Versatile sensing capabilities of layer-by-layer deposited polyaniline-reduced graphene oxide composite-based sensors

Precise temperature, humidity, and organic pollutants monitoring are required for industrial, environmental and medical applications. The interesting properties of polyaniline for sensors, such as environmental responsiveness and stability, combined with the large surface area and tunable properties of graphene oxide, offer excellent prospects for the development of sensor materials. In this paper, we show that HCl-doped polyaniline/reduced graphene oxide (PANI/rGO) layer-by-layer deposition and subsequent reduction can be used as resistive sensors for temperature, humidity, acetone, and electrochemical sensors for organophosphate detection in aqueous so-lutions. Sensors were characterized using atomic force and scanning electron microscopies and energy-dispersive x-ray and Raman spectroscopies, and impedance spectroscopy complemented by semi-empirical quantum chemical calculations. Reduction temperature and bilayer numbers influence PANI/rGO sensor characteristics significantly. The results show that only one PANI/rGO bilayer is needed to provide a temperature coefficient of resistance of -0.758 degrees C- 1 and 37% sensitivity at 95% relative humidity. PANI/rGO shows potential for elec-trochemical detection of dimethoate affected by the number of bilayers and reduction temperature. The response to acetone vapor is linear from 1 to 60 ppm and detectable at 1 ppm. The sensors do not respond to methanol and some other volatile organic compounds (VOCs) at the same concentration. Food monitoring with total VOCs detection was successfully demonstrated. PANI/rGO sensors feature versatile sensing capabilities, making them feasible due to their rapid production and low cost.