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 1

US007588828B2

(12) United States Patent
Mushtaq et al.
(54) PREPARATION OF NANOPARTICLE
MATERLALS

(75) Inventors: Imrana Mushtaq, Manchester (GB);
Steven Daniels, Manchester (GB); Nigel
Pickett, East Croyden (GB)
(73) Assignee: Nanoco Technologies Limited,
Manchester (GB)
(*) Notice:

Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.C. 154(b) by 0 days.

(21) Appl. No.: 11/852,748
(22) Filed:

Sep. 10, 2007

(65)

Prior Publication Data

US 2008/O160306 A1

Jul. 3, 2008

Related U.S. Application Data
(63) Continuation-in-part of application No. 1 1/579,050,
filed on Oct. 27, 2006.

(30)
Foreign Application Priority Data
Apr. 30, 2004 (GB) ................................. O4O9877.8
Apr. 27, 2005 (GB) ............... PCT/GB2005/OO1611

(51) Int. Cl.
B32B5/66

(2006.01)

(52) U.S. Cl. ....................... 428/403; 428/404; 428/405:
428/406; 427/212
(58) Field of Classification Search ................. 428/403,
428/404, 405, 406; 427/212
See application file for complete search history.
(56)

References Cited
U.S. PATENT DOCUMENTS
4,609.689 A
6,114,038 A

9, 1986 Schwartz et al.
9, 2000 Castro et al.

6,207,229 B1* 3/2001 Bawendi et al. .
... 427,215
6,322,901 B1 * 1 1/2001 Bawendi et al. ............. 428,548
6,379,635 B2

4/2002 O'Brien et al.

6,660,379 B1* 12/2003 Lakowicz et al. ........... 428/402
2003, OO17264 A1
1/2003 Treadway et al.
2003/0106488 A1
6/2003 Huang et al.
2004/O110347
2007, 0104865
2007/0202333
2007/0238126
2008.O220593
2008/0257.201
2008/0264479

A1
A1
A1
A1
A1
A1
A1

6, 2004
5, 2007
8, 2007
10, 2007
9, 2008
10, 2008
10, 2008

Yamashita
Pickett
O'Brien et al.
Pickett et al.
Pickett et al.
Harris et al.
Harris et al.

FOREIGN PATENT DOCUMENTS
CN
GB
JP
WO
WO
WO
WO

1394599
9518910.6
2005,139389
WO 97.101.75
WO-OOf 17642
WO-O2,04527
WOO2.29.140

2, 2003
9, 1995
6, 2005
3, 1997
3, 2000
1, 2002
4/2002

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

WOO3,099708
WO-2004/066361
WO-2005/021150
WO 2004/033366
WO 2005,106082
WO-2006/017125
WO-2006/116337
WO-2007/049052
WO-2007/060591
WO-2007/065039

US 7,588,828 B2
Sep. 15, 2009
4/2003
8, 2004
3, 2005
11, 2005
11, 2005
2, 2006
11, 2006
5/2007
5/2007
6, 2007

OTHER PUBLICATIONS

Cumberland et al., “Inorganic clusters as sinle Source precursors for
preparation of . . . nanomaterials” Chem. Mater. 14, 1576-1584.*
Agger, J.R. et al., J. Phys. Chem. B (1998) 102, p. 3345.
Aldana, J. et al., J. Am. Chem. Soc. (2001), 123:8844.
Alivisatos, A.P.J. Phys. Chem., (1996), 100, p. 13226.
Alivisatos, A.P.J. Am. Chem. Soc., (1998) 120, p. 5343.
Bawendi, M.G., Annu. Rev. Phys. Chem. (1990), 42:477.
Berry, C.R., Phys. Rev. (1967) 161:848.
Bunge, S.D. et al., J. Mater: Chem. (2003) 13: 1705.
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).
Eychmüller, A. et al., Chem. Phys. Lett. 208, p. 59. (1993).
Fendler, J.H. et al., Adv. Mater. (1995) 7: 607.
Gao, M. et al., J. Chem. Soc. Commun. (1994) 2779.
Guzelian, A. et al., Appl. Phys. Lett. (1996) 69: 1432.
Guzelian, A. et al., J. Phys. Chem. (1996) 100: 7212.
Hagfeldt, A. et al., Chem. Rev. (1995) 95: 49.
Henglein, A., Chem Rev. (1989) 89: 1861.
Jegier, J.A. et al., Chem. Mater. (1998) 10.
Kher, S. et al., Chem. Mater. (1994) 6: 2056.
Lieber, C. et al., Angew: Chem. Int. Ed. Engl. (1996) 35: 687.
LOver, T. et al., J. Mater: Chem. (1997) 7(4): 647.
Matijevic, E., Ann. Rev. Mater: Sci. (1985) 15:483.
Matijevic, E., Langmuir (1986) 2:12.
Mekis, I. et al., J. Phys. Chem. B. (2003) 107: 7454.
Micic et al., “Synthesis and Characterization of InP, GaP, and GalnP
Quantum Dots”, J. Phys. Chem. (1995) pp. 7754–7759.
Murray, C.B. et al., “Synthesis and characterization of nearly
monodisperse CoE (E = Sulfur, selenium, tellurium) semiconductor
nanocrystallites”, J. Am. Chem. Soc. (1993) 115 (19) pp. 8706-8715.
Olshavsky, M.A., et al., J. Am. Chem. Soc. (1990) 112:9438.
Peng et al., “Shape control of CdSe nanocrystals', Nature, (2000)
vol. 404, No. 6773, pp. 59-61.
Pradhan, N. et al., J. Am. Chem. Soc. (2003) 125: 2050.
Qu, L. et al., Nano Lett. (2001) 1: 333.
Salata, O.V. et al., Appl. Phys. Letters (1994) 65: 189.
Sercel, P.C. et al., Appl. Phys. Letters (1992) 61: 696.

(Continued)
Primary Examiner Leszek Kiliman
(74) Attorney, Agent, or Firm Goodwin Procter LLP
(57)

ABSTRACT

Nanoparticles including a molecular cluster compound incor
porating ions from groups 12 and 16 of the periodic table, as
well as a core semiconductor material incorporating ions
from groups 13 and 15 of the periodic table, are fabricated.
The core semiconductor material is provided on the molecu
lar cluster compound.
14 Claims, 4 Drawing Sheets

US 7,588,828 B2
Page 2
OTHER PUBLICATIONS

Steigerwald, M.L. et al., Acc. Chem. Res. (1990) 23: 183.
Stroscio, J.A. et al., Science (1991), 254: 1319.
Trinidade et al., “A single source approach to the synthesis of CdSe
nanocrystallites”. Advanced Materials, vol. 8, No. 2, pp. 161-163.
(1996).
Wang Y. et al., J. Chem. Phys. (1987) 87:7315.
Weller, H., Adv. Mater. (1993) 5:88.
Weller, H., Angew: Chem. Int. Ed. Engl. (1993)32:41.
Wells, R.L. et al., Chem. Mater. (1995) 7:793.
International Search Report for PCT/GB2005/00 1611 mailed Sep. 8,
2005 (5 pages).
Patents Act 1977: Search Report under Section 17 for Application
No. GB0409877.8 dated Oct. 7, 2004 (1 page).
Patent Act 1977 Search Report under Section 17 for Application No.
GB0522027.2 dated Jan. 27, 2006 (1 page).
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.
Castro et al., Chem. Mater. (2003) 15:3142-3147.
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.
Castro et al., “Synthesis and Characterization of Colloidal CuInS
Nanoparticles from a Molecular Single-Source Precursors.” J. Phys.
Chem. B (2004) 108:12429.
Cui et al., “Harvest of near infrared light in PbSe nanocrystal-poly
mer hybrid photovoltaic cells.” Appl. Physics Lett. 88 (2006)
183111-183111-3.

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).
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.
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.
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.
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.
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.
Malik et al., Adv. Mat., (1999) 11:1441-1444.
Mews et al., J. Phys. Chem. (1994) 98:934.
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.
Nairn et al., Nano Letters (2006) 6:1218-1223.
Nazeeruddin et al., “Engineering of Efficient Panchromatic Sensitiz
ers for Nanocrystalline TiO-Based Solar Cells,” J. Am. Chem. Soc.
(2001) 123:1613-1624.
Nazeeruddin et al., “Conversion of Light to Electricity by cis
X2Bis(2.2"bipyridyl-4,4'-dicarboxylate)ruthenium(II)
Charge
Transfer Sensitizers (X= Cl-, Br-, I-, CN-, and SCN-) on
Nanocrystalline TiO, Electrodes,” J. Am. Chem. Soc. (1993)
115:6382-6390.

O'Brien et al., “The Growth of Indium Selenide Thin Films from a

Novel Asymmetric Dialkydiselenocarbamate.” 3 Chem. Vap. Depos.
4, pp. 227 (1979).
Olson et al., J. Phys. Chem. C. (2007) 111:16640-16645.
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.
Qi et al., “Efficient polymer-nanocrystal quantum-dot photodetec
tors.” Appl. Physics Lett. 86 (2005) 093103-093103-3.
Robel et al., “Quantum Dot Solar Cells. Harvesting Light Energy
with CdSe Nanocrystals Molecularly Linked to Mesoscopic TiO,
Films,” J. Am. Chem. Soc. (2006) 128: 2385-2393.
Shulz et al., J. Elect. Mat. (1998) 27:433-437.

Vayssieres et al., "Highly Ordered SnO, Nanorod Arrays from Con

trolled Aqueous Growth.” Angew. Chem. Int. Ed. (2004) 43: 3666
3670.

Xiao et al., J. Mater. Chem. (2001) 11:1417-1420.
Yang et al., Crystal Growth & Design (2007) 12:2562-2567.
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.
Patent Act 1977 Search Report under Section 17 for Application No.
GBO606845.6.

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.
GBO723539.3.

* cited by examiner

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1.

2
Single-core semiconductor nanoparticles, which generally
consist of a single semiconductor material along with an outer
organic passivating layer, tend to have relatively low quantum

PREPARATION OF NANOPARTICLE
MATERALS
RELATED APPLICATIONS

The present application is a continuation-in-part of U.S.
application Ser. No. 1 1/579,050, filedon Oct. 27, 2006, which
is the U.S. national stage application of International (PCT)
Patent Application Serial No. PCT/GB2005/001611, filed
Apr. 27, 2005, which claims the benefit of GB Application
No. 0409877.8, filed Apr. 30, 2004. The entire disclosure of
each of these applications is hereby incorporated by refer

efficiencies due to non-radiative electron-hole recombination

10

CCC.

BACKGROUND

There has been substantial interest in the preparation and
characterization of compound semiconductors in the form of
particles with dimensions in the order of 2-50 nanometers
(nm), often referred to as quantum dots, nanoparticles, or
nanocrystals. Interest has arisen mainly due to the size-related
electronic properties of these materials that can be exploited
in many commercial applications such as optical and elec
tronic devices, biological labeling, Solar cells, catalysis, bio
logical imaging, light-emitting diodes, general space light
ing, and electroluminescent and photoluminescent displays.

15

would otherwise act as non-radiative recombination centers.
Small lattice mismatch between the core and shell materials

25

Two fundamental factors, both related to the size of the

individual semiconductor nanoparticle, are responsible for
their unique properties. The first is the large Surface-to-Vol
ume ratio: as a particle becomes Smaller, the ratio of the

30

number of surface atoms to that in the interior increases. This

leads to the Surface properties playing an important role in the
overall properties of the material. The second factor is the
change in the electronic properties of the material with size,
e.g., the band gap gradually becomes larger because of quan
tum confinement effects as the size of the particle decreases.
This effect is a consequence of increased carrier confinement
giving rise to discrete energy levels similar to those observed
in atoms and molecules, rather than the continuous band of

the corresponding bulk semiconductor material. Thus, for a
semiconductor nanoparticle, because of the physical param
eters, the carriers (i.e., electrons and holes) produced by the
absorption of electromagnetic radiation (i.e., a photon) with
energy greater then the first excitonic transition, are closer
together than in the corresponding bulk (or macrocrystalline)

35

40

45

material. So that the coulombic interaction cannot 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 correspond
ing macrocrystalline material and, consequently, the first
excitonic transition (i.e., the bandgap) increases in energy
with decreasing particle diameter.
Among the most studied semiconductor quantum dot
materials have been the chalcogenide II-VI materials, namely
Zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium sulfide
(CdS), cadmium selenide (CdSe), cadmium telluride (CdTe).
Reproducible quantum dot production methods have been
developed from “bottom-up' techniques, whereby particles
are prepared atom-by-atom, i.e. from molecules to clusters to
particles, using wet chemical procedures. The coordination
about the final inorganic Surface atoms in any nanoparticle
may be incomplete, with highly reactive non-fully coordi
nated atomic “dangling bonds on the Surface of the particle,
which can lead to particle agglomeration. This problem may
be overcome by passivating (e.g., capping) the bare surface
atoms with protective organic groups.

occurring at defects and dangling bonds situated on the nano
particle surface. FIG. 1A schematically depicts an indium
phosphide (InP) single-core nanoparticle 100 with a core 110
including InP and an organic passivation layer 120. The
hydrocarbon chains of passivation layer 120 promote mono
dispersity of a group of nanoparticles in Solution.
One method to eliminate defects and dangling bonds is
growth of a second inorganic material, having a wider band
gap and Small lattice mismatch to that of the core material,
epitaxially on the Surface of the core particle to produce a
“core-shell' nanoparticle. Core-shell nanoparticles separate
any carriers confined in the core from Surface states that

50

55

60

also minimizes non-radiative recombination. One example of
a core-shell nanoparticle is ZnS grown on the surface of CdSe
cores. FIG. 1B schematically depicts a core-shell nanopar
ticle 140 with a core 150 including InP and a shell 160
including ZnS.
Another approach is the formation of a core-multi shell
structure where the electron-hole pair is completely confined
to a single shell layer. In these structures, the core is of a wide
bandgap material, Surrounded by a thin shell of narrower
bandgap material, and capped with a further wide bandgap
layer, such as CdS/HgS/CdS. In such a structure, a few mono
layers of mercury sulfide (HgS) are formed on the surface of
the core CdS nanocrystal and then capped by additional CdS.
The resulting structures exhibit clear confinement of photo
excited carriers in the narrower bandgap HgSlayer. FIG. 1C
schematically depicts a multi-shell nanoparticle 170 with a
core 180 including InP, a shell 190 including ZnSe, and an
outer shell 195 including ZnS. FIG. 2 schematically depicts a
nanoparticle 200 coated with a capping layer 210 having a
head group 220 (bonded to the nanoparticle) and hydrocarbon
chains 230.

The outermost layer of organic material (i.e., the capping
agent) or sheath material helps to inhibit particle aggregation,
and further protects the nanoparticle from the Surrounding
chemical environment. It also may provide a means of chemi
cal linkage to other inorganic, organic, or biological material.
In many cases, the capping agent is the solvent in which the
nanoparticle preparation is undertaken, and consists of a
Lewis base compound or a Lewis base compound diluted in a
inert solvent Such as a hydrocarbon. The capping agent
includes alone pair of electrons that are capable of donor-type
coordination to the Surface of the nanoparticle, and may
include mono- or multi-dentate ligands of the types: phos
phines (trioctylphosphine, triphenolphosphine, t-butylphos
phine), phosphine oxides (trioctylphosphine oxide), alkyl
phosphonic acids, alkyl-amine (hexadecylamine, octy
lamine), aryl-amines, pyridines, long chain fatty acids, and
thiophenes. Other types of materials may also be appropriate
capping agents.
The outermost layer (capping agent) of a quantum dot may
also consist of a coordinated ligand that processes additional
functional groups that can be used as chemical linkage to
other inorganic, organic or biological material. In such a case,
the functional group may point away from the quantum dot
surface and is available to bond/react with other available

65

molecules, such as primary, secondary amines, alcohols, car
boxylic acids, azides, or hydroxyl groups. The outermost
layer (capping agent) of a quantum dot may also consist of a

US 7,588,828 B2
3
coordinated ligand, processing a functional group that is
polymerizable, which may be used to form a polymer around
the particle.
The outermost layer (capping agent) may also consist of
organic units that are directly bonded to the outermost inor
ganic layer, and may also process a functional group, not
bonded to the surface of the particle, that may be used to form
a polymer around the particle.
Important issues related to the synthesis of high-quality
semiconductor nanoparticles are particle uniformity, size dis
tribution, quantum efficiencies, long-term chemical stability,
and long-term photostability. Early routes applied conven
tional colloidal aqueous chemistry, with more recent methods
involving the kinetically controlled precipitation of nanocrys
tallites, using organometallic compounds.

5

10

15

4
In an embodiment, the nanoparticle includes a first layer
including a first semiconductor material provided on the
nanoparticle core. The first semiconductor material may
incorporate ions from group 12 of the periodic table, e.g., Zinc
ions, and/or from group 16, e.g., at least one member of the
group consisting of oxide ions, Sulfide ions, selenide ions, and
telluride ions. A second layer including a second semicon
ductor material may be provided on the first layer.
In a second aspect, the invention features a method for
producing nanoparticles including the steps of providing a
nanoparticle precursor composition including group 13 ions
and group 15 ions, and effecting conversion of the nanopar
ticle precursor into nanoparticles. The conversion is effected
in the presence of a molecular cluster compound incorporat
ing group 12 ions and group 16 ions under conditions permit
ting nanoparticle seeding and growth.

SUMMARY OF THE INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS

In accordance with embodiments of the invention, conver

sion of a precursor composition to nanoparticles is effected in
the presence of a molecular cluster compound. Molecules of
the cluster compound act as a seed or nucleation point upon
which nanoparticle growth may be initiated. In this way, a
high-temperature nucleation step is not required to initiate
nanoparticle growth because Suitable nucleation sites are
already provided in the system by the molecular clusters. The
molecules of the cluster compound act as a template to direct
nanoparticle growth. “Molecular cluster' is a term which is
widely understood in the relevant technical field, but for the
sake of clarity should be understood herein to relate to clus
ters of three or more metal atoms and their associated ligands
of sufficiently well-defined chemical structure such that all
molecules of the cluster compound possess approximately
the same relative molecular formula. (When the molecules
possess the same relative molecular formula, the molecular
clusters are identical to one another in the same way that one
HO molecule is identical to another HO molecule.) The

25

30

and
35

molecular clusters act as nucleation sites and are much better

defined than the nucleation sites employed in other methods.
The use of a molecular cluster compound may provide a
population of nanoparticles that are essentially monodis
perse. A significant advantage of this method is that it can be
more easily scaled-up to production Volumes when compared
to other methods of nanoparticle generation. Methods of pro
ducing Suitable molecular cluster compounds are known
within the art, examples of which can be found at the Cam
bridge Crystallographic Data Centre (www.cccdc.ca.ac.uk).
Accordingly, in a first aspect, the invention features a nano
particle including a molecular cluster compound incorporat
ing ions from groups 12 and 16 of the periodic table, as well
as a core semiconductor material incorporating ions from
groups 13 and 15 of the periodic table provided on the
molecular cluster compound. The molecular cluster com
pound and the core semiconductor material may have com
patible crystal phases, and the molecular cluster compound
may incorporate Zinc ions.
Various embodiments of the invention incorporate one or
more of the following features. The group 16 ions may
include at least one member of the group consisting of oxide
ions, sulfide ions, selenide ions, and telluride ions. The group
13 ions may include at least one member of the group con
sisting of aluminum ions, gallium ions, and indium ions. The
group 15 ions may include at least one member of the group
consisting of nitride ions, arsenide ions, and antimonide ions.
The nanoparticle may exhibit a quantum efficiency ranging
from about 20% to about 60%.

In the drawings, like reference characters generally refer to
the same parts throughout the different views. Also, the draw
ings are not necessarily to scale, emphasis instead generally
being placed upon illustrating the principles of the invention.
In the following description, various embodiments of the
present invention are described with reference to the follow
ing drawings, in which:
FIGS. 1A-1C schematically depict exemplary single-core,
core-shell, and multi-shell nanoparticles;
FIG. 2 schematically depicts a nanoparticle coated with a
capping layer;
FIG. 3 schematically depicts the formation of a nanopar
ticle using a molecular seed, capping agent, and precursors;
FIGS. 4A-4E schematically depict various exemplary
molecular clusters that may be utilized as seeding templates
for nanoparticle formation.
DETAILED DESCRIPTION

40

45

Embodiments of the invention involve the large-scale syn
thesis of III-V quantum dots (nanoparticles) whereby a seed
ing molecular cluster is placed in a solvent (coordinating or
otherwise) in the presence of other precursors to initiate par
ticle growth. Moreover, the seeding molecular cluster is
employed as a template to initiate particle growth from other
precursors present within the reaction solution. The molecu
lar cluster used as a seed can either consist of the same

50

elements as those required in the Subsequent quantum dot or
different elements that are not required in the final quantum
dots but facilitate the seeding process. In accordance with
embodiments of the current invention, the molecular cluster

55

60

to be used as the seeding agent is either prefabricated or
produced in situ prior to acting as a seeding agent. In accor
dance with embodiments of the invention, Some precursors
may not be present at the beginning of the reaction process
along with the molecular cluster; however, as the reaction
proceeds and the temperature is increased, additional
amounts of precursors are periodically added to the reaction
either drop-wise as a solution or as a Solid.

In various embodiments of the invention, the formation of

nanoparticles from the precursor(s) is carried out under con
ditions to ensure that, either there is direct reaction and

65

growth between the precursor composition and the molecular
cluster, or some clusters grow at the expense of others (due to
Ostwald ripening) until reaching a certain size at which there
is direct growth of the nanoparticle from the precursor(s).

US 7,588,828 B2
5
Such conditions ensure that the monodispersity of the cluster
compound is maintained throughout nanoparticle growth,
which in turn ensures that a monodisperse population of
nanoparticles is obtained.
Any suitable molar ratio of the molecular cluster com
pound to, e.g., first and second nanoparticle precursors may
be used, and may depend upon the structure, size and com
position of the nanoparticles being formed. The desired ratio
may also depend upon the nature and concentration of the
other reagents, such as the nanoparticle precursor(s), the cap
ping agent, size-directing compounds, and/or solvents. In
embodiments utilizing first and second precursors, ratios of
the number of moles of the molecular cluster compound to the
total number of moles of the first and second precursor spe
cies may be in the range 0.0001-0.1 (no. moles of cluster
compound): 1 (total no. moles of first and second precursor
species), 0.001-0.1:1, or 0.001-0.060:1. The ratios of the
number of moles of the molecular cluster compound to the
total number of moles of the first and second precursor spe
cies may lie in the range 0.002-0.030:1, or 0.003-0.020:1. In
preferred embodiments, the ratio of the number of moles of
the molecular cluster compound to the total number of moles
of the first and second precursor species may lie in the range

10

15

O.OO35-OOO45:1.

Any Suitable molar ratio of a first precursor species to a
second precursor species may be used. For example, the
molar ratio of the first precursor species to the second precur
Sor species may lie in the range 100-1 (first precursor spe
cies): 1 (second precursor species), or 50-1:1. The molar ratio
of the first precursor species to the second precursor species
may even lie in the range 40-5:1, or 30-10:1. In various
embodiments, approximately equal molar amounts of the first
and second precursor species are used. The molar ratio of the
first precursor species to the second precursor species may lie
in the range 0.1-1.2:1, 0.9-1.1:1, or 1:1. In some embodi
ments, it is appropriate to use approximately twice the num
ber of moles of one precursor species than that of 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, or, in a preferred embodiment, 0.5:1.

25

30

35

40

45

50

be conducted in a suitable solvent. When the cluster com

pound and nanoparticle precursor(s) are introduced into the
solvent, the temperature of the solvent is preferably suffi
ciently high to ensure satisfactory dissolution and mixing of
the cluster compound. Full dissolution is preferable but not
necessary. The temperature is preferably low enough to pre
vent disruption of the integrity of the cluster compound mol
ecules. Exemplary solvent temperatures high enough to pro
mote dissolution of the cluster compound yet low enough to
maintain cluster compound integrity may be within the range
of approximately 25°C. to approximately 100° C. Once the
cluster compound and precursor composition are sufficiently
well dissolved in the solvent, the temperature of the solution
thus formed is raised to a temperature, or to a range of tem
peratures, which is/are sufficiently high to initiate nanopar

amines, or functionalized PEG chains. If a solvent is used

which does not act as a capping agent, then any desirable
capping agent may be added to the reaction mixture during
nanoparticle growth. Such capping agents are typically Lewis
bases, but a wide range of other agents is available. Such as
oleic acid or organic polymers which form protective sheaths
around the nanoparticles.
In accordance with embodiments of the invention, III-V

Various embodiments of the invention concern the conver

sion of a nanoparticle precursor composition to a desired
nanoparticle. Suitable precursors include single-source pre
cursors which comprise the two or more ions to be incorpo
rated into the growing nanoparticle, or multi-source precur
sors in which two or more separate precursors each contain at
least one ion to be included in the growing nanoparticle. The
total amount of precursor composition required to form the
final desired yield of nanoparticles may be added before
nanoparticle growth has begun; alternatively, the precursor(s)
may be added in stages throughout the reaction.
The conversion of the precursor(s) into nanoparticles may

6
ticle growth but not so high as to damage the integrity of the
cluster compound molecules. For example, the growth initia
tion temperature may be within the range of approximately
100° C. to approximately 350° C. As the temperature is
increased, further quantities of the precursor may be added to
the reaction in a drop-wise manner (i.e., in liquid form) or as
a solid. The temperature of the solution may then be main
tained at the formation temperature (or within the formation
temperature range) for as long as required to form nanopar
ticles possessing the desired properties.
A wide range of appropriate solvents is available. The
choice of Solvent used may depend upon the nature of the
reacting species, i.e. the nanoparticle precursor and/or cluster
compound, and/or the type of nanoparticles which are to be
formed. Typical Solvents include Lewis base-type coordinat
ing solvents, such as a phosphine (e.g., tri-n-octylphosphine
(TOP)), a phosphine oxide (e.g., tri-n-octylphosphine oxide
(TOPO)), an amine (e.g., hexadecylamine (HDA)), a thiol
Such as octanethiol, or a non-coordinating organic solvent,
e.g. an alkane or an alkene. If a non-coordinating solvent is
used, it will usually be in the presence of an additional coor
dinating agent to act as a capping agent. The reason is that
capping of nanoparticle Surface atoms which are not fully
coordinated, i.e., have dangling bonds, serves to minimize
non-radiative electron-hole recombination and inhibit par
ticle agglomeration (which can lower quantum efficiencies).
A number of different coordinating solvents may also act as
capping or passivating agents, e.g. TOP TOPO, organo-thi
ols, long-chain organic acids Such as myristic acid, long chain

55

60

65

nanoparticles are produced using molecular clusters, which
may be collections of identical molecules (rather than
ensembles of Small nanoparticles which may lack the anony
mous nature of molecular clusters). Molecular clusters can
either have the same elements as required in the nanoparticles
to be formed, or other elements, as long as they can facilitate
a seeding reaction. For example, III-V molecular clusters are
notoriously difficult to produce, but many types of II-VI
molecular clusters may be produced relatively easily. More
over, it is possible to use a II-VI molecular cluster, such as
HNEtaZnS,(SPh), to seed the growth of III-V mate
rials, such as InP and gallium phosphide (GaP) and their
alloys, in nanoparticle form. Other molecular compounds,
herein referred to as "molecular feedstocks.” may be added
and consumed to facilitate particle growth. These molecular
Sources may be periodically added to the reaction solution to
keep the concentration of free ions to a minimum but also
maintain a concentration of free ions to inhibit Ostwald rip
ening and defocusing of nanoparticle size range.
Nanoparticle growth may be initiated by heating (ther
molysis), or by Solvothermal methods. (AS used herein, Sol
Vothermal refers to heating in a reaction solution so as to
initiate and Sustain particle growth, and may also be referred
to as thermolsolvol. Solution-pyrolysis, or lyothermal meth
ods.) Particle preparation may also include changing of the
reaction conditions such as adding a base or an acid (i.e.,
changing the pH of the mixture), pressure change (e.g., using
pressures much greater than atmospheric pressure), or utiliz
ing microwave or other electromagnetic radiation.

US 7,588,828 B2
7
The progress of nanoparticle growth can be monitored in
any convenient way, such as photoluminescence (PL) or UV
visible (UV-vis) spectroscopy. Once nanoparticles have been
produced having the desired properties, e.g., when a nano
particle peak is observed on the PL/UV-vis emission spectra
at the desired wavelength, further growth may be inhibited by
altering the reaction conditions, e.g. reducing the temperature
of the Solution below that necessary to Support nanoparticle
growth. At this stage, the nanoparticles can be isolated from
the growth solution by any convenient means, such as pre
cipitation, or allowed to anneal at a Suitable temperature for
any desirable amount of time, e.g., 10 minutes to 72 hours, to
“size-focus’ via Ostwald ripening prior to isolation. Follow
ing initial isolation, the nanoparticle material may then be
Subject to one or more rounds of Washing to provide final
nanoparticles of high purity.
Referring to FIG. 3, a method 300 for nanoparticle forma
tion is depicted. To molecular seed 310, e.g., ZnS,
(SPh)|XI (where X=Li+ or (CH)NH") are added pre
cursors 320 and 330. In an exemplary embodiment, precursor
320 is an indium source, and may include indium acetate
and/or indium myristate, and precursor 330 is a phosphorous
Source, and may include tris-trimethylsilyl phosphine
(P(TMS)). Capping agent 340, e.g., di-n-butylsebacate, is
also present in the reaction mixture. The indium and phos
phorous atoms from precursors 320 and 330 bond to molecu
lar seed 310, resulting the formation of nanoparticle 350
including an InP core.
Conditions for the Preparation of Semiconductor Nanopar
ticles

Feedstocks: Suitable molecular feedstocks may be in the
form of a single-source precursor or a multi-source precursor.
These feedstocks may be added at the beginning of the reac
tion or periodically throughout the reaction of particle
growth. The feedstock may be in the form of liquids, solu
tions, Solids, slurries and/or gases.
In-situ formation of seeding cluster: The cluster to be
employed as the seeding template may be prefabricated prior
to the reaction and added to the reaction solution at the begin
ning of the reaction process or formed in situ in the reaction
solution prior to the addition of precursors used for the growth
of the nanoparticles.
Embodiments of the invention may be utilized to prepare
semiconductor nanoparticle materials, preferably within the
size range 2-100 nm. The core material of the nanoparticle
may include:
III-V (i.e., 13-15) material including a first element from
group 13 of the periodic table and a second element from
group 15 of the periodic table, including but not limited to
boron phosphide (BP), aluminum phosphide (AlP), alumi
num arsenide (AIAS), aluminum antimonide (AlSb), gallium
nitride (GaN), GaP. gallium arsenide (GaAs), gallium anti
monide (GaSb), indium nitride (InN), InP, indium arsenide
(InAs), indium antimonide (InSb), aluminum nitride (AIN),
boron nitride (BN), and/or ternary or quaternary alloys of
these materials. The material may be doped with at least one
Suitable dopant. As utilized herein, references to doping or
Suitable dopants include addition of elements from adjoining
groups of the periodic table, e.g., group II, group IV, and/or
group VI elements, or other main-group or rare-earth ele
ments. In certain embodiments, the dopant is a transition
metal or rare earth element, e.g., a ZnS nanoparticle may be

10

15

25

30

35

40

45

50

55

60

doped with Mn" or Cu".

IIA-VIB (i.e., 2-16) material including a first element from
group 2 of the periodic table and a second element from group
16 of the periodic table, including but not limited to magne

65

8
sium sulfide (MgS), magnesium selenide (MgSe), magne
sium telluride (MgTe), calcium sulfide (CaS), calcium
selenide (CaSe), calcium telluride (CaTe), strontium sulfide
(SrS), strontium selenide (SrSe), strontium telluride (SrTe),
barium sulfide (BaS), barium selenide (BaSe), barium tellu
ride (BaTe), and/or ternary or quaternary alloys of these mate
rials. The material may be doped with at least one suitable
dopant.
IIB-VIB (i.e., 12-16) material including a first element
from group 12 of the periodic table and a second element from
group 16 of the periodic table, including but not limited to
ZnS, ZnSe, zinc telluride (ZnTe), CdS, CdSe, CdTe. HgS,
mercury selenide (HgSe), mercury telluride (HgTe), and/or
ternary or quaternary alloys of these materials. The material
may be doped with at least one Suitable dopant.
II-V (i.e., 12-15) material including a first element from
group 12 of the periodic table and a second element from
group 15 of the periodic table, including but not limited to
Zinc phosphide (Zn-P), Zinc arsenide (Zn-AS), cadmium
phosphide (CdP), cadmium arsenide (Cd-AS), cadmium
nitride (CdN), Zinc nitride (Zn-N), and/or ternary or qua
ternary alloys of these materials. The material may be doped
with at least one Suitable dopant.
III-IV (i.e., 13-14) material including a first element from
group 13 of the periodic table and a second element from
group 14 of the periodic table, including but not limited to
boron carbide (BC), aluminum carbide (Al..C.), gallium
carbide (GalC), and/or ternary or quaternary alloys of these
materials. The material may be doped with at least one suit
able dopant.
III-VI (i.e., 13-16) material, which includes a first element
from group 13 of the periodic table and a second element from
group 16 of the periodic table, including but not limited
aluminum Sulfide (Al2S), aluminum selenide (Al-Sea), alu
minum telluride (Al-Te), gallium sulfide (GaS), gallium
Selenide (GaSes), indium Sulfide (InS), indium selenide
(InSes), gallium telluride (GaTes), indium telluride
(InTes), and/or ternary or quaternary alloys of these materi
als. The material may be doped with at least one suitable
dopant.
IV-VI (i.e., 14-16) material, which includes a first element
from group 14 of the periodic table and a second element from
group 16 of the periodic table, including but not limited to
lead sulfide (PbS), lead selenide(PbSe), lead telluride (PbTe),
tin sulfide (SnS), tin selenide (SnSe), tin telluride (SnTe),
and/or ternary or quaternary alloys of these materials. The
material may be doped with at least one Suitable dopant.
Material including a first element from any transition metal
group of the periodic table and a second element from any
group of the d-block elements of the periodic table, including
but not limited to nickel sulfide (NiS), chromium sulfide
(CrS), copper indium sulfide (CuInS), and/or ternary or qua
ternary alloys of these materials. The material may be doped
with at least one Suitable dopant.
Outer inorganic shell(s): The material used on any shell or
Subsequent numbers of shells grown onto the core III-V nano
particle preferably has a crystal phase compatible with that of
the core. Compatible crystal phases may be the same, e.g., a
hexagonal or cubic material formed on a hexagonal or cubic
core. Compatible crystal phases may alternatively be differ
ent phases, wherein a lattice spacing of the core material is
close enough to a lattice spacing of the shell material Such that
deleterious lattice Strain and/or relaxation (and concomitant
defect generation) does not occur. In some embodiments, the
shell material is closely lattice-matched to (i.e., has approxi
mately the same lattice constantas) the core material. In other
embodiments, a buffer layer is formed on the core to amelio

US 7,588,828 B2
rate the effects of lattice mismatch between the core material

and a subsequently formed shell material. The material of a
buffer layer and/or a shell material formed on the core may
include at least one of the following:
IIA-VIB (i.e., 2-16) material, which includes a first ele
ment from group 2 of the periodic table and a second element
from group 16 of the periodic table, including but not limited
to MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe,
and/or ternary or quaternary alloys of these materials. The
material may be doped with at least one Suitable dopant.
IIB-VIB (i.e., 12-16) material, which includes a first ele
ment from group 12 of the periodic table and a second ele
ment from group 16 of the periodic table, including but not
limited to ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe. HgS, HgSe,
HgTe, and/or ternary or quaternary alloys of these materials.
The material may be doped with at least one suitable dopant.
II-V (i.e., 12-15) material, which includes a first element
from group 12 of the periodic table and a second element from
group 15 of the periodic table, including but not limited to
Zn-P, ZnAS, CdP, Cd AS., CdN, Zn-N, and/or ter
nary or quaternary alloys of these materials. The material may
be doped with at least one suitable dopant.
III-V (i.e., 13-15) material, which includes a first element
from group 13 of the periodic table and a second element from
group 15 of the periodic table, including but not limited to BP.

10

15

25

AlP, AlAs. AlSb; GaN, GaP, GaAs, GaSb. InN, InP, InAs,

InSb, AlN, BN, and/or ternary or quaternary alloys of these
materials. The material may be doped with at least one suit
able dopant.
III-IV (i.e., 13-14) material, which includes a first element
from group 13 of the periodic table and a second element from
group 14 of the periodic table, including but not limited to
BC, Al C. GaC, and/or ternary or quaternary alloys of
these materials. The material may be doped with at least one
Suitable dopant.
III-VI (i.e., 13-16) material, which includes a first element
from group 13 of the periodic table and a second element from
group 16 of the periodic table, including but not limited
Al2S3, Al2Sea. Al-Tes, Ga2S3, Ga-Sea. In-Ss, InTes, and/or
ternary or quaternary alloys of these materials. The material
may be doped with at least one Suitable dopant.
IV-VI (i.e., 14-16) material, which includes a first element
from group 14 of the periodic table and a second element from
group 16 of the periodic table, including but not limited to
PbS, PbSe, PbTe, SnS, SnSe, SnTe, and/or ternary or quater
nary alloys of these materials. The material may be doped
with at least one Suitable dopant.
Nanoparticle shape: The shape of the nanoparticle pro
duced according to embodiments of the present invention
may be spherical. In other embodiments, the nanoparticle has
the shape of a rod, disk, tetrapod, or star. Control of the shape
of the nanoparticle may be achieved in the particle growth
process by the addition of a compound that will preferentially
bind to a specific lattice plane of the growing particle and
Subsequently inhibit or slow particle growth in a specific
direction. Example of compounds that may be added include
phosphonic acids (n-tetradecylphosphonic acid, hexylphos
honic acid, 1-decanesulfonic acid, 12-hydroxydodecanoic
acid, or n-octadecylphosphonic acid).
Various embodiments of the present invention are utilized
to form a plurality of monodisperse nanoparticles that are
Substantially pure (i.e., uniform in chemical composition).
Each nanoparticle may substantially consist of a III-V mate
rial, and may be stabilized from particle aggregation and the
Surrounding chemical environment by an organic layer. For
example, the nanoparticle may be represented by the formula

(ME),L, in which M represents a group III element, E rep

30

35

10
resents a group V element, and L represents a coordinating
organic layer or capping agent. Each nanoparticle may form
on and arounda molecular cluster which may have a chemical
formula different from that of the nanoparticle core and/or
shell(s).
A molecular cluster is utilized as a template to seed the
growth of nanoparticles (with compositions (ME)L, where M
and E are the two types of ions making up the nanoparticle,
e.g., M is a group III ion and E is a group Vion, and L is the
capping agent) from precursors including elements other than
those in the molecular cluster. A Small quantity of a Suitable
molecular cluster is mixed with a solvent having a relatively
high boiling point. This solvent can also act as a capping
agent, and may be, e.g., a Lewis base coordination compound
Such as a phosphine, a phosphine oxide, an organo-thiol, an
amine, oran organic acid. The solvent may alternatively bean
inert Solvent such as an alkane (e.g., octadecence), and may
be utilized with the addition of an additional capping agent
compound Such as oleic acid. As the reaction temperature is
increased, suitable source precursors for M and E are peri
odically added either drop-wise in liquid from or as small
quantities of solid powder. Additionally, a source for Manda
source for E may be added to the reaction mixture. The Mand
E precursor source(s) may either be in the form of two sepa
rate precursors (one containing M and the other containing
E), or as a single-source precursor that contains both M and E
within a single molecule.
The nanoparticle material preferably has a crystal phase
compatible with that of the molecular cluster. Compatible
crystal phases may be the same, e.g., a hexagonal or cubic
nanoparticles formed on a hexagonal or cubic molecular clus
ter. Compatible crystal phases may alternatively be different
phases, wherein a lattice spacing of the nanoparticle material
is close enough to a lattice spacing of the molecular cluster
material Such that deleterious lattice strain and/or relaxation

(and concomitant defect generation) does not occur. In some
embodiments, the nanoparticle material is closely lattice
matched (i.e., has approximately the same lattice constant) to
the molecular cluster material.
40

45

50

55

60

65

Other regents which have the ability to control the shape of
the nanoparticles may be added to the reaction mixture, e.g.,
a compound that can preferentially bind to a specific face (i.e.,
a lattice plane) of the growing nanoparticle and thus inhibit or
slow particle growth along that specific direction of the par
ticle. Moreover, other source precursors (including other
elemental species and or dopants) may be added to the reac
tion to produce ternary, quaternary, or doped particles.
After the molecular cluster is mixed with the coordinating
compound, the reaction mixture is heated at an approximately
steady rate until nanoparticle growth is initiated upon the
Surfaces of the molecular cluster templates. At an appropriate
temperature (e.g., approximately 100° C. to approximately
350° C.), further quantities of M and E precursors may be
added to the reaction mixture, e.g., as a batch addition where
Solid precursors or solutions containing the precursor atoms
are added in bulk, or as an addition over a period of time
(which may extend up to and include the entire reaction time)
of the solution phase precursors. In various embodiments, the
nanoparticle nucleation stage is separated from the nanopar
ticle growth stage, enabling a high degree of control of nano
particle size. Nanoparticle size may also be controlled by the
temperature of the reaction (generally, higher temperatures
lead to larger nanoparticles) and concentrations of precursors
present in the reaction. The size of the growing nanoparticles
may be approximately determined by use of UV and/or PL
spectra of the reaction Solution either by an in situ optical
probe or from aliquots of the reaction solution. After the

US 7,588,828 B2
11
desired nanoparticle size is obtained, the temperature may be
reduced by a specific amount (e.g., by approximately 20°C.
to approximately 80°C.) and the mixture left to anneal for a
period of time, e.g., in the range of approximately 10 minutes
to approximately 72 hours.
In other embodiments, further reaction steps are performed
in order to form core-shell and/or core-multi-shell nanopar
ticles. Preparation of core-shell nanoparticles having the
composition ME/NY, where N and Y are the elements of the
shell compound formed around the ME core, may be under
taken either before or after nanoparticle isolation, during
which the nanoparticles are isolated from the reaction and
redissolved in new (i.e., clean) capping agent. This new cap
ping agent may either be the same capping agent compound
utilized in the formation reaction or a different capping agent
compound. N and Y precursors are added to the reaction
mixture, either in the form of two separate precursors (one
containing N and the other containingY), or a single-source
precursor that contains both NandY within a single molecule,
thus forming a ME/NY core-shell nanoparticle.
The process may be repeated with the appropriate precur
sors to form desired core-multi-shell nanoparticles. Addi
tional shells may include elements other than M. E., N, andY.
Molecular Clusters

12
The molecular cluster may include only one of the elemen
tal species (or multiple elemental species from the same peri
odic table group) desired in the final nanoparticles. In an
embodiment in which a III-V nanoparticle is desired, suitable
molecular clusters may include either the group III element or
the group V element desired in the nanoparticle, as well as
organic moieties. Examples include but are not limited to:
II-V-based molecular clusters such as:
10

{RZn}{PR' (R=I, PEt Ph; R'=SiMe);

15

25

RAINR

30

35

{(PPh)Hg (SPh):
40

RMEBus (M=Zn, Cd, Hg: E-S, Se, Te: R=Me, Et, Ph):
45

50

55

CHGa NCHCH(CH):

DXE.M.(SR) (E=S, Se, Te; M=Zn, Cd, Hg:
X-Me-NH", Li", EtNH);
CdS (SPh).L.;
HgSea (SePh)(PPh"Pr):
Hg-Sea (SePh);
CdSe (SePh)(PPrs):
CdSe (SePh)-(PPh3);
M.(SPh)"LXI (M=Zn, Cd, Hg: X-MeN", Li": Zn
(SEt)Eto);
MeMEiPr) (M=Zn, Cd, Hg: E=S, Se, Te);

IRCdSR's (R=O(CIO), R=PPh, Pr);
Cdo E (EPh) (PR). (E., E-Te, Se, S);
CdSe(SePh), Cl);
|M.Te' (M=Cd, Hg);
PhMCdo (PEt). (M-Te, Se);

or IV-VI molecular clusters such as:

MeGaNBul:
60

EtGaNEt:

RGaPR' (R=Pr. CH Me: R'=Bu, CHMe):
RNInRI (R=Cl, Br, I, Me: R=Bu, CFs, CHF);
RInPR' (R=Pr, C.H.Me, Et; R'=SiPh, C.H.Me,
SiPr);
RInPRI (R=Et, R=SiMe(CMe"Pr)).

(Ph-P)(SEt)s (Br)(HgBr);
(PhP)Hg (SEt).Br:
HgTel N(CH2CH2Et);
IIB-VIIB molecular clusters such as:

CHMe);

RGaNR' (R=Ph, Me: R'=Ph, CFs, SiMe, Bu);

Cd4 InoS3s (H2O)2oCCoH2sNA).s:
The molecular cluster may include substantially none of
the elemental species desired in the final nanoparticles. In an
embodiment in which a III-V nanoparticle is desired, suitable
molecular clusters may include organic moieties but none of
the group III and group V elements desired in the nanopar
ticle. Examples include but are not limited to:
IIB-VIIB molecular clusters such as:

(R=Me, CHiPr', Ph; R'=Pr', CHiPr',

(SiPr). ASAIH):
PrNAIHL:
RAINRI (R=Me, Et, C1, CHPh, CH, Pr, Ph; R'=Me H,
Br, C=CPh, Pr', (CH), Me, (CH)2NMe, SiPhs);

SAIR (R=C(SMe), CEtMe...);
SAINMes:
TeAlR (R-Cp*, CEtMe...);
(C(SiMe))GaSa;

TBuGaSI:
RGaSea (R=Bu, CMeEt, CEt, C(SiMe), Cp*, Bu):

Eto: FIG. 4B depicts (RGaS, FIG. 4C depicts Bu'GaS);

FIG. 4D depicts RInSea; and FIG.3E depicts XIMoSea
(SPh) (where X=cation, M=Zn, Cd, Te).
The molecular cluster may include substantially all of the
elemental species desired in the final nanoparticles. In an
embodiment in which a III-V nanoparticle is desired, suitable
molecular clusters may include the group III and group V
elements desired in the nanoparticle, as well as organic moi
eties. Examples include but are not limited to:
EtGaNEt:
MeGaN(4-CHF):
(MeCaNBu);

P'Bus

Zn(PBu2)Cla:
(TBu)GaSea:
TBuGaS);
RInSea (R="Bu, CMeEt, Si(Bu), C((SiMe.)));
RInS (R=Bu, CMeEt);
RGaS) (R="Bu, CMe, Et, CEt);

cursors contribute ions which bond to the cluster and form the

desired nanoparticle. Hence, the molecular clusters facilitate
the nucleation and growth of nanoparticles that may other
wise be quite difficult to fabricate in the absence of the
molecular clusters. The choice of molecular clusters may
depend on the desired composition of the final nanoparticle,
as in the following examples. Exemplary molecular clusters
are depicted in FIGS. 4A-4E. FIG. 4A depicts Zn(SEt)

|M.C.(PPh) (P"Prs), (M=Zn, Cd):
Li(thf). (Ph-P)Cd:
Zn(PPh)Cl(PRR), (PRR'—PMe"Prs,
PEtPh):
or III-VI-based molecular clusters such as:

In accordance with embodiments of the invention, molecu

lar clusters are used as templates for the formation of nano
particles thereon. The molecular clusters may be formed of a
plurality of substantially identical molecules. When other
precursors are combined with the molecular clusters, the pre

IRCdNRI (R=Cl, Br, I, PEt, C=CSMe: R=PEt, I):
IRCdNR's (R-alkyl or aryl group and R'-alkyl or aryl
group);

65

S{SnR} (R=C(SiMe), Me, Ph):
See {SnRI (R=CF, C.H.Mes, p-Tol, C(SiMe)).
The molecular cluster may include at least one transition
metal and at least one element from the d-block of the peri
odic table. Examples include but are not limited to:
CuSe(PR) (R=EtPh, "Prs, Cy);

CusTe(Bu)(PPhEt),;
CuoTea (Bu),(PEt3)s:

US 7,588,828 B2
14

13
Cu, Tes(PPrMe);
NiaSe(PPh3);
Agao(TelPh), Teo (PEt3)2;

Sn(NO),
Pb(NO);
or elemental N. P. As, Sb, and/or Bi.
Single-source precursors of at least one group III element
and at least one group V element (e.g., the precursor molecule
includes both M and E for nanoparticle ((ME)L) may
include organometallic compounds, inorganic salts, and/or
coordination compounds, as in the following examples.

Agao Ses(Se'Bu) (PnPrs)s:
Co4(LL-Se) (PPh3);
Co(l-Se) (PPh3);
IWSe(dmpe).Br.";
RuBi(CO);
FeP(CO);
FeN(CO)2.

(Me)GaN(H)"Bul:
10

Precursors

In accordance with embodiments of the invention, various

precursors are utilized as sources for one or more of the
elemental species desired in the final nanoparticle. Examples
include but are not limited to:

Sources of the group III elements B, Al. Ga, or In:
III-phosphines (i.e., at least one group III element coordi
nated to a phosphine),
III-(TMS),
III-(alkyls) (e.g., trimethyl indium),
III-(aryl),
III-(acetate) (e.g., III-(myrisate)),
mixed alkyl- and aryl-acetates (e.g., III-(myrisate)(ac
etate) or III-(myrisate)(acetate)),
III-(III) acetylacetonate;
organometallics such as MR (M=Ga, In, Al, B: R-alky or

15

MeInPBul:
MeInSb'Bus:
25

30

35

40

Sources of the group V elements N. P. As, Sb, or Bi:

45

organometallics Such as:

MR (M-Mg: R-alky or aryl group (MgTBu));

50

MR (M=Zn, Cd, Te: R-alky or aryl group (MeZn, EtZn
MeCd, EtCd));
MR (M-Ga, In, Al, B: R-alky oraryl group AlR, GaR.

InR (R-Me, Et, Pr));

55

coordination compounds Such as carbonates:
MCO (M=Ca, Sr., Ba);
magnesium carbonate hydroxide (MgCO)"Mg(OH):
M(CO), (M=Zn, Cd);
MCO, (M=Pb);
acetates;

60

PO;
ASOs,
SbO:
SbO;

SbOs:
BiO,
Bi(NO);

precursors are utilized as sources for one or more of the
elemental species desired in one or more shells formed
around the core of the final nanoparticle. For a shell of com
position ME (which includes the elements M and E), a source
for element M may be further added to the reaction and may
includean M-containing species that has the ability to provide
the growing particles with a source of M ions. Likewise, a
source for element E may be further added to the reaction and
may include an E-containing species that has the ability to
provide the growing particles with a source of E ions. The
precursor may be an organometallic compound, an inorganic
salt, a coordination compound, or an elemental source.
Examples of precursor sources for an element M for a II-VI,
III-V, III-VI or IV-V shell include but are not limited to:

NHR, PHR, AsFIR, SbHR:

coordination compound such as carbonates, such as MCO
(M=P) or bismuth subcarbonate ((BiO)CO);
3-diketonates or derivatives thereof. Such as acetylaceto
nate (2.4-pentanedionate);
CHCOOCH=C(O )CHIM (M=Bi);
CHCOOCH=C(O )CHIM (M=Bi);
inorganic salts such as oxides or nitrates, such as:

Eta AlAs Bula:
TBuAISb(SiMe);
"BuGaAs Bul;
Me,GaAs Bull;
EtGaAs Bull.
In accordance with embodiments of the invention, various

organometallics, in which R-Me, Et, Bu, Bu, Pr, Ph, or

PH, Ash;
M(NMe) (M=P, Sb, As; dimethyldrazine (MeNNH));
ethylazide (Et-NNN):
hydrazine (HNNH);
MeSiN:

EtInSb(SiMe),
MeInNEt,

Shell Precursors

or elemental B, Al, Ga, and/or In.

similar groups, such as:
NR, PR, AsR SbR;
NHR, PHR, AsHR, SbHR:

TBuGaPH:
Me,GaP(Pr):
TBuGalPArl,
TBuGaP(H)CH):
Ga(As Bu2), EtGaAs(SiMe3),
TBuGaAs(SiMe3);
EtGaSb(SiMe);
(MeSiCH). InP(SiMe):
RInP(SiMe),

aryl group such as Me, Et, Pr);

coordination compounds such as carbonates, such as
M(CHC) (M=B, Al, Ga. In);
3-diketonates or derivatives thereof. Such as acetylaceto
nate (2.4-pentanedionate);
CHCOOCH=C(O-)CH):
CHCOOCH=C(O-)CHI (M=B, Al. Ga, In):
inorganic salts such as oxides or nitrides, such as:
In O.
Ga-O;
Al(NO);
In(NO);
Ga(NO);

HGaNH2,
PhGaP(SiMe.) Ga(Ph)Cl]EtGaP(SiMe),
EtGaPEt,

65

M(CHCO) (M=Mg, Ca, Sr, Ba, Zn, Cd, Hg);
M(CHC) (M=B, Al. Ga, In);
3-diketonates or derivatives thereof. Such as acetylaceto
nate (2.4-pentanedionate);
CHCOOCH=C(O-)CHI (M=Mg, Ca, Sr., Ba, Zn,
Cd. Hg);
CHCOOCH=C(O-)CHI (M=B, Al. Ga, In)
oxalates such as SrCO, CaCO BaCO, or SnCO;

US 7,588,828 B2
15
inorganic salts such as oxides or nitrates, such as:

16
PbO;

PbO:
Bi(NO);
Sn(NO);
Pb(NO);

SrO;
ZnO;
CdO;

In O,
GaOs:
SnO;
PbO:

Mg(NO);
Ca(NO);
Sr(NO);
Ba(NO);
Cd(NO);
Zn(NO);
Hg(NO),
Al(NO);
In(NO);
Ga(NO);
Sn(NO),
Pb(NO);
or an elemental source of Mg, Ca,Sr., Ba, Zn, Cd, Hg, B, Al,

or an elemental source of Sn, Ge, N. P. As, Sb, Bi, S, Se, Te,
Sn, or Pb.

10

15

(Me)GaN(H)"Bul:

Ga, In, Sn, or Pb.

HGaNH2,

Examples of precursor sources for an element E fora II-VI,

(PhGaP(SiMe.) Ga(Ph)Cl]EtGaP(SiMe);

III-V, III-VI or IV-V shell include but are not limited to:

organometallics, in which R-Me, Et, Bu, Bu, Pr, Ph, or

similar groups, such as:
NR, PR, AsF, SbR;
NHR, PHR, AsFIR, SbHR:
NHR, PHR, Ash R, SbHR:
PH, Ash;
M(NMe) (M=P, Sb, As):
dimethyldrazine (MeNNH);
ethylazide (Et-NNN):
hydrazine (HNNH);
MeSiN:

EtGaPEt;

25

30

35

40

Sn(CH),
Sn(CH):
Sn(CH) (OOCH):
coordination compounds Such as carbonates:
45

Eta AlAs Bula:
TBuAISb(SiMe);
"BuGaAs Bul;
Me,GaAs Bul:
EtGaAs Bull.

Examples of single-source precursors for elements Mand
E for a II-V shell (i.e., M is a group II element and E is a group
V element) include but are not limited to:

MeCdP'Bus

50

ZnP(SiPh).
Examples of single-source precursors for elements Mand
E for a IV-VI shell (i.e., M is a group IV element and E is a
group VI element) include but are not limited to:
lead (II) dithiocarbamates:
lead (II) selenocarbamates.

55

EXAMPLES

selenourea (HNC(=Se)NH;
inorganic salts such as oxides or nitrates:
ASOs,
60

SbO:
SbOs:
BiO,
SO:
SeO;
Te0:
SnO;

MeInPBul;
MeInSb'Bus:

EtInSb(SiMe):
MeInNEt;

group);
thiourea S—C(NH);

thiourea;

TBuGaPH:
Me,GaP(Pr):
TBuGalPAr;
TBuGaP(H)CH):
Ga(As Bul);
EtGaAS(SiMe):
TBuGaAs(SiMe3);
EtGaSb(SiMe):
(MeSiCH), InP(SiMe));
RInP(SiMe);

MR (M=S, Se Te: R=Me, Et, Bu, Bu, or similar group);
HMR (M=S, Se Te: R=Me, Et, Bu, Bu, Pr, Ph, or similar

bismuth subcarbonate (BiO)CO:
M(CO);
acetate M(CHCO) (M=S, Se, Te):
M(CHC), (M=Sn, Pb);
3-diketonates or derivatives thereof. Such as acetylaceto
nate (2.4-pentanedionate);
CHCOOCH=C(O )CHIM (M=Bi);
CHCOOCH=C(O-)CHIM (M=S, Se, Te);
CHCOOCH=C(O-)CHIM (M=Sn, Pb):

Examples of single-source precursors for elements Mand
E for a II-VI shell (i.e., M is a group II element and E is a
group VI element) include but are not limited to:
bis(dialkyldithio-carbamato)M, (II) complexes or related
Se and Te compounds of the formula M(SCNR) (M=Zn,
Cd, Hg, S=S, Se, O, Te: R-alkyl orary groups;
CdSSiMe):
Cd.(SOCR)py:
Cd.(SePh).
Examples of single-source precursors for elements Mand
E for a III-V shell (i.e., M is a group III element and E is a
group V element) include but are not limited to:

65

All syntheses and manipulations were carried out under a
dry oxygen-free argon or nitrogen atmosphere using standard
Schlenk and glove box techniques. All solvents were analyti
cal grade and distilled from appropriate drying agents prior to
use (Na/K-benzophenone for THF. EtO, toluene, hexanes,
pentane; magnesium for methanol and ethanol and calcium
hydride for acetone). All chemicals were analytical grade.
Elemental analyses were performed on a CARLO ERBA
CHNS-O EA1108 Elemental Analyzer. UV-vis absorption
spectra were measured on a Thermospectronic Hewios 3

US 7,588,828 B2
17
Spectrophotometer. PL spectra were measured with a Fluo
rolog-3 (FL3-22) photospectrometer with an excitation wave
length of 380 nm. Spectra were obtained with the slits set at 2
nm and an integration time of 1 second, or measured in situ
using an Ocean Optics 2000 USB probe. Powder X-Ray
diffraction (PXRD) measurements were performed on a
Bruker AXS D8 diffractometer using monochromatic
Cu—K radiation with the samples mounted flat and Scanned
from 10° to 70° with step sizes of 0.04° and a count rate of 2.5
seconds. PXRD measurements were taken using a glancing
angle incidence detector at an angle of 3 for 20 values of
20°-60° in steps of 0.04 and a count time of 1 second. A
Philips CM200 transmission electron microscope (TEM) was
used to observe the morphology and size distribution of nano
particles and for energy dispersive analysis of X-ray fluores
cence (EDAX). The samples for TEM and EDAX were pre
pared by placing a drop of a dilute suspension of a sample in
toluene on a copper grid (300 meshes, available from Agar
Scientific). The excess solvent was allowed to dry at room

10

15

temperature.

Preparation of IHNEtCd(SPh)
To a stirred methanol (60 ml) solution of benzenethiol
(20.00 g, 182 mmol) and triethylamine (18.50 g, 182 mmol)
was added dropwise CdCNO).4H2O (21.00 g, 68.00 mmol)
that had previously been dissolved in methanol (60 mL). The
solution was then allowed to stir while warming until the
precipitate had completely dissolved to leave a clear Solution.
This was then placed at 5°C. for 24 hours, during which large
colorless crystals of HNEtCd (SPh) formed.
Preparation of IHNEta CdSe (SPh)
To a stirred acetonitrile (100 ml) solution of IHNEtCd
(SPh) (80.00 g, 45.58 mmol) was added selenium powder
(3.57g, 45.21 mmol), and the resulting slurry was left to stir
for 12 hours, producing a white precipitate. A further 750 ml

25

30

35

ofacetonitrile was added and the solution warmed to 75°C. to

give a clear pale yellow solution. The solution was allowed to
cool to 5°C., yielding large colorless crystals. The crystals
were washed in hexane and recrystallized from hot acetoni
trile, resulting in 22.50 g of HNEtCdSe (SPh).
Preparation of CdSe Nanoparticles from Et NHCdSea
(SPh)/TOPSe/Cd(CHCO) in HDA
HDA (300 g) was placed in a three-neck flask and dried/
degassed by heating to 120° C. under a dynamic vacuum for
1 hour. The solution was then cooled to 70° C. To this was

added 1.0 g of EtNHCdSe (SPh) (0.311 mmol),
TOPSe (20 ml. 40.00 mmol) previously prepared from dis
solving selenium powder in TOP and CdCCHCO) (10.66
g, 40.00 mmol), and the temperature of reaction mixture was
gradually increased from 70° C. to 180° C. over an 8 hour
period. The progressive formation and growth of the nano
particles was monitored by their emission wavelength by
taking aliquots from the reaction mixture and measuring the
UV-vis and PL spectra thereof. The reaction was stopped
when the emission spectra corresponded to the desired size
(572 nm) by cooling the reaction to 60° C., followed by
addition of 200 ml of dry “warm' ethanol, resulting in pre
cipitation of nanoparticles. The resulting CdSe nanoparticles
were dried before re-dissolving in toluene filtering through
Celite, followed by re-precipitation from warm ethanol to
remove any excess HDA and CdCHCO). This produced
9.26 g of HDA-capped CdSe nanoparticles.
Preparation of CdSe Nanoparticles from Et NHCdSea
(SPh)/TOPSe/Cd(CHCO) in HDA
HDA (250 g) and octylamine (20 g) were placed in a
three-neck flask and dried/degassed by heating to 120° C.

40

45

50

55

60

65

18
under a dynamic vacuum for 1 hour. The solution was then
cooled to 70° C. To this was added 1.0 g of EtNHCdSe,
(SPh) (0.311 mmol), TOPSe (1 M, 4 ml, 4.00 mmol) pre
viously prepared from dissolving selenium powder in TOP,
and CdCHCO), dissolved in TOP (0.5 M, 4 ml, 2.00
mmol). The temperature of reaction mixture was gradually
increased from 70° C. to 150° C. over a 1 hour period. A
further 17 ml (17.00 mmol) of TOPSe and 27 ml of 0.5 M
Cd(CHCO), dissolved in TOP (13.50 mmol) were added
drop-wise while the temperature was gradually increased to
200°C. over a 24 hour period. The progressive formation and
growth of the nanoparticles was monitored via emission
wavelength by taking aliquots from the reaction mixture and
measuring the UV-vis and PL spectra. The reaction was
stopped when the emission spectra corresponded to the
desired size (630 nm) by cooling the reaction to 60° C. fol
lowed by addition of 200 ml of dry “warm' ethanol, resulting
in a precipitation of particles. The resulting CdSe nanopar
ticles were dried before re-dissolving in toluene filtering
through Celite, followed by re-precipitation from warm etha
nol to remove any excess HDA. This produced 4.56 g of
HDA-capped CdSe nanoparticles.
Preparation of CdSe Nanoparticles from EtsNHCdSe,
(SPh)/TOP/Se/CdO in HDA
HDA (150 g) and t-decylphosphonic acid (0.75 g) were
placed in a three-neck flaskand dried and degassed by heating
to 120° C. under a dynamic vacuum for 1 hour. The solution
was then cooled to 80°C. To this was added 0.5g of Et NH
CdSe (SPh) (0.156 mmol), 20 ml of TOP 0.6 g of
selenium powder (7.599 mmol) and 0.8 g. CdC (6.231 mmol).
The reaction mixture was stirred, resulting in a pale red,
cloudy mixture. The temperature of the reaction mixture was
gradually increased from 80°C. to 250° C. overa period of 24
hours. The progressive formation and growth of the nanopar
ticles was followed via emission wavelength by taking ali
quots from the reaction mixture and measuring the UV-vis
and PL spectra. The reaction was stopped when the emission
spectra corresponded to the desired size (593 nm) by cooling
the reaction to 60° C. followed by addition of 200 ml of dry
“warm' ethanol, resulting in a precipitation of particles. The
resulting CdSe nanoparticles were dried before re-dissolving
in toluene filtering through Celite, followed by re-precipita
tion from warm ethanol to remove any excess HDA. This
produced 1.55g of HDA-capped CdSe nanoparticles.
Preparation of CdSe Nanoparticles from Et NHCdSea
(SPh)/TOPSe/Cd(HO), in HDA
HDA (400 g) was placed in a three-neck flaskand dried and
degassed by heating to 120° C. under a dynamic vacuum for
1 hour. The solution was then cooled to 70° C. To this was

added 1.00 g of EtNHCdSe (SPh) (0.278 mmol),
20.0 ml of TOPSe, (2 M solution) and 5.85g of Cd(OH),
(40.00 mmol). The reaction mixture was stirred, resulting in a
pale yellow, cloudy mixture. The temperature of the reaction
mixture was gradually increased from 70° C. to 240° C. over
a period of 24 hours. The progressive formation and growth of
the nanoparticles was followed via emission wavelength by
taking aliquots from the reaction mixture and measuring the
UV-vis and PL spectra. The reaction was stopped when the
emission spectra corresponded to the desired size (609 mm)
by cooling the reaction to 60° C. followed by addition of 200
ml of dry “warm' ethanol, resulting in a precipitation of
particles. The resulting CdSe nanoparticles were dried before
re-dissolving in toluene filtering through Celite, followed by
re-precipitation from warm ethanol to remove any excess
HDA. This produced 10.18 g of HDA-capped CdSe nanopar
ticles.

US 7,588,828 B2
19
Preparation of CdSe Nanoparticles from Et NHCdSea
(SPh)/TOPSe/MeCd in HDA
HDA (100g) was placed in a three-neck flaskand dried and
degassed by heating to 120° C. under a dynamic vacuum for
1 hour. The solution was then cooled to 70° C. To this was

added 0.13 g of EtNHCdSe (SPh) (0.036 mmol),
2.5 ml of TOPSe, (2 M solution) and 0.71 g MeCd that had
previously been dissolved in TOP (0.358 ml, 5.00 mmol),
and the reaction mixture was stirred. The temperature of the
reaction mixture was gradually increased from 80°C. to 260°
C. over a period of 24 hours. The progressive formation and
growth of the nanoparticles was followed via emission wave
length by taking aliquots from the reaction mixture and mea
suring the UV-vis and PL spectra. The reaction was stopped
when the emission spectra corresponded to the desired size
(587 nm) by cooling the reaction to 60° C. followed by
addition of 100 ml of dry “warm' ethanol, resulting in a
precipitation of particles. The resulting CdSe nanoparticles
were dried before re-dissolving in toluene filtering through
Celite, followed by re-precipitation from warm ethanol to
remove any excess HDA. This produced 1.52 g of HDA
capped CdSe nanoparticles.
Preparation of CdSe Nanoparticles from Et NHCdSea
(SPh)/TOPSe/MeCd in HDA
HDA (100g) was placed in a three-neck flaskand dried and
degassed by heating to 120° C. under a dynamic vacuum for
1 hour. The solution was then cooled to 70° C. To this was

added 0.13 g of EtNHCdSe (SPh) (0.036 mmol).
The temperature was then increased to 100° C. and main
tained at this temperature while 2.5 ml of TOPSe, (2 M
solution) and 0.71 g MeCd that had previously been dis
solved in TOP (0.358 ml, 5.00 mmol) were added drop-wise
over a four-hour period. The progressive formation and
growth of the nanoparticles was followed via emission wave
length by taking aliquots from the reaction mixture and mea
suring the UV-Vis and PL spectra. The reaction was stopped
when the emission spectra corresponded to the desired size
(500 nm) by cooling the reaction to 60° C. followed by
addition of 100 ml of dry “warm' ethanol, resulting in a
precipitation of particles. The resulting CdSe nanoparticles
were dried before re-dissolving in toluene filtering through
Celite, followed by re-precipitation from warm ethanol to
remove any excess HDA. This produced 1.26 g of HDA
capped CdSe nanoparticles.
Preparation of CdSe Nanoparticles from EtsNHCdSe,
(SPh)/TOPSe/(CHCOO)Cd in HDA
HDA (200g) was placed in a three-neck flaskand dried and
degassed by heating to 120° C. under a dynamic vacuum for

5

1 hour. The solution was then cooled to 75° C. To this was
10

15

25

30

35

40

45

50

1 hour. The solution was then cooled to 80° C. To this was

added 0.5g of Et NHCdSe (SPh) (0.139 mmol). 20
ml of TOPSe(2M solution) and a solution of 2.568 gCdO (20
mmol) previously dissolved in steric acid (23.00 g). The
reaction mixture was stirred, resulting in a pale yellow, clear
Solution. The temperature of the reaction mixture was gradu
ally increased from 70° C. to 220° C. over a period of 24
hours. The progressive formation and growth of the nanopar
ticles was followed via emission wavelength by taking ali
quots from the reaction mixture and measuring the UV-vis
and PL spectra. The reaction was stopped when the emission
spectra corresponded to the desired size (590 nm) by cooling
the reaction to 60° C. followed by addition of 400 ml of dry
"warm' ethanol, resulting in a precipitation of nanoparticles.

20
The resulting CdSe nanoparticles were dried before re-dis
solving in toluene filtering through Celite, followed by re
precipitation from warm ethanol to remove any excess HDA.
This produced 4.27 g of HDA-capped CdSe nanoparticles.
Preparation of CdSe Nanoparticles from Et NHCdSea
(SPh)/TOPSe/CdCO, in HDA
HDA (50 g) was placed in a three-neck flask and dried/
degassed by heating to 120° C. under a dynamic vacuum for

55

60

65

added 0.5 g of EtNHCdSe (SPh) (0.156 mmol),
TOPSe (1.0 M, 5 ml, 5.00 mmol) previously prepared from
dissolving selenium powder in TOP and CdCO, dissolved in
TOP (0.5 M., 5 ml, 2.50 mmol), and the temperature of reac
tion mixture was gradually increased from 70° C. to 200° C.
over a 48 hour period. The progressive formation and growth
of the nanoparticles was monitored via emission wavelength
by taking aliquots from the reaction mixture and measuring
the UV-vis and PL spectra. The reaction was stopped when
the emission spectra corresponded to the desired size (587
nm) by cooling the reaction to 60°C., followed by addition of
200 ml of dry “warm' ethanol, resulting in a precipitation of
particles. The resulting CdSe nanoparticles were dried before
re-dissolving in toluene filtering through Celite, followed by
re-precipitation from warm ethanol to remove any excess
HDA. This produced 0.95g of HDA-capped CdSe nanopar
ticles.

Preparation of CdTe Nanoparticles from EtsNHCdSe,
(SPh)/TOPTe/Cd(CHCO) in HDA
HDA (200 g) was placed in a three-neck flask and dried/
degassed by heating to 120° C. under a dynamic vacuum for
1 hour. The solution was then cooled to 70° C. To this was

added 1.0 g of EtNHCdSe (SPh) (0.311 mmol), a
brown slurry of TOP (20 ml) with tellurium (2.55g, 20.00
mmol), and CdCCHCO) (4.33 g, 20.00 mmol). The tem
perature of reaction mixture was gradually increased from
70° C. to 160° C. over an 8 hour period. The progressive
formation and growth of the CdTe nanoparticles was moni
tored via emission wavelengths by taking aliquots from the
reaction mixture and measuring the UV-vis and PL spectra.
The reaction was stopped when the emission spectra corre
sponded to the desired size (624 nm) by cooling the reaction
to 60° C. followed by addition of 200 ml of dry “warm”
ethanol, resulting in a precipitation of nanoparticles. The
resulting CdTe nanoparticles were dried before recrystalliz
ing from toluene followed by re-precipitation from warm
ethanol to remove any excess HDA. This produced 6.92 g of
HDA-capped CdTe nanoparticles.
Preparation of III-V Nanoparticles
General procedure: A cluster Such as HNEtaZnoS
(SPh), and Small quantities of feedstock precursors, i.e., a
group III element precursor Such as In?myrisate) and a group
V element precursor such as P(TMS) are added to a solution
containing a capping agent. The temperature is then increased
(e.g., to between approximately 80° C. and approximately
140°C.) and the reaction stirred for a period of time (e.g.,
approximately 10 minutes to approximately 24hours), result
ing in the onset of III-V nanoparticle formation. Further drop
wise addition of both of the feedstock precursors may lead to
a red shift of the PL emission maximum of the quantum dots,
as monitored by an in situ PL probe. If further precursor is
added at this stage there may be no further red shift of the PL
maximum, thus signifying the conclusion of nanoparticle
growth. However, when the temperature is increased (by, e.g.,
5-40°C.), the PL maximum again may red shift. When more
precursors are added to the warmed reaction solution, the PL
maximum red may shift again. Therefore, this cycle of addi
tion of precursor followed by incrementally increasing the
reaction temperature may be repeated until the PL maximum

US 7,588,828 B2
21
peak is at the desired emission (also signifying the desired
nanoparticle size). The reaction may then be cooled to a lower
temperature (e.g., approximately 20°C. to approximately 60'
C. below the final reaction temperature) and allowed to anneal
for a further period of time (e.g., approximately 30 minutes to
approximately 7 days). Organic-capped III-V nanoparticles
may then be isolated from the reaction mixture.
Choice of molecular cluster: AII-VI molecular cluster may
preferably be used instead of a III-V one, as there are few
known III-V molecular clusters. Additionally, III-V molecu
lar clusters are difficult to make and are generally sensitive to
air and moisture. In contrast, many II-VI molecular clusters
are generally not sensitive to air or moisture and may be made
by simple procedures. III-V particles may be seeded on a
number of II-VI molecular clusters, depending on the III-V
material being grown and the feedstock precursors employed.
Preparation of InP nanoparticles (red emission): 200 mil
liliters (ml) of di-n-butylsebacate ester and 10 grams of
myristic acid at approximately 60°C. were placed in a round
bottomed three-neck flask and purged with N. Next, 0.94
grams of the ZnS cluster HNEtaZnS,(SPh) were
added to the flask. The flask was then heated to approximately
100° C. for 30 minutes. Next, 12 ml of 0.25M In(Ac).
(MA) (where Ac refers to acetate and MA refers to
myristate) was added over a period of 15 minutes using an
electronic Syringe pump at a rate of 48 ml per hour, followed
by the addition of 12 ml 0.25M (TMS)P at the same rate.
Once these additions were complete, the temperature of the
flask was increased to 180°C. To grow the particles up to the
required size (leading to the desired red emission), further
addition of In(Ac)(MA) and (TMS)P were made as

22
period, the temperature was decreased to 160° C. and the
reaction mixture was left to anneal for up to approximately 4
days (at a temperature approximately 20-40°C. below that of
the reaction). A UV lamp was also used at this stage to aid in
annealing.
The particles were isolated by the addition of dried
degassed methanol (approximately 200 ml) via cannula tech
niques. The precipitate was allowed to settle and then metha
nol was removed via cannula with the aid of a filter stick.
10

15

25

30

follows:

16 ml In(Ac)(MA) and 16 ml (TMS)P were added
followed by a temperature increase to 200° C.;
further additions of 10 ml of In(Ac)(MA) were made
and the temperature was maintained at approximately 200° C.

35

for 1 hour;

the temperature was then lowered to approximately 160°
C. and the reaction allowed to anneal at this temperature for
approximately 3 days.
Finally, the particles were isolated using acetonitrile, pre
cipitated from the reaction Solution, centrifuged, and col

40

lected.

Preparation of InP quantum dots with emission in the range
of 500-700 nm: Di-butyl ester (approximately 100 ml) and
myristic acid (approximately 10.06 grams) were placed in a
three-neck flask and degassed at approximately 70° C. under
vacuum for 1 hour. After this period, nitrogen was introduced
and the temperature increased to approximately 90° C.
Approximately 4.71 grams of the ZnS molecular cluster
EtNHZnoSa (SPh) was added, and the mixture was
stirred for approximately 45 minutes. The temperature was
then increased to approximately 100° C., followed by the
drop-wise additions of InCMA) (1M, 15 ml) followed by
(TMS)P (1M, 15 ml). The reaction mixture was stirred while
the temperature was increased to approximately 140°C. At
140°C., further drop-wise additions of InCMA) dissolved in
di-n-butylsebacate ester (1M, 35 ml) (left to stirfor 5 minutes)
and (TMS)P dissolved in di-n-butylsebacate ester (1M, 35
ml) were made. The temperature was then slowly increased to
180° C. and further drop-wise additions of InCMA), (1M, 55
ml) followed by (TMS)P (1M, 40 ml) were made. By addi
tion of the precursor in this manner, particles of InP with an
emission maximum gradually increasing from 500 nanom
eters (nm) to 720 nm were formed. The reaction was stopped
when the desired emission maximum was obtained and left to

stir at the reaction temperature for half an hour. After this

45

50

55

60

65

Dried degassed chloroform (approximately 10 ml) was added
to wash the solid. The solid was left to dry under vacuum for
1 day. This procedure resulted in the formation of InP nano
particles on ZnS molecular clusters.
Postoperative treatments: The quantum yields of the result
ing InP nanoparticles were further increased by washing in
dilute hydrofluoric acid (HF). The nanoparticles were dis
solved in anhydrous degassed chloroform (~270 ml). A 50 ml
portion was removed, placed in a plastic flask, and flushed
with nitrogen. Using a plastic syringe, the HF solution was
prepared by adding 3 ml of 60% w/w HF in water and adding
degassed THF (17 ml). The HF was added drop-wise over
approximately 5 hours to the InP dots. After addition of the
HF, the solution was left to stir overnight. Excess HF was
removed by extraction through calcium chloride solution (in
water) and drying the etched InP dots. The dried dots were
re-dispersed in 50 ml chloroform for future use. The emission
maximum was approximately 567 nm, and the particles had a
full width half maximum value (FWHM) of approximately 60
nm. The quantum efficiencies of the InP core material ranged
from approximately 25% to approximately 50%.
Growth of a ZnS shell: A 20 ml portion of the HF-etched
InP core particles was dried in a three-neck flask. 1.3 grams of
myristic acid and 20 ml di-n-butyl sebacate ester were added
and degassed for 30 minutes. The solution was heated to 200°
C., and 2 ml of 1M (TMS)S was added drop-wise (at a rate of
7.93 ml/hr). After this addition was complete, the solution
was left to stand for 2 minutes, and then 1.2 grams of anhy
drous zinc acetate was added. The solution was kept at 200°
C. for 1 hour and then cooled to room temperature. The
particles were isolated by adding 40 ml of anhydrous
degassed methanol and centrifuging. The Supernatant liquid
was discarded, and 30 ml of anhydrous degassed hexane was
added to the remaining solid. The solution was allowed to
settle for 5 hours and then centrifuged again. The Supernatant
liquid was collected and the remaining solid was discarded.
The emission maximum was approximately 535 nm, and the
particles had a FWHM of approximately 50-65 nm. The
quantum efficiencies of the InP core material ranged from
approximately 35% to approximately 90%.
It will be seen that the techniques described herein provide
a basis for improved production of nanoparticle materials.
The terms and expressions employed herein are used as terms
of description and not of limitation, and there is no intention
in the use of Such terms and expressions of excluding any
equivalents of the features shown and described or portions
thereof. Instead, it is recognized that various modifications
are possible within the scope of the invention claimed.
What is claimed is:

1. A nanoparticle comprising:
(i) a molecular cluster compound incorporating ions from
groups 12 and 16 of the periodic table, and
(ii) a core semiconductor material provided on said
molecular cluster compound,
wherein the core semiconductor material incorporates ions
from groups 13 and 15 of the periodic table.

US 7,588,828 B2
23
2. The nanoparticle of claim 1 wherein a crystal phase of
the molecular cluster compound and a crystal phase of the
core semiconductor material are compatible.
3. The nanoparticle of claim 1 wherein the molecular clus
ter compound incorporates Zinc ions.
4. The nanoparticle of claim 1 wherein the group 16 ions
comprise at least one member of the group consisting of oxide

24
10. The nanoparticle of claim 8 wherein said first semicon
ductor material incorporates ions from group 16 of the peri

ions, sulfide ions, selenide ions, and telluride ions.

ions, sulfide ions, selenide ions and telluride ions.

odic table.

11. The nanoparticle of claim 9 wherein the group 12 ions
comprise Zinc ions.
12. The nanoparticle of claim 9 wherein the group 16 ions
comprise at least one member of the group consisting of oxide

13. The nanoparticle of claim 8 further comprising a sec
5. The nanoparticle of claim 1 wherein the group 13 ions
comprise at least one member of the group consisting of 10 ond layer comprising a second semiconductor material pro
vided on said first layer.
aluminum ions, gallium ions, and indium ions.
14. A method of producing nanoparticles, the method com
6. The nanoparticle of claim 1 wherein the group 15 ions
comprise at least one member of the group consisting of prising the steps of:
providing a nanoparticle precursor composition compris
nitride ions, arsenide ions, and antimonide ions.
7. The nanoparticle of claim 1 wherein the nanoparticle 15
ing group 13 ions and group 15 ions; and
effecting conversion of the nanoparticle precursor into
exhibits a quantum efficiency ranging from about 20% to
about 60%.
nanoparticles,
8. The nanoparticle of claim 1 further comprising a first
wherein said conversion is effected in the presence of a
molecular cluster compound incorporating group 12
layer comprising a first semiconductor material provided on
said nanoparticle core.
ions and group 16 ions under conditions permitting
nanoparticle seeding and growth.
9. The nanoparticle of claim 8 wherein said first semicon
ductor material incorporates ions from group 12 of the peri
odic table.

k

k

k

k

k