A UV-enhanced room-temperature ethanol gas sensor

Abstract

The present invention relates to the field of ethanol sensing technology, and more specifically, to a UV-enhanced room-temperature ethanol gas sensor. The sensor comprises a substrate, an interdigitated electrode layer, a gas-sensitive material layer, and a precious metal particle layer. The interdigitated electrode layer is disposed on the substrate and includes a plurality of mutually parallel and separated interdigitated fingers. The gas-sensitive material layer is disposed between the interdigitated fingers and the substrate, and the precious metal particle layer is disposed on the gas-sensitive material layer. The sensor forms a resonant cavity between the precious metal particle layer and the interdigitated fingers, confining excitation light within the gas-sensitive material layer. This creates a strong electric field both on the surface of the gas-sensitive material layer and within the gas-sensitive material layer, thereby enhancing gas detection sensitivity. The sensor has promising application prospects in the field of ethanol gas sensing.

Description

Technical Field

[0001] The invention relates to the technical field of ethanol sensing, and in particular to an ultraviolet-enhanced room-temperature ethanol gas sensor. Background Art

[0002] Semiconductor gas sensors have attracted widespread attention due to their advantages, including high sensitivity, high spatial resolution, and fast response speed. However, when ethanol gas reacts with oxygen anions on the semiconductor surface, it produces water, which hinders the release of active sites. Researchers have installed a heating device outside the interdigitated electrodes to remove water molecules from the semiconductor surface. The heating device also increases the adsorption of oxygen molecules onto the semiconductor material. However, semiconductor gas sensors operating at high temperatures suffer from numerous drawbacks, including low operational safety and high energy consumption.

[0003] In recent years, researchers have tried various methods to achieve gas sensing at room temperature, such as surface functionalization of gas-sensitive materials [Room temperature gas nanosensors based on individual and multiple networked Au-modified ZnO nanowires, Sensors and Actuators B-Chemical, Vol. 299, pp. 126977, 2019], piezoelectric [Portable room-temperature self-powered / active H2 sensor driven by human motion through piezoelectric screening effect,. Nano Energy, 2014, Vol. 8, pp. 34, 2014], triboelectrostatic effect [Ultrasensitive flexible self-powered ammonia sensor based on triboelectricnanogenerator at room temperature, Nano Energy, Vol. 51, pp. 231, 2018], and photoexcitation [The Response of UV / Blue Light and Ozone Sensing Using Ag-TiO2 Planar Nanocomposite Thin Film]. Film, Sensors, Vol. 19, pp. 5061, 2019] and other methods have replaced high-temperature conditions. Among these methods, light excitation has the advantage of being easy to use, and LED light sources are mature technology and can be directly applied. However, semiconductor materials often have weak absorption of light and cannot fully utilize the excitation light. As a result, the gas sensitivity of most light-excited semiconductor gas sensors at room temperature is lower than that at high temperatures, limiting the application of light-excited room-temperature semiconductor gas sensors. Summary of the Invention

[0004] In order to solve the above problems, that is, to improve the application of excitation light, the present invention provides a UV-enhanced room-temperature ethanol gas sensor, comprising a substrate, an interdigitated electrode layer, a gas-sensitive material layer, and a precious metal particle layer. The interdigitated electrode layer is placed on the substrate, and the interdigitated electrode layer includes a plurality of mutually parallel and separated interdigitated fingers. The gas-sensitive material layer is placed on the interdigitated fingers and the substrate, and the precious metal particle layer is placed on the gas-sensitive material layer.

[0005] The core concept of the present invention is to form a resonant cavity between the noble metal particle layer and the interdigitated fingers, confining the excitation light within the gas-sensitive material layer and forming a strong electric field on the surface of the gas-sensitive material layer. On the one hand, this increases the activity of oxygen molecules, and on the other hand, it facilitates the desorption of water molecules from the gas-sensitive material, thereby improving the sensitivity of gas detection.

[0006] Furthermore, the gas-sensitive material layer is iron molybdate.

[0007] Furthermore, the noble metal particle layer is composed of dispersed noble metal particles.

[0008] Furthermore, the material of the noble metal particles is gold.

[0009] Furthermore, the size of the noble metal particles is greater than 5 nanometers and less than 20 nanometers.

[0010] Furthermore, the material of the interdigital fingers is gold.

[0011] Furthermore, the material of the substrate is aluminum oxide.

[0012] Furthermore, the surface of the substrate is provided with parallel grooves, the interdigitated fingers are arranged in the grooves, and the upper surfaces of the interdigitated fingers are flush with the upper surface of the substrate.

[0013] Furthermore, the interdigitals are prepared by coating and polishing methods.

[0014] Furthermore, an ultraviolet reflective layer is provided on the bottom surface of the substrate.

[0015] Beneficial effects of the present invention:

[0016] (1) The present invention forms a resonant cavity between the noble metal particle layer and the interdigitated fingers, and the excitation light is confined within the gas-sensitive material layer. A strong electric field is formed on the surface and inside the gas-sensitive material layer, thereby improving the sensitivity of gas detection.

[0017] (2) The present invention embeds the interdigitated fingers in the substrate, and the required gas-sensitive material layer is relatively thin. When gas is detected, the main thing that changes is the resistance of the surface of the gas-sensitive material layer, which further improves the sensitivity of gas detection.

[0018] (3) The present invention provides a reflective layer on the bottom surface of the substrate, which makes fuller use of the excitation light, helps to enhance the electric field on the surface of the gas-sensitive material layer, and improves the sensitivity of gas detection.

[0019] Based on the above effects, the present invention has good application prospects in the field of ethanol sensing technology.

[0020] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1Schematic diagram of a UV-enhanced room-temperature ethanol gas sensor.

[0022] Figure 2 It is a schematic diagram of the interdigitated fingers, gas-sensitive material layer, and precious metal particles.

[0023] Figure 3 It is a schematic diagram of the equivalent resistance of the surface and bottom layers of the gas-sensitive material layer.

[0024] Figure 4 This is a schematic diagram of another UV-enhanced room-temperature ethanol gas sensor.

[0025] In the figure: 1, substrate; 2, interdigitated electrode layer; 3, gas-sensitive material layer; 4, precious metal particle layer; 21, interdigitated; 41, precious metal particles. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of this application more clear, the application is further described in detail below with reference to the accompanying drawings and examples.

[0027] The present invention provides a UV-enhanced room temperature ethanol gas sensor, such as Figure 1 As shown, it includes a substrate 1, an interdigitated electrode layer 2, a gas-sensitive material layer 3, and a precious metal particle layer 4. The substrate 1 is made of aluminum oxide, and the thickness of the substrate 1 is greater than 0.5 mm and less than 1 mm; the interdigitated electrode layer 2 includes a plurality of mutually parallel and separated interdigits 21, and the material of the interdigits 21 is gold; the material of the gas-sensitive material layer 3 is iron molybdate nanostructures; Figure 2 As shown, the precious metal particle layer 4 is composed of dispersed precious metal particles 41. The precious metal particles 41 are made of gold and have a size greater than 5 nanometers and less than 20 nanometers. The interdigitated electrode layer 21 is disposed on the substrate 1. The gas-sensitive material layer 3 is disposed on the interdigitated electrodes 21 and the substrate 1. The gas-sensitive material layer 3 covers the interdigitated electrodes 21 and the exposed portions of the substrate 1. The precious metal particle layer 4 is disposed on the gas-sensitive material layer 3.

[0028] During application, under the irradiation of ultraviolet light, the resistance Ra of the gas-sensitive material layer 3 is first measured in an oxygen or air environment; then ethanol gas is introduced and the resistance Rg of the gas-sensitive material layer 3 in the ethanol gas environment is measured. The sensitivity S of ethanol gas detection is S=Ra / Rg.

[0029] The core concept of the present invention is to form a resonant cavity between the precious metal particle layer 4 and the interdigital fingers 21, thereby confining the excitation light within the gas-sensitive material layer 3 and forming a strong electric field on the surface of the gas-sensitive material layer 3. In addition, the activity of oxygen molecules is increased, which is beneficial to the desorption of water molecules from the gas-sensitive material, thereby improving the sensitivity of gas detection.

[0030] The gas-sensitive material layer 3 is arranged on the interdigital electrode layer 2 and the substrate 1 by screen printing. The thickness of the gas-sensitive material layer 3 is less than 10 microns. The thinner gas-sensitive material layer 3 is used so that the resistance of the entire gas-sensitive material layer 3 changes more relatively, so as to improve the sensitivity of ethanol gas sensing. The process of arranging the gas-sensitive material on the interdigital electrode layer 2 and the substrate 1 includes the following steps: (1) placing the iron molybdate nanostructured powder into an agate mortar for grinding. The grinding process includes preliminary grinding and deep grinding. The preliminary grinding is performed using a grinding rod. During the deep grinding, an appropriate amount of pine oil is added for wet grinding until it becomes viscous. In this step, by changing the amount of pine oil, the viscosity of the sample after grinding is adjusted, and the thickness of the gas-sensitive material layer 3 obtained is further controlled; (2) using a screen printing plate to print the obtained paste onto the interdigital electrode layer 2, and the paste is evenly coated on the test area; ( 3) Place the printed sample in a baking machine, set the temperature to 320 degrees Celsius, and bake for 2 hours, so that the organic solvent in the sample is fully volatilized, and only the iron molybdate nanostructure remains in the test area, and the iron molybdate nanostructure is in good contact with the fork finger 21; (4) Aging the obtained device at 400 degrees Celsius for 12 hours to improve the density of the gas-sensitive material layer 3, thereby improving the stability of the gas sensor. In this step, after the gas-sensitive material layer 3 is aged, the surface of the gas-sensitive material layer 3 tends to be flat, and the ultraviolet light of a specific band can be better confined to the resonant cavity formed by the precious metal particle layer 4 and the fork finger 21.

[0031] The method for preparing gold particles on the gas-sensitive material layer 3 adopts the method of adding gold sol, and the specific steps include: (1) placing the prepared device (including the substrate 1, the interdigitated electrode layer 2, and the gas-sensitive material layer 3) on a heating table and heating it, maintaining the temperature at 60 degrees Celsius for 30 minutes; (2) using a pipette to drop the gold sol on the iron molybdate nanostructure; (3) raising the temperature of the heating table to 80 degrees Celsius and maintaining it for 1 hour to remove the moisture in the gold sol; (4) calcining the obtained device again at 400 degrees Celsius for 12 hours so that the gold particles and the iron molybdate nanostructure are tightly combined to form a heterojunction.

[0032] In the present invention, the Fermi level of the iron molybdate nanostructure is lower than that of the gold nanoparticles. Free electrons flow from the gold particles to the iron molybdate until the Fermi levels of the iron molybdate and gold particles reach equilibrium, forming a potential barrier at the interface between the gold particles and the iron molybdate. Under ultraviolet light irradiation, the local electromagnetic field around the gold particles is enhanced, as is the electromagnetic field within the gas-sensitive material layer 3. This intensifies the generation and separation of photoexcited carriers on the surface of the iron molybdate nanostructure, significantly increasing the electron density in the iron molybdate conduction band. In oxygen or air, oxygen anions are adsorbed on the surface of the gas-sensitive material layer 3, increasing the resistance of the gas-sensitive material layer 3. In ethanol gas, the ethanol gas reacts with the oxygen anions to release electrons, reducing the resistance of the gas-sensitive material layer 3. The localized surface plasmon resonance of the gold particles and the electromagnetic field resonance within the gas-sensitive material layer 3 accelerate the surface adsorption and desorption of ethanol gas, improving the response of the gas sensor. Furthermore, in an oxygen or air environment, the holes generated by ultraviolet light irradiation effectively clean the surface of the photosensitive material layer 3, increasing active sites.

[0033] In the present invention, under ultraviolet light irradiation, the separation of electrons and holes in the iron molybdate nanostructure is intensified, thereby increasing the resistance change of the gas-sensitive material layer 3 in oxygen (or air) and ethanol gas, thereby improving the sensitivity of ethanol gas detection.

[0034] When the gas-sensitive material layer 3 is placed in oxygen (or air) and ethanol gas, the area where the carrier concentration in the gas-sensitive material layer 3 changes significantly only occurs in the surface layer of the gas-sensitive material layer 3 that is in contact with oxygen (or air) and ethanol gas, and the resistance (r) of the surface layer of the gas-sensitive material layer 3 changes significantly; the carrier concentration in the bottom layer of the gas-sensitive material layer 3 changes slightly, and the resistance (R) of the bottom layer of the gas-sensitive material layer 3 changes slightly. For example, in Figure 1 In the horizontal direction, the carrier concentration of the bottom layer of the gas-sensitive material layer 3 between adjacent interdigits 21 changes little, or in other words, the resistance (R) changes little. The total resistance between adjacent interdigits 21 is the parallel connection between the resistance of the surface layer of the gas-sensitive material layer 3 and the resistance of the bottom layer of the gas-sensitive material layer 3, such as Figure 3 If the adjacent interdigits 21 measure only the resistance change of the surface layer (r) of the gas-sensitive material layer 3, this will cause a larger change in resistance in oxygen (or air) and ethanol gas, thereby improving the sensitivity of ethanol gas detection.

[0035] Based on the above considerations, preferably, the surface of substrate 1 is provided with parallel grooves, with interdigits 21 positioned within the grooves, and the upper surfaces of interdigits 21 flush with the upper surface of substrate 1. This allows a relatively thin layer of gas-sensitive material 3 to be applied to cover interdigits 21. In the presence of oxygen (or air) and ethanol gases, the carrier concentration and resistance of the entire gas-sensitive material layer 3 vary significantly, thereby enhancing the sensitivity of ethanol gas detection.

[0036] The method of etching, coating and polishing is used to prepare interdigitated electrodes flush with the surface of the substrate 1. The specific steps include: (1) polishing the substrate 1 so that the substrate 1 has a smooth surface; (2) using electron beam particles or chemical etching to prepare grooves on the surface of the substrate 1; (3) using physical vapor deposition to plate gold on the grooves and the surface of the substrate 1; (4) polishing the surface of the substrate 1 until the gold film on the surface of the substrate 1 is polished away and only the gold in the grooves remains, thereby forming interdigitated electrodes flush with the surface of the substrate 1.

[0037] Preferably, an ultraviolet reflective layer is provided on the bottom surface of the substrate 1. The material of the ultraviolet reflective layer is fused quartz or calcium fluoride, which is used to reflect ultraviolet light incident from the surface, forming a stronger electromagnetic field in the gas-sensitive material layer 3 and at the gold particles, thereby intensifying the separation of electrons and holes in the gas-sensitive material layer 3 and improving the sensitivity of ethanol gas detection.

[0038] In summary, the present invention provides a UV-enhanced room-temperature ethanol gas sensor comprising a substrate 1, an interdigital electrode layer 2, a gas-sensitive material layer 3, and a precious metal particle layer 4. The interdigital electrode layer 2 is disposed on the substrate 1 and includes a plurality of mutually parallel and separated interdigital fingers 21. The gas-sensitive material layer 3 is disposed on the interdigital fingers 21 and the substrate 1, and the precious metal particle layer 4 is disposed on the gas-sensitive material layer 3. The present invention forms a resonant cavity between the precious metal particle layer 4 and the interdigital fingers 21, confining the excitation light within the gas-sensitive material layer 3. This creates a strong electric field both on the surface of the gas-sensitive material layer 3 and within the gas-sensitive material layer 3, thereby enhancing the sensitivity of gas detection. The sensor has promising application prospects in the field of ethanol gas sensing.

[0039] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A UV-enhanced room temperature ethanol gas sensor, characterized in that: It includes a substrate, an interdigitated electrode layer, a gas-sensitive material layer, and a precious metal particle layer, wherein the interdigitated electrode layer is placed on the substrate, the interdigitated electrode layer includes a plurality of mutually parallel and separated interdigitated fingers, the gas-sensitive material layer is placed on the interdigitated fingers and the substrate, and the precious metal particle layer is placed on the gas-sensitive material layer, wherein the precious metal particle layer is composed of dispersed precious metal particles, the surface of the substrate is provided with parallel grooves, the interdigitated fingers are arranged in the grooves, and the upper surface of the interdigitated fingers is flush with the upper surface of the substrate.

2. The UV-enhanced room-temperature ethanol gas sensor according to claim 1, wherein: The gas-sensitive material layer is iron molybdate.

3. The UV-enhanced room-temperature ethanol gas sensor according to claim 1, wherein: The material of the noble metal particles is gold.

4. The UV-enhanced room-temperature ethanol gas sensor according to claim 3, wherein: The size of the noble metal particles is greater than 5 nanometers and less than 20 nanometers.

5. The UV-enhanced room-temperature ethanol gas sensor according to claim 1, wherein: The material of the interdigitated fingers is gold.

6. The UV-enhanced room-temperature ethanol gas sensor according to claim 1, wherein: The material of the substrate is aluminum oxide.

7. The UV-enhanced room-temperature ethanol gas sensor according to claim 1, wherein: The interdigital fingers are prepared by coating and polishing methods.

8. The UV-enhanced room-temperature ethanol gas sensor according to claim 1, wherein: The bottom surface of the substrate is provided with an ultraviolet reflecting layer.

Images