阅读说明：本技术 一种pH调控碲化铋纳米线的制备方法 (Preparation method of pH-regulated bismuth telluride nanowire ) 是由 王金忠 赵晨晨 王东博 于 2021-10-20 设计创作，主要内容包括：一种pH调控碲化铋纳米线的制备方法,属于功能纳米材料形貌调控技术领域。所述方法为：采用氯化铋、亚碲酸钾作为Bi-(2)Te-(3)纳米线的Bi源和Te源,加入去离子水,搅拌处理10～30min,充分混匀后,加入葡萄糖,室温下搅拌备用；在搅拌和冷水浴的条件下,滴加酸液控制溶液的pH在0～6；将溶液置于聚四氟乙烯内衬中将内衬置于不锈钢反应釜中,反应釜拧紧密封,随后置于烘箱加热；反应结束后,自然冷却至室温,将产物置于离心管中,加入乙醇溶液,随后离心,收集下层沉淀样品,进行多次洗涤,最后干燥即可。本发明的Bi-(2)Te-(3)纳米线产品分散性好、稳定性高、纯度高。整个合成方法绿色环保、相对简单,反应条件温和,安全可靠性好,原料价廉易得,对环境友好。(A preparation method of a pH-regulated bismuth telluride nanowire belongs to the technical field of shape regulation of functional nano materials. The method comprises the following steps: bismuth chloride and potassium tellurite are adopted as Bi 2 Te 3 Adding deionized water into a Bi source and a Te source of the nanowires, stirring for 10-30 min, fully and uniformly mixing, adding glucose, and stirring at room temperature for later use; under the conditions of stirring and cold water bath, dropwise adding an acid solution to control the pH value of the solution to be 0-6; putting the solution into a polytetrafluoroethylene lining, putting the lining into a stainless steel reaction kettle, screwing the reaction kettle tightly and sealing, and then putting the reaction kettle into an oven for heating; and after the reaction is finished, naturally cooling to room temperature, placing the product in a centrifuge tube, adding an ethanol solution, then centrifuging, collecting a lower-layer precipitate sample, washing for multiple times, and finally drying. Bi of the present invention 2 Te 3 The nano-wire product has good dispersibility, high stability and high purity. The whole synthesis method is environment-friendly and relatively simple, the reaction condition is mild,has good safety and reliability, cheap and easily obtained raw materials and is environment-friendly.)

1. A preparation method of a pH-regulated bismuth telluride nanowire is characterized by comprising the following steps: the method comprises the following steps:

step one, respectively adopting bismuth chloride and potassium tellurite as Bi₂Te₃Adding deionized water serving as a solvent into a Bi source and a Te source of the nanowire, stirring for 10-30 min, fully and uniformly mixing, adding a glucose reducing agent, and stirring the prepared mixed solution at room temperature for later use;

step two, slowly dropwise adding an acid solution into the solution under the conditions of stirring and cold water bath, and controlling the pH value of the solution to be 0-6;

placing the mixed solution into a polytetrafluoroethylene lining, placing the lining into a stainless steel reaction kettle, screwing and sealing the reaction kettle, and then placing the reaction kettle into a drying oven for heating to perform hydrothermal reaction;

and step four, after the reaction is finished, naturally cooling the oven to room temperature, opening the kettle for sampling, placing the hydrothermal product into a centrifugal tube, adding an ethanol solution with the volume fraction of 50%, centrifuging, decanting the upper-layer solution, collecting the lower-layer precipitate sample, washing the precipitate sample for multiple times, and finally placing the sample into a vacuum drying oven for drying to obtain a gray black powder product.

2. The method for preparing the pH-regulated bismuth telluride nanowire according to claim 1, which is characterized by comprising the following steps: in the first step, the molar ratio of the Bi source to the Te source is 2:3, the molar ratio of the Bi source to the glucose reducing agent is 0.2: 1 to 5 mmol.

3. The method for preparing the pH-regulated bismuth telluride nanowire according to claim 1, which is characterized by comprising the following steps: in the second step, the acid solution is HCl or H₂SO₄。

4. The method for preparing the pH-regulated bismuth telluride nanowire according to claim 1, which is characterized by comprising the following steps: in the third step, the filling degree of the reaction kettle is 50-80%, the reaction temperature is 150-200 ℃, and the reaction time is 16-32 hours.

5. The method for preparing the pH-regulated bismuth telluride nanowire according to claim 1, which is characterized by comprising the following steps: in the third step, the temperature rise speed in the oven is 4-8 ℃/min.

6. The method for preparing the pH-regulated bismuth telluride nanowire according to claim 1, which is characterized by comprising the following steps: in the fourth step, the drying temperature is 50-80 ℃, and the drying time is 8-16 h.

Technical Field

The invention belongs to the technical field of shape regulation and control of functional nano materials, and particularly relates to a preparation method of a pH-regulated bismuth telluride nanowire.

Background

One-dimensional nanomaterials are considered to be ideal materials for directional electron transport due to their orientation characteristics in a certain direction, and are smallest-dimension structures that can be used for efficient transport of electrons and excitons, such as field effect transistors, resonant tunnel diodes, and other nanoelectronic devices. The one-dimensional nano structure becomes a research hotspot due to the integration of good electrical, optical and chemical properties, and is widely applied to various fields.

Bismuth telluride (Bi) as a typical semiconductor material₂Te₃) Is receiving attention because of its excellent thermoelectric properties. Bi is compared with other semiconductor materials and alloys₂Te₃Has lower thermal conductivity and resistivity, relatively stable physical and chemical properties and relatively simple synthesis conditions, and becomes an important research material in the field of thermoelectric materials. In 2009, Zhang Cheng et al demonstrated Bi by Angle-resolved photoelectron Spectroscopy (ARPES)₂Te₃The nature of topological insulation. As a novel topological insulating material, Bi₂Te₃The assembled structure has the quantum effect and topological insulation characteristics of the one-dimensional nano material, so that the assembled structure has the magical chemical, optical, photoelectric and thermoelectric conversion performances and the like, and has wide application prospects in the fields of photoelectric detection, thermoelectric refrigeration, catalysis, energy storage materials, electrochemical detection, biological photo-thermal physical therapy and the like.

At present, several methods have been reported for synthesizing Bi₂Te₃Materials such as hydrothermal/solvothermal methods, electrochemical deposition, vapor deposition, molecular beam epitaxy, pulsed laser deposition, magnetron sputter deposition, and templating methods, among others. More importantly, Bi₂Te₃The physical and chemical properties of the particles are closely related to the crystal structure, the material composition, the morphological characteristics, the particle size and other factors. Thus, for Bi₂Te₃The regulation and synthesis of the nano material are the key to exert the characteristics of the nano material. The hydrothermal/solvothermal method is relatively green and environment-friendly due to the nearly closed internal reaction environment, good in experimental reproducibility, relatively simple in synthesis method and strong in operability, and is favored by researchers. Existing hydrothermal/solvothermal synthesized Bi₂Te₃The following problems are common to nanomaterials: (1) the product shape is mainly hexagonal nanosheet and plate, and the sample is easy to agglomerate; (2) the synthesis process is comparativelyComplicated, surfactant is needed to assist in Bi synthesis₂Te₃The nano material is selected from polyvinylpyrrolidone (PVP), Cetyl Trimethyl Ammonium Bromide (CTAB), Cetyl Trimethyl Ammonium Chloride (CTAC), Sodium Dodecyl Sulfate (SDS), etc. After the appearance modifiers are added, the appearance modifiers have strong binding force with samples, so that the difficulty of the cleaning process of the product is increased, and the production cost is increased. Meanwhile, because the nano-wire is difficult to completely remove, the nano-wire can cause certain influence on the comprehensive performance (such as surface activity) of a finished product, sometimes some nano-wire structures are required to be added to serve as templates, and the templates are removed through a corrosion method subsequently to construct one-dimensional nano-wires, so that the process is relatively complex; (3) a large amount of organic matters are needed to be used as solvents in conventional synthesis, such as ethylene glycol, oleylamine, oleic acid and the like, reaction waste liquid is unfavorable to the environment and is difficult to treat, and the production cost of the product is invisibly increased. The products obtained by electrochemical deposition are mainly thin films, the reaction conditions are relatively mild, the quality of the thin films is regulated and controlled by various parameters in the electrochemical deposition, and the subsequent optimization process of the quality of the thin films is complicated. The large-size two-dimensional bismuth telluride material prepared by vapor deposition is found to have great selection tendency on a growth substrate through research, and the growth conditions need to be gradually optimized. In addition, the subsequent device application also involves material transfer, and the transfer process also needs to be explored and optimized, so that the process is time-consuming. The molecular beam epitaxy method can obtain a film with a large-size surface and a relatively flat surface and in a nanometer scale, but the operation of process equipment needs very high cost, the cost of the process equipment is high, and the large-scale application in industry is difficult to realize. Magnetron sputtering deposition and pulsed laser deposition require high-purity target materials and accurate control of process parameters, the growth process cost is relatively high, the film quality is also affected by various experimental factors, the process stability is not strong, and the mass production of the film cannot be realized.

The existence of the above problems severely restricts Bi₂Te₃The application of the nano material is practical. Therefore, a simple and easy preparation process with strong controllability is developed and designed to produce the sodium with high purity and high stabilityRice material, for Bi₂Te₃The industrial application of the nano material is particularly important.

Disclosure of Invention

The invention aims to solve the problem of the prior Bi₂Te₃The preparation method of the bismuth telluride nanowire with high stability is provided, and the high-stability Bi is prepared by pH regulation without any morphological modifier in the synthetic process₂Te₃And (3) nano materials.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a pH-regulated bismuth telluride nanowire comprises the following steps:

step one, respectively adopting bismuth chloride and potassium tellurite as Bi₂Te₃Adding deionized water serving as a solvent into a Bi source and a Te source of the nanowire, stirring for 10-30 min, fully and uniformly mixing, adding a glucose reducing agent, and stirring the prepared mixed solution at room temperature for later use;

step two, slowly dropwise adding an acid solution into the solution under the conditions of stirring and cold water bath, and controlling the pH value of the solution to be 0-6;

placing the mixed solution into a polytetrafluoroethylene lining, placing the lining into a stainless steel reaction kettle, screwing and sealing the reaction kettle, and then placing the reaction kettle into a drying oven for heating to perform hydrothermal reaction;

and step four, after the reaction is finished, naturally cooling the oven to room temperature, opening the kettle for sampling, placing the hydrothermal product into a centrifugal tube, adding an ethanol solution with the volume fraction of 50%, centrifuging, decanting the upper-layer solution, collecting the lower-layer precipitate sample, washing the precipitate sample for multiple times, and finally placing the sample into a vacuum drying oven for drying to obtain a gray black powder product.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention regulates and controls the pH value and reaction condition of the reaction solution and carries out operations such as centrifugal separation, washing, drying and the like on the hydrothermal reaction productAs the steps, the Bi with good dispersibility, high stability and high purity is prepared₂Te₃And (4) a nanowire product. The whole synthesis method is environment-friendly, relatively simple, mild in reaction conditions, good in safety and reliability, cheap and easily available in raw materials and environment-friendly.

2. In the aspect of raw material selection, bismuth chloride is specifically selected as a Bi source, and potassium tellurite is selected as a Te source. The two reaction raw materials are prepared into Bi according with a stoichiometric ratio (Bi/Te is 2:3) by adding hydrochloric acid to ensure that the pH of a mixed solution is less than 7, no surfactant or organic solvent is required to be added in the whole hydrothermal process, glucose is used as a weak reducing agent, and the ecological concept of environmental protection is met₂Te₃A nanowire. In the experiment, a template agent and a morphology modifier are not used, so that the production process is simplified, and the cost is reduced.

3. The preparation method of the invention takes the critical environment of high temperature and high pressure as a reaction micro-area in the hydrothermal reaction process. In the whole reaction process, a certain high-temperature high-pressure environment is created through a certain filling degree. At pH < 7, H in solution is reduced by glucose reducing agent⁺Te atoms which are preferentially reduced can be regulated and controlled to be assembled into the Te nano-wire. Then taking Te nano-wire as a template to spontaneously assemble Bi₂Te₃A nanowire structure.

4. According to the invention, after the raw materials are mixed and reacted, a hydrothermal product is treated in a way of naturally cooling to room temperature. It depends mainly on two reasons: firstly, a reaction system needs a stable transition process from high temperature, high pressure to normal temperature and normal pressure so as to avoid the phenomenon that a sample undergoes an Ostwald ripening process due to rapid change of the environment to cause excessive growth or agglomeration of crystals, thereby destroying the original stable nanowire structure; secondly, the safety of experimenters is guaranteed by the natural cooling mode, and experimental accidents caused by the pressure difference between a reaction kettle system and the environment due to high-temperature shock drop are effectively avoided.

5. The invention synthesizes Bi₂Te₃The nano-wire structure is in a mesoscopic scale which is respectively in a nano-micron order, so that the prepared product belongs to a hierarchical mesoscopic structure and simultaneously has larger specific surface area,High stability and good physical and chemical properties, and has wide application prospect in the fields of catalysis, photoelectric detection, energy storage, environmental pollutant treatment and the like.

Drawings

FIG. 1 shows Bi prepared at pH 1 according to the present invention₂Te₃SEM images of nanowire structures;

FIG. 2 shows Bi prepared at pH 1 according to the present invention₂Te₃EDS map of nanowire structures;

FIG. 3 shows Bi prepared by the present invention₂Te₃XRD pattern of nanowire structures;

FIG. 4 shows Bi prepared at pH 2 according to the present invention₂Te₃SEM images of nanowire structures;

FIG. 5 shows Bi prepared without pH control of the solution with acid solution₂Te₃SEM image of nanowire structure.

Detailed Description

The technical solutions of the present invention are further described below with reference to the drawings and the embodiments, but the present invention is not limited thereto, and modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

The first embodiment is as follows: the embodiment describes a method for preparing a bismuth telluride nanowire through pH regulation, which comprises the following steps:

step one, respectively adopting bismuth chloride and potassium tellurite as Bi₂Te₃Adding deionized water serving as a solvent (the addition amount of the deionized water is regulated and controlled by the filling degree of the volume of the reaction kettle) into a Bi source and a Te source of the nanowire, stirring for 10-30 min, fully and uniformly mixing, adding a glucose reducing agent, and stirring the prepared mixed solution at room temperature for later use;

the invention adopts deionized water as a solvent and adopts glucose as a reducing agent. Organic matters such as ethylene glycol are not used as a solvent, so that the production cost is reduced, the post-treatment process of the product is simplified, and the influence on the environment is reduced. Meanwhile, cheap glucose is used as a weak reducing agent, so that the method is friendly to human body and environment, and the mild reaction is ensured due to the weak reducing performance. Sodium borohydride and hydrazine hydrate are not used as reducing agents, and the reducing agents are high in activity, are not beneficial to regulation and control of reaction, can promote a large number of side reactions, and reduce the utilization rate of raw materials. In addition, the reducing agents have certain corrosivity and toxicity, and have certain harm to human bodies and the environment.

Step two, slowly dropwise adding an acid solution into the solution under the conditions of stirring and cold water bath, and controlling the pH value of the solution to be 0-6;

placing the mixed solution into a 50mL polytetrafluoroethylene lining, placing the lining into a stainless steel reaction kettle, screwing and sealing the reaction kettle, and then placing the reaction kettle into a drying oven for heating to perform hydrothermal reaction;

and step four, after the reaction is finished, adopting an oven natural cooling mode for safety, cooling to room temperature, opening the kettle for sampling, placing the hydrothermal product into a centrifuge tube, adding a proper amount of ethanol solution with the volume fraction of 50% (the addition depends on the volume of the centrifuge tube), centrifuging, decanting the upper-layer solution, collecting the lower-layer precipitated sample, washing the precipitated sample for multiple times, and finally placing the sample into a vacuum drying oven for drying to obtain a gray black powder product.

The water used in the invention is deionized water. The cost of the deionized water is relatively low, and the production cost can be saved.

The second embodiment is as follows: in a method for preparing a pH-controlled bismuth telluride nanowire according to a first specific embodiment, in the first step, a molar ratio of a Bi source to a Te source is 2:3, the molar ratio of the Bi source to the glucose reducing agent is 0.2: 1-5 mmol, the reaction is accurately regulated and controlled in a stoichiometric ratio mode from the precursor of the bismuth telluride, so that many side reactions in a high-temperature and high-pressure environment can be effectively avoided, the utilization rate of raw materials is improved, and the purity of a sample can be improved.

The third concrete implementation mode: in the second step of the method for preparing the bismuth telluride nanowire through pH regulation, acid solution is added for regulating the pH of the precursor solution, and the acid solution is HCl or H₂SO₄The concentration can be configured according to the requirement. These acids are industrially commonly used acids, and are readily available and inexpensive.

The fourth concrete implementation mode: in the third step, the filling degree of the reaction kettle is 50% -80%, the reaction temperature is 150-200 ℃, and the reaction time is 16-32 hours. And the hydrothermal reaction is adopted, so that the experimental reproducibility is good, and the industrial mass production business can be realized. The filling degree is set to be 50% -80%, and a bismuth telluride nanowire sample can be obtained. The critical hydrothermal condition of high temperature and high pressure can not be formed when the filling degree is less than 50 percent. The filling degree is more than 80%, the experimental conditions are unsafe, and the explosion risk exists under the conditions of high temperature and high pressure. Similarly, the reaction temperature is lower than 150 ℃ and the hydrothermal reaction cannot be carried out. The reaction temperature is higher than 200 ℃, and the sample is easy to sinter in the high-temperature and high-pressure environment, so that the appearance and the performance of the product are damaged. The reaction time is less than 16h, and the hydrothermal reaction is incomplete. The hydrothermal time is 32h, the whole reaction can be completely finished, and no precursor remains.

The fifth concrete implementation mode: in the third step, the temperature rise speed in the oven is 4-8 ℃/min. And the safe and high-efficiency hydrothermal reaction experiment can be ensured by adopting a relatively mild heating rate.

The sixth specific implementation mode: in the fourth step, the drying temperature is 50-80 ℃, and the drying time is 8-16 h. And the appearance and performance of the sample can be prevented from being damaged by adopting lower drying temperature.

Example 1:

(1) 0.2mmol of bismuth chloride and 0.3mmol of potassium tellurite are weighed and placed in a 50mL beaker, 32mL of deionized water is added into the beaker, and the beaker is magnetically stirred for 15min at room temperature.

(2) 1.1mmol of glucose reducing agent was weighed into the above solution and magnetic stirring was continued.

(3) Under stirring and a cold water bath, HCl is dropwise added into the solution, the pH value of the solution is regulated to be 1, the prepared mixed solution is transferred into a 50mL polytetrafluoroethylene lining, and then the mixed solution is filled into a simple hydrothermal reaction kettle made of stainless steel, and the filling degree in the hydrothermal reaction kettle is controlled to be 70%. And then placing the hydrothermal reaction kettle into an oven, setting the temperature to be 160 ℃, heating to 160 ℃ at the heating rate of 5 ℃/min, setting the reaction time to be 18h, and then cooling to room temperature.

(4) Adding the water/absolute ethyl alcohol mixed washing liquid into the collected mixed product, centrifuging by using a centrifuge (5 mL of the ethanol/water mixed washing liquid is added for the first time due to the adoption of a 50mL centrifuge tube, 35mL of the ethanol/water mixed washing liquid is added for each subsequent time), decanting the upper layer liquid, washing and precipitating for 3 times, drying the centrifuge tube containing the sample in a vacuum drying oven, drying for 10 hours at the temperature of 50 ℃, and then collecting the product.

(5) The samples were characterized in terms of morphology, composition and phase, as shown in FIGS. 1-3. As can be seen from the attached figure 1, the appearance of the sample presents broom-like micro-nano structure, and the nano wires in the micron scale have obvious hierarchical structure (the length is about 20-60 μm), and the nano wires consist of a plurality of nano wires with the diameter of about 20 nm. From figure 1, a surprising phenomenon can be seen, where the centers of these hierarchical nanowire structures are pH-regulated and assembled into unique self-supporting-broom-like micro-nano structures. Moreover, it can be clearly observed that the sample exhibits a distinct spreading state, suggesting that the sample has a higher specific surface area. As the electron microscope sample is prepared by dispersion through the ultrasonic process (the ultrasonic power is 100%, and the ultrasonic time is 30s), the complete line cluster structure can be seen from figure 1, and about 70% of the appearance of the sample is not damaged, so that the synthesized nanowire has certain stability. Fig. 2 is an EDS diagram of a hydrothermal sample from which it can be seen that the elements of the sample other than C, O, Si (C and O are derived from the conductive paste adhering to the Si wafer and the instrumentation and also a small portion of the air component from the adsorption of the sample, and Si is derived from the Si single wafer as the support carrier for the test sample) are predominantly Bi and Te in composition and the atomic ratio of Bi to Te is about 2:3, close to the theoretical stoichiometric ratio. Meanwhile, other miscellaneous elements are not found, and the fact that the prepared bismuth telluride sample has high purity is suggested. By comparing with JCPDS (15#0683) of a standard bismuth telluride sample, diffraction peaks of the prepared sample at (015), (1010) and (110) crystal planes (three strong peaks) are found in the attached diagram 3 to be in one-to-one correspondence with a standard card of the bismuth telluride, other crystal plane diffraction peaks can also be in good correspondence with the standard card, and other miscellaneous peaks are not found, so that the prepared bismuth telluride nanowire is proved to have higher purity.

Likewise, to confirm the pH control, two comparative experiments were also performed, as detailed in example 2 and example 3.

Example 2:

(1) 0.2mmol of bismuth chloride and 0.3mmol of potassium tellurite are weighed and placed in a 50mL beaker, 32mL of deionized water is added into the beaker, and the beaker is magnetically stirred for 15min at room temperature.

(2) 1.1mmol of glucose reducing agent was weighed into the above solution and magnetic stirring was continued.

(3) Under stirring and a cold water bath, HCl is dropwise added into the solution, the pH value of the solution is regulated to be 2, the prepared mixed solution is transferred into a 50mL polytetrafluoroethylene lining, and then the mixed solution is filled into a simple hydrothermal reaction kettle made of stainless steel, and the filling degree in the hydrothermal reaction kettle is controlled to be 70%. And then placing the hydrothermal reaction kettle into an oven, setting the temperature to be 160 ℃, heating to 160 ℃ at the heating rate of 5 ℃/min, setting the reaction time to be 18h, and then cooling to room temperature.

(4) Adding the water/absolute ethyl alcohol mixed washing liquid into the collected mixed product, centrifuging by using a centrifuge (5 mL of the ethanol/water mixed washing liquid is added for the first time due to the adoption of a 50mL centrifuge tube, 35mL of the ethanol/water mixed washing liquid is added for each subsequent time), decanting the upper layer liquid, washing and precipitating for 3 times, drying the centrifuge tube containing the sample in a vacuum drying oven, drying for 10 hours at the temperature of 50 ℃, and then collecting the product.

(5) The sample was characterized for morphology and is described in detail in figure 4. As can be seen from fig. 4, the morphology of the sample hardly changed as the pH of the solution increased to 2. And through the same ultrasonic dispersion, the micro-nano hierarchical structure of the bismuth telluride sample can still partially retain the initial broom-shaped structure.

Example 3:

(1) 0.2mmol of bismuth chloride and 0.3mmol of potassium tellurite are weighed and placed in a 50mL beaker, 32mL of deionized water is added into the beaker, and the beaker is magnetically stirred for 15min at room temperature.

(2) 1.1mmol of glucose reducing agent was weighed into the above solution and magnetic stirring was continued.

(3) The mixed solution was then transferred to a 50mL teflon liner and then charged into a simple hydrothermal reaction vessel made of stainless steel, with the fill level in the hydrothermal reaction vessel controlled at 70%. And then placing the hydrothermal reaction kettle into an oven, setting the temperature to be 160 ℃, heating to 160 ℃ at the heating rate of 5 ℃/min, setting the reaction time to be 18h, and then cooling to room temperature.

(4) Adding the water/absolute ethyl alcohol mixed washing liquid into the collected mixed product, centrifuging by using a centrifuge (5 mL of the ethanol/water mixed washing liquid is added for the first time due to the adoption of a 50mL centrifuge tube, 35mL of the ethanol/water mixed washing liquid is added for each subsequent time), decanting the upper layer liquid, washing and precipitating for 3 times, drying the centrifuge tube containing the sample in a vacuum drying oven, drying for 10 hours at the temperature of 50 ℃, and then collecting the product.

(5) The samples were characterized with respect to morphology, composition and phase, as detailed in figure 5. As can be seen in the attached figure 5, when the pH of the solution of the bismuth telluride precursor is not regulated, the morphology of the bismuth telluride sample is an amorphous cluster structure formed by nanobelts with the length of about 200-800 nm and folded and distorted nanosheets with the thickness of about 15nm, and a uniform morphology and a self-supporting structure are not provided.