Gas sensor

Abstract

The present disclosure provides a gas sensor, which includes a sensing electrode module and a resistance meter, and the resistance meter is electrically connected to the sensing electrode module. The sensing electrode module includes a substrate, a plurality of sensing electrodes disposed on one side of the substrate, and a sensing layer covering the sensing electrodes, and the sensing layer includes a transition metal diselenide material. Therefore, the gas sensor of the present disclosure has high sensitivity and high selectivity.

Description

Technical Field

[0001] This disclosure relates to a sensor, and more particularly to a gas sensor. Background Technology

[0002] With the rapid development of technology, the demand for gas sensors with high sensitivity and selectivity is increasing. Current gas sensors experience performance degradation after prolonged use, affecting their sensing reliability and lifespan. Electrochemical gas sensors, in particular, are susceptible to harsh environments, leading to poor sensing stability. Semiconductor gas sensors are less affected by harsh environments; however, they require high-temperature operation, increasing energy consumption costs and potentially negatively impacting long-term operating costs.

[0003] In addition, when sensing corrosive gases, the sensing element of the gas sensor is easily corroded and damaged by the corrosive gases. Hydrogen sulfide and ammonia have particularly serious negative effects on gas sensors, thus limiting the application of gas sensors and increasing the maintenance cost of gas sensors.

[0004] In view of this, the development of a gas sensor that can sense at room temperature and has high environmental tolerance, high sensitivity and high selectivity has been the goal of the industry for a long time. Summary of the Invention

[0005] The purpose of this disclosure is to provide a gas sensor that has high sensitivity, high selectivity and resistance to chemical corrosion.

[0006] One embodiment of this disclosure provides a gas sensor, including a sensing electrode module and a resistor, wherein the resistor is electrically connected to the sensing electrode module. The sensing electrode module includes a bottom layer, a plurality of sensing electrodes and a sensing layer, wherein the sensing electrodes are disposed on one side of the bottom layer, the sensing layer covers the sensing electrodes, and the sensing layer includes a transition metal diselenide material.

[0007] According to the gas sensor described above, the thickness of the transition metal diselenide material can be from 1.2 nm to 45 nm.

[0008] Based on the gas sensor described above, the transition metal diselenide material may have a single crystal phase or a polycrystalline phase.

[0009] According to the gas sensor described above, the transition metal diselenide material includes a transition metal layer and a selenium atom layer. The transition metal layer may include a transition metal source, and the selenium atom layer may be covalently bonded to one side of the transition metal layer.

[0010] Based on the gas sensor described above, the transition metal source of the transition metal diselenide material can be molybdenum, tungsten, tin, or platinum.

[0011] Based on the gas sensor described above, the transition metal diselenide material can be prepared by a plasma-assisted deposition method.

[0012] According to the gas sensor described above, the plasma-assisted deposition method may include the following steps: A solid selenium element is heated at a heating temperature to form a selenium element gas, wherein the heating temperature may be from 150°C to 300°C. A reactive gas is introduced at a plasma operating power to assist the selenium element gas in forming a selenium element plasma, wherein the reactive gas includes nitrogen, hydrogen, or a combination thereof, and the plasma operating power may be greater than 0W and less than or equal to 500W. A substrate is provided, which may include a base material and a coating layer, the coating layer being disposed on a surface of the base material, and the coating layer being deposited corresponding to the selenium element plasma at a reaction temperature and a reaction pressure to form a transition metal diselenide material. The thickness of the coating layer may be from 1 nm to 40 nm, and the coating layer may include a transition metal source.

[0013] Based on the gas sensor described above, the volume ratio of nitrogen to hydrogen in the reaction gas can be 0:1, 1:3, 1:1, 3:1, 2:1, or 1:0.

[0014] Based on the gas sensor described above, the volume ratio of nitrogen to hydrogen in the reaction gas can be 1:1, 3:1, or 2:1.

[0015] Based on the gas sensor described above, the reaction temperature can be from 100°C to 550°C. Attached Figure Description

[0016] To make the above and other objects, features, advantages and embodiments of this disclosure more apparent and understandable, the accompanying drawings are described below:

[0017] Figure 1 This is a schematic diagram illustrating a gas sensor according to one embodiment of the present disclosure;

[0018] Figure 2 This is a flowchart illustrating the steps of a plasma-assisted deposition method for preparing a transition metal diselenide material in a gas sensor according to an embodiment of the present disclosure;

[0019] Figure 3 It is a drawing according to Figure 2 A schematic diagram of the plasma-assisted process system used in the plasma-assisted deposition method;

[0020] Figure 4A The XRD patterns are for Experiment 1, Experiment 2, Experiment 3 and Experiment 4;

[0021] Figure 4B The XRD pattern of Experiment Example 7;

[0022] Figure 4C The XRD pattern of Experiment Example 9;

[0023] Figure 5 The graph shows the real-time sensing response results of nitrogen dioxide from 1 ppm to 25 ppm for Examples 1, 2, 3 and 4.

[0024] Figure 6 Linear graphs of sensing different concentrations of nitrogen dioxide for Examples 1, 2, 3, and 4;

[0025] Figure 7 This is a graph showing the sensing response results of Example 1;

[0026] Figure 8 The sensing selectivity results are shown in Examples 5, 6, 7, and 8; and

[0027] Figure 9 The image shows the sensing response results for different gases in Example 9.

[0028] The reference numerals in the attached figures are explained as follows:

[0029] 100: Gas sensor

[0030] 200: Resistance meter

[0031] 300: Sensing Electrode Module

[0032] 310: Bottom Layer

[0033] 320: Sensing electrode

[0034] 330: Sensing layer

[0035] 400: Plasma-assisted deposition method

[0036] 401, 402, 403: Steps

[0037] 410: Plasma-assisted process system

[0038] 411: Gas Inlet

[0039] 412: First Space

[0040] 413: Gas outlet

[0041] 414: The Second Space

[0042] 415: Selenium Plasma

[0043] 416: Inductively Coupled Plasma Coil

[0044] 417: Substrate

[0045] 418: Reactive gas

[0046] 419: Selenium element solid

[0047] 420: Transition metal diselenide materials Detailed Implementation

[0048] The various embodiments of this disclosure will be discussed in more detail below. However, these embodiments can be applications of various inventive concepts and can be implemented in various different specific scopes. The specific embodiments are for illustrative purposes only and are not limited to the scope of the disclosure.

[0049] <Gas Sensor>

[0050] Please refer to Figure 1 This is a schematic diagram illustrating a gas sensor 100 according to one embodiment of the present disclosure. Figure 1 As can be seen, the gas sensor 100 includes a sensing electrode module 300 and a resistor 200, wherein the resistor 200 is electrically connected to the sensing electrode module 300. The sensing electrode module 300 includes a bottom layer 310, a plurality of sensing electrodes 320, and a sensing layer 330, wherein the sensing electrodes 320 are disposed on one side of the bottom layer 310, the sensing layer 330 covers the sensing electrodes 320, and the sensing layer 330 includes a transition metal diselenide material (not shown in the figure). Specifically, during gas sensing with the gas sensor 100, the resistor 200 is used to measure the resistance value of the sensing electrode module 300, thereby observing the resistance change of the sensing electrode module 300. Furthermore, the spacing between the sensing electrodes 320 can be from 200 μm to 600 μm. Furthermore, the sensing electrode 320 is composed of a chromium metal layer and a noble metal layer. One surface of the chromium metal layer is connected to the underlying layer 310, and the other surface of the chromium metal layer is in contact with one surface of the noble metal layer, which is covered by the sensing layer 330. Additionally, the thickness of the chromium metal layer can be from 1 nm to 10 nm, and the thickness of the noble metal layer can be from 10 nm to 100 nm. This increases the sensing current of the gas sensor 100 and enhances the durability of the sensing electrode 320.

[0051] The thickness of the transition metal diselenide material can be from 1.2 nm to 45 nm. This improves the charge transfer capability of the transition metal diselenide material, thereby increasing the sensing sensitivity of the gas sensor 100. Furthermore, the transition metal diselenide material can have a single-crystal phase or a polycrystalline phase. This improves the selectivity of the gas sensor 100.

[0052] The transition metal diselenide material comprises a transition metal layer and a selenium atom layer. The transition metal layer may include a transition metal source, and the selenium atom layer may be covalently bonded to one side of the transition metal layer. Specifically, the transition metal source may be molybdenum, tungsten, tin, or platinum. This contributes to the bonding stability of the covalently bonded selenium atom layer to the transition metal layer, which is beneficial to the durability and reliability of the gas sensor 100.

[0053] Furthermore, the transition metal source for transition metal diselenide materials can be molybdenum, tungsten, tin, or platinum. Molybdenum, tungsten, tin, or platinum are transition metal elements, and the properties of overplated metals fall between alkali metals, alkaline earth metals, and nonmetals. Most of these metals possess unfilled valence shell d-orbitals, which contributes to the bonding stability of the transition metal diselenide materials. Moreover, diselenides of molybdenum, tungsten, tin, or platinum exhibit high environmental tolerance and high selectivity for the sensed gas, which is beneficial for improving the sensing performance of the gas sensor 100.

[0054] Please refer to Figure 2 and Figure 3 , Figure 2 This is a flowchart illustrating the steps of a plasma-assisted deposition method 400 for preparing a transition metal diselenide material 420 in a gas sensor 100 according to one embodiment of the present disclosure. Figure 3 It is a drawing according to Figure 2 A schematic diagram of the plasma-assisted process system 410 used in the plasma-assisted deposition method 400. (From...) Figure 2 and Figure 3 It can be seen that the plasma-assisted deposition method 400 includes steps 401, 402 and 403.

[0055] Step 401 involves heating a selenium solid 419 to form a selenium gas (not shown) at a temperature of 150°C to 300°C. Specifically, the selenium solid 419 is heated in a first space 412, and the heating temperature of the first space 412 is controlled within the range of 150°C to 300°C, thereby allowing the selenium solid 419 to be stably converted into selenium gas. Preferably, the heating temperature can be 200°C to 300°C. This improves the conversion efficiency of the selenium solid 419 into selenium gas.

[0056] Step 402 involves introducing a reactive gas 418 at a plasma operating power to assist the formation of a selenium plasma 415 from the selenium gas. The reactive gas 418 contains nitrogen, hydrogen, or a combination thereof, and the plasma operating power is greater than 0 W and less than or equal to 500 W. Specifically, the reactive gas 418 enters the first space 412 through the gas inlet 411, mixes with the selenium gas, and then flows out through the gas outlet 413 into the second space 414. There, the selenium plasma 415 is formed at the external inductively coupled plasma (ICP) coil 416 corresponding to the second space 414. Further, the volume ratio of nitrogen to hydrogen in the reactive gas 418 can be 0:1, 1:3, 1:1, 3:1, 2:1, or 1:0. This facilitates the generation of the selenium plasma 415. Alternatively, the volume ratio of nitrogen to hydrogen in the reactive gas 418 can be 1:1, 3:1, or 2:1. This improves the generation efficiency of selenium plasma 415. Specifically, the hydrogen gas in the reactant gas 418, under the action of the inductively coupled plasma coil 416, reacts with the selenium gas to generate selenium plasma 415, which can be represented as H₂Se, where H represents hydrogen atoms and Se represents selenium atoms. Furthermore, the selenium plasma 415 can dissociate to form the highly reactive precursor H₂Se. + This is beneficial for increasing the reaction rate.

[0057] Furthermore, the flow rate of the reactant gas 418 can be from 1 standard cubic centimeter per minute (sccm) to 500 sccm per minute. This helps to improve the uniformity of mixing between the reactant gas 418 and the selenium gas. Preferably, the flow rate of the reactant gas 418 can be from 100 sccm per minute to 500 sccm per minute. This can improve the generation efficiency of the selenium plasma 415.

[0058] Step 403 involves providing a substrate 417 comprising a substrate (not shown) and a plating layer (not shown). The plating layer is disposed on a surface of the substrate, and the plating layer is deposited corresponding to selenium plasma 415 at a reaction temperature and a reaction pressure to form a transition metal diselenide material 420. The thickness of the plating layer is 1 nm to 40 nm, and the plating layer contains a transition metal source, thereby forming the transition metal diselenide material 420 after the reaction between the selenium plasma 415 and the plating layer. Specifically, the precursor H2Se formed by the dissociation of selenium plasma 415... +A chemical reaction occurs between the coating and the metal, forming chemical bonds and thus creating a transition metal diselenide material 420. A coating thickness in the range of 1 nm to 40 nm is beneficial for the formation efficiency of the transition metal diselenide material 420. Preferably, the coating thickness can be 1 nm to 20 nm, thereby thinning the transition metal diselenide material 420 and increasing its charge transfer capability. Furthermore, the transition metal source of the coating can be molybdenum, tungsten, tin, or platinum. This increases the bond stability between the transition metal and selenium, contributing to improved sensing stability of the gas sensor 100.

[0059] Furthermore, the reaction temperature can be from 100°C to 550°C, and the reaction pressure can be from 0.01 Torr to 760 Torr. This can improve the yield of the transition metal diselenide material 420. Preferably, the reaction temperature can be from 250°C to 550°C, which can improve the crystal structure of the transition metal diselenide material 420, thus enhancing its chemical corrosion resistance and facilitating its deposition on a low-melting-point substrate. This can improve the corrosion resistance of the gas sensor 100.

[0060] Specifically, the substrate material can be polyimide (PI), glass, silicon nitride, stainless steel, silicon dioxide, aluminum oxide, or hafnium oxide. This increases the application versatility of the transition metal diselenide material 420. For example, when the substrate is polyimide, it facilitates the application of the transition metal diselenide material 420 on flexible circuit boards.

[0061] The following specific embodiments further illustrate this disclosure, so as to enable those skilled in the art to fully utilize and practice this disclosure without excessive interpretation, and these embodiments should not be regarded as limiting the scope of this disclosure, but are used to illustrate how to implement the materials and methods of this disclosure.

[0062] <Transition Metal Diselenide Materials>

[0063] Example 1: The transition metal diselenide material of Example 1 (hereinafter referred to as Example 1) was prepared by the aforementioned plasma-assisted deposition method, wherein the heating temperature was 150°C to 300°C, the plasma operating power was greater than 0W and less than or equal to 500W, the reaction temperature was 100°C to 550°C, the reaction pressure was 0.01 Torr to 760 Torr, the volume ratio of nitrogen to hydrogen in the reaction gas was 3:1, the substrate was silicon dioxide, the coating was tin(IV) oxide, and the thickness of the tin dioxide layer was 1 nm to 40 nm.

[0064] The transition metal diselenide material of Experiment 2 (hereinafter referred to as Experiment 2), the transition metal diselenide material of Experiment 3 (hereinafter referred to as Experiment 3), and the transition metal diselenide material of Experiment 4 (hereinafter referred to as Experiment 4) were prepared using a similar preparation method as Experiment 1, the difference being the volume ratio of nitrogen to hydrogen in the reaction gas.

[0065] The transition metal diselenide materials of Experimental Example 5 (hereinafter referred to as Experimental Example 5), Experimental Example 6 (hereinafter referred to as Experimental Example 6), Experimental Example 7 (hereinafter referred to as Experimental Example 7), Experimental Example 8 (hereinafter referred to as Experimental Example 8), and Experimental Example 9 (hereinafter referred to as Experimental Example 9) were prepared using a similar method to Experimental Example 1, the difference being the volume ratio of nitrogen to hydrogen in the coating and the reaction gas. The coatings of Experimental Examples 5 to 8 were all molybdenum (VI) oxide layers, and the thickness of the coatings ranged from 1 nm to 40 nm. The coating of Experimental Example 9 was a platinum metal layer, and the thickness of the coating was 1.2 nm.

[0066] The volume ratio of nitrogen to hydrogen in the coating and reaction gases of Experiments 1 to 9 is shown in Table 1.

[0067]

[0068]

[0069] <Crystal Structure of Transition Metal Diselenide Materials>

[0070] This experiment used an X-ray diffractometer (XRD) to analyze the transition metal diselenide materials in the aforementioned Experiments 1 to 4 to determine the crystal structure of the transition metal diselenide materials. The XRD scanning speed was 2° per minute, the scanning range was between 10° and 50°, and the scanning step was 0.05°.

[0071] Please refer to Figures 4A to 4C , Figure 4AThe XRD patterns are for Experiment 1, Experiment 2, Experiment 3, and Experiment 4. Figure 4B The XRD pattern of Experiment Example 7 is shown. Figure 4C This is the XRD pattern of Experiment Example 9. Figures 4A to 4C It can be seen that in Experiments 1, 2, 3, and 4, tin diselenide signals from transition metal diselenide materials appear at 2θ = 13.5°; in Experiment 7, molybdenum diselenide signals from transition metal diselenide materials appear at 2θ = 13.5°, 27.5°, 31.5°, 38°, 47.5°, and 56°; and in Experiment 9, platinum diselenide signals from transition metal diselenide materials appear at 2θ = 17.5°. This demonstrates that transition metal diselenide materials can be prepared by plasma-assisted deposition.

[0072] <Gas sensor sensing results>

[0073] A gas sensor includes a sensing electrode module and a resistor, wherein the resistor is electrically connected to the sensing electrode module. The sensing electrode module includes a bottom layer, a plurality of sensing electrodes, and a sensing layer, wherein the sensing electrodes are disposed on one side of the bottom layer, the sensing layer covers the sensing electrodes, and the sensing layer comprises the transition metal diselenide material of the aforementioned experimental example. Further, the thickness of the transition metal diselenide material can be from 1.2 nm to 45 nm. The gas sensors of Examples 1 to 9 (hereinafter referred to as Examples 1 to 9) and the transition metal diselenide materials of their sensing layers are shown in Table 2.

[0074]

[0075]

[0076] Please refer to Figure 5 and Figure 6 , Figure 5 The graph shows the real-time sensing response results of Examples 1, 2, 3, and 4 for nitrogen dioxide concentrations ranging from 1 ppm to 25 ppm. Figure 6 The graph shows the sensing linearity of different concentrations of nitrogen dioxide for Examples 1, 2, 3, and 4. The sensing response can be obtained by the following formula:

[0077]

[0078] Among them, R air R is the resistance value in pure air. gas It is the resistance value of the sensed gas.

[0079] Depend on Figure 5 and Figure 6It is evident that the response of the gas sensors in Examples 1, 2, 3, and 4 increases with increasing nitrogen dioxide concentration. The R-squared of the linear regression was calculated using the response data to evaluate the sensing linearity. The R-squared values ​​for the gas sensors in Examples 1, 2, 3, and 4 are 0.922, 0.983, 0.980, and 0.972, respectively. This demonstrates that the gas sensor disclosed herein can be used to sense nitrogen dioxide and exhibits good sensing linearity. Specifically, Example 1 shows the strongest response, indicating that the presence of nitrogen in the reaction gas of the plasma-assisted deposition method helps to improve the sensing signal intensity and sensitivity of transition metal diselenide materials applied to gas sensors.

[0080] Please refer to Figure 7 The image shows the sensing response results of Example 1. Specifically, the coating in Example 1 is a tin dioxide layer with a thickness ranging from 1 nm to 40 nm. By applying Example 1 with different tin dioxide layer thicknesses to a gas sensor, the gas sensor of Example 1 can be obtained. Figure 7 It can be seen that Example 1 exhibits a response under different tin dioxide layer thicknesses. Furthermore, when the tin dioxide layer thickness is less than or equal to 20 nm, the response intensity is greater, which is beneficial for increasing the sensing sensitivity of the gas sensor.

[0081] Please refer to Figure 8 This is a graph showing the sensing selectivity results for Examples 5, 6, 7, and 8. (From...) Figure 8 It can be seen that in Examples 5, 6, 7, and 8, 25 ppm of nitrogen dioxide and 25 ppm of ammonia gas were sensed respectively, and a sensing response was observed in all cases. This proves that Examples 5, 6, 7, and 8 of this disclosure can be used to sense nitrogen dioxide and ammonia gas. The ratio of the ammonia response to nitrogen dioxide is a selective factor; a higher selective factor indicates higher selectivity for sensing ammonia gas. Examples 5, 6, and 7 of this disclosure have high selectivity for sensing ammonia gas.

[0082] Please refer to Figure 9 This is a graph showing the sensing response results of different gases in Example 9. Figure 9It is evident that Example 9 exhibits a sensing response to nitrogen dioxide, acetone (ACE), ammonia, hydrogen sulfide, carbon monoxide, sulfur dioxide, and formaldehyde. This demonstrates that Example 9 of this disclosure can be used to sense nitrogen dioxide, acetone, ammonia, hydrogen sulfide, carbon monoxide, sulfur dioxide, and formaldehyde. Example 9 shows a high response to ammonia and hydrogen sulfide, thus demonstrating high selectivity for sensing these substances.

[0083] In summary, the sensing layer of the gas sensor disclosed herein comprises a transition metal diselenide material, which can be fabricated via plasma-assisted deposition. Large-area transition metal diselenide material can be generated using a plasma-assisted process system. By controlling the structure and composition of the transition metal diselenide material, it exhibits high selectivity for specific gas molecules and can be applied to the sensing of corrosive gases, such as hydrogen sulfide, ammonia, or sulfur dioxide. Therefore, the performance of the gas sensor disclosed herein is less affected by corrosive gases in harsh environments and possesses advantages such as high sensitivity, high selectivity, reproducibility, and low power consumption. Furthermore, the transition metal diselenide material fabricated by plasma-assisted deposition enables efficient and precise manufacturing processes, allowing for the production of large-area transition metal diselenide materials that meet industrial requirements, while also ensuring the quality of the transition metal diselenide material.

[0084] Although this disclosure has been presented above with reference to embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make various changes and modifications without departing from the concept and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the claims.

Claims

1. A gas sensor, characterized in that, Include: A sensing electrode module, comprising: One bottom layer; Multiple sensing electrodes are disposed on one side of the underlying layer; and A sensing layer covering the plurality of sensing electrodes, and the sensing layer comprising a transition metal diselenide material; and A ohmmeter is electrically connected to the sensing electrode module.

2. The gas sensor as described in claim 1, characterized in that, The thickness of this transition metal diselenide material ranges from 1.2 nm to 45 nm.

3. The gas sensor as described in claim 1, characterized in that, This transition metal diselenide material has a single crystal phase or a polycrystalline phase.

4. The gas sensor as described in claim 1, characterized in that, This transition metal diselenide material contains: A transition metal layer, comprising a transition metal source; and A selenium atom layer, covalently bonded to one side of the transition metal layer.

5. The gas sensor as described in claim 4, characterized in that, The transition metal source for this transition metal diselenide material is molybdenum, tungsten, tin, or platinum.

6. The gas sensor as described in claim 1, characterized in that, The transition metal diselenide material was prepared by a plasma-assisted deposition method.

7. The gas sensor as described in claim 6, characterized in that, This plasma-assisted deposition method includes: A solid selenium element is heated at a heating temperature of 150°C to 300°C to form a selenium element gas. A reactive gas is introduced at a plasma operating power to assist the selenium gas in forming a selenium plasma, wherein the reactive gas contains nitrogen, hydrogen, or a combination thereof, and the plasma operating power is greater than 0 W and less than or equal to 500 W; and A substrate is provided, comprising a substrate and a coating, the coating being disposed on a surface of the substrate and disposed corresponding to a selenium plasma, and deposited at a reaction temperature and a reaction pressure to form a transition metal diselenide material, wherein the thickness of the coating is 1 nm to 40 nm, and the coating comprises a transition metal source.

8. The gas sensor as described in claim 7, characterized in that, The volume ratio of nitrogen to hydrogen in the reaction gas is 0:1, 1:3, 1:1, 3:1, 2:1, or 1:

0.

9. The gas sensor as described in claim 8, characterized in that, The volume ratio of nitrogen to hydrogen in the reaction gas is 1:1, 3:1, or 2:

1.

10. The gas sensor as claimed in claim 7, characterized in that, The reaction temperature ranges from 100°C to 550°C.

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