Portable and Low-Cost Paper-Based Sensor Integrated with Smartphone for Chromium Ions Detection

Heavy metal contamination negatively impacts the environment, highlighting the need for affordable detection techniques for field monitoring. Paper-based sensors provide a low-cost, simple, and portable diagnostic technology for rapid detection of heavy metals in water. In this study, the paper sensor was fabricated by adsorbing 1,5 diphenyl carbazide as a chromogenic reagent for chromium onto filter papers coated with SiO2. The detection of targeted chromium has been evaluated using digital image-based colorimetric analysis, with parameters of chromogenic concentration, pH, and reaction time optimized. The SEM image shows a layer of silica on the surface of the paper, indicating that the silica-supporting material was successfully coated. Furthermore, new IR band appearances at 1538, 1602, and 1666 cm-1 confirm the successful attachment of 1,5-diphenylcarbazide to the surface of the paper. The paper-based sensor is susceptible to chromium ions, demonstrating a persistent purple color shift after 120 seconds of contact in a pH chromium solution of neutral to slightly basic conditions and higher 1,5-diphenylcarbazide concentrations. These results suggest that paper-based sensors have promising potential for low-cost and portable on-site detection of heavy metals in water.