Preparation of nanocrystallites

Details Preparation of nanocrystallites Preparation of nanocrystallites

2003-06-06

2004-11-23

Le, H. Thi (Department: 1773)

Single-crystal, oriented-crystal, and epitaxy growth processes;

Processes of growth with a subsequent step of heat treating...

C117S011000, C117S036000, C117S075000

Reexamination Certificate

active

06821337

ABSTRACT:

TECHNICAL FIELD
The invention relates to methods of manufacturing a nanocrystallite.
BACKGROUND
Nanocrystallites having small diameters can have properties intermediate between molecular and bulk forms of matter. For example, nanocrystallites based on semiconductor materials having small diameters can exhibit quantum confinement of both the electron and hole in all three dimensions, which leads to an increase in the effective band gap of the material with decreasing crystallite size. Consequently, both the optical absorption and emission of nanocrystallites shift to the blue (i.e., to higher energies) as the size of the crystallites decreases.
Methods of preparing monodisperse semiconductor nanocrystallites include pyrolysis of organometallic reagents, such as dimethyl cadmium, injected into a hot, coordinating solvent. This permits discrete nucleation and results in the controlled growth of macroscopic quantities of nanocrystallites. Organometallic reagents can be expensive, dangerous and difficult to handle.
SUMMARY
The invention features methods of manufacturing a nanocrystallite. The nanocrystallite has a diameter of less than 150 Å. The nanocrystallite can be a member of a population of nanocrystallites having a narrow size distribution. The nanocrystallite can be a sphere, rod, disk, or other shape. The nanocrystallite can include a core of a semiconductor material. The core can have an overcoating on a surface of the core. The overcoating can be a semiconductor material having a composition different from the composition of the core. Semiconducting nanocrystallites can photoluminesce and can have high emission quantum efficiencies. The method forms the nanocrystallite from an M-containing salt. The nanocrystallite can include a core having the formula MX, where M is cadmium, zinc, magnesium, mercury, aluminum, gallium, indium, thallium, or mixtures thereof, and X is oxygen, sulfur, selenium, tellurium, nitrogen, phosphorus, arsenic, antimony, or mixtures thereof. The M-containing salt can be the source of M in the nanocrystallite. An X-containing compound can be the source of the X in the nanocrystallite.
The M-containing salt can be a safe, inexpensive starting material for manufacturing a nanocrystallite relative to typical organometallic reagents which can be air sensitive, pyrophoric, or volatile. The M-containing salt is not air sensitive, is not pyrophoric, and is not volatile relative to organometallic reagents.
In one aspect, the invention features a method of manufacturing a nanocrystallite. The method includes contacting a metal, M, or an M-containing salt, and a reducing agent to form an M-containing precursor, M being Cd, Zn, Mg, Hg, Al, Ga, In or Tl. The M-containing precursor is contacted with an X donor, X being O, S, Se, Te, N, P, As, or Sb. The mixture is then heated in the presence of an amine to form the nanocrystallite. In certain embodiments, heating can take place in the presence of a coordinating solvent.
In another aspect, the invention features a method of manufacturing a nanocrystallite including contacting a metal, M, or an M-containing salt, and a reducing agent to form an M-containing precursor, contacting the M-containing precursor with an X donor, and heating the mixture to form the nanocrystallite. In certain embodiments, heating can take place in the presence of a coordinating solvent.
In another aspect, the invention features a method of manufacturing a nanocrystallite including contacting a metal, M, or an M-containing salt, an amine, and an X donor, and heating the mixture to form the nanocrystallite.
In yet another aspect, the invention features a method of overcoating a core nanocrystallite. The method includes contacting a core nanocrystallite population with an M-containing salt, an X donor, and an amine, and forming an overcoating having the formula MX on a surface of the core. In certain embodiments, a coordinating solvent can be present.
The amine can be a primary amine, for example, a C
8
-C
20
alkyl amine. The reducing agent can be a mild reducing agent capable of reducing the M of the M-containing salt. Suitable reducing agents include a 1,2-diol or an aldehyde. The 1,2-diol can be a C
6
-C
20
alkyl diol. The aldehyde can be a C
6
-C
20
aldehyde.
The M-containing salt can include a halide, carboxylate, carbonate, hydroxide, or diketonate. The X donor can include a phosphine chalcogenide, a bis(silyl) chalcogenide, dioxygen, an ammonium salt, or a tris(silyl) pnictide.
The nanocrystallite can photoluminesce with a quantum efficiency of at least 10%, preferably at least 20%, and more preferably at least 40%. The nanocrystallite can have a particle size (e.g., average diameter when the nanocrystallite is spheroidal) in the range of about 20 Å to about 125 Å. The nanocrystallite can be a member of a substantially monodisperse core population. The population can emit light in a spectral range of no greater than about 75 nm at full width at half max (FWHM), preferably 60 nm FWHM, more preferably 40 nm FWHM, and most preferably 30 nm FWHM. The population can exhibit less than a 15% rms deviation in diameter of the nanocrystallites, preferably less than 10%, more preferably less than 5%.
The method can include monitoring the size distribution of a population including of the nanocrystallite, lowering the temperature of the mixture in response to a spreading of the size distribution, or increasing the temperature of the mixture in response to when monitoring indicates growth appears to stop. The method can also include exposing the nanocrystallite to a compound having affinity for a surface of the nanocrystallite.
The method can include forming an overcoating of a semiconductor material on a surface of the nanocrystallite. The semiconductor material can be a group II-VI, III-V or IV semiconductor, such as, for example, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, or mixtures thereof.
The details of one or more embodiments of the invention are set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.


REFERENCES:
patent: 5147841 (1992-09-01), Wilcoxon
patent: 5262357 (1993-11-01), Alivisatos et al.
patent: 5354707 (1994-10-01), Chapple-Sokol et al.
patent: 5505928 (1996-04-01), Alivisatos et al.
patent: 5525377 (1996-06-01), Gallagher et al.
patent: 5537000 (1996-07-01), Alivisatos et al.
patent: 5985353 (1999-11-01), Lawton et al.
patent: 5990479 (1999-11-01), Weiss et al.
patent: 6114038 (2000-09-01), Castro et al.
patent: 6179912 (2001-01-01), Barbera-Guillem et al.
patent: 6207229 (2001-03-01), Bawendi et al.
patent: 6224739 (2001-05-01), Reetz et al.
patent: 6262129 (2001-07-01), Murray et al.
patent: 6379635 (2002-04-01), O'Brien et al.
patent: 6576291 (2003-06-01), Bawendi et al.
patent: 2002/0066401 (2002-06-01), Peng et al.
patent: WO98/19963 (1998-05-01), None
patent: WO99/26299 (1999-05-01), None
patent: WO00/17103 (2000-03-01), None
patent: WO00/17642 (2000-03-01), None
patent: WO00/17655 (2000-03-01), None
patent: WO00/17656 (2000-03-01), None
patent: WO01/07689 (2001-02-01), None
C. Yang et al, “Growth of CdS Nanorods in Nonionic Amphiphilic Triblock Copolymer Systems”, Chem. Mater, 14, 1277-1284 (2002).*
S. L. Cumberland et al, “Inorganic Clusters as Single-Source Precursors for Preparation of CdSe, ZnSe, and CdSe/ZnS Nanomaterials”, Chem. Mater, 14, 1576-1584 (2002).*
Mokari and Banin, “Synthesis and Properties of CdSe/ZnS Core/Shell Nanorods”, Institute of Chemistry, The Hebrew University of Jerusalem, (2003).*
S. D. Bunge et al., “Growth and Morphology of Cadminum Chalcogenides: the Synthesis of Nanorods. Tetrapods, and Spheres from CdO and Cd(O2CCH3)2”, J. Mater. Chem., 13, 1705-1709 (2003).*
A.P. Alivisatos, “Perspectives on the Physical Chemistry of Semiconductor Nanocrystals,” J. Phys. Chem. 100:13226-13239 (1996).
A.P. Alvisatos, “Semiconductor Clusters, Nanocryst

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