Reparation Of Novel Tin Oxide-based Humidity-sensitive Composites By Electrospinning And Its Application

Humidity sensors have a wide range of applications in medical and health applications,product performance testing,process control,and biological environment monitoring.With the advancement of technology and the increasing demand for sensors,people are committed to realizing humidity sensors with high sensitivity,rapid response recovery,long-term stability,and simple and easy operation.In this paper,two new nano-humidity materials Li Cl/Sn O₂/Ni O（LSNO）and Sn O₂/Cu O composites were prepared by electrospinning and calcination.The structure and properties of the materials were studied,and the humidity sensing mechanism was explored.The results show that the products all have good humidity-sensitive performance,as follows:1.Preparation of Li Cl/Sn O₂/Ni O（LSNO）humidity sensitive material with hollow porous nanofiber structure:A novel Li Cl/Sn O₂/Ni O（LSNO）hollow nanofiber humidity-sensitive material was prepared by electrospinning followed by in-situ calcination.A series of LSNO complexes（named LSNO-x（x=1,2,3,4,5））were obtained by adjusting the feed ratio of Sn/Ni and the doping amount of Li Cl in the precursor.The structural composition,morphological characteristics and humidity-sensing properties of the samples were characterized and tested.The research shows that the LSNO humidity-sensitive composite material with high sensitivity and fast response recovery is obtained by compounding different metal oxides and doping hydrophilic materials,which solves the problems of slow recovery and baseline drift of a single Sn O₂ material.Among them,the LSNO-3 composite material has high sensitivity（3.4 orders of magnitude change in impedance）,fast response（1 s）and recovery speed（2 s）,reliable repeatability and stability.The reasons for the excellent moisture-sensing properties of LSNO composites are as follows.1.The formation of the Sn O₂/Ni O composite P-N heterojunction promotes the increase of charge carriers and promotes the charge transfer between the sensitive material and water molecules,thereby accelerating the response and recovery of the sensor.2:The doping of Li Cl increases H₂O adsorbed on the material and improves the sensitivity of the sensor;it also provides ionic conductivity and accelerates the adsorption and desorption process of water molecules.3:The product has porous nanofiber structure,which facilitates the diffusion of H₂O,thereby shortening the response recovery time.Therefore,the ternary LSNO composite has practical application significance in the field of humidity sensing.2.Preparation of Sn O₂/Cu O composite humidity sensitive materials rich in oxygen vacancies:The Sn O₂/Cu O composite has the advantage of high sensitivity,but has the problem of long recovery time.We used electrospinning and urea blend calcination,and adjusting the feeding ratio of Sn/Cu salt and the amount of urea added in the spinning solution,to obtain a series of Sn O₂/Cu O rich in oxygen vacancies（O_v-Sn O₂/Cu O）composite moisture sensitive material.Urea produces ammonia gas during calcination to provide a reducing environment,and oxygen vacancies are generated.Oxygen vacancies can promote the capture of water molecules and the conversion of water molecules into conductive ions,which is beneficial to enhance the adsorption and desorption of water molecules,to speed up sensing.The results show that the O_v-Sn O₂/Cu O sensor containing oxygen vacancies has higher sensitivity than the Sn O₂/Cu O humidity sensitive material,and the recovery speed is significantly improved,from tens of seconds to several seconds.Among them,O_v-Sn O₂/Cu O（4:0.5）-2 has the best humidity sensitivity performance:fast response/recovery time（1 s/2 s）,negligible humidity hysteresis（1.85%）,and the resistance varies by 2.74 orders of magnitude over the humidity range.Therefore,it can be shown that oxygen vacancies are of great significance for improving the humidity-sensing properties.