Preparation method and system of indium oxide gas-sensitive material based on bamboo biological template

Abstract

The invention belongs to the technical field of gas sensing, and discloses a preparation method of an indium oxide gas-sensitive material based on a bamboo biological template, which comprises the following steps: taking natural bamboo as a biological structure template, introducing an indium source precursor into a template pore channel by a solution impregnation method, drying, and carrying out high-temperature calcination in an air atmosphere. According to the heat treatment process, thermal degradation and removal of the biological template are achieved, decomposition and oxidation of the precursor are synchronously induced, and finally the indium oxide material with the bamboo biological form and the high specific surface area is generated. The obtained material shows high response and recovery speed to nitrogen dioxide gas, the response value exceeds three thousand, meanwhile, precious metal and a traditional chemical preparation method do not need to be used in the preparation process, and the green chemical concept of saving energy and reducing pollution is achieved.

Description

Technical Field

[0001] This invention belongs to the field of gas sensing technology, and particularly relates to a method and system for preparing indium oxide gas-sensitive materials based on bamboo biotemplates. Background Technology

[0002] Nitrogen dioxide (NO2) is a reddish-brown gas with a pungent odor and is extremely harmful to human health. It is one of the most dangerous pollutants; exposure to levels as low as 3 ppm (parts per million) can cause eye and lung irritation, reduce resistance to respiratory infections, and even be fatal. Furthermore, NO2 can react with other chemicals in the surrounding atmosphere to form acid rain and ozone, causing significant damage to the environment. Therefore, developing a highly sensitive and fast-responding nitrogen dioxide sensor is crucial for both human health and environmental protection.

[0003] Currently, compared to expensive and complex instrumentation methods such as chromatography and fluorescence analysis, which are difficult to implement online, portable gas sensors based on oxide semiconductors have attracted much attention due to their ease of manufacture, high accuracy, and low cost. Therefore, metal oxide NO2 sensors are the main commercially available semiconductor sensors. As a wide-bandgap n-type semiconductor oxide, In2O3 has been considered an ideal sensing material for manufacturing NO2 gas sensors in recent years. It is worth noting that response time, recovery time, and response value are three important indicators for resistive sensors detecting toxic gases. However, most reported In2O3-based sensors still exhibit long response / recovery times when detecting NO2 gas, severely impacting real-time and rapid monitoring in daily life and industrial production. Meanwhile, compared to traditional wet chemical methods (such as sol-gel and hydro(solvothermal) methods), inexpensive, green plant template-assisted synthesis of metal oxide materials exhibits excellent gas-sensing performance. This is mainly because plant biomass-derived nanostructures possess abundant mesopores, a large specific surface area (SSA), and more active sites, effectively increasing the surface transport and adsorption of gas molecules.

[0004] Based on the above analysis, the problems and shortcomings of the existing technology are as follows: Currently, In₂O₃ metal oxide sensors exhibit long response and recovery times and low response values. Traditional chemical preparation methods suffer from drawbacks such as complex processes, high energy consumption, and the use of ultraviolet light and various chemical reagents, which also cause environmental pollution. In particular, the doping of precious metals increases production costs. Therefore, developing a simple, low-cost, reproducible, and environmentally friendly In₂O₃ gas sensor to achieve rapid response and high-sensitivity detection of NO₂ gas remains a challenging task. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing indium oxide gas-sensitive materials based on bamboo biological templates.

[0006] This invention is achieved as follows: a method for preparing an indium oxide gas-sensitive material based on a bamboo biotemplate includes: Step 1: Cut the natural bamboo into slices, heat and clean them in a water bath, then ultrasonically clean them in anhydrous ethanol, and finally soak them in KOH solution.

[0007] Step 2: Wash the bamboo strips thoroughly soaked in KOH solution multiple times until neutral, then transfer them to an oven for drying.

[0008] Step 3: Immerse the treated bamboo strips in an indium nitrate solution to allow them to fully absorb the indium source.

[0009] Step 4: Take out the soaked bamboo strips and dry them in an oven. Place the dried bamboo strips in a muffle furnace and anneal them in an air atmosphere to finally obtain In2O3 powder with a multi-level porous structure of bamboo.

[0010] Furthermore, in step 1, the bamboo strips are cut to a size of 10mm × 10mm, the water bath temperature is 80℃, and the water bath time is 30min.

[0011] Furthermore, in step 1, the ultrasonic time of the bamboo strips in anhydrous ethanol is 1 hour; more preferably, the ultrasonic time for a single session is 0.5 hours, the ethanol solution is replaced and the ultrasonic treatment is repeated three times to thoroughly wash away organic matter such as lipids and waxes from the bamboo strips.

[0012] In step 1, the KOH solution concentration is 0.5 mol / L and the soaking time is 12 h. More preferably, the KOH solution concentration is increased to 1 mol / L and the soaking time is increased to 20 h to fully remove lignin from the bamboo cell walls, making the biological template more porous.

[0013] Furthermore, in step 2, the process of washing the bamboo strips to neutrality involves repeatedly rinsing the bamboo strips in flowing deionized water, then rinsing them once with 0.01 mol / L oxalic acid, and then rinsing them again with deionized water. The final washing endpoint is determined by measuring the pH of the filtrate at 6.0-8.0 using pH test paper.

[0014] Furthermore, in step 3, the concentration of the indium nitrate solution is 0.3 mol / L, the solution volume is 10 ml, and the immersion time is 5 days.

[0015] The preferred concentration of the indium nitrate solution in step 3 is 0.5 mol / L, the preferred solution volume is 15 ml, and the preferred immersion time is 7 days.

[0016] Furthermore, in step 4, the soaked and dried bamboo strips are transferred to a muffle furnace and heated at a rate of 5°C / min, and annealed at 550°C and 600°C for 2 hours.

[0017] In step 4, the soaked and dried bamboo strips are transferred to a muffle furnace and heated at a rate of 5°C / min, preferably annealed at 550°C for 2 hours.

[0018] The product obtained after annealing in step 4 needs to be ground into fine powder. Grinding helps to collect the powder for making sensor sheets.

[0019] Another object of the present invention is to provide a preparation system for indium oxide gas-sensitive materials based on bamboo biotemplates, comprising: The cutting module is used to cut natural bamboo into slices, heat and clean them in a water bath, then ultrasonically clean them in anhydrous ethanol, and finally soak them in KOH solution.

[0020] The washing module is used to wash the bamboo strips, which have been thoroughly soaked in KOH solution, multiple times until they are neutral, and then transfer them to an oven for drying.

[0021] The adsorption module is used to immerse the treated bamboo strips in an indium nitrate solution to allow them to fully adsorb the indium source.

[0022] The annealing module is used to remove the impregnated bamboo strips and place them in an oven to dry. The dried bamboo strips are then placed in a muffle furnace and annealed in an air atmosphere to finally obtain In2O3 powder with a multi-level porous structure of bamboo.

[0023] Another object of the present invention is to provide a computer device comprising a memory and a processor, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the steps of the method for preparing indium oxide gas-sensitive material based on bamboo biotemplate.

[0024] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method for preparing the indium oxide gas-sensitive material based on a bamboo biotemplate.

[0025] Another objective of this invention is to provide an information data processing terminal for implementing the preparation system of indium oxide gas-sensitive material based on bamboo biotemplate.

[0026] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows: This invention provides a gas-sensitive material for detecting nitrogen dioxide gas. The material uses bamboo as a biological structural template. Bamboo strips are impregnated with indium nitrate, allowing indium ions to fully penetrate and adsorb into the porous structure within the bamboo, thus achieving indium loading on the bamboo matrix. After drying, it is calcined at high temperature in air. This high-temperature heat treatment removes the organic components of the bamboo through pyrolysis, while a small amount of its inherent inorganic component, silica, is retained, forming a supporting framework and maintaining the fine structure of the biological template. This significantly increases the specific surface area of ​​the material, thereby improving its gas-sensitive sensing performance.

[0027] The indium oxide gas-sensitive material described in this invention exhibited a high response value (R0) of 3300 in the experiment of dynamic detection of nitrogen dioxide gas. g / R a The material preparation method described in this invention uses natural and renewable bamboo as a template precursor, replacing the complex synthetic templates required in traditional synthesis, thus achieving high-value-added resource utilization of biomass waste. Furthermore, compared to hydrothermal / solvothermal methods that require continuous high temperature and pressure, the main energy consumption of this preparation method is concentrated in the final calcination stage, effectively reducing the energy consumption of the entire material preparation process. Moreover, the preparation process does not require the use of precious metals or toxic and harmful organic solvents, reducing the use and emission of harmful substances from the source, which aligns with the concept of "green chemistry." This lays a solid foundation for the development of novel metal oxide semiconductors and provides new possibilities for the development of high-precision integrated sensors.

[0028] The technical solution of this invention fills a technical gap in the industry at home and abroad: This invention uses bamboo as a biological template to prepare semiconductor gas-sensitive materials. Bamboo has strong adaptability to the growth environment and is inexpensive, which can effectively solve many problems in traditional chemical preparation methods, such as high energy consumption, high price, environmental pollution, and complex preparation methods. The indium oxide gas-sensitive sensing material prepared can efficiently detect nitrogen dioxide gas and has the characteristics of rapid response recovery and good stability. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation method of indium oxide gas-sensitive material based on bamboo biological template provided in the embodiments of the present invention.

[0030] Figure 2 This is a structural block diagram of the preparation system for indium oxide gas-sensitive materials based on bamboo biological templates provided in this embodiment of the invention.

[0031] Figure 3This is a microscopic morphology image (SEM image, SEM is an abbreviation for Scanning Electron Microscope) of the In2O3 gas-sensitive material synthesized in Example 1 of this invention.

[0032] Figure 4 This is the XRD pattern of the In2O3 gas-sensitive material synthesized in Example 1 of this invention (XRD is an abbreviation for X-ray diffraction).

[0033] Figure 5 This is the TG curve of the In2O3 gas-sensitive material synthesized in Example 1 of the present invention (TG is an abbreviation for Thermogravimetric).

[0034] Figure 6 This is a response curve of the In2O3 gas-sensitive material synthesized in Example 1 of the present invention for detecting 50ppm nitrogen dioxide gas at 140℃ for 5 cycles.

[0035] Figure 7 This is a response curve of the In2O3 gas-sensitive material synthesized in Example 1 of the present invention at 140°C to detect the nitrogen dioxide gas concentration gradient from 1ppm to 50ppm.

[0036] Figure 8 This is a long-term stability response curve of the In2O3 gas-sensitive material synthesized in Example 1 of the present invention when detecting 50ppm nitrogen dioxide gas at 140℃ (tested once every three days, for a total of 6 tests). Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] like Figure 1 As shown, the preparation method of an indium oxide gas-sensitive material based on bamboo biological template provided in this embodiment of the invention includes the following steps: S101 involves cutting natural bamboo into slices, heating and cleaning them in a water bath, then ultrasonically cleaning them in anhydrous ethanol, and finally soaking them in KOH solution.

[0039] S102 involves repeatedly washing bamboo strips that have been thoroughly soaked in KOH solution until neutral, and then transferring them to an oven for drying.

[0040] S103, the treated bamboo strips are immersed in an indium nitrate solution to allow them to fully adsorb the indium source.

[0041] S104, the soaked bamboo strips are taken out and placed in an oven to dry. The dried bamboo strips are then placed in a muffle furnace and annealed in an air atmosphere to finally obtain In2O3 powder with a multi-level porous structure of bamboo.

[0042] In the embodiment of the present invention, the bamboo strips in S101 are cut to a size of 10mm × 10mm, the water bath temperature is 80℃, and the water bath time is 30min.

[0043] In the embodiment of the present invention, the ultrasonic time of bamboo strips in anhydrous ethanol in S101 is 1 hour; more preferably, the ultrasonic time for a single ultrasonic session is 0.5 hours, the ethanol solution is replaced and the ultrasonic process is repeated three times to thoroughly wash away organic matter such as lipids and waxes from the bamboo strips.

[0044] The KOH solution concentration in S101 is 0.5 mol / L, and the soaking time is 12 h; more preferably, the KOH solution concentration is increased to 1 mol / L, and the soaking time is increased to 20 h, so as to fully remove the lignin in the bamboo cell wall and make the biological template more loose and porous.

[0045] In the process of washing bamboo strips to neutral in S102 provided in this embodiment of the invention, the bamboo strips are placed in flowing deionized water and rinsed repeatedly, then rinsed once with 0.01mol / L oxalic acid, and then rinsed again with deionized water; the final washing endpoint is determined by pH test paper to be 6.0-8.0 of the filtrate.

[0046] The indium nitrate solution in S103 provided in this embodiment of the invention has a concentration of 0.3 mol / L, a solution volume of 10 ml, and an immersion time of 5 days.

[0047] The preferred concentration of the indium nitrate solution in S103 is 0.5 mol / L, the preferred solution volume is 15 ml, and the preferred immersion time is 7 days.

[0048] In S104 of the present invention, the soaked and dried bamboo strips are transferred to a muffle furnace and heated at a rate of 5°C / min, and annealed at 550°C and 600°C for 2 hours.

[0049] In step S104, the soaked and dried bamboo strips are transferred to a muffle furnace and heated at a rate of 5°C / min, preferably annealed at 550°C for 2 hours.

[0050] The product obtained after annealing in S104 needs to be ground into fine powder. Grinding helps to collect the powder for making sensor sheets.

[0051] like Figure 2 As shown, the preparation system of indium oxide gas-sensitive material based on bamboo biotemplate provided in this embodiment of the invention includes: The cutting module is used to cut natural bamboo into slices, heat and clean them in a water bath, then ultrasonically clean them in anhydrous ethanol, and finally soak them in KOH solution.

[0052] The washing module is used to wash the bamboo strips, which have been thoroughly soaked in KOH solution, multiple times until they are neutral, and then transfer them to an oven for drying.

[0053] The adsorption module is used to immerse the treated bamboo strips in an indium nitrate solution to allow them to fully adsorb the indium source.

[0054] The annealing module is used to remove the impregnated bamboo strips and place them in an oven to dry. The dried bamboo strips are then placed in a muffle furnace and annealed in an air atmosphere to finally obtain In2O3 powder with a multi-level porous structure of bamboo.

[0055] Another object of the present invention is to provide a computer device comprising a memory and a processor, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the steps of the method for preparing indium oxide gas-sensitive material based on bamboo biotemplate.

[0056] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method for preparing the indium oxide gas-sensitive material based on a bamboo biotemplate.

[0057] Another objective of this invention is to provide an information data processing terminal for implementing the preparation system of indium oxide gas-sensitive material based on bamboo biotemplate.

[0058] Specific implementation of the present invention: Example 1 The preparation method of indium oxide gas-sensitive material (BB-In) based on bamboo biological template provided in Example 1 of this invention includes the following steps: Preparation of BB-In precursor: Natural bamboo was cut into 10mm × 10mm strips and placed in a water bath at 80℃ for 30 minutes. Afterward, it was ultrasonically cleaned in anhydrous ethanol for 30 minutes each time, with the ethanol solution changed and the ultrasonic cleaning process repeated three times. Finally, it was soaked in a 1mol / L KOH solution for 20 hours. The bamboo strips, fully soaked in KOH solution, were repeatedly rinsed in running deionized water, then rinsed once with 0.01mol / L oxalic acid, and rinsed again with deionized water. The final washing endpoint was determined by pH paper, with the filtrate pH between 6.0 and 8.0. The washed bamboo strips were then transferred to an oven for drying. The dried bamboo strips were then immersed in 15ml of a 0.5mol / L indium nitrate solution to ensure sufficient adsorption of the indium source. After seven days of immersion, the bamboo strips were removed and dried in an oven.

[0059] Preparation of BB-In: The precursor product was transferred to a muffle furnace and annealed at 550℃ for 2 hours with a continuous heating rate of 5℃ / min. After natural cooling, the product was collected and ground to obtain indium oxide gas-sensitive material. The prepared material was then characterized as follows: Figure 3 , Figure 4 , Figure 5 The images shown are SEM, XRD, and TG plots, respectively.

[0060] Performance testing of the gas-sensitive material: 0.015 g of the synthesized gas-sensitive material was dissolved in 400 μL of deionized water. The sample was ultrasonicated for 2 min to disperse it evenly in the water. Then, 2.5 μL of the dispersed sample solution was uniformly coated onto a resistive sensing sheet (4 mm × 8 mm). The sensing sheet consisted of two intersecting gold (Au) electrodes on a silicon dioxide (SiO2) substrate. The intersecting area was the coating area of ​​the sensing material. After the sensing sheet air-dried, a layer of indium oxide gas-sensitive material was coated onto the surface. The sensing sheet was placed on a programmable temperature-controlled heating stage and heated to 140 °C. A resistance testing machine was then connected, and air, 50 ppm nitrogen dioxide gas, and air were sequentially introduced at a rate of 1 L / min. The response value change curve was obtained. The gas-sensitive performance is as follows: Figure 6 , Figure 7 , Figure 8 As shown, this material exhibits excellent sensing performance for nitrogen dioxide gas, from Figure 6 As can be seen, the response value to 50 ppm nitrogen dioxide reached over 3300, with a response time of 10 seconds and a recovery time of 50 seconds. Furthermore, the response to nitrogen dioxide remained stable during 5 cycles of testing. Figure 7 The paper presents the concentration gradient response curves of indium oxide gas-sensitive material to nitrogen dioxide gas at concentrations of 1, 2, 5, 10, 20, and 50 ppm, showing that the response values ​​within this concentration range exhibit a good linear gradient. Figure 8 The long-term stability also demonstrates that the material has good stability, providing a basis for practical applications.

[0061] Example 2 The preparation method of indium oxide gas-sensitive material (WD-In) based on a dead tree branch biological template provided in Example 1 of this invention includes the following steps: Preparation of WD-In precursor: The deadwood branches were cut into short branches with a diameter of 10 mm and a length of 15 mm. These branches were then placed in a water bath at 80°C for 30 minutes, followed by ultrasonic cleaning in anhydrous ethanol for 30 minutes per session. The ethanol solution was changed, and the ultrasonic cleaning was repeated three times. Finally, the branches were soaked in a 1 mol / L KOH solution for 20 hours. The branches, fully soaked in the KOH solution, were repeatedly rinsed in running deionized water, then rinsed once with 0.01 mol / L oxalic acid, and rinsed again with deionized water. The final washing endpoint was determined by pH paper, with the filtrate pH between 6.0 and 8.0. The washed branches were then transferred to an oven for drying. After drying, the branches were immersed in 15 ml of a 0.5 mol / L indium nitrate solution to ensure sufficient adsorption of the indium source. After seven days of immersion, the branches were removed and dried in an oven.

[0062] Preparation of WD-In: The precursor product was transferred to a muffle furnace and annealed at 600°C for 2 hours with a continuous heating rate of 5°C / min. After natural cooling, the product was collected and ground to obtain indium oxide gas-sensitive material.

[0063] Performance testing of the gas-sensitive material: 0.015 g of the synthesized gas-sensitive material was dissolved in 400 μL of deionized water. The sample was ultrasonicated for 2 min to disperse it evenly in the water. Then, 2.5 μL of the dispersed sample solution was evenly coated onto a resistive sensing sheet (4 mm × 8 mm). The sensing sheet consisted of two intersecting gold (Au) electrodes on a silicon dioxide (SiO2) substrate. The intersecting area was the coating area of ​​the sensing material. After the sensing sheet was allowed to air dry, a layer of indium oxide gas-sensitive material was coated onto the surface of the sensing sheet. The sensing sheet was placed on a programmable temperature-controlled heating stage and heated to 140 °C. A resistance testing machine was then connected, and air, 50 ppm nitrogen dioxide gas, and air were sequentially introduced at a rate of 1 L / min. The response value change curve was obtained. The results showed that the WD-In material synthesized using dead tree branches as a biological template had a response value of only 20 to 50 ppm nitrogen dioxide, and its sensing performance was lower than that of the BB-In material synthesized using bamboo as a biological template.

[0064] The specific application areas or related products of this invention.

[0065] Application Example 1 Dissolve 0.015g of BB-In in 400µL of deionized water. Place the sample in an ultrasonic machine and sonicate for 2 minutes to ensure uniform dispersion in the water. Then, use a pipette to take 2.5µL of the dispersed sample solution and evenly coat it onto a resistive sensor sheet (4mm×8mm). The sensor sheet consists of two intersecting gold (Au) electrodes on a silicon dioxide (SiO2) substrate. The intersecting area is the coating area for the sensing material. After the sensor sheet air-dries naturally, a layer of indium oxide gas-sensitive material is coated onto the surface. Place the sensor sheet on a programmable temperature-controlled heating stage and heat it to 140℃. Connect it to a resistance testing machine and introduce different gases at a rate of 1L / min to obtain the response value change curves.

[0066] Application Example 2 Dissolve 0.015g of WD-In in 400µL of deionized water. Place the sample in an ultrasonic machine and sonicate for 2 minutes to ensure uniform dispersion in the water. Then, use a pipette to take 2.5µL of the dispersed sample solution and evenly coat it onto a resistive sensor sheet (4mm×8mm). The sensor sheet consists of two intersecting gold (Au) electrodes on a silicon dioxide (SiO2) substrate. The intersecting area is the coating area for the sensing material. After the sensor sheet air-dries naturally, a layer of indium oxide gas-sensitive material is coated onto the surface. Place the sensor sheet on a programmable temperature-controlled heating stage and heat it to 140℃. Connect it to a resistance testing machine and introduce different gases at a rate of 1L / min to obtain the response value change curves.

[0067] Evidence related to the technical effects obtained by the embodiments of the present invention.

[0068] The BB-In material synthesized in Example 1 was characterized by XRD, as shown in the following figures. Figure 4 As shown. The results indicate that the characteristic peaks of the indium oxide gas-sensitive material synthesized in Example 1 are consistent with the cubic phase In2O3 standard card, indicating that the obtained indium oxide has high purity. Figure 3 This is a SEM image of the BB-In material synthesized in Example 1. As can be seen from the image, the indium oxide gas-sensitive material is composed of bulk hexahedral stacks. Figure 5 This is the TG curve of the BB-In material synthesized in Example 1. As can be seen from the curve, when the calcination temperature reaches 550℃, the bamboo biomolecular template has been basically removed.

[0069] like Figure 6 As shown, the gas-sensitive material has a response value of 3300 to 50 ppm nitrogen dioxide, with a response time of 10 seconds and a recovery time of 50 seconds. Furthermore, the response to nitrogen dioxide remains stable during 5 cycles of testing. Figure 7The paper presents the concentration gradient response curves of indium oxide gas-sensitive material to nitrogen dioxide gas at concentrations of 1, 2, 5, 10, 20, and 50 ppm, showing that the response values ​​within this concentration range exhibit a good linear gradient. Figure 8 The long-term stability also demonstrates that the material has good stability, providing a basis for practical applications.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing indium oxide gas-sensitive material based on bamboo biotemplate, characterized in that, Includes the following steps: Step 1: After cutting the natural bamboo into slices, wash them in hot water, then ultrasonically clean them in ethanol. Afterward, soak the bamboo slices in potassium hydroxide solution to remove organic matter and break down the cell wall structure. Step 2: Wash the bamboo strips until they are neutral and then dry them; Step 3: Immerse the dried bamboo strips in an indium nitrate solution to allow them to adsorb the indium source; Step four: Dry the impregnated bamboo strips and anneal them in an air atmosphere to obtain indium oxide powder with a hierarchical porous structure of bamboo.

2. The method according to claim 1, characterized in that, In step one, the bamboo strips are 10 mm long and 10 mm wide, the water bath temperature is 80 degrees Celsius, and the water bath time is 30 minutes.

3. The method according to claim 1, characterized in that, In step one, the bamboo strips are sonicated in ethanol for 1 hour, and the ethanol is replaced every 0.5 hours and repeated three times; the concentration of potassium hydroxide solution is 0.5 mol / L to 1 mol / L, and the soaking time is 12 hours to 20 hours.

4. The method according to claim 1, characterized in that, The washing process in step two includes rinsing repeatedly with flowing deionized water, followed by rinsing once with a 0.01 mol / L oxalic acid solution. The washing is considered complete when the pH of the filtrate is between 6 and 8.

5. The method according to claim 1, characterized in that, In step three, the concentration of the indium nitrate solution is 0.3 mol / L to 0.5 mol / L, the solution volume is 10 mL to 15 mL, and the immersion time is 5 to 7 days.

6. The method according to claim 1, characterized in that, In step four, the heating rate is 5 degrees Celsius per minute, the annealing temperature is 550 to 600 degrees Celsius, and the annealing time is 2 hours.

7. The method according to claim 1, characterized in that, The annealed product in step four is then ground to obtain indium oxide powder suitable for preparing gas-sensitive sheets.

8. A system for preparing indium oxide gas-sensitive materials based on bamboo biotemplates for implementing the method according to any one of claims 1 to 7, characterized in that, include: The cutting pretreatment module is used for cutting bamboo, heating and cleaning, ultrasonic cleaning with ethanol, and soaking in potassium hydroxide. The washing and drying module is used to wash and dry the soaked bamboo strips; An adsorption module is used to immerse bamboo strips in an indium-containing solution and allow the bamboo strips to adsorb the indium source. The annealing module is used to anneal dried bamboo strips to form indium oxide powder with a hierarchical porous structure.

9. The preparation system according to claim 8, characterized in that, The cutting and pre-processing module can process bamboo into bamboo strips measuring 10 mm by 10 mm and has an 80-degree Celsius heating and cleaning function as well as an ethanol ultrasonic cleaning function.

10. The preparation system according to claim 8, characterized in that, The annealing module has a temperature control function that allows setting the heating rate to 5 degrees Celsius per minute and setting the annealing temperature to 550 degrees Celsius to 600 degrees Celsius.

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