A nitrogen dioxide gas sensor based on ZnTe-ZnSe heterojunction, a preparation method and application thereof

Abstract

The application provides a nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction, a preparation method and application thereof, and belongs to the technical field of electronic components. The technical scheme comprises a gold interdigital electrode and a gas-sensitive material coated on the surface of the gold interdigital electrode; the gas-sensitive material is a ZnTe-ZnSe heterojunction composite material, and the ZnTe-ZnSe heterojunction composite material comprises a micron block-shaped ZnTe matrix and ZnSe nanoparticles in-situ loaded on the surface of the ZnTe matrix. The application has the beneficial effects that the ZnTe-ZnSe heterojunction is used for room-temperature nitrogen dioxide detection for the first time, a one-step solvothermal method is adopted to construct a composite structure of micron block-shaped ZnTe and nano ZnSe particles, and the process is simple and low in cost. The response value of the sensor to 0.075 ppm NO2 reaches 1.96 at room temperature, the response value of the sensor to 1 ppm NO2 reaches 5.05, the response time is 35 seconds, the recovery time is 154 seconds, the sensor has excellent selectivity and long-term stability, ppb-level high-sensitivity detection is realized, and the comprehensive performance is significantly better than that of the prior art.

Description

Technical Field

[0001] This invention belongs to the field of electronic component technology, specifically relating to a nitrogen dioxide sensor based on a one-step solvothermal method for preparing a ZnTe-ZnSe heterojunction, its preparation technology, and detection method. The core focus is on the innovative application of ZnTe and its heterojunction materials in the field of gas sensing, enriching the research on zinc telluride in room temperature nitrogen dioxide gas sensing. The ZnTe-ZnSe nitrogen dioxide sensor has a detection range of 0.075 ppm to 1 ppm for nitrogen dioxide gas. Background Technology

[0002] With the acceleration of global industrialization and the expansion of urbanization, the emissions and sources of nitrogen dioxide (NO2) continue to increase. For the environment, NO2 is a key precursor to acid rain and photochemical smog, severely disrupting the ecological balance. For humans, even long-term exposure to low concentrations of NO2 can irritate the respiratory mucosa, causing bronchitis, asthma, and even increasing the risk of cardiovascular and cerebrovascular diseases. Therefore, developing an NO2 detection technology that can operate at room temperature and possesses high sensitivity, high selectivity, and rapid response characteristics has significant practical application value.

[0003] Currently, semiconductor gas sensors have become the mainstream research direction in the field of gas detection due to their advantages such as high sensitivity, small size, and low cost. However, traditional metal-oxide-semiconductor gas sensors operate at high temperatures, which not only consumes a lot of energy but also accelerates device aging, limiting their application in portable, low-power scenarios. Therefore, it is crucial to research a high-performance nitrogen dioxide sensor that can operate at room temperature.

[0004] In recent years, transition metal chalcogenides (TMDs) have shown great potential in the field of gas sensing due to their excellent properties such as high electron mobility and tunable band gap. Transition metal tellurides (TMTs), as an important branch of the TMDs family, inherit the core advantages of the family and perform outstandingly in the detection of gases such as ammonia, NO2, and hydrogen sulfide. In particular, they have the core characteristic of operating at room temperature, providing a new path to solve the pain points of traditional sensors.

[0005] It is worth noting that, among the transition metal tellurides, zinc telluride (ZnTe) exhibits excellent basic physicochemical properties, but current research focuses mainly on fields such as photoelectric conversion and solar cells, while exploration in the important application direction of gas sensing is still relatively lacking.

[0006] Based on this, this invention focuses on material system innovation, using a one-step solvothermal method to prepare ZnTe-ZnSe heterojunction materials, and systematically studies their microstructure and gas-sensing performance, providing new ideas and directions for gas sensor material systems. Summary of the Invention

[0007] The purpose of this invention is to explore the room temperature gas sensing potential of ZnTe materials. To address the technical limitations of traditional gas sensors, a simple one-step solvothermal method is used to prepare ZnTe-ZnSe heterojunction materials, providing a nitrogen dioxide sensor with high sensitivity, strong stability, and a low detection limit.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction includes a gold interdigitated electrode and a gas-sensitive material coated on the surface of the gold interdigitated electrode; the gas-sensitive material is a ZnTe-ZnSe heterojunction composite material, which includes a micron-sized bulk ZnTe matrix and ZnSe nanoparticles in situ loaded on the surface of the ZnTe matrix.

[0009] Further, the molar ratio of ZnTe to ZnSe is (8-14):1, preferably 10:1; the coating thickness of the gas-sensitive material on the surface of the gold interdigitated electrode is 20-80 μm; the gold interdigitated electrode is an alumina substrate with a pure gold electrode on the front, the number of interdigitated electrode pairs is 3-10 pairs, and the thickness of the alumina substrate is 2-5 μm; the operating temperature of the sensor is room temperature.

[0010] Furthermore, the sensor has a detection range of 0.075ppm-1ppm for nitrogen dioxide; at room temperature, its response value to 1ppm nitrogen dioxide is at least 3.3, its response time is no more than 35 seconds, and its recovery time is no more than 154 seconds.

[0011] This invention also includes a fabrication process for a nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction as described above, the steps of which are as follows: S1: Dissolve zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate in deionized water in sequence, control the molar ratio of sodium tellurite and sodium selenite pentahydrate, and stir vigorously to form a milky white suspension. S2: Add ethanolamine and hydrazine hydrate sequentially to the suspension obtained in step S1, and stir until a homogeneous solution is formed; S3: Transfer the solution obtained in step S2 to a hydrothermal reactor and carry out a hydrothermal reaction at a certain temperature; S4: After the reaction is completed, solid-liquid separation is achieved by centrifugation, and the product is repeatedly washed with deionized water and anhydrous ethanol. The obtained solid product is dried to obtain ZnTe-ZnSe heterojunction composite material. S5: Disperse the ZnTe-ZnSe heterojunction composite material obtained in step S4 in deionized water to obtain a dispersion; S6: Apply the dispersion obtained in step S5 to the surface of the gold interdigitated electrode. S7: Dry the coated gold interdigitated electrodes and allow them to cool naturally to room temperature to obtain the nitrogen dioxide gas sensor.

[0012] Further, the molar ratio of sodium tellurite and sodium selenite pentahydrate in step S1 is (8-14):1, preferably 10:1.

[0013] Furthermore, the amounts of zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate used in step S1 are such that the final molar ratio of ZnTe to ZnSe is 10:1.

[0014] Further, the hydrothermal reaction temperature in step S3 is 200℃; the drying conditions in step S4 are drying at 60℃ for 6 hours in a vacuum drying oven; the dispersion in step S5 is obtained by wet grinding the ZnTe-ZnSe heterojunction composite material in a mortar with deionized water; the coating thickness in step S6 is 20-80μm; and the drying conditions in step S7 are drying at 60℃ for 6 hours in a vacuum drying oven.

[0015] Furthermore, the amount of deionized water used in step S1 is 20 ml, the amount of ethanolamine used in step S2 is 30 ml, and the amount of hydrazine hydrate used is 10 ml.

[0016] The present invention also includes the application of the nitrogen dioxide gas sensor as described above or the nitrogen dioxide gas sensor prepared by the above-described process in the detection of nitrogen dioxide, wherein the application is carried out at room temperature and the detection range of nitrogen dioxide is 0.075ppm-1ppm.

[0017] Furthermore, the applications include indoor air quality monitoring, industrial exhaust emission detection, or trace nitrogen dioxide detection in environmental pollutant tracing.

[0018] The beneficial effects of this invention are: Compared with existing technologies, the nitrogen dioxide gas sensor based on ZnTe-ZnSe heterojunction, its preparation method, and its application described in this invention have the following technical features and beneficial effects: (1) The preparation process has significant advantages, low cost and outstanding industrialization potential.

[0019] This invention employs a one-step solvothermal method to prepare ZnTe / ZnSe heterojunction composite materials. The core principle of this method is to utilize the high temperature and high pressure environment of the solvothermal reaction system to enable the reaction precursors (zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate) to undergo a synergistic reaction in a closed space. By precisely controlling the molar ratio of sodium tellurite to sodium selenite pentahydrate (10:1), the in-situ generation of ZnTe micron-sized bulk matrix and the simultaneous loading of ZnSe nanoparticles are achieved without the need for subsequent modification or composite steps, thus avoiding the problems of product contamination, structural damage, and increased costs caused by multi-step processes from the source. This preparation method has multiple technical advantages: First, the raw materials (zinc acetate dihydrate, sodium tellurite, sodium selenite pentahydrate, etc.) are all commercially available conventional chemicals, widely available and inexpensive, significantly reducing the raw material cost of material preparation; Second, the process steps are simple and controllable, requiring only basic operations such as dissolution, stirring, hydrothermal reaction, centrifugal cleaning, and drying, without the need for complex equipment and harsh reaction conditions, making it easy to scale up production; Third, the closed environment of the solvothermal reaction can effectively suppress the introduction of impurities, while the high temperature and high pressure conditions promote the crystallinity of the product, ensuring high purity and uniform microstructure of the composite material. (2) Material innovation fills research gaps and expands the boundaries of technology application.

[0020] This invention explores the gas-sensing application potential of ZnTe materials, breaking the long-standing limitation of ZnTe's application mainly in optoelectronics and photovoltaics, effectively filling the research gap in the gas-sensing field, and providing a new direction for material innovation in gas sensors. Simultaneously, using ZnTe / ZnSe heterojunctions as a research platform, this invention deeply reveals the structure-property relationship of gas-sensing composites of transition metal tellurides (TMTs) and their congeners. This not only provides key theoretical basis and practical support for the functional expansion of transition metal tellurides, but also broadens the application scenarios of TMTs materials, promoting the diversified development of the gas-sensing materials field.

[0021] (3) The synergistic innovation of structure and mechanism has greatly improved the overall detection performance.

[0022] This invention cleverly utilizes the electronegativity difference between Te and Se anions to construct a novel ZnTe / ZnSe heterojunction composite gas-sensitive material in the same solvothermal system by using micron-sized bulk ZnTe as a matrix and loading ZnSe nanoparticles in situ on its surface.

[0023] In terms of macroscopic structure, the micron-sized bulk ZnTe provides a stable framework support, while the surface-modified ZnSe nanoparticles greatly increase the specific surface area of ​​the material, providing high-density and highly active adsorption sites for NO2 molecules, significantly enhancing gas adsorption capacity and response signal intensity, thus laying the foundation for high sensitivity and fast response of the sensor from a structural perspective.

[0024] At the microscopic interface and electron transport level, ZnTe and ZnSe belong to Group II-VI compounds and have the same anion (Te and Se are both Group VIA elements), exhibiting high lattice matching and good interfacial compatibility. When they form a heterojunction, the interface is smooth, the defect density is low, and the band structure is mild and ordered, effectively suppressing carrier recombination and achieving smooth and controllable interfacial electron transfer.

[0025] This unique micron-bulk-nanoparticle composite + homogeneous anion heterojunction synergistic system not only solves the problems of insufficient specific surface area and few adsorption sites of single materials, but also avoids the drawbacks of traditional heterojunction interfaces with many defects and violent and uncontrollable electron transfer. This enables the material to have high response, high selectivity, good stability and excellent recovery performance in the NO2 detection process, and significantly improves the comprehensive detection performance of the nitrogen dioxide sensor from the perspective of material design and working mechanism.

[0026] (4) Excellent performance indicators, wide range of application scenarios and high practical value.

[0027] The ZnTe / ZnSe heterojunction gas sensor prepared in this invention possesses high sensitivity for detecting NO2 at the ppb level at room temperature—a response value of 1.96 for 0.075 ppm NO2, a 34% improvement over pure ZnTe sensors; and a response value as high as 5.05 for 1 ppm NO2, a 75% improvement over pure ZnTe. Furthermore, the response time is as short as 35 seconds and the recovery time as low as 154 seconds, demonstrating fast response and high responsivity. Simultaneously, thanks to the selective electron transfer characteristics of the heterojunction, the sensor exhibits excellent anti-interference capability against NO2, effectively avoiding cross-interference from other common gases (such as formaldehyde, ammonia, and ethanol), demonstrating superior selectivity.

[0028] This sensor can operate at room temperature without the need for a heating device, which not only reduces energy consumption and operating costs, but also avoids the stability degradation caused by high-temperature environments. It can meet the trace NO2 detection needs in various scenarios such as indoor air quality monitoring, industrial exhaust emission detection, and environmental pollutant tracing. It is a high-performance, low-cost, and highly practical room temperature NO2 sensor with broad market application prospects and huge economic value. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. 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. Wherein: Figure 1 This is a scanning electron microscope (SEM) image of the ZnTe-ZnSe heterojunction composite material of the present invention. Figure 2 The graph shows the response curves of the gas sensor of pure ZnTe and ZnTe-ZnSe composite materials of the present invention to 1 ppm nitrogen dioxide at room temperature. Figure 3 The graph shows the response of the ZnTe-ZnSe heterojunction composite gas sensor of the present invention to nitrogen dioxide at room temperature from 0.075 ppm to 1 ppm. Figure 4 This is a cyclic test curve of the ZnTe-ZnSe heterojunction composite material of the present invention against 1 ppm NO2 at room temperature; Figure 5 This is a cyclic test curve of the ZnTe-ZnSe heterojunction composite material of the present invention at room temperature against 0.075 ppm NO2; Figure 6 This is a graph showing the 30-day long-term stability test of the ZnTe-ZnSe heterojunction composite gas sensor of the present invention against 1 ppm nitrogen dioxide at room temperature. Figure 7 This is a comparison chart of the response values ​​of the ZnTe-ZnSe heterojunction composite gas sensor of the present invention to 1 ppm nitrogen dioxide and 10 ppm other gases at room temperature. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The following description, in conjunction with the accompanying drawings... Figure 1-7 The nitrogen dioxide gas sensor based on ZnTe-ZnSe heterojunction, its preparation method, and its application are further explained.

[0031] Example 1 A nitrogen dioxide gas sensor based on ZnTe-ZnSe heterojunction is mainly composed of a gas-sensitive material and gold interdigitated electrodes. The gas-sensitive material is coated on the surface of the interdigitated electrodes with a coating thickness of 20-80 μm. The gas-sensitive material is a composite material of ZnTe and ZnSe heterojunction.

[0032] The gold interdigitated electrode is an alumina substrate with pure gold electrodes on the front side, with 3-10 pairs of interdigitated electrodes and a substrate thickness of 2-5 μm.

[0033] The nitrogen dioxide sensor operates at room temperature.

[0034] A fabrication process for a nitrogen dioxide gas sensor based on a ZnTe and ZnSe heterojunction is described below: Zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate were dissolved sequentially in deionized water, with the molar ratio of sodium tellurite to sodium selenite pentahydrate controlled at 10:1. The mixture was stirred vigorously to form a uniform milky white suspension. Add appropriate amounts of ethanolamine and hydrazine hydrate to the above solution in sequence, and stir until a homogeneous solution is formed; The solution obtained in step (2) was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 180℃-220℃ for 24 hours. After the reaction, solid-liquid separation was achieved by centrifugation, and the product was repeatedly washed with deionized water and anhydrous ethanol. The obtained solid product was placed in a vacuum drying oven and dried at 60℃ for 6 hours to finally obtain the ZnTe and ZnSe heterojunction composite material. The ZnTe-ZnSe heterojunction composite material was placed in a mortar, and an appropriate amount of deionized water was added for wet grinding. The dispersion was then coated onto the surface of the gold interdigitated electrode and placed in a vacuum drying oven at 60°C for 6 hours. After natural cooling to room temperature, the ZnTe-ZnSe heterojunction composite gas sensor was obtained.

[0035] The working principle of this invention is as follows: When a semiconductor material comes into contact with a target gas, gas molecules undergo electron transfer with the semiconductor surface, resulting in a change in the carrier concentration inside the material, which in turn manifests as a change in the semiconductor resistance. By detecting the magnitude and rate of the resistance change, the type and concentration of the gas to be tested can be identified.

[0036] The semiconductor material used in this invention has a work function lower than the affinity of nitrogen dioxide molecules for charge carriers. Therefore, when nitrogen dioxide molecules adsorb onto the semiconductor surface, they capture electrons from the material, causing a change in charge carrier concentration and ultimately a change in the material's conductivity. In this way, the sensor can output a corresponding detection signal based on the real-time change in resistance.

[0037] Example 2 (1) Add 0.132g zinc acetate dihydrate and 0.133g sodium tellurite to 20ml of deionized water in sequence and stir for 20min at room temperature.

[0038] (2) Add 30 ml of ethanolamine and 10 ml of hydrazine hydrate to the above solution in sequence, and stir for 15 min to form a transparent solution with a black precipitate.

[0039] (3) The solution obtained in step (2) was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 200°C for 24 h. After hydrothermal reaction, the product was centrifuged at 3000 rpm for 10 min to separate the solid and liquid phases, resulting in a reddish-brown solid. The solid product was washed three times with deionized water and ethanol, respectively. The solid product was then placed in a vacuum drying oven and kept at 60°C for 6 h to obtain pure phase zinc telluride material.

[0040] (4) Disperse the pure phase ZnTe material in 50 μl of deionized water in a mortar and continue grinding for 5-10 min until a uniform dispersion is formed. Take 20 μl of the dispersion and coat it evenly on the surface of the gold interdigitated electrode. Place it in a vacuum drying oven at 60°C for 6 h and allow it to cool naturally to room temperature to obtain a pure ZnTe material gas sensor.

[0041] Example 3 (1) Add 0.148g zinc acetate dihydrate, 0.133g sodium tellurite and 0.0197g sodium selenite pentahydrate to 20ml of deionized water in sequence and stir for 20min at room temperature.

[0042] (2) Add 30 ml of ethanolamine and 10 ml of hydrazine hydrate to the above solution in sequence, stir for 20 min to form a transparent solution with black precipitate and slightly yellow color.

[0043] (3) The solution obtained in step (2) was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 200°C for 24 h. After hydrothermal reaction, the product was centrifuged at 3000 rpm for 10 min to separate solid and liquid, and an orange-red solid was obtained. The solid product was washed three times with deionized water and ethanol respectively. The obtained solid product was placed in a vacuum drying oven and kept at 60°C for 6 h to obtain ZnTe-ZnSe heterojunction composite material, wherein the molar ratio of ZnTe to ZnSe was 8:1.

[0044] (4) Disperse the pure phase ZnTe material in 50 μl of deionized water in a mortar and continue grinding for 5-10 min until a uniform dispersion is formed. Take 20 μl of the dispersion and coat it evenly on the surface of the gold interdigitated electrode. Place it in a vacuum drying oven at 60°C for 6 h and allow it to cool naturally to room temperature to obtain the ZnTe-ZnSe composite gas sensor.

[0045] Example 4 (1) Add 0.1449g zinc acetate dihydrate, 0.133g sodium tellurite and 0.0157g sodium selenite pentahydrate to 20ml of deionized water in sequence and stir for 20min at room temperature.

[0046] (2) Add 30 ml of ethanolamine and 10 ml of hydrazine hydrate to the above solution in sequence, stir for 20 min to form a transparent solution with black precipitate and slightly yellow color.

[0047] (3) The solution obtained in step (2) was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 200°C for 24 h. After hydrothermal reaction, the product was centrifuged at 3000 rpm for 10 min to separate solid and liquid, and an orange-red solid was obtained. The solid product was washed three times with deionized water and ethanol respectively. The obtained solid product was placed in a vacuum drying oven and kept at 60°C for 6 h to obtain ZnTe and ZnSe heterojunction composite material, wherein the molar ratio of ZnTe to ZnSe was 10:1.

[0048] (4) Disperse the pure phase ZnTe material in 50 μl of deionized water in a mortar and continue grinding for 5-10 min until a uniform dispersion is formed. Take 20 μl of the dispersion and coat it evenly on the surface of the gold interdigitated electrode. Place it in a vacuum drying oven at 60°C for 6 h and allow it to cool naturally to room temperature to obtain the ZnTe-ZnSe composite gas sensor.

[0049] Example 5 Add 0.142g zinc acetate dihydrate, 0.133g sodium tellurite and 0.013g sodium selenite pentahydrate sequentially to 20ml of deionized water and stir for 20min at room temperature.

[0050] Add 30 ml of ethanolamine and 10 ml of hydrazine hydrate to the above solution in sequence, stir for 20 min to form a transparent solution with a black precipitate and a slightly yellow appearance.

[0051] The solution obtained in step (2) was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to a hydrothermal reaction at 200°C for 24 hours. After the hydrothermal reaction was completed, the product was centrifuged at 3000 rpm for 10 minutes to separate the solid and liquid phases, resulting in an orange-red solid. The solid product was washed three times with deionized water and ethanol, respectively. The obtained solid product was placed in a vacuum drying oven and kept at 60°C for 6 hours to obtain a ZnTe-ZnSe heterojunction composite material, wherein the molar ratio of ZnTe to ZnSe was 12:1.

[0052] The pure-phase ZnTe material was dispersed in 50 μl of deionized water in a mortar and ground continuously for 5-10 min until a uniform dispersion was formed. 20 μl of the dispersion was taken and evenly coated onto the surface of the interdigitated gold electrode. The electrode was then placed in a vacuum drying oven at 60°C for 6 h and allowed to cool naturally to room temperature to obtain the ZnTe-ZnSe composite gas sensor.

[0053] Example 6 Add 0.141g zinc acetate dihydrate, 0.133g sodium tellurite and 0.011g sodium selenite pentahydrate sequentially to 20ml of deionized water and stir for 20min at room temperature.

[0054] Add 30 ml of ethanolamine and 10 ml of hydrazine hydrate to the above solution in sequence, stir for 20 min to form a transparent solution with a black precipitate and a slightly yellow appearance.

[0055] The solution obtained in step (2) was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to a hydrothermal reaction at 200°C for 24 hours. After the hydrothermal reaction was completed, the product was centrifuged at 3000 rpm for 10 minutes to separate the solid and liquid phases, resulting in an orange-red solid. The solid product was washed three times with deionized water and ethanol, respectively. The obtained solid product was placed in a vacuum drying oven and kept at 60°C for 6 hours to obtain a ZnTe-ZnSe heterojunction composite material, wherein the molar ratio of ZnTe to ZnSe was 14:1.

[0056] The pure-phase ZnTe material was dispersed in 50 μl of deionized water in a mortar and ground continuously for 5-10 min until a uniform dispersion was formed. 20 μl of the dispersion was taken and evenly coated onto the surface of the interdigitated gold electrode. The electrode was then placed in a vacuum drying oven at 60°C for 6 h and allowed to cool naturally to room temperature to obtain the ZnTe-ZnSe composite gas sensor.

[0057] Comparative analysis of results from examples: In the five embodiments described above, by changing the ZnTe to ZnSe composite ratio, five sensors with different performances were obtained, leading to the conclusion that: As shown in Figure 2, in the 1ppm NO2 concentration gradient test, the response value of the ZnTe-ZnSe composite sensor showed a trend of first increasing and then decreasing with the ZnSe doping amount, intuitively reflecting the structure-property relationship between doping amount and gas sensing performance. When the ZnTe to ZnSe doping ratio was 14:1, the response value increased to 3.3, and further climbed to 4.4 at 12:1. At the optimal doping ratio of 10:1, the response value reached a peak of 5.05, which is 75% higher than that of pure ZnTe. At the same time, the response time was shortened to 35 seconds and the recovery time was reduced to 154 seconds, showing the best overall performance. In low-concentration detection, the response value of this proportional sensor to 75ppb NO2 reached 1.96, which is 34% higher than that of pure ZnTe, effectively breaking through the bottleneck of low-concentration detection. This performance optimization stems from the structural advantage of ZnTe and ZnSe both belonging to group II-VI semiconductors. With appropriate doping levels, ZnSe nanoparticles are uniformly dispersed to form high-density, low-defect heterojunctions, which not only optimizes the interfacial electron transport efficiency and reduces carrier recombination, but also increases active sites through the "matrix + nanoparticle" dual adsorption system. At the same time, it regulates the surface electron density and reduces the gas adsorption energy, thereby achieving a simultaneous improvement in sensitivity and kinetic performance.

[0058] When the ZnSe doping ratio was further increased to 8:1, the sensor response value dropped significantly, which is the result of the synergistic effect of the material's microstructure and gas-sensing mechanism. Excess ZnSe nanoparticles agglomerate on the ZnTe surface to form a continuous capping layer. On the one hand, this layer occupies a large number of active sites in the matrix, and since ZnSe's own gas-sensing activity is lower than that of the heterojunction synergistic system, the number of effective adsorption sites is reduced. On the other hand, the agglomeration layer increases electron transport paths, induces lattice defects, disrupts the heterojunction bandgap matching, and inhibits the effectiveness of carrier migration and electron transfer, ultimately leading to a decline in sensing performance. In summary, the NO2 sensing performance of the ZnTe-ZnSe composite material is the result of the mutual balance between the "heterojunction synergistic enhancement effect" and the "active site competition effect." The 10:1 doping ratio achieves the optimal balance between the two effects. This study clarifies the optimal doping window and micro-control mechanism, providing important theoretical and technical support for the design of high-performance NO2 sensors.

[0059] In existing technologies, research on ZnTe materials mainly focuses on photoelectric conversion and solar cells, with its application in gas sensing remaining largely unexplored. This invention is the first to apply ZnTe-based heterojunction materials to room-temperature nitrogen dioxide detection. A one-step solvothermal method is employed, using zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate as precursors. By precisely controlling the molar ratio of sodium tellurite to sodium selenite pentahydrate to 10:1, a ZnTe-ZnSe heterojunction composite material is synthesized in a single step under high temperature and pressure. This method eliminates the need for subsequent modification or composite steps, avoiding contamination and structural damage caused by multi-step processes. The raw materials are all commercially available conventional chemicals, making the process simple, low-cost, and easy to scale up. Compared to the technical drawback of traditional metal oxide sensors requiring high-temperature operation, the sensor prepared by this invention can operate at room temperature, significantly reducing energy consumption and extending device lifespan.

[0060] Existing semiconductor gas sensors generally suffer from problems such as insufficient specific surface area, few adsorption sites, numerous heterojunction interface defects, and uncontrollable electron transfer. This invention cleverly utilizes the electronegativity difference between Te and Se, both belonging to Group VIA, to construct a composite structure of "micron-sized bulk ZnTe matrix + in-situ loading of nano-sized ZnSe particles." Micron-sized ZnTe provides stable scaffold support, while surface-modified ZnSe nanoparticles significantly increase the specific surface area, providing high-density, highly active adsorption sites for NO2 molecules. More importantly, ZnTe and ZnSe belong to Group II-VI compounds, exhibiting high lattice matching and good interfacial compatibility. The resulting heterojunction interface is smooth, with low defect density and a mild, ordered band structure, effectively suppressing carrier recombination and achieving smooth and controllable interfacial electron transfer. This synergistic innovation of structural design and band matching solves the dual technical challenges of insufficient adsorption capacity of single materials and numerous interface defects in traditional heterojunctions.

[0061] Based on the aforementioned material and structural innovations, the ZnTe-ZnSe heterojunction gas sensor of this invention achieves highly sensitive detection of nitrogen dioxide at the ppb level at room temperature. Specifically, the response value to 0.075 ppm NO2 reaches 1.96, a 34% improvement compared to a pure ZnTe sensor; the response value to 1 ppm NO2 is as high as 5.05, a 75% improvement compared to pure ZnTe, with a response time as short as 35 seconds and a recovery time as low as 154 seconds. Cyclic testing and 30-day long-term stability testing show that the sensor has good repeatability and stability. Selectivity testing shows that the sensor's response value to NO2 is much higher than that of interfering gases such as formaldehyde, ammonia, and ethanol at 10 ppm, demonstrating excellent anti-interference ability. In addition, the sensor's detection range is 0.075 ppm-1 ppm, covering trace NO2 detection needs in various scenarios such as indoor air quality monitoring, industrial exhaust emission detection, and environmental pollutant tracing. The room temperature nitrogen dioxide sensor provided by this invention combines the comprehensive advantages of high sensitivity, high selectivity, fast response and recovery, good stability, and low cost, and has broad market application prospects and significant economic value.

[0062] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction, characterized in that, It includes a gold interdigitated electrode and a gas-sensitive material coated on the surface of the gold interdigitated electrode; the gas-sensitive material is a ZnTe-ZnSe heterojunction composite material, which includes a micron-sized bulk ZnTe matrix and ZnSe nanoparticles in situ loaded on the surface of the ZnTe matrix.

2. The nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction according to claim 1, characterized in that, The molar ratio of ZnTe to ZnSe is (8-14):1, preferably 10:1; the coating thickness of the gas-sensitive material on the surface of the gold interdigitated electrode is 20-80 μm; the gold interdigitated electrode is an alumina substrate with a pure gold electrode on the front, the number of interdigitated electrode pairs is 3-10 pairs, and the thickness of the alumina substrate is 2-5 μm; the operating temperature of the sensor is room temperature.

3. The nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction according to claim 1 or 2, characterized in that, The sensor has a detection range of 0.075ppm-1ppm for nitrogen dioxide; at room temperature, the response value for 1ppm nitrogen dioxide is at least 3.3, the response time is no more than 35 seconds, and the recovery time is no more than 154 seconds.

4. A fabrication process for a nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction as described in any one of claims 1 to 3, characterized in that, The steps are as follows: S1: Dissolve zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate in deionized water in sequence, control the molar ratio of sodium tellurite and sodium selenite pentahydrate, and stir vigorously to form a milky white suspension. S2: Add ethanolamine and hydrazine hydrate sequentially to the suspension obtained in step S1, and stir until a homogeneous solution is formed; S3: Transfer the solution obtained in step S2 to a hydrothermal reactor and carry out a hydrothermal reaction at a certain temperature; S4: After the reaction is completed, solid-liquid separation is achieved by centrifugation, and the product is repeatedly washed with deionized water and anhydrous ethanol. The obtained solid product is dried to obtain ZnTe-ZnSe heterojunction composite material. S5: Disperse the ZnTe-ZnSe heterojunction composite material obtained in step S4 in deionized water to obtain a dispersion; S6: Apply the dispersion obtained in step S5 to the surface of the gold interdigitated electrode. S7: Dry the coated gold interdigitated electrodes and allow them to cool naturally to room temperature to obtain the nitrogen dioxide gas sensor.

5. The fabrication process of the nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction according to claim 4, characterized in that, The molar ratio of sodium tellurite and sodium selenite pentahydrate in step S1 is (8-14):1, preferably 10:

1.

6. The fabrication process of the nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction according to claim 4, characterized in that, The amounts of zinc acetate dihydrate, sodium tellurite, and sodium selenite pentahydrate used in step S1 result in a final molar ratio of ZnTe to ZnSe of 10:

1.

7. The fabrication process of the nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction according to claim 4, characterized in that, The hydrothermal reaction temperature in step S3 is 200℃; the drying conditions in step S4 are drying at 60℃ for 6 hours in a vacuum drying oven; the dispersion in step S5 is obtained by wet grinding the ZnTe-ZnSe heterojunction composite material in a mortar with deionized water; the coating thickness in step S6 is 20-80μm; and the drying conditions in step S7 are drying at 60℃ for 6 hours in a vacuum drying oven.

8. The fabrication process of the nitrogen dioxide gas sensor based on a ZnTe-ZnSe heterojunction according to claim 4, characterized in that, The amount of deionized water used in step S1 is 20 ml, the amount of ethanolamine used in step S2 is 30 ml, and the amount of hydrazine hydrate used is 10 ml.

9. The application of a nitrogen dioxide gas sensor as described in any one of claims 1 to 3, or a nitrogen dioxide gas sensor prepared by the process described in any one of claims 4 to 8, in the detection of nitrogen dioxide, characterized in that, The application was performed at room temperature, and the detection range for nitrogen dioxide was 0.075 ppm to 1 ppm.

10. The application of the nitrogen dioxide gas sensor according to claim 9 in the detection of nitrogen dioxide, characterized in that, The applications include indoor air quality monitoring, industrial exhaust emission detection, or trace nitrogen dioxide detection in environmental pollutant tracing.

Images