Study On The Preparation And Gas Sensitive Property Of Cotton Fiber Matrix Composites

Gas-sensitive sensing devices include sensing materials and sensing substrates.Traditional sensing devices mostly use metal oxide semiconductor materials and rigid substrates,which not only have high power consumption and have a limited application range,but also produce some solid wastes that are difficult to degrade,causing environmental Pollution.Biomass materials have attracted wide attention because of their advantages of being green,environmentally friendly,renewable,low in price,and easy to control and adjustable in performance.In this paper,high-temperature carbonization and hydrothermal methods were used to prepare biomass cotton-based CFs and ZnO/CFs and carbon quantum dots CQDs,respectively.The cotton fibers prepared by carbonization produced a hollow structure,increased the specific surface area of CFs and ZnO/CFs,and formed the heterojunction of ZnO and CFs improves the performance of sensing materials.Using expired milk as the precursor,carbon quantum dots CQDs were prepared by hydrothermal method.CQDs have the characteristics of N and S co-doping,nano-particle size,ultra-high specific surface area,etc.,flexible CQDs/PCFT sensors prepared by compounding with cotton fiber Shows high sensitivity and bending stability.In this paper,biomass materials are mainly used to study gas-sensing performance from two aspects:sensing materials and sensing substrates.The specific work is as follows:(1)Renewable waste cotton was carbonized into hollow carbon fibers(CFs)and ZnO/CFs composite by a simple carbonization method,which was studied as gas sensing materials for the first time.It was found that the carbonization destroyed the hydrogen bonds within the cotton fiber and changed their microstructure.Meanwhile,high temperature promoted the decomposition of zinc acetate adsorbed to cotton fibers into ZnO,forming lots of heterojunctions between ZnO and CFs,which further improved the gas sensitive properties.Accordingly,the gas sensing properties of CFs and ZnO/CFs were effectively tailored by controlling the carbonization temperatures,achieving the differential response to the target gases.The sensor array based on CFs and ZnO/CFs displayed the rapid,discriminative detection to target gases at room temperature.The response time and recovery time of sensor array are no more than 15s and 4 s,respectively.The theoretical limit of detection of controlled CFs and ZnO/CFs to CH₂O vapor was determined to be 0.45 ppb and 0.17 ppb,respectively.This work extended the application of cotton to the field of gas sensors and enriched the family of gas sensing materials.(2)Carbon quantum dots(CQDs)co-doped with P?N and S derived from expired milk was prepared by a simple hydrothermal method.Pure cotton face towel(PCFT)was soaked in the CQDs ink and dried to make a flexible all-biomass CQD/PCFT sensor for the first time.Due to the doping of P?N and S,extremely small particle size,uniform dispersion of CQDs and excellent permeability of CQD/PCFT film,the flexible CQD/PCFT sensor showed the high sensitivity and bending stability in the range of 0-60^o.The detection limits of the flexible CQDs/PCFT sensor for CH₂O and H₂O₂are calculated to be 22.1 and 5.3 ppb,respectively.Importantly,because of the rich functional groups and defects of CQDs,the flexible sensor has displayed sensing curves of different shapes for different target analytes,laying a foundation for the discriminative detection of multiple analytes by relying only on single sensor and image recognition.In addition,the binary parameter method of response and response was created,which also showed that a single sensor could show discriminative detection.Biomass CQDs ink is not only convenient,economical and environmentally friendly,but also has rich functional groups and defects,and the synergistic effect of effective combination with cotton fiber improves the gas sensitivity.This work expands the application of biomass CQDs and makes a useful exploration for the development of flexible gas sensors.