JP2005343782A - Method for producing bismuth telluride nanoparticle and method for producing tellurium nanoparticle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a stable bismuth telluride (Bi<SB>2</SB>Te<SB>3</SB>) nanoparticle. <P>SOLUTION: The method for producing the bismuth telluride nanoparticle comprises: a process of preparing a first solution by dissolving bismuth chloride (BiCl<SB>3</SB>) in a solvent; a process of preparing a second solution by dissolving a polymer as a protective agent in the solvent; a process of preparing a third solution by adding the second solution to the first solution and, furthermore, adding the solvent to the mixture of the solutions; a process of preparing a fourth solution by dissolving an alkali metal hydroxide in water (H<SB>2</SB>O); a process of preparing a fifth solution by adding the fourth solution to the third solution; a process of putting tellurium (Te), a reducing agent, and the fifth solution into a pressure-resistant container and sealing the container with a lid and carrying out a reduction reaction while agitating the content of the container; and a process of lowering temperatures to room temperature while agitating the content after the completion of the reduction reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing bismuth telluride nanoparticles and a method for producing tellurium nanoparticles that can be used in the method for producing bismuth telluride nanoparticles.

In recent years, research on thermoelectric conversion materials has become active. The first reason is related to global environmental problems. When thermoelectric conversion materials are used, power can be extracted using low-grade heat that was previously discarded, saving fossil fuel and unit energy. Reduction of CO ₂ emission per conversion is theoretically possible. The second reason is that the problem of heat dissipation of semiconductor chips that have been miniaturized has become apparent. That is, thermoelectric conversion based electronic cooling has no moving parts, is highly reliable, and can be downsized. Therefore, the need for highly functional thermoelectric conversion materials is also increasing in this region. It depends.

Here, bismuth telluride (Bi ₂ Te ₃ ) is widely known as a low-temperature thermoelectric conversion material that operates at 200 ° C. or less, and is often used in heat sensors and thermoelectric cooling devices.
The general method for producing bismuth telluride (Bi ₂ Te ₃ ) is a heat-melting method in which a single metal is melted at a very high temperature. For a long time and at a high temperature under special conditions so as not to cause oxidation. Therefore, it is not easy to obtain a chemically uniform material.

On the other hand, Non-Patent Document 1 discloses a new method for producing bismuth telluride (Bi ₂ Te ₃ ).
The outline of this manufacturing method is as follows.

A mixture of bismuth chloride dihydrate (BiCl ₃ · 2H ₂ O), tellurium (Te) powder, potassium hydroxide (KOH), and potassium boron hydroxide (KBH ₄ ) is placed in an autoclave. The autoclave is filled to 90% with dimethylformamide (DMF), maintained at 100 to 180 ° C. for 10 to 50 hours, and then cooled to room temperature by natural cooling. It is then filtered and washed sequentially with distilled water and ethanol. Finally, the black product is dried at 80 ° C.

Further, in this Non-Patent Document 1, the product obtained by heating at 100 ° C. for 24 hours is a nanoparticle having an average width of 10 nm and a length of 150 nm, and obtained under the conditions of 180 ° C. and 15 hours. The products were nanoparticles with a particle size of 20-40 nm, and both products were reported to be bismuth telluride (Bi ₂ Te ₃ ).

Journal “Journal of Physics and Chemistry of Solids”, Volume 63 (2002), Page 2119-2121 (Yuan Deng et al)

However, the inventors of the present invention have tried the production method of bismuth telluride (Bi ₂ Te ₃ ) disclosed in Non-Patent Document 1 described above. As a result, the obtained product is unstable, agglomerated, and nano-sized. It was difficult to obtain bismuth telluride (Bi ₂ Te ₃ ).

Accordingly, the present invention is to propose a method for producing nanoparticles of a stable bismuth telluride (Bi ₂ Te ₃₎ as a first problem, tellurium (Te), which can be used in the production method of the telluride Bisumasunano particles A second problem is to propose a method for producing nanoparticles.

The first problem described above has been solved by the method for producing nanoparticles of bismuth telluride (Bi ₂ Te ₃ ) according to claim 1 or claim 19.
Specifically, a process of preparing a first solution by dissolving bismuth chloride (BiCl ₃ ) in a solvent, a process of preparing a second solution by dissolving a polymer as a protective agent in the solvent, and the second process described above. A process of adding a solution to the first solution and further adding the solvent to make a third solution, and a process of completely dissolving an alkali metal hydroxide in water (H ₂ O) to make a fourth solution And adding the fourth solution to the third solution to make a fifth solution, and putting tellurium (Te), a reducing agent and the fifth solution in a pressure vessel and sealing with a lid. This has been solved by a method for producing bismuth telluride nanoparticles, which comprises a step of performing a reduction reaction while stirring the inside of a pressure vessel and a step of lowering the temperature to room temperature while stirring after the completion of the reduction reaction.
Also, a first solution is prepared by dissolving an organometallic bismuth compound containing bismuth (Bi) in a solvent, and a second solution is prepared by dissolving an organometallic tellurium compound containing tellurium (Te) in the solvent. ) In a solvent to form a third solution, a process of mixing them, a process of substituting the atmosphere with nitrogen before or after mixing them, and sodium borohydride (NaBH ₄ ) as the solvent To make a fourth solution by dissolving it in a bubble of nitrogen gas, dropping the fourth solution into the solution that has undergone the mixing process and the nitrogen substitution process, and stirring after completion of the dropping The process, the process of raising the temperature to at least the boiling point of the solvent while stirring, the process of reacting, the process of lowering the temperature to room temperature with stirring after the reaction, and the obtained black solution on a filter under nitrogen replacement. The steps that, after collecting the resulting solution, the solution was evaporated and resolved by the method for producing telluride Bisumasunano particles comprising the steps for drying.

The second problem described above has been solved by the method for producing tellurium (Te) nanoparticles according to claim 11 or claim 15.
Specifically, a process of making an alkaline substance solution by dissolving an alkaline substance in water (H ₂ O), a process of putting tellurium (Te) into the alkaline substance solution, and a reducing agent and a protective agent in the solvent The process of making a solvent by dissolving the above polymer, the process of quickly adding and stirring the solvent after the alkaline substance solution containing the tellurium (Te) has turned purple, and heating the liquid until the color changes This has been solved by a method for producing tellurium nanoparticles including a refluxing process.
Also, a process of making the first solution by stirring the tellurium (Te) raw material and absolute ethanol (EtOH), and stirring the absolute ethanol (EtOH) and the polymer as the protective agent to make the second solution Tellurium nanoparticles comprising: a step of adding a second solution to the first solution and stirring to make a third solution; and adding an alkali borohydride to the third solution and stirring It was solved by the manufacturing method.

  Furthermore, the tellurium nanoparticles produced by the above-described method have been solved by a method for producing bismuth telluride nanoparticles used as tellurium (Te) added to the fifth solution in claim 1.

According to the above-described method for producing bismuth telluride nanoparticles according to the present invention, nano-sized bismuth telluride (Bi ₂ Te ₃ ) having a uniform structure can be produced. At this time, the particle size of the resulting nano-sized bismuth telluride (Bi ₂ Te ₃ ) can be controlled by adjusting the amount of the polymer protective agent.
Further, according to the above-described method for producing tellurium nanoparticles according to the present invention, tellurium (Te) nanoparticles that can be used for producing the nano-sized bismuth telluride (Bi ₂ Te ₃ ) are stably produced. Can be manufactured.
Furthermore, by using the tellurium (Te) nanoparticles produced by the above-described method for producing tellurium nanoparticles according to the present invention in the above-described method for producing bismuth telluride nanoparticles according to the present invention, nanostructures having a more uniform structure can be obtained. Size bismuth telluride (Bi ₂ Te ₃ ) can be produced more stably.

Hereinafter, preferred embodiments of the above-described method for producing nano-sized bismuth telluride (Bi ₂ Te ₃ ) according to the present invention and the method for producing nano-sized tellurium (Te) that can be used in the method according to the present invention will be described. Describe the form.

[Production Method of Bismuth Telluride Nanoparticles (Part 1)]
A list of reaction reagents used in the production of bismuth telluride nanoparticles is shown in Table 1.

First, 4.2 mg of bismuth chloride (BiCl ₃ ) is dissolved in 10 mL of dimethylformamide (hereinafter abbreviated as “DMF”) to form a first solution, and polyvinylpyrrolidone which is a polymer that functions as a protective agent (Hereinafter abbreviated as “PVP”) 36.7 mg (R = 10), 146.7 mg (R = 40), or 367 mg (R = 100), or polyethyleneimine (hereinafter abbreviated as “PEI”). ) Are dissolved in 10 mL of DMF to make the second solution.
In this example, DMF is used as the solvent, but other solvents can also be used. Moreover, although PVP or PEI was used for the polymer that functions as a protective agent, the polymer that functions as a protective agent is not limited to these, and weak coordination bonds with bismuth (Bi) and tellurium (Te) are possible. Any other polymer that can be dissolved in the solvent can be used as a protective agent. For example, polyacrylic acid, polyvinylamine, and analogs thereof can be used.

Subsequently, each of the first and second solutions was stirred for 30 minutes or longer, and after being well conditioned, the second solution (PVP or PEI was dissolved) in the first solution (solution in which BiCl ₃ was dissolved). Solution) is added to make a third solution, and 30 mL of DMF solvent is further added, and the mixture is well-mixed by stirring for 3 hours or more.

Separately, 11.9 mg of potassium hydroxide (KOH) is completely dissolved in ₂ mL of water (H ₂ O) to make a fourth solution, and this fourth solution is added to the third solution to add a fifth Make a solution. At this time, the solvent turns yellow.
In this example, potassium hydroxide (KOH) is used as the alkali metal hydroxide, but other alkali metal hydroxides such as sodium hydroxide (NaOH) can also be used.

Subsequently, 2.5 mg of tellurium (Te) powder and 4.2 mg of potassium borohydride (KBH ₄ ) as a reducing agent were placed in a pressure vessel, and the fifth solution (BiCl ₃ solution) was further placed in this pressure vessel. ) And close it tightly with a lid.
Here, the molar ratio of bismuth chloride (BiCl ₃ ) to tellurium (Te) is the same as the molar ratio of bismuth (Bi) to tellurium (Te) in bismuth telluride (Bi ₂ Te ₃ ), and is almost 2: 3. Adjust so that

  Subsequently, the temperature is raised while stirring in the pressure vessel, and a reduction reaction is performed for 17 hours. The temperature of the reduction reaction is preferably in the temperature range of 80 to 250 ° C, preferably 140 to 190 ° C, more preferably 160 to 180 ° C, and most preferably about 170 ° C.

  After the reduction reaction is completed, the temperature in the pressure vessel is lowered to room temperature while stirring to obtain a black solution.

As a result of analyzing the obtained product with an energy dispersive X-ray fluorescence spectrometer (EDX), it was confirmed that every particle contained elements of bismuth (Bi) and tellurium (Te), and an X-ray diffractometer (XRD). ) Analysis revealed that these bismuth telluride (BiCl ₃ ) particles have a trigonal structure.

The ratio R (= M2 / M1) of the number of moles of the polymer as a protective agent (M2) to the sum of the number of moles of bismuth chloride (BiCl ₃ ) and tellurium (Te) (M1) Although R = 10, 40, and 100, it was confirmed by other tests that nanoparticles were generated in the range of 0.1 <R <1000. However, the particle size of the colloidal particles changes depending on the amount of the polymer (PVP, PEI, etc.) that functions as a protective agent.

  That is, when a protective agent is not used, and when PEI is used as a protective agent and the ratio R is R = 10, R = 40, R = 100, a transmission electron microscope (TEM) of each generated fine particle FIGS. 1 to 4 show photographs according to the above.

FIG. 1 shows the case where no protective agent is used. In this case, the particle diameter of the fine particles is about several hundreds of nanometers and is considerably agglomerated. On the other hand, when the amount of the protective agent is increased to R = 10, 40, 100, as can be seen from FIGS. That is, the average particle diameter at R = 10 was 40 nm, the average particle diameter at R = 40 was 16 nm, and the average particle diameter at R = 100 was 13 nm.
Moreover, although cohesion still remains at R = 10, dispersibility is improved by increasing R with R = 40 and R = 100.

  Thus, in the method for producing bismuth telluride nanoparticles according to the present invention, there is an advantage that the particle size of the fine particles can be controlled using the protective agent.

[Production Method of Bismuth Telluride Nanoparticles (Part 2)]
The inventors of the present invention have advanced research and further developed the following nanoparticle production method. Three preferred embodiments of this method are disclosed. In this specification, the methods according to these three embodiments are referred to as method A, method B, and method C, respectively. Table 2 shows a list of reaction reagents commonly used in the embodiments of the nanoparticle production method (Method A, Method B, Method C).

The solvent used in the embodiment of the method for producing three nanoparticles (Method A, Method B, Method C) can heat the nanoparticles under a reducing atmosphere such as ethanol, butanol, pentanol, hexanol, ethylene glycol, or the like. 100 ° C, resistant to decomposition during reduction of solvent or potassium borohydride (KBH ₄ ) such as 1,2 Diethoxyethane, Diethylene glycol diethylene ether, etc. Solvent dispersible at the above temperatures (for heat treatment).

  The first preferred embodiment (Method A) is as follows.

Procedure 1: BiCl ₃ or (C ₂ H ₃ O ₂ ) ₃ Bi is dissolved in 10 mL of solvent. Dissolve Te (OEt) ₄ or TeCl ₄ in 10 mL of solvent. The polymer (PVP) is dissolved in 10 mL of solvent.
Operation 2: After they are completely dissolved, mix them well and mix well by stirring for 30 minutes or more.
Operation 3: The mixed and stirred solution is charged into a glass container, freeze degassed, and purged with nitrogen.
Operation 4: Separately, dissolve NaBH ₄ in 10 mL of solvent, charge into a dropping funnel, and expose to a nitrogen gas bubble for 10 minutes.
Operation 5: The solution of the above operation 3 is vigorously stirred, and the solution prepared in the above operation 4 is dropped into the solution in 10 minutes to 3 hours.
Operation 6: Stir for 30 minutes after dropping.
Operation 7: The temperature is raised to the boiling point of the solution while stirring, and the reaction is performed over 1 to 12 hours.
Operation 8: After completion of the reaction, the temperature is lowered to room temperature with stirring.
Procedure 9: Apply the resulting black solution to an ultrafilter under nitrogen purge. Thereafter, ethanol washing is performed 3 times using the same operation.
Operation 10: After collecting the obtained solution, the solution is evaporated and dried under reduced pressure at 80 ° C. overnight.

FIG. 5 is a transmission electron micrograph of the bismuth telluride nanoparticles obtained as described above. The particle size distribution is shown later, but in the range of 21.2 ± 3.8 nm in diameter, bismuth telluride (BiCl ₃ ) Nanoparticles could be prepared.

  The second preferred embodiment (Method B) is as follows.

Procedure 1: BiCl ₃ or (C ₂ H ₃ O ₂ ) ₃ Bi is dissolved in 10 mL of solvent. Dissolve Te (OEt) ₄ or TeCl ₄ in 10 mL of solvent. The polymer (PVP) is dissolved in 10 mL of solvent.
Operation 2: After they are completely dissolved, mix them well and mix well by stirring for 30 minutes or more.
Operation 3: The mixed and stirred solution is charged into a glass container, freeze degassed, and purged with nitrogen.
Operation 4: Separately, dissolve NaBH ₄ in 10 mL of solvent, charge into a dropping funnel, and expose to a nitrogen gas bubble for 10 minutes.
Operation 5: The solution of the above operation 3 is vigorously stirred, and the solution prepared in the above operation 4 is dropped into the solution in 10 minutes to 3 hours.
Operation 6: Stir for 30 minutes after dropping.
Operation 7: The solution of the above operation 6 is put in a pressure vessel under a nitrogen atmosphere.
Operation 8: While stirring in a pressure vessel, the temperature is raised to the boiling point of the solution + 30 ° C., and the reaction is performed for 17 hours.
Step 9: After completion of the reaction, the temperature is lowered to room temperature while stirring.
Procedure 10: Apply the resulting black solution to an ultrafilter under nitrogen purge. Thereafter, ethanol washing is performed 3 times using the same operation.
Operation 11: After collecting the obtained solution, the solution is evaporated and dried under reduced pressure at 80 ° C. overnight.

FIG. 6 is a transmission electron micrograph of bismuth telluride nanoparticles obtained as described above (using ethylene glycol as the solvent). In this case, the particle size distribution is shown later, but the diameter of the nanoparticles was very large, 110.5 ± 22.9 nm. By adjusting the nanoparticles in this way, the crystallinity of bismuth telluride (Bi ₂ Te ₃ ) is greatly improved. The larger the crystallinity, the better the properties as a thermoelectric conversion material. On the other hand, when used as various thermoelectric elements, a smaller particle size is advantageous.

  A third preferred embodiment (Method C) is as follows.

Procedure 1: BiCl ₃ or (C ₂ H ₃ O ₂ ) ₃ Bi is dissolved in 10 mL of solvent. Dissolve Te (OEt) ₄ or TeCl ₄ in 10 mL of solvent. The polymer (PVP) is dissolved in 10 mL of solvent.
Operation 2: After they are completely melted, they are all charged into a glass container, freeze degassed, and then purged with nitrogen.
Operation 3: Separately, dissolve NaBH ₄ in 10 mL of solvent, charge into a dropping funnel, and expose to a nitrogen gas bubble for 10 minutes.
Operation 4: The solution of the above operation 3 is gently stirred, and the solution prepared in the above operation 4 is dripped completely in several seconds. Operation 5: After completion of the addition, the solution is stirred for 30 minutes.
Operation 6: The temperature is raised to the boiling point of the solution while stirring, and the reaction is allowed to proceed for 7 hours.
Operation 7: After completion of the reaction, the temperature is lowered to room temperature with stirring.
Procedure 8: Apply the resulting black solution to an ultrafilter under nitrogen substitution. Thereafter, ethanol washing is performed 3 times using the same operation.
Operation 9: After collecting the obtained solution, the solution is evaporated and dried at 80 ° C. under reduced pressure overnight.

FIG. 7 is a transmission electron micrograph immediately after NaBH ₄ reduction in Method C, showing that small rod-shaped nanoparticles are generated. FIG. 8 is a transmission electron micrograph after heating and refluxing in the method C, and it can be seen that the rod grows by heating.

  In the preferred embodiments of the above-mentioned method A, method B, and method C, the reagents described in Table 2 were used. However, when carrying out the present invention, the following reagents were used instead of those reagents. It is also possible to use a reagent.

Bi samples include bismuth chloride (Bismuth III chloride), bismuth bromide (Bismuth III bromide), bismuth fluoride (Bismuth III fluoride), bismuth iodide (Bismuth III).
iodide), Bismuth acetate, Bismuth III nitrate, Bismuth pentoxide, Trimethylbismuth, Triethylbismuth, Triphenylbismuth ) Organometallic bismuth.

  Te samples include tellurium ethoxylate, dimethyltelluride, diphenyltelluride, dimethyltellurium diiodide, diphenyltellurium dichloride, and chloride. Organometallic tellurium such as trimethyltellurium chloride, triphenyltellurium chloride, tellurium tetrabromide, tellurium tetrachloride, tellurium tetraiodide.

  In the above-described method for producing bismuth telluride nanoparticles (part 2), in any of the embodiments, it is preferable to perform all of these processes in a nitrogen atmosphere. For example, it is preferably performed in a special nitrogen atmosphere chamber of nitrogen.

FIG. 9 is a particle size distribution of the bismuth telluride nanoparticles of FIG. 5 made according to Method A without using a special nitrogen atmosphere chamber, in which case the diameter of the nanoparticles was 21.2 ± 3.8 nm. .
FIG. 10 is a spectrum of the nanoparticles obtained by an energy dispersive X-ray fluorescence analyzer (EDX), which shows that bismuth (Bi) and tellurium (Te) are contained.

FIG. 11 is a particle size distribution of the bismuth telluride nanoparticles of FIG. 6 made according to Method B without using a special nitrogen atmosphere chamber, in which case the diameter of the nanoparticles was 110.5 ± 22.9 nm. .
FIG. 12 is a spectrum of the nanoparticles obtained by an energy dispersive X-ray fluorescence analyzer (EDX), which shows that bismuth (Bi) and tellurium (Te) are contained.

On the other hand, FIG. 13 is a transmission electron micrograph before heat treatment of bismuth telluride nanoparticles obtained according to Method A by performing all processes in a special nitrogen atmosphere chamber.
FIG. 14 shows the particle size distribution of the nanoparticles. In this case, the diameter of the nanoparticles was 4.6 ± 1.3 nm.

FIG. 15 is a transmission electron micrograph after heat treatment of bismuth telluride nanoparticles obtained according to Method A by performing all the steps in a special nitrogen atmosphere chamber (note that the temperature during NaBH ₄ reduction is 20 ° C).
FIG. 16 shows the particle size distribution of the nanoparticles. In this case, the diameter of the nanoparticles was 16.2 ± 23.9 nm.
FIG. 17 shows a spectrum of the nanoparticles obtained by an energy dispersive X-ray fluorescence analyzer (EDX), which shows that bismuth (Bi) and tellurium (Te) are contained.

Comparing these figures, the diameter of the prepared nanoparticles is smaller when the whole process is performed in a nitrogen atmosphere. Similar results were obtained when NaBH ₄ reduction was performed at 0 ° C.

  Further, in the above-described method for producing bismuth telluride nanoparticles (part 2), the solvent before the temperature increase in operation 7 of method A, operation 8 of method B, and operation 6 of method C is changed from ethanol to butanol, pentanol, ethylene・ Substitute with glycol, then raise the temperature and test to prepare nanoparticles in the same way. The results are as follows.

  When substituted with butanol and refluxed at 130 ° C. for 10 hours, the particle size was large and the colloid was unstable. When substituted with pentanol and refluxed at 150 ° C. for 10 hours, the particle size was very large and the colloid was stable. When substituted with ethylene glycol and refluxed at 200 ° C. for 10 hours, the particle size was large and the colloid was unstable.

FIG. 18 is transmission electron micrographs of bismuth telluride nanoparticles prepared under various conditions. (A) NaBH ₄ reduction with solvent ethanol, (B) NaBH ₄ reduction with solvent ethylene glycol and pressure treatment by maintaining at 230 ° C. above the boiling point of solvent, (C) is solvent ethanol When (B) is reduced with NaBH ₄ and refluxed with ethanol (110 ° C.), (D) is when NaBH _{4 is} reduced with solvent ethanol and refluxed with ethylene glycol (230 ° C.).
FIG. 19 shows X-ray diffraction intensity distributions corresponding to each, and it can be seen that the smaller the particle diameter, the weaker the peak, and the larger the particle diameter, the stronger the peak.

The composition ratio of bismuth (Bi) and tellurium (Te) in the above-described method for producing bismuth telluride nanoparticles (Part 2) can be freely changed by changing the ratio of the amount of charged materials. This is because it is an alloy. In the above-described embodiment, the case where the ratio is 2: 3 has been described.
Furthermore, this nanoparticle production method (part 2) can be carried out by replacing bismuth (Bi) with platinum (Pt) or palladium (Pd). In this case, platinum telluride particles or Nanoparticles of palladium telluride can be made.

  Next, a preferred embodiment of a method for producing tellurium (Te) nanoparticles that can be used in the method for producing bismuth telluride nanoparticles described above will be described.

[Method for producing tellurium nanoparticles (part 1)]
A list of reaction reagents used in the production of tellurium nanoparticles is shown in Table 3.

First, an alkaline substance (KOH or NaOH) is dissolved as much as possible (659.9 mg) in 2 mL of water (H ₂ O) to form a first solution (alkaline substance solution).

  Subsequently, 4.2 mg of tellurium (Te) powder is put into the first solution.

Separately, 2.1 mg of potassium borohydride (KBH ₄ ) and 146.7 mg of PVP are dissolved in 50 mL of DMF to make a second solution (solvent).

  Subsequently, when the first solution turns purple, the second solution is added quickly and stirred vigorously.

The temperature is then raised and heated to reflux until the color changes.
The heating reflux temperature is preferably in the temperature range of 80 to 250 ° C, preferably 140 to 190 ° C, more preferably 160 to 180 ° C, and particularly preferably about 170 ° C.

Immediately after the heating and reflux, the color is black-brown, but after one day, it becomes charcoal and tends to cause white precipitation after two days. Therefore, it is preferably used for the production of bismuth telluride nanoparticles during the black-brown.
In addition, although the color is better to make in a pressure vessel, it has the same tendency.

  As described above, tellurium (Te) nanoparticles used for producing bismuth telluride nanoparticles can be produced.

[Method for producing tellurium nanoparticles (2)]
A list of reaction reagents used in the production of tellurium nanoparticles is shown in Table 4.

First, 6 mg of tetraethoxytellurium (Te (OEt) ₄ ) is put in a container, and 10 mL of anhydrous ether (EtOH) is added thereto to make a first solution, which is stirred for 30 minutes or more.
In this example, tetraethoxytellurium (Te (OEt) ₄ ) was used as the raw material for tellurium (Te), but other tellurium alkoxides, tellurium chloride (TeCl ₄ ), and tellurium bromide (TeBr ₄ ) were used. , Iodine tellurium (TeI ₄ ), or telluric acid (Te (OH) ₆ ) may be used.

  Separately, add 73.4 mg of PVP in 10 mL of anhydrous ether (EtOH) to make a second solution and stir for more than 30 minutes.

Subsequently, the second solution (PVP solution) is added to the first solution (Te (OEt) ₄ solution) to form a third solution, which is stirred for 30 minutes or more.

Subsequently, 2.5 mg of sodium borohydride (NaBH ₄ ) powder is added to the third solution and stirred.

  Also by the above method, tellurium (Te) nanoparticles that can be suitably used for producing bismuth telluride nanoparticles are produced.

  The tellurium (Te) nanoparticles obtained as described above were dispersed in a liquid and seemed to be a transparent liquid.

[Method of producing bismuth telluride nanoparticles using tellurium nanoparticles]
A list of reaction reagents used in the production of bismuth telluride nanoparticles is shown in Table 5.

First, 4.2 mg of bismuth chloride (BiCl ₃ ) is dissolved in 10 mL of DMF to make a first solution, and 146.7 mg of PVP, which is a polymer that functions as a protective agent, is dissolved in 10 mL of DMF. make.

Subsequently, each of the first and second solutions was stirred for 30 minutes or longer, and after being well conditioned, the second solution (PVP or PEI was dissolved) in the first solution (solution in which BiCl ₃ was dissolved). Solution) is added to make a third solution, and 30 mL of DMF solvent is further added, and the mixture is well-mixed by stirring for 3 hours or more.

  Separately, colloidal solutions containing each tellurium nanoparticle are prepared with the reagent addition amounts shown in Tables 6 and 7 using the above-described method of producing tellurium nanoparticles (Part 1 and Part 2).

Subsequently, the above-prepared BiCl ₃ solution is placed in a pressure vessel, and a colloidal solution containing tellurium nanoparticles is added thereto using a glass syringe, which is closed in an airtight state with a lid.
Here, the molar ratio of bismuth chloride (BiCl ₃ ) to tellurium (Te) is the same as the molar ratio of bismuth (Bi) to tellurium (Te) in bismuth telluride (Bi ₂ Te ₃ ), and is almost 2: 3. Adjust so that

  Subsequently, the temperature is raised while stirring in the pressure vessel, and a reduction reaction is performed for 17 hours. The temperature of this reduction reaction is preferably about 170 ° C.

After the reduction reaction is completed, the temperature in the pressure vessel is lowered to room temperature while stirring to obtain a black solution.
This solution was a solution in which nano-sized bismuth telluride (BiCl ₃ ) was stably dispersed.

  As mentioned above, although the suitable embodiment of the manufacturing method of the bismuth telluride nanoparticle concerning the present invention and the manufacturing method of tellurium nanoparticle was described, the present invention is not limited to the above-mentioned embodiment at all, Naturally, various modifications and changes are possible within the scope of the technical idea of the present invention described in the claims.

_{2 is} a transmission electron micrograph of bismuth telluride (Bi ₂ Te ₃ ) nanoparticles prepared by the method of the present invention (Part 1) without using a protective agent. Under conditions ratio R of R = 10 of the protective agent is a transmission electron micrograph of nanoparticles of bismuth telluride made by the method of the present invention (Part _{1) (Bi 2 Te 3)} . _{2 is} a transmission electron micrograph of nanoparticles of bismuth telluride (Bi ₂ Te ₃ ) produced by the method of the present invention (Part 1) under the condition that the ratio R of the protective agent is R = 40. Under conditions ratio R of R = 100 of the protective agent is a transmission electron micrograph of nanoparticles of bismuth telluride made by the method of the present invention (Part _{1) (Bi 2 Te 3)} . The method of the present invention is a transmission electron micrograph of nanoparticles of bismuth telluride method made by A (Part _{2) (Bi 2 Te 3)} . FIG. _{3 is} a transmission electron micrograph of nanoparticles of bismuth telluride (Bi ₂ Te ₃ ) produced by Method B of Method 2 of the present invention (using ethylene glycol as solvent). The method of the present invention is a transmission electron micrograph of after NaBH ₄ reduction of nanoparticles bismuth telluride made by Method C (Part _{2) (Bi 2 Te 3)} . The method of the present invention is a transmission electron micrograph after heating to reflux of nanoparticles bismuth telluride made by Method C (Part _{2) (Bi 2 Te 3)} . 6 is a particle size distribution of the bismuth telluride nanoparticles of FIG. 5 prepared according to method A of the method of the present invention (part 2) without using a special nitrogen atmosphere chamber. It is the spectrum by the energy dispersive X-ray fluorescence analyzer of the bismuth telluride nanoparticle of FIG. 5 produced according to the method A of the method (the 2) of this invention, without using a special nitrogen atmosphere chamber. FIG. 7 is a particle size distribution of the bismuth telluride nanoparticles of FIG. 6 prepared according to method B of the method of the present invention (part 2) without using a special nitrogen atmosphere chamber. It is the spectrum by the energy dispersive X-ray fluorescence analyzer of the bismuth telluride nanoparticle of FIG. 6 produced according to the method B of the method (the 2) of this invention, without using a special nitrogen atmosphere chamber. It is the transmission electron micrograph before heat processing of the bismuth telluride nanoparticle which performed all the processes in the special nitrogen atmosphere chamber and was prepared according to the method A of the method (the 2) of this invention. It is the particle size distribution before the heat treatment of the bismuth telluride nanoparticles prepared according to the method A of the method (Part 2) of the present invention by performing all the processes in a special nitrogen atmosphere chamber. It is a transmission electron micrograph after the heat processing of the bismuth telluride nanoparticle made according to the method A of the method (the 2) of this invention, performing all the processes in a special nitrogen atmosphere chamber. It is the particle size distribution after heat treatment of bismuth telluride nanoparticles obtained according to method A of the method of the present invention (part 2) by performing all the processes in a special nitrogen atmosphere chamber. It is the spectrum by the energy dispersive X-ray fluorescence analyzer after the heat processing of the bismuth telluride nanoparticle obtained according to the method A of the method (the 2) of this invention, performing all processes in a special nitrogen atmosphere chamber. It is a transmission electron micrograph of the bismuth telluride nanoparticle produced on various conditions. 2 is an X-ray diffraction intensity distribution of bismuth telluride nanoparticles prepared under various conditions.

Claims (26)

A process of dissolving bismuth chloride (BiCl ₃ ) in a solvent to form a first solution, a process of dissolving a polymer as a protective agent in the solvent to form a second solution, and the second solution to the first solution. In addition to the above solution, the above-mentioned solvent is further added to make a third solution, the alkali metal hydroxide is dissolved in water (H ₂ O) to make a fourth solution, and the above-mentioned fourth solution Is added to the third solution to make a fifth solution, while tellurium (Te), a reducing agent, and the fifth solution are put in a pressure vessel and the inside of the pressure vessel is stirred in a sealed state. A method for producing bismuth telluride nanoparticles, comprising: a step of performing a reduction reaction; and a step of lowering the temperature to room temperature while stirring after completion of the reduction reaction.   The method for producing bismuth telluride nanoparticles according to claim 1, wherein the solvent is dimethylformamide (DMF).   2. The tellurization according to claim 1, wherein the polymer as the protective agent is a polymer capable of weak coordination bond with bismuth (Bi) and tellurium (Te) and soluble in the solvent. A method for producing bismuth nanoparticles.   2. The production of bismuth telluride nanoparticles according to claim 1, wherein the polymer as the protective agent is polyvinyl pyrrolidone, polyethyleneimine, polyacrylic acid, polyvinylamine, or an analog thereof. Method.   The method for producing bismuth telluride nanoparticles according to claim 1, wherein the alkali metal hydroxide is potassium hydroxide (KOH). The method for producing bismuth telluride nanoparticles according to claim 1, wherein the reducing agent is potassium borohydride (KBH ₄ ).   The method for producing bismuth telluride nanoparticles according to claim 1, wherein the reduction reaction is performed at a temperature of 80 to 250 ° C. The method for producing bismuth telluride nanoparticles according to claim 1, wherein the molar ratio of the bismuth chloride (BiCl ₃ ) to the tellurium (Te) is adjusted to approximately 2: 3. The ratio R (= M2 / M1) of the number of moles of the polymer (M2) to the sum (M1) of the number of moles of the bismuth chloride (BiCl ₃ ) and the tellurium (Te) is 0.1 <R <1000. The method for producing bismuth telluride nanoparticles according to claim 1, wherein   The method for producing bismuth telluride nanoparticles according to claim 1, wherein the tellurium (Te) is powdered tellurium (Te). The process of making an alkaline substance solution by dissolving an alkaline substance in water (H ₂ O), the process of adding tellurium (Te) to the alkaline substance solution, and dissolving a reducing agent and a polymer as a protective agent in the solvent. A process of making a solvent, a process of quickly adding and stirring the solvent after the alkaline substance solution containing the tellurium (Te) turns purple, and a process of heating and refluxing the liquid until the color changes. A method for producing tellurium nanoparticles, comprising:   The tellurium nanoparticles according to claim 11, wherein the alkaline substance is potassium hydroxide (KOH) or sodium hydroxide (NaOH), and the tellurium (Te) is powdered tellurium (Te). Production method. The solvent is dimethylformamide (DMF), the reducing agent is potassium borohydride (KBH ₄ ), and the polymer as the protective agent is polyvinylpyrrolidone, polyethyleneimine, polyacrylic acid, polyvinylamine, and further The method for producing tellurium nanoparticles according to claim 11, wherein the tellurium nanoparticles are any one of the analogs.   The method for producing tellurium nanoparticles according to claim 11, wherein the heating and refluxing is performed at a temperature of 80 to 250 ° C.   A process of making a first solution by stirring tellurium (Te) raw material and absolute ethanol (EtOH), and a process of making a second solution by stirring absolute ethanol (EtOH) and a polymer as a protective agent; And adding the second solution to the first solution and stirring to make a third solution, and adding and stirring the third solution with alkali borohydride. A method for producing tellurium nanoparticles. The tellurium (Te) raw material is tellurium alkoxide such as tetraethoxytellurium (Te (OEt) ₄ ), tellurium chloride (TeCl ₄ ), tellurium bromide (TeBr ₄ ), iodine tellurium (TeI ₄ ), or telluric acid (Te The method for producing tellurium nanoparticles according to claim 15, wherein the method is any one of (OH) ₆ ). The polymer as the protective agent is polyvinylpyrrolidone, polyethyleneimine, polyacrylic acid, polyvinylamine, or any of these analogs, and the alkali borohydride is sodium borohydride (NaBH ₄ ). The method for producing tellurium nanoparticles according to claim 15, wherein:   A method for producing bismuth telluride nanoparticles, wherein the tellurium nanoparticles produced in claim 11 or 15 are used as tellurium (Te) added to the fifth solution in claim 1. A first solution is prepared by dissolving an organometallic bismuth compound containing bismuth (Bi) in a solvent, a second solution is prepared by dissolving an organometallic tellurium compound containing tellurium (Te) in the solvent, and a polymer (PVP) is prepared. The process of making a third solution by dissolving in a solvent, the process of mixing them, the process of replacing the atmosphere with nitrogen before or after mixing them, and dissolving sodium borohydride (NaBH ₄ ) in the solvent Forming a fourth solution and exposing it to nitrogen gas bubbles; dropping the fourth solution into the solution that has undergone the mixing process and the nitrogen substitution process; The process of raising the temperature to at least the boiling point of the solvent while stirring, the reaction process, the process of lowering the temperature to room temperature while stirring, and the process of filtering the resulting black solution under nitrogen substitution If, after collecting the resulting solution, the solution is evaporated, characterized in that it comprises a step for drying method telluride Bisumasunano particles.   The above-mentioned organometallic bismuth compounds containing bismuth (Bi) are bismuth chloride, bismuth bromide, bismuth fluoride, bismuth iodide, bismuth acetate. (Bismuth III acetate), Bismuth nitrate (Bismuth III nitrate), Bismuth pentoxide (Bismuth III t-pentoxide), Trimethylbismuth, Triethylbismuth, Triphenylbismuth The method for producing bismuth telluride nanoparticles according to claim 19, wherein   The organometallic tellurium compound containing tellurium (Te) is tellurium ethoxylate (Tellurium IV ethoxide), dimethyltelluride, diphenyltelluride, dimethyltellurium diiodide, diphenyl dichloride. -Tellurium (diphenyltellurium dichloride), trimethyltellurium chloride, triphenyltellurium chloride, tellurium tetrabromide, tellurium tetrachloride, tellurium tetraiodide 20. The method for producing bismuth telluride nanoparticles according to claim 19, wherein the method is any one. The above solvent is a solvent capable of heating nanoparticles under reducing atmosphere such as ethanol, butanol, pentanol, hexanol, ethylene glycol, or 1,2 Diethoxyethane, diethylene glycol diethylene 20. Tellurization according to claim 19, wherein the tellurium is a solvent dispersible at a temperature of 100 ° C. or higher, which is not easily decomposed during sodium borohydride (NaBH ₄ ) reduction, such as ether (Diethylene glycol diethyl ether). A method for producing bismuth nanoparticles.   20. The method for producing bismuth telluride nanoparticles according to claim 19, wherein in the reaction process, the temperature is increased by placing the container in a pressure resistant container under a nitrogen-substituted atmosphere.   The method for producing bismuth telluride nanoparticles according to claim 19, wherein in the reaction step, the boiling point of the solution is raised to about + 30 ° C.   20. The method for producing bismuth telluride nanoparticles according to claim 19, wherein all the processes are performed in a nitrogen atmosphere. The platinum telluride particles or the palladium telluride nanoparticles are produced according to the process corresponding to claim 19 using platinum (Pt) or palladium (Pd) instead of the bismuth (Bi) of claim 19. A method for producing nanoparticles.

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