Surface functionalization of ion-in-conjugation polymer sensors for humidity-independent gas detection at room temperature

Abstract

Organic semiconductors rising as promising chemiresistive materials due to their high sensitivity and high selectivity towards target gas molecules. However, severe interference from moisture remains unsolved despite years of materials innovation. Herein, we realized humidity-independent detection of NO2 as low as 40 parts-per-billion (ppb) at varied humidity up to 80 % RH and room temperature (RT) through functionalization of the organic semiconductor film by polyvinylidene fluoride (PVDF) fibers. This strategy of PVDF surface functionalization is not only universally applicable to different gas sensing materials. The hydrophobic PVDF fibers repel water vapor but allow NO2 diffusing onto the beneath sensing layer, achieving a time stability up to five months at 80 % RH. The sensor devices are endowed with good flexibility (bended to 90° for 5000 times) by sticking the rigid organic semiconductor particles from cracking by the fibers during device bending. Our method is hopefully applicable to a wider range of organic semiconductors, prompting more organic gas sensors with excellent humidity-resistant performance.