Visual Detection of Mercaptan Gases Using Silver Nanoparticles-Based Colorimetric Sensor Array

Short-carbon chain mercaptans are easily evaporable organic compounds with high toxicity. The leakage of trace short-carbon chain mercaptan gases during transportation, storage, and chronic workplace exposure poses a serious threat to human health, as they cannot be promptly recognized and detected in advance. Based on chemically induced aggregation of nanoparticles to generate a colorimetric response, we propose a paper-based colorimetric sensor array that utilizes silver nanoparticles to achieve visual detection and differentiation of three highly toxic trace mercaptan gases: methyl mercaptan (CH3SH), ethyl mercaptan (C2H5SH), and butanethiol (C4H5SH). The silver nanoparticles, ranging from 3 to 9 nm in size, are capped with long-chain hydrophobic molecules (dodecanethiol, oleic acid, and oleyl amine) and immobilized on a porous hydrophobic polyvinylidene fluoride substrate, presenting excellent stability and ability to resist humidity. The sensor array exhibited superior sensitivity for the detection and discrimination of these three mercaptan gases with the limits of detection (LODs) of 80 ppb (CH3SH), 28 ppb (C2H5SH), and 109 ppb (C4H5SH), for only 10 min exposure. Importantly, these LODs are well below the American Conference of Governmental Industrial Hygienists (ACGIH) permissible exposure threshold of 0.5 ppm. Distinct colorimetric response patterns are observed for each of the analytes. Standard chemometric methods confirm the sensor array's excellent clustering ability for these three mercaptan gases and show an outstanding anti-interference capability against other interfering gases. The sensor array's response is irreversible and possesses outstanding performance in cumulative monitoring. The novel colorimetric sensor array based on solid-state AgNPs offers an innovative approach for the continuous, ultrasensitive, and visual detection of trace airborne pollutants.