Au / TiO 2 / PEDOT sensitive film material and its preparation method and application in sensor

Abstract

The invention discloses an Au / TiO2 / PEDOT sensitive film material and a preparation method thereof and an application of the material in a sensor. In the Au / TiO2 / PEDOT sensitive film material, TiO2 nanoparticles adhere to PEDOT polymers to form a microporous film, and the TiO2 nanoparticles cooperate with Au particles to make the microporous film a porous film. The Au / TiO2 / PEDOT sensitive film surface acoustic wave humidity-carbon dioxide dual response sensor responds to carbon dioxide in the acoustic-electric effect under illumination conditions. Since the frequency shift directions of the responses of the two are different, the mass load effect responds to the humidity frequency to the left, and the acoustic-electric effect responds to the carbon dioxide frequency under illumination conditions to the right, which effectively identifies humidity and carbon dioxide.

Description

Technical Field

[0001] The present invention relates to the field of environmental detection technology, in particular to Au / TiO 2 / PEDOT sensitive film material, preparation method thereof and application in sensors. Background Art

[0002] Humidity is one of the important and common indicators in the environment. In life, low humidity can easily make people feel dry and rough skin and feel uncomfortable, while high humidity can easily make people feel difficult to breathe. At the same time, humidity measurement also plays a great role in agriculture, industry, electronics, and food industry, and provides a great role in safe and normal production and consumption activities. Therefore, in order to improve people's living standards and maintain normal production activities, humidity measurement is also very important. At present, with the development of industry, the carbon emissions of various countries have increased year by year, and a more serious greenhouse effect has been caused. Excessive carbon dioxide concentration will affect people's normal life. Excessive concentration will cause discomfort, dizziness, irritability, etc., so the research on carbon dioxide sensors is very necessary.

[0003] At present, when humidity sensors and carbon dioxide sensors on the market detect humidity and carbon dioxide, humidity sensors can only detect humidity, and carbon dioxide sensors can only detect carbon dioxide. It is impossible to achieve a sensor that can detect humidity and carbon dioxide gas. Summary of the invention

[0004] The purpose of the present invention is to provide an Au / TiO 2 / PEDOT sensitive film material, PEDOT is a polymer of EDOT (3,4-ethylenedioxythiophene monomer).

[0005] Another object of the present invention is to provide the Au / TiO 2 / PEDOT sensitive film material preparation method.

[0006] Another object of the present invention is to provide the Au / TiO 2 / Application of PEDOT sensitive film materials in sensors.

[0007] The technical solution adopted to achieve the purpose of the present invention is:

[0008] Au / TiO 2 / PEDOT sensitive film material, in which TiO 2 Nanoparticles adhere to PEDOT polymer to form a microporous membrane, TiO 2 The nanoparticles and Au particles cooperate with each other to turn the microporous membrane into a porous membrane.

[0009] The Au / TiO 2 / PEDOT sensitive film material is prepared by the following method:

[0010] Step 1, dissolving tetrachloroauric acid trihydrate, titanium dioxide and 3-4-ethylenedioxythiophene in a solvent to obtain a mixed solution;

[0011] Step 2, using the mixed solution as a precursor, performing a photocatalytic reaction, and air-drying to obtain a composite film, namely the Au / TiO 2 / PEDOT sensitive film material;

[0012] Alternatively, the step 3 may be further included: washing the composite film and air-drying it again to obtain the Au / TiO 2 / PEDOT sensitive film material;

[0013] Alternatively, the step 4 is further included: the Au / TiO 2 / PEDOT sensitive film material is attached to the tantalum sheet, and then the Au / TiO 2 / PEDOT sensitive film material is removed from the tantalum sheet.

[0014] In the above technical solution, the solvent in step 1 is ethanol, and the concentration of tetrachloroauric acid trihydrate in the mixed solution is 0.0005-0.001 mol L -1 The concentration of titanium dioxide is 5-10 mg mL -1 The concentration of 3-4-ethylenedioxythiophene is 50-100 mg mL -1 .

[0015] In the above technical solution, the air-drying in step 2 is carried out in a light box with a high-pressure mercury lamp as the light source, the light source power is 220-230W, the illumination time is 2.5-3 hours, and the air-drying time is 30-45 minutes.

[0016] In the above technical solution, in step 3, during cleaning, an alcohol solution is sprayed on the wet film to wash away excess 3-4-ethylenedioxythiophene on the surface of the film that has not been polymerized into a polymer. After cleaning, the air-drying time is 10 to 20 minutes.

[0017] In the above technical solution, in step 4, the glue leveling includes two processes: low-speed glue leveling and high-speed glue leveling. The uniform speed of the low-speed glue leveling is 1:400-600rad / min, the time is 5-10s, and the uniform speed of the high-speed glue leveling is 2:1500-1800rad / min, the time is 20-30s.

[0018] In another aspect of the present invention, the Au / TiO 2 / PEDOT sensitive film materials combined with surface acoustic wave devices are used as sensors in detecting humidity and carbon dioxide.

[0019] In the above technical solution, the Au / TiO 2 The PEDOT sensitive film material is cut into blocks of predetermined size and attached to the delay zone of the delay line type surface acoustic wave device to detect humidity and carbon dioxide concentration.

[0020] In the above technical solution, the predetermined size is a rectangular block of 1.2 mm×1.3 mm and a thickness of 0.3 mm.

[0021] In the above technical solution, when carbon dioxide detection is performed, the detection method includes the following steps:

[0022] Step 1, establishing a gas measurement system, wherein the Au / TiO 2 / PEDOT sensitive film material is attached to the surface acoustic wave device as a carbon dioxide sensor, the sensor is connected to a network analyzer, different carbon dioxide concentrations are prepared under a light environment, the characteristic frequency-loss curve under each carbon dioxide concentration is detected by the sensor, the characteristic frequency offset value of each carbon dioxide concentration is obtained through the characteristic frequency-loss curve, a coordinate system of carbon dioxide concentration and characteristic frequency offset value under carbon dioxide concentration is established, and the characteristic frequency offset under different carbon dioxide concentrations and the corresponding carbon dioxide concentration are substituted into the coordinate system to form a standard curve;

[0023] Step 2, fit the standard curve into a straight line to obtain the linear regression equation of the straight line, obtain the loss-characteristic frequency curve of the object to be tested and obtain the characteristic frequency offset value through the loss-characteristic frequency, substitute the characteristic frequency offset value of the object to be tested into the linear regression equation to obtain the carbon dioxide concentration of the object to be tested.

[0024] In the above technical scheme, the illumination photocurrent is 17-18A; the carbon dioxide concentration range is 500ppm-10000ppm, and the test points are 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000ppm, a total of 17 test points.

[0025] In the above technical solution, when performing humidity detection, the detection method includes the following steps:

[0026] Step 1, establish a gas measurement system to simulate the adsorption process, wherein the Au / TiO 2 / PEDOT sensitive film material is attached to the surface acoustic wave device as a humidity sensor, the sensor is connected to a network analyzer, different relative humidity is prepared in a lightless environment, and the characteristic frequency-loss curve under each relative humidity is detected by the humidity sensor. During the detection, the relative humidity is increased from small to large to simulate the adsorption process, and the characteristic frequency offset value of each relative humidity is obtained through the characteristic frequency-loss curve, and a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity is established, and the characteristic frequency offset values ​​under different relative humidity and the corresponding relative humidity are substituted into the coordinate system to form an adsorption standard curve;

[0027] Step 2, establishing a gas measurement system to simulate the desorption process, wherein the Au / TiO 2 / PEDOT sensitive film is attached to the surface acoustic wave device as a humidity sensor, the sensor is connected to a network analyzer, different relative humidity is prepared in a lightless environment, and the characteristic frequency-loss curve under each relative humidity is detected by the humidity sensor. During the detection, the relative humidity is reduced from large to small to simulate the desorption process, and the characteristic frequency offset value of each relative humidity is obtained through the characteristic frequency-loss curve, and a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity is established, and the characteristic frequency offset values ​​under different relative humidity and the corresponding relative humidity are substituted into the coordinate system to form a desorption standard curve;

[0028] Step 3, fit the adsorption standard curve and the desorption standard curve into a straight line to obtain the linear regression equation of the straight line, obtain the characteristic frequency-loss curve of the object to be measured and obtain the characteristic frequency offset value through the characteristic frequency-loss curve, substitute the characteristic frequency offset value of the object to be measured into the linear regression equation to obtain the relative humidity of the object to be measured.

[0029] In the above technical solution, the standard relative humidity is the ratio of the actual water vapor content in the air to the water vapor content when saturation is reached at a certain temperature; the standard relative humidity test range is 0-90% RH, in step 1, the relative humidity is increased from 0% RH to 90% RH, each test point is separated by 5% RH, and there are a total of 19 test points; in step 2, the relative humidity is reduced from 90% RH to 0% RH, each test point is separated by 5% RH, and there are a total of 19 test points.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. Due to TiO 2The catalyst has a certain control effect on the particle size and dispersion of gold particles, which makes the distribution of Au nanoparticles have high electrical properties, and forms many gas channels in the porous membrane structure, increasing the contact area between the sensitive material and the analysis gas, which is beneficial for the attachment of water molecules and the entry of carbon dioxide into the channel, and undergoing a series of reactions with the sensitive membrane.

[0032] 2. Au / TiO 2 The porous structure of the Au / TiO / PEDOT sensitive film can absorb a large number of gas molecules, making the Au / TiO 2 / PEDOT sensitive film surface acoustic wave humidity-carbon dioxide dual response sensor responds to humidity by mass loading effect; TiO 2 Good photocatalytic performance, PEDOT has a reversible bidirectional conversion ability between the reduced state and the oxidized state, which will change the conductivity of the sensitive film. 2 The surface acoustic wave humidity-carbon dioxide dual response sensor with PEDOT sensitive film responds to carbon dioxide through the acoustic-electric effect under light conditions. Since the frequency shift directions of the two responses are different, the mass load effect responds to the humidity frequency shifting to the left, and the acoustic-electric effect responds to the carbon dioxide frequency shifting to the right under light conditions, effectively identifying humidity and carbon dioxide.

[0033] 3. Surface acoustic wave sensors are popular because of their low power, low loss, small device size, portability, good performance, and fast response. They convert corresponding signals into corresponding electrical signals, are easy to collect and organize signals, are easy to operate, require inexpensive instruments, have fast response, high sensitivity, good selectivity, and do not require complicated sample pre-treatment processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The Au / PEDOT and TiO 2 / PEDOT、Au / TiO 2 Scanning electron microscope (SEM) image of PEDOT / PEDOT sensitive film

[0035] Figure 2 The Au / TiO obtained in Example 1 2 Transmission electron microscopy image of Au / TiO / PEDOT sensitive film, where a is Au / TiO 2 a is the TEM image of the / PEDOT sensitive film, b is the corresponding EDS element mapping of Ti, O, and Au.

[0036] Figure 3 19 characteristic frequency-loss curves of relative humidity adsorbed by the sensor in Example 2;

[0037] Figure 419 characteristic frequency-loss curves of relative humidity of the sensor desorption humidity in Example 2;

[0038] Figure 5 The standard curve in Example 2 is fitted into a straight line;

[0039] Figure 6 17 characteristic frequency-loss curves of carbon dioxide concentration detected by the sensor in Example 3;

[0040] Figure 7 The standard curve in Example 3 is fitted into a straight line;

[0041] Figure 8 (a) is the characteristic frequency-loss curve of 17 relative humidity detected by the sensor in a no-light and no-carbon dioxide environment in Example 4;

[0042] Figure 8 (b) is the characteristic frequency-loss curve of 17 relative humidity detected by the sensor in Example 4 under the condition of no light and carbon dioxide concentration of 2000 ppm;

[0043] Fig. 9 (a) is the characteristic frequency-loss curve of 21 carbon dioxide concentrations detected by the sensor in an environment with light and no relative humidity in Example 4;

[0044] Fig. 9 (b) is the characteristic frequency-loss curve of 21 carbon dioxide concentrations detected by the sensor under light and relative humidity of 40% RH in Example 4;

[0045] Fig.10 The characteristic frequency-loss standard curve of the relative humidity is obtained for the 17 relative humidities measured in the no-light, no-carbon dioxide environment in Example 4 (eg Figure 8 a) and the 17 relative humidities measured in an environment without light and with a carbon dioxide concentration of 2000ppm to obtain the characteristic frequency-loss standard curve of the relative humidity (such as Figure 8 b) The fitted straight line.

[0046] Fig.11 The characteristic frequency-loss standard curve of the carbon dioxide concentration is obtained for the 21 carbon dioxide concentrations measured in the light-free relative humidity environment in Example 4 (such as Fig. 9 a) and 21 carbon dioxide concentrations measured under light and relative humidity of 40% RH to obtain the characteristic frequency-loss standard curve of the carbon dioxide concentration (such as Fig. 9 b) The fitted straight line. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Delay line surface acoustic wave device: Beijing Zhongxun Sifang Technology Co., Ltd.

[0049] Network analyzer: Beijing Fanshi Measurement and Control Technology Co., Ltd.

[0050] SZCL-2A digital display intelligent temperature control magnetic stirrer: Gongyi Yuhua Instrument Co., Ltd.

[0051] Room temperature 20~25℃.

[0052] The sources of drug purchase in the following embodiments are as follows:

[0053] 3Hydrated tetrachloroauric acid was purchased from Alfa Aesar (China) Chemical Co., Ltd.;

[0054] Titanium dioxide powder was purchased from Xuancheng Jingrui New Materials Co., Ltd.;

[0055] 3-4 Ethylenedioxythiophene was purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.;

[0056] Anhydrous ethanol was purchased from Tianjin Jiangtian Tongyi Technology Co., Ltd.;

[0057] In the following examples, the ratio of 10 mL of a mixed solution of tetrachloroauric acid trihydrate, titanium dioxide and 3-4-ethylenedioxythiophene in alcohol as solvent is 0.001 mol L -1 of tetrachloroauric acid trihydrate, 10 mg mL -1 of titanium dioxide and 100mg mL -1 10mL mixed solution of 3-4-ethylenedioxythiophene.

[0058] Example 1

[0059] Au / TiO 2 The preparation method of the PEDOT sensitive film material comprises the following steps:

[0060] Step 1, preparation stage: weigh 0.0039g of tetrachloroauric acid trihydrate with an electronic balance to prepare a 10ml solution with alcohol as solvent and place it in a 25ml brown volumetric flask, stir it thoroughly with a glass rod for standby use, then weigh 0.1000g of hydrophilic titanium dioxide nanopowder with an average particle size of 10nm, pour the titanium dioxide nanopowder into the volumetric flask of tetrachloroauric acid, blow down the titanium dioxide powder attached to the inner wall with a rubber balloon, put it on an ultrasonic device for ultrasonication for 15-20min, and when it becomes a uniform suspension, the ultrasonication is completed. Use a pipette to draw 1g of 751.3μL of 3-4 ethylenedioxythiophene solution and then drop it into the mixed solution of tetrachloroauric acid and titanium dioxide. In order to prevent the ultrasonication time from being too long and the temperature from being too high to destroy the physical structure of 3-4 ethylenedioxythiophene, the ultrasonication generally does not exceed 5 minutes, so as to form a component of 0.001mol L -1 Tetrachloroauric acid trihydrate, 10mgmL -1 of titanium dioxide and 100mgmL -1 10mL mixed solution of 3-4-ethylenedioxythiophene.

[0061] Step 2, illumination stage: Pour 10mL of the mixed solution into a quartz culture dish with a diameter of 4cm and put it into the light box of the high-pressure mercury lamp. Turn on the low-temperature thermostatic bath connected to the high-pressure mercury lamp, turn on the switch, refrigeration, and circulation from right to left, then turn on the high-pressure mercury lamp equipment, enter the password, turn on the circulating water pump and the mercury lamp light source, wait for it to preheat for about five minutes, wait for the preheating warning light to turn off, adjust the light source power, adjust the power of the 302nm high-pressure mercury lamp to 220-230W, illuminate for 2.5-3 hours, the solution gradually changes from a yellowish milky white liquid to a purple solution, and then gradually condenses into small purple dots, and then these dots will gradually connect. In one hour, re-ultrasound for three minutes to break up the solution and distribute it more evenly. After the illumination is completed, adjust the frequency to 0, turn off the mercury lamp light source and the circulating water pump in turn, and turn off the circulation, refrigeration, and switch of the low-temperature thermostatic bath from left to right. Take the quartz culture dish out of the light box and place it in a well-ventilated place. After 30 to 45 minutes of ventilation, the excess alcohol will evaporate completely under natural ventilation. At this time, the film in the quartz dish is already darker in color and has a smooth surface.

[0062] Step 3, sensitive film treatment stage: Use a rubber-tipped dropper to take 0.5 ml of alcohol solution and gently spray it on the wet film to wash away the excess 3-4-ethylenedioxythiophene on the surface of the film that has not polymerized into a polymer, and dispose of the excess 3-4-ethylenedioxythiophene into a waste liquid bucket. After the film material is ventilated for 10 to 20 minutes, the tantalum sheet is cleaned with alcohol and dried with an infrared lamp for later use. Use flat-mouthed tweezers used in medical surgery to cut the film material into appropriate sizes and stick them on the tantalum sheet. Place the film material attached on the tray of the glue machine, and perform two processes of low-speed and high-speed glueing respectively. The adjustment knob sets the parameters as follows:

[0063] Uniform speed 1:600rad / min, time 6s

[0064] Uniform speed 2: 1800rad / min, time 25s

[0065] Step 4, sensitive film transfer stage: Use medical surgical tweezers to remove the thin film material attached to the tantalum sheet, gently flatten it with a glass slide, then remove it and put it into a sample tube and put it in the refrigerator for later use. Take out the thin film material from the sample tube, use tweezers to assist with a surgical knife to cut out a 1.2mm×1.3mm rectangular piece with a height of about 0.3mm to obtain Au / TiO 2 / PEDOT sensitive film, use 90℃ ultrapure water to heat and slightly wet the film material on one side, and gently stick this side film material to the center of the delay area. After it is normally air-dried, it can be naturally bonded, and the sensor is completed.

[0066] According to the above preparation method, Au / PEDOT can be prepared without adding titanium dioxide nanopowder in step 1. Similarly, Au / PEDOT can be prepared without adding tetrachloroauric acid trihydrate in step 1. The performances of the three are verified as follows.

[0067] Example 1 Au / PEDOT, TiO 2 / PEDOT、Au / TiO 2 The scanning electron microscope (SEM) image of the / PEDOT sensitive film is shown in Figure 1 As shown, the Au / TiO 2 Transmission electron microscopy (TEM) image of PEDOT sensitive film Figure 2 As shown. Figure 1 It can be seen that the Au / PEDOT composite film is composed of a continuous PEDOT matrix and Au particles with uneven particle sizes dispersed therein. Among the Au particles, the small particles are only a few nanometers, and the large agglomerated particles are as large as one micron. 2 TiO / PEDOT sensitive film 2After the nanoparticles and PEDOT were mixed, ultrasonicated, and irradiated with a mercury lamp to polymerize PEDOT, TiO 2 The nanoparticles adhered to the PEDOT polymer to form a microporous membrane. 2 The micropores constructed by nanoparticles become channels for gas molecules to enter the sensitive membrane. 2 / PEDOT sensitive film due to TiO 2 The interaction between nanoparticles and Au particles makes Au / TiO 2 The TiO / PEDOT ternary sensitive film also becomes a porous film, which is composed of loose particle aggregates of about 100 nm adhered by PEDOT. 2 Compared with Au / TiO / PEDOT film, 2 The / PEDOT sensitive film has higher electrical properties due to the distribution of Au nanoparticles. 2 The catalyst has a certain control effect on the particle size and dispersion of gold particles. In this porous structure, many gas channels are formed, which increases the contact area between the sensitive material and the analysis gas, facilitates the attachment of water molecules and the entry of carbon dioxide into the channel, and undergoes a series of reactions with the sensitive membrane.

[0068] Example 2

[0069] Example 1 Au / TiO 2 The PEDOT sensitive film material is cut into pieces of a predetermined size and attached to the delay zone of a delay line type surface acoustic wave device, and used as a surface acoustic wave humidity-carbon dioxide dual response sensor in detecting relative humidity. The detection method comprises the following steps:

[0070] 1) Establishing a gas measurement system to simulate the adsorption process, wherein the Au / TiO 2 The surface acoustic wave humidity-carbon dioxide dual response sensor made of PEDOT sensitive film material was used as a working device. The sensor was connected to a network analyzer. In a lightless environment, 19 different relative humidities were prepared to conduct humidity adsorption experiments on the sensor (the 19 relative humidities increased from small to large, namely 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90% RH). Each relative humidity was detected by a gas measurement system to obtain the characteristic frequency-loss curves of the 19 relative humidities (such as Figure 3 ), obtain the characteristic frequency offset value of each relative humidity through the characteristic frequency-loss curve, establish a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity, substitute the characteristic frequency offset values ​​and relative humidity under all relative humidities into the coordinate system, and form a standard curve.

[0071] 2) Establishing a gas measurement system to simulate the desorption process, wherein the Au / TiO 2 The surface acoustic wave humidity-carbon dioxide dual response sensor with a / PEDOT sensitive film was used as a working device. The sensor was connected to a network analyzer. In a lightless environment, 19 different relative humidities were prepared to carry out a desorption experiment of the sensor on humidity (the 19 relative humidities decreased from large to small, namely 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 0% RH). The 19 relative humidities were detected by a gas measurement system to obtain the characteristic frequency-loss curve of the relative humidity ( Figure 4 ), obtain the characteristic frequency offset value of each relative humidity through the characteristic frequency-loss curve, establish a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity, substitute the characteristic frequency offset values ​​and relative humidity under all relative humidities into the coordinate system, and form a standard curve.

[0072] 3) Fitting the standard curve into a straight line to obtain a linear regression equation of the straight line, obtaining a characteristic frequency-loss curve of the object to be measured and obtaining a characteristic frequency offset value through the characteristic frequency-loss curve, substituting the characteristic frequency offset value of the object to be measured into the linear regression equation to obtain the relative humidity of the object to be measured.

[0073] The standard curve was fitted into a straight line. Figure 5 As shown in the figure, under high humidity, the mass loading effect and elastic effect work together, and two linear response zones are formed in the relative humidity range of 0-90%RH. Specifically, in the relative humidity range of 0-55%RH, the sensitivities of adsorption and desorption are 0.034%RH KHz, respectively. -1 and 0.041%RH KHz -1 In the relative humidity range of 55% to 90% RH, the sensitivity of the adsorption and desorption processes is 0.218% RH KHz -1 and 0.186%RH KHz -1 .

[0074] Adsorption process:

[0075] The linear regression equation for relative humidity 0-55% RH is Y=-0.034X+0.155;

[0076] The linear regression equation for relative humidity 55% to 90% RH is Y = -0.218X + 10.545;

[0077] Desorption process:

[0078] The linear regression equation for relative humidity 0-55%RH is Y=-0.041X+0.257;

[0079] The linear regression equation for relative humidity 55% to 90% RH is Y = -0.186X + 8.126;

[0080] Y is the characteristic frequency shift value, and X is the relative humidity.

[0081] Example 3

[0082] Example 1 Au / TiO 2 / PEDOT sensitive film material, cut into pieces of predetermined size, attached to the delay zone of the delay line type surface acoustic wave device, and used as a humidity and carbon dioxide dual response gas sensor in detecting carbon dioxide concentration. 2 A method for using a surface acoustic wave humidity-carbon dioxide dual response sensor of a PEDOT sensitive film to detect carbon dioxide concentration includes the following steps:

[0083] 1) Establishing a gas measurement system, wherein the Au / TiO 2 A surface acoustic wave humidity-carbon dioxide dual response sensor with a PEDOT / PEDOT sensitive film was used as a working device, the sensor was connected to a network analyzer, and 17 carbon dioxide concentrations were prepared under a light environment (the 17 carbon dioxide concentrations increased from small to large, respectively 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000 ppm), and the 17 carbon dioxide concentrations were detected by a gas measurement system to obtain the characteristic frequency-loss curve of the carbon dioxide concentration (such as Figure 6 ), obtain the characteristic frequency offset value of each carbon dioxide concentration through the characteristic frequency-loss curve, establish a coordinate system of carbon dioxide concentration and the characteristic frequency offset value at the carbon dioxide concentration, substitute the characteristic frequency offset values ​​and carbon dioxide concentration at all carbon dioxide concentrations into the coordinate system to form a standard curve.

[0084] 2) Fitting the standard curve into a straight line to obtain a linear regression equation of the straight line, obtaining a characteristic frequency-loss curve of the object to be measured and obtaining a characteristic frequency offset value through the characteristic frequency-loss curve, substituting the characteristic frequency offset value of the object to be measured into the linear regression equation to obtain the carbon dioxide concentration of the object to be measured.

[0085] The standard curve was fitted into a straight line. Figure 7 As shown in the figure, in the range of 500-7000ppm, the center frequency of the sensor gradually increases with the increase of carbon dioxide concentration. However, when the carbon dioxide concentration continues to increase to 8000ppm, the center frequency of the sensor decreases slightly and remains unchanged with the increase of carbon dioxide concentration ( Figure 7). In the two carbon dioxide concentration ranges of 0-2000ppm and 2000-7000ppm, the frequency shift is linearly related to the carbon dioxide concentration.

[0086] In the range of CO2 concentration from 500 to 2000 ppm, the sensitivity of the sensor reaches 0.003kHz ppm -1 , the detection limit is 50ppm. The linear regression equation is Y=0.003X-0.884, where Y is the characteristic frequency shift value and X is the concentration of carbon dioxide.

[0087] Example 4

[0088] Example 1 Au / TiO 2 The Au / TiO / PEDOT sensitive film is cut into blocks of a predetermined size and attached to the delay zone of a delay line type surface acoustic wave device to be used as a surface acoustic wave humidity-carbon dioxide dual response sensor to selectively detect humidity and carbon dioxide: a gas measurement system is established, wherein the Au / TiO 2 The surface acoustic wave humidity-carbon dioxide dual response sensor with a PEDOT sensitive film is used as a working device, and the sensor is connected to a network analyzer.

[0089] (1) In a light-free, carbon dioxide-free environment, 17 different relative humidities were prepared. The 17 relative humidities were detected using a gas measurement system to obtain the characteristic frequency-loss curves of the relative humidity (e.g. Figure 8 a), obtain the characteristic frequency offset value of each relative humidity through the characteristic frequency-loss curve (17 relative humidities increase in sequence from small to large), establish a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity, substitute the characteristic frequency offset values ​​and relative humidity under all relative humidities into the coordinate system to form a standard curve.

[0090] (2) In an environment without light and with a carbon dioxide concentration of 2000 ppm, 17 different relative humidities were prepared. The gas measurement system was used to detect the 17 relative humidities and obtain the characteristic frequency-loss curves of the relative humidity (such as Figure 8 b), obtain the characteristic frequency offset value of each relative humidity through the characteristic frequency-loss curve, (17 relative humidities increase from small to large, namely 0, 5, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90% RH), establish a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity, substitute the characteristic frequency offset values ​​and relative humidity under all relative humidities into the coordinate system, and form a standard curve.

[0091] (3) In an environment with light and no relative humidity, 20 different carbon dioxide concentrations were prepared. The 21 carbon dioxide concentrations were detected by a gas measurement system to obtain the characteristic frequency-loss curve of the carbon dioxide concentration (such as Fig. 9 a), obtain the characteristic frequency offset value of each carbon dioxide concentration through the characteristic frequency-loss curve, (the 20 carbon dioxide concentrations increase from small to large, namely 0, 500, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000 ppm), establish a coordinate system of carbon dioxide concentration and the characteristic frequency offset value under the carbon dioxide concentration, substitute the characteristic frequency offset values ​​and relative humidity under all carbon dioxide concentrations into the coordinate system, and form a standard curve.

[0092] (4) Prepare 20 different carbon dioxide concentrations under light and relative humidity of 40% RH. Use a gas measurement system to detect the 20 carbon dioxide concentrations and obtain the characteristic frequency-loss curve of the carbon dioxide concentration (such as Fig. 9 b), obtain the characteristic frequency offset value of each carbon dioxide concentration through the characteristic frequency-loss curve, (21 carbon dioxide concentrations increase from small to large, namely 0, 500, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000, 6000, 7000 ppm), establish a coordinate system of carbon dioxide concentration and the characteristic frequency offset value under the carbon dioxide concentration, substitute the characteristic frequency offset values ​​and relative humidity under all carbon dioxide concentrations into the coordinate system, and form a standard curve.

[0093] (5) The 17 relative humidities measured in a light-free and carbon dioxide-free environment are used to obtain a standard curve of the characteristic frequency-loss of the relative humidity (e.g. Figure 8 a) and the 17 relative humidities measured in an environment without light and with a carbon dioxide concentration of 2000ppm to obtain the characteristic frequency-loss standard curve of the relative humidity (such as Figure 8 b) Fitting into a straight line (such as Fig.10 ). The sensor's humidity response was tested in the presence and absence of 2000ppm CO2. In the relative humidity range of 0-90%RH, the sensor's humidity response was almost the same with or without the presence of CO2. Obviously, the sensor has no response to CO2 gas in the absence of light.

[0094] (6) The 21 carbon dioxide concentrations measured under light and relative humidity conditions are used to obtain a standard curve of characteristic frequency-loss of the carbon dioxide concentration (e.g. Fig. 9 a) and 21 carbon dioxide concentrations measured under light and relative humidity of 40% RH to obtain the characteristic frequency-loss standard curve of the carbon dioxide concentration (such as Fig. 9 b) Fitting into a straight line (such as Fig.11 ). The CO2 gas response of the sensor in a relative humidity of 40% RH and zero humidity environment. Regardless of the presence or absence of humidity, the frequency shift of the sensor response to CO2 is almost the same in the CO2 concentration range of 0-2000ppm. In the CO2 concentration range of 2000-7000ppm, at a relative humidity of 40% RH, the frequency shift of the sensor is slightly lower than when there are no water molecules, but the frequency shift difference between the two environmental conditions is only 3.3%. The CO2 response experiment was carried out under light conditions. This further confirms that the Au / TiO 2 The surface acoustic wave humidity-carbon dioxide dual response sensor based on PEDOT sensitive film has bidirectional selectivity for water vapor and carbon dioxide, that is, it responds to ambient humidity under lightless conditions and only responds to carbon dioxide gas under light conditions.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An Au / TiO2 / PEDOT sensitive film material, characterized in that: In the Au / TiO2 / PEDOT sensitive membrane material, TiO2 nanoparticles adhere to PEDOT polymers to form a microporous membrane, and TiO2 nanoparticles and Au particles cooperate with each other to make the microporous membrane become a porous membrane; The Au / TiO2 / PEDOT sensitive film material is prepared by the following method: Step 1, dissolving tetrachloroauric acid trihydrate, titanium dioxide and 3-4-ethylenedioxythiophene in a solvent to obtain a mixed solution; Step 2, using the mixed solution as a precursor, performing a photocatalytic reaction, and air-drying to obtain a composite film, namely the Au / TiO2 / PEDOT sensitive film material; or also includes step 3: cleaning the composite film, air-drying again to obtain the Au / TiO2 / PEDOT sensitive film material; or also includes step 4: sticking the Au / TiO2 / PEDOT sensitive film material obtained in step 3 on a tantalum sheet, performing a uniform coating process, and then removing the Au / TiO2 / PEDOT sensitive film material from the tantalum sheet.

2. The Au / TiO2 / PEDOT sensitive film material according to claim 1, characterized in that: The solvent in step 1 is ethanol. In the mixed solution, the concentration of tetrachloroauric acid trihydrate is 0.0005-0.001 mol L-1, the concentration of titanium dioxide is 5-10 mg mL-1, and the concentration of 3-4-ethylenedioxythiophene is 50-100 mg mL-1.

3. The Au / TiO2 / PEDOT sensitive film material according to claim 1, characterized in that: The air drying in step 2 is performed in a light box with a high-pressure mercury lamp as the light source, the light source power is 220-230W, the illumination time is 2.5-3 hours, and the air drying time is 30-45 minutes.

4. The Au / TiO2 / PEDOT sensitive film material according to claim 1, characterized in that: In step 3, during cleaning, an alcohol solution is sprayed on the wet film to wash away excess 3-4-ethylenedioxythiophene on the surface of the film that has not been polymerized into a polymer. After cleaning, the film is air-dried for 10 to 20 minutes.

5. The Au / TiO2 / PEDOT sensitive film material according to claim 1, characterized in that: In step 4, the coating includes two processes: low-speed coating and high-speed coating. The uniform speed of the low-speed coating is 1:400-600rad / min, and the time is 5-10s. The uniform speed of the high-speed coating is 2:1500-1800rad / min, and the time is 20-30s.

6. Use of the Au / TiO2 / PEDOT sensitive film material as claimed in any one of claims 1 to 5 in combination with a surface acoustic wave device as a sensor for detecting humidity and carbon dioxide.

7. The use according to claim 6, characterized in that The Au / TiO2 / PEDOT sensitive film material is cut into blocks of a predetermined size and attached to the delay region of a delay line type surface acoustic wave device to detect humidity and carbon dioxide concentration.

8. The use according to claim 7, characterized in that When performing carbon dioxide detection, the detection method includes the following steps: Step 1, establishing a gas measurement system, wherein the Au / TiO2 / PEDOT sensitive film material is attached to a surface acoustic wave device as a carbon dioxide sensor, the sensor is connected to a network analyzer, different carbon dioxide concentrations are prepared under a light environment, the characteristic frequency-loss curve under each carbon dioxide concentration is detected by the sensor, the characteristic frequency offset value of each carbon dioxide concentration is obtained through the characteristic frequency-loss curve, a coordinate system of carbon dioxide concentration and characteristic frequency offset value under carbon dioxide concentration is established, the characteristic frequency offset under different carbon dioxide concentrations and the corresponding carbon dioxide concentration are substituted into the coordinate system to form a standard curve; Step 2, fitting the standard curve into a straight line to obtain a linear regression equation of the straight line, obtaining a loss-characteristic frequency curve of the object to be measured and obtaining a characteristic frequency offset value through the loss-characteristic frequency, substituting the characteristic frequency offset value of the object to be measured into the linear regression equation to obtain the carbon dioxide concentration of the object to be measured.

9. The use according to claim 7, characterized in that When performing humidity detection, the detection method includes the following steps: Step 1, establishing a gas measurement system to simulate the adsorption process, wherein the Au / TiO2 / PEDOT sensitive film material is attached to a surface acoustic wave device as a humidity sensor, the sensor is connected to a network analyzer, different relative humidity is prepared in a lightless environment, and the characteristic frequency-loss curve under each relative humidity is detected by the humidity sensor. During the detection, the relative humidity increases from small to large to simulate the adsorption process, and the characteristic frequency offset value of each relative humidity is obtained through the characteristic frequency-loss curve, a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity is established, and the characteristic frequency offset values ​​under different relative humidity and the corresponding relative humidity are substituted into the coordinate system to form an adsorption standard curve; Step 2, establishing a gas measurement system to simulate the desorption process, wherein the Au / TiO2 / PEDOT sensitive film is attached to a surface acoustic wave device as a humidity sensor, the sensor is connected to a network analyzer, different relative humidities are prepared in a lightless environment, and the characteristic frequency-loss curve under each relative humidity is detected by the humidity sensor. During the detection, the relative humidity decreases from large to small to simulate the desorption process, and the characteristic frequency offset value of each relative humidity is obtained through the characteristic frequency-loss curve, a coordinate system of relative humidity and the characteristic frequency offset value under the relative humidity is established, and the characteristic frequency offset values ​​under different relative humidities and the corresponding relative humidity are substituted into the coordinate system to form a desorption standard curve; Step 3, fit the adsorption standard curve and the desorption standard curve into a straight line to obtain the linear regression equation of the straight line, obtain the characteristic frequency-loss curve of the object to be measured and obtain the characteristic frequency offset value through the characteristic frequency-loss curve, substitute the characteristic frequency offset value of the object to be measured into the linear regression equation to obtain the relative humidity of the object to be measured.

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