Electrosynthesized fluorinated polybithiophenes for ammonia sensing

Abstract

Tuning the frontier orbital energies is the way to control the nature of majority charge carriers. Therefore, among sensing materials operating under a real atmosphere, fluorinated compounds are under the spotlight. Herein, 5-(pentafluorophenyl)-2,2′-bithiophene was synthesized and polymerized or copolymerised with thiophene. The poly(pentafluorophenylbithiophene) derivatives were deposited as a sublayer for double lateral heterojunction gas sensors, by electrochemical processing, opening the possibility of building asymmetrical devices. The sensor behaviour, including sensitivity and reversibility towards various ammonia gas concentrations ranging from 1 ppm to 90 ppm, was investigated, with a limit of detection from 59 to 0.3 ppm, depending on the composition of the copolymers. The effect of UV light was studied to investigate its impact on the material stability and sensing properties.