Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction as well as preparation method and application thereof
By constructing a Bi2WO6/ZnIn2S4/Ag ternary hierarchical heterojunction, the problems of high operating temperature and poor selectivity of Bi2WO6 material in VOCs detection were solved, achieving high response value and rapid recovery to triethylamine at low temperature, with excellent selectivity and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGXI NORMAL UNIV
- Filing Date
- 2025-12-22
- Publication Date
- 2026-05-08
AI Technical Summary
Existing Bi2WO6 materials have high operating temperatures and poor selectivity in the detection of volatile organic compounds (VOCs), and it is difficult to form a robust heterostructure interface, which limits the improvement of gas-sensing performance.
A Bi2WO6/ZnIn2S4/Ag ternary hierarchical heterojunction was constructed by embedding ZnIn2S4 nanosheets on the surface of Bi2WO6 nanoplates and dispersing Ag nanoparticles on them, forming stable semiconductor heterojunctions and semiconductor-metal heterojunctions, thereby achieving multi-interface charge transfer.
It exhibits high response value, fast response/recovery speed and excellent selectivity to triethylamine at lower operating temperatures, and has good long-term stability, thus improving gas sensing performance.
Smart Images
Figure CN121990609A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the fields of new materials and electronic information technology, specifically relating to a Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction, its preparation method and application. Background Technology
[0002] Resistive gas sensors based on semiconductor gas-sensitive materials are among the most common and widely used gas sensors, and they hold great promise for detecting volatile organic compounds (VOCs). However, their gas-sensing performance still lags far behind theoretical values and practical requirements. Developing highly efficient VOCs gas sensing materials has become a research hotspot in recent years.
[0003] Gas sensors are widely used in various industrial and daily life fields such as chemical, metallurgical, environmental protection, medical, and food industries. Developing novel and efficient sensing materials is a current research focus in the field of gas sensors. Metal-oxide-semiconductor (MOS) sensors show great promise for identifying various gases due to their low cost, ease of operation, and portability. Many MOS sensors, including ZnO, In2O3, SnO2, Co3O4, CuO, and TiO2, are used for monitoring VOCs. Currently, Bi2WO6 has been successfully used as a sensor material due to its excellent electron transport efficiency, crystal structure stability, and environmental compatibility. Although there is a large body of literature on Bi2WO6 sensing materials, pure Bi2WO6 still exhibits a high operating temperature and poor VOCs selectivity, meaning that the gas detection performance of pure Bi2WO6 needs further enhancement and optimization.
[0004] Constructing heterostructures (including semiconductor heterostructures, semiconductor / metal heterostructures, etc.) is an important strategy for improving the gas-sensing performance of semiconductor gas-sensitive materials. In practice, due to lattice or band structure mismatches, it is often difficult to form robust and compact heterostructure interfaces between semiconductor elements or between semiconductors and metals. This makes effective charge transfer between components difficult, resulting in the inability to effectively convert the charge signal of the gas-solid reaction into a resistance signal, which significantly hinders further improvements in gas-sensing performance. In particular, designing robust and compact multi-interface ternary heterostructures remains a significant challenge compared to common binary semiconductor or semiconductor / metal heterostructures. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction, its preparation method, and its application. Specifically, the following technical solution is adopted: In a first aspect, the present invention provides a Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction. The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction includes a substrate Bi2WO6 nanoplate, ZnIn2S4 nanosheets densely embedded on the surface of the Bi2WO6 nanoplate, and Ag nanoparticles uniformly dispersed on the ZnIn2S4 nanosheets. The Bi2WO6 nanoplate and the ZnIn2S4 nanosheet form a semiconductor heterostructure interface; the Ag nanoparticles form a semiconductor-metal heterostructure interface on the surface of the ZnIn2S4 nanosheet.
[0006] This invention provides a Bi₂WO₆ / ZnIn₂S₄ / Ag ternary hierarchical heterojunction gas sensor. The sensor consists of a Bi₂WO₆ nanoplate as a substrate, ZnIn₂S₄ nanosheets embedded on the surface of the Bi₂WO₆ nanoplate, and a highly dispersed Ag nanoparticle outermost layer. It provides excellent sensing performance for the detection of the volatile organic compound triethylamine, exhibiting an R0.05 of approximately 128.94 for 100 ppm triethylamine at a relatively low operating temperature of 275 °C. a / R g It exhibits a significant response, along with excellent response / recovery speed and selectivity, and durable stability (over 60 days).
[0007] Most importantly, robust semiconductor heterojunctions (Bi₂WO₆ / ZnIn₂S₄) and semiconductor-metal heterojunctions (ZnIn₂S₄ / Ag) are formed in the ternary heterostructure, achieving highly efficient multi-interface charge transfer characteristics. Furthermore, due to the 2D / 2D / 0D structure design, the Bi₂WO₆ / ZnIn₂S₄ / Ag ternary hierarchical heterojunction not only possesses a large specific surface area for gas adsorption and reaction but also improves the stability of Bi₂WO₆. This invention, through the comprehensive design of a multi-interface ternary heterostructure, provides a new perspective for improving the gas-sensing properties of semiconductor materials.
[0008] As a further preferred embodiment, the longitudinal dimension of the Bi2WO6 nanoplate is 2 μm to 10 μm, the thickness of the ZnIn2S4 nanosheet is 10 nm to 50 nm, and the size of the Ag nanoparticles is 1 nm to 20 nm.
[0009] As a further preferred embodiment, the loading of the Ag nanoparticles is 1 wt% to 3 wt%; The specific surface area of the Bi2WO6 / ZnIn2S4 / Ag is 20 m². 2 / g~40 m 2 / g.
[0010] Secondly, the present invention provides a method for preparing the above-mentioned Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction, comprising the following steps: Zinc chloride, indium chloride, and thioacetamide were dissolved in water, and the pH was adjusted to 1-3. Bi2WO6 nanoplates were added and reacted in a water bath. After the reaction was completed, the mixture was washed and dried to obtain a Bi2WO6 / ZnIn2S4 heterojunction. The silver nitrate solution was dissolved in water and mixed evenly with the Bi2WO6 / ZnIn2S4 heterojunction. Then, a photodeposition reaction was carried out. After the reaction was completed, the mixture was washed and dried to obtain the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0011] As a further preferred embodiment, the Bi2WO6 nanoplatelet is prepared by the following steps: Bismuth oxide, tungsten oxide and sodium chloride were mixed and then ground with ethanol. After grinding, the mixture was dried and annealed. After annealing, the mixture was washed and dried to obtain the Bi2WO6 nanoplate.
[0012] As a further preferred embodiment, the molar ratio of bismuth oxide, tungsten oxide and sodium chloride is 1:1-3:5; The annealing temperature is 600 ℃~700 ℃, and the annealing time is 3 h~5 h.
[0013] As a further preferred embodiment, the molar ratio of zinc chloride, indium chloride and thioacetamide is 1:1~3:1~4; The water bath reaction temperature is 60 ℃~100 ℃, and the water bath reaction time is 1 h~3 h.
[0014] As a further preferred embodiment, the concentration of silver nitrate is 0.01 g / mol to 0.04 g / mol; The Bi2WO 6 / The ratio of ZnIn2S4 heterojunction to silver nitrate is 50 mg~200 mg: 0.1 mL~0.5 mL; The power of the mercury lamp used in the photodeposition reaction is 600 W to 1200 W, and the irradiation time is 0.3 h to 1.0 h.
[0015] Thirdly, the present invention also provides a gas sensor comprising the aforementioned Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0016] Fourthly, the present invention provides the application of the above-mentioned Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction or the above-mentioned gas sensor in the detection of triethylamine gas.
[0017] The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction of the present invention is used as a gas-sensitive sensing layer in a gas sensor for gas adsorption and gas-sensitive reaction on the surface, and it has high selectivity for triethylamine detection.
[0018] The beneficial effects of this invention are as follows: (1) The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction of the present invention consists of an ultrathin ZnIn2S4 nanosheet wrapped around a Bi2WO6 nanoplate as a substrate, and highly dispersed Ag nanoparticles on the outermost layer. The Bi2WO6 nanoplate is used as the substrate because it has excellent electron transport efficiency, crystal structure stability, and environmental compatibility. The present invention successfully grows ZnIn2S4 nanosheets on the surface of a Bi2WO6 nanoplate to construct a Bi2WO6 / ZnIn2S4 heterojunction. At the same time, the present invention disperses noble metals on the surface of ZnIn2S4 nanosheets. The chemical sensitization effect of the noble metal nanoparticles not only greatly enhances the adsorption activity of the Bi2WO6 / ZnIn2S4 heterojunction for molecules, but also ZnIn2S4 itself has a large specific surface area, and the heterojunction formed with Ag nanoparticles can provide abundant surface active sites. Therefore, compared with heterojunctions in the prior art, the structure of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction prepared in this invention is that Ag nanoparticles form a semiconductor-metal heterojunction interface (ZnIn2S4 / Ag) on the surface of the Bi2WO6 / ZnIn2S4 heterojunction. The establishment of this interface ultimately achieves highly efficient multi-interface charge transfer characteristics. Under relatively low operating temperature conditions, the ternary hierarchical heterojunction exhibits excellent gas selectivity for triethylamine with high response value and fast recovery speed. This invention demonstrates excellent performance in terms of gas selectivity and long-term stability, and has broad application prospects in practical production.
[0019] (2) The preparation process of this invention is simple and low-cost. The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction prepared by this invention has good heterojunction interface contact and achieves efficient multi-interface charge transfer characteristics. The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction designed with 2D / 2D / 0D structure has a large gas adsorption and reaction specific surface area. In addition, the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction can be applied in gas sensors, specifically for the high-selectivity detection of triethylamine at a relatively low operating temperature of 275 °C. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 The XRD patterns of Bi2WO6, ZnIn2S4, Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag are shown. Figure 2 The diagram shows the fabrication process of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction (a); SEM images of pure Bi2WO6 (b, f); SEM images of the Bi2WO6 / ZnIn2S4 heterojunction (d, h); SEM images of ZnIn2S4 (e, i); (c, g) and (j)-(t) are SEM images, TEM images, HRTEM images and EDS elemental distribution images of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction, respectively.
[0022] Figure 3 The XPS spectra of Bi2WO6, ZnIn2S4, Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag are shown; where (a) is the Zn 2p XPS spectrum; (b) is the In 3d XPS spectrum; (c) is the S 2p & Bi 4f XPS spectrum; (d) is the W 4f XPS spectrum; (e) is the O 1s XPS spectrum; and (f) is the Ag 3d XPS spectrum.
[0023] Figure 4 The table shows the nitrogen adsorption-desorption isotherms and pore size distribution curves of different samples, as well as the specific surface area, pore volume and average pore size parameters of different samples; where (a) is Bi2WO6; (b) is ZnIn2S4; (c) is Bi2WO6 / ZnIn2S4; and (d) is Bi2WO6 / ZnIn2S4 / Ag.
[0024] Figure 5 The figures show the response curves of Bi2WO6, ZnIn2S4, Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag to triethylamine at a concentration of 100 ppm at different temperatures; where (a) represents Bi2WO6, ZnIn2S4, Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag; and (b) represents Bi2WO6 and ZnIn2S4.
[0025] Figure 6The results show the repeatability of different samples for 100 ppm triethylamine over several cycles at 275 °C; where (a) is Bi2WO6; (b) is ZnIn2S4; (c) is Bi2WO6 / ZnIn2S4; and (d) is Bi2WO6 / ZnIn2S4 / Ag.
[0026] Figure 7 The results show the dynamic sensing characteristics of different samples for different concentrations of triethylamine at 275 °C; where (a) is Bi2WO6; (b) is ZnIn2S4; (c) is Bi2WO6 / ZnIn2S4; and (d) is Bi2WO6 / ZnIn2S4 / Ag.
[0027] Figure 8 (a) shows the response curves of four samples with triethylamine concentrations in the range of 20-1000 ppm; (b) shows the detection limit of the triethylamine gas-sensitive reaction of Bi2WO6 / ZnIn2S4 / Ag; (c) shows the response-recovery time curve of Bi2WO6 / ZnIn2S4 / Ag to 100 ppm triethylamine; and (d) shows the response of Bi2WO6 / ZnIn2S4 / Ag to different types of volatile organic compound gases.
[0028] Figure 9 The figure shown is a graph illustrating the long-term stability of the Bi2WO6 / ZnIn2S4 / Ag response value over 60 days. Detailed Implementation
[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0030] This invention provides a process for preparing a Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction (see schematic diagram). Figure 2 (As shown in a) First, Bi2WO6 nanoplates were prepared using a solid-state reaction. Using the Bi2WO6 nanoplates as a substrate, ZnIn2S4 nanosheets were densely embedded on the surface of the Bi2WO6 nanoplates via a water bath method, thus obtaining a Bi2WO6 / ZnIn2S4 heterojunction. Finally, Ag nanoparticles were uniformly deposited via photochemical reduction to obtain a Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0031] Example 1 The specific preparation process of a Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction is as follows: (1) Bismuth oxide (Bi2O3), tungsten oxide (WO3) and sodium chloride were added to a mortar in a molar ratio of 1:1:5. Ethanol was added and the mixture was ground thoroughly and then dried. The resulting powder was transferred to an alumina crucible and placed in a muffle furnace for annealing. The annealing temperature and annealing time were set to 650 °C and 3 h, respectively. The annealed powder was washed with deionized warm water (6 times) and dried at 80 °C to obtain Bi2WO6 nanoplates.
[0032] (2) Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:1:2, mixed, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 1 mol / L nitric acid. Then, Bi2WO6 nanoplates (0.04233 g) were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 80 °C in a water bath for 2 hours. After the reaction was completed, the product was washed and dried to obtain Bi2WO6 / ZnIn2S4 heterojunctions.
[0033] (3) 0.222 mL of silver nitrate solution (0.02 g / mol) and Bi2WO6 / ZnIn2S4 heterojunction (100 mg) were poured into 40 mL of deionized water and mixed to obtain a mixed solution. The mixed solution was subjected to photodeposition reaction. The power of the mercury lamp was set to 1000 W to irradiate the mixed solution. The reaction time was 30 minutes. After the reaction was completed, the product was washed and dried to obtain Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0034] Example 2 A Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction is prepared by the following steps: Step 1: Bismuth oxide (Bi2O3), tungsten oxide (WO3), and sodium chloride were added to a mortar in a molar ratio of 1:2:5. Ethanol was added, and the mixture was ground thoroughly and then dried. The resulting powder was transferred to an alumina crucible and placed in a muffle furnace for annealing. The annealing temperature and annealing time were set to 650 °C and 3 h, respectively. The annealed powder was washed with deionized warm water (6 times) and then dried at 80 °C to obtain Bi2WO6 nanoplates.
[0035] Step 2: Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:2:2, mixed thoroughly, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 1 mol / L nitric acid. Then, 0.04233 g of Bi2WO6 nanoplates were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 80 °C in a water bath for 2 hours. After the reaction, the product was washed and dried to obtain a Bi2WO6 / ZnIn2S4 heterojunction.
[0036] Step 3: Pour 0.3 mL of silver nitrate solution (0.02 g / mol) and Bi2WO6 / ZnIn2S4 heterojunction (100 mg) into 50 mL of deionized water, mix well to obtain a mixed solution; and carry out photodeposition reaction in the mixed solution. Set the power of the mercury lamp to 1000 W to irradiate the mixed solution, and the reaction time is 30 minutes. After the reaction is completed, wash and dry the product to obtain Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0037] Example 3 A Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction is prepared by the following steps: Step 1: Bismuth oxide (Bi2O3), tungsten oxide (WO3), and sodium chloride were added to a mortar in a molar ratio of 1:3:5. Ethanol was added, and the mixture was ground thoroughly and then dried. The resulting powder was transferred to an alumina crucible and placed in a muffle furnace for annealing. The annealing temperature and annealing time were set to 650 °C and 3 h, respectively. The annealed powder was washed with deionized warm water (6 times) and then dried at 80 °C to obtain Bi2WO6 nanoplates.
[0038] Step 2: Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:2:3, mixed thoroughly, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 1 mol / L nitric acid. Then, 0.04233 g of Bi2WO6 nanoplates were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 80 °C in a water bath for 2 hours. After the reaction, the product was washed and dried to obtain a Bi2WO6 / ZnIn2S4 heterojunction.
[0039] Step 3: Pour 0.4 mL of silver nitrate solution (0.02 g / mol) and Bi2WO6 / ZnIn2S4 heterojunction (100 mg) into 40 mL of deionized water, mix well to obtain a mixed solution; and carry out photodeposition reaction in the mixed solution. Set the power of the mercury lamp to 1000 W to irradiate the mixed solution, and the reaction time is 30 minutes. After the reaction is completed, wash and dry the product to obtain Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0040] Comparative Example 1 Bi2WO6 nanoplates were prepared using the following method: Bismuth oxide (Bi2O3), tungsten oxide (WO3), and sodium chloride were added to a mortar in a molar ratio of 1:1:5, ethanol was added, and the mixture was ground thoroughly and then dried. The resulting powder was transferred to an alumina crucible and annealed in a muffle furnace. The annealing temperature and annealing time were set to 650 °C and 3 h, respectively. The annealed powder was washed with deionized warm water (6 times) and then dried at 80 °C to obtain Bi2WO6 nanoplates.
[0041] Comparative Example 2 ZnIn2S4 powder was prepared using the following method: Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:1:2, mixed thoroughly, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 1 mol / L nitric acid. This reaction solution was then subjected to a water bath reaction, with the temperature maintained at 80 °C for 2 hours. After the reaction, the product was washed and dried to obtain ZnIn2S4 powder.
[0042] Comparative Example 3 Only Bi2WO6 / ZnIn2S4 heterojunctions were prepared, and the preparation method is as follows: Bismuth oxide (Bi2O3), tungsten oxide (WO3), and sodium chloride were added to a mortar in a molar ratio of 1:1:5, ethanol was added, and the mixture was ground thoroughly and then dried. The resulting powder was transferred to an alumina crucible and annealed in a muffle furnace. The annealing temperature and annealing time were set to 650 °C and 3 h, respectively. The annealed powder was washed with deionized warm water (6 times) and then dried at 80 °C to obtain Bi2WO6 nanoplates.
[0043] Zinc chloride, indium chloride, and thioacetamide were dissolved in deionized water at a molar ratio of 1:1:2, mixed thoroughly, and stirred for 0.5 hours to obtain a reaction solution. The pH of the solution was adjusted to 2.5 with 1 mol / L nitric acid. Then, 0.04233 g of Bi₂WO₆ nanoplates were immersed in the reaction solution for a water bath reaction. The temperature of the reaction solution was maintained at 80 °C in a water bath for 2 hours. After the reaction, the product was washed and dried to obtain a Bi₂WO₆ / ZnIn₂S₄ heterojunction.
[0044] Example 4 The specific results of characterization and performance testing of the sensors prepared in Example 1 and Comparative Examples 1-3 are as follows: The crystal structure of the sample was studied using XRD. Figure 1It can be seen that for pure Bi₂WO₆ nanoplates, the crystal planes at 2θ = 28.54°, 32.91°, 36.01°, 47.25°, 56.04°, 58.68°, 69.04°, 76.12°, 78.56°, and 87.72° all match the crystal planes of the orthorhombic Bi₂WO₆ system (JCPDS 39-0256), with the (131) crystal plane being the most exposed. Similarly, pure ZnIn₂S₄ nanosheets at 2θ values of 21.44°, 27.42°, 32.80°, 47.45°, 52.48°, 55.72°, and 76.04° also match the crystal planes of its hexagonal crystal system (JCPDS 65-2023), with the (006) crystal plane being the most exposed. Because the peak intensity and intrinsic crystallinity of ZnIn2S4 are much weaker than those of Bi2WO6, the XRD peak positions and intensities of the composite ZnIn2S4 / Bi2WO6 heterojunction and the ZnIn2S4 / Bi2WO6 / Ag ternary hierarchical heterojunction are roughly the same as those of Bi2WO6, with only a significant ZnIn2S4 peak prominent at 2θ=27.42°. At other positions, two diffraction peaks overlap at the same angular position, resulting in a slight enhancement of the peak intensity at that location. Due to the low loading rate and small size of Ag nanoparticles, the characteristic peaks of Ag cannot be clearly observed in the XRD pattern of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
[0045] Depend on Figure 2 It provides a schematic diagram of the material preparation process and information on the SEM and TEM morphology of the prepared materials. Among these, Figure 2 In the diagram, 'a' represents the preparation process of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction. Figure 2 b in Figure 2 f in the image is a SEM image of the Bi2WO6 nanoplate. The image shows that the material has a nanoplate structure with a relatively smooth surface. Figure 2 e in Figure 2 In the image, i represents a SEM image of ZnIn2S4 nanosheets. This material is composed of nanosheet structures, with a large number of nanosheets stacked together to form a spherical structure. Figure 2 d in Figure 2 h in the image represents the SEM image of the Bi2WO6 / ZnIn2S4 heterostructure. In the sample, ZnIn2S4 nanosheets are densely embedded on the surface of Bi2WO6 material, forming a good heterostructure interface contact, which is significantly different from the smooth surface of Bi2WO6. Figure 2 c in Figure 2In the figure, g represents the low-magnification and high-magnification morphology characterization of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction. Since the Ag particles are too small to be directly observed by SEM characterization, their morphology is basically the same as that of the Bi2WO6 / ZnIn2S4 heterojunction. Figure 2 j in Figure 2 The k values in the images represent TEM images of Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunctions. Figure 2 The clear sheet-like structure pointed to by the lower left arrow in the image is ZnIn2S4, while the black area in the upper right is because high-energy electron beams cannot penetrate the thicker nanoplate-like structure of Bi2WO6. Figure 2 The prominent black circular particles within the circle in the diagram are Ag particles successfully deposited using photodeposition. SEM and TEM characterizations reveal that the longitudinal dimensions of the Bi₂WO₆ nanoplatelets range from 2 μm to 10 μm, the thickness of the ZnIn₂S₄ nanosheets ranges from 10 nm to 50 nm, and the size of the Ag nanoparticles ranges from 1 nm to 20 nm. Figure 2 The image 'l' represents an HRTEM image of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterostructure. This image clearly shows three lattice fringes. Measurements and data analysis revealed that these fringes correspond to the (131) crystal plane of Bi2WO6, the (006) crystal plane of ZnIn2S4, and the (101) crystal plane of Ag. This characterization further confirms the presence of Ag particles and that the three components within the Bi2WO6 / ZnIn2S4 / Ag heterostructure form a stable heterointerface. Figure 2 m- Figure 2 In the figure, t is represented by EDS, which shows that the elements Bi, W, O, Zn, I, S, and Ag are uniformly distributed in the corresponding regions.
[0046] Figure 3 X-ray photoelectron spectroscopy (XPS) of Bi2WO6, ZnIn2S4, Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag. Figure 3 In the ZnIn2S4 of a 2+ The binding energies are 1022.01 eV and 1045.00 eV, respectively, which is similar to that of Zn 2p. 3 / 2 and Zn 2p 1 / 2 The binding energy is consistent; Figure 3 In the b of ZnIn2S4, In 3+ The binding energies are 445.03 eV and 452.59 eV, which are similar to those of In 3d 5 / 2 and In 3d 3 / 2 Consistent, and Figure 3 a and Figure 3The binding energies of Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag in b are both slightly positively shifted. Figure 3 The S in c of ZnIn2S4 2- The binding energies of 161.83 eV and 163.09 eV correspond to S 2p, respectively. 3 / 2 S 2p 1 / 2 It can be seen that the binding energies of Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag also show a slight positive shift. Figure 3 Bi in c of Bi2WO6 3+ The double peaks at binding energies of 159.20 eV and 164.51 eV correspond to Bi⁴f, respectively. 7 / 2 and Bi 4f 5 / 2 , Figure 3 The W in Bi2WO6 in d 6+ The distinct bimodal binding energies of 35.51 eV and 37.64 eV correspond to W 4f 7 / 2 and W 4f 5 / 2 The binding energies of Bi2WO6 / ZnIn2S4 and Bi2WO6 / ZnIn2S4 / Ag both showed a negative shift relative to Bi2WO6, while... Figure 3 Bi in c 3+ The peak intensities of the bimodal graph also changed significantly. This suggests that the interaction between ZnIn2S4 and Bi2WO6 is not a simple physical interaction, but rather a potentially strong interfacial electronic interaction, which is consistent with their morphological characteristics. Figure 3 The results show that Bi2WO6 / ZnIn2S4 exhibits three distinct peaks at 530.07 eV, 531.96 eV, and 533.57 eV. Meanwhile, the binding energies of the three distinct peaks in Bi2WO6 / ZnIn2S4 / Ag are 530.05 eV, 531.73 eV, and 533.32 eV, respectively. Compared to the distinct double peaks of Bi2WO6 at 530.09 eV and 530.92 eV, this may be due to the formation of a heterojunction between ZnIn2S4 and Bi2WO6, leading to the formation of more oxygen vacancies. This also explains the improved gas-sensing performance. Figure 3 f in the figure represents the XPS spectrum of Ag. The two peaks corresponding to Ag in Bi2WO6 / ZnIn2S4 / Ag can be well attributed to the metallic state of Ag. At the same time, the loading of Ag nanoparticles can be obtained from the above energy spectrum and XPS characterization as 1 wt%~3 wt%.
[0047] To further analyze the microstructure of the samples, including specific surface area, pore volume, and average pore size, nitrogen adsorption-desorption isotherms and pore size distribution curves, along with tables of specific surface area, pore volume, and average pore size parameters for different samples, are provided below. Figure 4 As shown. Pure Bi2WO6 ( Figure 4 a) It exhibits a relatively low specific surface area (3.1071 m²). 2 The pore volume and pore width indicate a limited number of active sites. In contrast, pure ZnIn2S4 ( / g), Figure 4 b) has a specific surface area of 63.6040 m². 2 / g, with relatively large pore volume and slightly smaller pore width, indicating that its structure is more suitable for gas molecule adsorption and diffusion. Bi2WO6 / ZnIn2S4 ( Figure 4 c) Specific surface area (18.6438 m²) 2 The pore width and pore volume were significantly improved compared to pure Bi2WO6, while the pore volume was reduced compared to pure ZnIn2S4, indicating that the composite synthesis process effectively optimized the microstructure. Figure 4 d represents the nitrogen adsorption-desorption isotherm and pore size distribution curve of Bi2WO6 / ZnIn2S4 / Ag. Adding Ag slightly increases the specific surface area and pore volume compared to Bi2WO6 / ZnIn2S4, but slightly reduces the pore width. The table below shows the specific surface area, pore volume, and average pore size parameters of different samples, which strongly supports the above viewpoint.
[0048] Example 5 The detection of triethylamine gas using the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction prepared in Example 1 is as follows: (1) Five test points were selected within a temperature range of 200 ℃ to 300 ℃, and the test was repeated several times at each temperature test point. The response values of the four samples to triethylamine at different temperatures are as follows: Figure 5As shown in a and 5b, in an environment with a triethylamine concentration of 100 ppm, the response value of ZnIn2S4 generally shows an upward trend in the temperature range of 200 ℃ to 300 ℃, decreasing only at 275 ℃. Bi2WO6, on the other hand, shows an upward trend in the response value in the same temperature range, decreasing at 300 ℃. The response value of Bi2WO6 / ZnIn2S4 increases in the temperature range of 200 ℃ to 300 ℃. Bi2WO6 / ZnIn2S4 / Ag reaches its highest response value at 275 ℃ within the 200 ℃ to 300 ℃ range; therefore, 275 ℃ is set as the optimal operating temperature for this material. It can also be seen that Bi2WO6 / ZnIn2S4 / Ag exhibits a significant performance improvement at 275 ℃ compared to Bi2WO6 / ZnIn2S4, ZnIn2S4, and Bi2WO6.
[0049] (2) Under a triethylamine atmosphere with a concentration of 100 ppm, the dynamic response of different samples to triethylamine was recorded in continuous and repeated tests. Figure 6 Each sample was tested repeatedly for 5 cycles under the same conditions. In any cycle, the introduction of triethylamine gas was observed to immediately cause a change in the material's resistivity, which then tended to stabilize at a certain value. With the release of triethylamine and the introduction of air, the resistance eventually returned to its original value. Repeated testing over multiple cycles showed high stability. The construction of the heterostructure had a significant impact on the response to triethylamine gas. Compared with pure Bi2WO6 (… Figure 6 a) and pure ZnIn2S4 ( Figure 6 Compared to the response value of Bi2WO6 / ZnIn2S4 (b), Figure 6 c) The average response value increased significantly. Figure 6 d represents Bi2WO6 / ZnIn2S4 / Ag. Modification with precious metal silver nanoparticles is also an important means to improve gas sensing performance. By loading Ag nanoparticles onto Bi2WO6 / ZnIn2S4, the average response value is further improved.
[0050] (3) Dynamic sensing characteristics of different samples for different concentrations of triethylamine, such as Figure 7 As shown, within a certain concentration range, the response value is directly proportional to the concentration of triethylamine. That is, as the concentration of triethylamine increases, the response value of each sample also increases. However, when the concentration of triethylamine reaches a certain value, the response value will stabilize within a certain range and reach a saturation state. When the concentration of triethylamine is 20 ppm, it is difficult to detect Bi2WO6 (…). Figure 7 a) ZnIn2S4 ( Figure 7 b) and Bi2WO6 / ZnIn2S4 ( Figure 7 c) while Bi2WO6 / ZnIn2S4 / Ag ( Figure 7d) It can still respond to lower concentrations of gas. Importantly, Bi2WO6 / ZnIn2S4 / Ag exhibits significant advantages over various previously reported triethylamine sensors, particularly in terms of response value and operating temperature.
[0051] from Figure 8 This allows for a more systematic comparison of the response values of four samples with triethylamine concentrations ranging from 20 ppm to 1000 ppm. Therefore, it can be seen that Bi2WO6 / ZnIn2S4 / Ag has the highest response value, followed by Bi2WO6 / ZnIn2S4. By processing the data, the limit of detection (LOD) for triethylamine using Bi2WO6 / ZnIn2S4 / Ag can be obtained. Figure 8 b). Formula fitting shows that its detection limit is 819.4 ppb, far below the safe leakage value for triethylamine. For example... Figure 8 As shown in Figure c, when 100 ppm triethylamine gas is injected, the resistance response changes rapidly, with a response time of approximately 39 seconds. It takes approximately 197 seconds for the resistance to recover to 90% of its initial value. Furthermore, the responses of Bi₂WO₆ / ZnIn₂S₄ / Ag to 100 ppm triethylamine, ethanol, methanol, formaldehyde, acetic acid, formic acid, ethyl acetate, acetone, propanol, diethyl ether, and toluene gases were recorded and compared. The response values of Bi₂WO₆ / ZnIn₂S₄ / Ag to different gases at the same operating temperature and gas concentration were compared. Figure 8 (d) The results showed that it had excellent gas-sensitive selectivity for triethylamine.
[0052] Furthermore, Bi2WO6 / ZnIn2S4 / Ag exhibits excellent long-term stability against triethylamine. For example... Figure 9 As shown, after 60 days, Bi2WO6 / ZnIn2S4 / Ag still maintained a high response of over 110 after multiple cycle tests, and there was no significant performance degradation compared to 60 days ago.
[0053] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.
Claims
1. A Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction, characterized in that, The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction includes a substrate Bi2WO6 nanoplate, ZnIn2S4 nanosheets densely embedded on the surface of the Bi2WO6 nanoplate, and Ag nanoparticles uniformly dispersed on the ZnIn2S4 nanosheets. The Bi2WO6 nanoplate and the ZnIn2S4 nanosheet form a semiconductor heterostructure interface; the Ag nanoparticles form a semiconductor-metal heterostructure interface on the surface of the ZnIn2S4 nanosheet.
2. The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction according to claim 1, characterized in that, The longitudinal dimension of the Bi2WO6 nanoplate is 2 μm to 10 μm, the thickness of the ZnIn2S4 nanosheet is 10 nm to 50 nm, and the size of the Ag nanoparticles is 1 nm to 20 nm.
3. The Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction according to claim 1, characterized in that, The loading of the Ag nanoparticles is 1 wt% to 3 wt%; The specific surface area of the Bi2WO6 / ZnIn2S4 / Ag is 20 m². 2 / g~40 m 2 / g.
4. The method for preparing the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction according to any one of claims 1-3, characterized in that, Includes the following steps: Zinc chloride, indium chloride, and thioacetamide were dissolved in water, and the pH was adjusted to 1-3. Bi2WO6 nanoplates were added and reacted in a water bath. After the reaction was completed, the mixture was washed and dried to obtain a Bi2WO6 / ZnIn2S4 heterojunction. The silver nitrate solution was dissolved in water and mixed evenly with the Bi2WO6 / ZnIn2S4 heterojunction. Then, a photodeposition reaction was carried out. After the reaction was completed, the mixture was washed and dried to obtain the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction.
5. The preparation method according to claim 4, characterized in that, The Bi2WO6 nanoplates were prepared by the following steps: Bismuth oxide, tungsten oxide and sodium chloride were mixed and then ground with ethanol. After grinding, the mixture was dried and annealed. After annealing, the mixture was washed and dried to obtain the Bi2WO6 nanoplate.
6. The preparation method according to claim 5, characterized in that, The molar ratio of bismuth oxide, tungsten oxide, and sodium chloride is 1:1 to 3:5; The annealing temperature is 600 ℃~700 ℃, and the annealing time is 3 h~5 h.
7. The preparation method according to claim 4, characterized in that, The molar ratio of zinc chloride, indium chloride and thioacetamide is 1:1~3:1~4; The water bath reaction temperature is 60 ℃~100 ℃, and the water bath reaction time is 1 h~3 h.
8. The preparation method according to claim 4, characterized in that, The concentration of silver nitrate is 0.01 g / mol to 0.04 g / mol; The Bi2WO 6 / The ratio of ZnIn2S4 heterojunction to silver nitrate is 50 mg~200 mg: 0.1 mL~0.5 mL; The power of the mercury lamp used in the photodeposition reaction is 600 W to 1200 W, and the irradiation time is 0.3 h to 1.0 h.
9. A gas sensor, characterized in that, Includes the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction as described in any one of claims 1-3.
10. The application of the Bi2WO6 / ZnIn2S4 / Ag ternary hierarchical heterojunction as described in any one of claims 1-3 or the gas sensor as described in claim 9 in the detection of triethylamine gas.