Eco-friendly paper-based colorimetric sensor for portable and rapid detection of lead (II) ions in aqueous environment

Lead contamination in water bodies poses significant environmental and health risks, necessitating effective detection methods. This study presents a novel, cost-effective, and portable paper-based sensor for the visual detection of lead (II) ions in an aqueous medium using the colorimetric dyes Eriochrome Black T and Bromothymol Blue. The sensor's sensitivity to varying concentrations of lead (II) ions is explored using UV–visible spectroscopy, with pH-adjusted dye solutions in acidic, neutral, and basic conditions. Both Eriochrome Black T and Bromothymol Blue dyes exhibited distinct colorimetric responses to the presence of lead (II), with optimal detection occurring in neutral pH environment. A concentration range of 60–140 ppm of lead (II) ions was examined, and the detection limits were lowest for Bromothymol Blue dye, found to be around 6 ppm. Furthermore, the selectivity of the dyes was tested against other metal ions, showing high specificity for lead (II) ions. The sensor's stability was verified across a temperature range of 25–90 °C. Finally, a paper-based chemo sensor was fabricated to demonstrate the sensor's real-time applicability, where visual color changes confirmed lead (II) detection in water. The developed sensor offers a promising alternative for field-based detection of lead in contaminated water sources, providing a low-cost, easy-to-use, and reliable method for environmental monitoring.