibit 7, # 9 Exhibit 8, # 10 Exhibit 9, # 11 Exhibit 10, # 12 Exhibit 11, # 13 Exhibit 12, # 14 Exhibit 13, # 15 Exhibit 14)(Henry, Claire)

Exhibit 3

US007867557B2

(12) United States Patent

(10) Patent No.:
(45) Date of Patent:

Pickett et al.

(56)

(54) NANOPARTICLES
Steven Daniels, Manchester (GB); Paul
O’Brien, High Peak (GB)

References Cited
2,769,838 A

11/1956 Matter et al.

(Continued)

(73) Assignee: Nanoco Technologies Limited,
Manchester (GB)
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.C. 154(b) by 168 days.

*Jan. 11, 2011

U.S. PATENT DOCUMENTS

(75) Inventors: Nigel Pickett, East Croyden (GB);

(*) Notice:

US 7,867,557 B2

FOREIGN PATENT DOCUMENTS
CN

1394599

2, 2003

(Continued)
OTHER PUBLICATIONS

This patent is Subject to a terminal dis
claimer.

(21) Appl. No.:

11/997,973

(22) PCT Filed:

Aug. 14, 2006

(86). PCT No.:

PCT/GB2OO6/OO3O28

S371 (c)(1),
(2), (4) Date:

Feb. 5, 2008

(87) PCT Pub. No.: WO2007/020416
PCT Pub. Date: Feb. 22, 2007
(65)

Prior Publication Data

US 2008/O220593 A1

Sep. 11, 2008

(30)
Foreign Application Priority Data
Aug. 12, 2005 (GB) ................................. O516598.O

(51) Int. Cl.
C30B 700
B82B3/00

(2006.01)
(2006.01)

(52) U.S. Cl. ....................... 427/214; 427/212; 427/215;
428/402; 428/403; 428/404: 428/405; 428/406
(58) Field of Classification Search ................... 257/14;
427/212, 214, 215; 428/403, 404, 405
See application file for complete search history.

Zhong et al., “Composition-Tunable ZnxCu1-xSe Nanocrystals with
High Luminescence and Stability”, Journal of American Chemical
Society. (2003).*

(Continued)
Primary Examiner Michael Cleveland
Assistant Examiner—Lisha Jiang
(74) Attorney, Agent, or Firm Bingham McCutchen LLP
(57)

ABSTRACT

Method for producing a nanoparticle comprised of core, first
shell and second shell semiconductor materials. Effecting
conversion of a core precursor composition comprising sepa
rate first and second precursor species to the core material and
then depositing said first and second shells. The conversion is
effected in the presence of a molecular cluster compound
under conditions permitting seeding and growth of the nano
particle core. Core/multishell nanoparticles in which at least
two of the core, first shell and second shell materials incor

porate ions from groups 12 and 15, 14 and 16, or 11, 13 and 16
of the periodic table. Core/multishell nanoparticles in which
the second shell material incorporates at least two different
group 12 ions and group 16 ions. Core/multishell nanopar
ticles in which at least one of the core, first and second

semiconductor materials incorporates group 11, 13 and 16
ions and the other semiconductor material does not incorpo
rate group 11, 13 and 16 ions.
17 Claims, 12 Drawing Sheets

US 7,867,557 B2
Page 2
U.S. PATENT DOCUMENTS

WO
WO

WO-97/101.75
WO-OOf 17642

WO

WO-O2,04527

WO
WO
WO
WO
WO
WO
WO
WO
WO
WO
WO
WO
WO
WO

WO-0224623
WO-O2,29140
WO-03/099708
WO-2004OO8550
WO-2004/033366
WO-2004/066361
WO-2004O65362
WO-2005/021150
WO-2005,106082
WO-2005106082
WO-2005 123575
WO-2006001848
WO-2006/017125
WO-2006O75974

6,815,064 B2 * 1 1/2004 Treadway et al. ........... 428,403

WO

WO-2006/116337

11, 2006

6,855,551 B2

2/2005 Bawendi et al.

WO

WO-2006 118543 A1

11 2006

6,914,264 B2

7/2005 Chen et al.

WO

WO-2006134599 A1

12/2006

7,041,362 B2

5, 2006 Barbera-Guillem

WO

WO-2007020416 A1

2, 2007

WO

WO-2007/049052

5/2007

3,524,771 A
4,609.689
6,114,038
6,207,229
6,221,602
6,261,779
6,322.901
6,326,144
6,333,110
6,379,635
6,423,551
6.426,513
6,607,829
6,660,379
6,699,723

A
A
B1
B1
B1
B1
B1
B1
B2
B1
B1
B1
B1
B1

7,151,047 B2

8, 1970 Green ........................ 136,203
9, 1986
9, 2000
3, 2001
4/2001
7/2001
11/2001
12/2001
12/2001
4/2002
7/2002
7/2002
8, 2003
12/2003
3, 2004

Schwartz et al.
Castro et al.
Bawendi et al.
Barbera-Guillem et al.
Barbera-Guillem et al.
Bawendi et al.
Bawendi et al.
Barbera-Guillem
O'Brien et al.
Weiss et al.
Bawendi et al.
Bawendi et al.
Lakowicz et al.
Weiss et al.

12/2006 Chan et al.

3, 1997
3, 2000

1, 2002
A2

A2
A2
A1
A1
A2

A1

3, 2002
4/2002
12/2003
1, 2004
4/2004
8, 2004
8, 2004
3, 2005
11, 2005
11, 2005
12/2005
1, 2006
2, 2006
T 2006

7,235,361 B2
7,264,527 B2
2003, OO17264 A1

6, 2007 Bawendi et al.
9, 2007 Bawendi et al.
1, 2003 Treadway et al.

WO
WO
WO

WO-2007/060591
WO-2007-060591 A
WO-2007049052 A2

5/2007
5/2007
5/2007

2003/0106488 A1

6/2003 Huang et al.

WO

WO-2007/065039

6, 2007

WO
WO
WO
WO
WO
WO

WO-2007 102799
WO-2008O13780
WO-2008.054874
WO-2008133660
WO-2009016354
WO-2009010681.0

2003/0148024
2004.0007169
2004/01 10002
2004/O110347
2004/0178390
2004/O250745

A1
A1
A1
A1
A1
A1

8, 2003
1/2004
6, 2004
6, 2004
9, 2004
12, 2004

Kodas et al.
Ohtsu et al.
Kim et al.
Yamashita
Whiteford et al.
Ogura et al.

A2
A2
A2
A2
A1
A1

9, 2007
1, 2008
5, 2008
11, 2008
2, 2009
9, 2009

2005/0129.947 A1

6/2005 Peng et al. .................. 428,403

2005, 0145853 A1

7/2005 Sato et al.

2006, OO19098 A1

1/2006 Chan et al.

2006, OO61017 A1
2006, OO68154 A1
2006/01 18757 A1

3, 2006 Strouse et al.
3, 2006 Parce et al.
6, 2006 Klimov et al.

2006/0130741 A1

6/2006 Peng et al.

Sheng et al., “In-Situ Encapsulation of Quantum Dots into Polymer

2007/0012941
2007.0034.833
2007/0059.705
2007, 0104865

1/2007
2/2007
3/2007
5/2007

Microspheres'. Langmuir, (2006), vol. 22(8), pp. 3782-3790.*
Agger, J.R. et al., J. Phys. Chem. B (1998) 102, p. 3345.
Aldana, J. et al. “Photochemical Instability of CdSe Nanocrystals
Coated by Hydrophilic Thiols”. J. Am. Chem. Soc. (2001), 123:

A1
A1
A1
A1

Cheon
Parce et al.
Lu et al.
Pickett ....................... 427,212

OTHER PUBLICATIONS

Cumberland et al., “Inorganic Clusters as Single-Source Precursors
for Preparation of CdSe, ZnSe, and CdSe/ZnS Nanomaterials.”
Chemistry of Materials (2002).*

2007, 011081.6 A1

5, 2007 Jun et al.

8844-8850.

2007/0114520 A1

5, 2007 Garditz et al.

Alivisatos, A.P. "Perspectives on the Physical Chemistry of Semi

2007/O125983 A1

6/2007 Treadway et al.

conductor Nanocrystals'. J. Phys. Chem. (1996), 100, pp. 13226

2007/013 1905 A1

6, 2007 Sato et al.

2007/0199.109
2007/0202333
2007/0238126
2008. O107911
2008/O112877
2008/O121844

A1
A1
A1
A1
A1
A1

2008.0160306 A1
2008.O220593
2008/0257.201
2008/0264479
2009/O139574

A1
A1
A1
A1

2009, 0212258 A1

2009,0263816
2010.0059721
2010.0068522
2010.0113813
2010, 0123155

A1
A1
A1
A1
A1

2010.0193767 A1

8, 2007
8, 2007
10, 2007
5, 2008
5, 2008
5/2008

Yi et al.
O'Brien et al.
Pickett et al.
Liu et al.
Xiao et al.
Jang et al.

7/2008 Mushtaq et al.
9, 2008
10, 2008
10, 2008
6, 2009

Pickett et al.
Harris et al.
Harris et al.
Pickett et al.

8, 2009 McCairn et al.

10, 2009
3/2010
3/2010
5, 2010
5, 2010

Pickett et al.
Pickett et al.
Pickett et al.
Pickett et al.
Pickett et al.

8/2010 Naasani et al.

FOREIGN PATENT DOCUMENTS
EP
EP
GB
GB
JP

1783 137 A1
1854,792 A1
9518910.6
2429838 A
2005,139389

5/2007
11, 2007
9, 1995
3, 2007
6, 2005

13239.

Arici et al. Thin Solid Films 451-452 (2004) 612-618.
Battaglia et al., “Colloidal Two-dimensional Systems: CodSe Quan
tum Shells and Wells.” Angew Chem. (2003) 115:5189.
Bawendi, M.G. The Quantum Mechanics of Larger Semiconductor
Clusters ("Quantum Dots'), Annu. Rev. Phys. Chem. (1990), 42:
477-498.

Berry, C.R. “Structure and Optical Absorption of Agl Microcrystals'.
Phys. Rev. (1967) 161: 848-851.
Bunge, S.D. et al. “Growth and morphology of cadmium
chalcogenides: the synthesis of nanorods, tetrapods, and spheres
from CdO and CdCOCCH), J. Mater. Chem. (2003) 13: 1705
1709.

Castro et al., Chem. Mater. (2003) 15:3142-3147.
Castro et al., “Synthesis and Characterization of Colloidal CuInS
Nanoparticles from a Molecular Single-Source Precursors.” J. Phys.
Chem. B (2004) 108: 12429.
Chun et al. Thin Solid Films 480-481 (2005) 46-49.

Contreraset al., “ZnO/ZnS(O,OH)/Cu(In,Ga)Se/Mo Solar Cell with
18:6% Efficiency.” from3d World Conf. on Photovol. Energy Conv.,
Late News Paper, (2003) pp. 570-573.
Cui et al., “Harvest of near infrared light in PbSe nanocrystal-poly
mer hybrid photovoltaic cells.” Appl. Physics Lett. 88 (2006)
183111-183111-3.

Cumberland et al., “Inorganic Clusters as Single-Source Precursors
for Preparation of CdSe, ZnSe, and CdSe/ZnS Nanomaterials”
Chemistry of Materials, 14, pp. 1576-1584. (2002).

US 7,867,557 B2
Page 3
Dance et al., J. Am. Chem. Soc. (1984) 106:6285.
Daniels et al., “New Zinc and Cadmium Chalcogenide Structured
Nanoparticles.” Mat. Res. Soc. Symp. Proc. 789 (2004).
Eychmüller, A. etal. "A quantum dot quantum well: CdS/HgS/CdS'.
Chem. Phys. Lett. 208, pp. 59-62 (1993).
Fendler, J.H. et al. “The Colloid Chemical Approach to
Nanostructured Materials”. Adv. Mater. (1995) 7:607-632.
Gao, M. etal. “Synthesis of PbS Nanoparticles in Polymer Matrices'.
J. Chem. Soc. Commun. (1994) pp. 2779-2780.
Gou et al., J. Am. Chem. Soc. (2006) 128:7222-7229.
Gur et al., “Air stable all-inorganic nanocrystal Solar cells processed
from solution.” Lawrence Berkeley Natl. Lab., Univ. of California,
paper LBNL-58424 (2005).
Gurin, Colloids Surf. A (1998) 142:35-40.
Guzelian, A. etal. "Colloidal chemical synthesis and characterization
of InAs nanocrystal quantum dots”, Appl. Phys. Lett. (1996) 69:
1432-1434.

Guzelian, A. et al., J. Phys. Chem. (1996) 100: 7212.
Hagfeldt, A. et al. “Light-induced Redox Reactions in Nanocrystal
line Systems”, Chem. Rev. (1995) 95: 49-68.
Henglein, A. "Small-Particle Research: Physicochemical Properties
of Extremely Small Colloidal Metal and Semiconductor Particles'.
Chem Rev. (1989) 89: 1861-1873.
Hirpo et al., “Synthesis of Mixed Copper-Indium Chalcogenolates.
Single-Source Precursors for the Photovoltaic Materials CuInO2
(Q=S. Se).” J. Am. Chem. Soc. (1993) 115:1597.
Hu et al., Sol. State Comm. (2002) 121:493-496.
International Search Report for PCT/GB2005/00 1611 mailed Sep. 8,
2005 (5 pages).
Jegier, J.A. et al. “Poly(imidogallane): Synthesis of a Crystalline 2-D
Network Solid and Its Pyrolysis To Form Nanocrystalline Gallium
Nitride in Supercritical Ammonia'. Chem. Mater. (1998) 10: 2041
2043.

Jiang et al., Inorg. Chem. (2000) 39:2964-2965.
Kaelin et al., “CIS and CIGS layers from selenized nanoparticle
precursors.” Thin Solid Films 431-432 (2003) pp. 58-62.
Kapur et al., “Non-Vacuum processing of Culin-Ga, Se Solar cells
on rigid and flexible Substrates using nanoparticle precursor inks.”
Thin Solid Films 431-432 (2003) pp. 53-57.
Kher, S. et al. “A Straightforward, New Method for the Synthesis of
Nanocrystalline GaAs and GaP”, Chem. Mater. (1994) 6: 2056-2062.
Kim et al., J. Mech. Sci. Tech. (2005) 19:2085-2090.
Law et al., “Nanowire dye-sensitized solar cells.” Nature Mater.
(2005) vol. 4 pp. 455-459.
Li et al., Adv. Mat. (1999) 11:1456-1459.
Lieber, C. et al. “Understanding and Manipulating Inorganic Mate
rials with Scanning Probe Microscopes'. Angew. Chem. Int. Ed.
Engl. (1996) 35: 687-704.
Little et al., “Formation of Quantum-dot quantum-well
heteronanostructures with large lattice mismatch: Zn/CdS/ZnS,” 114
J. Chem. Phys. 4 (2001).
Lu et al., Inorg. Chem. (2000) 39:1606-1607.
LOver, T. etal. "Preparation of a novel CodSnanocluster material from
a thiophenolate-capped CdS cluster by chemical removal of SPh
ligands”. J. Mater. Chem. (1997) 7(4): 647-651.
Malik et al., Adv. Mat., (1999) 11:1441-1444.
Matijevic, E., “Monodispersed Colloids: Art and Science”, Langmuir
(1986) 2:12-20.
Matijevic, E. "Production of Mondispersed Colloidal Particles'.
Ann. Rev. Mater. Sci. (1985) 15:483-5 18.
Mekis, I. et al., “One-Pot Synthesis of Highly Luminescent CdSet.
CdS Core-Shell Nanocrystals via Organometallic and "Greener”
Chemical Approaches”, J. Phys. Chem. B. (2003) 107: 7454-7462.
Mews et al., J. Phys. Chem. (1994) 98:934.
Micic et al., “Synthesis and Characterization of InP, GaP, and GainP.
Quantum Dots”, J. Phys. Chem. (1995) pp. 7754–7759.
Milliron et al., “Electroactive Surfactant Designed to Mediate Elec
tron Transfer between CdSe Nanocrystals and Organic Semicondic
tors.” Adv. Materials (2003) 15, No. 1, pp. 58-61.
Murray, C.B. et al., “Synthesis and Characterization of Nearly
Monodisperse CoE (E=S, Se, Te) Semiconductor Nanocrystallites”.
J. Am. Chem. Soc. (1993) 115 (19) pp. 8706-8715.
Nairn et al., Nano Letters (2006) 6:1218-1223.

Nazeeruddin et al., “Conversion of Light to Electricity by cis
X2Bis(2.2"bipyridyl-4,4'-dicarboxylate)ruthenium(II)
Charge
Transfer Sensitizers (X=C1-, Br-, I-, CN-, and SCN-) on
Nanocrystalline TiO, Electrodes,” J. Am. Chem. Soc. (1993)
115:6382-6390.

Nazeeruddin et al., “Engineering of Efficient Panchromatic Sensitiz
ers for Nanocrystalline TiO2-Based Solar Cells,” J. Am. Chem. Soc.
(2001) 123:1613-1624.
O'Brien et al., “The Growth of Indium Selenide Thin Films from a
Novel Asymmetric Dialkydiselenocarbamate.” 3 Chem. Vap. Depos.
4, pp. 227 (1979).
Olshaysky, M.A., et al. “Organometallic Synthesis of GaAs Crystal
lites Exhibiting Quantum Confinement”. J. Am. Chem. Soc. (1990)
1.12: 9438-9439.

Olson et al., J. Phys. Chem. C. (2007) 111:16640-16645.
Patents Act 1977: Search Report under Section 17 for Application
No. GB0409877.8 dated Oct. 7, 2004 (2 pages).
Patent Act 1977 Search Report under Section 17 for Application No.
GB0522027.2 dated Jan. 27, 2006 (1 page).
Patent Act 1977 Search Report under Section 17 for Application No.
GB0606845.6 dated Sep. 14, 2006.
Patent Act 1977 Search Report under Section 17 for Application No.
GBO7190739.

Patent Act 1977 Search Report under Section 17 for Application No.
GBO7190754.

Patent Act 1977 Search Report under Section 17 for Application No.
GB0723539.3 dated Mar. 27, 2008 (1 page).
Peng et al., J. Am. Chem. Soc. (2001) 123: 1389.
Peng et al., “Kinetics of I-VI and III-V Colloidal Semiconductor
Nanocrystal Growth: "Focusing” os Size Distributions”. J. Am.
Chem. Soc., (1998) 129: 5343-5344.
Penget al., “Shape control of CdSe nanocrystals', Nature, (2000) vol.
404, No. 6773, pp. 59-61.
Pradhan, N. et al. “Single-Precursor, One-Pot Versatile Synthesis
under near Ambient Conditions of Tunable. Single and Dual Band
Flourescing Metal Sulfide Nanoparticles'. J. Am. Chem. Soc. (2003)
12.5: 2050-2051.

Qi et al., “Efficient polymer-nanocrystal quantum-dot photodetec
tors.” Appl. Physics Lett. 86 (2005) 093103-093103-3.
Qu, L. et al. “Alternative Routes toward High Quality CdSe
Nanocrystals', Nano Lett. (2001) vol. 1, No. 6, pp. 333-337.
Robel et al., “Quantum Dot Solar Cells. Harvesting Light Energy
with CdSe Nanocrystals Molecularly Linked to Mesoscopic TiO2
Films,” J. Am. Chem. Soc. (2006) 128: 2385-2393.
Salata, O.V. et al. “Uniform GaAs quantum dots in a polymer
matrix”, Appl. Phys. Letters (1994) 65(2): 189-191.
Sercel, P.C. et al. “Nanometer-scale GaAs clusters from

organometallic percursors”, Appl. Phys. Letters (1992) 61: 696-698.
Shulz et al., J. Elect. Mat. (1998) 27:433-437.
Steigerwald, M.L. et al. “Semiconductor Crystallites: A Class of
Large Molecules”. Acc. Chem. Res. (1990) 23: 183-188.
Stroscio, J.A. et al. "Atomic and Molecular Manipulation with the
Scanning Tunneling Microscope'. Science (1991), 254: 1319-1326.
Trinidade et al., “A Single Source Spproach to the Synthesis of CdSe
Nanocrystallites”. Advanced Materials, (1996) vol. 8, No. 2, pp.
161-163.

Vayssieres et al., “Highly Ordered SnO, Nanorod Arrays from Con
trolled Aqueous Growth.” Angew. Chem. Int. Ed. (2004) 43: 3666
3670.

Wang Y. et al. “PbS in polymers, From molecules to bulk solids'. J.
Chem. Phys. (1987) 87: 73.15-7322.
Weller, H. "Colloidal Semiconductor Q-Particles: Chemistry in the
Transition Region Between Solid State and Molecules”. Angew.
Chem. Int. Ed. Engl. (1993) 32: 41-53.
Weller, H. "Quantized Semiconductor Particles: A Novel State of
Mater for Materials Science”, Adv. Mater. (1993) 5: 88-95.
Wells, R.L. etal. “Synthesis of Nanocrystalline Indium Arsenide and
Indium Phosphide from Indium(III) Halides and Tris
(trimethylsilyl)pnicogens. Synthesis, Characterization, and Decom
position Behavior of I-In-P(SiMe),”, Chem. Mater. (1995) 7: 793
800.

Xiao et al., J. Mater. Chem. (2001) 11:1417-1420.
Yang et al., Crystal Growth & Design (2007) 12:2562-2567.

US 7,867,557 B2
Page 4
Yu et al., “Polymer Photovoltaic Cells: Enhanced Efficiencies via a
Network of Internal Donor-Acceptor Heterojunctions,” 270 Science
5243 (1995), pp. 1789-1791.
Zhong et al., Nanotechnology 18 (2007) 025602.
Barron, “Group III Materials: New Phases and Nono-particles with
Applications in Electronics and Optoelectronics.” Office of Naval
Research Final Report (1999).
Dabousi et al., “(CdSe)ZnS Core—Shell Quantum Dots: Synthesis
and Characterization of a Size Series of Highly Luminescent
Nanocrystallites.” Jrl. Phys. Chem...(1997) 101, pp. 9463-9475.
Dehnen et al., “Chalcogen-Bridged Copper Clusters.” Eur, J. Inorg.
Chem. (2002) pp. 279-317.
Eisenmann et al., “New Phosphido-bridged Multinuclear Complexes
of Ag and Zn. Zeitschrift fur anorganische und allgemeine Chemi
(1995). (1 page—abstract).
Huang et al., "Bio-Inspired Fabrication of Antireflection
Nanostructures by Replicating Fly Eyes' Nanotechnology (2008)
vol. 19.

International Search Report for PCT/GB2006/003028 mailed Jan.
22, 2007 (5 pages).
International Search Report for PCT/GB2009/001928 mailed Dec. 8,
2009 (3 pages).
International Search Report for PCT/GB2009/002605 mailed Feb.
22, 2010 (3 pages).
Kim et al. “Engineering InASXP1-X/InP/ZnSe III-V Alloyed Core
Shell Quantum Dots for the Near-Infrared” JACS Articles published
on web Jul. 8, 2005.

Materials Research Society Symposium Proceedings Quantum Dots,
Nanoparticles and Nanowires, 2004, ISSN: 0272-9172.
Miller et al., “From Giant Molecular Clusters and Precursors to

Solid-state Structures.” Current Opinion in Solid State and Materials
Science, 4 (Apr. 1999) pp. 141-153.
Nielsch et al., “Uniform Nickel Deposition into Ordered Alumina
Pores by Pulsed Electrodeposition”. Advanced Materials, 2000 vol.
12, No. 8, pp. 582-586.
Rao et al. (2004) “The Chemistry of Nanomaterials: Synthesis, Prop
erties and Applications' p. 443.

Search Report for GB0813273.0 searched Dec. 8, 2008 (1 page).
Search Report for GB0814458.6 searched Dec. 5, 2008 (1 page).
Search Report for GB0820101.4 searched Mar. 3, 2009 (1 page).
Search Report for GB0821122.9 searched Mar. 19, 2009 (2 pages).
Trinidade et al., “Nanocrystalline Seminconductors: Synthesis, Prop
erties, and Perspectives”. Chemistry of Materials, (2001) vol. 13, No.
11, pp. 3843-3858.
Vittal, “The chemistry of inorganic and organometallic compounds
with adameantane-like structures.” Polyhedron, vol. 15, No. 10, pp.
1585-1642 (1996).
Xie et al. “Synthesis and Characterization of Highly Luminescent
CdSe-Core CdS/ZnO.5CdO.5S/ZnS Multishell Nanocrystals” JACS
Articles published on web Apr. 29, 2005.
Zhong et al., “Composition-Tunable ZnCu-XSe Nanocrytals with
High Luminescence and Stability”, Jrl Amer. Chem. Soc. (2003).
Foneberov et al., (2005) “Photoluminescence of tetrahedral quan
tum-dot quantum wells' Physica E, 26:63-66.
Cao, (2005) “Effect of Layer Thickness on the Luminescence Prop
erties of ZnS/CdS/ZnSquantum dot quantum well'. J. of Colloid and
Interface Science 284:516-520.

Harrison et al. (2000) “Wet Chemical Synthesis on Spectroscopic
Study of CdHgTe Nanocrystals with Strong Near-Infrared Lumines
cence” Mat. Sci and Eng.B69-70:355-360.
Sheng et al. (2006) "In-Situ Encapsulation of Quantum Dots into
Polymer Microsphers”. Langmuir 22(8):3782-3790.
Timoshkin, “Group 13 imido metallanes and their heavier analogs
RMYRIn (M=AI, Ga. In;Y=N. P. As, Sb).” Coordination Chemis
try Reviews (2005).
W. Peter Wuelfing et al: “Supporting Information for Nanometer
Gold Clusters Protected by Surface Bound Monolayers of Thiolated
Poly (ethylene glycol) Polymer Electrolyte” Journal of the American
Chemical Society (XP002529160), (1998).
International Search Report for PCT/GB2009/000510 mailed Jul. 6,
2010 (16 pages).

* cited by examiner

U.S. Patent

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Figure 4

s
250

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350

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550

Wavelength inm

25

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35

AO

45

2 - the ta degree)

(b)

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Figure 5

emission

s
absorption

3OO

4OO

500

Wavelength/nm

6OO

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U.S. Patent

Jan. 11, 2011

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Figure 6

emission

s
absorption

300

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6OO

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Jan. 11, 2011

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Figure 7

1.O

emission

0.8

2.
0.6

absorption
0.4

0.2

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Figure 8

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450

5CO

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Jan. 11, 2011

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absorption

1+

-absorption

O
3OO

350

O)

45)

SOC)

55)

OO

wavelength (nm)

Figure 9A
emission

f

3000

-emission

f
2000 +

|

1000
I
30

30

1)

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50

d

490

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Figure 9B

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Absorption
2.5 T.

2
1.5 +
--Absorption

E 1+
0.5 +

O
3O

350

OO

O

500

550

OO

SO

Wavelength (m)

Figure 10A
emission
SOOOOOO I
OOOOOO +

f

6OOOOOO +

|

5OOOOOO +

|

40000+

f

- - mission

30000+
OOOOOO +
1OOOOOO O
45)

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850

Wavelength (nm)

Figure 10B

750

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Jan. 11, 2011

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Absorption

Absorption

350

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450

5OO

550

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650

Wvel ength (nm)

Figure 11A

mission

50OOOO -45OOOO --

400000 -3500OO
300000
Emission

1500 OO
100000 --

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600

Wive ength (nm)

Figure 11B

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US 7,867,557 B2
1.
NANOPARTICLES

This application is the U.S. national stage application of
International (PCT) Patent Application Serial No. PCT/
GB2006/003028, filed Aug. 14, 2006, which claims the ben
efit of GBApplication No. 0516598.0, filed Aug. 12, 2005.
The entire disclosures of these two applications are hereby
incorporated by reference as if set forth at length herein in
their entirety.
The present invention relates to nanoparticles and methods
for preparing nanoparticles.

10

BACKGROUND

material.
15

There has been substantial interest in the preparation and
characterisation of compound semiconductors comprising of
particles with dimensions in the order of 2-100 nm, often
referred to as quantum dots and nanocrystals mainly because
of their optical, electronic or chemical properties. These inter
ests have occurred mainly due to their size-tunable electronic,
optical and chemical properties and the need for the further
miniaturization of both optical and electronic devices that
now range from commercial applications as diverse as bio
logical labelling, Solar cells, catalysis, biological imaging,
light-emitting diodes amongst many new and emerging appli

sis.

Single core nanoparticles, which consist of a single semi
conductor material along with an outer organic passivating
layer, tend to have relatively low quantum efficiencies due to
electron-hole recombination occurring at defects and dan
gling bonds situated on the nanoparticle Surface which lead to

30

non-radiative electron-hole recombinations.

35

One example is ZnS grown on the surface of CdSe cores. The
shell is generally a material with a wider bandgap then the
40

core material, so that the interface between the two materials
further result in defects and non-radiative electron-hole
45

becomes Smaller, the ratio of the number of surface atoms to

The second factor is that, with semiconductor nanopar
ticles, there is a change in the electronic properties of the
material with size, moreover, the band gap gradually becom
ing larger because of quantum confinement effects as the size
of the particles decreases. This effect is a consequence of the
confinement of an electron in a box giving rise to discrete
energy levels similar to those observed in atoms and mol
ecules, rather than a continuous band as in the corresponding
bulk semiconductor material. For a semiconductor nanopar
ticle, because of the physical parameters, the “electron and
hole', produced by the absorption of electromagnetic radia
tion, a photon, with energy greater then the first excitonic
transition, are closer together than in the corresponding mac
rocrystalline material, so that the Coulombic interaction can
not be neglected. This leads to a narrow bandwidth emission,
which is dependent upon the particle size and composition.
Thus, quantum dots have higher kinetic energy than the cor

core material and with little lattice mismatch to that of the

has as little lattice strain as possible. Excessive Strain can

those in the interior increases. This leads to the surface prop
erties playing an important role in the overall properties of the
material.

One method to eliminate defects and dangling bonds is to
grow a second material, having a wider band-gap and small
lattice mismatch with the core material, epitaxially on the
surface of the core particle, (e.g. another II-VI material) to
produce a “core-shell particle'. Core-shell particles separate
any carriers confined in the core from Surface states that
would otherwise act as non-radiative recombination centres.

form. Two fundamental factors, both related to the size of the

individual nanoparticle, are responsible for these unique
properties.
The first is the large Surface to Volume ratio; as a particle

The capping agent usually takes the form of a Lewis base
compound covalently bound to Surface metal atoms of the
outer most inorganic layer of the particle, but more recently,
So as to incorporate the particle into a composite, an organic
system or biological system can take the form of an organic
polymer forming a sheaf around the particle with chemical
functional groups for further chemical synthesis, or an
organic group bonded directly to the Surface of the particle
with chemical functional groups for further chemical synthe

25

cations.

Although some earlier examples appear in the literature,
recently methods have been developed from reproducible
“bottom up' techniques, whereby particles are prepared
atom-by-atom, i.e. from molecules to clusters to particles
using “wet chemical procedures. Rather from “top down”
techniques involving the milling of Solids to finer and finer
powders.
To-date the most studied and prepared of nano-Semicon
ductor materials have been the chalcogenides II-VI materials
namely ZnS, ZnSe, CdS, CdSe, CdTe; most noticeably CdSe
due to its tunability over the visible region of the spectrum.
Semiconductor nanoparticles are of academic and commer
cial interest due to their differing and unique properties from
those of the same material, but in the macro crystalline bulk

2
responding macrocrystalline material and consequently the
first excitonic transition (band gap) increases in energy with
decreasing particle diameter.
The coordination about the final inorganic Surface atoms in
any core, core-shell or core-multi shell nanoparticles is
incomplete, with highly reactive "dangling bonds' on the
Surface, which can lead to particle agglomeration. This prob
lem is overcome by passivating (capping) the "bare' surface
atoms with protecting organic groups. The capping or passi
Vating of particles not only prevents particle agglomeration
from occurring, it also protects the particle from its Surround
ing chemical environment, along with providing electronic
stabilization (passivation) to the particles in the case of core

50

55

recombination resulting in low quantum efficiencies.
Quantum Dot-Quantum Wells
Another approach which can further enhance the efficien
cies of semiconductor nanoparticles is to prepare a core-multi
shell structure where the “electron-hole' pair are completely
confined to a single shell Such as a quantum dot-quantum well
structure. Here, the core is of a wide bandgap material, fol
lowed by a thin shell of narrower bandgap material, and
capped with a further wide bandgap layer, such as CdS/HgS/
CdS grown using a substitution of Hg for Cd on the surface of
the core nanocrystal to depositjust a few monolayer of HgS.
The resulting structures exhibited clear confinement of pho
toexcited carriers in the Hg.S. Other known Quantum dot
quantum well (QDQW) structures include—ZnS/CdSe/ZnS,
CdS/CdSe/CdS and ZnS/CdS/ZnS.

60

65

Colloidally grown QD-QW nanoparticles are relatively
new. The first and hence most studied systems were of CdS/
HgS/CdS grown by the substitution of cadmium for mercury
on the core surface to deposit one monolayer of HgS. A wet
chemical synthetic method for the preparation of spherical
CdS/HgS/CdS quantum wells was presented with a study of
their unique optical properties. The CdS/HgS/CdS particles
emitted a red band-edge emission originating from the HgS

US 7,867,557 B2
3
layer. Little et al. have grown ZnS/CdS/ZnS QDQWs using a
similar growth technique to that of Eychmüller to show that
these structure can be made despite the large lattice mismatch
(12%) between the two materials, ZnS and CdS. Daniels etal
produced a series of structures that include ZnS/CdSe/ZnS,
ZnS/CdS/CdSe/ZnS, ZnS/CdSe/CdS/ZnS, ZnS/CdS/CdSe/

CdS/ZnS. The aim of this work was to grow strained nanoc
rystalline heterostructures and to correlate their optical prop
erties with modelling that Suggested that there is relocation of
the carriers (hole?electron) from confinement in the ZnS core
to the CdSe shell. CdS/CdSe/CdS QDQW's, have also been
produced by Peng et al. although this structure is promising,
the small CdS band gap may not be sufficient to prevent the

10

materials or non-metallic materials. The invention addresses

escape of electrons to the surface.'''

Although there are now a number of methods for preparing
core-shell quantum dots, where it has been shown and
reported for the reaction solutions containing the quantum
dots, core-shell quantum dots can have quantum yields as
high as 90%. However, it is well known that once one tries to
manipulate the freshly made solutions of core-shell quantum
dots such as isolating the particles as dry powders, upon
re-dissolving the particles quantum yields can be substan
tially lower (sometimes as low as 1-5%).
According to a first aspect of the present invention there is
provided a method for producing a nanoparticle comprised of
a core comprising a core semiconductor material, a first layer
comprising a first semiconductor material provided on said
core and a second layer comprising a second semiconductor
material provided on said first layer, said core semiconductor
material being different to said first semiconductor material
and said first semiconductor material being different to said
second semiconductor material, wherein the method com
prises effecting conversion of a nanoparticle core precursor
composition to the material of the nanoparticle core, depos
iting said first layer on said core and depositing said second
layer on said first layer, said core precursor composition
comprising a first precursor species containing a first ion to be
incorporated into the growing nanoparticle core and a sepa
rate second precursor species containing a second ion to be
incorporated into the growing nanoparticle core, said conver
sion being effected in the presence of a molecular cluster
compound under conditions permitting seeding and growth
of the nanoparticle core.
This aspect of the present invention relates to a method of
producing core/multishell nanoparticles of any desirable
form and allows ready production of a monodisperse popu
lation of Such particles which are consequently of a high
purity. It is envisaged that the invention is suitable for pro
ducing nanoparticles of any particular size, shape or chemical
composition. A nanoparticle may have a size falling within
the range 2-100 nm. A sub-class of nanoparticles of particular
interest is that relating to compound semiconductor particles,
also known as quantum dots or nanocrystals.
The current invention concerns the large scale synthesis of
nanoparticles by the reaction whereby a seeding molecular
cluster is placed in a dispersing medium or solvent (coordi
nating or otherwise) in the presence of other precursors to
initiate particle growth. The invention uses a seeding molecu
lar cluster as a template to initiate particle growth from other
precursors present within the reaction medium. The molecu
lar cluster to be used as the seeding agent can either be
prefabricated or produced in situ prior to acting as a seeding

15

25

a number of problems, which include the difficulty of pro
ducing high efficiency blue emitting dots.
The nanoparticle core, first and second semiconductor
materials may each possess any desirable number of ions of
any desirable element from the periodic table. Each of the
core, first and second semiconductor material is preferably
separately selected from the group consisting of a semicon
ductor material incorporating ions from groups 12 and 15 of
the periodic table, a semiconductor material incorporating
ions from groups 13 and 15 of the periodic table, a semicon
ductor material incorporating ions from groups 12 and 16 of
the periodic table, a semiconductor material incorporating
ions from groups 14 and 16 of the periodic table and a semi
conductor material incorporating ions from groups 11, 13 and
16 of the periodic table.
Thus, while at least one of the core, first and second semi

30

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40

45

50

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conductor materials may incorporate ions from groups 12 and
15 of the periodic table, the material(s) used in these layers
may include ions of one or more further elements, for
example, more than one element from group 12 and/or group
15 of the periodic table and/or ions from at least one different
group of the periodic table. A preferred core/multishell archi
tecture comprises at least one layer incorporating two differ
ent types of group 12 ions (e.g. Cd and Zn, or Cd and Hg) and
group 16 ions (e.g. S. Se or Te).
In the nanoparticle of the present invention where at least
one of the core, first and second semiconductor materials is

selected from the group consisting of a semiconductor mate
rial incorporating ions from groups 12 and 15 of the periodic
table (a II-V semiconductor material), a semiconductor
material incorporating ions from groups 14 and 16 of the
periodic table (a IV-VI semiconductor material) and a semi
conductor material incorporating ions from groups 11, 13 and
16 of the periodic table (a I-III-VI semiconductor material),
any other core, first or second layers in a particular nanopar
ticle may comprise a II-V, IV-VI or I-II-VI material. For
example, where a nanoparticle in accordance with the present
invention has a core comprising a II-V semiconductor mate
rial, the nanoparticle may possess a first layer comprising any
appropriate semiconductor material for example a different
II-V material (i.e. a II-V material in which the II ions are ions
of a different element of group 12 compared to the II ions in
the core material and/or the V ions are ions of a different

element compared to the group 15 ions in the core material),
ora IV-VI or I-III-VI semiconductor material. Furthermore, if
60

agent.

Although manipulation of freshly made solutions of core
shell quantum dots can Substantially lower the particles
quantum yields, by using a core-multishell architecture rather
than known core-shell structures, more stable nanoparticles

4
(to both chemical environment and photo effects) can be
produced. It will be appreciated that while the first aspect of
the present invention defines a method for producing nano
particles having a core, and first and second layers, the
method forming the first aspect of the present invention may
be used to provide nanoparticles comprising any desirable
number of additional layers (e.g. third, fourth and fifth layers
provides on the second, third and fourth layers respectively)
of pure or doped semiconductor materials, materials having a
ternary or quaternary structure, alloyed materials, metallic

the nanoparticle in accordance with the present invention
possess a second layer comprising a I-III-VI semiconductor
material, it may possess a first layer comprising any Suitable
semiconductor material including a different I-III-VI semi
conductor material, or a II-V or IV-VI material. It will be

65

appreciated that when choosing Suitable semiconductor
materials to place next to one another in a particular nanopar
ticle (e.g. when choosing a suitable first layer material for
deposition on a core, or a Suitable second layer material for

US 7,867,557 B2
5
deposition on a first layer) consideration should be given to
matching the crystal phase and lattice constants of the mate
rials as closely as possible.
The method forming the first aspect of the present inven
tion may be used to produce a nanoparticle comprised of a
core comprising a core semiconductor material, a first layer
comprising a first semiconductor material provided on said
core and a second layer comprising a second semiconductor
material provided on said first layer, said core semiconductor
material being different to said first semiconductor material
and said first semiconductor material being different to said

6
nium ions. Preferably the group 16 ions are selected from the
group consisting of Sulfide ions, selenide ions and telluride
ions. The group 11 ions are preferably selected from the group
consisting of copper ions, silver ions and gold ions. In a
preferred embodiment the group 13 ions are selected from the
group consisting of aluminium ions, indium ions and gallium
1O.S.

10

second semiconductor material, wherein

a) at least two of the core, first shell and second shell
materials incorporate ions from groups 12 and 15 of the
periodic table, groups 14 and 16 of the periodic table, or
groups 11, 13 and 16 of the periodic table;
b) the second shell material incorporates ions of at least two
different elements from group 12 of the periodic table
and ions from group 16 of the periodic table:
c) at least one of the core, first and second semiconductor
materials incorporates ions from groups 11, 13 and 16 of
the periodic table and at least one other of the core, first

15

indium to sulfide ions is 1:2. Moreover, the semiconductor

and second semiconductor materials is a semiconductor

material not incorporating ions from groups 11, 13 and
16 of the periodic table.
Preferably in set a) the other of the core, first and second
semiconductor materials incorporates ions from the group
consisting groups 12 and 15 of the periodic table, groups 13
and 15 of the periodic table, groups 12 and 16 of the periodic
table, groups 14 and 16 of the periodic table, and groups 11,
13 and 16 of the periodic table.
It is preferred that in set b) said second semiconductor
material has the formula M.NE, where M and N are the
group 12 ions, E is the group 16 ion, and 0<x<1. It is preferred
that 0.1<x<0.9, more preferably 0.2<x<0.8, and most prefer
ably 0.4<x<0.6. Particularly preferred nanoparticles have the
structure ZnS/CdSe/CdZnS/CdZnS/CdSe/ZnS or
CdZnS/CdSe/CdZnS.
In a preferred embodiment of set c) said at least one other
of the core, first and second semiconductor materials not

incorporating ions from groups 11, 13 and 16 of the periodic
table incorporates ions from the group consisting of groups
12 and 15 of the periodic table, groups 13 and 15 of the
periodic table, groups 12 and 16 of the periodic table, and
groups 14 and 16 of the periodic table.
Preferably the nanoparticle formed using the method
according to the first aspect of the present invention further
comprises a third layer of a third semiconductor material
provided on said second layer. The nanoparticle may option
ally comprise still further layers of semiconductor material,
such as fourth, fifth, and sixth layers.
It is preferred that the third semiconductor material is
selected from the group consisting of a semiconductor mate
rial incorporating ions from groups 12 and 15 of the periodic
table, a semiconductor material incorporating ions from
groups 13 and 15 of the periodic table, a semiconductor
material incorporating ions from groups 12 and 16 of the
periodic table, a semiconductor material incorporating ions
from groups 14 and 16 of the periodic table and a semicon
ductor material incorporating ions from groups 11, 13 and 16
of the periodic table.
Preferably the group 12 ions are selected from the group
consisting of Zinc ions, cadmium ions and mercury ions. The
group 15 ions are preferably selected from the group consist
ing of nitride ions, phosphide ions, arsenide ions, and anti
monide ions. It is preferred that the group 14 ions are selected
from the group consisting of lead ions, tin ions and germa

The core, first and second semiconductor materials may
include ions in an approximate 1:1 ratio (i.e. having a stoichi
ometry of 1:1). For example, the nanoparticle ZnS/CdTe?ZnS
contains a first layer of CdTe in which the ratio of cadmium to
telluride ions is approximately 1:1. The semiconductor mate
rials may possess different stroichiometries, for example the
nanoparticle ZnS/CuInS/ZnS contains a first layer of CulnS
in which the ratio of copper to indium ions is approximately
1:1 but the ratio of copper to sulfide ions is 1:2 and the ratio of

25

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45

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65

materials may possess non-empirical stoichiometries. For
example, the nanoparticle ZnS/CunS/CdZnS incorpo
rates a second layer of CdZnS where 0<x<1. The notation
MNE is used herein to denote a mixture of ions M, N and
E (e.g. M=Cd, N=Zn, E=S) contained in a semiconductor
material. Where the notation MNE is used it is preferred
that 0<x<1, preferably 0.1<x<0.9, more preferably
0.2<x<0.8, and most preferably 0.4<x<0.6.
The temperature of the dispersing medium containing the
growing nanoparticles may be increased at any appropriate
rate depending upon the nature of the nanoparticle core pre
cursor composition and the molecular cluster compound
being used. Preferably the temperature of the dispersing
medium is increased at a rate in the range 0.05°C/min to 1
C/min, more preferably at a rate in the range 0.1°C/minto 19
C./min, and most preferably the temperature of the dispersing
medium containing the growing nanoparticles is increased at
a rate of approximately 0.2°C./min.
Any suitable molar ratio of the molecular cluster com
pound to first and second nanoparticle core precursors may be
used depending upon the structure, size and composition of
the nanoparticles being formed, as well as the nature and
concentration of the other reagents, such as the nanoparticle
core precursor(s), capping agent, size-directing compound
and solvent. It has been found that particularly useful ratios of
the number of moles of cluster compound compared to the
total number of moles of the first and second precursor spe
cies preferably lie in the range 0.0001-0.1 (no. moles of
cluster compound): 1 (total no. moles of first and second
precursor species), more preferably 0.001-0.1:1, yet more
preferably 0.001-0.060:1. Further preferred ratios of the
number of moles of cluster compound compared to the total
number of moles of the first and second precursor species lie
in the range 0.002-0.030:1, and more preferably 0.003-0.020:
1. In particular, it is preferred that the ratio of the number of
moles of cluster compound compared to the total number of
moles of the first and second precursor species lies in the
range 0.0035-0.0045:1.
It is envisaged that any suitable molar ratio of the first
precursor species compared to the second precursor species
may be used. For example, the molar ratio of the first precur
Sor species compared to the second precursor species may lie
in the range 100-1 (first precursor species): 1 (second precur
sor species), more preferably 50-1:1. Further preferred ranges
of the molar ratio of the first precursor species compared to
the second precursor species lie in the range 40-5:1, more
preferably 30-10:1. In certain applications it is preferred that
approximately equal molar amounts of the first and second
precursor species are used in the method of the invention. The
molar ratio of the first precursor species compared to the

US 7,867,557 B2
7
second precursor species preferably lies in the range 0.1-1.2:
1, more preferably, 0.9-1.1:1, and most preferably 1:1. In
other applications, it may be appropriate to use approximately
twice the number of moles of one precursor species compared
to the other precursor species. Thus the molar ratio of the first
precursor species compared to the second precursor species
may lie in the range 0.4–0.6:1, more preferably the molar ratio
of the first precursor species compared to the second precur
sor species is 0.5:1. It is to be understood that the above
precursor molar ratios may be reversed such that they relate to
the molar ratio of the second precursor species compared to
the first precursor species. Accordingly, the molar ratio of the
second precursor species compared to the first precursor spe
cies may lie in the range 100-1 (second precursor species): 1
(first precursor species), more preferably 50-1:1, 40-5:1, or
30-10:1. Furthermore, the molar ratio of the second precursor
species compared to the first precursor species may lie in the
range 0.1-1.2:1, 0.9-1.1:1, 0.4–0.6:1, or may be 0.5:1.
In a preferred embodiment of the first aspect of the present
invention the molecular cluster compound and core precursor
composition are dispersed in a Suitable dispersing medium at
a first temperature and the temperature of the dispersing
medium containing the cluster compound and core precursor
composition is then increased to a second temperature which
is sufficient to initiate seeding and growth of the nanoparticle
cores on the molecular clusters of said compound.
Preferably the first temperature is in the range 50° C. to
100° C., more preferably in the range 70° C. to 80° C., and
most preferably the first temperature is approximately 75° C.
The second temperature may be in the range 120° C. to
280° C. More preferably the second temperature is in the
range 150° C. to 250° C., and most preferably the second
temperature is approximately 200° C.
The temperature of the dispersing medium containing the
cluster compound and core precursor composition may be
increased from the first temperature to the second tempera
ture over a time period of up to 48 hours, more preferably up
to 24 hours, yet more preferably 1 hour to 24 hours, and most
preferably over a time period in the range 1 hour to 8 hours.
In a further preferred embodiment of the first aspect of the
present invention the method comprises
a. dispersing the molecular cluster compound and an initial
portion of the nanoparticle core precursor composition
which is less than the total amount of the nanoparticle
core precursor composition to be used to produce said
nanoparticle cores in a suitable dispersing medium at a
first temperature;
b. increasing the temperature of the dispersing medium
containing the cluster compound and core precursor
composition to a second temperature which is sufficient
to initiate seeding and growth of the nanoparticle cores

8
reaction mixture in the dispersing medium. Preferably the
additional core precursors are added either dropwise as a
Solution or as a Solid.

10

15

COCS.

25

30

35

40

45

50

on the molecular clusters of said molecular cluster com

pound; and
c. adding one or more further portions of the nanoparticle
core precursor composition to the dispersing medium
containing the growing nanoparticle cores,
wherein the temperature of the dispersing medium containing
the growing nanoparticle cores is increased before, during
and/or after the addition of the or each further portion of the
nanoparticle core precursor composition.
In this preferred embodiment less than the total amount of
precursor to be used to produce the nanoparticle cores is
present in the dispersing medium with the cluster compound
prior to the initiation of nanoparticle growth and then as the
reaction proceeds and the temperature is increased, additional
amounts of core precursors are periodically added to the

The temperature of the dispersing medium containing the
growing nanoparticle cores may be increased at any appro
priate rate depending upon the nature of the nanoparticle core
precursor composition and the molecular cluster compound
being used. Preferably the temperature of the dispersing
medium is increased at a rate in the range 0.05°C/min to 1
C./min, more preferably at a rate in the range 0.1° C./minto 1
C./min, and most preferably the temperature of the dispersing
medium containing the growing nanoparticle cores is
increased at a rate of approximately 0.2°C./min.
While the first and second temperatures of the dispersing
medium may take any suitable value, in a preferred embodi
ment of the present invention said first temperature is in the
range 15° C. to 60° C. Said second temperature may be in the
range 90° C. to 150° C.
It is preferred that the or each further portion of the nano
particle core precursor composition is added dropwise to the
dispersing medium containing the growing nanoparticle

55

60

65

The or each further portion of the nanoparticle core pre
cursor composition may be added to the dispersing medium
containing the growing nanoparticle cores at any desirable
rate. It is preferred that the core precursor composition is
added to the dispersing medium at a rate in the range 0.1
ml/min to 20 ml/min per litre of dispersing medium, more
preferably at a rate in the range 1 ml/minto 15 ml/min per litre
of dispersing medium, and most preferably at a rate of around
5 ml/min per litre of dispersing medium.
Preferably said initial portion of the nanoparticle core pre
cursor composition is less than or equal to approximately
90% of the total amount of the nanoparticle core precursor
composition to be used to produce said nanoparticle cores.
Said initial portion of the nanoparticle core precursor com
position may be less than or equal to approximately 10% of
the total amount of the nanoparticle core precursor composi
tion to be used to produce said nanoparticle cores.
In a preferred embodiment where one further portion of the
nanoparticle core precursor composition is added to the dis
persing medium containing the growing nanoparticle cores
said one further portion is less than or equal to approximately
90% of the total amount of the nanoparticle core precursor
composition to be used to produce said nanoparticle cores.
In a further preferred embodiment where more than one
further portion of the nanoparticle core precursor composi
tion is added to the dispersing medium containing the grow
ing nanoparticle cores, each of said further portions is less
than or equal to approximately 45% of the total amount of the
nanoparticle core precursor composition to be used to pro
duce said nanoparticle cores. Each of said further portions
may be less than or equal to approximately 10% of the total
amount of the nanoparticle core precursor composition to be
used to produce said nanoparticle cores.
It is preferred that formation of said molecular cluster
compound is effected in situ in said dispersing medium prior
to dispersing the molecular cluster compound and the initial
portion of the nanoparticle core precursor composition in said
dispersing medium.
In a preferred embodiment of the present invention said
process is subject to the proviso that the nanoparticle core
precursor composition does not contain CdCCH-CO). A
further preferred embodiment provides that said process is
Subject to the proviso that the nanoparticle core precursor
composition does not contain TOPSe. Said process may be
Subject to the proviso that the nanoparticle core precursor

US 7,867,557 B2
9
composition does not contain CdCCHCO) and TOPSe. In a
still further preferred embodiment said process is subject to
the proviso that the temperature of the dispersing medium
containing the growing nanoparticle cores is increased at a
rate which is other than 50° C. over a period of 24 hours.
The conversion of the core precursor to the material of the
nanoparticles can be conducted in any suitable dispersing
medium or solvent. In the method of the present invention it
is important to maintain the integrity of the molecules of the
cluster compound. Consequently, when the cluster compound
and nanoparticle core precursor are introduced in to the dis
persing medium or solvent the temperature of the medium/
Solvent must be sufficiently high to ensure satisfactory disso
lution and mixing of the cluster compound it is not necessary
that the present compounds are fully dissolved but desirable.
It is most preferred that the temperature of the dispersing
medium containing the cluster and precursors should not be
so high as to disrupt the integrity of the cluster compound
molecules. Once the cluster compound and core precursor
composition are sufficiently well dissolved in the solvent the
temperature of the solution thus formed is raised to a tem
perature, or range of temperatures, which is/are sufficiently
high to initiate nanoparticle core growth but not so high as to
damage the integrity of the cluster compound molecules. As
the temperature is increased further quantities of core precur
sor are added to the reaction, preferably in a dropwise manner
or as a solid. The temperature of the solution can then be
maintained at this temperature or within this temperature
range for as long as required to form nanoparticle cores pos
sessing the desired properties.
A wide range of appropriate dispersing media/solvents are
available. The particular dispersing medium used is usually at
least partly dependent upon the nature of the reacting species,
i.e. nanoparticle core precursor and/or cluster compound,
and/or the type of nanoparticles which are to be formed.
Preferred dispersing media include Lewis base type coordi
nating solvents, such as a phosphine (e.g.TOP), a phosphine
oxide (e.g. TOPO) or an amine (e.g. HDA), or non-coordi
nating organic solvents, e.g. alkanes and alkenes (e.g. octa
decene). If a non-coordinating solvent is used then it will
usually be used in the presence of a further coordinating agent
to act as a capping agent for the following reason.
If the nanoparticles being formed are intended to function
as quantum dots it is important that the Surface atoms which
are not fully coordinated “dangling bonds' are capped to

10

15

25

30

35

40

45

minimise non-radiative electron-hole recombinations and

inhibit particle agglomeration which can lower quantum effi
ciencies or form aggregates of nanoparticles. A number of
different coordinating solvents are known which can also act
as capping or passivating agents, e.g. TOP TOPO. HDA or
long chain organic acids such as myristic acid. If a solvent is
chosen which cannotact as a capping agent then any desirable
capping agent can be added to the reaction mixture during
nanoparticle growth. Such capping agents are typically Lewis
bases but a wide range of other agents are available. Such as
oleic acid and organic polymers which form protective
sheaths around the nanoparticles.
The first aspect of the present invention comprises of a
method to produce nanoparticle materials using molecular
clusters, whereby the clusters are defined identical molecular
entities, as compared to ensembles of Small nanoparticles,
which inherently lack the anonymous nature of molecular

50

55

60

semiconductor material and said first semiconductor material

being different to said second semiconductor material,
wherein

clusters. The invention consists of the use of molecular clus

ters as templates to seed the growth of nanoparticle cores,
whereby other molecular sources, i.e. the precursor com
pounds, or “molecular feedstocks' are consumed to facilitate
particle growth. The molecular sources (i.e. core precursor

10
composition) are periodically added to the reaction Solution
So as to keep the concentration of free ions to a minimum but
also maintain a concentration of free ions to inhibit Oswards
ripening from occurring and defocusing of nanoparticle size
range from occurring.
A further preferred embodiment of the first aspect of the
present invention provides that the method comprises:
i. monitoring the average size of the nanoparticle cores
being grown; and
ii. terminating nanoparticle core growth when the average
nanoparticle size reaches a predetermined value.
It is preferred that the average size of the nanoparticle cores
being grown is monitored by UV-visible absorption spectros
copy. The average size of the nanoparticle cores being grown
may be monitored by photoluminescence spectroscopy. Pref
erably nanoparticle core growth is terminated by reducing the
temperature of the dispersing medium from the second tem
perature to a third temperature.
Conveniently the method may comprise forming a precipi
tate of the nanoparticle core material by the addition of a
precipitating reagent, which is preferably selected from the
group consisting of ethanol and acetone.
Preferably conversion of the core precursor composition to
the nanoparticle core is effected in a reaction medium and
said nanoparticle core is isolated from said reaction medium
prior to deposition of the first layer.
It is preferable that deposition of said first layer comprises
effecting conversion of a first semiconductor material precur
Sor composition to said first semiconductor material. The first
semiconductor material precursor composition preferably
comprises third and fourth precursor species containing the
ions to be incorporated into the growing first layer of the
nanoparticle. The third and fourth precursor species may be
separate entities contained in said first semiconductor mate
rial precursor composition, or the third and fourth precursor
species may be combined in a single entity contained in the
first semiconductor material precursor composition.
Preferably deposition of said second layer comprises
effecting conversion of a second semiconductor material pre
cursor composition to said second semiconductor material.
The second semiconductor material precursor composition
preferably comprises fifth and sixth precursor species con
taining the ions to be incorporated into the growing second
layer of the nanoparticle. It is preferred that the fifth and sixth
precursor species are separate entities contained in said sec
ond semiconductor material precursor composition, alterna
tively the fifth and sixth precursor species may be combined
in a single entity contained in said second semiconductor
material precursor composition.
A second aspect of the present invention provides a nano
particle produced according to a method in accordance with
the first aspect of the present invention.
A third aspect of the present invention provides a nanopar
ticle comprised of a core comprising a core semiconductor
material, a first layer comprising a first semiconductor mate
rial provided on said core and a second layer comprising a
second semiconductor material provided on said first layer,
said core semiconductor material being different to said first

65

a) at least two of the core, first shell and second shell
materials incorporate ions from groups 12 and 15 of the
periodic table, groups 14 and 16 of the periodic table, or
groups 11, 13 and 16 of the periodic table;

US 7,867,557 B2
11
12
b) the second shell material incorporates ions of at least two CuInSe/CdZnS ZnS/CuGaSe/ZnS, ZnS/CuGaSe/
different elements from group 12 of the periodic table CdZnS and CdZnS/CuGaSe/CdZnS, where
O<x<1.
and ions from group 16 of the periodic table:
A fourth aspect of the present invention provides a method
c) at least one of the core, first and second semiconductor
materials incorporates ions from groups 11, 13 and 16 of 5 for producing a nanoparticle according to the third aspect of
the periodic table and at least one other of the core, first the present invention, wherein the method comprises effect
ing conversion of a nanoparticle core precursor composition
and second semiconductor materials is a semiconductor
material not incorporating ions from groups 11, 13 and to the material of the nanoparticle core, depositing said first
layer on said core and depositing said second layer on said
16 of the periodic table.
10 first layer.
Preferably in set a) the other of the core, first and second
It will be evident to the skilled person how the method
semiconductor materials incorporates ions from the group
consisting groups 12 and 15 of the periodic table, groups 13 forming the fourth aspect of the present invention may be put
and 15 of the periodic table, groups 12 and 16 of the periodic into effect by routine modification to the experimental details
table, groups 14 and 16 of the periodic table, and groups 11, 15 disclosed herein and involving no undue experimentation for
the preparation of core/multishell nanoparticles in accor
13 and 16 of the periodic table.
It is preferred that in set b) said second semiconductor dance with the third aspect of the present invention.
Preferably said nanoparticle core precursor composition
material has the formula MNE, where M and N are the comprises first and second core precursor species containing
group 12 ions, E is the group 16 ion, and 0<x<1. It is preferred
into the growing nanoparticle
that 0.1<x<0.9, more preferably 0.2<x<0.8, and most prefer the ionsisto be incorporated first and second core precursor
core. It preferred that the
ably 0.4<x<0.6. Particularly preferred nanoparticles have the species are separate entities contained in the core precursor
structure ZnS/CdSe/CdZnS, CdZnS/CdSe/ZnS or composition, and the conversion is effected in the presence of
CdZnS/CdSe/CdZnS.
a molecular cluster compound under conditions permitting
In a preferred embodiment of set c) said at least one other seeding and growth of the nanoparticle core.
of the core, first and second semiconductor materials not 25 The first and
core precursor
com
incorporating ions from groups 11, 13 and 16 of the periodic bined in a singlesecond contained in thespecies may be com
entity
core precursor
table incorporates ions from the group consisting of groups position.
12 and 15 of the periodic table, groups 13 and 15 of the
Preferably conversion of the core precursor composition to
periodic table, groups 12 and 16 of the periodic table, and the nanoparticle core is effected in a reaction medium and
groups 14 and 16 of the periodic table.
30 said nanoparticle core is isolated from said reaction medium
Preferably the nanoparticle further comprises a third layer prior to deposition of the first layer.
of a third semiconductor material provided on said second
In a preferred embodiment of the fourth aspect of the
layer. The nanoparticle may optionally comprise still further present invention deposition of the first layer comprises
layers of semiconductor material. Such as fourth, fifth, and effecting conversion of a first semiconductor material precur
sixth layers.
35 Sor composition to said first semiconductor material.
Regarding the third aspect of the present invention it is
Preferably the first semiconductor material precursor com
preferred that the third semiconductor material is selected position comprises third and fourth precursor species con
from the group consisting of a semiconductor material incor taining the ions to be incorporated into the growing first layer
porating ions from groups 12 and 15 of the periodic table, a of the nanoparticle. The third and fourth precursor species
semiconductor material incorporating ions from groups 13 40 may be separate entities contained in the first semiconductor
and 15 of the periodic table, a semiconductor material incor material precursor composition (i.e. the precursor species
porating ions from groups 12 and 16 of the periodic table, a may be provided by a multisource or dual source precursor
semiconductor material incorporating ions from groups 14 composition). Alternatively or additionally the third and
and 16 of the periodic table and a semiconductor material fourth precursor species may be combined in a single entity
incorporating ions from groups 11, 13 and 16 of the periodic 45 contained in the first semiconductor material precursor com
table.
position (i.e. the precursor composition may contain a single
Preferably the group 12 ions are selected from the group Source precursor comprising both the third and fourth ions to
be incorporated in to the first layer).
consisting of Zinc ions, cadmium ions and mercury ions.
Preferably deposition of the second layer comprises effect
The group 15 ions are preferably selected from the group
consisting of nitride ions, phosphide ions, arsenide ions, and 50 ing conversion of a second semiconductor material precursor
composition to said second semiconductor material.
antimonide ions.
Preferably the second semiconductor material precursor
It is preferred that the group 14 ions are selected from the composition comprises fifth and sixth precursor species con
group consisting of lead ions, tin ions and germanium ions.
ions to be incorporated into the growing second
Preferably the group 16 ions are selected from the group 55 taining the nanoparticle. The fifth and sixth precursor species
layer of the
consisting of Sulfide ions, selenide ions and telluride ions.
separate entities
The group 11 ions are preferably selected from the group may bematerial precursorcontained in said second semicon
ductor
composition, and/or the fifth and
consisting of copper ions, silver ions and gold ions.
sixth precursor species may be combined in a single entity
In a preferred embodiment the group 13 ions are selected contained in said second semiconductor material precursor
from the group consisting of aluminium ions, indium ions and 60 composition.
gallium ions.
The invention addresses a number of problems, which
The current invention describes the design and preparation include the difficulty of producing high efficiency blue emit
methods of a number of unique quantum dot-quantum wells ting dots.
The most researched and hence best-characterized semi
nanoparticles including, ZnS/CuInS/ZnS, ZnS/CuInS/
CdZnS, CdZnS/CuInS/CdZnS, ZnS/CuGaS/ 65 conductor QD is CdSe, whose optical emission can be tuned
across the visible region of the spectrum. Green and red
ZnS, ZnS/CuGaS/CdZnS, CdZnS/CuGaS/CdZn
S., ZnS/CuInSe/ZnS, ZnS/CuInSe/CdZnS, CdZnS/ CdSe/ZnScore-shell nanocrystals are the most widely avail

US 7,867,557 B2
13
able under existing methodologies. CdSe nanoparticles with
blue emission along with narrow spectral widths and high
luminescence quantum yields are difficult to synthesize using
the conventional high temperature rapid injection “nucleation
and growth' method. Using this conventional method to
make blue quantum dots is difficult as the blue quantum dots
are the smallest and are what is initially formed but rapidly
grow (about 3 seconds of reaction time) in to larger does
which have a green emission. There are also further problems
including difficulties in experimental work-up, processes and
overcoating with ZnS. Moreover, only small quantities of
material can be produced in a single batch due to the dilute
reaction Solution necessary to keep the particle size Small.
Alternative blue emitting semiconductor nanocrystals
include ZnTe and CdS, however, growing large (>4.5 nm
diameter) ZnTe needed for blue emissions, with narrow size
distributions has proved difficult.
CdS on the other hand has an appropriate bandgap and has
been shown to emit in the 460-480 nm range with narrow size
distributions and good luminescence efficiency. Bare CdS
cores tend to emit white luminescence, attributed to deep trap
emissions which can be Suppressed by overcoating by a wide
band gap material such as ZnS. These CdS/ZnS structures
have shown recent promise as the active material for blue QD
LEDs and blue QD lasers.
Quantum Dots Incorporating Lower Toxicity Elements
Another drive for designing and producing specific quan
tum dot-quantum well structures in this invention is the cur
rent need for quantum dots free of elements (e.g. cadmium
and mercury) which are deemed by national authorities to be
toxic or potentially toxic but which have similar optical and/
or electronic properties to those of CdSe ZnS core-shell
quantum dots. The current invention includes the design and
synthesis of a number of cadmium free QD-QW structures
based on II-VI/I-III-VI/II-VI, III-VII-VIII-V materials
such as but not restricted to ZnS/CuInS/ZnS, ZnS/CuGaS/

14
This organometallic route has advantages over other syn
thetic methods, including near monodispersity <5% and high
particle cystallinity. As mentioned, many variations of this
method have now appeared in the literature which routinely
give high quality core and core-shell nanoparticles with
monodispersity of <5% and quantum yield >50% (for core
shell particles of as-prepared solutions), with many methods

displaying a high degree of size and shape control."
Recently attention has focused on the use of “greener”

10

precursors which are less exotic and less expensive but not
necessary more environmentally friendly. Some of these new
precursors include the oxides, CdC; carbonates MCO
M-Cd, Zn; acetates M(CHCO) M=Cd, Zn and acetylacet
anates CHCOOCH=C(O)CH M-Cd, Zn; amongst

15

other.

(The use of the term “greener” precursors in semiconduc

tor particle synthesis has generally taken on the meaning of
cheaper, readily available and easier to handle precursor start
ing materials, than the originally used organometallics which
are Volatile and air and moisture sensitive, and does not nec

25

30

35

ZnS, ZnS/CuInSe/ZnS, ZnS/CuGaSe/ZnS.''''''

Current Synthetic Methods
Many synthetic methods for the preparation of semicon
ductor nanoparticles have been reported, early routes applied
conventional colloidal aqueous chemistry, with more recent
methods involving the kinetically controlled precipitation of
nanocrystallites, using organometallic compounds.
Over the past six years the important issues have concerned
the synthesis of high quality semiconductor nanoparticles in
terms of uniform shape, size distribution and quantum effi

40

45

ciencies. This has lead to a number of methods that can

routinely produce semiconductor nanoparticles, with mono
dispersity of <5% with quantum yields >50%. Most of these
methods are based on the original “nucleation and growth
method described by Murray, Norris and Bawendi, using
organometallic precursors. Murray etal originally used orga
nometallic solutions of metal-alkyls (RM) M=Cd, Zn, Te;
R=Me, Et and tri-n-octylphosphine sulfide/selenide (TOPS/
Se) dissolved in tri-n-octylphosphine (TOP). These precursor
Solutions are injected into hot tri-n-octylphosphine oxide
(TOPO) in the temperature range 120-400° C. depending on
the size of the particles required and the material being pro
duced. This produces TOPO coated/capped semiconductor
nanoparticles of II-VI material. The size of the particles is
controlled by the temperature, concentration of precursor
used and length of time at which the synthesis is undertaken,
with larger particles being obtained at higher temperatures,
higher precursor concentrations and prolonged reaction
times.

50

55

60

65

essary mean that “greener precursors' are any more environ
mentally friendly).
Single-source precursors have also proved useful in the
synthesis of semiconductor nanoparticle materials of II-VI.
as well as other compound semiconductor nanoparticles. Bis
(dialkyldithio-/diseleno-carbamato)cadmium(II)/zinc.(II)
compounds, M(ECNR) (M=Zn or Cd, E=S or Se and
R=alkyl), have used a similar one-pot synthetic procedure,
which involved dissolving the precursor in tri-ii-octylphos
phine (TOP) followed by rapid injection into hot tri-n-oc
tylphosphine oxide/tri-n-octylphosphine (TOPO/TOP)
above 200° C. Single-source precursors have also been used
to produce I-III-VI materials i.e. CuInS, using (PPH),Culn
(SEt) dissolved in a mixture of hexanethiol and dioctylpha

late at 200° C. to give hexanethiol coated CuInS.

I-III-VI nanoparticles have also been prepared from
multi-source precursors such as in the case of CunSea pre
pared from CuCl dissolved in triethylene and elemental
indium and selenium. CuInTe was produce by a similar
approach but from using elemental tellurium.
For all the above methods, rapid particle nucleation fol
lowed by slow particle growth is essential for a narrow par
ticle size distribution. All these synthetic methods are based
on the original organometallic “nucleation and growth
method by Murray etal, which involves the rapid injection of
the precursors into a hot solution of a Lewis base coordinating
Solvent (capping agent) which may also contain one of the
precursors. The addition of the cooler solution subsequently
lowers the reaction temperature and assist particle growth but
inhibits further nucleation. The temperature is then main
tained for a period of time, with the size of the resulting
particles depending on reaction time, temperature and ratio of
capping agent to precursor used. The resulting solution is
cooled followed by the addition of an excess of a polar solvent
(methanol or ethanol or sometimes acetone) to produce a
precipitate of the particles that can be isolated by filtration or
centrifugation.
Preparation from single-source molecular clusters,
Cooney and co-workers used the cluster S.Cdo (SPh)
Me-NH) to produce nanoparticles of CdS via the oxidation
of surface-capping SPh ligands by iodine. This route fol
lowed the fragmentation of the majority of clusters into ions
which were consumed by the remaining
Another method whereby it is possible to produce large
Volumes of quantum dots, eliminated the need for a high
temperature nucleation step. Moreover, conversion of the
precursor composition to the nanoparticles is affected in the

US 7,867,557 B2
15
presence of a molecular cluster compound. Each identical
molecule of a cluster compound acts as a seed or nucleation
point upon which nanoparticle growth can be initiated. In this
way, nanoparticle nucleation is not necessary to initiate nano
particle growth because Suitable nucleation sites are already
provided in the system by the molecular clusters. The mol
ecules of the cluster compound act as a template to direct
nanoparticle growth. By providing nucleation sites which are
so much more well defined than the nucleation sites employed
in previous work the nanoparticles formed in this way possess
a significantly more well defined final structure than those
obtained using previous methods. A significant advantage of
this method is that it can be more easily scaled-up for use in

16
nary materials and doped materials. Nanoparticle materials
include but are not restricted to:- ZnS/CdSe/CdS/ZnS, ZnS/

10

industry than conventional methods."

The particular solvent used is usually at least partly depen
dent upon the nature of the reacting species, i.e. nanoparticle
precursor and/or cluster compound, and/or the type of nano
particles which are to be formed. Typical solvents include
Lewis base type coordinating solvents, such as a phosphine
(e.g. TOP), a phosphine oxide (e.g. TOPO) or an amine (e.g.
HDA), hexanethiol, or non-coordinating organic Solvents,
e.g. alkanes and alkenes. If a non-coordinating solvent is used
then it will usually be used in the presence of a further coor
dinating agent to act as a capping agent for the following

15

25

CaSO.

If the nanoparticles are intended to function as quantum
dots an outer capping agent (e.g. an organic layer) must be
attached to stop particle agglomeration from occurring. A
number of different coordinating solvents are known which
can also act as capping or passivating agents, e.g. TOP,
TOPO, alkylthiols or HDA. If a solvent is chosen which
cannot act as a capping agent then any desirable capping
agent can be added to the reaction mixture during nanopar
ticle growth. Such capping agents are typically Lewis bases
but a wide range of other agents are available, such as oleic
acid and organic polymers which form protective sheaths
around the nanoparticles.

30

35

40

Type of System Covered by the Current Invention

ZnS/CuInS/ZnS, ZnS/CuInS/CdS/ZnS, CdS/ZnS/CuInS/
CdS/ZnS, ZnS/CuGaS/ZnS, ZnS/CuGaS/CdS/ZnS, CdS/
ZnS/CuGaS/CdS/ZnS, ZnS/CuInSe/ZnS, ZnS/CuInSe/
CdS/ZnS, CdS/ZnS/CuInSe/CdS/ZnS, ZnS/CuGaSe/ZnS,
ZnS/CuGaSe/CdS/ZnS, CdS/ZnS/CuGaSe/CdS/ZnS.
Comprising a core first element from group 12 of the peri
odic table and a second element from group 15 of the periodic
table, a first layer comprising a first element from group 12 of
the periodic table and a second element from group 15 of the
periodic table and a second layer of semiconductor material
comprising a first element from group 12 of the periodic table
and a second element from group 15 of the periodic table and
also including ternary and quaternary materials and doped
materials. Nanoparticle material includes but is not restricted
tO:—

45

50

55

III-VIII-VIII-V Material

where 0<x<1.

II-VI/II-VIIII-VI Material

Comprising a core of a first element from group 12 of the
periodic table and a second element from group 16 of the
periodic table, a first layer of material comprising a shell of a
first element from group 12 of the periodic table and a second
element from group 16 of the periodic table and a second
layer material comprising a shell of a first element from group
12 of the periodic table and a second element from group 16
of the periodic table and also including ternary and quater

include but are not restricted to:

II-VIII-VII-V Material

DESCRIPTION OF INVENTION

The present invention is directed to the preparation of a
number of semiconductor nanoparticles which may be con
sidered as falling within the class of materials known as
quantum dot-quantum wells and includes materials within the
size range 2-100 nm. The present invention describes the
architecture and the preparation of a number of nanoparticles
materials and includes a number of compound semiconductor
particles otherwise referred to as quantum dots-quantum
well, include material comprising of ZnS/CuInS/ZnS, ZnS/
CuInS/CdZnS, Cd:ZnS/CuInS/CdZnS, ZnS/Cu
GaS/ZnS, ZnS/CuGaS/CdZnS, CdZnS/CuGaS/
CdZnS, ZnS/CuInSe/ZnS, ZnS/CuInSe/CdZnS,
CdZnS/CuInSe/CdZnS, ZnS/CuGaSe/ZnS, ZnS/
CuGaSe/CdZnS and CdZnS/CuGaSe/CdZnS,

CdTe/ZnS, ZnS/CdHgS/ZnS, ZnS/HgSe/ZnS, ZnS/HgTe/
ZnS, ZnSe/CdSe/ZnSe, ZnSe/CdTe/ZnSe, ZnSe/HgS/ZnSe,
ZnS/HgSe/ZnS, ZnSe/HgTe/ZnSe, ZnTe/CdSe/ZnS, ZnTe/
CdTe/ZnS, ZnTe/CdHgS/ZnS, ZnTe/HgSe/ZnS, ZnTe/HgTe/
ZnS, CdS/CdSe/ZnS, CdS/CdTe/ZnS, CdS/CdhgS/ZnS,
CdS/HgSe/ZnS, CdS/HgTe/ZnS, CdSe/CdTe/ZnS, CdSe/
CdFHgS/ZnS, CdSe/HgSe/ZnS, CdSe/HgTe/ZnS, CdTe?
CdSe/ZnS, CdTe?CdElgS/ZnS, CdTe?HgSe/ZnS, CdTe?
HgTe/ZnS, HgS/CdSe/ZnS, HgS/CdTe/ZnS, HgS/CdFIgS/
ZnS, HgS/HgSe/ZnS, HgS/HgTe/ZnS, HgSe/CdSe/ZnS,
HgSe/CdTe/ZnS, HgSe/CdHgS/ZnS, HgSe/HgTe/ZnS.
II-VI/I-III-VI/II-VI Material
Comprising a core of a first element from group 12 of the
periodic table and a second element from group 16 of the
periodic table, a first layer of material comprising of a shell of
a first element from group 11 of the periodic table and a
second element from group 13 of the periodic table a third
element from group 16 of the periodic table and a second
layer material comprising a shell of a first element from group
12 of the periodic table and a second element from group 16
of the periodic table and also including ternary and quater
nary materials and doped materials. Nanoparticle materials

60

65

Comprising a core of a first element from group 13 of the
periodic table and a second element from group 15 of the
periodic table, a first layer comprising of a first element from
group 13 of the periodic table and a second element from
group 15 of the periodic table and a second layer comprising
of a first element from group 13 of the periodic table and a
second element from group 15 of the periodic table and also
including ternary and quaternary materials and doped mate
rials. Nanoparticle materials include but are not restricted
tO:—

US 7,867,557 B2
17
AlP/AlAs/AlP, AlP/A1Sb/AIP, AlP/GaN/AIP, AlP/GaP/AIP
AlP/GaAs/AlP, AlP/GaSb/AIP, AlP/InN/AIP, AlP/InP/AIP
AlP/InAs/AlP, AlP/InSb/AIP. A1AS/AIP/AlAs. AlP/A1Sb/
AlP, AlP/GaN/AIP, AlP/GaP/AIP, AlP/GaAs/AlP, AlP/GaSb/
AlP, AlP/InN/AIP, AlP/InP/AIP, AlP/InAs/AlP, AlP/InSb/
AlP. A1Sb/AIP/A1Sb, AlSb/AlAs/A1Sb, AlSb/GaN/A1Sb,
AlSb/GaP/A1Sb, AlSb/GaAs/A1Sb, AlSb/GaSb/A1Sb, AlSb/
InN/A1Sb, AlSb/InP/A1Sb, AlSb/InAs/A1Sb, AlSb/InSb/
AlSb, GaN/AlP/GaN, GaN/AlAS/GaN, GaN/AlAS/GaN,
GaN/GaP/GaN, GaN/GaAs/GaN, GaN/GaSb/GaN, GaN/
InN/GaN, GaN/InP/GaN, GaN/InAS/GaN, GaN/InSb/GaN,
GaP/AIP/GaP. GaP/AlAS/GaP. GaP/A1Sb/GaP. GaP/GaN/
GaP. GaP/GaAs/GaP. GaP/GaSb/GaP. GaP/InNGaP. GaP/
InP/GaP. GaP/InAS/GaP. GaP/InSb/GaP, GaAs/AlP/GaAs,
GaAs/AlAS/GaAs, GaAs/AlSb/GaAs, GaAs/GaN/GaAs,
GaAs/Gap/GaAs, GaAs/GaSb/GaAs, GaAs/InN/GaAs,
GaAs/InP/GaAs, GaAs/InAS/GaAs, GaAs/InSb/GaAs,
GaSb/AIP/GaSb, GaSb/AlAs/GaSb, GaSb/A1Sb/GaSb,
GaSb/GaN/GaSb, GaSb/GaP/GaSb, GaSb/GaAs/GaSb,
GaSb/InN/GaSb, GaSb/InP/GaSb, GaSb/InAS/GaSb, GaSb/
InSb/GaSb, InN/AIP/InN, InN/AlAS/InN, InN/A1Sb/InN,
InN/GaN/InN, InN/GaP/InN, InN/GaAs/InN, InN/GaSb/
InN, InN/InP/InN, InN/InAs/InN, InN/InSb/InN, InP/AIP/
InP, InP/AlAS/InP, InP/A1Sb/InP, InP/GaN/InP, InP/GaP/InP,
InP/GaAs/InP, InP/GaSb/InP, InP/InN/InP, InP/InAS/InP,
InP/InSb/InP, InAS/AlP/InAs, InAs/AlAS/InAs, InAS/A1Sb/
InAs, InAS/GaN/InAs, InAS/GaP/InAs, InAS/GaAs/InAs,
InAS/GaSb/InAs, InAS/InN/InAs, InAS/InP/InAs, InAS/
InSb/InAs, InSb/AlP/InSb, InSb/AlAS/InSb, InSb/A1Sb/
InSb, InSb/GaN/InSb, InSb/GaP/InSb, InSb/GaAs/InSb,
InSb/GaSb/InSb, InSb/InN/InSb, InSb/InP/InSb, InSb/InAs/

10

example (Zn, Cd1-,L, nanocrystal (where L is a capping

15

example being (Zn, CdS, Sei)L nanocrystal (where L is a
Solvothermal

25

30

35

40

include but are not restricted to:—

PbS/PbSe/PbS, PbS/PbTe/PbS, PbS/Sb,Te/PbS, PbS/SnS/

45

PbS, PbS/SnSe/PbS, PbS/SnTe/PbS, PbSe/PbS/PbSe, PbSe/

PbTe/PbSe, PbSe/Sb,Te/PbSe, PbSe/SnS/PbSe, PbSe/
SnSe/PbSe PbSe/SnTe/PbSe PbTe/PbS/PbTe, PbTe/PbSe/

PbTe, PbTe/Sb, Te/PbTe, PbTe/SnS/PbTe, PbTe/SnSe/PbTe,
PbTe/SnTe/PbTe, Sb,Te/PbS/SbTe, Sb,Te/PbSe/SbTe,
SbTe/PbTe/SbTe, Sb, Te/SnS/SbTe, Sb,Tes/SnSe/
SbTe, Sb, Te/SnTe/SbTe, SnS/PbS/SnS, SnS/PbSe/SnS,
SnS/PbTe/SnS, SnS/Sb-Tel/SnS, SnS/SnSe/SnS, SnS/SnTe?
SnS, SnSe/PbSe/SnSe, SnSe/PbS/SnSe, SnSe/PbTe/SnSe,

SnSe/Sb-Tel/SnSe, SnSe/SnS/SnSe, SnSe/SnTe/SnSe, SnTe?
PbS/SnTe, SnTe/PbSe/SnTe, SnTe/PbTe/SnTe, SnTe/Sb,Te/

50

55

SnTe, SnTe/SnS/SnTe, SnTe/SnSe/SnTe.
DEFINITIONS RELATING TO THE INVENTION
60

Semiconductor Nanoparticle
Semiconductor nanoparticles are also known as nanocrys
tals or quantum dots and generally possess a core Surrounded
by at least one shell of semiconductor material. Nanoparticles
comprising a core and a plurality of shells are known as
core/multi-shell nanoparticles. An important class of core/

agent and 0<x<1).
Quaternary Phase
By the term quaternary phase nanoparticle for the purposes
of specifications and claims, refer to nanoparticles of the
above but having a core or at least one shell comprising a
four-component material. The four components are usually
compositions of elements from the as mentioned groups,
capping agent, 0<x<1 and 0<y<1).

InSb.
IV-VI/IV-VI/IV-VI Material

Comprising a core semiconductor material comprising of a
first element from group 14 of the periodic table and a second
element from group 16 of the periodic table, a first layer
comprising of a first element from group 14 of the periodic
table and a second element from group 16 of the periodic table
and a second layer comprising of a first element from group
14 of the periodic table and a second element from group 16
of the periodic table and also including ternary and quater
nary materials and doped materials. Nanoparticle materials

18
multi-shell nanoparticles are quantum dot-quantum wells
which possess an architecture whereby there is a central core
of one material overlaid by another material which is further
over layered by another material in which adjacent layers
comprise different semiconductor materials.
Ternary Phase
By the term ternary phase nanoparticle for the purposes of
specifications and claims, refer to nanoparticles of the above
but having a core and/or at least one shell layer comprising a
three component material. The three components are usually
compositions of elements from the as mentioned groups, for

65

By the term Solvothermal for the purposes of specifica
tions and claims, refer to heating the reaction Solution so as to
initiate and Sustain particle growth or to initiate a chemical
reaction between precursors to initiate particle growth and
can also take the meaning Solvothermal, thermolysis, ther
molsolvol. Solution-pyrolysis, lyothermal.
Core-Shell and Core/Multi Shell (Quantum Dot-Quantum
Well) Particles
The material used on any shell or Subsequent numbers of
shells grown onto the core particle in most cases will be of a
similar lattice type material to the core material i.e. have close
lattice match to the core material so that it can be epitaxially
grown on to the core, but is not necessarily restricted to
materials of this compatibility. The material used on any shell
or Subsequent numbers of shells grown on to the core present
in most cases will have a wider band-gap then the core mate
rial but is not necessarily restricted to materials of this com
patibility.
Capping Agent
The outer most layer (capping agent) of organic material or
sheath material is to inhibit particles aggregation and to pro
tect the nanoparticle from the Surrounding chemical environ
ment and to provide a means of chemical linkage to other
inorganic, organic or biological material. The capping agent
can be the solvent that the nanoparticle preparation is under
taken in, and consists of a Lewis base compound whereby
there is a lone pair of electrons that are capable of donor type
coordination to the Surface of the nanoparticle and can
include mono- or multi-dentate ligands of the type but not
restricted to:—

phosphines (trioctylphosphine, triphenolphosphine, t-bu
tylphosphine), phosphine oxides (trioctylphosphine oxide),
alkyl-amine (hexadecylamine, octylamine), ary-amines,
pyridines, and thiophenes.
The outer most layer (capping agent) can consist of a
coordinated ligand that processes a functional group that can
be used as a chemical linkage to other inorganic, organic or
biological material Such as but not restricted to:—mercapto
functionalized amines or mercaptocarboxylic acids.
The outer most layer (capping agent) can consist of a
coordinated ligand that processes a functional group that is
polymerisable and can be used to form a polymer around the

US 7,867,557 B2
19
particle, polymerisable ligands such as but not limited to
styrene functionalized amine, phosphine or phosphine oxide
ligand.
Nanoparticle Shape
The shape of the nanoparticle is not restricted to a sphere
and can consist of but not restricted to a rod, sphere, disk,
tetrapod or star. The control of the shape of the nanoparticle is
by the addition of a compound that will preferentially bind to
a specific lattice plane of the growing particle and Subse
quently inhibit or slow particle growth in a specific direction.
Example of compounds that can be added but is not restricted
to include: phosphonic acids (n-tetradecylphosphonic acid,
hexylphosphonic acid, 1-decanesulfonic acid, 12-hydroxy
dodecanoic acid, n-octadecylphosphonic acid).
Description of Preparative Procedure
The current invention should lead to pure, monodispersed,
nanocrystalline particles of the materials as described above,
that are stabilized from particle aggregation and the Surround
ing chemical environment by a capping agent, such as an
organic layer.
Synthetic Method Employed
The synthetic method employed to produce the initial core
and core-shell material can either be by the conventional
method of high temperature rapid injection “nucleation and
growth' as in the fourth aspect of the present invention or
where larger quantities of material is required by a seeding
process using of a molecular cluster with dual precursors in
accordance with the first and fourth aspects of the present
invention.

Further consecutive treatment of the as formed nanopar
ticles (ZnS and CdZnS) to form core-shell and then quan
tum dot-quantum well particles may be undertaken. Core
shell particle preparation is undertaken either before or after
nanoparticle isolation, whereby the nanoparticles are isolated
from the reaction and redissolved in new (clean) capping
agent/solvent, this can result in a better quantum yield.

20
For IV-VI material, a source for IV and a source for VI

10

15

tum Well Structures Core Material Source Multi-Source
Precursor Materials
Metal Ions

For a compound semiconductor nanoparticle comprising a
core semiconductor material of for example, (ZnS)L or
(CdZnS)L (where L is a ligand or capping agent) a source
for element Znand Cdis further added to the reaction and can
25

30

cursor are added to the reaction mixture and can be either in

the form of two separate precursors one containing a group II
element, and the other containing V element or as a single
Source precursor that contains both II and V within a single
molecule to form a core or shell layer of II-V material (where
II=Zn, Cd, Hg V=N, PAs, Sb, Bi).

restricted to:—

Organometallic such as but not restricted to a MR2 where
Cd; R-alky or aryl group (MeZn, EtZn MeCd, EtCd);

35

40

MR.
Coordination compound such as a carbonate or a B-dike
tonate or derivative thereof. Such as acetylacetonate (2,4pentanedionate) ICHCOOCH=C(O—)CH M=Zn, Cd,:
Inorganic salt such as but not restricted to a Oxides ZnO,
CdO, Nitrates Mg(NO), Cd(NO), Zn(NO), M(CO)

M=Zn, Cd,; M(CHCO), M=Zn, Cd,
An element Zn, Cd,
Non-Metal Ions
45

For a compound semiconductor nanoparticle comprising,

for example, (ZnE),L, or (CdZn-E),L, a source of E

50

55

ions, where E is a non-metal, for example, Sulfur or selenium,
is further added to the reaction and can consist of any E-con
taining compound that has the ability to provide the growing
particles with a source of Eions. n and mare numerical values
selected to provide the desired compound. L is a ligand. Such
as a capping agent. The precursor can comprise but is not
restricted to an organometallic compound, an inorganic salt, a
coordination compound or an elemental source.
Examples for an II-VI, semiconductor where the second
elements include but are not restricted to:—

ER (E=S or Se; R=Me, Et, Bu, Bu etc.); HER (E=S or Se:
R=Me, Et, Bu, Bu, Pr, Phetc); thiourea S=C(NH2).
60

For III-V material, a source for III and a source for V

precursor are added to the reaction mixture and can be either
in the form of two separate precursors one containing III, and
the other containing V or as a single-source precursor that
contains both III and V within a single molecules to form a
core or shell layer of III-V material (where III-In, Ga., Al, B,
V=N, PAs, Sb, Bi).

consist of any Zn or Cd-containing compound that has the
ability to provide the growing particles with a source of Znor
Cd ions. The precursor can comprise but is not restricted to an
organometallic compound, an inorganic salt, a coordination
compound or the element.
Examples for II-VI, for the first element include but are not

M-Mg R-alky or aryl group (MgTBu); MR where M-Zn,

For II-VI material, a source for II and a source for VI

precursor are added to the reaction mixture and can be either
in the form of two separate precursors one containing I ele
ment, and the other containing VI element or as a single
source precursor that contains both II and VI within a single
molecule to form a core or shell layer of II-VI material (e.g.
where II=Cd, Zn, VIS, Se).
For I-III-VI material, a source for I (group 11 of the
periodic table), a source for III and a source for VI element
precursor are added to the reaction mixture and can be either
in the form of three separate precursors one containing I
element, one containing III element and the other containing
VI or as a single-source precursor that contains both I and VI
and III and VI within a single molecules to form the I-III-VI
layer (where I-Cu and III-In, Ga and VI-S, Se), or a single
Source precursor which contains all three elements.
For II-V material, a source for II and a source for V pre

precursor are added to the reaction mixture and can be either
in the form of two separate precursors one containing IV
element, and the other containing VI element or as a single
source precursor that contains both IV and VI within a single
molecule to form a core or shell layer of IV-VI material
(where IV=Si, C, Ge, Sn, Pb VI-S, Se, Te).
The process may be repeated with the appropriate element
precursors until the desired quantum dot-quantum well or
core/multi-shell material is formed. The nanoparticles size
and size distribution in an ensemble of particles is dependent
on the growth time, temperature and concentrations of reac
tants in Solution, with higher temperatures generally produc
ing larger nanoparticles.
Precursor Materials Used to Grow the Quantum Dot-Quan

65

An element S or Se. An elemental source can be used

whereby the element is directly added to the reaction or is
coordinated to a O-donor Lewis base compound (two electron
pair donor); Such as elemental Sulfur or selenium coordinat
ing to TOP (tri-octyl-phosphine) to form TOPS and TOPSe
respectively or the use of other Lewis bases such as phos
phines, amines orphosphine oxides but not restricted to. Such
as in the case of using octylamine to coordinate Sulfur.

US 7,867,557 B2
21
Core Material Source Single-Source Precursor Materials
For a compound semiconductor nanoparticle comprising,

22
Inorganic salt such as but not restricted to an Oxide, e.g.
InO, Ga-O, a Nitrate, e.g. In(NO), Ga(NO),
M(CHC), MAl, Ga. In

for example, elements ZnS or CdZnS a source for Zn or

Cd and S can be in the from of a single-source precursor,
whereby the precursor to be used contains both Znor Cd and
S within a single molecule. This precursor can be an organo
metallic compound and inorganic salt or a coordination com

An element Ga, In.

Group VI Source (S or Se)

MR (M=S, Se; R=Me, Et, Bu, Bu etc.); HMR (M=S, Se:
R=Me, Et, Bu, Bu, Pr, Phetc); thiourea S=C(NH); Se=C

pound, (ZnS)L or (CdZnS).L. Where Zn or Cd and S

are the elements required within the nanoparticles and L is the
capping ligands.
Examples for an II-VI semiconductor where M=II and
E=VI element can be but is not restricted to bis(dialkyldithio
carbamato)M(II) complexes compounds of the formula
M(SCNR), M=Zn, Cd. S=S, and R-alkyl or aryl groups;
CdS CdSSiMe, Cd(SCNHNH2)C1, Cd(SOCR)py:

(NH).

10

15

RME'Bus M=Zn, Cd; E=S.; R=Me, Et, Ph; DXLEM

(SR), E=S, M=Zn, Cd; X-MeNH", Li, EtNH R=Me,
Et, Ph; CdS (SPh).L., M.(SPh)"DX M Zn, Cd,

X-Me-N", Li"; Zn(SEt)Eto: MeMe'Pr M=Zn, Cd, E=S:
RCdSR's R=O(CIO), R=PPhs, Pr; CdS (SPh),
(PR). (TBu)GaSel: TBuGaS); RInSela R="Bu, CMe, Et,
Si(Bu), C(SiMe); RInS, R=Bu, CMeEt; RGaS
R="Bu, CMe Et, CEts; SAIR R=C(SMe), CEtMe: (C
(SiMe))GaS, TBuGaSI: RGaSea R="Bu, CMeEt,
CEt, C(SiMe), Cp*, CuSe(PR)s R=EtPh, "Prs. Cys.

25

First Semiconductor Materials

For Use in First Layer
For a compound semiconductor quantum dot-quantum
well nanoparticle comprising a first layer of for example,
I-III-VI or II-VI material, sources for element I, III, VI or II
are added to the reaction and can consist of any I, III, VI or
II-containing compound that has the ability to provide the
growing particles with a source of E ions. The precursor can
consist of but are not restricted to an organometallic com
pound, an inorganic salt, a coordination compound or an
elemental source. Examples include but are not restricted

30

But is not restricted to:—

40

CuX where X=Cl, Br, I; Copper(II) acetate(CHCO)Cu,
Copper(I) acetate CH-COCu, copper(II) acetylacetonate
CHCOCH=C(O)CHCu and other B-diketonate, cop
per(I) butanethioate CH (CH2)SCu, Copper(II) nitrate
Cu(NO), CuO.
Group II Source (e.g. Mg)
Organometallic such as but not restricted to a MR where

45

Cd; R-alky or aryl group (MeZn, EtZn MeCd, EtCd);

50

to the reaction and can consist of any Zn or Cd-containing
compound that has the ability to provide the growing particles
with a source of Zn or Cd ions. The precursor can consist of
but are not restricted to an organometallic compound, an
inorganic salt, a coordination compound or the element.
Examples for II-VI, for the first element include but are not
restricted to:—

Cd; R-alky or aryl group (MeZn, EtZn MeCd, EtCd);
55

60

MR.
Coordination compound such as a carbonate or a B-dike
tonate or derivative thereof. Such as acetylacetonate (2,4pentanedionate) (CHCOOCH=C(O)CHI, M=Zn, Cd,:
Inorganic salt such as but not restricted to a Oxides ZnO,
CdO, Nitrates Mg(NO), Cd(NO), Zn(NO), M(CO)

M=Zn, Cd,; M(CHCO), M=Zn, Cd,

But is not restricted to:—

An element Zn, Cd.

MR. Where M-Ga, In, Al, B: R-alky or aryl group AlR.

GaR, InR (R-Me, Et, Pr).
In.

For Use in Second, Outer or any Other Subsequent Layers
The precursor(s) used to provide the second semiconductor
material may be chosen from the same lists of materials set
out above in respect of the first semiconductor material.
For a quantum dot-quantum well with the second or outer
most layer comprising, for example, (ZnS),L, or (Cd

M-Mg R-alky or aryl group (MgTBu); MR where M-Zn,

An element Zn, Cd,

Coordination compound Such as a B-diketonate or deriva
tive thereof, such as CHCOOCH=C(O)CHI, M=Al, Ga.

Second Semiconductor Materials

Organometallic such as but not restricted to a MR where

CdO, a Nitrate, e.g. Mg(NO), Cd(NO), Zn(NO),
M(CO), M=Zn, Cd; M(CHCO), M=Zn, Cd,
Group III Source (e.g. In and Ga)

X-Me-N", Li"; Zn(SEt)Eto: MeMe'Pr M=Zn, Cd, E=S:
IRCdSR's R=O(CIO), R=PPh, Pr; CdS (SPh),
(PR). (Bu)GaSe; BuGaS); RInSea R=Bu, CMeEt,
Si(TBu), C(SiMe); RInS, R="Bu, CMe, Et: RGaS
R=Bu, CMeEt, CEts; SAIR R=C(SMe), CEtMe: (C
(SiMe))GaS, TBuGaSI: RGaSea R="Bu, CMeEt,

ZnS),L, a source for element Zn and Cd is further added

M-Mg R-alky or aryl group (MgTBu); MR where M-Zn,

MR.
Coordination compound Such as a carbonate or a B-dike
tonate or derivative thereof. Such as acetylacetonate (2,4pentanedionate) (CHCOOCH=C(O)CHI, M=Zn, Cd;
Inorganic salt Such as but not restricted to an Oxide, e.g. ZnO,

RMEBus M=Zn, Cd; E=S.; R-Me, Et, Ph; XEM

(SR), E=S, M=Zn, Cd; X-MeNH", Li, EtNH R=Me,
Et, Ph; CdS (SPh).L., M.(SPh)"X M=Zn, Cd,

CEt, C(SiMe), Cp*, CuSe(PR). R=EtPh, "Prs. Cys.

35

tO:—

Group I Source (e.g. Cu)

An element S, Se. An elemental source can be used

whereby the element is directly added to the reaction or is
coordinated to a O-donor Lewis base compound (two electron
pair donor); Such as elemental Sulfur or selenium coordinat
ing to TOP (tri-octyl-phosphine) to form TOPS and TOPSe
respectively or the use of other Lewis bases such as phos
phines, amines orphosphine oxides but not restricted to. Such
as in the case of using octylamine to coordinate Sulfur.
First Semiconductor Materials—Single-Source Precursors
Examples for an II-VI semiconductor where M=II and
E=VI element can be but is not restricted to bis(dialkyldithio
carbamato)M, (II) complexes compounds of the formula
M(SCNR) M=Zn, Cd,; S=S, and R-alkyl or aryl groups:
CdS CdSSiMe, Cd(SCNHNH),C1, Cd(SOCR), py:

Non-Metal Ions
65

For a compound semiconductor nanoparticle comprising,
for example (ZnS),L, or (Cd:ZnS),L, a source for non
metal ions, E. e.g. Sulfur is further added to the reaction and

US 7,867,557 B2
24
Quantum Well Modifications ZnS/CdSe/CdZnS
Growth of the CdZnS shell is performed at a low tem
perature and added very slowly to prevent thick shell growth
and renucleation of CdSe nanoparticles. The likelihood of
alloying is minimal at this growth temperature. The ZnS/
CdSe core-shell nanocrystals exhibit quantum efficiencies of
about 3%. The growth of the outer CdZnS also shifts the
emission and the first absorption feature by about 2 nm.
Again, similar shifts in the emission/absorption are common

23
can consist of any E-containing compound that has the ability
to provide the growing particles with a source of E ions. The
precursor can consist of but are not restricted to an organo
metallic compound, an inorganic salt, a coordination com
pound or an elemental Source. Examples for an II-VI, semi
conductor where the second elements include but are not
restricted to:—

MR (M=S: R=Me, Et, Bu, Buetc.); HMR (M=S: R=Me, Et,
TBu, Bu, Pr, Phetc); thiourea S=C(NH).

An element S or Se. An elemental source can be used

whereby the element is directly added to the reaction or is
coordinated to a O-donor Lewis base compound (two electron
pair donor); Such as elemental Sulfur or selenium coordinat
ing to TOP (tri-octyl-phosphine) to form TOPS and TOPSe
respectively or the use of other Lewis bases such as phos
phines, amines orphosphine oxides but not restricted to. Such
as in the case of using octylamine to coordinate Sulfur.
Second Semiconductor Materials—Single-Source Precur

10

15

SOS

For a compound semiconductor nanoparticle comprising

of elements ZnS or CdZnS a source for Zn or Cd and S

Source can also be in the from of a single-source precursor,
whereby the precursor to be used contains both Znor Cd and
S within the single molecule. This precursor can be an orga
nometallic compound and inorganic salt or a coordination

25

compound, (ZnS)L or (CdZnS),L, Where Zn or Cd

and S are the elements required within the nanoparticles and
L is the capping ligands.
Examples for an II-VI semiconductor were M=II and E=VI
element can be but is not restricted to bis(dialkyldithio-car
bamato)M, (II) complexes compounds of the formula
M(SCNR), M=Zn, Cd. S=S, and R-alkyl or ary groups;
CdS CdSSiMe, Cd(SCNHNH2)C1, Cd(SOCR)py:

RME'Bus M=Zn, Cd; E=S: R=Me, Et, Ph: XLEM

(SR),

30

35

CdS (SPh).I.L. M.(SPh)"DX), M=Zn, Cd;
RCdSR's R=O(CIO), R=PPhs, Pr: CdS (SPh),

ZnScore particles were dissolved in warm capping agent/
solvent such as HDA-hexanethiol or TOPO-hexanethiol fol

lowed by the addition of a copper source, an indium source
and a sulfur source such as CuI dissolved in an amine. In
dissolved in an amine and sulfur coordinated to TOP to give
TOPS. The growth of the CulnS, shell onto the ZnS cores is
achieved by the addition of the above precursors to the HDA
hexanethiol solution while increasing the temperature
between 150° and 300° C. The Solution was then cooled to

X-Me-N", Li": Zn(SEt)Eto: MeMe'PrM=Zn, Cd; E=S.:

40

DETAILED DISCUSSION

The synthesis of quantum dot-quantum wells is preferably
a three-step process, optionally involving isolation of the
product of a step prior to further modification to provide the
next layer of the nanoparticle structure. By way of example,
for the nanoparticle, ZnS/CdSe/CdZnS, the cores are syn
thesized and isolated from a growth solution and the first shell
is grown onto the cores in a separate reaction and isolated
once again. Finally an outer CdZnS shell layer is grown
onto the core-shell structure to produce the ZnS/CdSe/
CdZnS quantum dot-quantum well.
Synthesis of ZnS Cores
Zinc sulfide (or cadmium/zinc sulphide) particles were
synthesized by a number of methods when a small quantity
was needed by decomposing EtsNHaZnoSa (SPh) clus
ters in HDA at 180° C. and heating to 250° C. or 300° C. to
produce 2 nm or 5.5 nm diameter ZnS particles.
Synthesis of ZnS/CdSe Core Shell Dots
Either a combination of two precursors was used Such as
MeCd and TOPSe or a single-source precursor such as
EtNHCdSe (SPh) was used as precursors for the
formation of the CdSe layer. The precursors decompose onto
the ZnScores enabled the synthesis of multi-gram quantities
of ZnS/CdSe core-shell particles.

Cadmium-Free Quantum Dot-Quantum Wells
There is also a great need for quantum dots that perform
similarly to CdSe- ZnScore-shell quantum or quantum dot
quantum wells that are cadmium free. Nanoparticles inaccor
dance with the present invention may therefore be produced
which include a layer of cadmium-free semiconductor mate
rial in place of a cadmium-containing layer. For example, the
nanoparticles ZnS/CuInS/ZnS and ZnS/CuInSe/ZnS can be
produced in accordance with the method of the present inven
tion and used in place of ZnS/CdS/ZnS and ZnS/CdSe/ZnS.
ZnS/CuInS Core/Shell Structure
This was achieved by using either a combination of pre
cursors each containing just one element required within the
final composite nanoparticle or by the use of single-source
precursors which contain all or more than one element
required within the final composite.
Multi-Source Precursors

E=S, M=Zn, Cd; X=MeNH", Li, EtNH":

(PR).

with CdSe or CdS overcoated with ZnS.

45

50

150° C. before further precursor additions, this being
repeated until the desired emission wavelength was achieved.
The particles-containing solution was then cooled and the
particles isolated using excess methanol.
Single-Source Precursors
Single-source precursors may be used such as (Ph-P)CuIn
(SEt) or a combination of single-source precursors such as
In(SCNEt) and Cu(SCNEt).
ZnS/CuInSea Core/Shell Structure
This was achieved by using either a combination of pre
cursors each containing just one element required within the
final composite nanoparticle or by the use of single-source
precursors which contain all or more than one element
required within the final composite.
Multi-Source Precursors

55

60

ZnScore particles were dissolved in warm capping agent/
solvent such as HDA or TOPO-hexanethiol mix followed by
the addition of a copper source an indium source and a sele
nium source such as CuI dissolved in an amine. In Is dissolved
in an amine and selenium coordinated to TOP to give TOPSe.
The growth of the CuInSea shell onto the ZnS cores is
achieved by the addition of the above precursors to the HDA
hexanethiol solution while increasing the temperature
between 150° and 300° C. The Solution was then cooled to

65

150° C. before further additions, this being repeated until the
desired emission wavelength was achieved. The particles
containing Solution was then cooled and the particles isolated
using excess methanol.

US 7,867,557 B2
25
Single-Source Precursors
Single-source precursors may be used such as (Ph-P)CuIn
(SeEt) or a combination of single-source precursors such as
In(SeCNEt) and Cu(SeCNEt).
ZnS/CuInS/ZnS and ZnS/CuInSe/ZnS Core/Multishell
Nanoparticles
The amount of Zinc and Sulfur precursor used was varied
depending on the thickness of the outer ZnS shell required.
ZnS/CuInS or ZnS/CuInSea particles were added to
degassed HDA at 70° C. and heated to 180-200° C. MeZn
and sulfur solutions were used to grow the outer ZnSlayers by
dropwise addition until the desired ZnS shell thickness was

26
FIGS. 10A and 10B show absorption and PL spectra of
ZnS/InP core/shell nanocrystals respectively in which the
ZnS cores are larger than those shown in FIGS. 9A and 9B;
FIGS. 11A and 11B show PL and absorption spectra of
ZnS/InP/ZnS quantum well nanocrystals; and
FIG. 12 shows a PL spectrum for the growth of ZnSe
quantum dots.
EXAMPLES
10

reached.

By the use of an in situ optical probe, moreover, an Ocean
Optics USB2000 spectrometer, the progressive formation/
growth of the core, core-shell or quantum-well particle can be
followed by the maximum of the photoluminescence emis
sion peak or the maximum of the absorption spectra, when the
required the photoluminescence emission was achieved the
reaction was stopped by cooling the reaction solution.
The present invention is illustrated with reference to the
following figures and non-limiting Example and Reference
Examples, in which:
FIG. 1 is an illustration of a) Core nano-particle comprising
of a ZnS core and HDA as an organic capping agent, b)
core-shell particle comprising of a ZnS core a CdSe shell and
HDA as an organic capping agent, c) quantum dot-quantum
well organic capped particle comprising of a ZnScore a CdSe
shell followed by a CdZnS shell with a HDA capping

15

25

30

agent,

FIG.2 is an illustration of a) Core nano-particle comprising
of a ZnS core and HDA as an organic capping agent, b)
core-shell particle comprising of a ZnS core a CdSe shell and
HDA as an organic capping agent, c) quantum dot-quantum
well organic capped particle comprising of a ZnScore a CdSe
shell followed by a ZnS shell with a HDA capping agent d)
quantum dot-multi quantum well comprising of a ZnScore a
CdSe shell followed by a shell of CdS followed by another
shell of ZnS with a HDA capping agent;
FIG. 3 is a diagram of a) core particle comprising of a ZnS
core and HDA as an organic capping agent, b) core-shell
particle comprising of a ZnS core a CuInS, shell and HDA as
an organic capping agent, c) quantum dot-quantum well
organic capped particle comprising of a ZnS core a CuInS
central layer followed by a ZnS shell with a HDA capping

35

40

for 10 minutes. A further 750 ml of acetonitrile was added and
45

agent,

FIG. 4 illustrates properties of ZnS core quantum dots a)
excitation (to the left) and emission spectra of 5.5 nm ZnS
nanocrystals. (b) Powder X-Ray diffraction pattern of 5.5um.
(c) Transmission electron micrograph (TEM) image of 5.5
nm ZnScore. Inset shows a high-resolution image of a single
ZnS particle:
FIG. 5 shows absorption and photoluminescence spectra
for a core-shell ZnS CdSe quantum dots with an outer cap
ping layer of hexadecylamine (HDA), with the absorption
FIG. 6 shows absorption and PL spectra of ZnS/CdSe/

length adsorption feature occurs at W453 nm and the maxi
mum emission peak is at W472 nm,
FIG. 7 shows absorption and PL spectra of ZnS cores:
FIG. 8 shows absorption and PL spectra of ZnSe cores;
FIGS. 9A and 9B show absorption and PL spectra of ZnS/
InP core/shell nanocrystals respectively;

the solution warmed to 75° C. to give a clear pale yellow
solution which was allowed to cool to 5° C. yielding large
colourless crystals (74.5 g). The crystals were washed in
hexane to give 71.3 g of HNEtaZnS,(SPh).

Preparation of Quantum Dot Cores (ZnS or CdZnS)
50

55

maximum at 440 nm and the emission maximum at 460 nm,

CdZnS quantum well nanocrystals. The longest wave

All syntheses and manipulations were carried out under a
dry oxygen-free argon or nitrogen atmosphere using standard
Schlenk or glove box techniques. All solvents were distilled
from appropriate drying agents prior to use (Na/K-benzophe
none for THF. EtO, toluene, hexanes and pentane). HDA,
octylamine, hexanethiol, dioctylphalate, TOP, Cd(CH
CO), sulfur, selenium powder, CdC), CdCO. In I, CuI (Ad
rich) were procured commercially and used without further
purification.
UV-vis absorption spectra were measured on a Hewios?
Thermospectronic. Photoluminescence (PL) spectra were
measured with a Fluorolog-3 (FL3-22) photospectrometer at
the excitation wavelength 380 nm. Powder X-Ray diffraction
(PXRD) measurements were preformed on a Bruker AXS D8
diffractometer using monochromated Cu-K radiation.
Cluster Preparation
Preparation of IHNEtZn(SPh)
To a stirred methanol (360 ml) solution of benzenethiol
(168 ml, 1.636 mmol) and triethylamine (229 ml, 1.64 mmol)
was added dropwise Zn(NO)6HO (189 g, 0.635 mol) that
had previously been dissolved in methanol (630 ml). The
solution was then allowed to stir while warming until the
precipitate had completely dissolved to leave a clear Solution.
This was then place at 5° C. for 24 h in which time large
colourless crystals of IHNEt,Zn(SPh) had formed (169
g).
Preparation of IHNEtaZnS,(SPh)
To a stirred acetonitrile (100 ml) solution of HNEtZn
(SPh) (168.9 g, 0.1086 mol) was added 3.47 g (0.1084
mmol) of sulfur powder, the resulting slurry was left to stirrer

60

65

Method 1—Preparation of ZnS Nanoparticles from Ets
NHLZnS(SPh)/TOPS/MeZn in HDA by dropwise
addition of MeZnTOP
HDA was placed in a three-neck round bottomed flaskand
dried and degassed by heating to 120° C. under a dynamic
vacuum for >1 hour. The solution was then cooled to 60°C. To

this was added HNEtZnS,(SPh). Initially 4 mmol of
TOPS and 4 mmols of MeZn.TOP were added to the reaction
at room temperature and the temperature increased and
allowed to stirfor 2 hours. The temperature was progressively
increased at a rate of ~1°C./5 min with equimolar amounts of
TOPS and MeZn.TOP being added dropwise as the tempera
ture was steadily increased. The reaction was stopped when
the PL emission maximum had reached the required emis
sion, by cooling to 60°C. followed by addition of 300 ml of
dry ethanol or acetone. This produced was isolated by filtra
tion. The resulting ZnSparticles which were recrystallized by
re-dissolving in toluene followed by filtering through Celite

US 7,867,557 B2
27
followed by re-precipitation from warm ethanol to remove
any excess HDA, selenium or cadmium present.
Method 2 (For Reference Purposes Only)
2 nm cores were prepared in 250g hexadecylamine (HDA)
which was previously degassed at 120° C. for one hour then,
under nitrogen, Et NHaZnS(SPh) (4.75 g, 1.64
mmol) was added and the solution was heated to 250° C. for
30 minutes which resulted in the nucleation and growth of
ZnS nanoparticles. The resulting solution was then cooled to
65° C. and the particles were isolated by the addition of 400
ml dry methanol giving 1.1 g ZnS particles with approxi
mately 20% w/w of ZnS. To grow 5.5 nm ZnS, the above
mentioned procedure was repeated at 300° C. growth tem
perature for 30 minutes giving 0.69 g ZnS particles with
approximately 33% w/w of ZnS.
Synthesis of ZnS/CdSe Composite Quantum Dots

5

10

15

In a typical synthesis, 0.35 g ZnS cores (or approximately

4.9x107 particles) were added to 100 g of degassed HDA at
25

HDA solution, between 150 to 300° C. for two hours. The
solution was cooled to 150° C. before the further addition of

precursor. The ZnS/CdSe particles were then cooled and iso
lated with excess methanol.

30

Method 2

and moisture-free HDA at 70° C., the solution was then
35

TOPSe to the ZnS-HDA solution, between 150 to 300° C. for
two hours. The solution was then cooled to 150° C. before

additional MeZn.TOP and TOPS were added, this was
repeated until the desired emission wavelength was achieved.
Synthesis of ZnS/CdSe/CdZnS
The amount of Zinc, cadmium and Sulfur precursor used
was varied depending on the thickness of the outer CdZnS
shell required. The synthesis of ZnS/CdSe/CdZnS 2.5 ml
MeCd (0.05M), 2.5 ml Me,Zn (0.05M) solutions along with

40

45

5.0 ml 0.05M Sulfur Solution was added to the ZnS/CdSe

cores to produce ZnS/CdSe/CdZnS nanoparticles.
50

Preparation of ZnS/InP/ZnS and ZnSe/InP/ZnSe
Quantum Dot-Quantum Wells
55

overnight to room temperature. Particles of HDA coated ZnS
were isolated by the addition of warm dry methanol (250 ml).
The precipitation of white particles occurred these were iso
lated by centrifugation, washed with acetone and left to dry
under nitrogen. Mass of product=1.7442 g. UV-vis and PL
spectra of the ZnScores are shown in FIG. 7.

220° C. and then allowed to cool to room temperature. This
was followed by isolation; by adding 100 ml of dry warm
ethanol which produced a precipitate of orange/red particles
which were isolated via centrifugation, washed with acetone
and left to dry. Mass of product=2.29 g. UV-vis spectrum of
the ZnS/InP core/shell particles is shown in FIG. 9A. PL
spectrum of the ZnS/InP core/shell particles is shown in FIG.
9B.

Preparation of Core-Shell ZnS/InP
Method (b) (Using Larger Sized ZnS Core Particles)
Dibutyl ester (50 ml) and stearic acid (5.65 g) were dried/
degassed by heating to between 65-100° C. under vacuum for
1 hour. The temperature was then increased to 180° C. and
ZnS particles (0.5 g) along with InMe (1.125 ml) and
(TMS)P (1.125 ml) were added dropwise under N to the
the reaction mixture turned pale yellow. When the reaction
temperature had reached 200° C., further addition of InMes
(2.25 ml) and (TMS)P (2.25 ml) was made which resulted in
the colour changing from pale yellow to clear bright orange.
The temperature was then increased to 220°C., with further
addition of InMe (3.375 ml) and (TMS)P (3.375 ml) result
ing in the reaction Solution turning a dark red solution colour.
The reaction mixture was then left to anneal for 1 hour at

heated to 300° C. for 30 minutes. After 30 minutes, the solu
tion was cooled to 200° C. and the reaction mixture was
annealed for one hour. The reaction mixture was left to cool

Preparation of Core-Shell ZnS/InP
Method (a)
Dibutyl ester (50 ml) and stearic acid (5.65 g) were dried/
degassed by heating to between 65-100° C. under vacuum for
1 hour. The temperature was then increased to 180° C. fol
lowed by the addition of InMe (1.125 ml), (TMS)P (1.125
ml) and ZnSparticles (0.235 g) and left to stirfor 10 mins. The
reaction mixture turned pale yellow after 5 mins of addition.
When the reaction temperature had reached 200° C., further
quantities of InMe (2.25 ml) and (TMS)P (2.25 ml) were
added dropwise which resulted in the colour changing from
pale yellow to clear bright orange, the temperature was Sub
sequently increased to 220°C. This was followed by further
addition of InMe (3.375 ml) and (TMS)P (3.375 ml) result
ing in a dark red solution colour.

reaction solution this was left to stirfor 10 mins, in which time

REFERENCE EXAMPLES

Preparation of Core ZnS
HDA (250 g) was placed in a three neck flaskand degassed
at 120° C. under vacuum for one hour. At 100° C. EtNH
ZnoSa (SPh) (10 g) was added and the solution was then

ZnSe cores are shown in FIG. 8.

The reaction mixture was then left to anneal for 1 hour at

In a typical synthesis, ZnS cores were added to degassed
heated to 150° C. The growth of the CdSe layer onto the ZnS
core is achieved by a successive addition of MeCd.TOP and

to 280°C. After 280°C. the reaction was left to cool. Once the

temperature had decreased to 65° C., the particles were iso
lated by addition of methanol (250 ml) followed by centri
fuged, washed with acetone and left to dry under nitrogen.
Mass of product=1.2443 g. UV-vis and PL spectra of the

Method 1

70° C., the solution was then heated to 150° C. The growth of
the CdSe layer onto the ZnScore is, achieved by a successive
addition of the cluster EtsNHCdSe (SPh) to the ZnS

28
Preparation of Core ZnSe
HDA (150 g) was placed in a three neck flask, dried and
degassed at 120° C. for one hour. After one hour the mixture
was cooled to 60° C. ZnSea (SPh).EtNH (5 g) was
added to the HDA under nitrogen at 90° C. and left to stir for
5 mins before adding TOPSe (3.53 ml).
The reaction mixture changed colour from colorless to pale
yellow. The temperature was increased to 120° C. The tem
perature of the reaction mixture was then increased gradually

60

65

220°C. followed by cooling to room temperature. 100 ml of
dry warm ethanol was then added to gave a precipitate of
orange/red particles, these particles were isolated by centrifu
gation, washed with acetone and left to dry. Mass of prod
uct=3.2844 g. UV-vis spectrum of the ZnS/InP core/shell
particles is shown in FIG. 10A. PL spectrum of the ZnS/InP
core/shell particles is shown in FIG. 10B.
Preparation of Core-Shell ZnSe/InP
Dibutyl ester (50 ml) and stearic acid (5.65 g) were placed
in a three neck flask and dried and degassed for one hour at a

US 7,867,557 B2
29
temperature of 90°C. The temperature was increased to 180°
C. with addition of ZnSe particles (0.5 g), (TMS)P (1.125
ml) and InMe (1.125 ml). The solution was left at 180° C. for
10 mins followed by increasing the temperature to 200°C. At
200° C. a further addition of (TMS)P (2.25 ml) and InMe
(2.25 ml) was made. The temperature was then increased to
220° C. followed by a final addition of (TMS)P (3.375 ml)
and InMe (3.375 ml). The reaction mixture changed colour
from orange/yellow to dark red and was left to anneal for one
hour at 220°C. before cooling to room temperature. 100 ml of
dry warm ethanol was then added to the reaction solution to
give a precipitate of orange/red particles, which were isolated
by centrifugation, washed with acetone and left to dry. Mass
of product=3.33 g
Final Shelling
Preparation of ZnS/InP/ZnS
HDA (150 g) was placed in a 3 neck flask and dried and
degassed for one hour the temperature was then increased to
200° C. In a separate flask core-shell particles of ZnS/InP
(with an orange emission) (2.6343 g) were dissolved in Dibu
tyl ester (5 ml) and placed under vacuum for 20 mins this was
followed by sonication for 5 mins, this was followed by the
addition of (TMS)S (3.75 ml). This solution was then added
to the HDA solution dropwise followed by the addition of
Zn(Et) dissolved TOP (7.50 ml). The reaction mixture was

30
5. Total 20 mmol TOP-Se and Zn(Et) were used to make
ZnSe nanoparticles.
6. The final ZnSe nanoparticle was collected by size selec
tive precipitation with hot butanol (70° C.), centrifuga
tion and then redispersed in octane. Excess HDA was
5
completely removed by repeating those previous steps.
The particles were re-dispersed in toluene, hexane, hep
tane and octane, resulting in clear nanoparticle solution.
The PL peak width of ZnSe product by this method is as
10 narrow as 16 nm with a QY of 10-20%.
Preparation of ZnSe Quantum Dots
Dual Source Precursor Method
15

345 C.

After obtaining the ZnSe quantum dots, the multi-injection
of Zn(Et) and TOP-Se precursors for the growth of larger
ZnSe nanoparticles was analogous to the above Cluster
20 Method for the production of ZnSe quantum dots.
The PL peak width of ZnSe product by this method is as
narrow as 20 nm with a QY of 10-30%.
REFERENCES

25

left at 200°C. for 26 hours. After 26 hours some luminescence

was observed. The temperature was then decreased to room
temperature followed by the addition of chloroform. The
reaction solution was then filtered through Celite. The QD
QW's were then isolated under nitrogen by addition of warm
dry methanol followed by centrifugation. UV-vis spectrum of
the ZnS/InP/ZnS core/shell/shell particles is shown in FIG.
11A. PL spectrum of the ZnS/InP/ZnS core/shell/shell par
ticles is shown in FIG. 11B.

Preparation of ZnSe Quantum Dots
Alternative methods are set out below for preparing ZnSe
quantum dots which can be further modified for use as cores
in the preparation of core/multishell quantum dot-quantum
wells as described above.

30

35

40

45

50

tion and PL emission.

1.1 ml TOP-Se (0.5M) and 1 ml Zn(Et), (0.5M) was slowly
injected into the above reaction solution at 290°C., and
then kept at 290° C. for 30 mins. The obtained PL is 393

55

G. Kanatzidis, J. Am. Chem. Soc. 1993, 115, 1597.

2.2 ml TOP-Se (0.5M) and 2 ml Zn(Et) (0.5M) was added
into the reaction solution at 290° C. and then kept at 290°

Adv. Mater. 1999, 11, No 17, 1441.
60

3. Additional of 2 ml, 2 ml, 3 ml and 3 ml etc of the same

stock solution was dropwise injected into reaction Solu
tion by the same reaction condition.
4. The PL peak will be the red-shift with the multi-injection
of Zn(Et) and TOP-Se precursors and the longer
annealing time. The maximum finial PL peak can reach
to 435 nm (See FIG. 12).

(5) “New Zinc and Cadmium Chalcogenide Structured Nano
particles S. M. Daniels, P. O'Brien, N. L. Pickett, J. M.
Smith, Mat. Res. Soc. Symp. Proc. Vol. 789, 2004.
(6) A. Mews, A. Eychmuller, M. Giersig. D. Schooss, H.
Weller, J. Phys. Chem. 1994, 98,934.
(7) “Colloidal Two-dimensional Systems: CdSe Quantum
Shell and Wells' David Battaglia, Jack J. Li, Yunjun Wang,
Xiaogang Peng, Angew. Chem. 2003, 115,5189.
(8) “Formation of Quantum-dot quantum-well heteronano
structures with large lattice mismatch: Zn/CdS/ZnS’ Regi
nald B. Little, Mostafa A. El-Sayed, Garnett W. Bryant,
Susan Burke, J. Chem. Phys. Vol. 114, No. 4, 2001.
(9) “Synthesis and Characterization of Colloidal CuInS
Nanoparticles from a Molecular Single-Source Precur
sors' S. L. Costro, S. G. Bailey. R P Raffaelle, K. K.
Banger, A. F. Hepp, J. Phys. Chem. B. 2004, 108, 12429.
(10) “Synthesis of Mixed Copper-Indium Chalcogenolates.
Single-Source Precursors for the Photovoltaic Materials
CuInO (Q=S. Se)'W.Hirpo, S. Dhingra, A. C. Sutorik, M.
(11) “A Novel Route for the Preparation of CuSe and CuInSe
Nanoparticles' M. A. Malik, P. O'Brien, N. Revaprasadu,

.

C. for 60 mins. The obtained PL is 403 nm.

(2) Synthesis and characterization of nearly monodisperse
CdE (E-sulfur, selenium, tellurium) semiconductor
nanocrystallites, Murray, C.B.; Norris, D. J.; Bawendi, M.
G. J. Am. Chem. Soc. 1993, 115,8706.
(3) Process for preparing a nano-crystalline material, inter
national filing date 9 Aug. 1996, PCT/GB96/01942.
(4) GB Patent, Preparation of Nanoparticle Materials, PCT/
GB2005/OO1611

was then increased to 250° C. this was left to stir for 2 hours,

the initial PL peak of ZnSe was at 385 nm, Zn(Et), and further
quantities of and TOP-Se precursors were added to the reac
tion solution while the temperature was slowly increased to
290° C. Further quantities of Zn(Et), and TOP-Se were added
while the temperature was kept at 290°C. The growth of ZnSe
was followed by monitoring the evolution of UV-Vis absorp

(1) Perspectives on the Physical Chemistry of Semiconductor
Nanocrystals, Alivisatos, A. P.; J. Phys. Chem. 1996, 100,
13226.

Molecular Cluster Method

EtNHaZnSea (SPh) (2.5 g) and 5 mmol TOP-Se
were added to a stirred solution of HDA (55g) under N, while
at 100° C. using standard airless techniques. The temperature

ZnSe quantum dots were prepared by using the injection of
5 ml Zn(Et) (0.5M) and 5 ml TOP-Se (0.5M) into ODA at

(12) “The Growth of Indium Selenide Thin Films from a
Novel Asymmetric Dialkydiselenocarbamate P. O'Brien,
D. J. Otway, J. R. Walsh, Chem. Vap. Deposition 1979, 3,
No. 4, 227.
The invention claimed is:

65

1. A method for producing a nanoparticle comprised of a
core comprising a core semiconductor material, a first layer
comprising a first semiconductor material provided on said

US 7,867,557 B2
31
core and a second layer comprising a second semiconductor
material provided on said first layer, said core semiconductor
material being different to said first semiconductor material
and said first semiconductor material being different to said
second semiconductor material, the method comprising:
effecting conversion of a nanoparticle core precursor com
position to the material of the nanoparticle core;
depositing said first layer on said core; and
depositing said second layer on said first layer, said core
precursor composition comprising a first precursor spe
cies containing a first ion to be incorporated into the
growing nanoparticle core and a separate second precur
Sor species containing a second ion to be incorporated
into the growing nanoparticle core,
said conversion being effected in the presence of a molecu
lar cluster compound different from the nanoparticle
core precursor composition.

10

15

2. The method of claim 1, wherein a ratio of the number of

moles of cluster compound compared to a total number of
moles of the first and second precursor species lies in the
range 0.0001-0.1:1.
3. The method of claim 1, wherein a molar ratio of the first

precursor species to the second precursor species lies in the
range 100-1:1.

4. The method of claim 1, wherein the molecular cluster

compound and the core precursor composition are dispersed
in a dispersing medium at a first temperature and a tempera
ture of the dispersing medium containing the cluster com
pound and the core precursor composition is then increased to
a second temperature greater than the first temperature.
5. The method of claim 4, wherein the first temperature is
in the range 50° C. to 100° C.
6. The method of claim 4, wherein the second temperature
is in the range 120° C. to 280° C.
7. The method of claim 1, the method comprising:
a. dispersing the molecular cluster compound and an initial
portion of the nanoparticle core precursor composition
which is less than a total amount of the core precursor
composition to be used to produce said nanoparticle
cores in a suitable dispersing medium at a first tempera

25

30

35

15. The method of claim 7, wherein formation of said
molecular cluster compound is effected in situ in said dispers
ing medium prior to dispersing the molecular cluster com
pound and the initial portion of the nanoparticle core precur
Sor composition in said dispersing medium.
16. The method of claim 1, wherein conversion of the core

40

precursor composition to the nanoparticle core is effected in
a reaction medium and said nanoparticle core is isolated from
said reaction medium prior to deposition of the first layer.
17. The method of claim 1, wherein:

ture;

b. increasing a temperature of the dispersing medium con
taining the cluster compound and the core precursor
composition to a second temperature greater than the
first temperature; and
c. thereafter, adding one or more further portions of the
core precursor composition to the dispersing medium
containing the growing nanoparticle cores,
wherein the temperature of the dispersing medium contain
ing the growing nanoparticle cores is further increased
above the second temperature at least one of before,
during, or after the addition of the initial portion or each
further portion of the nanoparticle core precursor com
position.

32
8. The method of claim 7, wherein the temperature of the
dispersing medium containing the growing nanoparticle
cores is increased to the second temperature at a rate in the
range 0.05° C./min to 1°C/min.
9. The method of claim 7, wherein said first temperature is
in the range 15° C. to 60° C.
10. The method of claim 7, wherein said second tempera
ture is in the range 90° C. to 150° C.
11. The method of claim 7, wherein the initial portion or
each further portion of the nanoparticle core precursor com
position is added dropwise to the dispersing medium contain
ing the growing nanoparticle cores.
12. The method of claim 7, wherein said initial portion of
the nanoparticle core precursor composition is less than or
equal to approximately 90% of the total amount of the nano
particle core precursor composition to be used to produce said
nanoparticle cores.
13. The method of claim 7, wherein one further portion of
the nanoparticle core precursor composition is added to the
dispersing medium containing the growing nanoparticle
cores and said one further portion is less than or equal to
approximately 90% of the total amount of the nanoparticle
core precursor composition to be used to produce said nano
particle cores.
14. The method of claim 7, wherein a plurality of further
portions of the nanoparticle core precursor composition is
added to the dispersing medium containing the growing nano
particle cores and each of said further portions is less than or
equal to approximately 45% of the total amount of the nano
particle core precursor composition to be used to produce said
nanoparticle cores.

45

50

a) at least two of the core, first shell and second shell
materials incorporate ions from groups 12 and 15 of the
periodic table, groups 14 and 16 of the periodic table, or
groups 11, 13 and 16 of the periodic table; or
b) the second shell material incorporates ions of at least two
different elements from group 12 of the periodic table
and ions from group 16 of the periodic table; or
c) at least one of the core, first and second semiconductor
materials incorporates ions from groups 11, 13 and 16 of
the periodic table and at least one other of the core, first
and second semiconductor materials is a semiconductor

material not incorporating ions from groups 11, 13 and
16 of the periodic table.
k

k

k

k

k