A resistive gas sensor for hydrazine hydrate detection and preparation method thereof

Abstract

A resistive gas sensor for hydrazine hydrate detection and a preparation method thereof, comprising a single crystal silicon substrate, silicon dioxide layers provided on both sides of the single crystal silicon substrate, gold interdigital electrodes provided on the silicon dioxide layer on one side, a gas sensitive material film provided on the surfaces of the silicon dioxide layer and the gold interdigital electrodes, the gas sensitive material film being composed of a metal oxide / conductive polymer binary composite material; the single crystal silicon substrate, the silicon dioxide layer, and the gold interdigital electrodes together forming a sensor chip; the resistance of the gas sensitive material film changes before and after contact with a gas to be measured, i.e., hydrazine hydrate, and the relevant performance of the sensor response value is obtained by measuring the change in resistance between the gold interdigital electrodes; the present invention has the advantages of simplicity, high response, and good stability.

Description

Technical Field

[0001] The invention belongs to the technical field of gas sensing, and in particular relates to a resistance-type gas sensor for hydrazine hydrate detection and a preparation method thereof. Background Art

[0002] Hydrazine hydrate (N2H4·H2O) is a liquid at room temperature and is widely used in industry, medicine, and other fields as a reducing agent and antioxidant. However, it is highly toxic and volatile at room temperature, making it prone to poisoning and even fires and explosions during storage, transportation, sampling, and processing.

[0003] Currently, there are many methods for detecting hydrazine hydrate, such as gas chromatography, electrochemical analysis, high-performance liquid chromatography, and capillary electrophoresis. However, these traditional methods are complex and expensive, and most of them rely on liquid-phase detection of hydrazine hydrate, making it difficult to directly detect hydrazine hydrate in the gas phase. Exploring a simple, highly responsive, and stable method for detecting hydrazine hydrate gas is of great practical significance. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the object of the present invention is to provide a resistive gas sensor for hydrazine hydrate detection and a preparation method thereof, which has the advantages of simplicity, high response and good stability.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A resistive gas sensor for hydrazine hydrate detection comprises a single crystal silicon substrate 1, wherein silicon dioxide layers 2 are provided on both sides of the single crystal silicon substrate 1, gold interdigital electrodes 3 are provided on the silicon dioxide layer 2 on one side, and a gas sensitive material film 4 is provided on the surfaces of the silicon dioxide layer 2 and the gold interdigital electrodes 3. The gas sensitive material film 4 is composed of a metal oxide / conductive polymer binary composite material. The single crystal silicon substrate 1, the silicon dioxide layer 2, and the gold interdigital electrodes 3 together constitute a sensor chip. The resistance of the gas sensitive material film 4 changes before and after contact with the gas to be measured, i.e., hydrazine hydrate. The performance related to the sensor response value is obtained by measuring the change in resistance between the gold interdigital electrodes.

[0007] The gas sensitive material film 4 is composed of a metal oxide / conductive polymer binary composite material, specifically a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas sensitive material film, and is prepared by a drop coating method.

[0008] The gas sensitive material film 4 is formed by a physical mixture of titanium dioxide nanoparticles and poly 3-hexylthiophene-2,5-diyl in a mass ratio of 1:1. The purity of poly 3-hexylthiophene-2,5-diyl is ≥90% and the average molecular weight is 10,000 to 100,000. The average particle size of the titanium dioxide nanoparticles is 20 to 40 nm.

[0009] The method for preparing a resistive gas sensor for hydrazine hydrate detection comprises the following steps:

[0010] Step 1: Prepare the sensor chip: Thermally oxidize both sides of a single-crystal silicon substrate 1 to form a silicon dioxide layer 2 on the surface. Then, through processes such as coating, UV exposure, development, hardening, electron beam evaporation deposition, and metal stripping, gold interdigital electrodes 3 are formed on one side of the silicon dioxide layer 2. The single-crystal silicon substrate 1, silicon dioxide layer 2, and gold interdigital electrodes 3 together constitute the sensor chip. The surface of the sensor chip is ultrasonically cleaned with ethanol and water in sequence, and then dried for later use.

[0011] Step 2, prepare titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion: weigh 1-25 mg titanium dioxide nanoparticles and 5 mg poly (3-hexylthiophene-2,5-diyl) into a brown reagent bottle, add 5 ml chloroform, and sonicate for 30 minutes;

[0012] Step 3, preparing a gas sensitive material film 4: using a drop coating method to form a film, using a pipette to take 0.5-2 μl of the titanium dioxide / poly 3-hexylthiophene-2,5-diyl chloroform dispersion, and drop it vertically on the sensor chip in step 1 to form a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas sensitive material film on the surface;

[0013] Step 4: Heat the titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material resistance-type gas sensor prepared above at 70°C for 3 hours to completely evaporate the solvent chloroform, thereby obtaining a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material resistance-type gas sensor.

[0014] The beneficial effects of the present invention are:

[0015] 1. The present invention selects poly (3-hexylthiophene-2,5-diyl) from the conductive polymer material, which has a high response to hydrazine hydrate at room temperature and strong environmental stability, and is easy to prepare and modify. In addition, compared with unbranched polythiophene, it has better dispersibility in solvents such as chloroform and tetrahydrofuran, providing good conditions for compounding with other materials.

[0016] 2. Since the polythiophene used mainly conducts electricity through positively charged holes and has P-type semiconductor characteristics, and titanium dioxide mainly conducts electricity through negatively charged electrons and has N-type semiconductor characteristics, the composite of polythiophene and titanium dioxide can form a heterojunction between the two materials. When the sensor is exposed to a certain concentration of hydrazine hydrate, the lone pair electrons in the hydrazine hydrate molecules will interact with the polythiophene to reduce the hole concentration, causing energy band bending at the contact interface, increasing the width of the interface depletion layer, further hindering carrier transport, significantly increasing the resistance of the gas-sensitive film, and improving the sensor response value.

[0017] 3. The present invention uses a physical mixing method to prepare the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) composite gas-sensitive material. The method is simple, easy to operate, and low-cost. The sensing performance of hydrazine hydrate can be controlled simply by adjusting the ratio of the two substances.

[0018] 4. The present invention adopts a drop coating method to prepare a titanium dioxide / poly (3-hexylthiophene-2,5-diyl) composite material resistive gas sensor. The method is simple and easy to operate, and the sensor can be conveniently manufactured, providing good conditions for mass production and processing. It solves the problems of traditional metal oxide gas sensors requiring high-temperature sintering and complex processing, further reducing energy consumption and costs.

[0019] 5. Compared with other hydrazine hydrate sensors, the resistive gas sensor for hydrazine hydrate detection provided in the present invention can directly achieve high-response detection of gas-phase hydrazine hydrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of a gas sensor according to an embodiment of the present invention.

[0021] Figure 2 This is a transmission electron microscope image of the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) composite gas-sensitive material of Example 1 of the present invention.

[0022] Figure 3 This is the X-ray diffraction pattern of the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) composite gas-sensitive material of Example 1 of the present invention.

[0023] Figure 4 This is the dynamic response recovery curve of the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) composite gas-sensitive material resistance-type gas sensor to low-concentration hydrazine hydrate at 25°C in Example 1 of the present invention.

[0024] Figure 5 This is a bar graph showing the response values ​​of the sensor with different amounts (0.5 to 2 μl) of titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion drop-coated according to Examples 1, 2, and 3 of the present invention.

[0025] Figure 6 These are the dynamic response recovery curves of a series of sensors with different contents (1-25 mg) of titanium dioxide nanoparticles in Examples 1, 4, 5, 6, and 7 of the present invention. DETAILED DESCRIPTION

[0026] The following further illustrates a resistive gas sensor for hydrazine hydrate detection and a preparation method thereof according to the present invention in conjunction with the accompanying drawings and examples.

[0027] Example 1, with reference to Figure 1 A resistive gas sensor for hydrazine hydrate detection comprises a single crystal silicon substrate 1, with silicon dioxide layers 2 provided on both sides of the single crystal silicon substrate 1, a gold interdigital electrode 3 provided on the silicon dioxide layer 2 on one side, a gas sensitive material film 4 provided on the surface of the silicon dioxide layer 2 and the gold interdigital electrode 3, the gas sensitive material film 4 being composed of a metal oxide / conductive polymer binary composite material; the single crystal silicon substrate 1 is 500 μm thick, the double-sided silicon dioxide layer 2 is 2 μm thick, the interdigital width of the gold interdigital electrode 3 is 10 μm, the gap between adjacent interdigits is 10 μm, and the thickness of the gold electrode is 75 nm; the resistance of the gas sensitive material film 4 changes before and after contact with the gas to be measured, i.e., hydrazine hydrate, and the performance related to the sensor response value is obtained by measuring the change in resistance between the gold interdigital electrodes;

[0028] The gas sensitive material film 4 is composed of a metal oxide / conductive polymer binary composite material, specifically a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas sensitive material film, and is prepared by a drop coating method;

[0029] The gas sensitive material film 4 is formed by a physical mixture of titanium dioxide nanoparticles and poly 3-hexylthiophene-2,5-diyl in a mass ratio of 1:1. The purity of poly 3-hexylthiophene-2,5-diyl is ≥90% and the average molecular weight is 10,000 to 100,000. The average particle size of the titanium dioxide nanoparticles is 20 to 40 nm.

[0030] The titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material prepared by the present invention was tested by transmission electron microscopy. The results are as follows: Figure 2 As shown, it can be seen that polythiophene is in the form of flakes and titanium dioxide is in the form of round nanoparticles of 20 to 40 nm, and the two are tightly combined;

[0031] The titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material prepared by the present invention was subjected to X-ray diffraction test, and the results were as follows: Figure 3As shown in the image, the three peaks of 5.472°, 16.226°, and 21.908° are characteristic peaks of poly (3-hexylthiophene-2,5-diyl), and the six peaks of 25.431°, 37.905°, 48.165°, 53.757°, 55.192°, and 71.877° are characteristic peaks of titanium dioxide, and the titanium dioxide is anatase titanium dioxide.

[0032] The method for preparing a resistive gas sensor for hydrazine hydrate detection comprises the following specific steps:

[0033] Step 1: Prepare the sensor chip: Thermally oxidize both sides of a single-crystal silicon substrate 1 to form a silicon dioxide layer 2 on the surface. Then, through processes such as coating, UV exposure, development, hardening, electron beam evaporation deposition, and metal stripping, gold interdigital electrodes 3 are formed on one side of the silicon dioxide layer 2. The single-crystal silicon substrate 1, silicon dioxide layer 2, and gold interdigital electrodes 3 together constitute the sensor chip. The surface of the sensor chip is ultrasonically cleaned with ethanol and water in sequence, and then dried for later use.

[0034] Step 2, prepare titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion: weigh 5 mg titanium dioxide nanoparticles and 5 mg poly (3-hexylthiophene-2,5-diyl) into a brown reagent bottle, add 5 ml chloroform, and sonicate for 30 minutes;

[0035] Step 3, preparing a gas sensitive material film 4: using a drop coating method to form a film, using a pipette to suck 1 μl of the titanium dioxide / poly 3-hexylthiophene-2,5-diyl chloroform dispersion, vertically drop it on the sensor chip in step 1 to form a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas sensitive material film on the surface;

[0036] Step 4: Heat the titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material resistance-type gas sensor prepared above at 70°C for 3 hours to completely evaporate the solvent chloroform, thereby obtaining a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material resistance-type gas sensor.

[0037] The performance of the above-mentioned resistive gas sensor was tested using a gas sensitive test system. The response to 29ppm hydrazine hydrate gas at room temperature (25℃) was as follows: Figure 4 As shown in the figure (Response=(R g -R a ) / R a , where Response represents the sensor response value, R a Indicates the baseline resistance of the sensor in air, R g represents the resistance of the sensor in the target gas).

[0038] The results show that the prepared titanium dioxide / poly (3-hexylthiophene-2,5-diyl) composite gas-sensitive material resistive gas sensor has a response value of up to 260.7 to 29ppm hydrazine hydrate gas.

[0039] Example 2: The amount of the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion in step 3 of Example 1 was changed to 0.5 μl, and the other procedures remained the same.

[0040] Example 3: The amount of the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion in step 3 of Example 1 was changed to 2 μl, and the other procedures remained the same.

[0041] Figure 5 The bar graph shows the response values ​​of sensors coated with different amounts (0.5 to 2 μl) of titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion. The graph shows that the response values ​​of the sensors prepared in Example 1, Example 2, and Example 3 are 260.7, 215.2, and 232.5, respectively. By comparison, it can be concluded that the sensor in Example 1 has a better effect.

[0042] Example 4: The amount of titanium dioxide nanoparticles in step 2 of Example 1 was changed to 1 mg, and the other aspects remained the same.

[0043] Example 5: The amount of titanium dioxide nanoparticles in step 2 of Example 1 was changed to 2.5 mg, and the other aspects remained the same.

[0044] Example 6: The amount of titanium dioxide nanoparticles in step 2 of Example 1 was changed to 10 mg, and the other aspects remained the same.

[0045] Example 7: The amount of titanium dioxide nanoparticles in step 2 of Example 1 was changed to 25 mg, and the other aspects remained the same.

[0046] Figure 6 The dynamic response recovery curves of a series of sensors with different contents (1-25 mg) of titanium dioxide nanoparticles are shown in the figure. The dynamic response recovery of the sensors prepared in Example 1, Example 4, Example 5, Example 6, and Example 7 are shown in the figure. By comparison, it can be concluded that the sensor in Example 1 has a better effect (Response = (R g -R a ) / R a , where Response represents the sensor response value, R a Indicates the baseline resistance of the sensor in air, R g represents the resistance of the sensor in the target gas).

[0047] At the same time, the electrode material can also be made of other precious metals including silver or platinum. Since the electrode material needs to be selected according to the sensor design requirements, the preparation details of other materials are not detailed here.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A resistive gas sensor for hydrazine hydrate detection, comprising a single crystal silicon substrate (1), characterized in that: Silicon dioxide layers (2) are provided on both sides of a single crystal silicon substrate (1), a gold interdigital electrode (3) is provided on the silicon dioxide layer (2) on one side, a gas sensitive material film (4) is provided on the surface of the silicon dioxide layer (2) and the gold interdigital electrode (3), and the single crystal silicon substrate (1), the silicon dioxide layer (2) and the gold interdigital electrode (3) together constitute a sensor chip; the resistance of the gas sensitive material film (4) changes before and after contacting the gas to be measured, i.e., hydrazine hydrate, and the performance related to the sensor response value is obtained by measuring the change in the resistance between the gold interdigital electrodes; The gas sensitive material film (4) is composed of a metal oxide / conductive polymer binary composite material, specifically a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas sensitive material film, and is prepared by a drop coating method.

2. A resistive gas sensor for hydrazine hydrate detection according to claim 1, characterized in that: The gas sensitive material film (4) is formed by physically mixing titanium dioxide nanoparticles and poly 3-hexylthiophene-2,5-diyl at a mass ratio of 1:1, the purity of poly 3-hexylthiophene-2,5-diyl is ≥90%, and the average molecular weight is 10,000-100,000; the average particle size of the titanium dioxide nanoparticles is 20-40 nm.

3. The method for preparing a resistive gas sensor for hydrazine hydrate detection according to claim 1, characterized in that: The following steps are involved: Step 1, preparing a sensor chip: thermally oxidizing both sides of a single crystal silicon substrate (1) to form a silicon dioxide layer (2) on the surface, and then performing a process of coating, ultraviolet exposure, development, hardening, electron beam evaporation deposition and metal stripping to obtain a gold interdigital electrode (3) on one side of the silicon dioxide layer (2); the single crystal silicon substrate (1), the silicon dioxide layer (2) and the gold interdigital electrode (3) together constitute a sensor chip, and ultrasonically cleaning the surface of the sensor chip with ethanol and water in sequence, and drying for use; Step 2: Prepare titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion: weigh 1-25 mg titanium dioxide nanoparticles and 5 mg poly (3-hexylthiophene-2,5-diyl) into a brown reagent bottle, add 5 ml chloroform, and sonicate for 30 minutes. Step 3, preparing a gas sensitive material film (4): using a drop coating method to form a film, using a pipette to absorb 0.5-2 μl of the titanium dioxide / poly 3-hexylthiophene-2,5-diyl chloroform dispersion, and drop it vertically on the sensor chip in step 1 to form a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas sensitive material film on the surface; Step 4: Heat the sensor chip with the titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material film formed on the surface at 70° C. for 3 hours to completely evaporate the solvent chloroform, thereby obtaining a titanium dioxide / poly 3-hexylthiophene-2,5-diyl composite gas-sensitive material resistive gas sensor.

4. The method according to claim 3, wherein: In step 2, 5 mg of titanium dioxide nanoparticles and 5 mg of poly (3-hexylthiophene-2,5-diyl) were weighed into a brown reagent bottle; in step 3, 1 μl of the titanium dioxide / poly (3-hexylthiophene-2,5-diyl) chloroform dispersion was aspirated using a pipette.

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