Method for preparing high-sensitivity gas sensor based on undaria pinnatifida

Abstract

In recent years, undaria pinnatifida planting rapidly develops in coastal areas, but the discarding problem of expired undaria pinnatifida gradually appears. Traditional treatment methods, such as incineration and composting, have disadvantages. Although residues can be removed through incineration, harmful smoke can be released, and the environment is affected. Although composting is environment-friendly, the problem of pathogenic bacteria can be caused by improper treatment. In order to solve the problem, the invention provides a method for preparing a high-sensitivity gas sensor by using expired undaria pinnatifida, and the method comprises the steps of freeze drying, carbonization and the like. The sensor can detect 500 ppm of hydrazine, formaldehyde, ammonia gas and trimethylamine target gas at room temperature. The innovation not only enriches the field of gas-sensitive materials, but also develops a new possibility for the application of biomass materials. The preparation method is simple and convenient, and provides technical support for the undaria pinnatifida-based gas sensor. The technology is expected to be popularized nationwide, and a new scheme is provided for treatment and reutilization of waste marine plants.

Description

Technical Field

[0001] This invention relates to the fields of biomaterials science and gas sensing, specifically to a method for preparing a high-sensitivity gas sensor based on wakame seaweed. Background Technology

[0002] Hydrazine is an important chemical substance widely used in aerospace, chemical, and pharmaceutical industries. However, hydrazine is extremely toxic and poses a serious threat to human health. Hydrazine has strong acute toxicity; inhalation or skin contact can lead to serious health problems, with symptoms including headache, nausea, vomiting, difficulty breathing, and confusion. It is also irritating to the skin and eyes, causing redness, pain, and chemical burns. Long-term exposure can cause liver and kidney damage, affect nervous system function, and may trigger allergic reactions. Notably, hydrazine is also a flammable liquid and can form explosive mixtures when mixed with air. Therefore, developing efficient hydrazine gas sensors for explosion monitoring and human health protection is particularly important and urgent to ensure timely action in the event of hydrazine leaks or exposure, safeguarding human safety and health.

[0003] Currently, the most common choice in the market is semiconductor gas sensors, which use metal oxides as a substrate. However, these sensors suffer from high power consumption, high cost, and high operating temperatures, limiting their development and application. Especially in environments requiring precise detection, the lower sensitivity and higher operating temperature of metal oxide semiconductor gas sensors become their limitations. They typically need to operate at temperatures ranging from 150 to 400 °C, which not only increases power consumption but also increases the risk of fire or explosion when detecting flammable and explosive gases such as hydrazine.

[0004] In recent years, carbon materials have attracted widespread attention due to their high conductivity, low cost, good stability, and ease of design. However, traditional carbon-based materials, such as carbon nanotubes and graphene, rely on petrochemical products, which present problems such as non-renewability, environmental unfriendliness, and complex preparation processes. Researchers have begun to search for new carbon materials that are more environmentally friendly, low-cost, and renewable.

[0005] Biomass energy, as a renewable energy source, not only possesses excellent biocompatibility, biodegradability, and permeability, but also advantages such as sustainability and low cost. Its degradability and environmental friendliness help overcome the rigidity and non-degradability drawbacks of traditional sensor substrates. Therefore, biomass materials are considered ideal sensor substrate materials.

[0006] Marine biological materials, especially algal biochar, have attracted considerable attention due to their high regeneration rate and low price. They can grow in natural freshwater and seawater without additional land or fertilizer, and have a higher biomass per unit volume than terrestrial plants. Therefore, they are economic resources worthy of development and utilization. The planting area and yield of wakame seaweed in China have been steadily increasing year by year. Taking 2023 as an example, the planting area of ​​wakame seaweed exceeded 550,000 mu (approximately 36,667 hectares), and the yield reached 1.6 million tons. As an important marine plant in China, wakame seaweed is mainly cultivated in coastal areas such as Fujian, Zhejiang, and Shandong. With a large influx of wakame seaweed, the problem of expired wakame seaweed gradually emerges if it cannot be consumed in time. Traditional wakame seaweed disposal methods mainly include incineration and composting. While incineration can quickly remove residues and release some nutrients, it also brings serious environmental problems, such as the emission of carbon dioxide and harmful fumes, which affects air quality and threatens human health. Composting is an environmentally friendly disposal method that helps to recycle nutrients, but if not handled properly, it may lead to odors and the growth of pathogens.

[0007] In view of this, the present invention proposes an innovative solution. We collect waste and expired wakame seaweed, and through low-temperature pre-freezing, freeze-drying, and carbonization, prepare biomass porous carbon materials, and test their gas-sensitive properties. This method not only solves the problem of recycling waste and expired wakame seaweed, but also obtains high-performance gas-sensitive materials. This innovative technology is expected to make a positive contribution to environmental protection and human health. Summary of the Invention

[0008] This invention uses discarded and expired wakame seaweed from Weihai City, Shandong Province as raw material. It is prepared by low-temperature pre-freezing, freeze-drying, and high-temperature carbonization to obtain biomass-derived carbon materials. Gas-sensitive testing results show that freeze-drying followed by carbonization at 500 °C is the optimal preparation method. The sample responds to four gases: hydrazine, formaldehyde, ammonia, and trimethylamine, exhibiting good selectivity for hydrazine with a high response intensity of 14.2 kJ. The response and recovery times are 29.278 s and 0.764 s, respectively.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a. Preparation method of gas-sensitive materials: b. Wash expired wakame seaweed with deionized water; c. Dry expired wakame seaweed at 70℃ to constant weight; d. Soak dried, expired wakame seaweed in deionized water, then pre-freeze it in a -7°C freezer for 10 hours; e. Place the pre-frozen material into a freeze dryer and freeze-dry for 16 hours; f. The freeze-dried expired wakame seaweed was placed in a ceramic boat and then placed in a chemical vapor deposition (CVD) tube furnace. Under a nitrogen atmosphere (nitrogen flow rate of 0.1-0.2 L / min), the material was carbonized at 500 °C. Simultaneously, the heating temperature and holding time were set, and the tube furnace was heated from room temperature to the target temperature at a rate of 5 °C / min. After reaching the target temperature, it was held for 3 hours. g. Allow the temperature to cool naturally to room temperature, and then remove the wakame seaweed from the chemical vapor deposition tube furnace; h. Grind it using an agate mortar and pestle and place it into a centrifuge tube.

[0010] This invention application provides a method for preparing a high-sensitivity gas sensor based on discarded and expired wakame seaweed, which is prepared according to the above method.

[0011] Beneficial Technical Effects of this Invention: This invention selects waste and expired wakame seaweed as a biomass raw material, and prepares biomass-derived carbon material through a carbonization reaction. This carbon material is then detected in a gaseous environment, increasing the added value of marine plant treatment and improving the efficient utilization of waste and expired wakame seaweed resources. The material used in this invention mainly comes from wakame seaweed, a waste marine plant consumed in large quantities in my country. This raw material is abundant and easily accessible. Choosing waste and expired wakame seaweed to prepare biomass carbon not only greatly expands the application range of waste and expired wakame seaweed, but also provides a new approach for the effective treatment of waste and expired wakame seaweed. Traditional wakame seaweed treatment methods mainly include incineration and composting. Although incineration can quickly remove residues and release some nutrients, it also brings serious environmental problems, such as the emission of carbon dioxide and harmful fumes, which affects air quality and threatens human health. Composting is an environmentally friendly treatment method that helps to recycle nutrients, but if not handled properly, it may lead to odors and the growth of pathogens. Therefore, how to effectively utilize waste wakame seaweed to solve the treatment problem and achieve sustainable resource utilization has important research value. This invention uses waste and expired wakame seaweed as a biomass raw material and prepares biomass-derived carbon materials through a carbonization reaction for gas detection. This not only increases the added value of marine plant treatment but also promotes the efficient utilization of waste and expired wakame seaweed resources.

[0012] This invention utilizes expired wakame seaweed, a waste marine plant, to recycle and reuse biomass carbon. The resulting carbon not only possesses the inherent environmentally friendly properties of biomass materials, but also, after freeze-drying, retains the shape of the original material and is even more saturated. Cross-sections show a more porous structure compared to the original material, resulting in a high specific surface area. Furthermore, it exhibits abundant active sites and excellent electrochemical properties. The sample responds to four gases: hydrazine, formaldehyde, ammonia, and trimethylamine. However, it shows better selectivity for hydrazine, with a response intensity 14.2 kJ higher, and response and recovery times of 29.278 s and 0.764 s, respectively. Attached Figure Description

[0013] Figure 1 Scanning electron microscope (SEM) image of the biomass carbon material prepared in this invention. Figure 2 Elemental analysis mapping diagram of the biomass carbon material prepared in this invention. Figure 3 X-ray diffraction (XRD) pattern of biomass carbon material prepared according to the present invention Figure 4 The Fourier transform infrared (FTIR) spectrum of the biomass carbon material prepared in this invention is shown below. Figure 5 Gas-sensitive detection curves of the biomass carbon material prepared in this invention for formaldehyde, ammonia, trimethylamine and hydrazine in three repeated cycles at room temperature (25 °C); Figure 6 The response recovery curve of the biomass carbon material prepared in this invention to hydrazine is shown. Detailed Implementation

[0015] The following is a detailed description of various exemplary embodiments of this invention. This description illustrates alternative embodiments of this invention; however, it is more clearly stated that this invention can be implemented in various forms and is not intended to limit the invention. Rather, these specific embodiments are provided to increase the completeness and thoroughness of the invention and to clearly and fully convey the scope of this invention to those skilled in the art.

[0016] The terminology used in this application is not intended to limit the scope of the application, but is merely for describing the embodiments. The singular forms “a,” “the,” etc., used in this application and the claims are intended to represent more than one form, but to encompass multiple forms. Open-ended terms such as “having,” “comprising,” etc., used herein mean including but not limited to, unless specifically stated otherwise.

[0017] The numerical ranges used herein do not specifically refer to or represent any particular intermediate value, but rather encompass every intermediate value within that specific range. Any stated value or every smaller range within a stated range is also included in this application.

[0018] Unless otherwise specified herein, all technical and scientific terms used herein have the same meaning as understood by one of ordinary skill in the art. While only preferred materials and embodiments have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0019] The following is a detailed description of a method for preparing a high-sensitivity gas sensor based on wakame seaweed, in conjunction with the accompanying drawings:

[0020] Example 1 The method for preparing a high-sensitivity gas sensor from wakame seaweed according to this invention application includes: a. Wash expired wakame seaweed with deionized water; b. Dry the wakame seaweed from step a at 70°C until constant weight; c. Soak dried wakame seaweed in deionized water, then pre-freeze it in a -7°C freezer for 10 hours; d. Place the pre-frozen wakame seaweed into a freeze dryer and freeze-dry for 16 hours; e. The freeze-dried wakame seaweed was placed in a ceramic boat and then placed in a chemical vapor deposition (CVD) tube furnace. Under a nitrogen atmosphere (nitrogen flow rate of 0.1-0.2 L / min), the sample was carbonized at 500 °C. Simultaneously, the heating temperature and holding time were set, and the tube furnace was heated from room temperature to the target temperature at a rate of 5 °C / min. After reaching the target temperature, it was held for 3 hours. f. Allow the temperature to cool naturally to room temperature, then remove the cooled wakame seaweed from the chemical vapor deposition tube furnace; g. Grind using an agate mortar and pestle, then place the mixture into centrifuge tubes.

[0021] Example 2 like Figure 1 The SEM images shown reveal the morphology of the material. The surface of the sample shown in Figure a exhibits a structure similar to a dog's nose mirror, filled with wrinkles and grooves. Simultaneously, numerous dot-like structures are present on the wrinkles, increasing the specific surface area and providing more active sites. The cross-section of the sample shown in Figure b reveals a layered, porous structure, thus giving the sample a high specific surface area.

[0022] Example 3 Figure 2The mapping diagram shows that the sample is rich in C and O elements, as well as trace elements such as Na and K. When a given voltage is applied, the presence of these trace elements enables current conduction, further improving the gas sensing performance of the gas sensor.

[0023] Example 4 Figure 3 The following are XRD patterns of QD500 at different temperatures. According to the figure below, we can see that the material has diffraction peaks at 22° and 43.3°, which correspond to the (002) and (100) crystal planes of graphite carbon, respectively.

[0024] Example 5 Figure 4 The Fourier transform infrared spectrum was used to study the functional groups of the sample. The sample has abundant functional groups, which provide active sites for gas adsorption, thus exhibiting high sensitivity.

[0025] Example 6 Figure 5 To connect the power supply of the optoelectronic integrated test platform CGS-MT, the sensor's response to 500 ppm of target gases hydrazine, formaldehyde, ammonia, and trimethylamine was tested at room temperature (temperature 25 ℃, relative humidity 25%) under a bias voltage of 4 V. It was found that the gas sensor prepared in this invention exhibits high sensitivity and selectivity to hydrazine.

[0026] Example 7 pass Figure 6 It can be seen that the sample's response intensity to hydrazine is 14.2k, and the response and recovery times are 29.278s and 0.764s, respectively.

Claims

1. Preparation method of gas-sensitive materials: a. After thoroughly washing the expired wakame seaweed provided by volunteers from Weihai City, Shandong Province with deionized water, dry it at 70℃ to constant weight, close the drying oven, and let it cool naturally to room temperature; b. After removing the wakame seaweed obtained in step a, soak it in a beaker containing deionized water; c. Place the wakame seaweed obtained in step b in the refrigerator at -7℃; d. Place the pre-frozen wakame seaweed from step c into a freeze dryer for 16 hours of freeze-drying; e. Take out the wakame seaweed obtained in step d, put it into a ceramic boat and place it in a chemical vapor deposition furnace. After introducing N2, carbonize it at 500 °C for 3 h, and let it cool naturally to room temperature in the tube furnace to obtain biomass carbon gas-sensitive material. f. Take out the sample obtained after carbonization in step e, grind it thoroughly in an agate mortar for 5 minutes to obtain a fine powder, then mix it with a certain proportion of deionized water and continue grinding to obtain a uniformly dispersed solution. Use a dropper to evenly drop the solution onto interdigitated electrode plates, and let it stand at room temperature for 24-48 hours to dry, thus preparing a gas sensor based on wakame seaweed. According to claim 1, a method for preparing a high-sensitivity gas sensor based on wakame seaweed is characterized in that... In step e, during the carbonization process, the heating rate of the tubular furnace is 5 °C / min, and the nitrogen flow rate is 0.1-0.2 L / min.

2. A high-sensitivity gas sensor based on wakame seaweed, characterized in that, Prepared according to the preparation method according to any one of claims 1 to 2.

3. The high-sensitivity gas sensor prepared based on wakame seaweed according to claim 3 has the application of efficient and rapid detection of hydrazine gas.

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