Preparation method of GO / SiO2 humidity-sensitive material, humidity-sensitive material and humidity sensor

Abstract

The application relates to the technical field of humidity sensors, and particularly discloses a preparation method of a GO / SiO2 humidity-sensitive material, a humidity-sensitive material and a humidity sensor. The preparation method of the GO / SiO2 humidity-sensitive material comprises the following preparation steps: S1. providing SiO2 microspheres; S2. modifying the surface of the SiO2 microspheres by using PDDA to obtain modified SiO2 microspheres; and S3. wrapping the modified SiO2 microspheres by using GO to obtain a GO / SiO2 humidity-sensitive material. The humidity sensor prepared from the humidity-sensitive material has the characteristics of selectivity to water molecules, high sensitivity, fast response and recovery speed, and can be applied to agricultural humidity detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of humidity sensors, and more particularly to a preparation method of a GO / SiO2 humidity-sensitive material, a humidity-sensitive material and a humidity sensor. BACKGROUND

[0002] With the rapid development of modern agriculture, real-time acquisition of agricultural information is of great significance for understanding the current situation of agricultural production, improving the efficiency of agricultural production, and realizing the automation, informatization and high efficiency of the agricultural production process. Water-saving irrigation and sprinkling irrigation are two important agricultural production methods that affect crop growth by changing the humidity of the planting environment. Since humidity plays a crucial role in crop growth, it is necessary to quickly and accurately detect agricultural humidity. However, in actual farmland, the traditional humidity detection method is manual monitoring, which leads to inconvenient operation, time-consuming and low accuracy. In addition, manual detection can cause humidity data collection delay. In intelligent agriculture, new technologies such as the Internet of Things, big data analysis and unmanned aerial vehicles are applied to capture a large amount of humidity data, which are then used for decision-making. In particular, the combination of the Internet of Things and wireless sensor networks has become a promising trend for intelligent agricultural humidity data collection. Among them, the sensor, as the terminal for detecting agricultural humidity in the entire Internet of Things system, is indispensable for the rapid detection of humidity data. However, there are many interfering gases in the actual agricultural environment, such as oxygen (O2), ammonia (NH3), nitrogen dioxide (NO2), carbon dioxide (CO2), carbon monoxide (CO), etc. Therefore, it is still challenging for the sensor to quickly and sensitively detect humidity in the presence of interfering gases.

[0003] Due to the importance of humidity detection, many studies have been devoted to developing sensors with fast response, high sensitivity and selectivity. Currently, few humidity sensors can simultaneously meet these three characteristics. For example, cellulose nanofiber composite carbon nanotube (CNT) paper-based humidity sensors are considered a low-cost method for detecting humidity, however, the response / recovery time of these humidity sensors is as long as several hundred seconds, with slow response speed. Metal composite polymer nanomaterials, such as halide perovskite CsPbBr3 nanoparticles, chitosan / ZnO / single-walled CNT composites, and cellulose / KOH composite ion membranes, are applied to humidity sensors, which have a response speed of only a few seconds, but the sensitivity of these sensors is relatively low. New applications of SnS2 nanoflower / rGO, nitrogen-doped rGO fibers, etc. can manufacture humidity sensors with fast response and high sensitivity, however, these sensors lack selectivity.

[0004] In summary, how to prepare a humidity sensor with fast response / recovery, high sensitivity and selectivity at the same time still needs to be explored. SUMMARY

[0005] The application aims to provide a preparation method of GO / SiO2 humidity-sensitive material, a humidity-sensitive material and a humidity sensor, so that the prepared humidity sensor has the characteristics of fast response / recovery, high sensitivity and selectivity.

[0006] In a first aspect, the application provides a preparation method of GO / SiO2 humidity-sensitive material, which adopts the following technical scheme:

[0007] The preparation method of GO / SiO2 humidity-sensitive material comprises the following preparation steps:

[0008] S1. providing SiO2 microspheres;

[0009] S2. modifying the SiO2 microspheres by PDDA to obtain modified SiO2 microspheres;

[0010] S3. wrapping the modified SiO2 microspheres by GO to obtain GO / SiO2 humidity-sensitive material.

[0011] Optionally, step S1 comprises the following preparation steps:

[0012] S1-1. adding anhydrous ethanol, ammonia water and deionized water in a reaction container, and stirring to obtain a mixed solution;

[0013] S1-2. adding tetraethyl orthosilicate in the mixed solution, stirring and reacting;

[0014] S1-3. after the reaction is completed, centrifugal separation is performed, the precipitate is collected, washed and dried to obtain SiO2 microspheres.

[0015] Optionally, the volume ratio of the anhydrous ethanol, ammonia water, deionized water and tetraethyl orthosilicate in step S1 is (100-600):(80-300):(80-350):(25-100).

[0016] Optionally, step S2 comprises the following preparation steps:

[0017] S2-1. dispersing the SiO2 microspheres in deionized water to form a SiO2 microsphere suspension;

[0018] S2-2. dispersing PDDA in deionized water to form a PDDA solution;

[0019] S2-3. mixing the SiO2 microsphere suspension and the PDDA solution to react;

[0020] S2-4. after the reaction is completed, centrifugal separation is performed, the precipitate is collected, washed and dried to obtain modified SiO2 microspheres.

[0021] Optionally, step S3 comprises the following preparation steps:

[0022] S3-1. Disperse GO sheets in deionized water to form a GO solution;

[0023] S3-2. Disperse the modified SiO2 microspheres in deionized water to obtain a uniformly dispersed modified SiO2 microsphere suspension, slowly add the modified SiO2 microsphere suspension to the GO solution under ultrasonic treatment, and then continue ultrasonic treatment to react, so that the GO wraps the modified SiO2 microspheres;

[0024] S3-3. After the reaction is completed, centrifugal separation is performed, the precipitate is collected, washed and dried to obtain a GO / SiO2 humidity-sensitive material.

[0025] Optionally, the ratio of the average particle size of the GO sheets to the average particle size of the modified SiO2 microspheres in step S3 is 40-500 nm: 200-800 nm.

[0026] Optionally, the concentration of the GO solution is 0.01-2 mg / mL, the concentration of the modified SiO2 microsphere suspension is 2-50 mg / mL, and the volume ratio of the amount of the GO solution to the amount of the modified SiO2 microsphere suspension is 1-100: 1-100.

[0027] In a second aspect, the present application provides a GO / SiO2 humidity-sensitive material obtained by the above-mentioned method for preparing a GO / SiO2 humidity-sensitive material.

[0028] In a third aspect, the present application provides a humidity sensor comprising the above-mentioned GO / SiO2 humidity-sensitive material.

[0029] Optionally, the humidity sensor is prepared by the following steps:

[0030] S4. Disperse the GO / SiO2 humidity-sensitive material in deionized water to obtain a GO / SiO2 suspension;

[0031] S5. Drop the GO / SiO2 suspension onto a chip, dry it into a film, and prepare a humidity sensor.

[0032] In summary, the present application has at least one of the following beneficial effects:

[0033] 1. The preparation method of the GO / SiO2 humidity-sensitive material provided by the application has simple preparation process and is easy to control, the surface of SiO2 microspheres is modified by PDDA to make the surface of the SiO2 microspheres have positive charges, the surface of GO sheets has negative charges, therefore, the GO / SiO2 humidity-sensitive material can realize self-assembly under electrostatic force to form a specific structure, the GO sheets are wrapped on the surface of the SiO2 microspheres to obtain a composite structure, the structure of the SiO2 microspheres can inhibit the aggregation of water droplets, the curved surface can promote the evaporation of water molecules, and the stacking of the GO sheets can also be inhibited, so that the fast response / recovery is realized, and the response / recovery speed of the GO / SiO2 humidity sensor can reach 0.24-2.76s / 0.73-4.81s, preferably, can reach 0.24-1.08s / 0.73-1.93s, and more preferably, can reach 0.24-0.48s / 0.73-0.96s.

[0034] 2. The humidity sensor comprising the GO / SiO2 humidity-sensitive material provided by the application also has the characteristics of high sensitivity and high selectivity, the humidity sensor shows high sensitivity of 1.2-4.2% per %RH in the relative humidity range of 11%-95%, and the humidity sensor shows selectivity to water molecules due to the hydrophilic property of GO and the significant increase in ionic transmission conductivity.

[0035] 3. The humidity sensor provided by the application can be applied to agricultural humidity detection, and can realize 0.8-1.2Hz analog drip irrigation humidity detection and 4-10Hz unmanned aerial vehicle detection. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 (a) is a scanning electron microscope image of SiO2 particles prepared in Preparation Example 1; (b) is a scanning electron microscope image of GO / SiO2 humidity-sensitive material prepared in Preparation Example 1; (c) is a Raman spectrum of GO / SiO2 humidity-sensitive material prepared in Preparation Example 1.

[0037] Figure 2 is a scanning electron microscope image of GO / SiO2 humidity-sensitive material prepared in Comparative Preparation Example 3.

[0038] Figure 3 is a scanning electron microscope image of GO / SiO2 humidity sensor prepared in Comparative Preparation Example 5.

[0039] Figure 4 (a) is a repeatability test of the GO / SiO2 humidity sensor prepared in Example 1 on a modulated humid nitrogen gas flow; (b) is a single test response curve of the GO / SiO2 humidity sensor on a modulated humid nitrogen gas flow.

[0040] Figure 5(a) are response curves of GO / SiO2 humidity sensors prepared in Examples 1-4 and Comparative Example 1; (b) are recovery time and response time of GO / SiO2 humidity sensors.

[0041] Figure 6 (a) are response curves of GO / SiO2 humidity sensors prepared in Examples 1 and Comparative Examples 2, 3; (b) are recovery time and response time of GO / SiO2 humidity sensors.

[0042] Figure 7 (a) are response curves of GO / SiO2 humidity sensors prepared in Examples 1 and Comparative Example 4; (b) are response curves of GO / SiO2 humidity sensors prepared in Examples 1 and Comparative Example 5.

[0043] Figure 8 are real-time video snapshots of water adsorption and desorption on the surface of GO / SiO2 humidity-sensitive material (a-c) and pure GO sheets (d-f) of Example 1: (a) start; (b) 8 min; (c) end: 15 min 53 s; (d) start; (e) 2 min; (f) end: 3 min 53 s.

[0044] Figure 9 (a) are resistance of GO / SiO2 humidity sensor of Example 1 in the humidity range of 11% RH to 95% RH; (b) are complex impedance spectra of GO / SiO2 humidity sensor of Example 1 at different test frequencies in the humidity range of 11% RH to 95% RH; (c) are adsorption models of water molecules on the surface of GO / SiO2 humidity sensor of Example 1 in the humidity range of 11% RH to 95% RH.

[0045] Figure 10 (a) are selective measurements of GO / SiO2 humidity sensor of Example 1 for H2O, O2, NH3, NO2, CO2 and CO; (b) are corresponding AR / R0 of humidity sensor in (a).

[0046] Figure 11 is a flow chart of application of GO / SiO2 humidity sensor of Application Example 1 and Application Example 2 to agricultural humidity detection.

[0047] Figure 12 (a) is a schematic diagram of the device and sensor employed in Application Example 1 and Application Example 2 for agricultural humidity detection and remote wireless transmission on mobile phone and computer terminal; (b) is a simulated process of water dripping and (c) is a practical process of agricultural field humidity detection and display process simulated by a drone.

[0048] Figure 13(a) is the response curve of the GO / SiO2 humidity sensor analog drop process detection frequency of 0.8H Z of application example 1; (b) the response curve of the GO / SiO2 humidity sensor analog unmanned aerial vehicle detection process detection frequency of 4H Z of application example 2. DETAILED DESCRIPTION

[0049] In recent years, graphene oxide (GO) has been considered as a promising humidity-sensitive material due to its hydrophilicity and high specific surface area. However, the stacking phenomenon between GO sheets can affect its adsorption performance. In our previous work (Li J. et al., 2021. “Gold particles decorated reduced graphene oxide for low level mercury vapor detection with rapid response at room temperature”. Ecotoxicology and Environmental Safety, 228, 112995.), the insertion of gold particles into graphene sheets can shorten the response / recovery time. This indicates that the addition of new structures in graphene sheets can inhibit their laminated stacking, which is an effective method to improve the detection performance of sensors. On this basis, the applicant has surprisingly found that the SiO2 microsphere structure can further improve the response / recovery speed of GO sheets, and has thus developed a GO / SiO2 humidity-sensitive material based on GO wrapped SiO2 microsphere structure. The humidity sensor prepared by using the GO / SiO2 humidity-sensitive material has fast response / recovery, high sensitivity and selectivity at room temperature.

[0050] The present application provides a preparation method of a GO / SiO2 humidity-sensitive material, comprising the following preparation steps:

[0051] S1. providing SiO2 microspheres, step S1 comprising the following preparation steps:

[0052] S1-1. adding anhydrous ethanol, ammonia water and deionized water in a reaction container, stirring uniformly to obtain a mixed solution;

[0053] S1-2. adding tetraethyl orthosilicate in the mixed solution, stirring and reacting;

[0054] S1-3. after the reaction is completed, centrifugal separation is performed, the precipitate is collected, washed and dried to obtain SiO2 microspheres.

[0055] The volume ratio of anhydrous ethanol, ammonia, deionized water and tetraethyl orthosilicate in step S1 is (100-600):(80-300):(80-350):(25-100); preferably (200-400):(100-300):(150-300):(30-80); more preferably (300-350):(150-250):(200-380):(45-70); even more preferably (310-330):(180-220):(230-260):(50-70). Through long-term experimental research, the applicant discovered that SiO2 microspheres with specific particle sizes can be obtained by adjusting the volume ratio of anhydrous ethanol, ammonia, deionized water, and tetraethyl orthosilicate. The particle size ratio of GO sheets to SiO2 microspheres significantly affects the response / recovery performance, sensitivity, and selectivity of the GO / SiO2 humidity-sensitive material. The average particle size of the SiO2 microspheres prepared in this invention is [missing information].

[0056] The average particle size is 100 nm to 1 μm, preferably 200 to 800 nm, more preferably 400 to 800 nm, and even more preferably 400 to 600 nm.

[0057] S2. Surface modification of the SiO2 microspheres using PDDA (polydiallyl dimethyl ammonium chloride) to obtain modified SiO2 microspheres. Step S2 includes the following preparation steps:

[0058] S2-1. Disperse the SiO2 microspheres in deionized water to form a SiO2 microsphere suspension;

[0059] S2-2. Disperse PDDA in deionized water to form a PDDA solution;

[0060] S2-3. Mix the SiO2 microsphere suspension with the PDDA solution and react;

[0061] S2-4. After the reaction is complete, centrifuge to separate the precipitate, collect it, wash and dry it to obtain modified SiO2 microspheres.

[0062] Specifically, in step S2, the concentration of the SiO2 microsphere suspension is 1–100 mg / mL, preferably 5–20 mg / mL, the concentration of the PDDA solution is 1–100 mg / mL, preferably 5–20 mg / mL, and the volume ratio of the SiO2 microsphere suspension to the PDDA solution is 10–100:10–100. By adjusting the concentration of the SiO2 microsphere suspension and the concentration and volume ratio of the PDDA solution, the surface of the SiO2 microspheres is modified to obtain a suitable positive charge without changing the structure of the SiO2 microspheres. The modified SiO2 microspheres maintain the same average particle size as the pure SiO2 microspheres.

[0063] S3. The GO is used to wrap the modified SiO2 microspheres to obtain a GO / SiO2 humidity-sensitive material, and step S3 includes the following preparation steps:

[0064] S3-1. The GO sheets are dispersed in deionized water to form a GO solution;

[0065] S3-2. The modified SiO2 microspheres are dispersed in deionized water to obtain a uniformly dispersed modified SiO2 microsphere suspension, and the modified SiO2 microsphere suspension is slowly added to the GO solution under ultrasonic treatment, and then ultrasonic treatment is continued to react, so that the GO wraps the modified SiO2 microspheres;

[0066] S3-3. After the reaction is completed, centrifugal separation is performed, the precipitate is collected, washed and dried to obtain a GO / SiO2 humidity-sensitive material.

[0067] In step S3, the ratio of the average particle size of the GO sheets to the modified SiO2 microspheres is 40-500 nm: 200-800 nm; more preferably 50-300 nm: 200-800 nm; more preferably 100-200 nm: 400-800 nm, more preferably 100-200 nm: 400-600 nm. The particle size of the GO sheets and the modified SiO2 microspheres is matched, so that the GO sheets can be better wrapped on the surface of the modified SiO2 microspheres to form a specific composite structure.

[0068] In step S3, the concentration of the GO solution is 0.01-2 mg / mL; preferably 0.1-0.5 mg / mL. The concentration of the modified SiO2 microsphere suspension is 2-50 mg / mL; preferably 5-20 mg / mL. The volume ratio of the use amount of the GO solution to the modified SiO2 microsphere suspension is 1-100: 1-100. By using a specific range of the concentration of the GO solution, the concentration of the modified SiO2 microsphere suspension and the volume ratio, the GO and the modified SiO2 microspheres can be well contacted, and the electrostatic force between the GO sheets and the modified SiO2 microspheres makes the GO sheets wrap the surface of the modified SiO2 microspheres to form a specific structure of the GO / SiO2 humidity-sensitive material.

[0069] In addition to electrostatic binding, no chemical binding occurs between the GO sheets and the modified SiO2 microspheres, so that the GO retains its own characteristics, has hydrophilicity and high specific surface area, the modified SiO2 microspheres change the curvature of the GO wrapped on the surface, improve the evaporation rate of the micro water droplets on the GO surface, and inhibit the stacking of the GO, thereby improving the response and recovery speed.

[0070] The application provides a humidity sensor prepared from the GO / SiO2 humidity-sensitive material. The humidity sensor prepared from the GO / SiO2 humidity-sensitive material with the specific structure of the application has a response / recovery speed of 0.24-2.76s / 0.73-4.81s, preferably 0.24-1.08s / 0.73-1.93s, and more preferably 0.24-0.48s / 0.73-0.96s. Meanwhile, the GO / SiO2 humidity sensor also has the characteristics of high sensitivity and high selectivity, and the humidity sensor shows a high sensitivity of 1.2-4.2 / %RH in the relative humidity range of 11%-95%, preferably 1.4-4.2 / %RH, more preferably 1.6-4.2 / %RH, more preferably 1.9-4.2 / %RH, and more preferably 2.3-4.2 / %RH. Due to the hydrophilic property of GO and the significant increase in ion transmission conductivity, the humidity sensor shows unique selectivity to water molecules compared with oxygen (O2), ammonia (NH3), nitrogen dioxide (NO2), carbon dioxide (CO2) and carbon monoxide (CO). Therefore, the humidity sensor can be applied to agricultural humidity detection. The detection results show that 0.8-1.2Hz analog drip irrigation humidity detection and 4-10Hz unmanned aerial vehicle detection can be realized.

[0071] The application provides a humidity sensor comprising the GO / SiO2 humidity-sensitive material.

[0072] The humidity sensor is prepared by the following steps:

[0073] S4. dispersing the GO / SiO2 humidity-sensitive material into deionized water to obtain a GO / SiO2 suspension;

[0074] S5. dropping the GO / SiO2 suspension onto a chip and drying into a film to prepare the humidity sensor.

[0075] The concentration of the specific GO / SiO2 suspension is 0.1-50mg / mL, preferably 0.5-20mg / mL, and more preferably 1-5mg / mL. The above range of the concentration of the suspension is conducive to forming a uniform humidity detection film. The unit area dosage of the GO / SiO2 suspension is 5μL-500μL / 10mm*10mm chip area, preferably 5μL-200μL / 10mm*10mm chip area, more preferably 5μL-100μL / 10mm*10mm chip area, and more preferably 15μL-75μL / 10mm*10mm chip area. The above specific range of the dosage can obtain relatively fast response speed and recovery speed. The application is described in detail below in combination with examples.

[0076] Example

[0077] Preparation Example 1

[0078] S1. Preparation of SiO2 microspheres:

[0079] S1-1. Add 320 mL of anhydrous ethanol, 200 mL of ammonia water (25-28 wt / %) and 240 mL of deionized water into a flask, stir for 10 minutes, then mix uniformly to obtain a mixed solution;

[0080] S1-2. Add 60 mL of tetraethyl orthosilicate (TEOS, Aladdin, T110593-500 mL) into the mixed solution, and stir for 4 hours at a stirring speed of 1040 r / min;

[0081] S1-3. After the stirring reaction is completed, the precipitate is collected by centrifugal separation, and washed with deionized water and anhydrous ethanol alternately for three times, and dried at 60°C for 12 h to obtain SiO2 particles.

[0082] Figure 1 (a) is a scanning electron microscope image of the SiO2 particles prepared in S1-3. It can be seen from Figure 1 that the SiO2 particles are microspheres, uniform in size and good in dispersibility, and the average particle size of the SiO2 microspheres is 500 nm.

[0083] S2. PDDA-modified SiO2 microspheres:

[0084] S2-1. Take 1 g of SiO2 microspheres prepared in step S1 and ultrasonically disperse them in 100 mL of deionized water for 30 min at a power of 160 W to form a SiO2 microsphere suspension with a concentration of 10 mg / mL;

[0085] S2-2. Take 1 g of polydiallyldimethylammonium chloride (PDDA, Macklin, P816116-500 mL) and stir-disperse it in 100 mL of deionized water for 10 min at a stirring speed of 1040 r / min to form a polydiallyldimethylammonium chloride solution with a concentration of 10 mg / mL;

[0086] S2-3. Mix the entire SiO2 microsphere suspension prepared in S2-1 with the entire polydiallyldimethylammonium chloride solution prepared in step S2-2 under ultrasonic action for 30 min at a power of 160 W to obtain a mixture;

[0087] S2-4. Stir the mixture obtained in S2-3 for 12 h at a stirring speed of 1040 r / min, and after the reaction is completed, centrifugal separation is performed, the precipitate is collected, and washed with deionized water repeatedly for three times, and dried at 60°C for 12 h to obtain PDDA-modified SiO2 microspheres.

[0088] S3. GO-coated modified SiO2 microspheres, preparation of GO / SiO2 humidity-sensitive material:

[0089] S3-1. 40 mg of micro- GO sheets (purchased from JCNO Technology Co., Ltd. (Nanjing, China), average particle size less than 200 nm) were ultrasonically dispersed in 200 mL of deionized water to form a uniform GO solution with a concentration of 0.2 mg / mL, and the ultrasonic time was 45 min and the power was 160 W;

[0090] S3-2. The PDDA-modified SiO2 microspheres prepared in S2-4 were dispersed in deionized water to obtain a uniformly dispersed PDDA-modified SiO2 microsphere suspension with a concentration of 8 mg / mL, and 100 mL of the suspension was slowly added to 100 mL of the GO solution prepared in S3-1 under ultrasonic treatment, the ultrasonic time was 20 min and the power was 160 W, then the same power was maintained and the ultrasonic reaction was continued for 30 min;

[0091] S3-3. After the ultrasonic reaction was completed, centrifugal separation was performed, the precipitate was collected and washed with deionized water three times, and then dried at 60 °C for 12 h to obtain the GO / SiO2 humidity-sensitive material.

[0092] Figure 1 (b) is a scanning electron microscope image of the GO / SiO2 humidity-sensitive material prepared in S3-3. Figure 1 As can be seen from (b), the GO / SiO2 humidity-sensitive material is composed of modified SiO2 microspheres and GO sheets wrapped on the surface of the modified SiO2 microspheres, and there are GO sheets connecting between adjacent modified SiO2 microspheres, and the GO-coated modified SiO2 microspheres have the same average particle size as the pure SiO2 microspheres, which is still 500 nm.

[0093] Figure 1 (c) is the Raman spectrum of the GO / SiO2 humidity-sensitive material prepared, as shown in Figure 1 (c), the GO / SiO2 humidity-sensitive material shows a representative D peak of GO at 1333 cm -1 and a G peak at 1600 cm -1 .

[0094] Therefore, from these characterization results, it can be proved that the micro- GO sheets are successfully self-assembled on the surface of the PDDA-modified SiO2 microspheres. Since the GO sheet surface is negatively charged and the PDDA-modified SiO2 microspheres are positively charged, the GO / SiO2 humidity-sensitive material can be self-assembled under electrostatic force, so that the GO sheets are wrapped on the surface of the SiO2 microspheres to form a composite structure, and the unmodified SiO2 microspheres cannot be self-assembled with the GO sheets to form a composite structure.

[0095] Comparative Preparation Example

[0096] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 1 is that the amount of anhydrous ethanol in S1-1 is replaced by 92 mL, the amount of ammonia water (25-28 wt%) is replaced by 1.45 mL, the amount of deionized water is replaced by 17.2 mL, and the amount of tetraethyl orthosilicate (TEOS) in S1-2 is replaced by 3.5 mL. The rest of the preparation steps are the same as those in Preparation Example 1. The average diameter of the SiO2 microsphere particles prepared in S1-3 is measured to be 100 nm.

[0097] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 1 is that the amount of anhydrous ethanol in S1-1 is replaced by 650 mL, the amount of ammonia water (25-28 wt%) is replaced by 60 mL, the amount of deionized water is replaced by 67.5 mL, and the amount of tetraethyl orthosilicate (TEOS) in S1-2 is replaced by 23 mL. The average diameter of the SiO2 microsphere particles prepared in S1-3 is measured to be 1 μm.

[0098] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 1 is that the micro GO sheets in S3-1 are replaced by large GO sheets with an average diameter of 2 μm (manufacturer: Xianfeng Nanometer, model number: XF224). The rest of the preparation steps are the same as those in Preparation Example 1. Figure 2 The scanning electron microscope picture of the prepared GO / SiO2 humidity-sensitive material can be seen from FIG. 2, which shows that the SiO2 microspheres are completely wrapped in the large GO sheets, and the surface of the large GO sheets has a wrinkled morphology. Figure 2

[0099] Example 1:

[0100] The GO / SiO2 humidity-sensitive material prepared in Preparation Example 1 is dispersed in deionized water to obtain a uniform suspension with a concentration of 2 mg / mL. An IDE chip (IDE chip model: 50 μm ceramic interdigital electrode IDE capacitance array biological gas humidity sensor chip, chip substrate: alumina ceramic) is used to prepare a humidity sensor. The outer size is 10 mm*10 mm, the line spacing is 50 μm, the line width is 100 μm, the finger length is 7.7 mm, and the interdigital electrode number is 15 pairs (30 fingers). 50 μL of the suspension is dropped onto the interdigital electrode array of the chip, and the unit area dosage of the GO / SiO2 humidity-sensitive material is 50 μL / 10 mm*10 mm chip area. The chip is dried at room temperature and air-cooled to prepare a GO / SiO2 humidity sensor.

[0101] Example 2

[0102] Example 2 is different from Example 1 in that 15 μL of the GO / SiO2 humidity-sensitive material suspension is dropped onto the chip, and the unit area dosage of the GO / SiO2 humidity-sensitive material is 15 μL / 10 mm*10 mm chip area. The rest of the preparation steps are the same as those in Example 1. ​

[0103] Example 3

[0104] Example 3 differs from Example 1 in that 25 μL of the GO / SiO2 humidity-sensitive material suspension is dropped onto the chip, the unit area usage of the GO / SiO2 humidity-sensitive material is 25 μL / 10 mm*10 mm chip area, and the remaining preparation steps are the same as in Example 1.

[0105] Example 4

[0106] Example 4 differs from Example 1 in that 100 μL of the GO / SiO2 humidity-sensitive material suspension is dropped onto the chip, the unit area usage of the GO / SiO2 humidity-sensitive material is 100 μL / 10 mm*10 mm chip area, and the remaining preparation steps are the same as in Example 1.

[0107] Comparative Example 1

[0108] Comparative Example 1 differs from Example 1 in that 200 μL of the GO / SiO2 humidity-sensitive material suspension is dropped onto the chip, the unit area usage of the GO / SiO2 humidity-sensitive material is 200 μL / 10 mm*10 mm chip area, and the remaining preparation steps are the same as in Example 1.

[0109] Comparative Example 2

[0110] Comparative Example 2 differs from Example 1 in that the GO / SiO2 humidity-sensitive material of Comparative Preparation Example 1 is used instead of the GO / SiO2 humidity-sensitive material of Preparation Example 1, and the remaining preparation steps are the same as in Example 1.

[0111] Comparative Example 3

[0112] Comparative Example 3 differs from Example 1 in that the GO / SiO2 humidity-sensitive material of Comparative Preparation Example 2 is used instead of the GO / SiO2 humidity-sensitive material of Preparation Example 1, and the remaining preparation steps are the same as in Example 1.

[0113] Comparative Example 4

[0114] Comparative Example 4 differs from Example 1 in that the GO / SiO2 humidity-sensitive material of Comparative Preparation Example 3 is used instead of the GO / SiO2 humidity-sensitive material of Preparation Example 1, and the remaining preparation steps are the same as in Example 1.

[0115] Comparative Example 5

[0116] Comparative Example 5 differs from Example 1 in that PDDA-modified Si02microspheres prepared in Preparation Example 1 S2-4.1 and micro- GO sheets prepared in Preparation Example 1 S3-1. are separately prepared into PDDA-modified Si02microspheres suspension and GO solution with a concentration of 2 mg / mL, then 25 μL of the prepared PDDA-modified Si02microspheres suspension is dropped onto the chip, and after drying into a film, 25 μL of the prepared GO solution is dropped onto the surface thereof, and dried at room temperature to prepare a humidity sensor.

[0117] Figure 3 The scanning electron microscope picture of the prepared humidity sensor can be seen from Figure 3 , in which the surface of part of the Si02microspheres is overlapped by the GO film.

[0118] Performance test

[0119] In order to evaluate the humidity sensing performance of the GO / Si02humidity sensor, the GO / Si02humidity sensor prepared in Example 1 is placed in a chamber, and a humidified nitrogen gas flow (humidity of 62% RH) is flown over the surface of the GO / Si02humidity sensor at a constant flow rate at room temperature, and the resistance response of the humidity sensor is recorded, and the corresponding resistance measurement curve is shown in Figure 4 , the response of the sensor to the modulated humidified nitrogen flow repeats multiple cycles within 300 seconds, and the results are shown in Figure 4 (a), and it is found that the resistance response has little change, which clearly indicates that the prepared GO / Si02humidity sensor has high repeatability at room temperature. Figure 4 (b) is Figure 4 (a), and from Figure 4 (b), it can be seen that when the humidified nitrogen gas flows in, the resistance of the humidity sensor immediately decreases, and then, after the humidified nitrogen gas flow is turned off, the resistance of the sensor quickly returns to its initial value. The response and recovery times are usually used to define the speed of resistance change, the response time is defined as the time required to reach 90% of its stable value, and the recovery time is the time required for the equilibrium resistance to return to 10% of the initial value after the target humidified gas is released. As shown in the experimental results in Figure 4 (b), the GO / Si02humidity sensor has a fast response and recovery speed, and the response and recovery times are 0.24 s and 0.73 s, respectively.

[0120] The same test method as in Example 1 is used to test the performance of the sensors of Examples 2-4 and Comparative Example 1, and the results of Examples 1-4 and Comparative Example 1 are normalized, as shown in Figure 5 (a), and in addition, Figure 5 (a), the response times and recovery times of the five response curves in Figure 5(b) shows the counting and display. Specifically, the response / recovery times of the five sensors with doses of 15μL, 25μL, 50μL, 100μL, and 200μL were 0.48s / 0.95s, 0.36s / 0.96s, 0.24s / 0.73s, 1.08s / 1.93s, and 2.76s / 4.81s, respectively. It can be found that when the amount of GO / SiO2 humidity-sensitive material is small (15μL~50μL / 10mm*10mm chip area), the difference in response and recovery times among the GO / SiO2 humidity sensors is relatively small. The response and recovery times decrease with the increase of the amount of GO / SiO2 humidity-sensitive material. When the amount of GO / SiO2 humidity-sensitive material per unit area is 50μL / 10mm*10mm chip area, the response and recovery speeds reach their optimal levels. The main reason is that with the increase in the amount of GO-coated SiO2 microspheres, the adsorption sites on the surface of the humidity-sensitive material increase. Therefore, the resistance change of the humidity sensor with a unit area of ​​50 μL / 10mm*10mm chip area is greater than that with 15 μL / 10mm*10mm and 25 μL / 10mm*10mm chip areas. However, with the continuous increase in the amount of GO / SiO2 humidity-sensitive material, compared with the unit area of ​​50 μL / 10mm*10mm chip area, the humidity sensors with a unit area of ​​100 μL / 10mm*10mm and 200 μL / 10mm*10mm chip area show a significant increase in response and recovery times. In particular, the response / recovery speed of the humidity sensor with a unit area of ​​200 μL / 10mm*10mm chip area is significantly slower. The main reason for this is that the film thickness on the surface of the GO / SiO2 humidity sensor is too thick, which cannot suppress the adsorption and desorption of water on the surface of the humidity sensor, leading to a decrease in the performance of the humidity sensor. It is evident that humidity sensors with a unit area usage of 15μL to 100μL / 10mm*10mm chip area exhibit faster response and recovery speeds, especially those with a unit area usage of 15μL to 50μL / 10mm*10mm chip area, which demonstrate even better response and recovery performance.

[0121] The performance of the sensors in Comparative Examples 2 and 3 was tested using the same test method as in Example 1, and the results of Example 1 and Comparative Examples 2 and 3 were normalized, as follows: Figure 6 As shown in (a), in addition... Figure 6 The response times and recovery times of the three response curves in (a) are... Figure 6(b) were counted and displayed. Specifically, the response / recovery times of the humidity sensors prepared by using the GO / SiO2 humidity-sensitive material prepared by using SiO2 microspheres with an average diameter of 100 nm and 1 μm were 1.56 s / 3.64 s and 2.5 s / 3.02 s, respectively, which were compared with the response time and the recovery time of the humidity sensors of Comparative Examples 2 and 3, which were prepared by using SiO2 microspheres with an average diameter of 500 nm. The response time and the recovery time of the humidity sensors of Comparative Examples 2 and 3 were greatly increased. The main reason was that, although the microspheres of 100 nm in Comparative Example 2 had a larger curvature, the micro GO sheets were not well wrapped on the surface of the microspheres, but were stacked in a large area, thereby reducing the response and recovery speed. In Comparative Example 3, the curvature of the 1 μm microspheres was smaller, which reduced the evaporation rate of water, and also reduced the response and recovery speed. It can be seen that, by matching the particle size of the GO sheets and the modified SiO2 microspheres, and by using a specific particle size ratio of the GO sheets and the modified SiO2 microspheres, the GO sheets can be better wrapped on the surface of the modified SiO2 microspheres, and the GO / SiO2 humidity-sensitive material prepared thereby has a better response and recovery speed.

[0122] The performance of the sensors of Comparative Examples 4 and 5 was tested by using the same test method as in Example 1, and the results of Example 1 and Comparative Examples 4 and 5 were compared, as shown in Figure 7 (a) and Figure 7 (b). Figure 7 In (a), compared with the GO / SiO2 humidity-sensitive material of Example 1 which used micro GO sheets, the GO / SiO2 humidity-sensitive material of Comparative Example 4 used large GO sheets, and the response / recovery times of the GO / SiO2 humidity sensor of Comparative Example 4 were 1.44 s / 2.77 s. Figure 7 In (b), compared with the GO / SiO2 humidity-sensitive material of Example 1 which used micro GO sheets to wrap SiO2 microspheres, the surfaces of part of the SiO2 microspheres of Comparative Example 5 were overlapped by GO films, and the response / recovery times of the humidity sensor were 0.85 s / 2.65 s. It can be proved by Comparative Examples 4 and 5 that the GO / SiO2 humidity sensor prepared in Example 1 has a faster response and recovery speed and a larger resistance increment. This is due to the structural differences of the sensitive materials of these humidity sensors, i.e., the structure of the micro GO sheets wrapped SiO2 microspheres shows a larger curvature, while the structure of the GO overlapped SiO2 microspheres and the large GO sheets coated SiO2 microspheres has no curvature. Since the structure of the sensitive material with a large curvature can promote the evaporation of water molecules, the micro GO sheet wrapped SiO2 microsphere sensor prepared in Example 1 shows a higher response and recovery performance in humidity detection than the large GO sheet coated SiO2 microsphere sensor of Comparative Example 4 and the GO overlapped SiO2 microsphere sensor of Comparative Example 5.

[0123] To visually display the adsorption and desorption processes and demonstrate the high performance of the prepared GO / SiO2 humidity sensor, the GO / SiO2 humidity-sensitive material prepared in Example 1 and the micro GO sheet of Preparation Example 1 were respectively configured into a GO / SiO2 humidity-sensitive material suspension with a concentration of 2 mg / mL and a pure GO sheet solution with a concentration of 2 mg / mL, each was dropped onto the surface of a silicon wafer, and air-cooled dried at room temperature. The surface change processes of the two materials were recorded when a continuous nitrogen stream with high humidity was blown onto the surface of the GO / SiO2 humidity-sensitive material and the pure GO sheet, respectively.

[0124] Real-time video snapshots of three time nodes of the adsorption and desorption processes were taken, respectively, as shown in Figure 8 (a-c) are real-time video snapshots of water adsorption and desorption on the surface of the GO / SiO2 humidity-sensitive material, and (d-f) are real-time video snapshots of water adsorption and desorption on the surface of the pure GO. From Figure 8 (a-c), it can be observed that no water droplets were formed on the surface of the GO / SiO2 humidity-sensitive material during the process of continuously flowing high-humidity nitrogen for more than 15 minutes. In contrast, from Figure 8 (d-f), it can be observed that water droplets began to form and adsorb on the surface of the pure GO in a short time. As shown in Figure 8 (d), the pure GO sheet is a two-dimensional planar structure with a small amount of wrinkles on the surface, and these microdroplets accumulate and coalesce into large droplets, as shown in Figure 8 (e). When the high-humidity nitrogen continues to flow, the water droplets continue to accumulate, and eventually completely cover the surface of the pure GO, as shown in Figure 8 (f). Compared with the planar structure of the pure GO, the evaporation rate of water on the surface of the GO / SiO2 humidity-sensitive material is much higher than that of the pure GO, resulting in Figure 8 (a-c), no obvious water droplets were formed on the surface of the GO-coated modified SiO2 microspheres of the GO / SiO2 humidity-sensitive material. At the same time, the evaporation rate of the sensitive film surface depends on the diameter of the spheres, and the numerical simulation and humidity experiment show that the evaporation rate is inversely proportional to the diameter of the spheres in the process of water evaporation on the surface of the spheres, and the diameter of the spheres is inversely proportional to the curvature. As a planar structure, the diameter of the pure GO sheet is approximately infinite, which means that the curvature of the GO-coated SiO2 microsphere structure of the GO / SiO2 humidity-sensitive material is greater than that of the pure GO sheet. Therefore, water molecules evaporate faster on the surface of the GO-coated SiO2 microspheres, so that no obvious water droplets are formed on the surface of the GO-coated SiO2 microspheres. From this, the reason for the fast recovery performance of the GO / SiO2 humidity sensor is derived, and it is speculated that the fast response performance is due to the inhibition of GO stacking by the SiO2 microspheres.

[0125] In order to explore the sensitivity characteristics of the humidity sensor, the resistance of the GO-coated SiO2 microsphere sensor of Example 1 was tested in the range of 11% relative humidity to 95% relative humidity, and the corresponding results are shown in Figure 9The resistance of the humidity sensor of Example 1 decreases with the increase of humidity, which can be observed from Figure 9(a). The sensitivity of the humidity sensor is defined as follows:

[0126]

[0127] where R 11％RH is the resistance at 11% relative humidity; R X％RH is the resistance at X% relative humidity; RH X％ is X% relative humidity, RH 11％ is 11% relative humidity.

[0128] It can be calculated that the sensitivity of the GO / SiO2humidity sensor is 1.2% / %RH-4.2% / %RH in the range of 11%RH-95%RH. The highest sensitivity of 4.2% / %RH is reached at 33%RH, and the sensitivity gradually decreases with the increase of relative humidity; the sensitivity is 2.3 / %RH at 54%RH, 1.9 / %RH at 62%RH, 1.6 / %RH at 75%RH, 1.4 / %RH at 85%RH, and 1.2 / %RH at 95%RH.

[0129] In addition, in order to further study the response mechanism of the sensor, the electrical response process of the GO / SiO2humidity-sensitive material of Example 1 in the water molecule adsorption process is analyzed, and the complex impedance characteristics of the GO / SiO2humidity sensor under different humidity conditions are tested, as shown in Figures 9(b) and 9(c). Figure 9 It can be found that the complex impedance curves of the GO / SiO2humidity sensor of Example 1 corresponding to each humidity are very different, indicating that the water molecule adsorption and ion transport mechanisms are different under different humidity conditions. Specifically, the frequency range of the scan is 1Hz-200KHz, and the excitation signal amplitude is 0.2V. The complex impedance of the humidity sensor of Example 1 is represented as follows:

[0130]

[0131] where Re(Z) and Im(Z) represent the real part and the imaginary part of the complex impedance, respectively. In addition, “|Z|” is the modulus of the complex impedance, “arg(Z)” represents the phase difference, and j is the imaginary unit (satisfying j 2 =-1).

[0132] In addition, Figure 9 (c) gives a schematic adsorption model of water molecules on the surface of the GO / SiO2humidity sensor in the humidity range of 11%RH to 95%RH.

[0133] Under low humidity conditions of 11% RH - 33% RH, the corresponding complex impedance spectra are Figure 9 The semicircular curve in (b). Due to the hydrophilic nature of GO sheets, a small amount of water molecules are adsorbed on the surface of the sensing film and form double hydrogen bonds with GO. Due to the restriction of double hydrogen bonds, water molecules cannot move freely. At this time, the conduction mechanism mainly depends on the hopping transfer of protons, as shown in Figure 9 (c). Although the humidity sensor has a higher initial resistance due to the low electron mobility and weak conductivity of GO, the hopping transport of protons can weakly increase its conductivity, resulting in a decrease in the resistance of the sensor.

[0134] As the humidity increases to 54% RH, it can be seen from Figure 13 (b) that the complex impedance curve shows a semicircle connected with a straight line. More water molecules are adsorbed by single hydrogen bonds and then form a series of water molecule layers. These adsorbed water molecules are ionized under the action of the electrostatic field to produce a large number of hydrogen ions (H3O + ) as carriers. Since the binding force of single hydrogen bond is weaker than that of double hydrogen bond, H3O + can move freely through the water layer and produce ion transport, as shown in Figure 13 (c). It is called Grottuss chain reaction mechanism, i.e. Free ion transport can improve the conductivity of the sensing film, making the resistance of the sensor decrease rapidly.

[0135] As the humidity continues to increase to high humidity conditions of 75% RH - 95% RH, it can be observed from Figure 9 (b) that in the complex impedance curve, the semicircle gradually disappears and the straight line gradually lengthens. As shown in Figure 9 (c), a large number of water molecules are not only adsorbed on the surface of the sensing film, but also enter its sheets and expand the interlayer spacing. It can produce more H3O + and enhance ion transport, thereby further enhancing the conductivity of the humidity sensing film. Therefore, the humidity sensor maintains high sensitivity to water molecules and shows a large resistance change under high humidity conditions. In summary, the mechanism from proton hopping transport to increased ion transport indicates that the humidity sensor has high sensitivity in humidity detection. The high sensitivity performance should be attributed to the different sensing mechanisms from hopping transport to increased ion transport, resulting in a significant change in the resistance of the sensor.

[0136] Due to the significant increase in conductivity caused by ion transport, the sensor exhibits excellent selectivity to water molecules. Figure 10 The response of the GO / SiO2 humidity sensor of Example 1 to 500 ppm of different gases commonly used in agriculture, such as O2, NH3, NO2, CO2 and CO, is shown. From Figure 10As observed in (a), the resistance of the GO / SiO2 humidity sensor increases with the detection of O2. We hypothesize that this increase is due to the strong oxidizing properties of O2. Furthermore, the resistance change of the GO / SiO2 humidity sensor is minimal when the target gases detected are NH3, NO2, CO2, and CO. To more clearly compare the sensor's response to different gases, its relative resistance change (ΔR / R0) is shown below. Figure 10 As shown in (b), the ΔR / R0 of H2O is significantly higher than that of other gases, reaching as high as 94%, compared to 14% for O2, 0.2% for NH3, 0.02% for NO2, 2.6% for CO2, and 1.9% for CO. This is attributed to the fact that water molecules, as an electrolyte, can generate H3O. + Therefore, due to the ion conduction mechanism, the sensor's ΔR / R0 is significantly reduced. However, other gases are non-electrolytes, and thus their corresponding ΔR / R0 is lower. Therefore, it can be concluded that the GO / SiO2 humidity sensor prepared in Example 1 exhibits high selectivity as a humidity sensor.

[0137] As shown in Table 1, the humidity sensing performance of the GO / SiO2 humidity sensor of Example 1 is compared with currently reported work. It can be found that the sensor of Example 1 exhibits faster response / recovery performance than most of the listed sensors. Other reported sensors, such as N-rGO, have shorter response / recovery times but lower sensitivity and non-selectivity. It can be found that the sensor prepared in Example 1 exhibits higher sensitivity than N-rGO (0.07% / %RH-0.09% / %RH) sensors, fluorinated graphene (2.2% / %RH) sensors, etc. In summary, the GO / SiO2 humidity sensor prepared in this invention has fast response / recovery, high sensitivity, and high selectivity, making it competitive in humidity detection applications.

[0138] Table 1 compares the performance of the humidity sensor with currently reported work.

[0139]

[0140] Report 1: Zhang DZ, Xu ZY, Yang ZM, et al., 2020. High-performance flexible self-powered tin disulfide nanoflowers / reduced graphene oxide nanohybrid-based humidity sensor driven by triboelectric nanogenerator. NanoEnergy, 67, 104251.

[0141] Report 2: Choi S.J., Yu H.Y., Jang J.S., et al., 2018. Nitrogen-doped single graphene fiber with platinum water dissociation catalyst for wearable humidity sensor. Small, 14, 1703934.

[0142] Report 3: Wu Z.L., Sun X., Guo X.Z., 2021. Development of a rGO-BiVO4 heterojunction humidity sensor with boosted performance. ACS Applied Materials & Interfaces, 13, 27188-27199.

[0143] Due to the high performance of the GO / SiO2 humidity sensor, such as fast response / recovery, high sensitivity and high selectivity, it can be applied to agricultural humidity detection. The humidity detection results can be displayed on the mobile phone terminal or computer terminal through the designed wireless transmission module, realizing remote real-time humidity monitoring. Figure 11 Figure 11 As shown in FIG. 1, the humidity detection device is composed of a front-end data acquisition unit, a wireless transmission unit and a remote wireless data display unit. In the front-end data acquisition process, the integrated constant current source chip (LM234) is used to collect the resistance value of the GO / SiO2 humidity sensor, and the master control chip (STM32F103C8T6 MCU) and the WiFi module (ESP8266) are used to transmit the collected humidity detection results of the GO / SiO2 humidity sensor to the cloud server. In addition, an architecture composed of web and server is adopted, and the display terminal of the remote wireless data unit such as mobile phone terminal or computer terminal can access the cloud server, trigger the humidity sensor to detect humidity and obtain the humidity detection results on the cloud server, so that remote real-time detection can be realized.

[0144] The present application establishes two experimental devices, one is to simulate the humidity detection in agricultural water-saving drip irrigation by using a flow-adjustable dropper, and the other is composed of a controllable humid nitrogen flow and a small chopper, which is used to interrupt the humid flow regularly, simulating the humidity detection of unmanned aerial vehicles in agriculture. The corresponding schematic diagram is shown in FIG. 2(a). Figure 12

[0145] Application Example 1 ​​

[0146] Application Example 1 uses a flow-adjustable dropper to simulate the water-saving drip irrigation in agriculture. The GO / SiO2 humidity sensor and humidity sensing device prepared in Example 1 are applied to humidity detection. The flow rate of the dropper is adjusted to simulate the dripping process. When a drop of water passes through the sensor, the response is monitored. The detection results are shown in Figure 12 (b), which shows that the GO / SiO2 humidity sensor can sensitively capture the water dripping process with a water dripping frequency of 1.2 Hz.

[0147] Figure 13 (a) shows another response curve of the dripping process with a water dripping frequency of 0.8 Hz. The results also show that the GO / SiO2 humidity sensor can sensitively capture the water dripping process with a frequency of 0.8 Hz.

[0148] Application Example 2

[0149] Application Example 2 is composed of a controllable humid nitrogen flow and a small chopper. The chopper is used to interrupt the humid flow periodically. When the blade of the chopper blocks the humid water vapor, the humidity around the sensor will decrease temporarily. Therefore, the frequency of the blade blocking the water vapor is the frequency of the humidity change. In this way, the humidity detection of the unmanned aerial vehicle in agriculture is simulated, as shown in Figure 12 (c), which shows that the GO / SiO2 humidity sensor can sensitively detect the humid flow with a frequency of 10 Hz.

[0150] Figure 13 (b) shows the response curve of the humid flow with a frequency of 4 Hz, which shows that the GO / SiO2 humidity sensor can sensitively capture the humid flow with a frequency of 4 Hz.

[0151] Therefore, it can be proved that the GO / SiO2 humidity sensor prepared in the application can be applied to agricultural humidity detection.

[0152] The above are preferred embodiments of the application, and do not limit the protection scope of the application. Therefore, any equivalent changes made on the basis of the structure, shape, and principle of the application should be covered within the protection scope of the application.

Claims

1. An application of a GO / SiO2 humidity-sensitive material in a humidity sensor, characterized in that: The preparation steps include the following: S1. Provides SiO2 microspheres; S2. The SiO2 microspheres are surface modified using PDDA to obtain modified SiO2 microspheres; S3. The modified SiO2 microspheres are encapsulated with GO to obtain a GO / SiO2 humidity-sensitive material; Step S1 includes the following preparation steps: S1-1. Add anhydrous ethanol, ammonia and deionized water to the reaction vessel and stir until homogeneous to obtain a mixed solution; S1-2. Add tetraethyl orthosilicate to the mixed solution, stir, and react. S1-3. After the reaction is complete, centrifuge to separate the precipitate, collect the precipitate, wash and dry it to obtain SiO2 microspheres; The volume ratio of anhydrous ethanol, ammonia, deionized water and tetraethyl orthosilicate in step S1 is (100-600):(80-300):(80-350):(25-100). Step S3 includes the following preparation steps: S3-1. Disperse GO tablets in deionized water to form a GO solution; S3-2. The modified SiO2 microspheres are dispersed in deionized water to obtain a uniformly dispersed modified SiO2 microsphere suspension. The modified SiO2 microsphere suspension is slowly added to the GO solution under ultrasonic treatment, and then ultrasonic treatment is continued to carry out the reaction, so that the GO encapsulates the modified SiO2 microspheres. S3-3. After the reaction is complete, centrifuge to separate the precipitate, collect the precipitate, wash and dry it to obtain the GO / SiO2 humidity-sensitive material; In step S3, the average particle size ratio of the GO sheet to the modified SiO2 microspheres is 100~200nm:400~600nm; the concentration of the GO solution is 0.01~2mg / mL; the concentration of the modified SiO2 microsphere suspension is 2~50mg / mL; and the volume ratio of the GO solution to the modified SiO2 microsphere suspension is 1~100:1~100. The GO / SiO2 humidity-sensitive material is dispersed in deionized water to obtain a GO / SiO2 suspension. The GO / SiO2 suspension is dropped onto a chip and dried to form a film to prepare a humidity sensor. The concentration of the GO / SiO2 suspension is 1-5 mg / mL, and the amount of GO / SiO2 suspension used per unit area is 15 μL-50 μL / 10 mm * 10 mm chip area.

2. The application of the GO / SiO2 humidity-sensitive material according to claim 1 in a humidity sensor, characterized in that: Step S2 includes the following preparation steps: S2-1. Disperse the SiO2 microspheres in deionized water to form a SiO2 microsphere suspension; S2-2. Disperse PDDA in deionized water to form a PDDA solution; S2-3. Mix the SiO2 microsphere suspension with the PDDA solution and react them; S2-4. After the reaction is complete, centrifuge to separate the precipitate, collect it, wash and dry it to obtain modified SiO2 microspheres.

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