CN116256400A - A UV-enhanced room temperature ethanol gas sensor - Google Patents

Abstract

The invention relates to the technical field of ethanol sensing, in particular to an ultraviolet enhanced room temperature ethanol gas sensor, which comprises a substrate, an interdigital electrode layer, a gas-sensitive material layer and a noble metal particle layer, wherein the interdigital electrode layer is arranged on the substrate and comprises a plurality of mutually parallel and separated interdigital fingers, the gas-sensitive material layer is arranged on the interdigital fingers and the substrate, and the noble metal particle layer is arranged on the gas-sensitive material layer. According to the invention, the resonant cavity is formed between the noble metal particle layer and the interdigital, the excitation light is limited in the gas-sensitive material layer, a strong electric field is formed on the surface of the gas-sensitive material layer and in the gas-sensitive material layer, the sensitivity of gas detection is improved, and the invention has good application prospect in the field of ethanol gas sensing.

Description

A UV-enhanced room temperature ethanol gas sensor

technical field

The invention relates to the technical field of ethanol sensing, in particular to an ultraviolet-enhanced room temperature ethanol gas sensor.

Background technique

Semiconductor gas sensors have the advantages of good sensitivity, high spatial resolution, and fast response, and have received extensive attention. For ethanol gas, when ethanol gas reacts with oxygen anions on the semiconductor surface, water is generated, which is not conducive to the release of active sites. The researchers placed heating devices outside the interdigitated electrodes to remove water molecules from the surface of the semiconductor material. In addition, the heating device also increases the adsorption between the oxygen molecules and the semiconductor material. However, the semiconductor gas sensor under the condition of operation and high temperature has many disadvantages such as low operation safety and high energy consumption.

In recent years, researchers have tried a variety of methods to achieve gas sensing at room temperature, for example, researchers have functionalized the surface 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], using piezoelectric [Portable room-temperature self-powered/active H ₂ sensor driven by human motion through piezoelectricscreening effect,. Nano Energy, 2014, Vol.8, pp .34, 2014], using tribostatic effect [Ultrasensitive flexible self-powered ammonia sensor based ontriboelectric nanogenerator at room temperature, Nano Energy, Vol.51, pp.231, 2018], light excitation [The Response of UV/Blue Light and Ozone Sensing Using Ag-TiO2Planar Nanocomposite Thin Film, Sensors, Vol.19, pp.5061, 2019] and other methods have replaced high temperature conditions. Among these methods, the use of light excitation has the advantage of convenient application, and the LED light source has a mature technology for direct application. However, semiconductor materials tend to absorb light weakly and cannot make full use of the excitation light, resulting in the gas sensitivity of most light-excited semiconductor gas sensors at room temperature is higher than that at room temperature, which limits the sensitivity of light-excited semiconductor gas sensors at room temperature. Applications of gas sensors.

Contents of the invention

In order to solve the above problems, that is, to improve the application of excitation light, the present invention provides an ultraviolet-enhanced room temperature ethanol gas sensor, which includes a substrate, an interdigital electrode layer, a gas-sensitive material layer, and a noble metal particle layer. The interdigital electrode layer is placed on the On the substrate, the interdigital electrode layer includes a plurality of parallel and separated interdigital fingers, the gas-sensing material layer is placed on the interdigital fingers and the substrate, and the noble metal particle layer is placed on the gas-sensing material layer.

The core idea of the present invention is to form a resonant cavity between the noble metal particle layer and the fingers, confine the excitation light in the gas-sensitive material layer, and form a strong electric field on the surface of the gas-sensitive material layer, which increases the activity of oxygen molecules on the one hand, On the other hand, it is beneficial to the desorption of water molecules from the gas-sensitive material, thereby improving the sensitivity of gas detection.

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

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

Furthermore, the material of the noble metal particles is gold.

Furthermore, the size of the noble metal particles is larger than 5 nanometers and smaller than 20 nanometers.

Furthermore, the material of the fingers is gold.

Furthermore, the material of the substrate is alumina.

Furthermore, the surface of the base is provided with parallel grooves, the fingers are arranged in the grooves, and the upper surfaces of the fingers are flush with the upper surface of the base.

Furthermore, the fingers are prepared by coating and polishing.

Furthermore, the bottom surface of the substrate is provided with an ultraviolet reflective layer.

Beneficial effects of the present invention:

(1) The present invention forms a resonant cavity between the noble metal particle layer and the fingers, the excitation light is limited in the gas-sensitive material layer, and a strong electric field is formed on the surface of the gas-sensitive material layer and in the gas-sensitive material layer, which improves the gas Sensitivity of detection.

(2) The present invention embeds the fingers in the base, so the required gas-sensitive material layer is relatively thin, and when gas is detected, the resistance on the surface of the gas-sensitive material layer is mainly changed, which further improves the sensitivity of gas detection.

(3) The present invention arranges a light-reflecting layer on the bottom surface of the substrate, which makes full use of the excitation light, which is beneficial to enhance the electric field on the surface of the gas-sensitive material layer and improve the sensitivity of gas detection.

Based on the above effects, the present invention has a good application prospect in the technical field of ethanol sensing.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of drawings

Figure 1 is a schematic diagram of a UV-enhanced room temperature ethanol gas sensor.

Fig. 2 is a schematic diagram of an interdigitated finger, a gas-sensitive material layer, and noble metal particles.

Fig. 3 is a schematic diagram of the equivalent resistance of the surface layer and the bottom layer of the gas-sensitive material layer.

Fig. 4 is a schematic diagram of yet another ultraviolet-enhanced room temperature ethanol gas sensor.

In the figure: 1, substrate; 2, interdigitated electrode layer; 3, gas-sensitive material layer; 4, noble metal particle layer; 21, interdigitated fingers; 41, noble metal particles.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples.

The present invention provides an ultraviolet-enhanced room temperature ethanol gas sensor, as shown in FIG. The material of the substrate 1 is aluminum oxide, and the thickness of the substrate 1 is greater than 0.5 mm and less than 1 mm; the interdigital electrode layer 2 includes a plurality of mutually parallel and separated interdigital fingers 21, and the material of the interdigital fingers 21 is gold; the gas-sensitive material layer 3 The material is an iron molybdate nanostructure; as shown in Figure 2, the noble metal particle layer 4 is composed of dispersed noble metal particles 41, the material of the noble metal particles 41 is gold, and the size of the noble metal particles 41 is greater than 5 nanometers and less than 20 nanometers. The interdigital electrode layer 21 is placed on the substrate 1, the gas-sensitive material layer 3 is placed on the interdigital 21 and the substrate 1, the gas-sensitive material layer 3 covers the interdigital 21 and the substrate 1 exposed by the interdigital 21, and the noble metal particle layer 4 is placed on the gas-sensitive material layer 3.

During application, under the irradiation of ultraviolet light, first measure the resistance Ra of the gas-sensitive material layer 3 in an oxygen or air environment; The sensitivity S of gas detection is S=Ra/Rg.

The core idea of the present invention is to form a resonant cavity between the noble metal particle layer 4 and the fingers 21, confine the excitation light in the gas-sensitive material layer 3, and form a strong electric field on the surface of the gas-sensitive material layer 3, in addition, increase The activity of oxygen molecules is improved, which is conducive to the desorption of water molecules from the gas-sensitive material, thereby improving the sensitivity of gas detection.

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, and the thinner gas-sensitive material layer 3 is used so that the resistance of the entire gas-sensitive material layer 3 There are relatively more changes in order to improve the sensitivity of ethanol gas sensing. The process of disposing the gas-sensitive material on the interdigitated electrode layer 2 and the substrate 1 includes the following steps: (1) putting the iron molybdate nanostructure powder into an agate mortar for grinding, the grinding process includes preliminary grinding and deep grinding, The preliminary grinding is ground with a grinding rod. When grinding deeply, add an appropriate amount of terpineol for wet grinding until it is called viscous. In this step, by changing the amount of terpineol, the viscosity of the sample after grinding is adjusted. Further control the thickness of the finally obtained gas-sensitive material layer 3; (2) use a screen printing plate to print the obtained paste on the interdigitated electrode layer 2, and evenly coat the paste on the test area; (3) Put the printed sample into the glue baking machine, set the temperature at 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 molybdate The iron nanostructure is in good contact with the fingers 21; (4) the obtained device is aged at 400 degrees Celsius for 12 hours to improve the compactness of the gas sensitive material layer 3, thereby improving the stability of the gas sensor. In this step, the gas After the aging of the sensitive material layer 3 , the surface of the gas sensitive material layer 3 tends to be flat, and the ultraviolet light of a specific wavelength band can be better confined in the resonant cavity formed by the noble metal particle layer 4 and the fingers 21 .

The method for preparing gold particles on the gas-sensitive material layer 3 adopts the method of dropping gold sol, and the specific steps include: (1) placing the prepared device (including the substrate 1, the interdigital electrode layer 2, and the gas-sensitive material layer 3) Heating on the heating platform, the temperature maintained is 60 degrees Celsius, and the maintained time is 30 minutes; (2) the gold sol is added dropwise on the iron molybdate nanostructure with a pipette gun; (3) the temperature of the heating platform is increased to 80 Celsius, kept for 1 hour, so as 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 nanostructures are closely combined to form a heterojunction.

In the present invention, the Fermi energy level of the iron molybdate nanostructure is lower than the Fermi energy level of the gold nanoparticles, and free electrons flow from the gold particles to the iron molybdate until the Fermi energy levels of the iron molybdate and the gold particles reach equilibrium , a potential barrier is formed at the interface between the gold particles and the iron molybdate; under the irradiation of ultraviolet light, the local electromagnetic field around the gold particles is enhanced and the electromagnetic field in the gas-sensitive material layer 3 is also enhanced, aggravating the iron molybdate The generation and separation of photoexcited carriers on the nanostructured surface led to a significant increase in the electron density in the conduction band of iron molybdate. In oxygen or air, the surface of the gas-sensitive material layer 3 adsorbs oxygen negative ions, and the resistance of the gas-sensitive material layer 3 increases; in ethanol gas, ethanol gas reacts with oxygen negative ions to release electrons, and the resistance of the gas-sensitive material layer 3 decreases. The localized surface plasmon resonance of the gold particles and the electromagnetic field resonance in the gas-sensing material layer 3 accelerate the surface adsorption and desorption process of ethanol gas and improve the response value of the gas sensor. In addition, in an oxygen or air environment, holes generated under ultraviolet light irradiation can effectively clean the surface of the photosensitive material layer 3 and increase active sites.

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

When the gas-sensitive material layer 3 is placed in oxygen (or air) and ethanol gas, the region where the carrier concentration in the gas-sensitive material layer 3 changes greatly only occurs when the gas-sensitive material layer 3 is in contact with oxygen (or air) and ethanol gas. The surface layer that ethanol gas contacts, the resistance (r) of gas-sensitive material layer 3 top layer changes greatly; smaller. For example, in FIG. 1 , in the horizontal direction, the carrier concentration of the bottom layer of the gas-sensitive material layer 3 between adjacent interdigital fingers 21 changes little, or the resistance (R) changes little. The total resistance between adjacent fingers 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 , as shown in FIG. 3 . If only the resistance change of the gas-sensitive material layer 3 surface layer (r) is measured by the adjacent fingers 21, this will make the resistance change greatly in oxygen (or air) and ethanol gas, thereby improving the sensitivity of ethanol gas detection .

Based on the above considerations, preferably, the surface of the base 1 is provided with parallel grooves, the fingers 21 are disposed in the grooves, and the upper surface of the fingers 21 is flush with the upper surface of the base 1 . In this way, the gas-sensitive material layer 3 that needs to be coated is thin enough to cover the fingers 21 . In oxygen (or air) and ethanol gas, the carrier concentration of the entire gas-sensitive material layer 3 changes greatly, and the resistance also changes greatly, which improves the sensitivity of ethanol gas detection.

The method of etching, coating and polishing is used to prepare the 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) applying electron beam particles or chemical etching The method prepares the groove on the surface of the substrate 1; (3) applies the method of physical vapor deposition to plate gold on the surface of the groove and the substrate 1; (4) polishes the surface of the substrate 1 until the gold film on the surface of the substrate 1 is all polished Only the gold in the groove is left, forming interdigitated electrodes flush with the surface of the substrate 1 .

Preferably, the bottom surface of the substrate 1 is provided with an ultraviolet reflective layer, and the material of the ultraviolet reflective layer is fused silica or calcium fluoride, which is used to reflect the incident ultraviolet light from the surface and form a stronger The electromagnetic field intensifies the separation of electrons and holes in the gas-sensitive material layer 3 and improves the sensitivity of ethanol gas detection.

In summary, the present invention provides a UV-enhanced room temperature ethanol gas sensor, which includes a substrate 1, an interdigital electrode layer 2, a gas-sensitive material layer 3, and a noble metal particle layer 4. The interdigital electrode layer 2 is placed on the substrate 1, The interdigital electrode layer 2 includes a plurality of parallel and separated interdigital fingers 21 , the gas-sensing material layer 3 is placed on the interdigital fingers 21 and the substrate 1 , and the noble metal particle layer 4 is placed on the gas-sensing material layer 3 . In the present invention, a resonant cavity is formed between the noble metal particle layer 4 and the fingers 21, the excitation light is confined in the gas-sensitive material layer 3, a strong electric field is formed on the surface of the gas-sensitive material layer 3 and in the gas-sensitive material layer 3, and the improvement is improved. The sensitivity of gas detection is improved, and it has a good application prospect in the field of ethanol gas sensing.

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

Claims (10)

1. a kind of ultraviolet enhanced room temperature ethanol gas sensor is characterized in that, comprises substrate, interdigitated electrode layer, gas-sensitive material layer, precious metal particle layer, and described interdigitated electrode layer is placed on described substrate, and described interdigitated electrode layer The layer includes a plurality of mutually parallel and separated fingers, the gas-sensing material layer is placed on the fingers and the substrate, and the noble metal particle layer is placed on the gas-sensing material layer. 2. The ultraviolet-enhanced room temperature ethanol gas sensor according to claim 1, characterized in that: the gas-sensitive material layer is iron molybdate. 3. The ultraviolet-enhanced room temperature ethanol gas sensor according to claim 1, characterized in that: the noble metal particle layer is composed of dispersed noble metal particles. 4. The ultraviolet-enhanced room temperature ethanol gas sensor as claimed in claim 3, characterized in that: the material of the noble metal particles is gold. 5. The ultraviolet-enhanced room temperature ethanol gas sensor as claimed in claim 4, characterized in that: the size of the noble metal particles is greater than 5 nanometers and less than 20 nanometers. 6. The ultraviolet-enhanced room temperature ethanol gas sensor as claimed in claim 1, characterized in that: the material of the fingers is gold. 7. The ultraviolet-enhanced room temperature ethanol gas sensor according to claim 1, characterized in that: the material of the substrate is aluminum oxide. 8. The ultraviolet-enhanced room temperature ethanol gas sensor as claimed in claim 1, characterized in that: the surface of the base is provided with parallel grooves, the forked fingers are arranged in the grooves, and the upper surface of the forked fingers is in contact with The upper surface of the base is flush. 9. The ultraviolet-enhanced room temperature ethanol gas sensor as claimed in claim 8, characterized in that: the interdigitated fingers are prepared by coating and grinding. 10. The ultraviolet-enhanced room temperature ethanol gas sensor according to claim 1, characterized in that: the bottom surface of the substrate is provided with an ultraviolet reflective layer.

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