Dopamine Interface Coupled Enhanced Self-Powered Ammonia Sensor

With the rise of the Internet of Things（IOT）in the high-speed information era,various emerging technologies have been driven to flourish.Sensor technology as one of the most crucial component in the IOT system,domestic and foreign sensor researches focus on the power supply and regular maintenance of sensing nodes in IOT,which turns out to be an ideal solution to solve the current energy consumption problem for sensor network and wearable electronics.Harvesting mechanical energy from nature to sustain the operation of sensors can greatly reduce the energy crisis on sensor networks.Piezoelectric composite fibers based on the piezoelectric effect can effectively convert mechanical energy from the surrounding environment into electrical energy,becoming new direction for the preparation of self-powered sensors.Ammonia（NH₃）is one of the most common harmful gases in the atmosphere,which considerably jeopardizes the human and animals.Therefore,the combination of NH₃ sensing technology and self-driving technology to prepare self-powered NH₃ sensors on the basis of three-dimensional skeleton has become a hot topic in the field of electronic devices for environmental monitoring and health management.In this paper,polyvinylidene fluoride（PVDF）is used to construct the three-dimensional skeleton structure of the self-powered sensor by electrospinning process.During the preparation process,dopamine（PDA）is attached to PVDF fibrous scaffold throughπ-πstacking or covalent bonding with surface carboxyl groups.The loading of hydrophilic PDA not only enhances the dispersion of PVDF in water,but also provides enough active sites for the subsequent in-situ polymerization of PANI.Due toπ-πstacking,the PANI layer is further bonded to PDA/PVDF,which plays a key role in the sensing process.The study of the self-powered ammonia sensor and its performance are carried out through three directions,including optimization of composite sensitive film,sensor structure design,and gas sensing mechanism,which are mainly investigated as follows.1.The nanofibers prepared by electrospinning process of PDA and PVDF form a three-dimensional skeleton on the interdigital electrode.Due toπ-πstacking,PANI can grow uniformly and densely on the three-dimensional skeleton as a gas-sensing layer.The effect of PDA doping amount and PANI polymerization time on the device performance is investigated.Experiments show that the introduction of PDA can improve the ammonia-sensitive performance of the device,and the gas-sensitive response can reach320.5%at 200 ppm NH₃,with a sensitivity of 1.76%ppm^-1.2.The introduction of PDA can simultaneously increase the ratio of PVDF polarβ-phase and provide more sites for in situ polymerization of PANI.PANI and PDA/PVDF form a core-shell nanofiber configuration,where PDA/PVDF acts as a pressure-sensitive region as well as the power source in the core part to convert external pressure into piezoelectric signals,and PANI acts as a gas-sensing layer.The sensing mechanism is based on the interfacial electrostatic shielding of the core piezoelectric part as a consequence of NH₃ chemisorption on the shell layer of PANI.As the surface PANI as a gas-sensing layer changes its resistance by detecting NH₃ signal and thus reduces the interfacial electrostatic shielding effect on the core part,the piezoelectric output will be further improved.According to the testing results,the sensitivity can reach 0.316 V/N for pressure detection,and achieve high response（133.45%under 200 ppm）,great selectivity(0.69%ppm^-1)and good stability in the self-powered gas sensing measurement.