A SnO2 / Se nanocomposite material and its preparation method and application

Abstract

The present invention provides a SnO2 / Se nanocomposite material, a preparation method, and an application thereof. The SnO2 / Se nanocomposite material comprises Se nanowires and SnO2 nanosheets, wherein the SnO2 nanosheets are dispersed between the Se nanowires and / or supported on the Se nanowires. The SnO2 / Se nanocomposite material is obtained by allowing ultrathin SnSe nanosheets obtained by liquid exfoliation to stand in an aqueous solution to undergo self-transformation. The preparation process is stable and controllable and can be controlled by adjusting the size of the SnSe nanosheets, the standing time, the standing temperature, and the alkalinity of the aqueous solution. The resulting SnO2 / Se nanocomposite material is applied to photodetectors and exhibits excellent light response performance. The resulting SnO2 / Se nanocomposite material can also be used in fields such as gas sensors, energy storage devices, and mode-locked lasers.

Description

Technical Field

[0001] The invention belongs to the field of nano material preparation, and relates to a SnO2 / Se nano composite material and a preparation method and application thereof. Background Art

[0002] Over the past decade, the rapid development of liquid-phase exfoliation technology has driven fundamental research and applications in ultrathin two-dimensional materials. It has shown great potential for the large-scale preparation of two-dimensional materials. However, two-dimensional crystals prepared by liquid-phase exfoliation are typically small in lateral dimensions, exposing a large number of chemically active crystal facets and reducing their stability. Studying the degradation chemistry of two-dimensional materials is crucial for their preservation and application, as well as for developing new two-dimensional stable phases through the spontaneous transformation of unstable to stable structures.

[0003] CN110028098A discloses a liquid phase exfoliation method for preparing high-concentration SnS2 nanosheets. A certain amount of tin disulfide polycrystalline powder or tin disulfide single crystal block is added to a sealed blue-capped ultrasonic bottle. A certain amount of polar solvent is then added to the blue-capped ultrasonic bottle to form a solution system, which is then subjected to an inert gas bubbling treatment. Ultrasonic treatment is then performed. During the ultrasonic treatment, ice cubes are added to the ultrasonic cleaning machine to create a low-temperature environment, which acts as an ice bath to cool the environment, thereby obtaining an orange-yellow SnS2 nanosheet dispersion.

[0004] In addition to SnS2, tin selenide (SnSe) has received more extensive attention in the fields of optics, optoelectronics, photothermal devices, thermoelectrics, and ferroelectrics due to its unique structure and multi-purpose properties.

[0005] Existing technology (Li, F. Defect Engineering in Ultrathin SnSe Nanosheets for High-Performance Optoelectronic Applications. ACS Applied Materials & Interfaces, 13(28), 33226–33236. doi: 10.1021 / acsami.1c05254) uses a combination of lithium ion intercalation and ultrasonic liquid phase exfoliation to efficiently prepare ultrathin SnSe nanosheets with controllable Se defects. As the lithiation time increases, the loss of Se elements, the narrowing of the band gap, and the increase of defects are observed. The results show that SnSe nanosheets with high defect density have faster carrier recombination times and significantly improved photodetection performance. The photocurrent, photoresponsivity, photoresponse speed, and detection rate of its photoelectrochemical photodetector are increased by 4 to 10 times, and it also has good stability and a broadband detection range from the ultraviolet to the near-infrared region. This study provides an effective way for the large-scale production of SnSe nanosheets.

[0006] Two-dimensional SnSe layers are prepared using liquid-phase exfoliation. Due to the large interlayer bonding energy, the lateral dimensions of the ~2nm-thick SnSe after exfoliation are only tens of nanometers. Consequently, the exfoliated two-dimensional SnSe has a large specific surface area, which reduces its stability. Theoretical calculations and experimental studies have shown that two-dimensional SnSe is stable in air.

[0007] However, there are no reports on the stability of 2D SnSe in water. The reddish-brown precipitates, defects, and disordered edges observed in SnSe nanosheets (NSs) suggest the instability of 2D SnSe in water.

[0008] In addition, studies have shown that the surface of SnSe NSs can be oxidized to SnO2, which is an effective electron transport material in perovskite solar cells and one of the best gas sensing materials. However, the stability and evolution of SnSe NSs in water are still unclear. Exploiting this unstable property to synthesize a new stable low-dimensional material may provide insights into this field. Summary of the Invention

[0009] In view of the problems existing in the prior art, the purpose of the present invention is to provide a SnO2 / Se nanocomposite material and its preparation method and application, wherein the SnO2 / Se nanocomposite material comprises Se nanowires and SnO2 nanosheets, wherein the SnO2 nanosheets are dispersed between the Se nanowires and / or loaded on the Se nanowires. The SnO2 / Se nanocomposite material is obtained by allowing ultrathin SnSe nanosheets to stand in an aqueous solution to undergo self-transformation. The preparation process is stable and controllable and can be controlled by adjusting the size of the ultrathin SnSe nanosheets, the concentration in the aqueous solution, the standing time, the standing temperature, and the alkalinity of the aqueous solution. The obtained SnO2 / Se nanocomposite material is applied to photodetectors and has excellent light response performance. The obtained SnO2 / Se nanocomposite material can also be used in fields such as gas sensors, energy storage devices, and mode-locked lasers.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a SnO2 / Se nanocomposite material comprising Se nanowires and SnO2 nanosheets, wherein the SnO2 nanosheets are dispersed between the Se nanowires and / or loaded on the Se nanowires.

[0012] SnO2 is a wide-bandgap semiconductor material that absorbs only ultraviolet light, while Se, a semiconductor material with a bandgap of approximately 1.6 eV, can absorb visible light. SnO2 is an excellent electron transport medium, enabling rapid transfer of photogenerated carriers from Se nanowires to the circuit, generating a high photocurrent. It also prevents recombination of photogenerated carriers, improving photoresponse characteristics.

[0013] The present invention provides a novel SnO2 / Se nanocomposite material composed of SnO2 nanosheets and Se nanowires. Thus, the SnO2 / Se nanocomposite material exhibits superior photoelectric properties. The SnO2 / Se nanocomposite material is prepared by a specific preparation method. Ultrathin SnSe nanosheets are dispersed in an aqueous solution and allowed to stand for a period of time, resulting in the self-transformation into the SnO2 / Se nanocomposite material. This transformation process can be controlled by adjusting the size of the SnSe nanosheets, the standing time, the standing temperature, and the alkalinity of the solvent. Because SnO2 is an excellent electron transport medium with the characteristic of rapid electron transfer and forms a favorable energy band alignment with Se, photoelectric detection prepared from the SnO2 / Se nanocomposite material deposited on an electrode surface exhibits excellent photoresponse performance. In summary, the SnO2 / Se nanocomposite material exhibits a faster current response speed and a higher photoresponse current, making it suitable for applications in fields requiring rapid electron transfer, such as sensing and catalysis. It can also be used in fields such as gas sensors, energy storage devices, and mode-locked lasers.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] As a preferred technical solution of the present invention, based on the mass of the SnO2 / Se nanocomposite material being 100wt%, the Se nanowires account for 30 to 98wt%, for example, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt% or 98wt%, etc., but are not limited to the listed values, and other values ​​not listed within the above numerical range are equally applicable.

[0016] Preferably, based on the mass of the SnO2 / Se nanocomposite material being 100wt%, the SnO2 nanosheets account for 2 to 70wt%, for example, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt% or 70wt%, etc., but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0017] Preferably, in the SnO2 / Se nanocomposite material, the diameter of the Se nanowire is 20 to 200 nm, for example, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm or 200 nm, and the length is 200 nm to 2 μm, for example, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2 μm, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0018] Preferably, in the SnO2 / Se nanocomposite material, the thickness of the SnO2 nanosheets is ≤15nm, for example, it can be 15nm, 14nm, 13nm, 12nm, 11nm, 10nm, 9nm, 8nm, 7nm, 6nm, 5nm, 4nm, 3nm, 2nm or 1nm, etc., and the diameter is less than or equal to 300nm, for example, it can be 300nm, 280nm, 260nm, 240nm, 220nm, 200nm, 180nm, 160nm, 140nm, 120nm, 100nm, 80nm, 60nm, 40nm, 20nm, 10nm or 5nm, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0019] In the SnO2 / Se nanocomposite of the present invention, decreasing the diameter and length of the Se nanowires enhances the photoelectric performance of the SnO2 / Se nanocomposite. Adjusting the mass fraction of the nanowires also influences the properties of the resulting nanocomposite. Preferably, the mass fraction of Se is 48-54 wt%, more preferably 51 wt%, or 66.7% by mole.

[0020] In a second aspect, the present invention provides a method for preparing the SnO2 / Se nanocomposite material according to the first aspect, comprising the following steps:

[0021] The ultrathin SnSe nanosheets are dispersed in an aqueous solution and allowed to stand, so that the ultrathin SnSe nanosheets undergo self-transformation until all SnSe is transformed, thereby obtaining a SnO2 / Se nanocomposite material.

[0022] In the preparation method, the self-conversion process can be controlled by adjusting the size of ultrathin SnSe nanosheets, the concentration of ultrathin SnSe nanosheets in the aqueous solution, the standing time, the standing temperature and the alkalinity of the aqueous solution, thereby affecting the self-conversion degree (self-conversion rate) of the ultrathin SnSe nanosheets and the proportion, size and morphology of SnO2 nanosheets and Se nanowires in the SnO2 / Se nanocomposite material.

[0023] Hydroxide in the environment acts on ultrathin SnSe nanosheets to participate in their self-transformation process. Therefore, any parameter that can change the interaction between hydroxide and ultrathin SnSe nanosheets can affect the result of self-transformation.

[0024] For example, when standing in a pure water solution at room temperature, the size of the ultra-thin SnSe nanosheets will affect the efficiency and effect of self-conversion due to the constant hydroxide concentration in the water flow. The smaller the size of the ultra-thin SnSe, the higher the efficiency of self-conversion into SnO2 / Se nanocomposites. The smaller the generated SnO2 nanosheets and the smaller the diameter of the Se nanowires, the better the photoelectric performance of the resulting SnO2 / Se nanocomposites.

[0025] When standing in a pure aqueous solution at room temperature, the concentration of ultrathin SnSe nanosheets in the aqueous solution will affect the efficiency and effect of self-conversion due to the constant hydroxide concentration in the water flow. The higher the concentration, the longer the standing time required. However, reducing the concentration of ultrathin SnSe nanosheets in the aqueous solution will accelerate the self-conversion process, and the concentration can also affect the length of the Se nanosheets.

[0026] When the hydroxide concentration in the aqueous solution changes, the efficiency and effect of the self-conversion of the ultra-thin SnSe nanosheets will be affected. Therefore, the self-conversion process can be accelerated by increasing the standing temperature to promote the dissociation of water to increase the hydroxide concentration in the aqueous solution and / or adding a hydroxide-containing substance to adjust the alkalinity of the aqueous solution. It should be noted that, under the same conditions, the efficiency or speed of self-conversion is roughly proportional to the hydroxide concentration. When the hydroxide concentration is increased to 10 times the original (i.e., the pH value increases by 1), the efficiency or speed of self-conversion will also increase by about 10 times, thereby greatly shortening the standing time. However, while accelerating the self-conversion, the higher hydroxide concentration will also affect the morphology and size of the resulting SnO2 / Se nanocomposite material itself, especially reducing the amount of SnO2 present and causing the Se nanowires to transform into Se single crystals, thereby losing the nanostructure, and thus causing the performance of the resulting SnO2 / Se nanocomposite material to deteriorate.

[0027] Therefore, the present invention does not strictly limit the parameters affecting the self-conversion process, but only provides preferred ranges and matching schemes. Those skilled in the art can also adjust and reasonably match these factors affecting the self-conversion process according to actual needs, so that the ultrathin SnSe nanosheets can fully complete the self-conversion to obtain SnO2 / Se nanocomposite materials and the SnO2 / Se nanocomposite materials can achieve the target performance.

[0028] As a preferred technical solution of the present invention, the concentration of the ultrathin SnSe nanosheets in the aqueous solution in step (2) is 0.1 to 1 mg / mL, for example, 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0029] Preferably, the standing comprises standing at room temperature (about 25° C.) for 25 to 100 days, such as 25 days, 28 days, 31 days, 34 days, 37 days, 40 days, 43 days, 46 days, 49 days, 52 days, 55 days, 58 days, 61 days, 64 days, 67 days, 70 days, 73 days, 76 days, 79 days, 82 days, 85 days, 88 days, 91 days, 94 days, 97 days or 100 days, etc., preferably 90 to 100 days, or at 26 to 50° C. For example, 26°C, 29°C, 32°C, 35°C, 38°C, 41°C, 44°C, 47°C or 50°C, and standing for 10 to 45 days, such as 10 days, 12 days, 14 days, 16 days, 18 days, 20 days, 22 days, 24 days, 26 days, 28 days, 30 days, 32 days, 34 days, 36 days, 38 days, 40 days, 42 days, 44 days or 45 days, but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0030] Preferably, a substance containing hydroxide is additionally added to the aqueous solution before the standing.

[0031] Preferably, the hydroxide-containing substance includes any one of sodium hydroxide, potassium hydroxide or lithium hydroxide, or a combination of at least two of them. Typical but non-limiting examples of the combination include a combination of sodium hydroxide and potassium hydroxide, a combination of sodium hydroxide and lithium hydroxide, or a combination of potassium hydroxide and lithium hydroxide.

[0032] Preferably, after adding the hydroxide-containing substance, the pH of the aqueous solution is 7 to 8.5, for example, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.1, 8.3, 8.4 or 8.5, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0033] As mentioned above, due to the relatively slow self-transformation process, the diameter of the Se nanowires grown during room temperature stabilization is smaller, but the length is longer. In terms of optoelectronic performance, the smaller the diameter and the shorter the length of the Se nanowires, the better the performance. Adding a substance containing hydroxide or increasing the stabilization temperature can accelerate the self-transformation process, thus shortening the required stabilization time. However, while the self-transformation process is accelerated, the diameter of the grown Se nanowires will also increase, but the length will decrease. Therefore, relatively speaking, room temperature stabilization can provide better controllability by adjusting the stabilization time. However, the performance of the product obtained by room temperature stabilization is not necessarily the best, as the product's performance still depends on the proportion, size, and morphology of the Se nanowires and SnO2 nanosheets. Therefore, when accelerating the reaction process by heating or adding hydroxide, as long as the control is appropriate, for example, effectively reducing the length of the Se nanowires, the optoelectronic performance of the resulting nanocomposite material can be improved.

[0034] When a substance containing hydroxide is added or the standing temperature is increased, the pH value is preferably 7-8.5 or the temperature is 25-50°C. Within this range, the self-conversion process is relatively easier to control, thereby obtaining a product with better performance.

[0035] As a preferred technical solution of the present invention, the lateral size of the ultrathin SnSe nanosheet is ≤500nm, for example, it can be 500nm, 500nm, 450nm, 400nm, 350nm, 300nm, 250nm, 200nm, 150nm, 100nm, 50nm, 30nm or 10nm, etc., and the thickness is ≤20nm, for example, it can be 20nm, 18nm, 16nm, 14nm, 12nm, 10nm, 8nm, 6nm, 4nm or 2nm, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0036] Preferably, the method for preparing the ultrathin SnSe nanosheets comprises a liquid phase exfoliation method.

[0037] The present invention preferably adopts liquid phase exfoliation method to prepare the ultrathin SnSe nanosheets. SnSe nanosheets synthesized by chemical methods such as hydrothermal method can also be used. Since the SnSe nanosheets prepared by liquid phase exfoliation method have irregular morphology, high specific surface area and defect concentration, they are easier to self-transform into SnO2 / Se nanocomposites than SnSe nanosheets synthesized by wet chemical method.

[0038] Preferably, the liquid phase exfoliation method comprises the following steps:

[0039] The SnSe powder is dispersed in a solvent, subjected to a first centrifugation after ultrasonication, and the supernatant is collected. The solvent is added to the precipitate again, and the first centrifugation is performed after ultrasonication again, and the supernatant is collected. The process of adding the solvent, ultrasonication, and the first centrifugation is repeated until a sufficient amount of supernatant is collected, and a second centrifugation is performed to collect the precipitate to obtain ultrathin SnSe nanosheets.

[0040] As a preferred technical solution of the present invention, when the SnSe powder is dispersed in a solvent for the first time, the concentration of the SnSe powder is 0.01 to 0.03 g / mL, for example, 0.01 g / mL, 0.012 g / mL, 0.014 g / mL, 0.016 g / mL, 0.018 g / mL, 0.02 g / mL, 0.022 g / mL, 0.024 g / mL, 0.026 g / mL, 0.028 g / mL or 0.03 g / mL, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0041] Preferably, the solvent includes any one or a combination of at least two of 1-2-methylpyrrolidone, ethanol, isopropanol or deionized water. Typical but non-limiting examples of the combination include a combination of 1-2-methylpyrrolidone and ethanol, a combination of 1-2-methylpyrrolidone and isopropanol, a combination of 1-2-methylpyrrolidone and deionized water, a combination of ethanol and deionized water, a combination of ethanol and isopropanol, or a combination of isopropanol and deionized water.

[0042] Preferably, the power of the ultrasound is 300-500W, for example, 300W, 320W, 340W, 360W, 380W, 400W, 420W, 440W, 460W, 480W or 500W, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0043] Preferably, the ultrasound time is 1 to 3 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0044] Preferably, the ultrasonication is performed in an ice bath.

[0045] Preferably, the temperature of the ultrasound is -5 to 5°C, for example, -5°C, -4°C, -3°C, -2°C, -1°C, 0°C, 1°C, 2°C, 3°C, 4°C or 5°C, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0046] As a preferred technical solution of the present invention, the rotation speed of the first centrifuge is 3000-12000 rpm, for example, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm or 12000 rpm, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0047] The present invention obtains ultrathin SnSe nanosheets of different sizes by adjusting the rotational speed. When the rotational speed is higher, the size of the nanosheets that can be retained in the supernatant is smaller. The present invention uses multiple first centrifugations to discard the larger ultrathin SnSe nanosheets precipitated at the first centrifugal speed, retaining the smaller ultrathin SnSe nanosheets in the supernatant. These smaller ultrathin SnSe nanosheets need to be precipitated at a higher centrifugal speed to obtain. In other words, the first centrifugal speed determines the maximum size of the ultrathin SnSe nanosheets obtained. Then, the present invention uses a second centrifugation to precipitate some or all of the smaller ultrathin SnSe nanosheets in the supernatant. In other words, the second centrifugation further screens the ultrathin SnSe nanosheets in the supernatant. The second centrifugation speed determines the minimum size of the ultrathin SnSe nanosheets that can be obtained. Therefore, the present invention does not strictly limit the speed range of the first and second centrifugations. Those skilled in the art can reasonably match and select the speeds of the first and second centrifugations according to actual needs and experimental conditions to obtain ultrathin SnSe nanosheets of the target size.

[0048] Preferably, the first centrifugation time is 20 to 40 min, for example, 20 min, 24 min, 28 min, 32 min, 36 min or 40 min, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0049] Preferably, the process of adding solvent, sonication and first centrifugation is repeated 6 to 8 times, for example 6 times, 7 times or 8 times.

[0050] Preferably, the rotation speed of the second centrifugation is 12000-14000 rpm, for example, 12000 rpm, 12200 rpm, 12400 rpm, 12600 rpm, 12800 rpm, 13000 rpm, 13200 rpm, 13400 rpm, 13600 rpm, 13800 rpm or 14000 rpm, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0051] Preferably, the second centrifugation time is 50 to 70 min, for example, 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, 62 min, 64 min, 66 min, 68 min or 70 min, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0052] As a preferred technical solution of the present invention, after the second centrifugation, the obtained precipitate is dispersed in water and freeze-dried to obtain ultrathin SnSe nanosheets.

[0053] Preferably, the concentration of the obtained precipitate in water is controlled to be 0.05-0.3 g / mL, for example, 0.05 g / mL, 0.08 g / mL, 0.1 g / mL, 0.12 g / mL, 0.14 g / mL, 0.16 g / mL, 0.18 g / mL, 0.2 g / mL, 0.22 g / mL, 0.24 g / mL, 0.26 g / mL, 0.28 g / mL or 0.3 g / mL, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0054] Preferably, the freeze-drying temperature is -80 to -60°C, for example, -80°C, -78°C, -76°C, -74°C, -72°C, -70°C, -68°C, -66°C, -64°C, -62°C or -60°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0055] Preferably, the freeze-drying time is 24 to 72 h, for example, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, 50 h, 52 h, 54 h, 56 h, 58 h, 60 h, 62 h, 64 h, 66 h, 68 h, 60 h or 72 h, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0056] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0057] (1) Weigh 0.3-0.6 g of ground SnSe powder and disperse it in 20-25 mL of 1-methyl-2-pyrrolidone solvent; use a probe ultrasonicator with a power of 300-500 W to perform ice bath ultrasonication for 1-3 h, then perform a first centrifugation at 3000-12000 rpm for 20-40 min, and collect the supernatant; add an appropriate amount of 1-methyl-2-pyrrolidone solvent to the centrifugal precipitate, repeat the ultrasonication and perform the first centrifugation, and collect the supernatant; repeat the addition of solvent, ultrasonication and the first centrifugation for 6-8 times, collect a sufficient amount of supernatant, and perform a second centrifugation at 12000-14000 rpm for 50-70 min to obtain ultrathin SnSe NSs precipitation; then dispersing the precipitate in 2 to 4 mL of deionized water, and freeze-drying at -80 to -60 ° C for 24 to 72 hours to obtain ultrathin SnSe nanosheets, wherein the ultrathin SnSe nanosheets have a lateral size of ≤500 nm and a thickness of ≤20 nm;

[0058] (2) dispersing the obtained ultrathin SnSe nanosheets in an aqueous solution, controlling the concentration of the ultrathin SnSe nanosheets in the aqueous solution to be 0.1 to 1 mg / mL, and allowing the ultrathin SnSe nanosheets to stand at room temperature for 25 to 100 days or at 26 to 50° C. for 10 to 45 days, so that the ultrathin SnSe nanosheets undergo self-transformation until all SnSe is converted, thereby obtaining a SnO2 / Se nanocomposite material.

[0059] In a third aspect, the present invention provides an application of the SnO2 / Se nanocomposite material described in the first aspect or the SnO2 / Se nanocomposite material obtained by the preparation method described in the second aspect in the field of photoelectric conversion.

[0060] As a preferred technical solution of the present invention, compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0061] The present invention obtains SnO2 / Se nanocomposite materials by allowing ultrathin SnSe nanosheets obtained by liquid stripping to stand in an aqueous solution to cause self-transformation. The method is simple and convenient, and the process is stable and controllable. The obtained SnO2 / Se nanocomposite materials are composed of SnO2 nanosheets and Se nanowires. When applied to photodetectors, they have excellent light response performance. The obtained SnO2 / Se nanocomposite materials can also be used in gas sensors, energy storage devices, mode-locked lasers and other fields, which will provide more expansion opportunities for optical and optoelectronic applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is a scanning electron microscope image of the ultrathin SnSe nanosheet obtained in Example 1;

[0063] Figure 2 and Figure 3The scanning electron microscope image and low-magnification transmission electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 1 are respectively;

[0064] Figure 4 1 is an elemental analysis result diagram of the SnO2 / Se nanocomposite material obtained in Example 1;

[0065] Figure 5 is a scanning electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 5;

[0066] Figure 6 is a scanning electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 6;

[0067] Figure 7 is a scanning electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 7;

[0068] Figure 8 is a scanning electron microscope image of the nanocomposite material obtained in Example 10;

[0069] Figure 9 This is a scanning electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 14.

[0070] Figure 10 is a scanning electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 18;

[0071] Figure 11 18 is an elemental analysis result diagram of the SnO2 / Se nanocomposite material obtained in Example 18;

[0072] Figure 12 is a schematic diagram of a photoelectrode made of SnO2 / Se nanocomposite material;

[0073] Figure 13 is a schematic diagram of the three-electrode photoelectrochemical test system used in the application example;

[0074] Figure 14 and Figure 15 1 and 2 are linear sweep voltammetry curves of the photodetectors constructed in Example 1 and Example 10, respectively;

[0075] Figure 16 and Figure 17 Graphs showing changes in photocurrent of the photodetectors constructed in Example 1 and Example 10 when a potential is applied;

[0076] Figure 18 and Figure 19 They are the light response It curves corresponding to the photodetectors constructed in Example 1 and Example 10 at different light power densities;

[0077] Figure 20 and Figure 21 2 are the light response It curves of the photodetectors constructed in Example 1 and Example 10 at different light wavelengths;

[0078] Figure 22 Graph showing the functional relationship between the optical power density and the photocurrent of the photodetectors constructed in Example 1 and Example 10. DETAILED DESCRIPTION

[0079] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0080] Example 1

[0081] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof, wherein the preparation method comprises the following steps:

[0082] (1) Weigh 0.4 g of ground SnSe powder and disperse it in 22 mL of 1-methyl-2-pyrrolidone solvent; use a 360 W probe ultrasonicator to sonicate in an ice bath for 2 h, then perform a first centrifugation at 5000 rpm for 30 min, and collect the supernatant; add an appropriate amount of 1-methyl-2-pyrrolidone solvent to the centrifugal precipitate, repeat the sonication, and perform a first centrifugation, and collect the supernatant; repeat the addition of solvent, sonication, and first centrifugation for a total of 7 times, collect a sufficient amount of supernatant, and perform a second centrifugation at 12000 rpm for 60 min to obtain a precipitate of ultrathin SnSe NSs; then disperse the precipitate in 3 mL of deionized water, and freeze-dry at -80 ° C for 48 h to obtain ultrathin SnSe nanosheets;

[0083] (2) The obtained ultrathin SnSe nanosheets are dispersed in an aqueous solution, the concentration of the ultrathin SnSe nanosheets in the aqueous solution is controlled to be 1 mg / mL, and the solution is allowed to stand at room temperature for 90 days to allow the ultrathin SnSe nanosheets to undergo self-transformation until all SnSe is converted, thereby obtaining a SnO2 / Se nanocomposite material.

[0084] Example 2

[0085] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that in step (2), the concentration of the ultrathin SnSe nanosheets in the aqueous solution is adjusted from 1 mg / mL to 0.1 mg / mL, and the standing time at room temperature is adjusted from 90 days to 30 days.

[0086] Example 3

[0087] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the rotation speed of the second centrifuge is adjusted from 12000 rpm to 5000 rpm in step (1) and the standing time at room temperature is adjusted from 90 days to 150 days in step (2).

[0088] Example 4

[0089] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the rotation speed of the second centrifuge is adjusted from 12000 rpm to 5000 rpm in step (1).

[0090] Example 5

[0091] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the rotation speed of the second centrifuge is adjusted from 12000 rpm to 8000 rpm in step (1).

[0092] Example 6

[0093] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the rotation speed of the second centrifuge is adjusted from 12000 rpm to 14000 rpm in step (1).

[0094] Example 7

[0095] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the concentration of ultrathin SnSe nanosheets in the aqueous solution is adjusted from 1 mg / mL to 0.1 mg / mL in step (2).

[0096] Example 8

[0097] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the concentration of ultrathin SnSe nanosheets in the aqueous solution is adjusted from 1 mg / mL to 0.5 mg / mL in step (2).

[0098] Example 9

[0099] This embodiment provides a nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the concentration of ultrathin SnSe nanosheets in the aqueous solution is adjusted from 1 mg / mL to 1.5 mg / mL in step (2).

[0100] Example 10

[0101] This embodiment provides a nanocomposite material and a preparation method thereof. The preparation method is identical to that of embodiment 1 except that the standing time at room temperature is adjusted from 90 days to 30 days in step (2).

[0102] Example 11

[0103] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the standing time at room temperature is adjusted from 90 days to 100 days in step (2).

[0104] Example 12

[0105] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. The preparation method is identical to that of Example 1 except that the standing time at room temperature is adjusted from 90 days to 120 days in step (2).

[0106] Example 13

[0107] This embodiment provides a nanocomposite material and a preparation method thereof. In the preparation method, heating and standing are performed in step (2). The heating temperature is 35° C. and the standing time is 24 days. Other conditions are exactly the same as those in Example 1.

[0108] Example 14

[0109] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. In the preparation method, heating and standing are performed in step (2). The heating temperature is 35°C and the standing time is 45 days. Other than that, the other conditions are exactly the same as those in Example 1.

[0110] Example 15

[0111] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. In the preparation method, heating and standing are performed in step (2). The heating temperature is 70°C and the standing time is 10 days. Other than that, the other conditions are exactly the same as those in Example 1.

[0112] Example 16

[0113] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. In the preparation method, in step (2), 1 μL of 2M NaOH is added to an aqueous solution of ultrathin SnSe nanosheets and the mixture is allowed to stand until the reaction is complete. Other than this, the other conditions are exactly the same as those in Example 1.

[0114] Example 17

[0115] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. In the preparation method, in step (2), 10 μL of 2M NaOH is added to the aqueous solution of ultrathin SnSe nanosheets and the mixture is allowed to stand until the reaction is complete. Other than this, the other conditions are exactly the same as those in Example 1.

[0116] Example 18

[0117] This embodiment provides a SnO2 / Se nanocomposite material and a preparation method thereof. In the preparation method, in step (2), 100 μL of 2M NaOH is added to the aqueous solution of ultrathin SnSe nanosheets and the mixture is allowed to stand until the reaction is complete. Other than this, the other conditions are exactly the same as those in Example 1.

[0118] Comparative Example 1

[0119] This comparative example provides a SnO2 / Se nanocomposite material and a preparation method thereof. In the preparation method, no liquid phase exfoliation is performed in step (1), and SnSe powder is directly dispersed in an aqueous solution in step (2). Other than this, the other conditions are exactly the same as those in Example 1.

[0120] control group

[0121] In this control group, the ultrathin SnSe nanosheets obtained in Example 1 were used as subsequent test materials.

[0122] Figure 1 This is a scanning electron microscope image of the ultrathin SnSe nanosheets obtained in Example 1. It can be seen that the ultrathin SnSe nanosheets are in the form of nanosheets and are in the form of black powder. The ultrathin SnSe nanosheets are still black when the aqueous dispersion obtained by dispersing them in the aqueous solution in step (2). After the self-conversion occurs, the aqueous dispersion spontaneously turns into reddish brown. The degree of self-conversion can be judged by the depth of the reddish brown color.

[0123] Figure 2 and Figure 3 The scanning electron microscope image and low-magnification transmission electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 1 are respectively; the reddish-brown product of the SnO2 / Se nanocomposite material shows the formation of many criss-cross nanowires, the diameter of the nanowires is about 50nm, and some nanosheets are distributed and attached to the surface of the nanowires.

[0124] Figure 4 This is the elemental analysis result diagram of the SnO2 / Se nanocomposite material obtained in Example 1, including the element mapping and EDS results under STEM, which confirms that the nanowire structure in the SnO2 / Se nanocomposite material is mainly composed of Se elements, while the nanosheets are mainly composed of Sn and O elements. The EDS spectrum shows that the mass fractions of Se, Sn and O in the test sample are 49.00wt%, 38.56wt% and 12.44wt%, respectively, confirming that the sample is a SnO2 / Se nanocomposite material.

[0125] Figure 5-Figure 8 The following are scanning electron microscope images of SnO2 / Se nanocomposites obtained in Example 5, Example 6, Example 7 and Example 10 respectively. Figure 2 、 Figure 5 and Figure 6 The comparison found that for the same standing time and the same concentration of ultrathin SnSe nanosheet dispersion, the diameter of Se nanowires depends on the size of ultrathin SnSe nanosheets. The smaller the size of SnSe nanosheets, the smaller the diameter of Se nanowires. Figure 5 The Se nanowires in the sample have large diameters and poor performance. Figure 6 The Se nanowires in the reactor have a small diameter and therefore have better performance. Figure 2 and Figure 7 It can be seen from the comparison that for the same ultra-thin SnSe nanosheet size and standing time, the length of Se nanowires is related to the concentration of ultra-thin SnSe nanosheets. The higher the concentration, the longer the Se nanowires. Figure 2 and Figure 8 The comparison shows that when the size and concentration of ultra-thin SnSe nanosheets are the same, the length of Se nanowires is related to the static time. The longer the static time, the greater the proportion of Se nanowires, the larger the diameter, and the longer the length.

[0126] Figure 9 This is a scanning electron microscope image of the SnO2 / Se nanocomposite material obtained in Example 14. Heating can accelerate the self-transformation. Se rice noodles are generated in the obtained composite material, but the length is shorter than that of Example 1 and the diameter is larger.

[0127] Figure 10 Example 18: Scanning electron micrograph of the SnO2 / Se nanocomposite material obtained. A small amount of (OH) -The chemical process can be significantly accelerated. In Example 18, 100 μL of 2M NaOH aqueous solution was added to 10 mL of 1 mL / mg ultrathin SnSe nanosheet aqueous solution. The color of the solution can be changed from black to reddish brown within 10 minutes. The reddish brown product is composed of a large number of particles larger than 2 μm. The cross section of the typical particles is a regular hexagon, which is consistent with the structure of selenium single crystals. The SEM image of the reddish brown product was taken and the energy dispersive X-ray spectroscopy (EDS) analysis results are shown as follows: Figure 11 As shown in the figure, the calculated contents of Se, Sn, and O are 94.22wt%, 4.09wt%, and 1.69wt%, respectively. The atomic ratio of Sn to O is about 1:2.2, which is SnO2 nanoparticles. It can be seen that the excess (OH) - Reacts with SnO2 to form Sn(OH)6 2- Ions are the cause of the sharp decrease in Sn elements. Based on the above results and analysis, it can be inferred that the chemical reaction of the self-transformation process is as follows:

[0128] SnSe+4OH -1 →xSnO2+(1-x)Sn(OH)6 2- +Se+2xH +

[0129] Under ideal conditions, x is 0.5. The reason why this process is very slow under simple room temperature conditions is that the reaction relies on the stable ionization of water to produce OH -1 Ions (room temperature ~10 -7 mol / L(OH) - ions), therefore, the transition process is longer, and the self-transformation process is controllable at this time. A small amount of (OH) - It will accelerate the self-transformation process, and the excess (OH) - This will result in the inability to generate SnO2 / Se nanocomposites.

[0130] Application Examples

[0131] In order to evaluate the photoelectric detection performance of the nanocomposites obtained in the examples and comparative examples, the nanocomposites were deposited on an ITO substrate (2×1 cm 2 ) is coated with the obtained nanocomposite material to prepare a photoelectrode (working electrode), such as Figure 12 As shown, and through Figure 13 The three-electrode photoelectrochemical (PEC) test system shown in the figure constitutes a photodetector to evaluate the light response performance of the obtained nanocomposite material, wherein WE is the working electrode, CE is the counter electrode, RE is the reference electrode, the electrolyte is 0.5M Na2SO4, the light source is white light with 5 levels of power intensity, and light of different wavelengths is obtained through filters. The light powder density (P λ), unit is mW / cm 2 All are listed in Table 1.

[0132] Table 1

[0133] wavelength White light 400nm 550nm 600nm 700nm Power intensity level I 12.28 0.52 0.86 1.04 1.19 Power intensity level II 20.73 0.88 1.45 1.76 1.87 Power intensity level III 28.26 1.20 1.98 2.40 2.54 Power intensity level IV 33.92 1.44 2.37 2.88 3.05 Power intensity level V 37.69 1.60 2.64 3.20 3.39

[0134] Figure 14 and Figure 15 The linear sweep voltammetry curves of the photodetectors constructed using the nanocomposites obtained in Example 1 and Example 10 under medium cycle on / off white light are shown. In the potential range of 0-1.2 V, the dark current of the SnO2 / Se photodetector in Example 1 is slightly higher, while the photocurrent (i.e., I light -I dark ) are significantly higher than the values ​​of the photodetector obtained in Example 10.

[0135] like Figure 16 and Figure 17 As shown, as the applied potential increases, the photocurrent of both devices first decreases slightly, then remains flat until it reaches around 1V, before rapidly increasing. The difference between the work function of the semiconductor working electrode and the electrolyte redox potential generates a built-in electric field, giving the PEC photodetector its self-powered nature. Consequently, the device generates a built-in electric field of ~0.3V, which causes a slight decrease in photocurrent as the applied potential increases from 0 to 0.3V. Given that the dark current of the photodetector is stable at a potential of 0.6V, the photoresponse performance of the photodetector at 0.6V was further systematically investigated.

[0136] Figure 18 and Figure 19 It curves of the light response of the photodetector composed of the nanocomposite material obtained in Example 10 and the SnO2 / Se nanocomposite material of the embodiment under irradiation of 12.25-37.69 mW / cm2 white light. Figure 20 and Figure 21 The photoresponse It curves of the two under irradiation with light of different power densities at wavelengths of 400 to 700 nm respectively are shown. It can be seen that for white light and the above four wavelengths, the photocurrent increases steadily with the increase of light intensity.

[0137] The power function is usually used to describe the relationship between optical power density and photocurrent, which can be expressed as follows:

[0138]

[0139] Among them, P light is the incident light power density, photocurrent density (I ph ) is a direct parameter of the photodetector and can be calculated by the following formula:

[0140]

[0141] Among them I light -I dark is the current of the photodetector under light and darkness, S device is the ITO area coated with nanocomposite (~2cm 2 ).

[0142] Figure 22 The functional relationship diagram of the optical power density and photocurrent of the photodetectors constructed in Example 1 and Example 10 shows that the α values ​​under white light are 0.91 and 0.78, respectively. In addition, it is calculated that the α values ​​of the photodetector constructed in Example 10 at wavelengths of 400, 550, 600, and 700 nm are 0.73, 0.89, 0.75, and 0.92, respectively. Under the same test conditions, the α values ​​of the SnO2 / Se photodetector constructed in Example 1 are 0.88, 0.88, 0.86, and 0.93, respectively, as shown in Table 2. For an ideal photoelectric conversion process, the α value is 1. However, due to the complex photoelectric conversion process caused by trap states or light gating effects, the measured α value is usually less than 1. Secondly, the α value of the SnO2 / Se photodetector constructed in Example 1 is closer to 1, indicating that its intrinsic photoelectric conversion efficiency is higher.

[0143] Table 2

[0144] α value White light 400nm 550nm 600nm 700nm Example 1 0.91 0.88 0.88 0.86 0.93 Example 11 0.78 0.73 0.89 0.86 0.93

[0145] At a potential of 0.6 V, the photoresponsivity (R) and specific detectivity (D*) of the photodetectors constructed in Examples 1 to 18 were tested and calculated according to the following formula:

[0146]

[0147] Among them, P light is the incident light power density, I ph refers to the photocurrent density, q is the electron charge (1.6×10 -19 C), I dark is the current in the dark, S device is the ITO area coated with nanocomposite (~2cm 2 ).

[0148] The data of other embodiments, comparative examples and control groups were also tested, and the above results are recorded in Table 3.

[0149] Table 3

[0150]

[0151]

[0152] As can be seen from Table 3:

[0153] (1) Comparison between the control group and Example 1 shows that when the ultrathin SnSe nanosheets are completely converted into SnO2 / Se nanocomposites, the key photoresponse parameters are significantly enhanced, with photocurrent, R, and D* increasing by 282.3 times, 465.8 times, and 20 times, respectively. Furthermore, the SnO2 / Se photodetector exhibits excellent photoresponse performance and stability and can also be used as a self-powered photodetector with an operating voltage of 0V. The excellent photoresponse performance of the novel SnO2 / Se nanocomposite will provide expanded opportunities for optical and optoelectronic applications.

[0154] (2) Comparing Example 1 with Examples 4-5, the SnSe obtained by low-speed centrifugation in Examples 4 and 5 are large in size and cannot be completely converted into Se / SnO2 nanocomposites in the same time, and the grown nanowires are larger in size, and the photoelectric detection performance is significantly improved; comparing Example 1 with Example 6, the SnSe obtained by high-speed centrifugation are similar in size, SnSe can be completely converted into Se / SnO2 nanocomposites, and the nanowire diameters are comparable, and the photoelectric detection performance is comparable.

[0155] (3) Compared with Example 1 and Example 7, the SnSe concentration in Example 1 is high, the generated nanowire concentration is high, and the photoelectric performance is significantly improved; compared with Example 1 and Example 8, the SnSe concentration in Example 8 is slightly lower, the generated nanowires are slightly larger, and the photoelectric detection performance is equivalent; compared with Example 1 and Example 9, the SnSe concentration in Example 9 is large, and it cannot be completely converted into Se / SnO2 nanocomposite material in the same time. Therefore, the obtained composite material contains unconverted ultrathin SnSe nanosheets and Se / SnO2 nanocomposite material, which is recorded as SnSe / SnO 2 / Se nanocomposite material, but the photoelectric detection performance of Example 9 is also significantly improved compared with that of Comparative Example 1 and the control group.

[0156] (4) Comparing Example 1 with Example 10, Example 10 has a short standing time and is not completely converted into Se / SnO2 nanocomposite material. 2 / Se nanocomposite materials, but the photoelectric detection performance of Example 10 is significantly improved compared with that of Comparative Example 1 and the control group; compared with Examples 11-12, the SnSe nanosheets in Examples 11-12 are completely converted into SnO2 / Se nanocomposites, and the material structure will not change if the standing time is further increased, so the photoelectric detection performance is equivalent to that of Example 1.

[0157] (5) Under heat-assisted self-conversion, Example 13 had a short self-conversion time and was not completely converted into a Se / SnO2 nanocomposite material. Compared with Example 1, its photoelectric performance was poor. Example 14 had a long self-conversion time and was completely converted into a SnO2 / Se nanocomposite material. The nanowires had a significantly smaller diameter but a longer length, and its photoelectric detection performance was comparable to that of Example 1. Example 15 used a higher heating temperature, had a shorter self-conversion time, and its nanowires were closer to large particles. Compared with Example 1, its performance was significantly worse.

[0158] (6) After adding sodium hydroxide, the self-conversion time of Example 16 is shortened. Compared with Example 1, the self-conversion time of Example 1 is slightly longer, the nanowire diameter is small but the length is long, so the photoelectric detection performance is equivalent; Example 17 increases the amount of sodium hydroxide, and the Se grown in Example 17 is between nanowires and particles. Compared with Example 1, the photoelectric detection performance is slightly worse. Example 18 further increases the amount of sodium hydroxide, and the nanowires grown in Example 18 in a short time are close to large particles, and the photoelectric detection performance is the worst.

[0159] (7) Compared with Comparative Example 1, Example 1 shows a significant improvement in photodetection performance, with photocurrent, R, and D* increasing by 571.8 times, 931.6 times, and 41.5 times, respectively.

[0160] While the present invention is described through the above-described embodiments to illustrate the detailed structural features of the present invention, the present invention is not limited to these detailed structural features, nor does it necessarily rely on these detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0161] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0162] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0163] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A SnO2 / Se nanocomposite material, characterized in that: Comprising Se nanowires and SnO2 nanosheets, wherein the SnO2 nanosheets are dispersed between the Se nanowires and / or supported on the Se nanowires; Based on the mass of the SnO2 / Se nanocomposite material being 100 wt%, the Se nanowires account for 30-98 wt%, and the SnO2 nanosheets account for 2-70 wt%.

2. The SnO2 / Se nanocomposite material according to claim 1, characterized in that In the SnO2 / Se nanocomposite material, the diameter of the Se nanowire is 20-200 nm, and the length is 200 nm-2 μm.

3. The SnO2 / Se nanocomposite material according to claim 1, characterized in that In the SnO2 / Se nanocomposite material, the thickness of the SnO2 nanosheet is ≤15nm, and the diameter is less than or equal to 300nm.

4. The method for preparing the SnO2 / Se nanocomposite material according to any one of claims 1 to 3, characterized in that: The steps include: The ultrathin SnSe nanosheets are dispersed in an aqueous solution and allowed to stand to self-convert until all SnSe is converted, thereby obtaining a SnO2 / Se nanocomposite material. The concentration of the ultrathin SnSe nanosheets in the aqueous solution is 0.1-1 mg / mL, and the standing includes standing at room temperature for 25-100 days or at 26-50° C. for 10-45 days; The method for preparing the ultrathin SnSe nanosheets includes a liquid phase exfoliation method, which includes the following steps: The SnSe powder is dispersed in a solvent, subjected to a first centrifugation after ultrasonication, and the supernatant is collected. The solvent is added to the precipitate again, and the first centrifugation is performed after ultrasonication again, and the supernatant is collected. The process of adding the solvent, ultrasonication, and the first centrifugation is repeated until a sufficient amount of supernatant is collected, and a second centrifugation is performed to collect the precipitate to obtain an ultrathin SnSe nanosheet. The rotation speed of the second centrifugation is 12000-14000 rpm.

5. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: Before the standing, a hydroxide-containing substance is additionally added to the aqueous solution.

6. The method for preparing the SnO2 / Se nanocomposite material according to claim 5, characterized in that: The hydroxide-containing substance includes any one of sodium hydroxide, potassium hydroxide or lithium hydroxide, or a combination of at least two of them.

7. The method for preparing the SnO2 / Se nanocomposite material according to claim 5, characterized in that: After the hydroxide-containing substance is added, the pH of the aqueous solution is 7 to 8.

5.

8. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The ultra-thin SnSe nanosheet has a lateral size of ≤500nm and a thickness of ≤20nm.

9. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: When the SnSe powder is dispersed in a solvent for the first time, the concentration of the SnSe powder is 0.01-0.03 g / mL.

10. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The solvent includes 1-methyl-2-pyrrolidone.

11. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The power of the ultrasound is 300-500W.

12. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The ultrasound time is 1 to 3 hours.

13. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The ultrasonication was performed in an ice bath.

14. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The temperature of the ultrasound is -5~5°C.

15. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The rotation speed of the first centrifugation is 3000~12000rpm.

16. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The first centrifugation time is 20-40 min.

17. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The process of adding solvent, sonication and the first centrifugation was repeated 6 to 8 times.

18. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The second centrifugation time is 50-70 min.

19. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: After the second centrifugation, the obtained precipitate was dispersed in water and freeze-dried to obtain ultrathin SnSe nanosheets.

20. The method for preparing the SnO2 / Se nanocomposite material according to claim 19, characterized in that: The concentration of the obtained precipitate in water was controlled to be 0.05~0.3g / mL.

21. The method for preparing the SnO2 / Se nanocomposite material according to claim 19, characterized in that: The freeze-drying temperature is -80~-60°C.

22. The method for preparing the SnO2 / Se nanocomposite material according to claim 19, characterized in that: The freeze-drying time is 24 to 72 hours.

23. The method for preparing the SnO2 / Se nanocomposite material according to claim 4, characterized in that: The steps include: (1) Weigh 0.3-0.6 g of ground SnSe powder and disperse it in 20-25 mL of 1-methyl-2-pyrrolidone solvent; use a 300-500 W power probe ultrasonicator to perform ice bath ultrasonication for 1-3 h, then perform the first centrifugation at 3000-12000 rpm for 20-40 min, and collect the supernatant; add an appropriate amount of 1-methyl-2-pyrrolidone solvent to the centrifugal precipitate, repeat the ultrasonication and perform the first centrifugation, and collect the supernatant; repeat the addition of solvent, ultrasonication and the first centrifugation for 6-8 times, collect enough supernatant, and perform the second centrifugation at 12000-14000 rpm for 50-70 min to obtain ultrathin SnSe NSs precipitation; then dispersing the precipitate in 2~4mL of deionized water, and freeze-drying at -80~-60℃ for 24~72h to obtain ultrathin SnSe nanosheets, wherein the ultrathin SnSe nanosheets have a lateral size of ≤500nm and a thickness of ≤20nm; (2) The obtained ultrathin SnSe nanosheets are dispersed in an aqueous solution, the concentration of the ultrathin SnSe nanosheets in the aqueous solution is controlled to be 0.1-1 mg / mL, and the ultrathin SnSe nanosheets are allowed to stand at room temperature for 25-100 days or at 26-50°C for 10-45 days to allow the ultrathin SnSe nanosheets to undergo self-transformation until all SnSe is converted, thereby obtaining a SnO2 / Se nanocomposite material.

24. Use of the SnO2 / Se nanocomposite material according to any one of claims 1 to 3 or the SnO2 / Se nanocomposite material obtained by the preparation method according to any one of claims 4 to 23 in the field of photoelectric conversion.

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