Polyaniline nanofiber reinforced nanocomposite based highly sensitive piezoelectric sensors for selective detection of hydrochloric acid: Analysis of response mechanism

The present study reports the fabrication of a polyaniline (PAni) nanofiber reinforced nanocomposite coated quartz crystal microbalance sensor for the selective detection of hydrochloric acid (HCl) in aqueous environment with equal applicability in laboratory conditions and natural marine ecosystems. This detection system based on the measurement of mass change corresponding to a frequency shift of the modified quartz crystal relies on the high dissociating capability of HCl in aqueous medium resulting in fast and efficient protonation of PAni and the rapid insertion of Cl− counterions to maintain charge neutrality. This results in a highly sensitive and selective HCl sensor over several common mineral acids, salts, and anions. This portable, simple and cost-effective sensing system provides rapid detection of HCl at concentrations as low as 10 ppm (far below the hazard limit) in natural water systems with response times ranging from 1.4 to 1.9 s and relative sensitivities between 0.5 and 0.9.