Humidity sensing properties of poly-vanadium-titanium acid combined with polyaniline grown in situ by electrochemical polymerization

Abstract

A high-performance humidity sensor based on multilayer-structured poly-vanadium-titanium acid/polyaniline (V-Ti/PANI) composite was reported in this paper. A two-layer-structured V-Ti/PANI composite was fabricated by dip-coating poly-vanadium-titanium acid first on the surface of the interdigitated gold electrode (IDE) and electrochemically polymerizing polyaniline afterward onto the surface of the sensor covered with poly-vanadium-titanium acid, then the process could be repeated to prepare the multilayer-structured V-Ti/PANI composite. Morphological and structural characteristics of the composite were characterized using various techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy (UV–vis). It can be confirmed that PANI and poly-vanadium-titanium acid are considered to be combined through electrostatic interactions and hydrogen bonding in the composite. The humidity sensing performances of the composite exhibited not only small hysteresis (∼5% RH), fast response (8 s) and recovery (11 s) time but also high stability within the relative humidity (RH) range of 11%–97%. In order to explore the humidity sensing mechanism of the composite, the complex impedance spectra, the fitting data and the equivalent circuit at different RHs were analyzed. All the results demonstrate the multilayer-structured V-Ti/PANI composite can be used as a promising material for the fabrication of humidity sensors.