JPH01305806A - Production of superfine particle of metal sulfide, metal selenide, or their mixed crystal - Google Patents

Abstract

PURPOSE:To obtain the title superfine particles by preparing the colloid of the sulfide, selenide, or their mixed crystal of a specified metal, adding an ionic surfactant to flocculate the colloid, and then extracting the superfine particles with an org. solvent difficultly soluble in water. CONSTITUTION:An aq. soln. of the ion of Cd, Zn, Pb, Ga, In, Ge, Sn, or Cu and an aq. soln. contg. a compd. supplying the ion of S and/or Se and held at 2-12pH are mixed to prepare the colloid of the metal sulfide, metal selenide, or their mixed crystal having <=150Angstrom particle radius. The colloid is then added with an ionic surfactant, and flocculated. An org. solvent difficultly soluble in water is added to transfer the superfine particles into the org. solvent. Water is then separated, and the org. solvent in the obtained transparent organocolloid is removed to obtain the superfine particles of the metal sulfide, metal selenide, or their mixed crystal having <=150Angstrom particle diameter.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing ultrafine particles of metal sulfides, metal selenides, or mixed crystals thereof, and more specifically relates to photochemical reactions related to conversion and storage of light energy. The present invention relates to a method for producing ultrafine particles of metal sulfides, metal selenides, or mixed crystals thereof useful as catalysts or photosensitizers, electrophotographic photoreceptors, nonlinear optical materials, piezoelectric materials, and other optoelectronic functional materials.

(Prior art) Metal sulfides and metal selenides such as CdS and CdSe are
It has been used as an inorganic pigment, electrophotographic photoreceptor, etc. For inorganic pigments, emphasis is placed on their hiding power, and in general, inorganic pigments' It! 'Wl force is determined when the particle diameter of the pigment particles is 1/2 of the wavelength of visible light, that is, 0.2 to 0.
It is said that the hiding power is maximum at 3 μm, and that the hiding power decreases no matter whether it is larger or smaller than that. This is 0.3μ
This is because when the particle size becomes larger than m, the surface area becomes smaller and the total amount of light reflected on the particle surface decreases, and when the particle size becomes smaller than 0.2 μm, the light transmittance increases. From this point of view, conventionally 0.2
Metal sulfides, metal selenides, etc. having a particle size of ~0.3 μm or more have been researched and developed and have been used industrially.

There are two known methods for producing metal sulfides and metal selenides of such size: dry method and wet method. There are two methods: heating a mixture of cadmium oxide and cadmium, or heating cadmium in hydrogen sulfide.A wet method involves reacting hydrogen sulfide gas with an aqueous solution of cadmium sulfate, cadmium chloride, etc. and precipitating it. be. JP-A-59-192256, JP-A-60-133455, etc. disclose methods for producing CdS powder particularly for use in electrophotographic photoreceptors.

(Problem to be solved) However, it is necessary to express optical functions so that it can be used as a catalyst or photosensitizer for photochemical reactions related to the conversion and storage of light energy, as an optoelectronic functional material for electrophotographic photoreceptors, nonlinear optical materials, piezoelectric materials, etc. If the purpose is to improve transparency, it is necessary to further reduce the particle size to impart transparency. Reducing the particle size not only helps improve transparency, but also brings about the so-called quantum effect, which is useful.

Metal crystals and ionic crystals have different physical properties depending on their particle size, that is, the number of atoms and ions that make up the crystal. In particular, these crystals are formed by long-range acting forces such as metal bonding forces and Coulomb forces, and the valence and conduction electrons in the crystal interact with the entire crystal lattice, so the crystal grain size changes from bulk to ultrafine. When they become extremely small, their physical properties change significantly and quantum effects occur.

Quantum size effects and dimensional effects are also important in nonlinear optical effect materials, which are expected to become increasingly important in future optoelectronic devices, and the importance of ultrafine particles such as metal sulfides has been pointed out (Flower et al. Materials, Applied Physics, 1dan (10).

1348-1352 (1987)).

Such ultrafine particles of metal sulfides and metal selenides cannot be produced using conventional manufacturing methods; in other words, conventional methods involve in-phase reactions and precipitation reactions, making it difficult to control the shape and diameter of the particles. For example, in the wet method described above, as the Cd ion concentration in the reaction system increases, the shape of the precipitated particles becomes unstable.
Agglomerates are generated and the width of the particle size distribution becomes wide, and in more severe cases, tabular aggregates called flakes with a diameter of about 10 to 30 μm may be formed.

Although various attempts have been made to improve these conventional methods, the particle size of CdS and the like that can currently be produced industrially is 1.0 μm or more, and it is difficult to produce ultrafine particles of 200 Å or less.

Therefore, the present invention aims to use superimposed metal sulfides, selenides, or mixed crystals thereof, which have a particle radius of 150 Å or less, have good dispersibility in various organic binders, and polymers, and have a particle radius of 150 Å or less to express optoelectronic functions. Aim to provide a method for manufacturing fine particles 6 As a result of intensive technical studies to achieve the above-mentioned object, the present inventors prepared colloidal ultrafine particles,
Afterwards, he discovered a method for extracting ultrafine particles from colloidal solutions.

Generally, it is difficult to extract fine particles from a colloidal solution, and even more so, it is nearly impossible to extract them while maintaining the ultrafine particle state on an industrial scale using normal methods.

Furthermore, even if colloidal particles can be extracted, since they are ultrafine particles, their surface energy is abnormally large, resulting in problems such as drying and agglomeration, and it is difficult to extract them while maintaining the particle size at the time of precipitation. is extremely difficult.

The present inventors have further overcome such problems and have arrived at the present invention.

(Means for solving problems) That is, the present invention fl) (a) Cd, Zn, Pb, Ga, In.

Mixing an aqueous solution containing one or more of Ge, Sn or Cu ions, and (b) an aqueous solution containing a compound that supplies S and/or Se ions and whose pH is adjusted to 2 to 12. Stir to prepare a colloid of metal sulfide, metal selenide, or a mixed crystal thereof with a particle radius of 150 Å or less, (2) add an ionic surfactant to the colloid, and then
(3) Add an organic solvent that is poorly soluble in water to the aggregate to disperse and transfer the ultrafine particles into the organic solvent, and then separate the water to prepare a transparent organocolloid. (4) Furthermore, the present invention provides a method for producing ultrafine particles of metal sulfides, metal selenides, or mixed crystals thereof with a particle radius of 150 Å or less, which is characterized by removing some solvent in the organocolloid.

The metal sulfides, metal selenides, or mixed crystals thereof in the present invention are the following compounds.

That is, Cd, Zn, Pb, Ga, In, Ge, Sn
, Cu, etc., and S and/or Se, for example, CdS, ZnS, PbS, GaS, InS, Ge
S, SnS, CuS, CdSe, Zn5e, Pb5e,
GaSe, InSe, GeSe, 5nSe, CuS
As these mixed crystals, such as ccisxse+
−x, Z n S x S e + −x IO<
x < 1), etc.

The method of the present invention consists of four processes, tl) to (4), as described above, and each process will be described in turn.

First, the process (1) is (a) Cd, Zn, Pb, Ga, In, Ge.

J! This is a process of mixing and stirring a uniform aqueous solution to prepare a colloid of metal sulfide, metal selenide, or a mixed crystal thereof with a particle radius of 150 Å or less.

The metal ions in (a) above include non-tionic acid salts of these metals such as chlorides, sulfates, nitrates, and perchlorates;
It is supplied using organic acid salts such as acetates as raw materials. Specifically, for example, CdCff, , Cd (No3), , C
d (CI2041., Cd50,, Cd (CH3
Coo )2, Zn (cgo, 12, Pb (NO
3)2. Examples include Pb (CH3COOh, etc.).

The metal ion concentration is preferably io-' to 15not/
j2, more preferably 10-3 to 1.0 mol
/12.

Examples of compounds that supply S or Se in the above (b'l) include (NHnlz S, Na z S, N
aH3, (C2H, 1, NH5, H2S, (NH4)
2 S e , N az S e ,
N a HS e, (CzHsl+ Nt(Se, H2
Examples include Se.

When using a compound that is gaseous at room temperature, such as H2S or HzSe, the tempering gas is dissolved in water or used while being dissolved.

The ion concentration of S and/or Se in (b) is
Preferably it is 10-4 to lomol/J2, more preferably 10-3 to 1 mol/β.

In the t8 solution (b), NaO[(p)(p) is adjusted to 2 to 12 with a base such as NaO[(p)] or an acid such as hydrochloric acid.

Further, a colloid stabilizer, that is, a particle growth inhibitor may be added to the solution (b).

As such a particle growth inhibitor, an anionic polymeric surfactant or a nonionic polymeric surfactant such as a carboxylic acid type, sulfuric acid ester type, or sulfonic acid type is used. Specifically, for example, copolymers of acrylic acid and styrene, ethylene, isobutylene, etc., partially saponified products thereof,
Salt, amide, ester, etc., maleic anhydride/styrene copolymer system. The concentration of particle growth inhibitor is S or S
e It varies depending on the type and amount of the compound, the amount of surfactant used later, etc., so it is determined appropriately, but it is preferably 0.5
% by weight or less.

Next, the solutions (a) and (b) are vigorously mixed and stirred to prepare a colloid with a particle radius of 150 Å or less. At this time, the mixing ratio of solutions (a) and (b) is 1:2 to
The ratio is 1:50 (capacity ratio).

The mixing is preferably carried out by dropping the solution (a) into the solution (b) little by little, and the temperature at this time is preferably 30°C or lower.

Next, the process (2) is a process in which an ionic surfactant is added to the colloid prepared in the fil process and the colloid is once coagulated.

Here, the addition of the ionic surfactant aggregates the ultrafine colloid particles prepared in (1), facilitates their transfer into the organic solvent in the next process (3), and forms a stable organocolloid. It's to get it.

As the ionic surfactant, both low-molecular and high-molecular types can be used as long as they are soluble in water.

Preferred examples of the low molecular weight anionic surfactant include sodium dodecylbenzenesulfonate, lauric acid, palmitic acid, myristic acid, and stearic acid.
As the polymeric anionic surfactant, the above-mentioned anionic polymeric surfactant is preferred.

Further, as the cationic surfactant, for example, amine salt or ammonium salt type surfactants are preferable.

By adding a surfactant, the charge of the charged ultrafine colloidal particles is neutralized and the hydrophilic surface is converted to hydrophobic. Therefore, an anionic surfactant is used when the colloid particles are positively charged, and a cationic surfactant is used when the colloid particles are negatively charged. Typically, the surfactant has a concentration of 10-' to l O-'mol/I;! ,
It is used as an aqueous solution. The amount of surfactant added varies depending on the amount of colloidal particles, but is preferably 10-2 to 5% by weight. If the amount of surfactant added is too small, the charge on the colloidal particles will not be neutralized, and if it is too large, oriented adsorption of the hydrophobic groups of the surfactant will occur, causing the colloidal particles to be charged, which will hinder the next process. Since it becomes difficult for the surfactant to migrate into the organic solvent, the amount of surfactant added should be set to the point at which the ultrafine colloidal particles are completely agglomerated.

Next, in the process (3), an organic solvent that is hardly soluble in water is added to the aggregate obtained in the process (2) to transfer the ultrafine particles into the organic solvent, and then the water is separated. It is a process to prepare transparent organocolloids.

The organic solvent to be used is appropriately determined depending on the type of surfactant used in the process (2), but examples include toluene, xylene, cyclohexane, benzene, hexane,
Carbon tetrachloride, chloroform, pentane, cyclohexanone, ethylmethylketone, phenylmethanol, cyclohexanol, butanol, trichloroethylene, etc. can be used.

The amount of organic solvent used is 0.2 to 2 times the total volume of the reaction solution.
Double is preferred.

By adding the above-mentioned organic solvent to the aqueous solution containing the aggregate obtained in (2) and stirring, the ultrafine particles are transferred into the organic solvent. Thereafter, water is separated by means such as a normal liquid separation operation to obtain a transparent organocolloid.

Next, the process (4) is a process of removing the organic solvent in the organocolloid obtained in the process (3).

Here, the organic solvent may be completely removed to form ultrafine particles in the form of a powder, or a portion may be removed, that is, concentrated to form a paste.

Concentration or separation of the organic solvent can be easily carried out using conventional means, such as vacuum distillation with or without heating. There is no risk of agglomeration of ultrafine particles due to desorption.

By the method of the present invention described above, the particle radius is 150 Å.
Below, preferably 100 Å or less, more preferably 5
Ultrafine particles of metal sulfides, metal selenides, or mixed crystals thereof having a particle size of 0 Å or less can be obtained.

The ultrafine particles thus obtained have high transparency because they are ultrafine particles, and are extremely well dispersed in organic binders, polymers, etc., so they can be used as optical functional materials.

(Example) The present invention will be explained below with reference to Examples.

Example 1 (a) Cd504 of 8.9x 10-'mat/Q
60 ml of aqueous solution.

(b) 4, 5x 10 containing 0.07i mass% of maleic anhydride/styrene copolymer as a particle growth inhibitor
"3 mol/12 (NH-), S aqueous solution (pH 3)
The mixture was added dropwise little by little to 250 ml while stirring deeply. At this time, the temperature of the aqueous solution was 23°C.

This colloid was added with 2×1O as an anionic surfactant.
180 ml of sodium dodecylbenzenesulfonate aqueous solution of ~"mol/Q was added to aggregate the CC15 colloid.

Next, 30% xylene was added to the aqueous solution containing this aggregate.
After adding 0 ml of the mixture and shaking it vigorously to transfer the CdS ultrafine particles to the xylene phase, water was removed by a liquid separation operation.

In this way, the ultrafine particles of CdS were completely dispersed in xylene, and a transparent organocolloid was obtained. The organocolloid was heated to 50°C in a water bath, and the xylene was distilled off under reduced pressure at 30 mmHg to concentrate it and form a paste. CdS ultrafine particles were obtained. Further, by completely removing xylene, powdered CdS ultrafine particles were obtained. The particle radius of the generated CdS was 28 when measured using a transmission electron microscope.

Example 2 (a) Zn(
45 ml of CffO4)z aqueous solution, (b) 2 X 10-3 mol / (N a of 2
The mixture was added dropwise little by little to 1800 ml of HS water solution (pH 8) with careful stirring. At this time, the temperature of the aqueous solution was 20°C.

This colloid contains 2, 5 as anionic surfactants.
750 ml of an aqueous solution of sodium laurate of 3 mol/f2 was added to collect the ZnS colloid.

Next, 12 toluene was added to the aqueous solution containing this aggregate.
00ml was added and vigorously shaken to transfer the ZnS ultrafine particles to the toluene phase, and then water was removed by a liquid separation operation.

In this way, the ZnS ultrafine particles were completely dispersed in toluene, and a transparent organocolloid was obtained.

This organocolloid was heated to 50°C in a water bath and heated to 90°C.
Powdered ZnS ultrafine particles were obtained by distillation under reduced pressure of 1 to 1 mmHg. The particle radius of the generated ZnS was measured using a transmission electron microscope and was found to be 30. Ultrafine particles can be obtained.

These ultrafine particles obtained according to the present invention are useful as catalysts or photo-enhancing agents for photochemical reactions related to the conversion and storage of light energy, and optoelectronic functional materials for electrophotographic photoreceptors, nonlinear optical materials, piezoelectric materials, and the like.

Claims (1)

[Scope of Claims] (a) An aqueous solution containing one or more of Cd, Zn, Pb, Ga, In, Ge, Sn or Cu ions;
and (b) an aqueous solution containing a compound that supplies S and/or Se ions and whose pH is adjusted to 2 to 12 is mixed and stirred, and a metal sulfide, metal selenide or After preparing a colloid of these mixed crystals, adding an ionic surfactant to the colloid and causing it to aggregate, add an organic solvent that is sparingly soluble in water to the aggregate to disperse and transfer the ultrafine particles into the organic solvent. , a metal sulfide with a particle radius of 150 Å or less, characterized in that water is separated to prepare a transparent organocolloid, and the organic solvent in the organocolloid is further removed;
A method for producing ultrafine particles of metal selenides or mixed crystals thereof.