JP2003073126A - Method for producing semiconductive nano-particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a semiconductive nano-particle having high crystallinity and excellent dispersibility in an organic matrix, obtainable advantageously by using inexpensive salts of excellent in chemical stability as raw materials. SOLUTION: This method comprises the steps of a first step for forming a hydrosol containing a semiconductive nano-crystal and/or a precursor thereof, and a second step for bringing the hydrosol into contact with an organic phase containing an oil-soluble surface-modifying molecule having bondability to the semiconductive nano-crystal and/or a precursor thereof to extract the semiconductive nano-crystal and/or a precursor thereof into the organic phase.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing semiconductor nanoparticles. More specifically, the present invention relates to an advantageous method for producing semiconductor nanoparticles mainly composed of semiconductor nanoparticles. Since the semiconductor nanoparticles obtained by the production method of the present invention have optical properties such as light absorption and emission characteristics and a high refractive index, they are used as a raw material of a component material of an optical device such as a projector or a display or an optical coating material.

[0002]

2. Description of the Related Art Conventional methods for producing semiconductor nanocrystals are roughly classified into a vapor phase method and a liquid phase method. Among them, the gas-phase method is a method capable of industrially producing semiconductor nanocrystals by a gas-phase reaction (for example, thermal decomposition oxidation) of semiconductor raw materials. It had the drawback that it was usually unavoidable. On the other hand, the following three methods are illustrated as conventional liquid phase methods. (1) A method of allowing a raw material aqueous solution to exist as a reverse micelle in a non-polar organic solvent and growing crystals in the reverse micelle phase (hereinafter referred to as "reverse micelle method"). S. Zo
u et al; Int. J. Quant. Chem. , 72 volumes,
439 (1999). Although relatively inexpensive salt can be used as a raw material, the crystallinity of semiconductor nanocrystals is insufficient because it is usually performed at a relatively low temperature that does not exceed the boiling point of water, resulting in product absorption and emission characteristics and high refractive index properties. Such characteristics were not always satisfactory. Also,
In some cases, the surfactant necessary for stabilizing the reverse micelles remained on the surface of the product particles, and the thermal stability and dispersibility were reduced. (2) A method (hereinafter referred to as “sol generation method”) in which a semiconductor nanocrystal or a precursor thereof is generated in a protic solvent such as water or ethanol to give a sol using an acid-base reaction as a driving force is known. For example, a synthesis example of titanium oxide nanocrystal hydrosol is Seijiro Ito et al .;
No. 305-308 (1984), a synthesis example of ethanol sol of zinc oxide nanocrystals is described in L. et al. Spanhel et al .;
J. Am. Chem. Soc. , 113, 2826 (1991). In the former case, in particular, by adding a surfactant (sodium dodecylbenzene sulfonate) to the hydrosol of titanium oxide nanocrystals and coating the surface of the particles with this, the secondary agglutination is suppressed while making the particles hydrophobic, and the organic solvent dispersibility Is given. However, as in the case of the reverse micelle method, since the synthesis reaction is performed at a relatively low temperature, the crystallinity of the semiconductor nanocrystal becomes insufficient, so that it is proposed to add a heat treatment such as firing. For example, a method of isolating the nanocrystals coated with the surfactant as described above and then heating the nanocrystals at a temperature lower than the thermal decomposition temperature of the surfactant (for example, about 200 ° C.) is used. Under the conditions, not only heating for several hours is required to sufficiently improve the crystallinity, but also a part of the surfactant may be thermally denatured to deteriorate the redispersibility. In addition, when heat treatment at a high temperature at which an organic substance such as a surfactant is thermally decomposed is performed, the crystallinity is easily improved, but there is a problem that the organic substance that suppresses the secondary aggregation of nanocrystals is lost. It was (3) A method of injecting a thermally decomposable raw material into a high-temperature liquid-phase organic medium to grow crystals (hereinafter referred to as "hot soap method"). E. B. Katari et al .; Phy
s. Chem. , 98, 4109-4117 (199
4) Cadmium selenide nanocrystals are described in J. Rock
Enberger et al .; Am. Chem. Soc. ，
121, 11595-11596 (1999)
Nanocrystals of —Fe ₂ O ₃ , Mn ₃ O ₄ and Cu ₂ O have been reported respectively. Compared with the reverse micelle method and the sol generation method, the synthetic reaction is performed at about 300 ° C., and thus the nanocrystals of the product are characterized by excellent crystallinity, excellent light absorption and emission characteristics, and excellent particle size distribution. However, it uses expensive and chemically unstable organometals such as dimethylcadmium and diethylzinc as raw materials, uses expensive organic substances such as trioctylphosphine oxide and hexadecylamine as reaction solvents, or scales. There is a limit to industrial use in that the quality of the product (for example, absorption / emission wavelength, particle size distribution, etc.) fluctuates sensitively due to changes in reaction conditions such as up.

As can be seen from the above-mentioned conventional techniques, in producing semiconductor nanocrystals, crystallinity and dispersibility (or 2
A method of simultaneously satisfying the following three points: suppression of secondary aggregation) and use of inexpensive raw materials has not been known.

[0004]

DISCLOSURE OF THE INVENTION According to the present invention, a hydrosol of semiconductor nanocrystals, which can be obtained as a raw material at low cost and has excellent chemical stability, is used, and the semiconductor nanocrystals have high crystallinity. An object of the present invention is to provide a manufacturing method which imparts excellent dispersibility to an organic matrix (for example, an organic solvent or resin).

[0005]

Means for Solving the Problems As a result of extensive studies conducted by the present inventor to achieve the above object, a fat-soluble molecule (hereinafter referred to as “lipophilic surface-modifying molecule”) having a binding property on the surface of a semiconductor nanocrystal particle has been found. ) Or a water-immiscible organic solution containing the same is brought into contact with a hydrosol of the semiconductor nanocrystals (that is, a dispersion having water as a solvent), whereby the above-mentioned semiconductor nanocrystals are added to the semiconductor nanocrystals at the interface between both phases. Improving the crystallinity of semiconductor nanocrystals while maintaining the dispersibility in the organic matrix by promoting the binding reaction of the lipophilic surface-modifying molecules and coating the former particle surface with the latter to extract into the organic phase The present invention has been achieved by finding that the above is possible.

That is, the gist of the present invention is to provide a first step for producing a hydrosol containing semiconductor nanocrystals and / or precursors thereof, and a lipophilic compound having a binding property to the semiconductor nanocrystals and / or precursors thereof. A method for producing semiconductor nanoparticles, comprising a second step of contacting an organic phase containing a surface modifying molecule with the hydrosol to extract the semiconductor nanocrystals and / or a precursor thereof into an organic phase. Exist.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. [Semiconductor Nanoparticles] The semiconductor nanoparticles in the production method of the present invention are those in which semiconductor nanocrystals and / or precursors thereof are bound to the surface of the particles with a fat-soluble surface modifying molecule described later. Such semiconductor nanoparticles have good dispersibility in an organic matrix such as a resin or an organic solvent due to the effect of the fat-soluble surface modification molecule.

The term "semiconductor nanocrystals" as used herein refers to semiconductor crystals, which will be described later, as a main component and has a number average particle size of usually 0.5 to 50 n.
m, which may have an outer shell having a composition of a heterogeneous semiconductor, a conductor (for example, transition metal or carbon) or an insulator (for example, silica). If the number average particle size is less than 0.5 nm, the properties as a semiconductor crystal (for example, light absorption / emission characteristics and high refractive index property) may not be sufficiently exhibited. Therefore, the lower limit value is preferably 2 nm, more preferably 3 nm. On the other hand, when the number average particle size exceeds 50 nm, the characteristics as a semiconductor nanocrystal (for example, particle size dependency of light absorption and emission characteristics due to quantum effect and transparent dispersibility) may be extremely reduced. Therefore, the upper limit value is preferably 40 nm, more preferably 30 nm.

The number average particle diameter is determined by using a numerical value measured from a transmission electron microscope (TEM) observation image of a given particle. That is, the diameter of a circle having the same area as the observed particle image is defined as the particle size of the particle image. The number average particle diameter is calculated, for example, by a known statistical processing method of image data using the thus determined particle diameter. The number of particle images used for the statistical processing (the number of statistically processed data) is as large as possible. Of course, in the present invention, the number of randomly selected particle images in terms of reproducibility is at least 50, preferably 80 or more, more preferably 100 or more.

It is desirable that the semiconductor nanocrystal has a transition metal element on its surface in order to form a bond with a fat-soluble surface modifying molecule described later. Specifically, semiconductor nanocrystals are titanium oxides among the semiconductor crystals described below,
ZnO, iron oxides, and other transition metal oxides, zinc or cadmium-containing II-VI group compound semiconductors, and transition metal shells (eg, silver, gold, copper, etc., Group 11 of the periodic table). 3 with an elemental zero-valent metal shell)
Two cases are illustrated. The reason is that in these three cases, a mercapto group, a disulfide group, an amino group, a pyridine ring, an amide bond, a carboxyl group, a sulfonic acid group,
It becomes easy to bond a fat-soluble surface-modifying molecule containing a bond-forming functional group such as a phosphonic acid group, a phosphinic acid group, a phosphine oxide group, or the like, to the surface of the semiconductor nanocrystal through the bond-forming functional group. This is because.

The content of the fat-soluble surface-modifying molecule in the semiconductor nanoparticles depends on the molecular weight of the molecule, but is usually 5 to 5.
It is 70% by weight. From the viewpoint of using the minimum weight of the fat-soluble surface-modifying molecule, the upper limit of its content is preferably 50% by weight, more preferably 40% by weight, while its lower limit is preferably in terms of the dispersibility of nanoparticles. It is 10% by weight, more preferably 15% by weight. The content of such surface-modifying molecules is determined by thermogravimetric analysis in which the given semiconductor nanoparticles are heated at 600 ° C. for 90 minutes or more in a nitrogen atmosphere.

When the semiconductor nanoparticles obtained by the production method of the present invention are used for the purpose of absorbing light in a specific wavelength range such as the ultraviolet region, the absorption edge wavelength of the absorption spectrum of the semiconductor nanocrystal is within the range of 300 to 600 nm. Preferably there is. The lower limit of the range of the absorption edge wavelength is more preferably 330 nm, further preferably 370 nm, for the purpose of absorbing an ultraviolet region that deteriorates the organic matter when the particles are dispersed in an organic matter matrix such as a resin. The upper limit is more preferably 550 nm, further preferably 500 nm, and most preferably 450 nm in terms of transparency in the visible region.

[Semiconductor Crystal] Specific examples of the semiconductor crystal
The composition formula is shown below. Periodic table of C, Si, Ge, Sn, etc.
Periodic table group 15 such as simple substance of group 14 element, P (black phosphorus)
Element simple substance, or element of periodic table group 16 element such as Se or Te
Compounds consisting of multiple elements of Group 14 of the periodic table
Thing, SnO₂, Sn (II) Sn (IV) S₃, Sn
S₂, SnS, SnSe, SnTe, PbS, PbS
e, PbTe and other periodic table group 14 elements and periodic table group 16
Compounds with elements, BN, BP, BAs, AlN, Al
P, AlAs, AlSb, GaN, GaP, GaAs,
GaSb, InN, InP, InAs, InSb, etc.
A compound of a group 13 element of the periodic table and a group 15 element of the periodic table
Ruiya III-V compound semiconductor), Al₂S₃, Al₂
Se₃, Ga₂S₃, Ga₂Se₃, Ga ₂Te₃, In
₂O₃, In₂S₃, In₂Se₃, In₂Te₃Periodic table number such as
Compound of Group 13 element and Group 16 element of the periodic table, TlC
Periodic table of the 13th group elements of the periodic table such as l, TlBr, and TlI
Compounds with Group 17 elements, ZnO, ZnS, ZnSe,
ZnTe, CdO, CdS, CdSe, CdTe, Hg
Periodic table group 12 elements such as S, HgSe, HgTe, etc.
Table Compounds with Group 16 elements (or II-VI group compounds)
Semiconductor), As₂S₃, As₂Se₃, As₂Te₃, Sb
₂S₃, Sb₂Se₃, Sb ₂Te₃, Bi₂S₃, Bi₂S
e₃, Bi₂Te₃Periodic table group 15 elements and the periodic table first
Compound with Group 6 element, Cu₂O, Cu₂Periodic table such as Se
CuC, a compound of Group 11 element and Group 16 element of the periodic table
Periodic table of l, CuBr, CuI, AgCl, AgBr, etc.
NiO, a compound of Group 11 element and Group 17 element of the periodic table
Of periodic table group 10 elements and other periodic table group 16 elements
, Group 9 elements of the periodic table such as CoO, CoS and the first of the periodic table
Compound with Group 6 element, α-Fe₂O₃, Γ-Fe₂O₃, F
e₃O_FourOxides such as FeS, and elements of Group 8 of the periodic table such as FeS
Periodic Table Group 7 compounds such as compounds with Group 16 elements in the Periodic Table, MnO, etc.
Compounds of elements with elements of Group 16 of the periodic table, MoS₂, WO₂
Of periodic table group 6 element and other periodic table group 16 element
Thing, VO, VO₂, Ta₂O_FivePeriodic Table Group 5 elements such as
Compounds with Group 16 elements, TiO₂, Ti₂O_Five, T
i₂O₃, Ti_FiveO₉Titanium oxides such as rutile (crystal type is rutile
Type, rutile / anatase mixed crystal type, anatase type
Any) and ZrO₂Periodic Table Group 4 Elements and Period
Table Compounds with Group 16 elements, Y₂O₃, La₂O₃Cycle of etc.
Group 3 elements (including lanthanoid elements) and Periodic Table 1
Periodic table of compounds such as MgS and MgSe with Group 6 elements 2
CdCr compound of group 16 element and periodic table group 16 element
₂O_Four, CdCr₂Se_Four, CuCr₂S_Four, HgCr₂Se_Four
Such as chalcogen spinel, or BaTiO₃Etc.
Can be mentioned. In addition, G. Schmid et al .; Adv. Ma
ter. , Vol. 4, p. 494 (1991).
(BN)₇₅(BF_Two)₁₅F₁₅, D. Fenske
Angew. Chem. Int. Ed. Eng
l. , 29, p. 1452 (1990).
Cu₁₄₆Se₇₃(Triethylphosphine)_{twenty two}like
Semiconductor clusters whose structure is well defined are also exemplified.
Be done.

Of these, those that are practically important are, for example,
If SnO₂, SnS₂, SnS, SnSe, SnTe, P
Periodic table group 14 elements such as bS, PbSe, PbTe, etc.
Compounds with Group 16 elements, GaN, GaP, GaA
s, GaSb, InN, InP, InAs, InSb, etc.
III-V compound semiconductor, Ga₂O₃, Ga₂S₃, G
a₂Se₃, Ga₂Te₃, In₂O₃, In₂S₃, In₂S
e₃, In₂Te₃Periodic table group 13 elements such as and the periodic table first
Compounds with Group 6 elements, ZnO, ZnS, ZnSe, Zn
Te, CdO, CdS, CdSe, CdTe, HgO,
II-VI group compounds such as HgS, HgSe, and HgTe
Conductor, As₂O₃, As₂S₃, As₂Se₃, As₂Te₃,
Sb₂O₃, Sb₂S₃, Sb₂Se₃, Sb₂Te₃, Bi₂
O₃, Bi₂S₃, Bi₂Se₃, Bi₂Te₃Periodic table number such as
Α-Fe, a compound of Group 15 element and Group 16 element of the periodic table
₂O₃, Γ-Fe₂O₃, Fe₃O_FourIron oxides such as FeS
A compound of an element of Group 8 of the periodic table with an element of Group 16 of the periodic table,
The above-mentioned titanium oxides and ZrO ₂And other elements in Group 4 of the periodic table
Compound with Group 16 element of the periodic table, Y₂O₃, La₂O₃Etc.
Periodic table Group 3 elements (including lanthanoid elements) and periodic table
It is a compound with a Group 16 element.

Among these, SnO ₂ , GaN, Ga
P, In ₂ O ₃ , InN, InP, Ga ₂ O ₃ , Ga ₂ S ₃ ,
In ₂ O ₃ , In ₂ S ₃ , ZnO, ZnS, CdO, Cd
S, the above-mentioned iron oxides, rutile-type or anatase-type titanium dioxide, ZrO ₂ , Y ₂ O ₃ , MgS and the like do not contain a highly toxic negative element, and are therefore preferable in terms of environmental pollution resistance and safety to living organisms. From this viewpoint, SnO ₂ , In ₂ O ₃ , ZnO,
ZnS, α-Fe ₂ O ₃ , rutile titanium dioxide, ZrO
_A composition that does not contain a highly toxic positive element such as ₂ , Y ₂ O ₃ is more preferable.

Oxide semiconductor crystals such as ZnO, α-Fe ₂ O ₃ , rutile-type titanium dioxide, and Y ₂ O ₃ have a light-absorbing ability, a high refractive index, safety, and are inexpensive. It is most preferable for applications such as high refractive index coating. In addition, colored semiconductor crystals having absorptivity in the visible region, such as iron oxides such as α-Fe ₂ O ₃ are important for coloring materials such as pigments.

In the case of utilizing the light emitting ability of semiconductor nanocrystals, GaN and Ga having an emission band in the visible region and its vicinity are used.
III-V group compound semiconductors such as P, GaAs, InN, InP, ZnO, ZnS, ZnSe, ZnTe, Cd
II-VI group compound semiconductors such as O, CdS, CdSe, CdTe, HgO, and HgS, In ₂ O ₃ , In ₂ S _{3, and the} like are important. Among them, semiconductor crystal grain size controllability and luminous ability are preferable. ZnO, ZnS, ZnSe, ZnTe, C
II-VI group compound semiconductors such as dO, CdS, and CdSe, and particularly ZnO, ZnS, ZnSe, CdS, and Cd.
Se and the like are more preferably used for this purpose.

In the composition of any of the semiconductor crystals exemplified above, Al, Mn, Cu, Zn, A as a trace amount of a doping material (meaning impurities intentionally added) is added as necessary.
Elements such as g, Cl, Ce, Eu, Tb, and Er may be added. The semiconductor nanocrystal according to the present invention is, for example, A.
R. Kortan et al .; Am. Chem. Soc. ，
112, 1327 (1990) or US Pat.
As reported in Japanese Patent No. 985173 (1999), a so-called core-shell structure composed of an inner core (core) and an outer shell (shell) may be used. Such core-shell type semiconductor nanocrystals may be suitable for applications using the exciton absorption / emission band. In this case, it is generally effective to form an energy barrier by using a semiconductor crystal composition of the shell having a band gap (band gap) larger than that of the core. It is presumed that this is due to a mechanism that suppresses the influence of an undesired surface level or the like due to the influence of the external environment or the crystal lattice defect on the crystal surface.

The composition of the semiconductor crystal preferably used for such a shell depends on the band gap of the core semiconductor crystal, but the band gap in the bulk state has a temperature of 300K.
At 2.0 eV or more, eg B
III-V group compound semiconductors such as N, BAs, GaN and GaP, ZnO, ZnS, ZnSe, ZnTe, CdO, C
A II-VI group compound semiconductor such as dS, a compound of a group 2 element of the periodic table and a group 16 element of the periodic table such as MgS or MgSe, and the like are preferably used. Among these, the semiconductor crystal composition which becomes a more preferable shell is III, such as BN, BAs, and GaN.
-Group V compound semiconductor, ZnO, ZnS, ZnSe, Cd
1. The II-VI group compound semiconductor such as S, the band gap in the bulk state of the compound of the periodic table group 2 element such as MgS, MgSe and the like, and the group 16 element of the periodic table at a temperature of 300K.
More than 3 eV, most preferably B
N, BAs, GaN, ZnO, ZnS, ZnSe, Mg
The band gap in the bulk state of S, MgSe, etc. is at temperature 3
It is 2.5 eV or more at 00K, and ZnS is most preferably used in chemical synthesis. When a particularly preferred combination example of the core-shell composition is expressed by a composition formula,
CdSe-ZnS, CdSe-ZnO, CdSe-Cd
S, CdS-ZnS, CdS-ZnO, etc. are mentioned.

[Hydrosol] The hydrosol in the present invention means a dispersion liquid in which the semiconductor nanocrystals and / or their precursors are dispersed in an aqueous solvent mainly containing water. The aqueous solvent is uniform, and the content of water in the aqueous solvent is usually 70% by weight or more, preferably 80% by weight or more, and more preferably 9% from the viewpoint of phase separation from the organic phase described later.
It is 0% by weight or more. Examples of the water-miscible organic solvent that may be mixed with the aqueous solvent include alcohols having 3 or less carbon atoms such as methanol, ethanol, n-propanol and isopropyl alcohol, and carbon numbers such as ethylene glycol, propylene glycol and butylene glycol. Examples thereof include glycols of 4 or less and polyhydric alcohols such as glycerin and pentaerythritol.

The content of the semiconductor nanocrystals and / or their precursors in the hydrosol is not limited, but is usually 0.001 to 10% by weight.
Alternatively, the upper limit thereof is preferably 5% by weight, more preferably 2% by weight in view of dispersibility of the precursor in the hydrosol, while the lower limit thereof is preferably 0.0% in view of productivity.
It is 1% by weight, more preferably 0.1% by weight.

The precursor of the semiconductor nanocrystal referred to here is
It is an inorganic particle that does not necessarily have to be a semiconductor, and is one that is dispersed in the above aqueous solvent and does not settle due to gravity. The particle size is usually about the same as the number average particle size of the semiconductor nanocrystals. Examples of such precursors include hydrated iron oxides (eg, goethite and acagonite, which are precursors that give iron oxide nanocrystals such as hematite (α-Fe ₂ O ₃ ) and magnetite (Fe ₃ O ₄ ). Alternatively, iron oxides having a hydroxyl group whose composition is indefinite), hydrated titanium oxide that gives titanium oxide nanocrystals having anatase-type or rutile-type crystals, and the like.

The pH (hydrogen ion concentration) of the hydrosol in the present invention is not limited as long as it does not extremely hinder the extraction of the semiconductor nanocrystals into the organic phase, but is usually 1 to 1
2. The reactivity with the bond-forming functional group contained in the lipophilic surface-modifying molecule and the stability of the bond formed are preferably 2-1.
It is 0. [Fat-soluble surface-modifying molecule] The fat-soluble surface-modifying molecule according to the present invention is bound to the semiconductor nanocrystals dispersed in the hydrogel or a precursor thereof to modify the surface thereof to be fat-soluble, thereby forming an organic phase. It is an organic compound having dispersibility and having a function of extracting semiconductor nanocrystals and / or precursors thereof into an organic phase. There is no limitation on the mode of binding of the lipophilic surface-modifying molecule to the semiconductor nanocrystal or its precursor, but it is usually by a chemical bond such as a covalent bond, an ionic bond, a coordinate bond, a hydrogen bond and the like. In the present invention, the chemical structure of the lipophilic surface-modifying molecule that forms such a bond is referred to as a bond-forming functional group.

The molecular weight of the fat-soluble surface-modifying molecule is not particularly limited as long as it exerts the above-mentioned extraction action, but it is extremely volatilized in the third step described below in which the organic phase is heated to about 150 to 400 ° C. It is not easy and it is desirable to avoid unnecessary high molecular weight.
It is 0, preferably 170 to 400, more preferably 190 to 350.

The above lipophilic surface-modifying molecule has sufficient lipophilicity when the proportion of the hydrocarbon structure (eg, alkyl group, alkylene group, hydrocarbon aromatic ring, etc.) in its molecular structure is 40% by weight or more. This value is desirable in order to exhibit, and this value is preferably 50% by weight or more, more preferably 60% by weight or more. Preferred hydrocarbon structures include n-propyl group, isopropyl group, n-butyl group,
Isobutyl group, n-pentyl group, cyclopentyl group, n
-Hexyl group, cyclohexyl group, octyl group, decyl group, dodecyl group, hexadecyl group, octadecyl group, and other alkyl groups having about 3 to 20 carbon atoms, phenyl group, benzyl group, naphthyl group, naphthylmethyl group, and other aromatic carbonization Examples thereof include a hydrocarbon group containing a hydrogen group, and among them, a linear alkyl group having about 6 to 16 carbon atoms such as an n-hexyl group, an octyl group, a decyl group, a dodecyl group, and a hexadecyl group is more preferable.

The above bond-forming functional group is not limited, but examples thereof include a sulfur atom-containing functional group such as a mercapto group, a disulfide group and a thiophene ring, and a nitrogen atom-containing functional group such as an amino group, a pyridine ring, an amide bond and a nitrile group. , A carboxyl group, a sulfonic acid group, a phosphonic acid group, an acidic functional group such as a phosphinic acid group, a phosphorus atom-containing functional group such as a phosphine group or a phosphine oxide group, or a hydroxyl group, a carbonyl group,
Examples thereof include ester bonds, ether bonds, oxygen atom-containing functional groups such as polyethylene glycol chains. Of these, sulfur atom-containing functional groups such as mercapto groups and disulfide groups, amino groups, nitrogen atom-containing functional groups such as pyridine rings and amide bonds, carboxyl groups, sulfonic acid groups, phosphonic acid groups and phosphinic acid groups A functional group, a phosphorus atom-containing functional group such as a phosphine group or a phosphine oxide group is preferable in terms of binding to the semiconductor nanocrystal and / or its precursor, and among them, a mercapto group, an amino group, a carboxylic acid amide group (- CONH2), a carboxyl group, a phosphonic acid group and a phosphine oxide group are more preferable. The mercapto group is a bonding force to a transition metal element (for example, elements of Group 11 and 12 of the periodic table such as silver, gold, copper, zinc, cadmium, etc.), and the phosphonic acid group is an oxide (for example, titanium dioxide, oxidation). Zinc, iron oxide, etc.) are most preferable in terms of binding force to the surface. On the other hand, since the amino group, the carboxylic acid amide group and the phosphine oxide group have a relatively loose binding force, the lipid-soluble surface modifying molecule may be removed or replaced with another organic compound during or after the step of the production method of the present invention. It is most preferably used when necessary. Two or more and / or two or more kinds of the bond-forming functional groups exemplified above may be present in the molecular structure as long as the effect of the fat-soluble surface modifying molecule is not significantly deteriorated, but usually one is present. Is desirable.

Specific lipophilic surface-modifying molecules include 1
-Mercapto-n-butane (or n-butyl mercaptan), 1-mercapto-n-hexane, 1-mercapto-n-octane, 1-mercapto-n-decane, 1-mercapto-n-dodecane, 1-mercapto- ω-mercaptoalkanes such as n-hexadecane, benzenethiol, thiols having a phenyl group such as mercaptophenylmethane (or benzylmercaptan), 1-amino-n-butane (or n-butylamine), 1-amino-
ω-aminoalkanes such as n-hexane, 1-amino-n-octane, 1-amino-n-decane, 1-amino-n-dodecane, 1-amino-n-hexadecane, aniline, aminophenylmethane (or Amines having a phenyl group such as benzylamine), fatty acids such as n-butanoic acid, n-hexanoic acid, n-octanoic acid, n-decanoic acid, n-dodecanoic acid, n-hexadecanoic acid and oleic acid, n
-Fatty acid amides, n-hexanoic acid amides, n-octanoic acid amides, n-decanoic acid amides, n-dodecanoic acid amides, n-hexadecanoic acid amides, oleic acid amides and other fatty acid amides, benzoic acid amides, cinnamic acid Carboxylic amides having a phenyl group such as amides, n-butylphosphonic acid, n-hexylphosphonic acid, n-octylphosphonic acid, n-decylphosphonic acid, n-dodecylphosphonic acid, n-hexadecylphosphonic acid, etc. Phosphonic acids having a phenyl group such as aliphatic phosphonic acids and benzenephosphonic acid, trialkylphosphine oxides such as tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide and tridecylphosphine oxide, triphenylphosphine oxide, benzyldioctyl oxide Phosphine oxides having a phenyl group of the scan fin oxide, and the like, and the like.

[Manufacturing Method of Semiconductor Nanoparticles] The manufacturing method of the present invention is, as will be described below, a semiconductor nanocrystal and
Or to produce a hydrosol containing the precursor thereof
Step, and contacting the hydrosol with an organic phase containing a lipophilic surface-modifying molecule having a binding property to the semiconductor nanocrystal and / or its precursor, to bring the semiconductor nanocrystal and / or its precursor into an organic phase. It includes three steps, a second step of extracting the organic phase and a third step of heating the organic phase, if necessary.

(1) First step This is a step of forming the semiconductor nanocrystals and / or their precursors in an aqueous solvent mainly containing water. The content of the aqueous solvent, the content of the semiconductor nanocrystals and / or the precursor thereof in the hydrosol to be generated, and the pH of the hydrosol are the same as those described in the hydrosol section. There is no limitation on the reaction mechanism of formation of such a hydrosol,
For example, the sol generation method described in the above-mentioned prior art, that is, hydrolysis or vulcanization of a metal salt in an aqueous solvent or an alcoholic solvent, and a condensation reaction associated therewith, are used to form semiconductor nano-particles such as metal oxides or metal sulfides. A method for directly producing crystals and / or precursors thereof is exemplified, but semiconductor nanocrystals prepared by other methods (for example, the vapor phase method, the other liquid phase method such as the reverse micelle method and the hot soap method). And / or the precursor thereof may be used as a raw material and dispersed in an aqueous solvent to form a hydrosol. The most preferably used of these is the above-mentioned sol generation method.

Examples of the raw material in the sol production method include titanyl sulfate for the synthesis of titanium oxide nanocrystals and zinc salts such as zinc acetate and zinc nitrate for the synthesis of zinc oxide nanocrystals. Metal alkoxides such as tetraethyl orthosilicate (abbreviation TEOS) and tetraisopropoxy orthotitanate can also be preferably used as a raw material. In particular, in the case of synthesizing oxide nanocrystals by a sol generation method, for example, as in the synthesis of titanium oxide nanocrystals using titanyl sulfate as a raw material, a precursor such as hydroxide is used, and then an acid or alkali (preferably Procedures for dehydration condensation or deflocculation of this (with an acid) to form a hydrosol are also possible. In the procedure via such a precursor, it is preferable in terms of purity of the final product to isolate and purify the precursor by an arbitrary method such as filtration or precipitation separation (centrifugation if necessary).

(2) Second Step A two-phase system of the hydrosol obtained in the first step and an organic phase capable of forming a phase separated from water (hereinafter referred to as “extracted organic phase”) is brought into contact with the organic phase. This is a step of extracting the semiconductor nanocrystals and / or their precursors into the phase. Such an extracted organic phase is
Although a small amount of water may be dissolved by contact with a hydrosol, it is either a melt of the fat-soluble surface modifying molecule described above or an organic solvent (hereinafter referred to as “modifying molecule solution”) in which the melt is dissolved. As a mechanism for the fat-soluble surface modifying molecule to work at such a two-phase system interface, a kind of phase transfer catalytic action, that is, a semiconductor nanocrystal and / or a precursor thereof in which a bond-forming functional group of the fat-soluble surface modifying molecule is present in the hydrosol phase It is considered that an interfacial reaction that binds to the surface of the semiconductor nanocrystal and / or its precursor increases in lipophilicity and moves to the extracted organic phase as the interfacial reaction proceeds.

The volume ratio of the hydrosol phase to the extracted organic phase in the second step depends on the content of the semiconductor nanocrystals and / or the precursor thereof in the hydrosol, but is usually 99: 1 to 1.
The volume ratio is in the range of about 1:99, and the volume ratio is preferably 90:10 to 10:90, and more preferably 80:20 to 20:80 from the viewpoint of increasing the interface area. The extracted organic phase may contain an organic solvent, but the content of the lipophilic surface-modifying molecule in the extracted organic phase is such that the surface of the semiconductor nanocrystal to be extracted and / or its precursor is coated Sufficient amount to make the oil soluble. Specifically, it is usually 1 to 100 as a weight percentage in the extracted organic phase.
%, In terms of extraction power, it is preferably 10 to 100%, and more preferably 20 to 100%.

The organic solvent that may be contained in the above extracted organic phase is not limited as long as it can form a phase that is not uniformly miscible with water. Specifically, pentane, hexane, heptane, octane, isooctane. Alkanes such as methylene chloride, chloroform, dichloroethane and other halogenated aliphatic hydrocarbons, benzene, toluene, xylene and other aromatic hydrocarbons, chlorobenzene, dichlorobenzene, etc.
Examples thereof include halogenated aromatic hydrocarbons such as bromobenzene, ethers such as diethyl ether and dibutyl ether, esters such as methyl acetate, ethyl acetate and butyl acetate, and higher alcohols such as hexanol and octanol. Of these, alkanes such as hexane, heptane, octane, and isooctane, aromatic hydrocarbons such as toluene and xylene, and halogenated aromatic hydrocarbons such as chlorobenzene are not too high in chemical stability and volatility. It is preferable in terms of boiling point and non-hydrophilicity that are easily removed, and among them, aromatic hydrocarbons such as toluene and xylene and halogenated aromatic hydrocarbons such as chlorobenzene are more preferable in terms of solubility.

The extraction temperature in the second step is usually 0 to 1
The temperature is 00 ° C., and the lower limit is preferably 10 ° C., more preferably 20 ° C. from the viewpoint of the dissolving power of the extracted organic phase, and the upper limit is preferably for the purpose of suppressing solvent volatilization of the hydrosol or the extracted organic phase. 90 ° C., more preferably 80 ° C. On the other hand, there is no limitation on the extraction time in the second step, but it is usually 0.5 to 1500 minutes, and in view of the extraction yield, the lower limit value is preferably 1 minute, more preferably 10 minutes. In this respect, the upper limit value is preferably 1000 minutes, more preferably 500 minutes.

In some cases, it is preferable to carry out the second step in an inert gas atmosphere such as nitrogen or argon for the purpose of preventing denaturation such as oxidation of semiconductor nanocrystals and / or their precursors and organic substances. Depending on the situation, light may be shielded. (3) Third step This is a step of heating the semiconductor nanocrystals and / or their precursors extracted in the extraction organic phase in the second step, if necessary. The organic phase containing the semiconductor nanocrystals and / or the precursor thereof that is heated in the third step is hereinafter referred to as “heated organic phase”. The main purpose of this step is to generate semiconductor nanocrystals by heating and / or to improve the crystallinity thereof, but as a secondary effect, the number average particle size of the semiconductor nanocrystals and / or their precursors. There may be an increase in In the third step, the extracted organic phase may be used as the heated organic phase as it is, but an organic solvent having a relatively low boiling point is removed in advance by distillation or the like as the heated organic phase for the purpose of achieving a high heating temperature. In any of these cases, a new solvent may be added for the purpose of temperature control by heating under reflux at a predetermined temperature.

The temperature of the organic phase to be heated in the third step is usually 150 to 400 ° C. In terms of improving the crystallinity of the semiconductor nanocrystals and / or their precursors, the lower limit is preferably 180 ° C., more preferably 200 ° C., on the other hand, due to thermal decomposition of organic substances such as fat-soluble surface modification molecules and solvents. The upper limit is preferably 380 ° C., and more preferably 350 ° C. from the viewpoint of suppressing denaturation.

The heating in the third step is preferably performed in an atmosphere of an inert gas such as nitrogen or argon. this is,
This is to prevent denaturation such as oxidative deterioration of organic substances due to heating. The inert gas atmosphere in the present invention means an atmosphere of the above-mentioned inert gas having an oxygen gas concentration of usually less than 1%, preferably less than 0.1%, more preferably less than 0.05%.

The semiconductor nanocrystals and / or precursors thereof produced through the third step are usually present in the state of semiconductor nanoparticles having the lipid-soluble surface-modifying molecules bound to the surface thereof in the second step. As a post-treatment for isolating this, for example, a precipitation-precipitation operation of the semiconductor nanoparticles by injecting the heated organic phase into a poor solvent (for example, alcohols such as methanol which may contain water) is carried out. You can go.

[0039]

EXAMPLES Specific examples of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. [Measuring device] (1) Transmission electron microscope (TEM): H manufactured by Hitachi, Ltd.
-9000UHR transmission electron microscope (accelerating voltage 300k
V, the degree of vacuum during observation is about 7.6 × 10 ^-9 Torr). (2) Emission spectrum: F2500 spectrofluorimeter made by Hitachi Ltd. (3) Absorption spectrum: Hewlett-Packard H
P8453 UV / Visible absorptiometer.

[Synthesis Example of Hydrosol] Synthesis Example 1: Hydrosol iron (III) nitrate nonahydrate (4.03 g) containing hydrated iron oxide was added to water (1) at room temperature.
0 mL), and a 2.5 N aqueous solution of sodium hydroxide (10 mL) was added dropwise with stirring over 25 minutes. Further, stirring was continued at room temperature to obtain a hydrosol having a pH of 1.68 and a dark wine red color.

Synthesis Example 2: Hydrosol containing titanium oxide nanocrystals While stirring an aqueous solution of titanyl chloride having a concentration of 0.1 mol / L, the same volume of an aqueous solution of sodium carbonate having a concentration of 1.5 mol / L was used at room temperature for 25 hours. It dripped over minutes. The suspension of white ultrafine particles thus obtained was centrifuged (4000 rp).
m), removal of the supernatant by decantation and washing with water were repeated in this order for purification. However, the purification was carried out until the white turbidity of barium sulfate was not visually observed even if an aqueous barium hydroxide solution was added to the supernatant. The white precipitate thus obtained was stirred and dispersed in dilute hydrochloric acid having a concentration of 0.3 mol / L and heated at 60 ° C. for about 1 hour to obtain a transparent acidic hydrosol. This hydrosol was ice-cooled, and an aqueous solution of sodium dodecylbenzenesulfonate (abbreviated as DBS) (concentration of 0.05 mol / L) was added. As a white precipitate was produced, this was extracted with toluene and concentrated. From the TEM observation of this concentrated residue, it was found that the titanium oxide nanocrystals contained in the titanium oxide hydrosol had a number average particle diameter of 5 nm. Further, it was found from the X-ray diffraction spectrum that the titanium oxide crystals were mainly anatase type crystals.

[Production Example of Semiconductor Nanoparticles] Example 1: Magnetite Nanoparticles The wine red-colored hydrosol (1 obtained in Synthesis Example 1)
Hexadecylamine (1.465 g) dissolved in toluene (15 mL) was added to 2 mL), and the mixture was vigorously stirred at room temperature. The organic phase separated by standing was concentrated and dried in vacuum to obtain a brown solid (1.19 g). This brown solid (512.8 mg) was mixed with hexadecylamine (8.10 g) in a glass container at 100 ° C.
The mixture was vacuum dried with stirring at, and then placed under a dry argon atmosphere at atmospheric pressure. The reaction solution is approximately 1
When heated for a period of time, the liquid color became black, so it was cooled by air, poured into methanol (20 mL) before the reaction liquid solidified, and stirred for 10 minutes to precipitate a solid. The precipitate was separated by centrifugation (3000 rpm), the supernatant was removed, and toluene (3 mL) was added to redissolve the precipitate. Pour the redissolved solution back into methanol (20 mL) 1
A solid was precipitated by stirring for 0 minutes, and the precipitate was centrifuged (3000 rpm) to settle to remove the supernatant.
The purified precipitate thus obtained was vacuum dried to obtain a black powder (32 mg). From the X-ray diffraction spectrum (shown in FIG. 1) of this black powder, it was found that the particles were mainly composed of magnetite nanocrystals. Further, it was found by TEM observation that the number average particle size of the magnetite crystals was about 6 nm.

Since the magnetite nanoparticles obtained in Example 1 were re-dissolvable in toluene and gave a transparent solution with no turbidity by visual observation, it was considered that they were dispersed as nanoparticles. Further, when polymethylmethacrylate is dissolved in such a toluene solution and spin-coated on a glass plate to give a transparent coating film, the magnetite nanoparticles are excellent in dispersibility in an organic resin such as an acrylic resin.

Example 2 Titanium Oxide Nanoparticles To the acidic hydrosol obtained in Synthesis Example 2, was added toluene containing octylphosphonic acid or tetradecylphosphonic acid, and the mixture was vigorously stirred, and the organic phase obtained by allowing this to stand was obtained. The layers are separated and concentrated to give a residue. The residue is redispersed in tetradecylphosphonic acid in a brown glass flask and heated in a dry argon atmosphere in the same procedure as in Example 1 to obtain titanium oxide nanoparticles with improved crystallinity.

[0045]

The production method of the present invention utilizes the hydrosol method, which is a simple liquid phase synthesis method for semiconductor nanocrystals,
Semiconductor nanoparticles having both high crystallinity and nanodispersion can be provided. According to the production method of the present invention, semiconductor nanoparticles having excellent dispersibility in an organic matrix (for example, organic solvent, resin, etc.) can be advantageously obtained from inexpensive salts having excellent chemical stability as raw materials.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction spectrum diagram of magnetite nanoparticles obtained in Example 1.

Claims (5)

[Claims] 1. A first step for producing a hydrosol containing semiconductor nanocrystals and / or precursors thereof, and a lipophilic surface-modifying molecule having binding properties to the semiconductor nanocrystals and / or precursors thereof. A method for producing semiconductor nanoparticles, comprising a second step of bringing the organic phase and the hydrosol into contact with each other to extract the semiconductor nanocrystal and / or a precursor thereof into the organic phase. 2. The lipophilic surface-modifying molecule is a mercapto group,
Disulfide group, amino group, pyridine ring, amide bond,
The semiconductor nanoparticle according to claim 1, which has at least one bond-forming functional group selected from the group consisting of a carboxyl group, a sulfonic acid group, a phosphonic acid group, a phosphinic acid group, a phosphine group, and a phosphine oxide group. Manufacturing method. 3. The molecular weight of the lipophilic surface-modifying molecule is 150 to
The method for producing semiconductor nanoparticles according to claim 1, wherein the method is 500. 4. The organic phase containing the semiconductor nanocrystals and / or their precursors obtained in the second step is heated to 150 to 400 ° C.
The method for producing semiconductor nanoparticles according to claim 1, further comprising a third step of heating the semiconductor nanoparticles. 5. The method for producing semiconductor nanoparticles according to claim 4, wherein the heating in the third step is performed in an inert gas atmosphere.