Detection and discrimination of volatile organic compounds by noble metal nanoparticle functionalized MoS2 coated biodegradable paper sensors

Abstract

In the current study, noble metal nanoparticle functionalized MoS2 coated biodegradable low-cost paper sensors were fabricated for the selective detection of low concentrations of volatile organic compounds (VOCs). A MoS2 layer was grown on flexible cellulose paper by a two-step hydrothermal route and functionalized further by using noble metal nanoparticles like Au, Pd and Pt by a spray coating technique. MoS2 nanoflakes aggregating into a micro-flower morphology was confirmed by field emission scanning electron microscopy. X-ray photoelectron spectroscopy authenticated the existence of noble metal nanoparticles on the MoS2 surface. Sensors were then tested with seven different VOCs (≤100 ppm) of ketones, alcohols and aromatic hydrocarbon groups. Au–MoS2 and Pd–MoS2 showed inherent acetone and benzene selectivity with 50.5% and 45.7% responses, respectively, after exposure to 100 ppm concentrations at 50 °C. Paper sensors exhibited highly stable baseline resistances, less sensitivity towards humidity (∼75% RH) and an acceptable response/recovery time within 3–6 min at low temperature (50 °C). An additional effort was devoted to discriminating and recognizing different VOCs by using suitable classification algorithms utilizing four types of paper sensors, i.e. pure, Au, Pd and Pt MoS2. Principal component analysis and logistic regression schemes successfully classified five VOCs among the seven. Moreover, the sensing mechanism of the noble metal modified MoS2 paper sensor is discussed in light of the Schottky barrier model.