A fluorinated TiO2 gas sensor based on ultraviolet light band and a preparation method thereof

Abstract

The application belongs to the technical field of electronic components and elements, and provides a fluorinated TiO2 gas sensor based on ultraviolet light bands and a preparation method thereof.The fluorinated TiO2 gas sensor comprises a gas-sensitive material and an interdigital electrode plate, the gas-sensitive material is coated on the surface of the interdigital electrode plate, and the gas-sensitive material is composed of fluorinated titanium dioxide hollow microsphere material.The method has simple production process, and the obtained gas-sensitive material has high sensitivity to formaldehyde and fast response and recovery, and can be used in the field of formaldehyde gas sensors.Compared with existing traditional heating type gas sensor array technology, the application can make the sensor work at room temperature, reduce the aging problem of the sensitive material, improve the stability of the sensor, and thus obtain a novel gas-sensitive material with high sensitivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic components, and particularly relates to preparation of a fluorinated TiO2 gas sensor based on an ultraviolet light wave band and a detection method thereof. BACKGROUND

[0002] In recent years, qualitative and quantitative detection of toxic and harmful gases is becoming more and more important. Nowadays, analysis of these gases is usually carried out by using some test instruments with long test time and high cost, such as spectral analysis and chromatographic analysis. Semiconductor oxide gas sensors have attracted extensive attention due to many advantages, such as high sensitivity, small size and low manufacturing cost. In order to obtain excellent sensing performance, the sensor usually operates at a high temperature of 100-400 DEG C. However, this high temperature not only causes high power consumption but also may ignite flammable and explosive gases. In recent years, some studies show that, for example, irradiation of materials by ultraviolet light so as to reduce the working temperature of the materials is a very promising choice. Since Camagni (P. Camagni, G. Faglia, P. Galinetto, C. Perego, G. Samoggia, G. Sberveglieri, Photo-sensitivity activation of SnO2 thin film gas sensors at room temperature, Sensors and Actuators B: Chemical 31 (1996) 99-03.) et al. first reported the ultraviolet-enhanced semiconductor oxide sensor in 1996, many reports show that ultraviolet irradiation can significantly improve the sensing performance of semiconductor oxide gas sensors.

[0003] Titanium dioxide as a traditional n-type semiconductor has been widely studied for sensing, environmental remediation, solar energy conversion and energy storage applications. However, the single-component titanium dioxide has high resistance and long gas response recovery time, which is not dominant in practical applications; TiO2 hollow structure has flexible design of multi-layer micro / nano structure, easy to obtain compatibility and synergistic guest modification, porous framework and high specific surface area, therefore, it is expected that the use of TiO2 hollow structure for sensing can achieve higher photocatalytic activity and energy conversion efficiency, greater substrate adsorption capacity and stronger light intensity. The modification of fluorine ions can inhibit the growth of titanium dioxide grains, improve the crystallinity of TiO2, and promote the generation of hydroxyl radicals, thereby greatly improving the performance of TiO2. At the same time, the use of hydrofluoric acid in the synthesis process can also control the morphology of the material, so as to improve the gas sensing performance. Such an important method for improving the gas sensing performance of materials has not been fully investigated and researched. Therefore, it can be seen that the design and synthesis of fluorinated TiO2 gas sensing material with hollow structure will have important scientific and practical significance. However, to our knowledge, there are few reports on fluorinated titanium dioxide gas sensing material with hollow structure. Therefore, in this study, we prepared fluorinated titanium dioxide hollow microspheres by hydrothermal method and systematically studied the microstructure and gas sensing performance. In addition, under normal circumstances, the working temperature of gas sensor using metal oxide semiconductor as sensitive material is generally 200-500℃, which requires a large energy demand on the one hand, and accelerates the aging of the sensitive material during high temperature process, resulting in the shortening of the service life of the sensor. Recently, people have begun to use nanomaterial technology and light-assisted activation method to try to reduce the working temperature of the sensor to room temperature. Among them, light-assisted activation metal oxide semiconductor gas sensor has attracted more and more attention. The advantage of this technology is that only a few milliwatt LED lamps can be used to achieve high sensitivity of the sensor to gas, while reducing the aging process of the sensitive material, which is expected to improve the service life of the sensor. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a gas sensor based on ultraviolet light wave band with good selectivity, high sensitivity and good stability, and a detection method thereof.

[0005] The technical scheme of the present application is as follows:

[0006] A fluorinated TiO2 gas sensor based on ultraviolet light wave band mainly comprises an ultraviolet light source, a gas sensing material and an interdigital electrode plate, the gas sensing material is coated on the surface of the interdigital electrode plate, and the coating thickness is 1-100 μm; the composition of the gas sensing material is fluorinated titanium dioxide hollow microsphere material.

[0007] The fluorinated titanium dioxide hollow microsphere material is obtained by fluorination and etching of titanium dioxide using hydrofluoric acid through a water bath method.

[0008] The size of the fluorinated titanium dioxide hollow microsphere is 10-30 microns.

[0009] The interdigital electrode plate is an alumina substrate with a pure gold electrode on the front surface and a heating resistance wire on the back surface, and the heating temperature reaches 350 DEG C.

[0010] A preparation process of a fluorinated TiO2 gas sensor based on an ultraviolet light wave band, comprising the following steps:

[0011] (1) adding isopropyl titanate into a mixed solution of anhydrous ethanol and water, controlling the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1, adding hydrofluoric acid into the mixed solution under magnetic stirring, the mass fraction of the hydrofluoric acid solution itself is 40%, and the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution is controlled to be (1-4):10;

[0012] (2) moving the mixed solution obtained in step (1) to a hydrothermal reaction kettle lined with polytetrafluoroethylene, carrying out hydrothermal reaction at 200 DEG C for 12-14 hours, then using a centrifuge to carry out solid-liquid separation on the product after hydrothermal reaction, and using deionized water and ethanol to wash the obtained solid product for multiple times, placing the obtained solid product in a drying box for drying at 60 DEG C, and grinding to obtain a powder-shaped solid;

[0013] (3) heat treating the solid product obtained in step (2) at 400 DEG C for 4 hours to obtain a fluorinated TiO2 hollow sphere material;

[0014] (4) grinding the fluorinated TiO2 hollow sphere material into powder, dispersing the ground fluorinated TiO2 hollow sphere material powder into deionized water, ultrasonic treating to form a dispersion liquid with a concentration of 8-10 mg / ml, taking the dispersion liquid to coat the surface of the interdigital electrode plate, placing in a drying box for drying at 60 DEG C for 4-6 hours, and naturally cooling to room temperature to obtain a fluorinated TiO2 hollow sphere material gas sensor.

[0015] In step (4), the ultrasonic power is 240-260 W, and the ultrasonic time is 1 minute.

[0016] The working temperature of the fluorinated TiO2 hollow sphere material gas sensor based on an ultraviolet light wave band is room temperature, and the material can be integrated with a silicon-based microelectronic device.

[0017] Working principle: the present application is based on the ultraviolet band of the fluorinated TiO2 hollow sphere material gas sensor as a resistance type semiconductor gas sensor, mainly using the change of resistance when the semiconductor contacts the gas to detect the composition or concentration of the gas. When the device is placed in the air, the oxygen in the air is adsorbed on the surface of the gas sensitive material and reacts with the electrons to form surface adsorbed oxygen ions, at this time the material is in a high resistance state, when contacting the gas to be measured, the surface adsorbed oxygen ions react with the gas to be measured, and the electrons return to the semiconductor, the resistance decreases. Under the irradiation of ultraviolet light, the reaction can be carried out at room temperature.

[0018] Advantages of the present application:

[0019] (1) The present application adopts a water bath method to obtain a new type of fluorinated titanium dioxide hollow sphere material, the raw materials are easy to obtain, low in price and simple in preparation process, and the preparation scheme is a three-dimensional semiconductor hollow sphere structure preparation scheme with small equipment investment and simple process flow.

[0020] (2) The fluorine ions are uniformly distributed on the surface of the hollow sphere material of the present application, which can guide the accumulation of electrons on the surface material, strengthen the gas sensitive selectivity of the material, and the fluorine ions on the surface of the hollow sphere can help promote the additional oxygen adsorption on the material surface, thereby improving the gas sensitive performance in low temperature environment.

[0021] (3) The present application utilizes the excitation effect of ultraviolet light to reduce the required temperature for the operation of the sensor, which can work at room temperature, and slows down the material aging and damage caused by working in high temperature environment. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 SEM image of the fluorinated titanium dioxide hollow sphere material;

[0023] Figure 2 Response and recovery curve comparison of the fluorinated titanium dioxide hollow sphere material gas sensitive element and the pure titanium dioxide gas sensitive element at room temperature;

[0024] Figure 3 Response and recovery curve comparison of the fluorinated titanium dioxide hollow sphere material gas sensitive element with different fluorine titanium ratios at room temperature. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below, and the present application is implemented on the premise of the technical scheme of the present application, and detailed implementation mode and specific operation process are given, but the protection scope of the present application is not limited to the following embodiments.

[0026] Example 1

[0027] A fluorinated TiO2 hollow sphere material gas sensor based on ultraviolet light band, which is composed of a gas sensitive material and a heating substrate, is composed of an ultraviolet light source, a gas sensitive material and an interdigital electrode plate, the gas sensitive material is coated on the surface of the interdigital electrode plate, and the coating thickness is 100 μm. The preparation method comprises the following steps:

[0028] (1) adding isopropyl titanate into a mixed solution of anhydrous ethanol and water, controlling the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1; adding hydrofluoric acid into the above mixed solution under the environment of magnetic stirring, the mass fraction of the hydrofluoric acid solution itself is 40%, and the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution is controlled to be 1:10;

[0029] (2) moving the mixed solution obtained in step (1) to a hydrothermal reaction kettle lined with polytetrafluoroethylene, carrying out hydrothermal reaction at 200 DEG C for 12 h, then carrying out solid-liquid separation on the product after hydrothermal reaction by using a centrifuge, and sequentially washing the obtained solid product with deionized water and ethanol for multiple times, placing the obtained solid product in a drying box for drying at 60 DEG C, and grinding to obtain a powder-shaped solid;

[0030] (3) heat treating the solid product obtained in step (2) at 400 DEG C for 4 h, to obtain a fluorinated TiO2 hollow sphere material;

[0031] (4) grinding the fluorinated TiO2 hollow sphere material into powder, dispersing the ground fluorinated TiO2 hollow sphere material powder into deionized water, ultrasonic treating to form a dispersion liquid with a concentration of 8 mg / ml to 10 mg / ml, taking the dispersion liquid to coat on the surface of the interdigital electrode plate, placing in a drying box for drying at 60 DEG C for 4 h, and naturally cooling to room temperature, to obtain a fluorinated TiO2 hollow sphere material gas sensor.

[0032] In step (4), the ultrasonic power is 240 W, and the ultrasonic time is 1 min;

[0033] Example 2

[0034] A fluorinated TiO2 hollow sphere material gas sensor based on ultraviolet light band, which is composed of a gas sensitive material and a heating substrate, is composed of an ultraviolet light source, a gas sensitive material and an interdigital electrode plate, the gas sensitive material is coated on the surface of the interdigital electrode plate, and the coating thickness is 100 μm. The preparation method comprises the following steps:

[0035] (1) adding isopropyl titanate into a mixed solution of anhydrous ethanol and water, controlling the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1; adding hydrofluoric acid into the above mixed solution under the environment of magnetic stirring, the mass fraction of the hydrofluoric acid solution itself is 40%, and the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution is controlled to be 1:10;

[0036] (2) The mixed solution obtained in step (1) is moved to a hydrothermal reactor lined with polytetrafluoroethylene, and hydrothermal reaction is carried out at 200°C for 12h. The product after hydrothermal reaction is subjected to solid-liquid separation by a centrifuge, and the obtained solid product is washed with deionized water and ethanol for multiple times. The obtained solid product is placed in a drying box and dried at 60°C. After grinding, a powder-like solid is obtained;

[0037] (3) The solid product obtained in step (2) is heat-treated at 400°C for 4h to obtain a fluorinated TiO2 hollow sphere material;

[0038] (4) The fluorinated TiO2 hollow sphere material is ground into powder, and the ground fluorinated TiO2 hollow sphere material powder is dispersed in deionized water to form a dispersion liquid with a concentration of 8mg / ml-10mg / ml. The dispersion liquid is coated on the surface of the interdigital electrode plate, placed in a drying box and dried at 60°C for 4h, and naturally cooled to room temperature to obtain a fluorinated TiO2 hollow sphere material gas sensor.

[0039] In step (4), the ultrasonic power is 250W, and the ultrasonic time is 1min;

[0040] Example 3

[0041] A fluorinated TiO2 hollow sphere material gas sensor based on the ultraviolet light band is composed of a gas-sensitive material and a heating substrate, which is composed of an ultraviolet light source, a gas-sensitive material and an interdigital electrode plate. The gas-sensitive material is coated on the surface of the interdigital electrode plate with a coating thickness of 100μm. The preparation method comprises the following steps:

[0042] (1) Isopropyl titanate is added to a mixed solution of anhydrous ethanol and water, and the volume ratio of isopropyl titanate, anhydrous ethanol and water is controlled to be 5:60:1. Hydrofluoric acid is added to the above mixed solution under magnetic stirring, the mass fraction of the hydrofluoric acid solution itself is 40%, and the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution is controlled to be 3:10;

[0043] (2) The mixed solution obtained in step (1) is moved to a hydrothermal reactor lined with polytetrafluoroethylene, and hydrothermal reaction is carried out at 200°C for 12h. The product after hydrothermal reaction is subjected to solid-liquid separation by a centrifuge, and the obtained solid product is washed with deionized water and ethanol for multiple times. The obtained solid product is placed in a drying box and dried at 60°C. After grinding, a powder-like solid is obtained;

[0044] (3) The solid product obtained in step (2) is heat-treated at 400°C for 4h to obtain a fluorinated TiO2 hollow sphere material;

[0045] (4) grinding the fluorinated TiO2hollow sphere material into powder, dispersing the ground fluorinated TiO2hollow sphere material powder into deionized water, ultrasonic treatment into a dispersion liquid of 8 mg / ml-10 mg / ml, taking the dispersion liquid to coat the surface of the interdigital electrode plate, placing in a drying oven at 60°C for drying for 4 h, naturally cooling to room temperature, to obtain a fluorinated TiO2hollow sphere material gas sensor.

[0046] In step (4), the ultrasonic power is 260 W, and the ultrasonic time is 1 min;

[0047] Example 4

[0048] A fluorinated TiO2hollow sphere material gas sensor based on the ultraviolet light band, composed of a gas sensitive material and a heating substrate, composed of an ultraviolet light source, a gas sensitive material and an interdigital electrode plate, the gas sensitive material being coated on the surface of the interdigital electrode plate, the coating thickness being 100 μm. The preparation method comprises the following steps:

[0049] (1) adding isopropyl titanate into a mixed solution of anhydrous ethanol and water, controlling the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1; adding hydrofluoric acid into the above mixed solution under the environment of magnetic stirring, the mass fraction of the hydrofluoric acid solution itself being 40%, controlling the molar ratio of hydrogen fluoride and isopropyl titanate in the mixed solution to be 4:10;

[0050] (2) moving the mixed solution obtained in step (1) into a hydrothermal reaction kettle lined with polytetrafluoroethylene, carrying out hydrothermal reaction at a temperature of 200°C for 12 h, then using a centrifuge to carry out solid-liquid separation on the product after hydrothermal reaction, and using deionized water and ethanol to wash the obtained solid product for multiple times, placing the obtained solid product in a drying oven for drying at 60°C, and grinding to obtain a powder-shaped solid;

[0051] (3) heat treating the solid product obtained in step (2) at 400°C for 4 h, to obtain a fluorinated TiO2hollow sphere material;

[0052] (4) grinding the fluorinated TiO2hollow sphere material into powder, dispersing the ground fluorinated TiO2hollow sphere material powder into deionized water, ultrasonic treatment into a dispersion liquid of 8 mg / ml-10 mg / ml, taking the dispersion liquid to coat the surface of the interdigital electrode plate, placing in a drying oven at 60°C for drying for 4 h, naturally cooling to room temperature, to obtain a fluorinated TiO2hollow sphere material gas sensor.

[0053] In step (4), the ultrasonic power is 240 W, and the ultrasonic time is 1 min;

[0054] Example 5

[0055] A fluorinated TiO2 hollow sphere material gas sensor based on ultraviolet light band, which is composed of a gas sensitive material and a heating substrate, and is composed of an ultraviolet light source, a gas sensitive material and an interdigital electrode plate, wherein the gas sensitive material is coated on the surface of the interdigital electrode plate with a coating thickness of 100 μm. The preparation method comprises the following steps:

[0056] (1) adding isopropyl titanate into a mixed solution of anhydrous ethanol and water, controlling the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1; adding hydrofluoric acid into the above mixed solution under the environment of magnetic stirring, the mass fraction of the hydrofluoric acid solution itself is 40%, and the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution is controlled to be 3:10;

[0057] (2) moving the mixed solution obtained in step (1) to a hydrothermal reaction kettle lined with polytetrafluoroethylene, carrying out hydrothermal reaction at 200℃ for 13h, then carrying out solid-liquid separation on the product after hydrothermal reaction by using a centrifuge, and washing the obtained solid product with deionized water and ethanol for multiple times in sequence, placing the obtained solid product in a drying box for drying at 60℃, and grinding to obtain a powder-shaped solid;

[0058] (3) heat treating the solid product obtained in step (2) at 400℃ for 4h to obtain a fluorinated TiO2 hollow sphere material;

[0059] (4) grinding the fluorinated TiO2 hollow sphere material into powder, dispersing the ground fluorinated TiO2 hollow sphere material powder into deionized water, ultrasonic treating to form a dispersion liquid with a concentration of 8mg / ml-10mg / ml, taking the dispersion liquid to coat on the surface of the interdigital electrode plate, placing in a drying box for drying at 60℃ for 4h, and naturally cooling to room temperature to obtain a fluorinated TiO2 hollow sphere material gas sensor.

[0060] In step (4), the ultrasonic power is 260W, and the ultrasonic time is 1min;

[0061] Example 6

[0062] A fluorinated TiO2 hollow sphere material gas sensor based on ultraviolet light band, which is composed of a gas sensitive material and a heating substrate, and is composed of an ultraviolet light source, a gas sensitive material and an interdigital electrode plate, wherein the gas sensitive material is coated on the surface of the interdigital electrode plate with a coating thickness of 100 μm. The preparation method comprises the following steps:

[0063] (1) adding isopropyl titanate into a mixed solution of anhydrous ethanol and water, controlling the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1; adding hydrofluoric acid into the above mixed solution under the environment of magnetic stirring, the mass fraction of the hydrofluoric acid solution itself is 40%, and the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution is controlled to be 3:10;

[0064] (2) The mixed solution obtained in step (1) is moved to a hydrothermal reactor with a polytetrafluoroethylene inner liner, and hydrothermal reaction is carried out at 200°C for 14h. The product after hydrothermal reaction is subjected to solid-liquid separation by a centrifuge, and the obtained solid product is washed with deionized water and ethanol for multiple times. The obtained solid product is placed in a drying box and dried at 60°C. After grinding, a powder-like solid is obtained;

[0065] (3) The solid product obtained in step (2) is heat-treated at 400°C for 4h to obtain a fluorinated TiO2 hollow sphere material;

[0066] (4) The fluorinated TiO2 hollow sphere material is ground into powder, and the ground fluorinated TiO2 hollow sphere material powder is dispersed in deionized water to form a dispersion liquid with a concentration of 8mg / ml-10mg / ml. The dispersion liquid is coated on the surface of the interdigital electrode plate, and placed in a drying box and dried at 60°C for 4h. After natural cooling to room temperature, a fluorinated TiO2 hollow sphere material gas sensor is obtained.

[0067] In step (4), the ultrasonic power is 260W, and the ultrasonic time is 1min;

[0068] In the above six examples, the first four examples obtained four groups of fluorinated TiO2 hollow sphere material gas sensors with different performances by changing the molar ratio of hydrogen fluoride to isopropyl titanate, and it was concluded that with the change of the molar ratio of hydrogen fluoride to isopropyl titanate, the gas sensing performance of the fluorinated TiO2 hollow sphere material gas sensor showed a trend of first increasing and then decreasing. When the molar ratio of hydrogen fluoride to isopropyl titanate was 0.3, the gas sensing performance of the fluorinated TiO2 hollow sphere material gas sensor was optimal. The last two examples changed the hydrothermal reaction time and concluded that when the hydrothermal time increased to 14h, the gas sensing performance of the fluorinated TiO2 hollow sphere material gas sensor showed a downward trend.

Claims

1. A fluorinated TiO2 gas sensor based on the ultraviolet light band, characterized in that, The fluorinated TiO2 gas sensor mainly consists of an ultraviolet light source, a gas-sensitive material, and an interdigitated electrode plate. The gas-sensitive material is coated on the surface of the interdigitated electrode plate with a coating thickness of 1 μm to 100 μm. The gas-sensitive material is composed of fluorinated titanium dioxide hollow microspheres. The fluorinated titanium dioxide hollow microsphere material is obtained by water bath method and by fluorination and etching of titanium dioxide with hydrofluoric acid; the size of the fluorinated titanium dioxide hollow microspheres is 10μm~30μm; The fluorinated TiO2 gas sensor based on the ultraviolet light band operates at room temperature, realizing the integration of materials with silicon-based microelectronic phases.

2. The fluorinated TiO2 gas sensor based on the ultraviolet light band according to claim 1, characterized in that, The interdigitated electrode plate is an alumina substrate with pure gold electrodes on the front and heating resistance wires on the back, with a heating temperature of up to 350°C.

3. A fabrication process for a fluorinated TiO2 gas sensor based on ultraviolet light, characterized in that, Includes the following steps: (1) Add isopropyl titanate to a mixed solution of anhydrous ethanol and water, and control the volume ratio of isopropyl titanate, anhydrous ethanol and water to be 5:60:1; add hydrofluoric acid with a mass fraction of 40% to the above mixed solution under magnetic stirring, and control the molar ratio of hydrogen fluoride to isopropyl titanate in the mixed solution to be (1-4):

10. (2) The solution obtained in step (1) is transferred to a hydrothermal reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 200°C for 12-14 hours. The product after hydrothermal reaction is then separated into solid and liquid by centrifuge, and the obtained solid product is washed repeatedly with deionized water and ethanol. The obtained solid product is placed in a drying oven and dried at 60°C. After grinding, a powdered solid is obtained. (3) The powdered solid obtained in step (2) is heat-treated at 400°C for 4 hours to obtain fluorinated TiO2 hollow sphere material; (4) Grind the fluorinated TiO2 hollow sphere material into powder, then disperse the ground fluorinated TiO2 hollow sphere material powder into deionized water, and sonicate it into a dispersion of 8mg / ml~10mg / ml. Then take the dispersion and coat it onto the surface of the interdigitated electrode plate, place it in a drying oven at 60℃ for 4h~6h, and cool it naturally to room temperature to obtain the fluorinated TiO2 hollow sphere material gas sensor.

4. The preparation process according to claim 3, characterized in that, In step (4), the ultrasonic power is 240W~260W and the ultrasonic time is 1min.

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