Patent Application
20170130127
The present invention relates to the technical field of nanotechnology, and more particularly to semiconductor nanocrystals and methods for preparing same.
In accordance with one aspect of the present invention, there is provided a method for preparing semiconductor nanocrystals comprising contacting an M-precursor compound with an X donor, wherein the X donor is represented by the formula (I):
X(Y(R)3)3 (I)
where X is a group V element; Y is Ge, Sn, or Pb; and each R, independently, is alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl, wherein each R, independently, is optionally substituted by 1 to 6 substituents independently selected from hydrogen, halo, hydroxy, nitro, cyano, amino, alkyl, cycloalkyl, cycloalkenyl, alkoxy, acyl, thio, thioalkyl, alkenyl, alkynyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl at a first temperature to form a reaction mixture; and
heating the reaction mixture at a second temperature for at least an hour, wherein the second temperature is the same as or different from the first temperature.
The compound of formula (I) can be tris(trimethylgermyl)nitride; tris(trimethylstannyl)nitride; tris(trimethylplumbyl)nitride; tris(trimethylgermyl)phosphide; tris(trimethylstannyl) phosphide; tris(trimethylplumbyl) phosphide; tris(trimethylgermyl)arsine; tris(trimethylstannyl)arsine; tris(trimethylplumbyl)arsine; tris(trimethylgermyl)stibine; tris(trimethylstannyl)stibine; or tris(trimethylplumbyl)stibine.
In certain embodiments, X can be As. Y can be Ge. Each R, independently, can be alkyl, cycloalkyl, or aryl. Each R, independently, can be unsubstituted alkyl, unsubstituted cycloalkyl, or unsubstituted aryl.
In certain embodiments, M included in the M-precursor includes can be a group III element. M can be In.
In accordance with another aspect of the present invention, there is provided a method for preparing a semiconductor nanocrystal including a core comprising a Group III element and a Group V element and a shell over at least a portion of the core, the method comprising: contacting an M-precursor compound with an X donor, wherein the X donor is represented by the formula (I):
X(Y(R)3)3 (I)
in a reaction mixture, where X is a group V element; Y is Ge, Sn, or Pb; and each R, independently, is alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl, wherein each R, independently, is optionally substituted by 1 to 6 substituents independently selected from hydrogen, halo, hydroxy, nitro, cyano, amino, alkyl, cycloalkyl, cycloalkenyl, alkoxy, acyl, thio, thioalkyl, alkenyl, alkynyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl at a first temperature to form a reaction mixture; and
heating the reaction mixture at a second temperature for at least an hour, wherein the second temperature is the same as or different from the first temperature;
isolating cores from the reaction mixture after heating; and
forming at least a first shell over at least a portion of the isolated cores, the shell comprising a semiconductor material.
The compound of formula (I) can be tris(trimethylgermyl)nitride; tris(trimethylstannyl)nitride; tris(trimethylplumbyl)nitride; tris(trimethylgermyl)phosphide; tris(trimethylstannyl) phosphide; tris(trimethylplumbyl) phosphide; tris(trimethylgermyl)arsine; tris(trimethylstannyl)arsine; tris(trimethylplumbyl)arsine; tris(trimethylgermyl)stibine; tris(trimethylstannyl)stibine; or tris(trimethylplumbyl)stibine.
In certain embodiments, X can be As. Y can be Ge. Each R, independently, can be alkyl, cycloalkyl, or aryl. Each R, independently, can be unsubstituted alkyl, unsubstituted cycloalkyl, or unsubstituted aryl.
In certain embodiments, M included in the M-precursor includes can be a group III element. M can be In.
In certain embodiments, the semiconductor material can be a Group II-VI semiconductor. Examples of a Group II-VI semiconductor include, but are not limited to, CdSe, ZnSe, etc. In certain embodiments, ZnSe can be preferred.
In certain embodiments, the method can further comprise forming a second shell over the first shell. The second shell can comprise a semiconductor material. In certain embodiments, a Group II-VI semiconductor can be preferred.
In accordance with another aspect of the present invention, there is provided a method for preparing a semiconductor nanocrystal including a core comprising a Group III element and a Group V element and a shell over at least a portion of the core, the method comprising: contacting an M-precursor compound with an X donor, wherein the X donor is represented by the formula (I):
X(Y(R)3)3 (I)
in a reaction mixture, where X is a group V element; Y is Ge, Sn, or Pb; and each R, independently, is alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl, wherein each R, independently, is optionally substituted by 1 to 6 substituents independently selected from hydrogen, halo, hydroxy, nitro, cyano, amino, alkyl, cycloalkyl, cycloalkenyl, alkoxy, acyl, thio, thioalkyl, alkenyl, alkynyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl at a first temperature to form a reaction mixture;
heating the reaction mixture at a second temperature for at least an hour, wherein the second temperature is the same as or different from the first temperature; and
forming at least a first shell over at least a portion of the cores in the reaction mixture, the shell comprising a semiconductor material.
The compound of formula (I) can be tris(trimethylgermyl)nitride; tris(trimethylstannyl)nitride; tris(trimethylplumbyl)nitride; tris(trimethylgermyl)phosphide; tris(trimethylstannyl) phosphide; tris(trimethylplumbyl) phosphide; tris(trimethylgermyl)arsine; tris(trimethylstannyl)arsine; tris(trimethylplumbyl)arsine; tris(trimethylgermyl)stibine; tris(trimethylstannyl)stibine; or tris (trimethylplumbyl) stibine.
In certain embodiments, X can be As. Y can be Ge. Each R, independently, can be alkyl, cycloalkyl, or aryl. Each R, independently, can be unsubstituted alkyl, unsubstituted cycloalkyl, or unsubstituted aryl.
In certain embodiments, M included in the M-precursor includes can be a group III element. M can be In.
In certain embodiments, the semiconductor material can be a Group II-VI semiconductor. Examples of a Group II-VI semiconductor include, but are not limited to, CdSe, ZnSe, etc. In certain embodiments, ZnSe can be preferred.
In certain embodiments, the method can further comprise forming a second shell over the first shell. The second shell can comprise a semiconductor material. In certain embodiments, a Group II-VI semiconductor can be preferred.
In accordance with another aspect of the present invention, there is provided a semiconductor nanocrystal including a core comprising indium arsenide, a first shell comprising zinc selenide, and a second shell comprising a second semiconductor material.
In certain embodiments, the second shell comprises a Group II-VI semiconductor.
In certain embodiments, the second shell comprises cadmium, zinc, and selenium.
The foregoing, and other aspects described herein, all constitute embodiments of the present invention.
It should be appreciated by those persons having ordinary skill in the art(s) to which the present invention relates that any of the features described herein in respect of any particular aspect and/or embodiment of the present invention can be combined with one or more of any of the other features of any other aspects and/or embodiments of the present invention described herein, with modifications as appropriate to ensure compatibility of the combinations. Such combinations are considered to be part of the present invention contemplated by this disclosure.
Additional information concerning the foregoing, and other information useful with the present inventions is provided below.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. Other embodiments will be apparent to those skilled in the art from consideration of the description and drawings, from the claims, and from practice of the invention disclosed herein.
In the drawings,
For a better understanding of the present invention, together with other advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.
Various aspects and embodiments of the present inventions will be further described in the following detailed description.
The present invention relates to methods for preparing semiconductor nanocrystals. The present invention further relates to semiconductor nanocrystals.
Semiconductor nanocrystals have size-dependent optical and electronic properties. In particular, the band gap energy of a semiconductor nanocrystal of a particular semiconductor material varies with the diameter of the crystal. Generally, a semiconductor nanocrystal is a member of a population of nanocrystals having a distribution of sizes. When the distribution is centered about a single value and narrow, the population can be described as monodisperse. Monodisperse particles can, for example, have at least 60% of the particles fall within a specified particle size range.
Semiconductor nanocrystals can be a sphere, rod, disk, or other shape.
Semiconductor nanocrystals demonstrate quantum confinement effects in their luminescent properties. A semiconductor nanocrystal is capable of emitting light upon excitation. A semiconductor nanocrystal can be excited by irradiation with an excitation wavelength of light, by electrical excitation, or by other energy transfer.
The emission from a semiconductor nanocrystal can be a narrow Gaussian emission band that can be tuned through the complete wavelength range of the ultraviolet, visible, or infra-red regions of the spectrum by varying the size of the semiconductor nanocrystal, the composition of the semiconductor nanocrystal, or both.
In certain embodiments, the semiconductor nanocrystals of the invention comprise semiconductor nanocrystals that are capable of emitting light with a peak emission wavelength in a range from about 800 nm to about 2 microns upon excitation.
Photoluminescence quantum efficiency (also referred to as quantum efficiency, quantum yield or solution quantum yield) represents the percent of absorbed photons that are reemitted as photons upon excitation by irradiation with an excitation wavelength of light.
A nanocrystal is a nanometer sized particle, e.g., in the size range of up to about 1000 nm In certain embodiments, a nanocrystal can have a size in the range of up to about 100 nm In certain embodiments, a nanocrystal can have a size in the range up to about 20 nm (such as about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nm). In certain embodiments, a nanocrystal can have a size less than 100 Å.
In accordance with one aspect of the present invention, there is provided a method for preparing semiconductor nanocrystals comprising contacting an M-precursor compound with an X donor, wherein the X donor is represented by the formula (I):
X(Y(R)3)3 (I)
where X is a group V element; Y is Ge, Sn, or Pb; and each R, independently, is alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl, wherein each R, independently, is optionally substituted by 1 to 6 substituents independently selected from hydrogen, halo, hydroxy, nitro, cyano, amino, alkyl, cycloalkyl, cycloalkenyl, alkoxy, acyl, thio, thioalkyl, alkenyl, alkynyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl at a first temperature to form a reaction mixture; and
heating the reaction mixture at a second temperature for at least an hour, wherein the second temperature is the same as or different from the first temperature.
The compound of formula (I) can be tris(trimethylgermyl)nitride; tris(trimethylstannyl)nitride; tris(trimethylplumbyl)nitride; tris(trimethylgermyl)phosphide; tris(trimethylstannyl) phosphide; tris(trimethylplumbyl) phosphide; tris(trimethylgermyl)arsine; tris(trimethylstannyl)arsine; tris(trimethylplumbyl)arsine; tris(trimethylgermyl)stibine; tris(trimethylstannyl)stibine; or tris(trimethylplumbyl)stibine.
Group V (also referred to herein as Group VA) elements include, for example, nitrogen, phosphorus, arsenic, antimony, and bismuth.
In certain embodiments, X can be As. Y can be Ge. Each R, independently, can be alkyl, cycloalkyl, or aryl. Each R, independently, can be unsubstituted alkyl, unsubstituted cycloalkyl, or unsubstituted aryl.
An X donor can further be included in a solvent before being contacted with an M-precursor. In certain embodiments, a solvent can comprise a coordinating solvent or a weakly coordinating solvent. In certain embodiments, a solvent comprises a non-coordinating solvent. A solvent can also comprise a mixture of solvents
In certain preferred embodiments, M included in the M-precursor includes can be a group III element. In certain embodiments, an M-precursor wherein M includes indium can be more preferred.
Examples of M-precursors include, for example, elements, covalent compounds, ionic compounds, and/or coordination complexes, that serve as a source for the desired metal element(s) in the resulting nanocrystal. For example, a metal precursor can constitute a wide range of substances, including, but not limited to, a metal oxide, a metal carbonate, a metal bicarbonate, a metal sulfate, a metal sulfite, a metal phosphate, metal phosphite, a metal halide, a metal carboxylate, a metal alkoxide, a metal thiolate, a metal amide, a metal imide, a metal alkyl, a metal aryl, other organometallics, a metal coordination complex, a metal solvate, and the like. For example, non-limiting examples of indium precursors include In(III) acetate, In(III) trifluoroacetate, trialkyl indium (InR3)(wherein R=methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, tert-butyl, etc.); non-limiting examples of gallium precursors include Ga(III) acetate, Ga(III) trifluoroacetate, trialkyl gallium (InR3)(wherein R=methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, tert-butyl, etc.). Other Group III metal precursors can be readily ascertained by one of ordinary skill in the art.
An M-precursor can further be included in a solvent before being contacted with an X donor. In certain embodiments, a solvent can comprise a coordinating solvent or a weakly coordinating solvent. In certain embodiments, a solvent comprises a non-coordinating solvent. A solvent can also comprise a mixture of solvents
In certain embodiments, the reaction mixture can further include one or more additional solvents.
Examples of solvents include, but are not limited to, octadecene, squalene, methyl myristate, octyl octanoate, hexyl octanoate, and CH3(CH2)nC(O)O(CH2)mCH3 wherein n=4-18 and m=1-8, dioctyl ether, and diphenyl ether, and mixtures of one or more solvents. In certain embodiments, a mixture can comprise a mixture, (including but not limited to a eutectic mixture) of biphenyl and diphenyl oxide, including, e.g., DOWTHERM A, available from the Dow Chemical Company. Other high boiling point ethers (e.g., BP>˜200° C.) may also be used. Such ethers (coordinating) can be aromatic ethers, aliphatic ethers or aromatic aliphatic ethers. Examples of additional ethers include, but are not limited to, dihexyl ether, diethyleneglycol dimethyl ether, diethyleneglycol dibutyl ether, triethyleneglycol dimethyl ether, tetraethyleneglycol dimethyl ether, butyl phenyl ether, benzyl phenyl ether, dibenzyl ether, ditolyl ether and isomers thereof. Mixtures of two or more solvents can also be used. Other coordinating solvents can be readily ascertained by one of ordinary skill in the art.
Examples of other non-coordinating solvents that may be useful include, but are not limited to, squalane, octadecane, or any other saturated hydrocarbon molecule. Mixtures of two or more solvents can also be used.
Other solvents for use in the methods taught herein can be readily ascertained by one of ordinary skill in the art.
In certain embodiments, the first temperature is less than 300° C. For example, the first temperature can be in a range from about 80° C. to about 285° C. Other temperatures may be determined to be useful or desirable.
The second temperature can be the same as the first temperature or different. In certain embodiments, for example, the second temperature can be in a range from about 260° C. to about 285° C. Other temperatures may be determined to be useful or desirable.
In certain embodiment, heating at the second temperature can be carried out for up to 2 hours, up to 2.5, hours, up to 3 hours, up to 3.5 hours. Other times within these ranges or outside of these ranges may also be useful.
In accordance with another aspect of the present invention, there is provided a method for preparing a semiconductor nanocrystal including a core comprising a Group III element and a Group V element and a shell over at least a portion of the core, the method comprising: contacting an M-precursor compound with an X donor, wherein the X donor is represented by the formula (I):
X(Y(R)3)3 (I)
in a reaction mixture, where X is a group V element; Y is Ge, Sn, or Pb; and each R, independently, is alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl, wherein each R, independently, is optionally substituted by 1 to 6 substituents independently selected from hydrogen, halo, hydroxy, nitro, cyano, amino, alkyl, cycloalkyl, cycloalkenyl, alkoxy, acyl, thio, thioalkyl, alkenyl, alkynyl, cycloalkenyl, heterocyclyl, aryl, or heteroaryl at a first temperature to form a reaction mixture; and
heating the reaction mixture at a second temperature for at least an hour, wherein the second temperature is the same as or different from the first temperature; and
forming at least a first shell over at least a portion of the cores, the shell comprising a semiconductor material.
In certain embodiments, isolating the cores from the growth medium can be preferred before the step of forming the first shell.
Isolating the cores from the growth medium is particularly preferred before forming a first shell comprising cadmium selenide over an indium arsenide core prepared using tris(trimethylgermyl)arsine as the X-donor.
The compound of formula (I) can be tris(trimethylgermyl)nitride; tris(trimethylstannyl)nitride; tris(trimethylplumbyl)nitride; tris(trimethylgermyl)phosphide; tris(trimethylstannyl)phosphide; tris(trimethylplumbyl)phosphide; tris(trimethylgermyl)arsine; tris(trimethylstannyl)arsine; tris(trimethylplumbyl)arsine; tris(trimethylgermyl)stibine; tris(trimethylstannyl)stibine; or tris(trimethylplumbyl)stibine.
Group V (also referred to herein as Group VA) elements include, for example, nitrogen, phosphorus, arsenic, antimony, and bismuth.
In certain embodiments, X can be As. Y can be Ge. Each R, independently, can be alkyl, cycloalkyl, or aryl. Each R, independently, can be unsubstituted alkyl, unsubstituted cycloalkyl, or unsubstituted aryl.
An X donor can further be included in a solvent before being contacted with an M-precursor. In certain embodiments, a solvent can comprise a coordinating solvent or a weakly coordinating solvent. In certain embodiments, a solvent comprises a non-coordinating solvent. A solvent can also comprise a mixture of solvents
In certain preferred embodiments, M included in the M-precursor includes can be a group III element. In certain embodiments, an M-precursor wherein M includes indium can be more preferred.
Examples of M-precursors include, for example, elements, covalent compounds, ionic compounds, and/or coordination complexes, that serve as a source for the desired metal element(s) in the resulting nanocrystal. For example, a metal precursor can constitute a wide range of substances, including, but not limited to, a metal oxide, a metal carbonate, a metal bicarbonate, a metal sulfate, a metal sulfite, a metal phosphate, metal phosphite, a metal halide, a metal carboxylate, a metal alkoxide, a metal thiolate, a metal amide, a metal imide, a metal alkyl, a metal aryl, other organometallics, a metal coordination complex, a metal solvate, and the like. For example, non-limiting examples of indium precursors include In(III) acetate, In(III) trifluoroacetate, trialkyl indium (InR3)(wherein R=methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, tert-butyl, etc.); non-limiting examples of gallium precursors include Ga(III) acetate, Ga(III) trifluoroacetate, trialkyl gallium (InR3)(wherein R=methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, tert-butyl, etc.). Other Group III metal precursors can be readily ascertained by one of ordinary skill in the art.
An M-precursor can further be included in a solvent before being contacted with an X donor. In certain embodiments, a solvent can comprise a coordinating solvent or a weakly coordinating solvent. In certain embodiments, a solvent comprises a non-coordinating solvent. A solvent can also comprise a mixture of solvents.
In certain embodiments, the reaction mixture can further include one or more additional solvents.
Examples of solvents include, but are not limited to, octadecene, squalene, methyl myristate, octyl octanoate, hexyl octanoate, and CH3(CH2)nC(O)O(CH2)mCH3 wherein n=4-18 and m=1-8, dioctyl ether, and diphenyl ether, and mixtures of one or more solvents. In certain embodiments, a mixture can comprise a mixture, (including but not limited to a eutectic mixture) of biphenyl and diphenyl oxide, including, e.g., DOWTHERM A, available from the Dow Chemical Company. Other high boiling point ethers (e.g., BP >˜200° C.) may also be used. Such ethers (coordinating) can be aromatic ethers, aliphatic ethers or aromatic aliphatic ethers. Examples of additional ethers include, but are not limited to, dihexyl ether, diethyleneglycol dimethyl ether, diethyleneglycol dibutyl ether, triethyleneglycol dimethyl ether, tetraethyleneglycol dimethyl ether, butyl phenyl ether, benzyl phenyl ether, dibenzyl ether, ditolyl ether and isomers thereof. Mixtures of two or more solvents can also be used. Other coordinating solvents can be readily ascertained by one of ordinary skill in the art.
Examples of other non-coordinating solvents that may be useful include, but are not limited to, squalane, octadecane, or any other saturated hydrocarbon molecule. Mixtures of two or more solvents can also be used.
Other solvents for use in the methods taught herein can be readily ascertained by one of ordinary skill in the art.
In certain embodiments, the first temperature is less than 300° C. For example, the first temperature can be in a range from about 80° C. to about 285° C. Other temperatures may be determined to be useful or desirable.
The second temperature can be the same as the first temperature or different. In certain embodiments, for example, the second temperature can be in a range from about 260° C. to about 285° C. Other temperatures may be determined to be useful or desirable.
In certain embodiment, heating at the second temperature can be carried out for up to 2 hours, up to 2.5, hours, up to 3 hours, up to 3.5 hours. Other times within these ranges or outside of these ranges may also be useful.
A semiconductor material included in a shell can comprise an element, for example, a Group IVA element. A semiconductor material included in the shell can comprise a compound represented by the formula MX. In certain examples M comprises, for example, one or more elements from Group IA element (for example, lithium, sodium, rubidium, and cesium), Group IIA (for example, beryllium, magnesium, calcium, strontium, and barium), Group IIB (for example, Zn, Cd, and Hg), Group IIIA (for example, Al, Ga, In and Tl), Group IVA (for example, Si, Ge, Sn, and Pb), and/or the transition metals (for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Co, Ni, Pd, Pt, Rh, and the like). (See, F. A. Cotton et al., Advanced Inorganic Chemistry, 6th Edition, (1999). In certain examples, X comprises one or more elements from Group VA (for example, nitrogen, phosphorus, arsenic, antimony, and bismuth) and/or Group VIA (for example, oxygen, sulfur, selenium, and tellurium). In certain embodiments, a semiconductor material included in the shell comprises a binary (including two elements) material, a ternary (including three elements) material, a quaternary (including four elements) material, etc. In certain embodiments, the material can comprise an alloy and/or a mixture.
Non-limiting examples of a binary semiconductor material that can be included in a shell include ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe (IIB-VIA materials), PbS, PbSe, PbTe (IVA-VIA materials), AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb (IIIA-VA materials). Non-limiting examples of ternary semiconductor materials that can be included in the shell include AxByC wherein A may comprise a Group IIB, IIIA or IVA element, B may comprise a group IIB, IIIA, or IVA element, and C may comprise a group VA or VIA element, and x and y are molar fractions between 0 and 1. Preferably x+y=1.
In certain preferred embodiments, the semiconductor material included in the first shell comprises a Group II-VI semiconductor. Examples of a Group II-VI semiconductor include, but are not limited to, CdSe, ZnSe, etc. In certain embodiments, ZnSe can be more preferred.
In certain embodiments, the method can further comprise forming a second shell over the first shell. The second shell can comprise a semiconductor material. In certain embodiments, a Group II-VI semiconductor can be preferred. In certain embodiments, CdZnS can be more preferred.
Shells can be formed on semiconductor nanocrystals by introducing shell precursors at a temperature where material adds to the surface of existing nanocrystals.
Shell thickness can be varied by growing a desired thickness of the shell. For example, the shell can have a thickness less than about one monolayer, about one monolayer, or more than about one monolayer. Preferably, the thickness is less than that at which quantum confinement is not achieved. The thickness is selected to achieve the predetermined characteristics of the core/shell nanocrystal. In certain embodiments, the thickness is in the range from greater than about 0 to about 20 monolayers. In certain embodiments, the thickness is in the range from greater than about 0 to about 10 monolayers. In certain embodiments, the thickness is in the range from greater than about 0 to about 5 monolayers. In certain embodiments, the thickness is in the range from about 1 to about 5 monolayers. In certain embodiments, the thickness is in the range from about 3 to about 5 monolayers. In certain embodiments, more than 20 monolayers can be grown. The actual monolayer thickness is dependent upon the size and composition of the molecules included in the shell.
In preparing a shell, use of a coordinating solvent can be desirable. A coordinating solvent is a compound having at least one donor site (e.g., a lone electron pair) that, for example, is available to coordinate to a surface of the growing nanocrystal. Solvent coordination can stabilize the growing nanocrystal. Examples of coordinating solvents include alkyl phosphines, alkyl phosphine oxides, alkyl phosphonic acids, or alkyl phosphinic acids, however, other coordinating solvents, such as pyridines, furans, and amines may also be suitable for the nanocrystal production. More specific examples of suitable coordinating solvents include pyridine, tri-n-octyl phosphine (TOP), tri-n-octyl phosphine oxide (TOPO) and trishydroxylpropylphosphine (tHPP). Technical grade TOPO can be used. Alternatively, a non-coordinating solvent could be used. Examples of non-coordinating solvents include saturated hydrocarbons; other examples are provided elsewhere herein.
The present invention will be further clarified by the following non-limiting examples, which are intended to be exemplary of the present invention.
Three different methods for preparing an indium arsenide semiconductor nanocrystal are described below.
In each of the following three methods, tris(trimethylgermyl) arsine is used as the X-donor. Method A:
Each of the above three methods was also carried out, but substituting an equal molar quantity of tris (trimethylsilyl) arsine, for the tris (trimethylgermyl)arsine.
Table 1 below shows a comparison of first exciton absorption for InAs cores synthesized by above three methods with either TMS-As or TMGe-As as the X-donor.
When an InAs core made with use of tris (trimethylgermyl) arsine as the X-donor was overcoated with a CdSe first shell in situ in the growth medium (e.g., without being isolated from the growth medium before the coating step), no first exciton absorption feature could be detected in the final InAs/CdSe/CdZnS core/shell/shell material.
However, with use of a ZnSe first shell on isolated InAs core made with use of tris (trimethylgermyl) arsine as the X-donor, the absorption features were maintained. See
Further, as the thickness of the ZnSe primary shell is increased, the first exciton peaks become more well-defined and undergo less of a redshift. See, for example,
Example core/shell/shall procedure beginning with an isolated core:
Primary Shell:
Secondary Shell, 2 syringes:
Purification: Split the reaction solution into 2 centrifuge tubes, and fill to the 45 mL line with 5:1 butanol:methanol (BuOH:MeOH) to induce precipitation. Vortex to mix, then spin at max (4200 rpm) for 3 minutes. Discard supernatant and redisperse cores in 2 mL of hexane per tube. Fill again to the 45 mL line with 5:1 BuOH:MeOH to induce precipitation. Discard supernatant and redisperse cores in 5mL of hexanes. Filter through black and red filters.
InAs cores made with use of tris (trimethylsilyl) arsine (TMS-As) as the X-donor and overcoated in situ with CdSe and CdZnS maintained well-defined and relatively narrow first exciton absorption features. As discussed above, when an InAs core made with use of tris (trimethylgermyl) arsine as the X-donor was overcoated with a CdSe and CdZnS in situ, no first exciton absorption feature could be detected in the final InAs/CdSe/CdZnS core/shell/shell material.
When the core is isolated and purified before overcoating, the absorption features were maintained and the overall performance of the QD material was enhanced (See
When the CdSe shell is replaced by a ZnSe primary shell, the trend is also seen but is less pronounced. See
Example core purification procedure:
Syringe 1:
In accordance with another aspect of the present invention, there is provided a semiconductor nanocrystal including a core comprising indium arsenide, a first shell comprising zinc selenide, and a second shell comprising a second semiconductor material.
In certain embodiments, the second shell comprises a Group II-VI semiconductor.
In certain embodiments, the second shell comprises cadmium, zinc, and selenium.
Semiconductor nanocrystals typically have ligands attached thereto. Ligands can be derived from a coordinating solvent that may be included in the reaction mixture during the growth process. Ligands can also be added to the reaction mixture. Ligands can also be derived from a reagent or precursor including in the reaction mixture for preparing or overcoating the semiconductor nanocrystals. In certain embodiments, more than one type of ligand can be attached to an outer surface of a nanocrystal.
Additional information that may be useful with the present invention is included in International Publication No. WO/2013/040365 of MIT, for “Highly Luminescent Semiconductor Nanocrystals”, published 21 Mar. 2013; International Application No. PCT/US2009/004345, of Breen, et al for “Nanoparticle Including Multi-Functional Ligand And Method”, filed 28 Jul. 2009, International Application No. PCT/US2007/024320, of Clough, et al.,for “Nanocrystals Including A Group III A Element And A Group V A Element, Method, Composition, Device And Other Products”, filed 21 Nov. 2007, International Publication No. WO 2012/099653 of QD vision, Inc., for “Semiconductor Nanocrystals And Methods Of Preparation” published 26 Jul. 2012; International Publication No. WO 2013/173409 A1 of QD Vision, Inc. for “Semiconductor Nanocrystals And Methods Of Preparation”, published 21 Nov. 2013; International Application No. PCT/US2007/13152 of Coe-Sullivan, et al., for “Light-Emitting Devices and Displays With Improved Performance”, filed 4 Jun. 2007; and U.S. Ser. No. 12/283,609 of Coe-Sullivan, et al. for “Compositions, Optical Component, System Including An Optical Component, Devices, And Other Products”, filed 12 Sep. 2008. The disclosures of each of the foregoing applications are hereby incorporated herein by reference in their entireties.
As used herein, the singular forms “a”, “an” and “the” include plural unless the context clearly dictates otherwise. Thus, for example, reference to an emissive material includes reference to one or more of such materials.
The entire contents of all patent publications and other publications cited in this disclosure are hereby incorporated herein by reference in their entirety. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.
Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein. It is intended that the present specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims and equivalents thereof.
This application claims priority to U.S. Provisional Patent Application No. 62/202,784, filed 7 Aug. 2015, which is hereby incorporated herein by reference in its entirety for all purposes.
This invention was made with Government support under Contract No. H92222-12-C-0002 awarded by the US Special Operations Command (USSOCOM). The Government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62202784 | Aug 2015 | US |
