SnS2-based multi-element core-shell heterojunction as well as preparation method and application thereof

Abstract

The invention discloses a SnS2-based multi-element core-shell heterojunction and a preparation method and application thereof, and belongs to the technical field of material science and gas sensors, the SnO2 / WO3 nanorod heterojunction with uniform morphology is obtained by adopting Sn atom doping and adjusting the stirring temperature and the reaction time. The SnS2 nanosheet is used as a template, the SnO2 / WO3 nanorod and CS (NH2) 2 are used as raw materials, and the SnS2-based multi-element core-shell heterojunction is obtained through a vulcanization reaction. The SnS2-based multi-element core-shell heterojunction prepared by the preparation method disclosed by the invention not only comprises a p-n junction formed by p-type WS2 and n-type SnS2, but also comprises a metal / semiconductor heterojunction formed by 1T-WS2 and n-type SnS2, and a crystalline phase heterojunction formed between the 1T-WS2 and 2H-WS2. The sensitivity of the NO2 gas sensor is effectively enhanced through the synergistic effect of the three heterojunctions.

Description

Technical Field

[0001] The present invention relates to the field of material science and gas sensor technology, and in particular to a SnS2-based multi-element core-shell heterojunction and a preparation method and application thereof. Background Art

[0002] With the increasing severity of environmental pollution, NO2 gas concentration has become an important indicator of air quality. Highly sensitive, low-power, room-temperature-operating NO2 gas sensors hold great promise for application in environmental monitoring and air quality testing. However, existing NO2 gas sensors still face challenges such as low sensitivity, long response times, and high operating temperatures. Therefore, the development of novel gas sensing materials, particularly those with low detection limits and high sensitivity at room temperature, has become a research hotspot.

[0003] In recent years, two-dimensional materials have attracted considerable attention due to their large surface area, excellent electrical properties, and abundant gas-solid interaction sites. Among these 2D materials, transition metal dichalcogenides (TMDCs) have shown promising application prospects in gas sensing due to their low cost, good intrinsic activity, moderate band gap, and large surface area. Transition metal dichalcogenides, such as WS2 and SnS2, exhibit excellent gas adsorption properties, making them ideal room-temperature gas sensing materials. With increasing research, constructing van der Waals heterojunctions of 2D TMDCs with diverse properties and functions has become an important approach to improving material performance and promoting their applications. Unlike traditional heterojunction structures, van der Waals heterojunctions rely on van der Waals forces rather than chemical bonds and lattice matching, offering greater construction flexibility and enabling the realization of atomically precise heterojunction interfaces. Charge transfer and proximity effects across these interfaces can optimize the band structure and surface work function, promoting the adsorption and reaction of gas molecules on the material surface, thereby enhancing sensor sensitivity. However, van der Waals heterojunctions still suffer from weak interfacial interactions and limited charge transfer, which results in a large energy barrier and limits their application in high-sensitivity detection of trace gases. Summary of the Invention

[0004] In response to the above problems, the present invention provides a SnS2-based multi-element core-shell heterojunction and its preparation method and application, which effectively solves the technical problems of weak interfacial interaction and limited charge transfer in existing van der Waals heterojunction sensing materials, thereby affecting high-sensitivity detection of trace gases. The present invention uses SnS2 as a template to epitaxially grow crystalline heterojunctions of 1T phase WS2 and 2H phase WS2 with SnS2 to obtain a SnS2-based multi-element core-shell heterojunction. Through the synergistic effect of the low noise characteristics of the 1T phase and the high response characteristics of the 2H phase, the gas sensing performance is significantly improved, thereby achieving high-sensitivity detection of trace NO2 gas at room temperature.

[0005] The first object of the present invention is to provide a method for preparing a SnS2-based multi-element core-shell heterojunction, characterized in that it comprises the following steps: Preparation of SnS2 nanosheets.

[0006] Sn source and W source are used as raw materials to form a suspension in water, which is stirred at 70℃~80℃ and then subjected to hydrothermal reaction to obtain SnO2 / WO3 nanorods.

[0007] Using SnS2 nanosheets as templates, the SnO2 / WO3 nanorods and CS(NH2)2 as raw materials, water is added to form a suspension, and a sulfurization reaction is carried out at 180℃~220℃ for 26h~36h to generate p-type WS2 with 1T phase WS2 and 2H phase WS2. The p-type WS2 and SnS2 form a pn junction, the 1T phase WS2 and SnS2 form a metal / semiconductor heterojunction, and a crystalline heterojunction is formed between the 1T phase WS2 and the 2H phase WS2, thereby obtaining a SnS2-based multi-core-shell heterojunction.

[0008] As a preferred embodiment, the molar ratio of the Sn source to the W source is 1-1.2:0.8.

[0009] As a preferred embodiment, the mass ratio of the SnS2 nanosheets, SnO2 / WO3 nanorods and CS(NH2)2 is 5:1.5~3:95.

[0010] As a preferred embodiment, stirring is performed at 75°C, and then a hydrothermal reaction is performed at 200°C to 220°C.

[0011] As a preferred embodiment, the stirring time is 1.5h~2h, and the hydrothermal reaction time is 10h~14h.

[0012] As a preferred embodiment, polyvinyl pyrrolidone is added to the suspension, and the mass ratio of the SnS2 nanosheets to polyvinyl pyrrolidone is 1:10~12.

[0013] As a preferred embodiment, the Sn source is SnCl4·5H2O, and the W source is (NH4) 10 H2(W2O7)6.

[0014] As a preferred embodiment, the preparation method of the SnS2 nanosheets includes the following steps: preparing an aqueous suspension using CS(NH2)2 and SnCl4·5H2O as raw materials, and reacting the aqueous suspension at 100°C~120°C to obtain the obtained nanosheets.

[0015] The second object of the present invention is to provide a SnS2-based multi-element core-shell heterojunction prepared by any of the preparation methods described above.

[0016] The third object of the present invention is to provide an application of the above-mentioned SnS2-based multi-element core-shell heterojunction in NO2 gas detection.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a SnS2-based multi-element core-shell heterojunction. First, Sn atoms are doped, and by adjusting the stirring temperature and reaction time, a uniform SnO2 / WO3 nanorod-shaped heterojunction is obtained. Then, using SnS2 nanosheets as templates, SnO2 / WO3 nanorods and CS(NH2)2 as raw materials, a sulfurization reaction is performed to obtain a SnS2-based multi-element core-shell heterojunction formed by WS2 containing 1T and 2H phases and SnS2. The SnS2-based multi-element core-shell heterojunction prepared by the present invention includes a pn junction formed by p-type WS2 and n-type SnS2, a metal / semiconductor heterojunction formed by 1T phase WS2 and n-type SnS2, and a crystalline phase heterojunction formed between 1T phase WS2 and 2H phase WS2. The synergistic effect of these three heterojunctions effectively enhances the sensitivity of NO2 gas sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 These are the SEM images and XRD patterns of SnO2 / WO3 nanorods synthesized at different stirring temperatures in the examples of the present invention, wherein a) is Example 1 at 70°C, b) is Example 2 at 75°C, c) is Example 3 at 80°C, and d) is the XRD pattern.

[0019] Figure 2 These are the SEM images, XRD images and EDX images of SnO2 / WO3 nanorods synthesized at different hydrothermal reaction times according to the embodiments of the present invention, wherein a) is Example 4 (10h), b) is Example 5 (14h), c) is the XRD image, and d) is the EDX image of Example 2.

[0020] Figure 3 SEM images and XRD patterns of SnS2 nanosheets prepared in the present invention, a) is the SEM image, b) is the XRD pattern.

[0021] Figure 4 The SEM images of SnS2-based multi-element core-shell heterojunctions synthesized at different sulfurization reaction times according to the embodiments of the present invention, wherein a) is for comparative example 1 (24h), b) is for example 2 (26h), c) is for example 6 (30h), d) is for example 7 (36h), and e) is for comparative example 2 (40h). Figure 4 The scale bars in Figures a) to e) are all 2 μm.

[0022] Figure 5The XRD patterns of SnS2-based multi-element core-shell heterojunctions synthesized at different sulfurization reaction times according to the embodiments of the present invention.

[0023] Figure 6 These are the planar and side EDX images of the SnS2-based multi-element core-shell heterojunction synthesized under sulfurization reaction for 26 h in Example 1 of the present invention, where a) is the planar view and b) is the side view.

[0024] Figure 7 This is the XPS graph of the SnS2-based multi-element core-shell heterojunction synthesized in Example 1 of the present invention under a sulfurization reaction for 26 h, wherein Figure A is S 2p, Figure B is Sn 3d, and Figure C is E 4f.

[0025] Figure 8 The IV curves of the SnS2 nanosheets prepared in the present invention and the SnS2-based multi-core-shell heterojunction synthesized under different sulfurization reaction times.

[0026] Figure 9 The response-recovery curves of the SnS2 nanosheets prepared in the present invention and the SnS2-based multi-core-shell heterojunction synthesized at different sulfurization reaction times to 5ppm NO2. DETAILED DESCRIPTION

[0027] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0028] In response to the technical problem that existing van der Waals heterojunctions have weak interfacial interactions and limited charge transfer, resulting in a large energy barrier, which limits the application of van der Waals heterojunctions in high-sensitivity detection of trace gases, the present invention provides a SnS2-based multi-element core-shell heterojunction and its preparation method and application.

[0029] The technical solution of the present invention is described in detail below.

[0030] The present invention first provides a method for preparing a SnS2-based multi-element core-shell heterojunction, comprising the following steps: S1. Preparation of SnS2 nanosheets: using CS(NH2)2 and SnCl4·5H2O as raw materials to prepare an aqueous suspension, and reacting the aqueous suspension at 100°C~120°C for 12 h to obtain the obtained nanosheets.

[0031] S2, (NH4) 10H2(W2O7)6 and SnCl4·5H2O are used as raw materials, water is added, stirred at 70℃~80℃, and then a hydrothermal reaction is carried out to obtain SnO2 / WO3 nanorods.

[0032] S3, using SnS2 nanosheets as templates, the SnO2 / WO3 nanorods, CS(NH2)2 and PVP as raw materials, adding water to form a suspension, and performing a sulfurization reaction at 180℃~220℃ to generate p-type WS2 with 1T phase WS2 and 2H phase WS2, the p-type WS2 and SnS2 form a pn junction, the 1T phase WS2 and SnS2 form a metal / semiconductor heterojunction, and the crystalline phase heterojunction formed between the 1T phase WS2 and the 2H phase WS2 obtains a SnS2-based multi-core-shell heterojunction.

[0033] In the above-mentioned technical solution, Sn atoms are first doped to obtain a SnO2 / WO3 nanorod-shaped heterojunction. Then, using SnS2 nanosheets as a template, SnO2 / WO3 nanorods and CS(NH2)2 as raw materials, a sulfurization reaction is performed to obtain a SnS2-based multi-element core-shell heterojunction formed by WS2 containing 1T phase and 2H phase and SnS2. The SnS2-based multi-element core-shell heterojunction prepared by the present invention includes both a pn junction composed of p-type WS2 and n-type SnS2, a metal / semiconductor heterojunction formed by 1T phase WS2 and n-type SnS2, and a crystalline phase heterojunction formed between 1T phase WS2 and 2H phase WS2. The synergistic effect of the above three heterojunctions effectively enhances the sensitivity of the NO2 gas sensor.

[0034] In the present invention, when preparing SnO2 / WO3 nanorods, the morphology of SnO2 / WO3 is affected by changing the time of the hydrothermal reaction, and the irregular morphology is not conducive to the attachment of the transition product SnO2 / WO3 nanorods to the SnS2 nanosheets. In order to prepare SnO2 / WO3 nanorods with uniform morphology, the present invention performs a hydrothermal reaction at 200℃~220℃ for 10h~14h. When the reaction temperature is too low or the reaction time is too short, the crystal crystallinity will decrease. When the reaction temperature is too high or the reaction time is too long, the crystal will collapse and then agglomerate again. These will change the crystal morphology, which is not conducive to the second step of compounding.

[0035] The duration of the sulfurization reaction in the present invention is also an important factor affecting the uniformity of crystal growth. The present invention adjusts the sulfurization duration from 26 h to 24 h, 30 h, 36 h, and 40 h, respectively. It is found that the sulfurization duration has a significant effect on the morphology uniformity, thereby affecting the performance of the SnS2-based multi-element core-shell heterojunction. In order to further optimize the performance of the heterojunction, the time of the sulfurization reaction is 26 h to 36 h. The sulfurization duration is also an important factor affecting the uniformity of crystal growth. The present invention adjusts the sulfurization duration from 26 h to 24 h, 30 h, 36 h, and 40 h, respectively. It is found that the sulfurization duration has a significant effect on the morphology uniformity, thereby affecting the performance of the heterojunction.

[0036] In order to prepare a uniform SnO2 / WO3 nanorod heterojunction, the molar ratio of the Sn source to the W source is 1-1.2:0.8. The Sn source used in the present invention is SnCl4·5H2O, and the W source is (NH4) 10 H2(W2O7)6.

[0037] In order to prepare WS2 with 1T phase and 2H phase, the mass ratio of SnS2 nanosheets, SnO2 / WO3 nanorods and CS(NH2)2 is 5:1.5~3:95.

[0038] It should be noted that the Sn source and W source form a suspension in water, are stirred at 70°C to 80°C for 1.5h to 2h, and then undergo a hydrothermal reaction at 200°C to 220°C. The present invention uses SnS2 nanosheets as a template, and through research it is found that the formation of the 1T phase is related to the reaction time. In the process of exploring the preparation of SnS2-based multi-element core-shell heterojunctions, the change in stirring temperature has an important influence on the adhesion of SnO2 on WO3. When the stirring temperature is adjusted from 75°C to 70°C or 80°C, the stability of the crystal structure can be better controlled. Increased temperature enhances the thermal motion of molecules, thereby weakening the interaction force between atoms, laying the foundation for the subsequent crystal growth of Sn-doped metal sulfide Sn-WS2. If the temperature is too high, the crystal structure will lose stability and lead to destruction.

[0039] It should be noted that the preparation method of the SnS2 nanosheets includes the following steps: preparing an aqueous suspension using CS(NH2)2 and SnCl4·5H2O as raw materials, and reacting the aqueous suspension at 100°C~120°C to obtain the obtained nanosheets.

[0040] In order to prepare a suspension with stable properties, thereby further improving the morphology uniformity of the SnO2 / WO3 nanorod-shaped heterojunction, polyvinyl pyrrolidone is added to the suspension, and the mass ratio of the SnS2 nanosheets to polyvinyl pyrrolidone is 1:10~12.

[0041] The present invention will be described in detail below through the following examples and comparative examples.

[0042] Example 1 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0043] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a molar ratio of 1:0.8 and stirred at 70°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes, washed three times with deionized water, and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0044] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 26 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0045] Example 2 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0046] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a molar ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes, washed three times with deionized water, and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0047] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 26 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0048] Example 3 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0049] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 80°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0050] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 26 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0051] Example 4 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0052] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 10 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0053] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 26 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0054] Example 5 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0055] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 14 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0056] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 26 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0057] Example 6 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0058] S2, SnCl4·5H2O and (NH4) 10H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0059] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 30 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0060] Example 7 A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0061] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0062] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 36 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0063] In order to further illustrate the effect of the present invention, the present invention also provides a comparative example, as follows: Comparative Example 1 Compared with Example 2, the difference is that the sulfurization reaction time is adjusted from 26 hours to 24 hours.

[0064] A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0065] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0066] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 24 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0067] Comparative Example 2 Compared with Example 2, the difference is that the sulfurization reaction time is adjusted from 26 hours to 40 hours.

[0068] A method for preparing a SnS2-based multi-element core-shell heterojunction comprises the following steps: S1. Preparation of SnS2 nanosheets: Dissolve CS(NH2)2 and SnCl4·5H2O in 19 mL of deionized water at a mass ratio of 15:1. Stir for 2 hours to form a homogeneous suspension. The suspension is then transferred to a reactor and the reaction temperature is set at 180°C for 12 hours. After completion of the reaction, centrifuge at 6500 rpm for 6 minutes, repeated three times. The sample is then rinsed three times with deionized water and dried at 80°C for 6 hours to obtain SnS2 nanosheets.

[0069] S2, SnCl4·5H2O and (NH4) 10 H2(W2O7)6 was dissolved in 20 mL of deionized water at a ratio of 1:0.8 and stirred at 75°C for 2 hours to produce a suspension. The suspension was then transferred to a reactor, set at 220°C for 12 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with deionized water and dried at 80°C for 6 hours to obtain SnO2 / WO3 nanorods.

[0070] S3: 6 mg of SnS2 nanosheets, 2.4 mg of SnO2 / WO3 nanorods, and 114 mg of CS(NH2)2 were mixed, and 66 mg of PVP was added and dissolved in 20 mL of deionized water to form a suspension. The suspension was then transferred to a reactor, and the reaction temperature was set at 220°C for 40 hours. After the reaction, the product was centrifuged three times at 6500 rpm for 6 minutes. The sample was washed three times with ethanol and dried at 80°C for 6 hours to obtain a SnS2-based multi-element core-shell heterojunction.

[0071] The morphology and performance of the SnS2-based multi-element core-shell heterojunctions prepared in Examples 1 to 7 above were tested, and the results are as follows.

[0072] Figure 1 The SEM images and XRD patterns of SnO2 / WO3 nanorods synthesized at different stirring temperatures in the present invention are shown in Figure 1 (a) for Example 1 at 70°C, Figure 2 (b) for Example 2 at 75°C, Figure 3 (c) for Example 3 at 80°C, and Figure d) for the XRD pattern. Figure 1 It can be seen that the stirring temperature affects the growth of the crystal nucleus. SnO2 / WO3 nanorods can be synthesized under the reaction conditions of 70~80℃, and the SnO2 / WO3 nanorods obtained under 75℃ have better morphology uniformity.

[0073] Figure 2 The SEM images, XRD images and EDX images of SnO2 / WO3 nanorods synthesized at different hydrothermal reaction times in the present invention are shown in Figure 1, where a) is Example 4 (10h), b) is Example 5 (14h), c) is the XRD image, and d) is the EDX image of Example 2. Figure 2 It can be seen that a shorter reaction time will result in poor crystallinity, and a longer reaction time will cause crystal agglomeration. Uniform nanorods are generated when the reaction time is 12 h.

[0074] Figure 3 The SEM and XRD patterns of the SnS2 nanosheets prepared in the present invention are shown in Figure a) as the SEM pattern and Figure b) as the XRD pattern. Figure 3 It can be seen that SnS2 nanosheets were successfully synthesized and the morphology was uniformly distributed.

[0075] Figure 4 The SEM images and XRD images of SnS2-based multi-element core-shell heterojunctions synthesized in different sulfurization reaction times according to the present invention are shown in Figure a) for comparative example 1 (24h), b) for example 2 (26h), c) for example 6 (30h), d) for example 7 (36h), and e) for comparative example 2 (40h). Figure 4 It can be seen that the morphology of the SnS2-based multi-element core-shell heterojunction generated at 26 h is more regular.

[0076] Figure 5 The XRD patterns of SnS2-based multi-element core-shell heterojunctions synthesized at different sulfurization reaction times according to the embodiments of the present invention. Figure 6 The plane and side EDX images of the SnS2-based multi-element core-shell heterojunction synthesized in Example 1 of the present invention under 26 h of sulfurization reaction, wherein a) is the plane and b) is the side. Figure 5 and Figure 6 It can be seen that the present invention successfully synthesized the SnS2-based multi-element core-shell heterojunction.

[0077] Figure 7 This is the XPS graph of the SnS2-based multi-element core-shell heterojunction synthesized in Example 1 of the present invention under 26 h of sulfurization reaction. Figure 7 It can be seen that the SnS2-based multi-core-shell heterostructure containing 1T phase WS2 was successfully synthesized.

[0078] Figure 8 The IV curves of SnS2 nanosheets prepared by the present invention and SnS2-based multi-element core-shell heterojunctions synthesized under different sulfurization reaction times are shown. Figure 8 It can be seen that the SnS2-based multi-element core-shell heterojunction with a temperature of 26 h has the best photoelectric effect and the strongest conductivity.

[0079] Figure 9 The response-recovery curves of SnS2 nanosheets prepared by the present invention and SnS2-based multi-element core-shell heterojunctions synthesized at different sulfurization reaction times to 5ppm NO2 are shown. Figure 9 It can be seen that the SnS2-based multi-core-shell heterojunction formed with a reaction time of 26h has the highest response-recovery value to 5ppm NO2, which is mainly due to the large specific surface area brought by the regular morphology.

[0080] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. A method for preparing a SnS2-based multi-element core-shell heterojunction, characterized in that: The following steps are involved: Preparation of SnS2 nanosheets; Sn source and W source are used as raw materials to form a suspension in water, which is stirred at 70℃~80℃ and then subjected to hydrothermal reaction to obtain SnO2 / WO3 nanorods; Using SnS2 nanosheets as templates, the SnO2 / WO3 nanorods and CS(NH2)2 as raw materials, water is added to form a suspension, and a sulfurization reaction is carried out at 180℃~220℃ for 26h~36h to generate p-type WS2 with 1T phase WS2 and 2H phase WS2. The p-type WS2 and SnS2 form a pn junction, the 1T phase WS2 and SnS2 form a metal / semiconductor heterojunction, and a crystalline heterojunction is formed between the 1T phase WS2 and the 2H phase WS2, thereby obtaining a SnS2-based multi-core-shell heterojunction.

2. The preparation method according to claim 1, characterized in that The molar ratio of the Sn source to the W source is 1-1.2:0.

8.

3. The preparation method according to claim 1, characterized in that The mass ratio of the SnS2 nanosheets, SnO2 / WO3 nanorods and CS(NH2)2 is 5:1.5~3:

95.

4. The preparation method according to claim 1, characterized in that Stir at 75°C, and then carry out hydrothermal reaction at 200°C~220°C.

5. The preparation method according to claim 1, characterized in that The stirring time is 1.5 h to 2 h, and the hydrothermal reaction time is 10 h to 14 h.

6. The preparation method according to claim 1, characterized in that Polyvinyl pyrrolidone is added to the suspension, and the mass ratio of the SnS2 nanosheets to the polyvinyl pyrrolidone is 1:10-12.

7. The preparation method according to claim 1, characterized in that The Sn source is SnCl4·5H2O, and the W source is (NH4) 10 H2(W2O7)6.

8. The preparation method according to claim 1, characterized in that The preparation method of the SnS2 nanosheets comprises the following steps: preparing an aqueous suspension using CS(NH2)2 and SnCl4·5H2O as raw materials, and reacting the aqueous suspension at 100°C to 120°C to obtain the nanosheets.

9. A SnS2-based multi-element core-shell heterojunction, characterized in that The method is prepared according to any one of claims 1 to 8.

10. Use of the SnS2-based multi-element core-shell heterojunction according to claim 9 in NO2 gas detection.

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