A method for preparing cotton straw-based gas-sensitive sensing material

Abstract

The present invention relates to a method for preparing a gas-sensitive sensor material based on cotton stalks. The method involves simple carbonization, hydrothermal and coating processes. At room temperature (25°C), the detection of 1000 ppm of ammonia, hydrogen peroxide, formaldehyde, ethanol and acetone and 85% and 100% relative humidity can be achieved. The discovery of this material has explored a new member for gas-sensitive materials and also provided a possibility for the research of biomass materials in gas-sensitive materials. We apply cotton stalks to the preparation of gas-sensitive sensor materials. The use of cotton stalks to prepare gas-sensitive sensor materials has low cost and is easy to process and manufacture. It has a good application prospect and should be paid attention to and developed.

Description

Technical Field

[0001] The invention relates to the fields of biomaterial science and gas-sensitive sensing materials, and in particular to a method for preparing a gas-sensitive sensor based on cotton stalks, which can realize high-sensitivity detection of toxic and harmful gases. Background Art

[0002] At present, environmental protection issues are becoming more and more important in international affairs and are increasingly valued by people. my country has also proposed two major environmental protection goals: carbon peak and carbon neutrality. In the field of agricultural production, on the one hand, there are problems that crop straw is difficult to handle and the treatment method is single. On the other hand, there is a problem that the existing methods of handling crop straw have low added value and are difficult to generate sufficient benefits. Using straw as raw material to prepare biomass carbon materials and then prepare high-performance sensor devices is of great significance to solving these two problems.

[0003] Biomass carbon materials have the advantages of low cost and easy availability of raw materials. As an economic crop planted on a large scale, cotton produces a huge amount of straw every year. The biomass carbon material prepared from cotton straw has a fine microporous structure, which is conducive to the growth of loaded metal oxides or sulfides on it to form a semiconductor heterojunction, thereby achieving excellent sensor performance. At the same time, biomass carbon materials also have the characteristics of high conductivity and light weight. Traditional semiconductor materials are mainly based on silicon-based materials, but the preparation process of silicon-based materials is very complicated and requires a lot of high-precision technology as support. It also consumes a lot of energy and is not economically cost-effective. Biomass carbon materials have huge advantages in this regard.

[0004] At the same time, the use of cotton straw to prepare carbon material sensors can also effectively solve the problem of crop straw disposal. The traditional way of dealing with straw is generally to burn it or use it as a structural material. But the air pollution problem caused by burning straw has long been obvious to all. A large number of PM10 and PM2.5 air pollution particles are caused by burning straw. For example, the large-scale air pollution in the Beijing-Tianjin-Hebei region in the past few years has had very serious consequences. It was not until the local government strictly controlled the burning of straw that it was significantly improved. Under the urgent requirements of my country's two major goals of carbon peak and carbon neutrality, the environmental protection treatment of straw has of course put forward higher requirements. Therefore, the prospect of using cotton straw as a biomass carbon-based sensor device is very broad.

[0005] We use cotton stalks to prepare gas sensor materials. The use of cotton stalks to prepare gas sensor materials is low-cost and easy to process and manufacture, and has a good application prospect, which should be paid attention to and developed. This invention has great potential for the preparation of high-performance gas sensor devices and the treatment of crop straw waste. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a cotton stalk-based gas-sensitive sensing material, which utilizes high-temperature carbonization under the protection of a nitrogen atmosphere and loads molybdenum sulfide to form a cotton stalk-based gas-sensitive sensing material. The preparation method is simple and flexible, and the production cost is low. It can achieve high-sensitivity detection of formaldehyde, ethanol, ammonia, hydrogen peroxide vapor and different humidity at room temperature (25°C).

[0007] Preparation of gas-sensitive materials:

[0008] a. First, weigh 10 g of thin cotton stalks, remove the outer bast part, so that the cotton stalks are completely exposed, and cut the peeled cotton stalks into pieces;

[0009] b. Grind the chopped cotton stalks in an agate mortar until they are completely crushed into powder and placed in a beaker;

[0010] c. Place the cotton stalks in a tubular furnace, introduce nitrogen as a protective gas, and carbonize at 500°C for 3 hours;

[0011] d. Place the carbonized cotton stalks into a polytetrafluoroethylene reactor, add 1 mmol of ammonium molybdate, 20 mmol of thiourea and 35 ml of deionized water, and perform hydrothermal reaction at 160°C for 4 hours;

[0012] e. Place the filtered and washed samples into a reagent tube;

[0013] f. Place the reagent tube containing the sample into a vacuum drying oven and dry it at a constant temperature of 60°C for 10 h to obtain the cotton stalk-based gas-sensitive sensing material.

[0014] The advantages of the present invention are that a method for preparing a cotton stalk-based gas-sensitive sensor material is provided. The cotton stalk-based gas-sensitive sensor material prepared by the method has good gas-sensitive sensing performance. Biomass is applied to the preparation of gas-sensitive sensor materials. The gas-sensitive sensor material is prepared using cotton stalks, which has low cost and is easy to process and manufacture, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a scanning electron microscope image of the pure cotton stem-based gas-sensitive sensor material in Example 1 of the present invention;

[0016] Figure 2 This is a scanning electron microscope image of the cotton stalk-based gas-sensitive sensor material loaded with molybdenum sulfide in Example 2 of the present invention;

[0017] Figure 3(a) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 1 of the present invention to ammonia water; (b) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 1 of the present invention to water vapor; (c) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 1 of the present invention to hydrogen peroxide; (d) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 1 of the present invention to ethanol.

[0018] Figure 4 (a) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 2 of the present invention to ammonia water; (b) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 2 of the present invention to water vapor; (c) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 2 of the present invention to hydrogen peroxide; (d) is the gas-sensitive response curve of the cotton stalk-based gas-sensitive sensor material in Example 2 of the present invention to ethanol.

[0019] Figure 5 This is the mapping element analysis of the pure cotton stem-based gas-sensitive sensor material in Example 1 of the present invention. From this data, it can be seen that the biomass carbon material obtained after carbonization of the pure cotton stem is mainly composed of carbon, a small amount of nitrogen and oxygen, and almost no sulfur and molybdenum.

[0020] Figure 6 This is the mapping element analysis of the cotton stalk carbon material after molybdenum sulfide loading in Example 2 of the present invention. From this data, it can be seen that in addition to the original carbon, nitrogen and oxygen elements, the surface of the loaded carbon material also carries sulfur and molybdenum elements. Therefore, it can be shown that molybdenum sulfide has been successfully grown on the surface of the carbon material.

[0021] Figure 7 The XRD characterization of the cotton stalk-based gas-sensitive materials in Examples 1 and 2 of the present invention, (a) is the XRD pattern of pure cotton stalk, and (b) is the XRD pattern of cotton stalk loaded with molybdenum sulfide. By comparing the card library data, it is known that the XRD characteristic peaks of cotton stalk loaded with molybdenum sulfide are consistent with the characteristic peaks of molybdenum disulfide.

[0022] Figure 8 This is the Raman characterization of the cotton stem-based gas-sensitive materials in Examples 1 and 2 of the present invention.

[0023] Fig. 9 This is the infrared spectrum characterization of the cotton stem-based gas-sensitive materials in Examples 1 and 2 of the present invention. DETAILED DESCRIPTION

[0024] The essential contents of the present invention are further explained below in conjunction with the accompanying drawings.

[0025] Example 1

[0026] a. First, weigh 10 g of thin cotton stalks and remove the outer bast part to expose the stalks completely;

[0027] b. Wash the surface with deionized water to remove impurities;

[0028] c. Place the cotton stalks in a tubular furnace and introduce nitrogen as a protective gas;

[0029] d. Carbonization at 500℃ for 4h;

[0030] e. Put the carbonized cotton stalk into the reagent tube;

[0031] Preparation of gas sensing materials:

[0032] Example 2

[0033] a. First, weigh 10 g of thin cotton stalks, remove the outer bast part, and expose the cotton stalks. Cut the peeled cotton stalks into small pieces about 2-3 cm long. Then, clean the peeled cotton stalks and place them in a beaker.

[0034] b. Place the cotton stalks in a tubular furnace and introduce nitrogen as a protective gas;

[0035] c. Carbonize the cotton stalks at 500℃ for 4 hours and then take them out.

[0036] d. Place the carbonized cotton stalks in a reactor, add 1 mmol of ammonium molybdate, 20 mmol of thiourea and 35 ml of deionized water, and perform hydrothermal reaction at 160°C for 4 hours;

[0037] e. Then, the carbonized cotton stalks are taken out and collected into a reagent tube, and finally the cotton stalk-based gas-sensitive sensing material is obtained.

[0038] Preparation of gas sensor chip:

[0039] Example 3

[0040] Take a small amount of cotton stalk-based gas-sensitive sensing material and place it in an agate mortar. Use a rubber-tipped dropper to absorb a small amount of deionized water and add it to the agate mortar. Grind it slightly to mix the cotton stalk-based gas-sensitive sensing material and deionized water evenly to form a uniform colloid. Then use a thin brush to dip the mixed colloid and carefully apply it to the electrode sheet of the ceramic substrate with silver interdigital electrodes pre-printed with a finger spacing of about 200 μm, and apply it evenly to form a sensing film. The prepared gas sensor was placed at room temperature to dry naturally for 24 h to obtain a gas-sensitive sensor chip of cotton stalk-based gas-sensitive sensing material.

[0041] Embodiment 1 Detection of target atmosphere by gas-sensitive sensor chip:

[0042] The power of the electrochemical workstation was turned on, and the response curves of the gas sensor chip to ammonia vapor, water vapor, hydrogen peroxide and ethanol gas at room temperature were tested under a bias voltage of 4 V. The average response sizes were 12200%, 4410%, 14200% and 0%, respectively; (e.g. Figure 3 ).

[0043] Embodiment 2 Detection of target atmosphere by gas-sensitive sensor chip:

[0044] The power of the electrochemical workstation was turned on, and the response curves of the gas sensor chip to ammonia vapor, water vapor, hydrogen peroxide and ethanol at room temperature were tested under a bias voltage of 4 V. The average response sizes were 38100%, 3700%, 892% and 1110% respectively; (e.g. Figure 4 ).

[0045] The gas-sensitive sensor chip of the cotton stalk-based gas-sensitive sensor material prepared by this method has a good response to ammonia. As the sensor is immersed in ammonia, the response continues to increase. When the sensor is taken out of the ammonia, the response immediately drops to near the baseline. After three cycles, there are similar responses, indicating that the sensor has high sensitivity and good repeatability.

[0046] The present invention can be more easily understood through the above specific embodiments. The above embodiments are merely exemplary descriptions and should not be construed as examples for limiting the present invention.

Claims

1. A method for preparing a cotton straw-based gas-sensitive sensor material, the specific preparation method is carried out according to the following steps: a. First, weigh 10g of thin cotton stalks, remove the outer bast part, make the cotton stalks completely exposed, and peel off the outer skin of the cotton stalks; b. Place the peeled cotton stalks in a tubular furnace, introduce nitrogen as a protective gas, and carbonize at 500 degrees Celsius for 3 hours; c. Place the carbonized cotton stalks into a polytetrafluoroethylene reactor, weigh 1 mmol of ammonium molybdate, 20 mmol of thiourea, and 35 ml of deionized water into the cleaned polytetrafluoroethylene reactor; d. Place the reactor in a dry heating box, perform hydrothermal reaction at 160°C for 4 hours, then take out the cotton stalks and clean the surface with deionized water; e. Place the washed sample into a reagent tube; f. Place the reagent tube containing the sample into a vacuum drying oven and dry it at a constant temperature of 60°C for 10 hours to obtain the cotton stalk-based gas-sensitive sensing material.

2. The method for preparing a cotton straw-based gas-sensitive sensor material according to claim 1, characterized in that: Step b is a high-temperature carbonization reaction of the cotton stalk under nitrogen protection.

3. The method for preparing a cotton straw-based gas-sensitive sensor material according to claim 1, characterized in that: In step d, molybdenum disulfide is loaded on the cotton stem.

4. The method for preparing a cotton straw-based gas-sensitive sensor material according to claim 1, characterized in that During the cleaning process of step d, the sample is washed until the surface solution is neutral.

5. Use of a cotton stalk-based gas-sensitive sensor material obtained by the method according to claim 1 in preparing a gas-sensitive sensor chip for detecting gases containing ammonia vapor, water vapor, hydrogen peroxide or ethanol.

Images