A method for preparing rGO-SnO2 nanocomposite material in a strong alkaline liquid environment

Abstract

This invention relates to a method for preparing rGO-SnO2 nanocomposites in a strongly alkaline liquid environment, belonging to the field of nanomaterials. The method involves adding SnCl4·5H2O and NaOH to a GO dispersion and stirring for 10–30 min to obtain a strongly alkaline liquid environment with a pH of 8–13.94. The obtained strongly alkaline liquid is then subjected to a hydrothermal reaction at 180–200 °C for 10–20 h. The product is then centrifuged, washed, and dried, and heat-treated at 600 °C at a rate of 10 °C / min for 2–6 h under an Ar atmosphere to obtain the rGO-SnO2 nanocomposites. This invention effectively solves the problems of difficult SnO2 material growth and low yield in strongly alkaline environments, as well as the low sensitivity and poor long-term stability of traditional gas-sensitive materials for detecting NO2, by using GO as a substrate and preparing rGO-SnO2 nanocomposites via a hydrothermal method. It has good application value and development prospects.

Description

Technical Field

[0001] The invention relates to a method for preparing an rGO-SnO2 nanocomposite material in a strong alkaline liquid environment, and belongs to the field of nanomaterials. Background Art

[0002] The preparation of a large number of nanomaterials needs to be prepared in an alkaline environment. In the preparation of SnO2 materials in an alkaline environment, an alkali-resistant oxide ceramic material substrate is usually used. In the prior art, a technology for growing SnO2 in an alkaline environment using indium tin oxide as a substrate has been proposed (for example, see non-patent document 1: J. Yan, M. Xu, F. Zhang, et al. Hydrothermal synthesis and photoluminescence properties of SnO2 nanowire array and pinecone-like nanoparticles on ITO substrate, Materials Letters, 165 (2016) 243-246.). Non-patent document 1 discloses a technology for growing SnO2 in an alkaline environment using indium tin oxide as a substrate.

[0003] Semiconductor gas-sensitive materials such as SnO2 often need to grow in an alkaline environment, but traditional substrates are usually not resistant to strong alkalis, and the price of alkali-resistant oxide ceramic material substrates is relatively high. In addition, the above-mentioned substrates are macroscopic substrates with small surface areas, and the transfer of prepared materials is complicated, which is not suitable for preparing gas-sensitive materials. Therefore, the development of methods for preparing nanomaterials in a strong alkaline environment has become one of the focuses of gas sensor research. For example, the indium tin oxide substrate introduced in non-patent document 1 can provide a small surface area for nucleation sites, and the transfer of SnO2 grown on its surface is difficult. If this substrate is used to prepare SnO2 gas-sensitive materials, the material preparation process will be complicated and the sensor cost will be high. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing rGO-SnO2 nanocomposite materials in a strong alkaline liquid environment, and another purpose of the present invention is to provide a gas-sensitive material for NO2 sensing. The present invention adopts a hydrothermal method to prepare rGO-SnO2 nanocomposite materials with large specific surface area, uniform morphology, good dispersibility, and large yield using GO as a substrate, and has excellent NO2 sensing performance. When GO dispersion liquid is not added, due to the lack of nucleation sites, only a trace amount of uncollectible SnO2 is generated on the wall of the reactor; when a single crystal silicon wafer or a glass wafer is used as a substrate, a strong alkaline solution corrodes the single crystal silicon wafer and the glass wafer, resulting in product contamination; using GO as a substrate can grow SnO2 nanomaterials in a strong alkaline liquid environment, and GO is reduced to rGO and SnO2 in the subsequent Ar atmosphere heat treatment process to form a rGO-SnO2 nanocomposite material.

[0005] A method for preparing an rGO-SnO2 nanocomposite material in a strong alkaline liquid environment comprises the following steps: adding SnCl4·5H2O and NaOH to a GO dispersion and stirring for 10 to 30 minutes to obtain a strong alkaline liquid, wherein the strong alkaline liquid environment is a liquid environment with a pH value of 8 to 13.94; subjecting the obtained strong alkaline liquid to a hydrothermal reaction at 180 to 200° C. for 10 to 20 hours, then centrifuging, washing, and drying the product, heating the product to 600° C. at a rate of 10° C. / min in an Ar gas atmosphere, and heat treating the product for 2 to 6 hours to obtain the rGO-SnO2 nanocomposite material.

[0006] Preferably, the solid content of the GO dispersion is 0.5-5 mg / mL.

[0007] Preferably, the molar ratio of SnCl4·5H2O to NaOH is 1:10 to 1:12.

[0008] Preferably, the mass ratio of GO to SnCl4·5H2O is 1:100 to 4:100.

[0009] Preferably, the centrifugal speed is 4000-6000 r / min.

[0010] Preferably, the washing is to centrifugally wash the product with ethanol and deionized water for 2 to 3 times respectively.

[0011] Preferably, the drying is to place the washed solid product in an oven at a temperature of 50 to 100° C. and dry it for 10 to 20 hours.

[0012] Another object of the present invention is to provide an rGO-SnO2 nanocomposite material prepared by the above method.

[0013] A rGO-SnO2 nanocomposite material, wherein the rGO-SnO2 nanocomposite material uses graphene oxide as an alkali-resistant substrate to provide nucleation sites for the growth of SnO2; the rGO-SnO2 nanocomposite material is composed of SnO2 square nanorods with a diameter of 80 to 100 nm and a length of 500 to 600 nm, which are assembled into micron flowers and grown on rGO, and the SnO2 square nanorods are of a tetragonal cassiterite phase structure.

[0014] Another object of the present invention is to provide a method for preparing a NO2 gas sensor using the above-mentioned rGO-SnO2 nanocomposite material.

[0015] A method for preparing a NO2 gas sensor based on rGO-SnO2 nanocomposite material comprises the following steps:

[0016] ① Place the rGO-SnO2 nanocomposite material in deionized water to form a uniform slurry;

[0017] ② The slurry obtained in step ① is dripped onto the interdigital electrodes to form a coating with a thickness of 100 to 300 μm, and after natural drying, the coating is aged at 175 to 200° C. for 2 to 4 hours to form a gas sensor;

[0018] Preferably, in step ①, the ratio of the rGO-SnO2 nanocomposite material to deionized water is 10-50 mg: 100-200 μL

[0019] The NO2 gas sensor prepared by the above method has a detection range of 0.05 to 5 ppm for NO2 gas and an operating temperature of 25 to 200°C.

[0020] Preferably, the working temperature is 110-130°C.

[0021] The beneficial effects of the present invention are as follows: the present invention uses GO as a substrate to prepare a rGO-SnO2 nanocomposite material with a large specific surface area, uniform morphology, good dispersibility, and large yield in a strong alkaline environment through a hydrothermal method, and has excellent NO2 sensing performance. The rGO-SnO2 nanocomposite material is used as a gas-sensitive coating to prepare a NO2 gas sensor. The gas sensor has a sensitivity of 1750 to 1850 to 1ppm NO2 gas at an operating temperature of 110 to 130°C, a response and recovery time of 230 to 250s and 10 to 15s, respectively, a NO2 detection lower limit of 0.05ppm, and has good selectivity and long-term stability. The preparation of rGO-SnO2 nanocomposite materials by a hydrothermal method using GO as a substrate effectively solves the problems of the difficulty of growing SnO2 materials in a strong alkaline environment, low yield, and low sensitivity and poor long-term stability of traditional gas-sensitive materials in detecting the presence of NO2, and has good application value and development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is attached Fig. 9 Size:

[0023] Figure 1 This is the SEM photograph of the rGO-SnO2 nanocomposite material described in Example 1. It can be seen that the obtained rGO-SnO2 nanocomposite material contains rGO and SnO2 square nanorods with a diameter of 80-100 nm and a length of 500-600 nm assembled into micro-flowers. The rGO-SnO2 nanocomposite material has good dispersibility.

[0024] Figure 2 This is the XRD spectrum of the rGO-SnO2 nanocomposite material described in Example 1. It can be seen that the diffraction peak of the rGO-SnO2 nanocomposite material matches that of tetragonal cassiterite SnO2 (JCPDS#41-1445).

[0025] Figure 3 TEM image of the rGO-SnO2 nanocomposite material described in Example 1. Figure 3 (a) It can be seen that the SnO2 square nanorods in the rGO-SnO2 nanocomposite material are assembled into micron-flower shapes, with a diameter of 80-100nm and a length of 500-600nm.

[0026] Figure 4 The response-recovery curves of the rGO-SnO2 nanocomposite material to 1 ppm NO2 at different working temperatures of Example 1 show that the rGO-SnO2 nanocomposite material has a significant response to NO2 within the working range of 25-200°C. It can be further seen that the resistance of the rGO-SnO2 nanocomposite material increases rapidly after each injection of NO2. When the test cavity is opened, its resistance recovers rapidly with the assistance of heating.

[0027] Figure 5 The sensitivity of the rGO-SnO2 nanocomposite material to 1 ppm NO2 described in Example 1 varies with the operating temperature. It can be seen that the optimal operating temperature of the rGO-SnO2 nanocomposite material is 125°C.

[0028] Figure 6 These are four consecutive response-recovery curves of the rGO-SnO2 nanocomposite material to 1 ppm NO2 as described in Example 1. It can be seen that the resistance of the rGO-SnO2 nanocomposite material increases rapidly after each injection of NO2 and the four resistance changes are similar, indicating that the response of the rGO-SnO2 nanocomposite material to NO2 has good reproducibility.

[0029] Figure 7(a) is the response-recovery curve of the rGO-SnO2 nanocomposite material to 0.05-5 ppm NO2 described in Example 1. It can be seen that after each injection of NO2, PtSn x -The resistance of the rGO-SnO2 nanocomposite material increases rapidly. When the test chamber is opened, its resistance recovers rapidly under the assistance of heating, and when the assistance of heating ends, its resistance returns to the initial value. The sensitivity of the rGO-SnO2 nanocomposite material to 0.05-5 ppm NO2 changes with the NO2 concentration as shown in Figure 2. Figure 7 (b) as shown.

[0030] Figure 8 From the sensitivity of the rGO-SnO2 nanocomposite material in Example 1 to different gases, it can be seen that the sensitivity of the rGO-SnO2 nanocomposite material to 1 ppm NO2 is 3 orders of magnitude higher than that to other toxic optimized gases, indicating that it has good selectivity in response to NO2.

[0031] Fig. 9 This is the change in response of the rGO-SnO2 nanocomposite material described in Example 1 to 1ppm NO2 within 100 days. It can be seen that the resistance change of the rGO-SnO2 nanocomposite material in response to 1ppm NO2 within 100 days is relatively consistent, and the response / recovery speed has no obvious change, indicating that the rGO-SnO2 nanocomposite material has good long-term stability in response to NO2. DETAILED DESCRIPTION

[0032] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0033] The test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0034] The preparation method of the rGO-SnO2 nanocomposite material of the present invention comprises the following specific steps: adding SnCl4·5H2O and NaOH to a GO dispersion and stirring for 10 to 30 minutes to obtain a mixed solution; subjecting the obtained mixed solution to a hydrothermal reaction at 180 to 200° C. for 10 to 20 hours, then centrifuging, washing and drying the product, heating it to 600° C. at 10° C. / min in an Ar atmosphere, and heat treating it for 2 to 6 hours to obtain the rGO-SnO2 nanocomposite material.

[0035] The preparation method of the NO2 gas sensor based on rGO-SnO2 nanocomposite material specifically includes the following steps:

[0036] ① placing the rGO-SnO2 nanocomposite material in deionized water to form a uniform slurry, wherein the ratio of the rGO-SnO2 nanocomposite material to the deionized water is 10-50 mg: 100-200 μL;

[0037] ② The slurry obtained in step ① is dripped onto the interdigital electrodes to form a coating with a thickness of 100 to 300 μm, and after natural drying, the coating is aged at 175 to 200° C. for 2 to 4 hours to form a gas sensor;

[0038] The NO2 gas sensor of the rGO-SnO2 nanocomposite material prepared by the above method has a detection range of 0.05 to 5 ppm for NO2 gas and an operating temperature of 25 to 200°C.

[0039] Embodiment 1:

[0040] The preparation method of the rGO-SnO2 nanocomposite material of the present invention comprises the following specific steps: adding 3mmol SnCl4·5H2O and 35mmol NaOH to 40mL GO dispersion (2.5mg / mL) and stirring for 30min to obtain a mixed solution; subjecting the obtained mixed solution to a hydrothermal reaction at 200°C for 16h, then centrifuging, washing and drying the product, heating to 600°C at 10°C / min in an Ar atmosphere, and heat treating for 4h to obtain the rGO-SnO2 nanocomposite material.

[0041] The SEM image of the rGO-SnO2 nanocomposite material described in this embodiment is as follows Figure 1 As shown, it can be seen that the obtained rGO-SnO2 nanocomposite material is SnO2 square nanorods with a diameter of 80-100 nm and a length of 500-600 nm assembled into micro-flowers and grown on rGO, and the rGO-SnO2 nanocomposite material has good dispersibility.

[0042] The XRD spectrum of the rGO-SnO2 nanocomposite material described in this embodiment is as follows Figure 2 As shown, it can be seen that the diffraction peak of the rGO-SnO2 nanocomposite matches that of tetragonal cassiterite phase SnO2 (JCPDS#41-1445).

[0043] The TEM image of the rGO-SnO2 nanocomposite material described in this embodiment is as follows Figure 3 As shown, from Figure 3 (a) It can be seen that the SnO2 square nanorods in the rGO-SnO2 nanocomposite material are assembled into micron-flower shapes, with a diameter of 80-100nm and a length of 500-600nm.

[0044] The preparation method of the NO2 gas sensor based on rGO-SnO2 nanocomposite material specifically includes the following steps:

[0045] ① placing the rGO-SnO2 nanocomposite material in deionized water to form a uniform slurry, wherein the ratio of the rGO-SnO2 nanocomposite material to deionized water is 40 mg:100 μL;

[0046] ② The slurry obtained in step ① is dripped onto the interdigital electrode to form a coating with a thickness of 200 μm, and after natural drying, it is aged at 200° C. for 4 h to form a gas sensor;

[0047] The NO2 gas sensor of the rGO-SnO2 nanocomposite material prepared by the above method has a detection range of 0.05 to 5 ppm for NO2 gas and an operating temperature of 25 to 200°C.

[0048] The response-recovery curves of the rGO-SnO2 nanocomposite material to 1 ppm NO2 at different working temperatures are shown in FIG. Figure 4 As shown, it can be seen that the rGO-SnO2 nanocomposite material has a significant response to NO2 in the working range of 25-200°C. It can be further seen that the resistance of the rGO-SnO2 nanocomposite material increases rapidly after each injection of NO2. When the test cavity is opened, its resistance recovers rapidly with the assistance of heating.

[0049] The sensitivity of the rGO-SnO2 nanocomposite material to 1 ppm NO2 varies with the operating temperature as shown in the following figure: Figure 5 As shown, it can be seen that the optimal working temperature of the rGO-SnO2 nanocomposite material is 125°C.

[0050] The response-recovery curves of the rGO-SnO2 nanocomposite material to 1 ppm NO2 for four consecutive times are shown in FIG. Figure 6 As shown, it can be seen that the resistance of the rGO-SnO2 nanocomposite material increases rapidly after each injection of NO2 and the four resistance changes are similar, indicating that the rGO-SnO2 nanocomposite material has good reproducibility in response to NO2.

[0051] The response-recovery curve of the rGO-SnO2 nanocomposite material to 0.05-5 ppm NO2 is as follows: Figure 7 As shown, it can be seen that after each injection of NO2, PtSn x-The resistance of the rGO-SnO2 nanocomposite material increases rapidly. When the test chamber is opened, its resistance recovers rapidly under the assistance of heating, and when the assistance of heating ends, its resistance returns to the initial value. The sensitivity of the rGO-SnO2 nanocomposite material to 0.05-5 ppm NO2 changes with the NO2 concentration as shown in Figure 2. Figure 7 (b) as shown.

[0052] The sensitivity of the rGO-SnO2 nanocomposite material to different gases is as follows: Figure 8 As shown, it can be seen that the sensitivity of the rGO-SnO2 nanocomposite material to 1 ppm NO2 is 3 orders of magnitude higher than that to other toxic optimized gases, indicating that it has good selectivity in response to NO2.

[0053] The changes in the response of the rGO-SnO2 nanocomposite material to 1 ppm NO2 within 100 days are as follows: Fig. 9 As shown, it can be seen that the resistance change of the rGO-SnO2 nanocomposite material in response to 1ppm NO2 is relatively consistent within 100 days, and the response / recovery speed has no obvious change, indicating that the rGO-SnO2 nanocomposite material has good long-term stability in response to NO2.

[0054] Example 2

[0055] The preparation method of the rGO-SnO2 nanocomposite material of the present invention comprises the following specific steps: adding 3mmol SnCl4·5H2O and 35mmol NaOH to 40mL GO dispersion (2mg / mL) and stirring for 30min to obtain a mixed solution; subjecting the obtained mixed solution to a hydrothermal reaction at 180°C for 16h, then centrifuging, washing and drying the product, heating to 600°C at 10°C / min in an Ar atmosphere, and heat treating for 4h to obtain the rGO-SnO2 nanocomposite material.

[0056] The preparation method of the NO2 gas sensor based on rGO-SnO2 nanocomposite material specifically includes the following steps:

[0057] ① placing the rGO-SnO2 nanocomposite material in deionized water to form a uniform slurry, wherein the ratio of the rGO-SnO2 nanocomposite material to deionized water is 40 mg:100 μL;

[0058] ② The slurry obtained in step ① is dripped onto the interdigital electrode to form a coating with a thickness of 200 μm, and after natural drying, it is aged at 200° C. for 4 h to form a gas sensor;

[0059] The NO2 gas sensor of the rGO-SnO2 nanocomposite material prepared by the above method has a detection range of 0.05 to 5 ppm for NO2 gas and an operating temperature of 25 to 200°C.

[0060] Example 3

[0061] The preparation method of the rGO-SnO2 nanocomposite material of the present invention comprises the following specific steps: adding 3mmol SnCl4·5H2O and 35mmol NaOH to 40mL GO dispersion (3mg / mL) and stirring for 30min to obtain a mixed solution; subjecting the obtained mixed solution to a hydrothermal reaction at 180°C for 10h, then centrifuging, washing and drying the product, heating to 600°C at 10°C / min in an Ar atmosphere, and heat treating for 4h to obtain the rGO-SnO2 nanocomposite material.

[0062] The preparation method of the NO2 gas sensor based on rGO-SnO2 nanocomposite material specifically includes the following steps:

[0063] ① placing the rGO-SnO2 nanocomposite material in deionized water to form a uniform slurry, wherein the ratio of the rGO-SnO2 nanocomposite material to deionized water is 40 mg:100 μL;

[0064] ② The slurry obtained in step ① is dripped onto the interdigital electrode to form a coating with a thickness of 200 μm, and after natural drying, it is aged at 200° C. for 4 h to form a gas sensor;

[0065] The NO2 gas sensor of the rGO-SnO2 nanocomposite material prepared by the above method has a detection range of 0.05 to 5 ppm for NO2 gas and an operating temperature of 25 to 200°C.

[0066] Comparative Example 1

[0067] In this comparative example, GO was not added. The specific steps were as follows: 3 mmol SnCl4·5H2O and 35 mmol NaOH were added to 40 mL of deionized water and stirred for 30 min to obtain a mixed solution; the obtained mixed solution was hydrothermally reacted at 200°C for 16 h, and then the product was centrifuged, washed, and dried. Since GO dispersion was not added, there was a lack of nucleation sites, and only a trace amount of uncollectible SnO2 was generated on the wall of the reactor, and the yield was very small and could not be used to prepare gas sensors.

[0068] Comparative Example 2

[0069] In this comparative example, the single crystal silicon wafer is used as the substrate, and the specific steps are as follows: 3 mmol SnCl4·5H2O and 35 mmol NaOH are added to 40 mL of deionized water and stirred for 30 min to obtain a mixed solution; 1×2 cm single crystal silicon wafer is added to the mixed solution, and hydrothermally reacted at 200°C for 16 h, and then the product is centrifuged, washed, and dried. Since the strong alkaline solution corrodes the single crystal silicon wafer, the single crystal silicon wafer is completely dissolved after hydrothermal reaction, resulting in contamination of the product.

Claims

1. A method for preparing rGO-SnO2 nanocomposite materials in a strong alkaline liquid environment, characterized in that: The rGO-SnO2 nanocomposite material uses graphene oxide as an alkali-resistant substrate to provide nucleation sites for the growth of SnO2; the rGO-SnO2 nanocomposite material is composed of SnO2 square nanorods with a diameter of 80 to 100 nm and a length of 500 to 600 nm assembled into micron flowers and grown on rGO; the SnO2 square nanorods are of a tetragonal cassiterite phase structure. The material is prepared by the following method: SnCl4·5H2O and NaOH are added to a GO dispersion and stirred for 10 to 30 minutes to obtain a strong alkaline liquid, wherein the strong alkaline liquid environment is a liquid environment with a pH of 13.94; the obtained strong alkaline liquid is subjected to a hydrothermal reaction at 180 to 200° C. for 10 to 20 hours, and then the product is centrifuged, washed, and dried, and the temperature is increased to 600° C. at 10° C. / min in an Ar gas atmosphere, and after heat treatment for 2 to 6 hours, an rGO-SnO2 nanocomposite material is obtained.

2. The material according to claim 1, characterized in that The solid content of the GO dispersion is 0.5-5 mg / mL.

3. The material according to claim 1, characterized in that The molar ratio of SnCl4·5H2O to NaOH is 1:10 to 1:

12.

4. The material according to claim 1, characterized in that The mass ratio of GO to SnCl4·5H2O is 1:100 to 4:

100.

5. A method for preparing a NO2 gas sensor based on the rGO-SnO2 nanocomposite material according to claim 1, characterized in that: The steps include: ① Place the rGO-SnO2 nanocomposite material in deionized water to form a uniform slurry; ② The slurry obtained in step ① is dripped onto the interdigital electrodes to form a coating with a thickness of 100 to 300 μm. After natural drying, the coating is aged at 175 to 200° C. for 2 to 4 hours to form a gas sensor.

6. The method according to claim 5, characterized in that In the step ①, the ratio of the rGO-SnO2 nanocomposite material to deionized water is 10-50 mg: 100-200 μL.

7. The NO2 gas sensor obtained by the method of claim 5, characterized in that: The gas sensor has a detection range of 0.05 to 5 ppm for NO2 gas and an operating temperature of 25 to 200°C.

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