Ultrasensitive NH3 Gas Sensor From Nanostructured TiO2 -Polyaniline PN Heterojunctions

Increasing demands for ever more sensitive chemical sensors have led to an upsurge of interest in combining nanostructured metal oxides with polymers. The PN junction materials consisting of semiconductive inorganic oxides and conductive polymers have been widely used to enhance the sensitivity of nanostructured sensors. Most of the enhancements on the sensing sensitivity are due to a synergy of organic and inorganic parts. Although sensors based on nanostructured PN junction have been reported, there are still many challenges in making a ultrasensitive sensor. Field-effect transistor is the most common technique that uses PN junctions to enhance nanosensor sensitivity and selectivity. In this communication, we present an alternative way to take the advantages of PN junctions for fabricating ultrasensitive nanostructrued gas sensors. Specifically, nanoparticles of a P-type conductive polymer, polyaniline (PANI), are enchased on electrospun semiconductive TiO2 nanofiber surface. The PN heterojunctions formed between TiO2 nanofibers and PANI nanoparticles function as electric current switches when NH3 gas is absorbed by PANI nanoparticles. The PN heterojunctions formed between TiO2 nanofibers and PANI nanoparticles function as electric current switches when NH3 gas is absorbed by PANI nanoparticles. The sensor constructed with these unique PN heterojuctions can detect as low as 50 ppb of NH3.