Multilevel Micro-nano Controllable Integrated Self-Powered Ammonia Sensor

The total amount of ammonia（NH₃）emission in the world reaches up to 22-83 Tg every year,and a large amount of NH₃ emission poses a serious threat to the global economy and life safety.NH₃ jeopardizes human health.When exposed to a large amount of NH₃,it will affect the human immune system and harm people’s eyes,skin,respiratory tract,liver and kidney,etc.Direct contact with NH₃ will also cause nose,throat irritation,cough and respiratory tract irritation.Existing gas sensors,most of which requiring external power,suffer from low battery power density,short service life,toxic leakage and other problems,in which bulky batteries hinder their potential for versatile scenarios.Self-powered gas sensor is an ideal solution to address these issues.This thesis develops a multilevel micro-nano controllable self-assembly gas-sensitive material and piezoelectric-integrated ammonia sensor based on PPY composites.The specific work is as follows:1.Multilevel micro-nano controllable self-assembly gas-sensitive material was prepared to achieve a good detection ability at the ammonia concentration from 20 ppm-100 ppm.The active sponge layer of the sensor device is synthesized by the original polymerization method,where the gas sensitive material PPY was polymerized on the sponge.The influence of different pore size（15 ppi,20 ppi,25 ppi）and polymerization time（10min,30min,60min and 90min）on the gas sensing performance of gas-sensitive material was systematically studied.The pore size and polymerization time will affect the polymerization morphology of PPY nanoparticles,and thus affect the gas sensing performance.The composite is employed as the active layer of the capacitive ammonia sensor.The repeatability,selectivity and long-term stability of the ammonia sensor were also investigated,revealing the gas-sensing mechanism of the prepared sensor.It is found that the capacitive ammonia sensor fabricated with a pore size of 20 ppi and polymerization time of 90 min features the optimal gas-sensitive response and selectivity for ammonia and long-term stable working ability.The excellent sensing behaviors were attained including 75%responsitivity toward 100 ppm NH3,the sensitivity of 0.42%ppm^-1,the response time/recovery time of 214/324 s.2.An integrated piezo-gas-sensitive ammonia sensor is prepared by adopting the Polypyrrole/PZT-PDMS composite as both piezoelectric layer and gas-sensitive layer.Porous piezoelectric membranes（PZT-PDMS）were fabricated using sacrificed-template method.The effects of polarization time,sequence between polarization and-polymerization of gas-sensitive materials and pressure on the output voltage amplitude of PZT-PDMS nanogenerators were investigated.The gas-sensitive polypyrrole was polymerized on porous piezoelectric PZT-PDMS membrane by in-situ polymerization method.The dependence of gas-sensing responsivity,repeatability,selectivity and long-term stability of ammonia sensor on the loading amounts of pyrrole were studied.Furthermore,a theoretical modeling for the gas-sensitive mechanism was established.Different amounts of pyrrole affect the polymerization of PPY.The ammonia sensor prepared with the amount of 80μl pyrrole achieves the superior gas sensitive response and selectivity for ammonia as well as long-term stability in comparison with other versions.The response value to NH₃ at 100 ppm concentration is 387%,and the sensitivity is 4.29%ppm^-1,with response/recovery time of 764s/772s.