A cuprous selenide nanomaterial and a preparation method thereof

Abstract

The present invention provides a cuprous selenide nanomaterial and a preparation method thereof, belonging to the field of preparation of nanomaterials. The preparation method is as follows: A Cu source, a Se source, an alkali, and a reducing agent are added to a solvent to obtain a mixture; the obtained mixture is stirred and heated for reaction to generate a cuprous selenide nanomaterial; after the reaction is completed, it is cooled to room temperature, and then centrifuged, washed, and dried to obtain a cuprous selenide nanomaterial with a flaky structure; wherein the alkali is one of lithium hydroxide or lithium hydroxide dihydrate. The present invention uses lithium hydroxide or lithium hydroxide dihydrate to replace traditional sodium hydroxide and potassium hydroxide as alkaline regulators, and successfully prepares a cuprous selenide nanomaterial with a flaky structure having a relatively concentrated particle size distribution and good uniformity, and successfully solves the problem of poor particle size uniformity when using potassium hydroxide and sodium hydroxide as alkaline regulators.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of nanomaterials, and particularly relates to a cuprous selenide nanomaterial and a preparation method thereof. Background Art

[0002] Cuprous selenide (Cu 2-x Se) is a kind of liquid-like thermoelectric material with rich raw material reserves and excellent performance. Especially in 2011, with the proposal of the concept of "phonon glass - electron crystal", Cu 2-x Se has once again attracted strong attention and is considered to be a thermoelectric material with good application prospects. Compared with traditional thermoelectric materials Bi 2 Te 3 、PbTe and GeTe containing precious metal Te element or toxic Pb element, the constituent elements of Cu 2-x Se are rich in reserves, environmentally friendly and non-toxic, and have characteristics such as a complex crystal structure, extremely low lattice thermal conductivity, and high thermoelectric performance. It has broad commercial application value in high-temperature waste heat recovery power generation and is expected to provide a friendly solution for replacing traditional thermoelectric materials.

[0003] In 1993, Hicks et al. predicted through theoretical calculations that low-dimensional or nano-sized materials enhance phonon scattering due to the quantum size effect, reduce thermal conductivity, and improve the thermoelectric figure of merit. Since then, extensive research has been carried out on this, and one-dimensional, two-dimensional, superlattice thin films, nano-sized and other thermoelectric materials in various systems have been successfully prepared. The results show that: the nanostructure can effectively change the electrothermal transport characteristics of the material; the quantum confinement effect, energy filtering effect and size effect caused by nanosizing all have a profound impact on the electrothermal transport characteristics, and can simultaneously improve the power factor of the material and reduce the lattice thermal conductivity, which verifies the above theory. According to literature reports, the relatively low lattice thermal conductivity of Cu 2-x Se material indicates that its phonon mean free path is quite small, but the relationship between the specific value and the particle size has not been determined.

[0004] By preparing nano-sized Cu 2-x Se material, the optimal particle size for optimizing the electrothermal transport performance of this material and the influence of grain size on the electrical transport characteristics and stability of Cu 2-x Se can be explored. The existing preparation methods of nanomaterials can be classified into various types according to the state of reaction substances, whether the materials undergo chemical reactions, etc., such as chemical vapor deposition method, solid-phase method, solvothermal method, laser ablation method, sol-gel method, etc. In the past ten-odd years, various synthesis methods of Cu 2-x Se nanomaterials have also been reported. The typical synthesis methods are mainly: 1) Using the solvothermal method, heating and reacting in an autoclave at a temperature of 230 °C for 24 hours to obtain β-Cu 2Se nanosheets; 2) Nanostructured Cu 2 Se was prepared by high-energy ball milling combined with spark plasma sintering, and the ball milling time was up to 50 hours; 3) Nanostructured Cu 2 Se was made using corrosive materials such as oleylamine and octadecene with pungent odors and corrosiveness. In comparison, the raw materials used in the above synthesis methods are prone to causing environmental pollution and certain harm to the human body; the reported reaction processes are relatively complex and the preparation of materials takes a long time. Moreover, the above reactions have strict requirements for containers and high costs, making it difficult to achieve the goal of rapidly and massively preparing target nanomaterials. Prior to this, the applicant has already disclosed a preparation method of Cu 2-x Se nanomaterials in his doctoral thesis (The influence of grain size and doping on the thermoelectric properties of copper selenide compounds, Wuhan University, Kong Fangfang), but the size uniformity of the Cu 2-x Se nanomaterials prepared by this method is relatively poor. Therefore, how to provide a preparation method of Cu 2-x Se nanomaterials with relatively uniform particle size and morphology, and further improving the size factor may have important significance for the influence mechanism of Cu 2-x Se electrothermal transport. SUMMARY OF THE INVENTION

[0005] The purpose of the present invention is to provide a copper selenide nanomaterial and its preparation method to solve the problem that the Cu 2-x Se nanomaterials prepared by existing methods have poor size and morphology uniformity. A preparation method of Cu 2-x Se nanomaterials with relatively uniform particle size and mostly hexagonal flake structures in morphology is provided.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of copper selenide nanomaterials, including the following steps:

[0008] 1) Add a Cu source, a Se source, an alkali, and a reducing agent to a solvent to obtain a mixture;

[0009] 2) Heat the obtained mixture for reaction to generate Cu 2-x Se nanomaterials;

[0010] The alkali is lithium hydroxide or lithium hydroxide dihydrate.

[0011] Preferably, in step 1), the Cu source includes one of copper sulfate or copper chloride, the Se source includes one of selenium dioxide or selenium powder, and the reducing agent is glucose;

[0012] The molar ratio of the Cu source, Se source, base and reducing agent is 1.8 - 2.1:1:2 - 5:2.5 - 10.

[0013] Preferably, the solvent described in step 1) is triethylene glycol.

[0014] Preferably, the concentration of the Se source in the mixture is 0.08 - 0.15 mmol / mL.

[0015] Preferably, the stirring speed in step 2) is 500 - 1200 r / min, the heating reaction temperature is 200 - 270 °C, and the time is 2 - 6 h.

[0016] Preferably, the method for preparing the cuprous selenide nanomaterial further comprises the following steps:

[0017] After the heating reaction is completed, the system is cooled to room temperature, and then centrifuged, washed and dried to obtain the Cu 2-x Se nanomaterial;

[0018] The centrifugation is carried out at a rotation speed of 5000 - 7000 r / min for 10 - 30 min;

[0019] The washing is carried out by washing 3 - 6 times with deionized water and then 3 - 6 times with absolute ethanol until the washing liquid is colorless and clear;

[0020] The drying is carried out in a vacuum oven at 55 - 70 °C for 8 - 14 h.

[0021] Another object of the present invention is to provide a Cu 2-x Se nanomaterial prepared by the described preparation method.

[0022] The molecular formula of the cuprous selenide nanomaterial is Cu 2-x Se, where x = 0 - 0.2.

[0023] During the material preparation process, as the reaction time progresses, the solution temperature gradually increases and the color also changes continuously with the reaction. First, as the reaction temperature increases, the solid material gradually dissolves, and the reaction solution gradually changes from grass green to dark green, indicating that the Cu source is completely dissolved; as the reaction temperature continues to increase, the solution quickly becomes turbid and the color continues to deepen to dark green and then gradually changes to brick red, brown, black and a precipitate with metallic luster appears, which indicates that the Se element in the Se source and the Cu element in the Cu source are gradually reduced to form the target Cu 2-x Se material; thereafter, the solution color no longer changes, only the content of fine particles with metallic luster increases.

[0024] The present invention has at least the following beneficial effects:

[0025] 1. The present invention uses triethylene glycol with high stability, low toxicity, low volatility, and high boiling point as the reaction solvent. It not only has a strong dissolving ability for polar materials but also has certain reducibility under boiling conditions.

[0026] 2. The present invention uses glucose as a reducing agent, which has the advantages of being non-toxic and having no pungent odor. Moreover, the final product of glucose after the reaction is safe, non-toxic, and easily soluble in water, and can be removed by water washing.

[0027] 3. The reaction of the present invention can be carried out under normal pressure without the protection of inert gas, with low requirements for reaction equipment and a significantly improved safety factor. The raw materials used in the present invention are green and environmentally friendly, the preparation method has simple and efficient steps, the reaction time can be shortened to 2 hours, and compared with the reported preparation methods of Cu 2-x Se nanomaterials, the time is significantly shortened. The mass of Cu 2-x Se nanomaterials prepared at one time can reach 10 g, the preparation efficiency is greatly improved, and there is a possibility of preparing Cu 2-x Se nanomaterials with a mass of up to 100 g at one time.

[0028] 4. The present invention uses lithium hydroxide or lithium hydroxide dihydrate as an alkaline regulator and successfully prepares a kind of flaky Cu 2-x Se nanomaterials with relatively uniform particle size. For the preparation of Cu 2-x Se nanomaterials by the existing solvothermal method, the alkaline regulators used are mostly NaOH or KOH. From the previous experimental test results of the applicant, it can be seen that when KOH and NaOH are used as alkaline regulators, the particle size uniformity is poor. When KOH is used as the alkaline regulator, the distribution range of the particle size of the prepared material is from dozens of nanometers to 1 micrometer, and when NaOH is used as the alkaline regulator, the particle size of the prepared material is distributed around ten to 200 nanometers. Brief Description of the Drawings

[0029] Figure 1 is the scanning electron microscope (SEM) image of the Cu 2-x Se nanomaterials prepared in Example 1 of the present invention;

[0030] Figure 2 is the scanning electron microscope (SEM) image of the Cu 2-x Se nanomaterials prepared in Example 2 of the present invention;

[0031] Figure 3 is the scanning electron microscope (SEM) image of the Cu 2-x Se nanomaterials prepared in Example 3 of the present invention;

[0032] Figure 4 is the scanning electron microscope (SEM) image of the Cu 2-xScanning electron microscope (SEM) image of Se nanomaterials;

[0033] Figure 5 is the Cu 2-x X-ray powder diffraction (XRD) pattern of the CuSe nanomaterials prepared in Example 1, Example 2, and Example 4 of the present invention;

[0034] Figure 6 is the Cu 2-x X-ray powder diffraction (XRD) pattern of the CuSe nanomaterials prepared in Example 3 of the present invention;

[0035] Figure 7 is the Cu 2-x Particle size statistical result graph of the CuSe nanomaterials prepared in Example 3 of the present invention;

[0036] Figure 8 is the Cu 2-x Microscopic characterization graph of the CuSe nanomaterials prepared in Example 3 of the present invention, where a is a transmission electron microscope (TEM) image, b is a high-resolution lattice fringe (HRTEM) image of the selected area, and c is a selected area electron diffraction (SAED) image;

[0037] Figure 9 is the Cu 2-x X-ray photoelectron spectroscopy (XPS) pattern of the CuSe nanomaterials prepared in Example 3 of the present invention;

[0038] Figure 10 is the Cu 2-x Raman spectrum (Raman) pattern of the CuSe nanomaterials prepared in Example 3 of the present invention;

[0039] Figure 11 is the Cu 2-x Scanning electron microscope (SEM) image of the CuSe nanomaterials prepared in Comparative Example 1 of the present invention;

[0040] Figure 12 is the Cu 2-x Scanning electron microscope (SEM) image of the CuSe nanomaterials prepared in Comparative Example 2 of the present invention;

[0041] Figure 13 is the Cu 2-x Scanning electron microscope (SEM) image of the CuSe nanomaterials prepared in Comparative Example 3 of the present invention;

[0042] Figure 14 is the Cu 2-x Scanning electron microscope (SEM) image of the CuSe nanomaterials prepared in Comparative Example 4 of the present invention;

[0043] Figure 15 is the Cu2-x Particle size statistical results of Se nanomaterials. Specific implementation mode

[0044] The present invention provides a preparation method of cuprous selenide nanomaterials, including the following steps:

[0045] 1) Add a Cu source, a Se source, an alkali, and a reducing agent to a solvent to obtain a mixture;

[0046] 2) Heat the obtained mixture for reaction to generate Cu 2-x Se nanomaterials;

[0047] The alkali is lithium hydroxide or lithium hydroxide dihydrate.

[0048] In the present invention, in step 1), the Cu source includes one of copper sulfate or copper chloride, the Se source includes one of selenium dioxide or selenium powder, and the reducing agent is glucose;

[0049] The molar ratio of the Cu source, the Se source, the alkali, and the reducing agent is preferably 1.8 - 2.1:1:2 - 5:2.5 - 10, more preferably 1.8 - 2:1:3 - 4:4 - 7, and even more preferably 2:1:4:5.

[0050] In the present invention, the solvent in step 1) is triethylene glycol.

[0051] The concentration of the Se source in the mixture is preferably 0.08 - 0.15 mmol / mL, more preferably 0.1 - 0.15 mmol / mL, and even more preferably 0.1 - 0.12 mmol / mL.

[0052] In the present invention, in step 2), the stirring speed is preferably 500 - 1200 r / min, more preferably 800 - 1000 r / min, the heating reaction temperature is preferably 200 - 270 °C, more preferably 220 - 250 °C, and the time is preferably 2 - 6 h, more preferably 2 - 4 h.

[0053] In the present invention, the preparation method of the cuprous selenide nanomaterials further includes the following steps:

[0054] After the heating reaction is completed, cool the system to room temperature, then carry out centrifugation, washing, and drying to obtain Cu 2-x Se nanomaterials;

[0055] The centrifugation is preferably carried out at a rotational speed of 5000 - 7000 r / min, more preferably at a rotational speed of 6000 - 7000 r / min, and even more preferably at a rotational speed of 6000 - 6500 r / min; the centrifugation time is preferably 10 - 30 min, more preferably 15 - 30 min, and even more preferably 15 - 25 min;

[0056] The washing is carried out by washing with deionized water 3 - 6 times and then washing with absolute ethanol 3 - 6 times until the washing liquid is colorless and clear;

[0057] The drying is preferably carried out in a vacuum oven at 55 - 70 °C, more preferably in a vacuum oven at 60 - 65 °C, and even more preferably in a vacuum oven at 60 - 65 °C; the drying time is preferably 8 - 14 h, more preferably 10 - 14 h, and even more preferably 10 - 12 h.

[0058] The present invention also provides a Cu 2-x Se nanomaterial prepared by the described preparation method, and the Cu 2-x Se nanomaterial mainly presents as hexagonal flakes.

[0059] The molecular formula of the copper selenide nanomaterial is Cu 2-x Se, where x = 0 - 0.2.

[0060] Hereinafter, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0061] Example 1

[0062] 1) Accurately weigh 2.5 mmol of selenium dioxide. Taking the Se source as a reference, weigh copper chloride, selenium dioxide, lithium hydroxide and the reducing agent glucose according to the molar ratio of Cu source, Se source, base and reducing agent of 2:1:4:5 and place them in a 50 ml two-necked round-bottom flask. Measure 25 ml of triethylene glycol solvent and add it thereto.

[0063] 2) Place the flask in a high-temperature resistant oil bath, magnetically stir for 30 minutes, then heat and raise the temperature to the target temperature of 220 °C, and continuously stir and heat the reaction for 4 hours at a stirring speed of 800 r / min to generate Cu 2-x Se nanomaterial.

[0064] 3) After the reaction is completed, the system is naturally cooled to room temperature, and then centrifuged at a speed of 7000 r / min for 10 min; the obtained precipitate is first washed 5 times with deionized water and then 4 times with absolute ethanol until the washing liquid is colorless and clear; finally, the washed precipitate is placed in a vacuum drying oven at 60 °C for drying for 12 h, and after cooling, Cu 2-x Se (x = 0) nanomaterials are obtained. The mass of the prepared Cu 2-x Se nanomaterials is 0.487 g, and the yield is 94.6%.

[0065] Example 2

[0066] 1) Accurately weigh 2.5 mmol of selenium dioxide. Taking the Se source as a reference, weigh copper sulfate, selenium dioxide, lithium hydroxide and the reducing agent glucose according to the molar ratio of Cu source, Se source, base and reducing agent of 2.1:1:3:2.5 and place them in a 50 ml two-necked round-bottom flask. Measure 25 ml of triethylene glycol solvent and add it thereto.

[0067] 2) Place the flask in a high-temperature oil bath and magnetically stir for 30 minutes, then heat and raise the temperature to the target temperature of 200 °C, and continuously stir and heat the reaction for 6 h at a stirring speed of 500 r / min to generate Cu 2-x Se nanomaterials.

[0068] 3) After the reaction is completed, the system is naturally cooled to room temperature, and then centrifuged at a speed of 6000 r / min for 15 min; the obtained precipitate is first washed 5 times with deionized water and then 4 times with absolute ethanol until the washing liquid is colorless and clear; finally, the washed precipitate is placed in a vacuum drying oven at 55 °C for drying for 14 h, and after cooling, Cu 2-x Se (x = 0) nanomaterials are obtained. The mass of the prepared Cu 2-x Se nanomaterials is 0.498 g, and the yield is 96.7%.

[0069] Example 3

[0070] 1) Accurately weigh 50 mmol of selenium powder. Taking the Se source as a reference, weigh copper chloride, selenium powder, lithium hydroxide dihydrate and the reducing agent glucose according to the molar ratio of Cu source, Se source, base and reducing agent of 1.8:1:2:4 and place them in a 1 L two-necked round-bottom flask. Measure 500 ml of triethylene glycol solvent and add it thereto.

[0071] 2) Place the flask in a high-temperature oil bath and magnetically stir for 30 minutes, then heat and raise the temperature to the target temperature of 250 °C, and continuously stir and heat the reaction for 2 h at a stirring speed of 1200 r / min, and then naturally cool to room temperature to generate Cu 2-x Se nanomaterials.

[0072] 3) After the reaction is completed, the system is naturally cooled to room temperature, and then centrifuged at a speed of 5000 r / min for 25 min; the obtained precipitate is first washed 5 times with deionized water and then 4 times with absolute ethanol until the washing liquid is colorless and clear; finally, the washed precipitate is placed in a vacuum drying oven at 65 °C for 8 hours, and after cooling, Cu 2-x Se(x = 0.2) nanomaterials are obtained. The mass of the prepared Cu 2-x Se nanomaterials is 9.48 g, and the yield is 98.1%.

[0073] Example 4

[0074] 1) Accurately weigh 50 mmol of selenium dioxide. Taking the Se source as a reference, weigh copper sulfate, selenium dioxide, lithium hydroxide dihydrate, and the reducing agent glucose according to the molar ratio of Cu source, Se source, base, and reducing agent of 2:1:5:10, and place them in a 1 L two-necked round-bottom flask. Measure 500 ml of triethylene glycol solvent and add it thereto.

[0075] 2) Place the flask in a high-temperature resistant oil bath and magnetically stir for 30 minutes, then heat and raise the temperature to the target temperature of 270 °C, and continuously stir and heat the reaction for 4 hours at a stirring speed of 1000 r / min, and then naturally cool to room temperature to generate Cu 2-x Se nanomaterials.

[0076] 3) After the reaction is completed, the system is naturally cooled to room temperature, and then centrifuged at a speed of 6500 r / min for 30 min; the obtained precipitate is first washed 3 times with deionized water and then 4 times with absolute ethanol until the washing liquid is colorless and clear; finally, the washed precipitate is placed in a vacuum drying oven at 70 °C for 10 hours, and after cooling, Cu 2-x Se(x = 0) nanomaterials are obtained. The mass of the prepared Cu 2-x Se nanomaterials is 9.87 g, and the yield is 95.8%.

[0077] Comparative Example 1

[0078] 1) Accurately weigh 2.5 mmol of selenium dioxide. Taking the Se source as a reference, weigh copper chloride, selenium dioxide, sodium hydroxide, and the reducing agent glucose according to the molar ratio of Cu source, Se source, base, and reducing agent of 2:1:4:5, and place them in a 50 ml two-necked round-bottom flask. Measure 25 ml of triethylene glycol solvent and add it thereto.

[0079] 2) Place the flask in a high-temperature resistant oil bath and magnetically stir for 30 minutes, then heat and raise the temperature to the target temperature of 220 °C, and continuously stir and continuously heat the reaction for 2 hours to generate Cu 2-x Se nanomaterials.

[0080] 3) After the reaction is completed, the system is naturally cooled to room temperature, and then centrifuged at a speed of 6000 r / min for 10 min; the obtained precipitate is first washed 5 times with deionized water and then 4 times with absolute ethanol until the washing liquid is colorless and clear; finally, the washed precipitate is placed in a vacuum drying oven at 60 °C for 12 hours, and after cooling, Cu 2-x Se nanomaterials are obtained.

[0081] Comparative Example 2

[0082] The operation steps are the same as those of Comparative Example 1.

[0083] Comparative Example 3

[0084] 1) Accurately weigh 2.5 mmol of selenium dioxide. Taking the Se source as a reference, weigh copper chloride, selenium dioxide, potassium hydroxide and the reducing agent glucose according to the molar ratio of Cu source, Se source, base and reducing agent of 2:1:4:5 and place them in a 50 ml two-necked round-bottom flask. Measure 25 ml of triethylene glycol solvent and add it thereto.

[0085] 2) Place the flask in a high-temperature resistant oil bath and magnetically stir for 30 minutes, then heat and raise the temperature to the target temperature of 220 °C, and continuously stir and heat the reaction for 2 hours at a stirring speed of 800 r / min to generate Cu 2-x Se nanomaterials.

[0086] 3) After the reaction is completed, the system is naturally cooled to room temperature, and then centrifuged at a speed of 6000 r / min for 10 min; the obtained precipitate is first washed 5 times with deionized water and then 4 times with absolute ethanol until the washing liquid is colorless and clear; finally, the washed precipitate is placed in a vacuum drying oven at 60 °C for 12 hours, and after cooling, Cu 2-x Se nanomaterials are obtained.

[0087] Comparative Example 4

[0088] The operation steps are the same as those of Comparative Example 3.

[0089] The Cu 2-x Se nanomaterials prepared in Examples 1-4 and Comparative Examples 1-4 of the present invention were microscopically characterized by a scanning electron microscope. Through Figures 1 to 4 It can be observed that the Cu 2-x Se nanoparticles prepared in Examples 1-4 using lithium hydroxide or lithium hydroxide dihydrate as the basic regulator have relatively uniform sizes and are mostly hexagonal flake structures, while the Cu 2-xThe sizes of Se nanoparticles vary greatly and the uniformity is poor. To verify this experimental conclusion, therefore, the applicant repeated the experiment multiple times and verified that when NaOH and KOH were used as alkaline regulators under normal pressure and in an unprotected atmosphere, the prepared Cu 2-x Se nanoparticles had poor size uniformity. It could be clearly observed from Figures 11 to 14 that the prepared Cu 2-x Se material had a wide particle size distribution range and slightly poor dispersibility.

[0090] The particle sizes of the Cu 2-x Se nanomaterials prepared in Example 3 and Comparative Example 1 were measured. The statistical results are shown in Figure 7 and Figure 15 . It can be seen that the Cu 2-x Se nanomaterials prepared using lithium hydroxide dihydrate as the alkaline regulator had a relatively narrow particle size distribution range. Nearly 97% of the particle sizes were in the range of 75 nm - 135 nm. Combining with its SEM image, it can be known that the material presented a uniform flaky structure. While the Cu 2-x Se nanomaterials prepared in Comparative Example 1 using NaOH as the alkaline regulator had a relatively wide particle size distribution and poor uniformity.

[0091] Figure 5 XRD patterns of the Cu 2-x Se nanomaterials prepared in Example 1, Example 2, and Example 4 are shown. Five obvious diffraction peaks can be seen near 27.1°, 45.0°, 53.2°, 65.5°, and 72.3°. This result is consistent with the PDF#88 - 2043 card (Cu 2 Se) in the XRD standard card; Figure 6 The XRD test results of Example 3 showed that in addition to six obvious diffraction peaks near 26.7°, 31.0°, 44.6°, 52.9°, 64.9°, and 71.6°, there were no other impurity peaks. The six diffraction peaks corresponded to the diffraction peak positions of the (111), (220), (220), (311), (400), and (331) crystal planes of cubic Cu 2-x Se. This result is consistent with the PDF#71 - 0044 card (Cu 1.8 Se) in the XRD standard card. In addition, from the diffraction results, it can be obtained that the full width at half maximum value of the diffraction peak is relatively large, indicating that the prepared Cu 2-x Se nanomaterials have small particles.

[0092] Figure 8 The microstructure of the Cu 2-x Se nanomaterials prepared in Example 3 was characterized in detail using high - resolution TEM. The results are shown in Figure 8 . Figure 8What was tested was a hexagonal Cu 2-x TEM image of Se nanosheets. The side size of the hexagonal sheets is about 15 - 40 nm, and the diagonal size of the particles is about 80 nm. Figure 8 also gives the prepared Cu 2-x high-resolution lattice fringes of Se nanosheets. From the results, it can be known that the measured interplanar spacing is 0.33 nm, corresponding to the (111) crystal plane, which is a face-centered cubic structure. For the Cu 2-x selected area electron diffraction image of Se nanosheets prepared in Example 3. After measuring and calculating the size information of the Debye rings, it is obtained that the corresponding crystal structure is face-centered cubic. The four Debye rings with increasing radius in this result correspond to the crystal plane families {111}, {200}, {220}, and {311} respectively. From the TEM analysis results, it can be seen that the Cu 2-x Se nanomaterials prepared in Example 3 are polycrystalline particles, but there are almost no lattice defects in the small size range, indicating that the Cu 2-x Se nanomaterials obtained by this preparation method have a high crystallinity.

[0093] The chemical composition information of the Cu 2-x Se nanomaterials prepared in Example 3 was tested with an XPS device. The XPS test results of Cu and Se atoms are as Figure 9 shown. Among them, from the core-level spectrum of Cu2p, it can be found that the two peak positions with binding energies of 932.43 eV and 942.78 eV correspond to Cu2p3 / 2, and the peak position of 952.38 eV corresponds to Cu2p1 / 2, indicating that there is no Cu 2-x in the Cu 2+ Se prepared by this method; in the core-level spectrum of Se3d, a strong peak can be seen, and the corresponding peak value is 54.58 eV, and the peak position corresponds to Se3d5 / 2, indicating that the Se element in the material only shows a valence state of -2.

[0094] The Raman spectrum of the Cu 2-x Se nanomaterials prepared in Example 3 irradiated with a 632.8 nm laser is as Figure 10 shown. From the figure, it can be observed that the Raman spectrum of the material only has a large-intensity resonance peak at the position of 259.14 cm -1 , which is consistent with the position where the Se - Se lattice causes vibration (260 cm -1 ). The relative width of this resonance peak is slightly larger, indicating that the symmetry of this material is high. This matches the result that the powder material is cubic phase obtained from the XRD analysis.

[0095] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0096] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of cuprous selenide nanomaterials, characterized in that, it comprises the following steps: 1) Add a Cu source, a Se source, an alkali, and a reducing agent into a solvent to obtain a mixture; 2) Stir and heat the obtained mixture for reaction to generate cuprous selenide nanomaterials; The alkali described in step 1) is lithium hydroxide or lithium hydroxide dihydrate; The molar ratio of the Cu source, the Se source, the alkali, and the reducing agent is 1.8 - 2.1:1:2 - 5:2.5 - 10; The heating reaction temperature is 200 - 270 °C, and the time is 2 - 6 h; The Cu source contains one of copper sulfate or copper chloride, the Se source contains one of selenium dioxide or selenium powder, and the reducing agent is glucose; The solvent is triethylene glycol; The concentration of the Se source in the mixture is 0.08 - 0.15 mmol / mL; 97% of the particle sizes in the cuprous selenide nanomaterials are 75 nm - 135 nm.

2. The preparation method of cuprous selenide nanomaterials according to claim 1, characterized in that, the stirring speed described in step 2) is 500 - 1200 r / min.

3. The preparation method of cuprous selenide nanomaterials according to claim 2, characterized in that, it further comprises the following steps: After the heating reaction is completed, cool the system to room temperature, then carry out centrifugation, washing, and drying to obtain cuprous selenide nanomaterials; The centrifugation is carried out at a rotation speed of 5000 - 7000 r / min for 10 - 30 min; The washing is carried out by washing with water 3 - 6 times and then washing with absolute ethanol 3 - 6 times until the washing liquid is colorless and clear; The drying is carried out in a vacuum oven at 55 - 70 °C for 8 - 14 h.

4. Cuprous selenide nanomaterials prepared by the preparation method described in any one of claims 1 - 3.

5. A cuprous selenide nanomaterial according to claim 4, characterized in that, The molecular formula is Cu 2-x Se, where x = 0 to 0.2.

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