Facile fabrication of PANI/Zn-tpps4 flexible NH3 sensor based on the bridge of Zn-tpps4

Produced in the process of meat spoilage, ammonia (NH3) is believed to be an important gas, as its concentration is a major indicator for evaluating freshness. A flexible NH3 sensor, based on novel polyaniline/Zn-porphyrin (PANI/Zn-tpps(4)) composite, was designed via a one-step electrodeposition method where a strong pi-pi conjugated system formed through the combination of the quinone ring of the PANI molecular chain and sulfate radical of the Zn-tpps(4) molecule. The new sensor PANI/Zn-tpps(4) film possesses outstanding sensing characteristics in terms of response value,enabling it to perform better than pure PANI film. To further explore the performance of PANI/Zn-tpps(4) film, the gas-sensing properties, humidity and endurance tests were fully evaluated at low NH3 concentration. It was concluded that the sensing performance was dramatically improved, because the Zn-tpps(4),acting as a bridge, facilitated the transfer of electrons from NH3 molecules to PANI molecular chains. It is expected that the PANI/Zn-tpps(4) sensor can be attached to deformable packaging membrane to form an ideal device as meat freshness indicator.