Fluorine-doped tin selenide and preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of gas sensor materials, and particularly relates to fluorine-doped tin selenide as well as a preparation method and application thereof. The fluorine-doped tin selenide is of a nanosheet structure and is in a transversely expanded ultrathin nanosheet form, and the thickness of the fluorine-doped tin selenide is 1 nm-10 nm; the fluorine ions are inserted between the tin selenide layers and cause lattice distortion, and at least part of the fluorine ions are adsorbed on the (001) crystal face. The gas sensor based on the fluorine-doped tin selenide has a response value up to 226.93% to 10ppm NO at room temperature, a detection limit as low as 400ppb, response time of 106.13 seconds and performance fluctuation of less than 15% in a high-humidity environment (greater than or equal to 60% RH), and shows excellent moisture resistance and stability. Besides, in a nitrogen-containing gas circulation test, the material has higher response characteristics (response values are respectively 243.93% and 206.54%) on NO and NO2, and the response characteristics are obviously superior to those on gases such as H2S, NH3 and VOCs.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas sensor material preparation, and particularly relates to fluorine-doped tin selenide as well as a preparation method and application thereof. BACKGROUND

[0002] With the increasing demand in the fields of environmental monitoring, industrial safety and medical diagnosis, the research and development of high-performance gas sensors have become a research hotspot in the fields of materials and sensors. Among them, as a typical atmospheric pollutant and biomarker, nitric oxide (NO) has important significance for real-time monitoring due to its high sensitivity, low detection limit and room-temperature working performance. However, the existing gas sensing materials still have significant technical bottlenecks: traditional metal oxide semiconductors (such as SnO2 and ZnO) are easily disturbed by environmental humidity; although noble metal doping (such as Pt / SnO2) can improve the response performance, it is high in cost and scarce in resources, which limits its large-scale application.

[0003] In recent years, tin selenide (SnSe2) based two-dimensional materials have shown potential in the field of gas sensing due to their layered structure, high specific surface area and adjustable electronic properties. In the prior art, researchers have constructed heterostructures or composite systems to optimize their gas sensing performance, for example: CN114646669B discloses a tin disulfide / tin diselenide lateral heterostructure prepared by a liquid phase ion replacement method, which realizes rapid response to NO2 at room temperature, but the heterostructure has the problems of low lattice matching degree between components and many interface defects, which limits the charge transport efficiency; CN118666249A adopts a tungsten diselenide / tin diselenide / tin monoselenide ternary heterostructure, which improves the selectivity of NO2 detection, but the preparation process needs to accurately control the proportion of multiple components, which is high in process complexity and poor in repeatability. In addition, the existing tin selenide-based materials are mostly designed for NO2 detection, and the response sensitivity to NO is generally low (response value <100%), and the performance fluctuation in a high humidity environment (≥60% RH) is more than 20%, which is difficult to meet the actual application requirements.

[0004] In view of the above problems, it is crucial to develop a tin selenide-based material that does not require a heterostructure design and can realize high-sensitivity NO detection through intrinsic regulation. In the prior art, single tin selenide materials have difficulty in breaking through the gas sensing performance due to insufficient surface active sites and low interlayer charge mobility; and element doping as an effective means to regulate the electronic structure of semiconductor materials has not been reported in the tin selenide system. Therefore, how to optimize the interlayer structure and surface adsorption characteristics of tin selenide through a simple and efficient doping strategy to realize high response, low detection limit and excellent humidity resistance to NO at room temperature is a technical problem to be solved in the field. SUMMARY

[0005] Based on this, the fluorine-doped tin selenide is prepared by the "intercalation-recrystallization" formation mechanism of intercalating fluorine ions first and then inducing recrystallization to form ultra-thin nanosheets, has excellent selectivity and high responsiveness to NO, and has excellent stability in a high-humidity environment.

[0006] In order to achieve the above-mentioned purpose, the present application can adopt the following technical solutions: The present application provides a kind of fluorine-doped tin selenide in one aspect, it is nanosheet structure, with the following characteristics: (i) the morphology of transverse extension ultra-thin nanosheet, thickness is 3nm-5nm;(ii) fluorine ion inserts tin selenide interlayer and triggers lattice distortion, and at least part of fluorine ion is adsorbed on (001) crystal face.

[0007] The present application provides a kind of preparation method of fluorine-doped tin selenide in another aspect, and the preparation method comprises: (1) tin selenide is dispersed into water to obtain dispersion liquid;(2) fluorine-doped tin selenide is obtained after the dispersion liquid is mixed with ammonium fluoride and then hydrothermal reaction is carried out.

[0008] Preferably, in the above preparation method, the addition amount of ammonium fluoride is 1wt%-10wt% of the mass of tin selenide.

[0009] More preferably, in the above preparation method, the addition amount of ammonium fluoride is 4wt% of the mass of tin selenide.

[0010] Preferably, in the above preparation method, (a) the temperature of hydrothermal reaction is 160℃-200℃;And / or (b) the hydrothermal reaction time based on temperature (a) is ≥12h.

[0011] Preferably, in the above preparation method, the preparation method of tin selenide comprises: (1) selenium powder and sodium borohydride are mixed with water to obtain a selenium precursor solution;(2) tin selenide is obtained after the selenium precursor solution and the aqueous solution of stannous chloride dihydrate are mixed and then hydrothermal reaction is carried out.

[0012] The present application provides a kind of gas sensor in another aspect, which includes the above-mentioned fluorine-doped tin selenide or the fluorine-doped tin selenide prepared by the above-mentioned preparation method.

[0013] The present application provides a kind of fluorine-doped tin selenide or the fluorine-doped tin selenide prepared by the above-mentioned preparation method or the above-mentioned gas sensor in still another aspect in the application of detecting or monitoring gas.

[0014] Preferably, in the above application, the gas is nitric oxide and / or nitrogen dioxide.

[0015] More preferably, the above-mentioned application includes: the application in detecting or monitoring gas in a high-humidity environment, and the humidity of the high-humidity environment is ≥60% RH.

[0016] The present application has at least the following beneficial effects: the gas sensor of the fluorine-doped tin selenide provided by the present application has a response value of up to 226.93% (4wt% F-doped) to 10 ppm NO at room temperature, a detection limit as low as 400 ppb, a response time of 106.13 seconds, and a performance fluctuation of less than 15% in a high-humidity environment (≥60% RH), showing excellent humidity resistance and stability. In addition, in the nitrogen-containing gas circulation test, the material has higher response characteristics (response values of 243.93% and 206.54% respectively) to NO and NO2, which are significantly better than the response to H2S, NH3, VOCs and other gases, overcoming the bottleneck of poor selectivity of traditional sensors. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Response characteristics of the fluorine-doped tin selenide in the present application to different gases; Figure 2 Response time of the fluorine-doped tin selenide in the present application to NO; Figure 3 Humidity resistance of the fluorine-doped tin selenide in the present application; Figure 4 Detection limit of the fluorine-doped tin selenide in the present application to NO; Figure 5 Stability of the fluorine-doped tin selenide in the present application. DETAILED DESCRIPTION

[0018] The examples are provided to better illustrate the present application, but the present application is not limited to the examples. Therefore, those skilled in the art can make non-essential improvements and adjustments to the embodiments according to the above disclosure, which still fall within the scope of the present application.

[0019] The terms used herein are used only to describe specific embodiments and are not intended to limit the present disclosure. Unless otherwise apparent in context, the singular forms "an," "a," and "the" include plural references. As used herein, it should be understood that terms such as "include," "have," "contain," "comprise," etc. are intended to indicate the presence of the features, numbers, operations, components, parts, elements, materials, or combinations. The terms of the present application are disclosed in the specification, and are not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations can exist or can be added. As used herein, " / " can be interpreted as "and" or "or" depending on the circumstances.

[0020] In a first aspect, the embodiments of the present application provide a fluorine-doped tin selenide, which is a nanosheet structure and has the following characteristics: (i) a transversely expanded ultrathin nanosheet morphology with a thickness of 3-5 nm; (ii) Fluoride ions intercalate into the SnSe layers and induce lattice distortion, and at least part of the fluoride ions are adsorbed on the (001) crystal surface.

[0021] It should be noted that the fluorine-doped tin selenide in the present application realizes directional regulation of the crystal morphology and electronic structure of tin selenide (SnSe). Fluoride ions, with a small ionic radius, intercalate into the SnSe layers, induce lattice distortion, and are preferentially adsorbed on the (001) crystal surface, thereby inhibiting longitudinal growth and promoting lateral expansion to form ultrathin nanosheets (3-5 nm thick). This process is accompanied by a dissolution-recrystallization mechanism, and finally, SnSe nanomaterials with high crystallinity, high specific surface area, and uniform F element doping are obtained. The formation mechanism of the fluorine-doped tin selenide in the present application is a "intercalation-recrystallization" formation mechanism in which fluoride ions first intercalate and then induce recrystallization to form ultrathin nanosheets. In addition, the fluoride ions in the present application not only increase the interlayer spacing and provide more gas adsorption sites, but also reduce the electron cloud density of Sn sites through strong electronegativity, thereby enhancing the adsorption energy and charge transfer efficiency of NO, and significantly improving the room temperature sensitivity and selectivity.

[0022] It should be further noted that "lateral expansion" in the present application specifically refers to an increase in the size along the a-axis and b-axis directions, while the c-axis direction perpendicular to the layered plane (i.e., the thickness) is effectively inhibited. "Lattice distortion" refers to the fact that F ions have a smaller atomic radius than Sn and Se. After being doped into the SnSe compound, the c-axis interlayer spacing is locally expanded, while a tensile stress is generated on the surrounding Sn-Se bonds, causing slight bending, wrinkling, and misalignment of the (001) crystal surface, resulting in a strained, non-perfect flat layered morphology of SnSe. "Adsorption on the (001) crystal surface" refers to the fact that the (001) crystal surface is a truncated surface of the periodic arrangement of atoms in different directions within the crystal, which is formed due to the anisotropy of the accumulation rate of atoms in different directions during crystal growth. The (001) crystal surface is one of the common crystal surfaces of the SnSe compound, and the adsorption of F ions on this crystal surface inhibits the accumulation and growth of SnSe in the c-axis (i.e., the thickness) direction. In addition, F ions preferentially adsorb on the (001) crystal surface. The reason for the preferential adsorption is that the (001) crystal surface has the highest surface energy and the most unsaturated bonds, providing the most stable and lowest bonding site for the highly electronegative F ions, so F ions will preferentially choose this crystal surface for adsorption.

[0023] In a second aspect, the present application provides a preparation method of fluorine-doped tin selenide, which comprises: (1) dispersing tin selenide in water to obtain a dispersion liquid; (2) mixing the dispersion liquid with ammonium fluoride and then performing a hydrothermal reaction to obtain fluorine-doped tin selenide.

[0024] It should be noted that the present application can use ammonium fluoride (NH4F) as a fluorine source, react with tin selenide in the same hydrothermal reaction kettle, and directly generate fluorine-doped tin selenide (F-SnSe) nanomaterials, which is different from the existing method which needs multi-step synthesis, ion replacement or construction of heterojunction. The preparation method in the present application does not need high-temperature annealing, the process is simple, the cost is low, and it is suitable for large-scale preparation.

[0025] In some specific examples, in the above preparation method, the doping amount of fluorine is 1wt%-10wt% of the total mass of tin selenide and ammonium fluoride.

[0026] It should be noted that the doping amount of fluorine in the present application is 1wt%-10wt% of the total mass of tin selenide and ammonium fluoride, for example, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% or 9wt% and the like.

[0027] In some specific examples, in the above preparation method, the doping amount of fluorine is 4wt% of the total mass of tin selenide and ammonium fluoride.

[0028] It should be noted that the doping amount of fluorine in the present application can be preferably 4wt% of the total mass of tin selenide and ammonium fluoride, and the performance of fluorine-doped tin selenide prepared at a doping amount of 4wt% is better than that of other addition concentrations. The response value to 10ppm NO at room temperature is as high as 227.62% (4wt% F doping), the detection limit is as low as 400ppb, the response time is 105.9 seconds, and the performance fluctuation in a high humidity environment (80%RH) is less than 15%, which shows excellent humidity resistance and stability.

[0029] In some specific examples, in the above preparation method, (a) the temperature of the hydrothermal reaction is 160°C-200°C; and / or (b) the hydrothermal reaction time based on temperature (a) is ≥12h.

[0030] It should be noted that the temperature of the hydrothermal reaction can be preferably 160°C-200°C, such as 170°C, 180°C or 190°C and the like; the hydrothermal reaction time based on the temperature can be ≥12h, which can be selected from 12h-24h, and preferably 12h, which can obtain higher preparation efficiency in a shorter time.

[0031] In some specific examples, in the above preparation method, the preparation method of tin selenide comprises: (1) mixing selenium powder and sodium borohydride with water to obtain a selenium precursor solution; (2) mixing the selenium precursor solution and the stannous chloride dihydrate aqueous solution, and then performing hydrothermal reaction to obtain tin selenide.

[0032] It should be noted that the tin selenide in the present application can be commercially available or self-made according to the above preparation method. In addition, the hydrothermal reaction temperature in the above preparation method is 160-200°C (such as 170°C, 180°C or 190°C, etc.), and the reaction time is ≥12h (such as 12-24h).

[0033] In a third aspect, the embodiments of the present application provide a gas sensor comprising the fluorine-doped tin selenide or the fluorine-doped tin selenide prepared by the above preparation method.

[0034] It should be noted that the fluorine-doped tin selenide in the present application can be prepared into a gas sensor, which can realize multiple breakthroughs in sensing performance such as room temperature operation, high sensitivity, high selectivity and strong humidity resistance, and is suitable for on-site rapid detection requirements in the fields of environmental monitoring, occupational safety and forensic science.

[0035] In a fourth aspect, the embodiments of the present application provide the application of the above fluorine-doped tin selenide or the fluorine-doped tin selenide prepared by the above preparation method or the above gas sensor in detecting or monitoring a gas.

[0036] In some specific examples, in the above application, the gas is nitric oxide and / or nitrogen dioxide.

[0037] It should be noted that the fluorine-doped tin selenide in the present application and the gas sensor based on the fluorine-doped tin selenide have excellent selectivity to nitric oxide and / or nitrogen dioxide, especially to nitric oxide. Specifically, in the nitrogen-containing gas circulation test, the response values of the fluorine-doped tin selenide in the present application to NO and NO2 are 243.93% and 206.54%, respectively.

[0038] In some specific examples, the above application includes the application in detecting or monitoring a gas in a high-humidity environment, and the humidity of the high-humidity environment is ≥60% RH.

[0039] It should be noted that the fluorine-doped tin selenide in the present application and the gas sensor based on the fluorine-doped tin selenide can efficiently detect the gas in a high-humidity environment, and have excellent stability in a high-humidity environment.

[0040] In addition, the fluorine-doped tin selenide (F-SnSe) of the present application is also compared with some gas-sensitive materials in the prior art, as follows: (1) Compared with CN114646669B (SnS2 / SnSe2 lateral heterostructure) and CN118666249A (WSe2 / SnSe2 / SnSe ternary heterostructure), the above patents adopt a complex multi-phase heterostructure construction strategy, which requires accurate control of the proportion of multiple precursors, step-by-step reaction interface and lattice matching, the process is complex, the repeatability requirement is high, and defects are prone to occur at the heterojunction interface, affecting the carrier transport efficiency and stability; the method of the present application adopts a single-phase F-doping strategy, and the morphology of SnSe is controlled and the electronic structure is modified by a hydrothermal method, avoiding the compatibility and stability problems brought by the multi-phase interface, and the process is simpler, the cost is lower, and it is easy to scale up. In addition, the gas sensitive materials in the above patents are specifically used for NO2 sensing, and there is no record of high selective recognition of NO; and the method of the present application shows high response (227.62% response value of 10ppm NO) and high selectivity (response to NO is significantly higher than that of NO2 and other interfering gases) to NO at room temperature, which is different from the above patents. (2) Compared with patent CN103482589B, the patent relies on chemical vapor deposition (CVD) or high-temperature solvothermal method, which needs to be carried out in a high-temperature and inert atmosphere protection environment, and also needs to use a metal catalyst; the hydrothermal method (180°C) adopted by the present method does not need a catalyst, the atmosphere requirement is loose, and the process is environmentally friendly, which is different from the patent. In addition, the F-SnSe sensor developed by the present method can realize high sensitivity detection of NO at room temperature, and has excellent humidity resistance (humidity fluctuation influence <15%) and long-term stability, solving the common problem of weak room temperature response and poor environmental adaptability of traditional gas sensitive materials.

[0041] In order to better understand the present application, the content of the present application will be further illustrated below in combination with specific examples, but the content of the present application is not limited to the following examples only.

[0042] Preparation Examples In the following examples, "4wt% F-SnSe" means that the doping amount of fluorine (F) is 4wt% of the total mass of tin selenide and ammonium fluoride, and so on. The conversion of different F doping amounts and the addition amount of NH4F is as follows: (1) Calculate the molar mass of SnSe: The molar mass of SnSe = 118.71(Sn) + 78.96(Se) = 197.67 g / mol; (2) Calculate the mass of 2mmol (0.002mol) SnSe: Mass = 0.002mol x 197.67g / mol = 0.3953g (i.e. 395.3mg); (3) Let the mass of NH4F added be mg, and the doping amount of F element is calculated: The molar mass of NH4F = 14.01 (N) + 4 x 1.008 (H) + 18.998 (F) = 37.04 g / mol; The mass fraction of F in NH4F = 18.998 / 37.04 ≈ 0.5130 (i.e. 51.30%); The doping mass of F element = 0.5130 x mg.

[0043] (4) According to the mass percentage of F, the equation is set up: Total mass = SnSe mass + NH4F mass = 0.3953 g + mg When the doping amount of fluorine (F) is 1wt%, 2wt%, 6wt%, 8wt%, and 10wt% of the total mass of tin selenide and ammonium fluoride, the mass of ammonium fluoride (NH4F) is as follows: (0.5130 x m) / (0.3953 + m) = w / 100, i.e. m = (0.3953 x w) / (51.30 - w); the calculation results are as follows: 1wt% F → 7.85 mg NH4F; 2wt% F → 15.7 mg NH4F; 4wt% F → 32.0 mg NH4F; 6wt% F → 47.5 mg NH4F; 8wt% F → 65.0 mg NH4F; 10wt% F → 85.5 mg NH4F.

[0044] Example 1 (1) Selenium powder (2 mmol) and sodium borohydride (NaBH4, 250 mg) were added to 30 mL of deionized water and magnetically stirred (500 revolutions per minute, stirring for 10 minutes) at room temperature until a clear solution was formed to obtain a selenium precursor solution; stannous chloride hydrate (SnCl2·2H2O) (2 mmol) was added to 30 mL of deionized water and prepared to obtain a stannous chloride dihydrate (SnCl2·2H2O) solution; the stannous chloride dihydrate solution was added to the selenium precursor solution and stirred vigorously (800 revolutions per minute) at room temperature for 20 minutes to obtain a mixture A; (2) The mixture A was transferred to a stainless steel high-pressure reaction kettle lined with polytetrafluoroethylene and subjected to a hydrothermal reaction at 180°C for 12 hours; after the reaction was completed, the resulting reaction product A was naturally cooled to room temperature, then washed with deionized water and ethanol, and dried to obtain a SnSe powder; (3) 395 mg SnSe powder was dispersed in 30 mL deionized water to obtain a SnSe dispersion liquid, 32.0 mg of ammonium fluoride (NH4F) was added to the dispersion liquid, and then a mixture B was obtained by magnetic stirring at room temperature for 20 minutes (to ensure uniformity); (4) The mixture B was placed in a polytetrafluoroethylene-lined autoclave, and a hydrothermal reaction was carried out at 180°C for 12 hours; after the reaction was completed, the obtained reaction product B was collected by filtration; then the reaction product B was washed with deionized water and ethanol, and dried to obtain a fluorine-doped tin selenide powder (4wt% F-SnSe).

[0045] Example 2 Example 2 is substantially the same as Example 1, except that the amount of ammonium fluoride (NH4F) added in step (3) is different; wherein the amount of ammonium fluoride (NH4F) added in step (3) of Example 2 is 7.85 mg, and a fluorine-doped tin selenide powder (1wt% F-SnSe) is prepared.

[0046] Example 3 Example 3 is substantially the same as Example 1, except that the amount of ammonium fluoride (NH4F) added in step (3) is different; wherein the amount of ammonium fluoride (NH4F) added in step (3) of Example 3 is 15.7 mg, and a fluorine-doped tin selenide powder (2wt% F-SnSe) is prepared.

[0047] Example 4 Example 4 is substantially the same as Example 1, except that the amount of ammonium fluoride (NH4F) added in step (3) is different; wherein the amount of ammonium fluoride (NH4F) added in step (3) of Example 4 is 47.5 mg, and a fluorine-doped tin selenide powder (6wt% F-SnSe) is prepared.

[0048] Example 5 Example 5 is substantially the same as Example 1, except that the amount of ammonium fluoride (NH4F) added in step (3) is different; wherein the amount of ammonium fluoride (NH4F) added in step (3) of Example 5 is 65.0 mg, and a fluorine-doped tin selenide powder (8wt% F-SnSe) is prepared.

[0049] Example 6 Example 6 is substantially the same as Example 1, except that the amount of ammonium fluoride (NH4F) added in step (3) is different; wherein the amount of ammonium fluoride (NH4F) added in step (3) of Example 6 is 85.5 mg, and a fluorine-doped tin selenide powder (10wt% F-SnSe) is prepared.

[0050] Comparative Example 1 (1) Selenium powder (2 mmol) and sodium borohydride (NaBH4, 250 mg) were added into 30 mL of deionized water and magnetically stirred at room temperature until a clear solution was formed to obtain a selenium precursor solution; stannous chloride hydrate (SnCl2·2H2O) (2 mmol) was added into 30 mL of deionized water and prepared to obtain a stannous chloride dihydrate (SnCl2·2H2O) solution; the stannous chloride dihydrate solution was added to the selenium precursor solution and stirred vigorously at room temperature for at least 20 minutes to obtain a mixture A; (2) The mixture A was transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle and subjected to a hydrothermal reaction at 180 °C for 12 hours; after the reaction was completed, the resulting reaction product A was naturally cooled to room temperature and then washed with deionized water and ethanol and dried to obtain SnSe powder.

[0051] Performance Test In the following tests, the fluorine-doped tin selenide powder prepared in the examples and the tin selenide powder prepared in the comparative examples were subjected to performance tests after being used to construct gas-sensitive sensor elements by drop coating technology. The construction process was as follows: 20 milligrams of fluorine-doped tin selenide powder prepared in the examples and 30 microliters of anhydrous ethanol were placed in a 0.5 milliliter centrifuge tube, and a stable colloidal suspension was prepared by ultrasonic treatment for 10 minutes; then, the stable colloidal suspension was precisely deposited on an interdigital platinum electrode array by a microsyringe with an increment of 2.5 microliters each time, so as to uniformly cover the active sensing area and obtain a sensor.

[0052] In the following tests, the evaluation of gas-sensitive properties was carried out on an assembled gas flow control test device, which integrated dynamic atmosphere control and resistance value monitoring as two core functions; all standard target gases (purity 99.99%, supplier: Chongqing Juchanghao Gas Co., Ltd.) were diluted by humidified synthetic air (21% oxygen and 79% nitrogen mixed gas) to control humidity, wherein the gas concentration was performed by a high-precision mass flow controller from the United States Alicat Scientific, the total gas flow rate and humidity (in the range of 0% to 80%) were precisely controlled by FlowVision automation software, and the total gas flow rate was maintained at 500 milliliters per minute during the test.

[0053] All the following tests include three stages: the first step is to make the sensor reach a baseline stability in the humid air flow and record the initial resistance Ra; the second step is to introduce the target analyte gas to monitor the dynamic response of the adsorption process; the third step is to introduce the humid air again to start the desorption cycle; the response amplitude is quantified by the formula |Rg-Ra| / Ra, where Rg represents the resistance when the gas-sensitive reaction reaches the equilibrium state. The response time and recovery time are extracted from the resistance-time curve, and the determination standard is the time node required to reach 90% of the total signal change; the whole resistance data collection is completed by Keithley 2700 digital multimeter, and the resolution of the instrument is 0.1%.

[0054] (1) Response characteristics test of different gases The response of the sensor prepared from the fluorine-doped tin selenide powder prepared in Example 1 to different gases was tested according to the above test method, and the results are shown in Table 1. Figure 1 The results show that the response value of the fluorine-doped tin selenide powder prepared in Example 1 to 10 ppm NO at room temperature is as high as 227.62%. The material has high selectivity to NO and NO2 (response values are 244.5% and 207.45%, respectively), which is significantly better than the response to interfering gases such as H2S, NH3, VOCs, etc., overcoming the bottleneck of poor selectivity of traditional sensors.

[0055] (2) Response time test The response time of the sensor prepared from the fluorine-doped tin selenide powder prepared in Example 1 to NO was tested according to the above test method, and the results are shown in Table 2. Figure 2 The results show that the response time of the fluorine-doped tin selenide powder prepared in Example 1 to 10 ppm NO at room temperature is 105.9 seconds.

[0056] (3) Humidity resistance test The response time of the sensor prepared from the fluorine-doped tin selenide powder prepared in Example 1 to NO in different humidity environments was tested according to the above test method, and the results are shown in Table 3. Figure 3 The results show that the performance fluctuation of the fluorine-doped tin selenide powder prepared in Example 1 at room temperature in a high humidity environment (80% RH) is less than 15%, showing excellent humidity resistance.

[0057] (4) Detection limit test The response of the sensor prepared from the fluorine-doped tin selenide powder prepared in Example 1 to different concentrations of NO was tested according to the above test method, and the results are shown in Table 4. Figure 4 The results show that the fluorine-doped tin selenide powder prepared in Example 1 can still produce a response to 400 ppb NO at room temperature, indicating that the detection limit is as low as 400 ppb.

[0058] (5) Stability test The response of the sensor prepared from the fluorine-doped tin selenide powder prepared in Example 1 to 10 ppm NO was tested by the above-mentioned test method after the fluorine-doped tin selenide powder was placed for different time (room temperature, 40% humidity), and the results are shown in Table 1. Figure 5 As shown in Table 1, the results show that the response of the fluorine-doped tin selenide powder prepared in Example 1 to 10 ppm NO does not fluctuate greatly after being placed for 30 days, indicating good stability.

[0059] In addition, the NO selectivity, NO response time, humidity resistance, NO detection limit and stability of the fluorine-doped tin selenide powder prepared in Examples 2 to 5 and the SnSe powder prepared in Comparative Example 1 were tested by the above-mentioned method, and were compared with the fluorine-doped tin selenide powder prepared in Example 1, and the test results are shown in Table 1.

[0060] Table 1 Performance test results of the materials prepared in the examples and comparative examples

[0061] As can be seen from Table 1, the response performance and stability of the fluorine-doped tin selenide prepared in Examples 1 to 5 to NO are significantly better than that of the tin selenide without fluorine doping in Comparative Example 1; in addition, with the increase of the amount of F added, the response performance first increases and then decreases, and when the amount of F added is 4wt% (Example 1), the NO response value is higher, the NO response time is shorter, the NO detection limit is lower, and the stability is more excellent.

[0062] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present application, and they should all be covered in the scope of the claims of the present application.

Claims

1. Fluorine-doped tin selenide, which has a nanosheet structure, has the following characteristics: (i) It exhibits a laterally extended ultrathin nanosheet morphology with a thickness of 1 nm to 10 nm; (ii) Fluoride ions are inserted into the interlayer of tin selenide and cause lattice distortion, and at least some of the fluoride ions are adsorbed on the (001) crystal plane.

2. A method for preparing fluorine-doped tin selenide, the method including: (1) Disperse tin selenide in water to obtain a dispersion; (2) Fluorine-doped tin selenide is obtained by mixing the dispersion with ammonium fluoride and then carrying out a hydrothermal reaction.

3. The preparation method according to claim 2, characterized in that, The fluorine doping amount is 1 wt% to 10 wt% of the total mass of tin selenide and ammonium fluoride.

4. The preparation method according to claim 3, characterized in that, The fluorine doping amount is 4 wt% of the total mass of tin selenide and ammonium fluoride.

5. The preparation method according to any one of claims 2 to 4, characterized in that, (a) The hydrothermal reaction temperature is 160℃~200℃; and / or (b) The hydrothermal reaction time based on temperature (a) is ≥12h.

6. The preparation method according to any one of claims 2 to 4, characterized in that, Methods for preparing tin selenide include: (1) Selenium powder and sodium borohydride were mixed with water to obtain a selenium precursor solution; (2) Tin selenide is obtained by mixing the selenium precursor solution and the aqueous solution of stannous chloride dihydrate and then carrying out a hydrothermal reaction.

7. A gas sensor, characterized in that, Includes fluorine-doped tin selenide as described in claim 1 or fluorine-doped tin selenide prepared by the preparation method described in any one of claims 2 to 6.

8. The application of the fluorine-doped tin selenide according to claim 1, or the fluorine-doped tin selenide prepared by the preparation method according to any one of claims 2 to 6, or the gas sensor according to claim 7, in detecting or monitoring gases.

9. The application according to claim 8, characterized in that, The gas is nitric oxide and / or nitrogen dioxide.

10. The application according to claim 8 or 9, characterized in that, Applications include: detection or monitoring of gases in high humidity environments, where the humidity is ≥60% RH.

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