Investigation on the Indium–Tin Oxide Nanoparticle-Based Chemoresistive Sensors to Detect Small-Molecular-Weight Substances Diluted in Water

We fabricated a chemoresistive sensor based on indium–tin oxide (ITO) nanoparticle detection layer printed on a polyethylene terephthalate (PET). The ITO sensor operates on a mechanism that detects substances through resistance change induced by electrochemical potential variations on the sensor surface, which correspond to changes in analyte concentration governed by the Nernst equation. In this study, we confirmed broad-spectrum detection capabilities of the ITO sensor by successfully detecting 31 kinds of substances and demonstrated by achieving a low limit of detection that fully satisfies the environmental protection limit (EPL) for effluents, also alongside an error margin of within 5% for all 31 substances. In addition, the possibility of selective detection was confirmed by presenting the response of the ITO sensor according to pH changes, concentration, and type of substance as a two-dimensional scattering pattern. Thus, this study demonstrates that ITO based on chemoresistive sensors can achieve real-time monitoring of various underwater substances with high sensitivity and broad detection capabilities.