Detection of ammonia in human breath using quartz crystal microbalance sensors with functionalized mesoporous SiO2 nanoparticle films

Quartz crystal microbalance (QCM) sensors with porous films comprising silica nanoparticles and poly(allylamine hydrochloride) (PAH) were fabricated. The films were deposited via an electrostatic self-assembly method, and they exhibited considerable sensitivity to relative humidity. The infusion of poly(acrylic acid) (PAA) into multi-layer porous films (5 or 10 cycles) enabled the construction of a highly sensitive and selective QCM sensor device for the detection of gaseous ammonia. Two types of QCM sensors, with and without PAA, were used as sensors for the simultaneous quantitative detection of humidity and ammonia. A comprehensive Fourier transform infrared (FTIR) investigation of the fabricated films was conducted to elucidate the mechanism of the chemical interaction at the sensor device interface. Preliminary tests were conducted to detect low concentrations of ammonia in human breath, which are of clinical relevance. The results of these tests showed that the sensor can detect ammonia in human breath at pathological levels (greater than 3 ppm). (C) 2015 Elsevier B.V. All rights reserved.