Paper-based colorimetric nanosensor for detecting halides in aqueous media

The selective detection of halides in aqueous samples is crucial for addressing environmental and physiological concerns. Consequently, the development of an affordable, portable, and user-friendly sensing platform for rapid halide detection holds substantial promise. In this study, we present a novel paper-based nanosensor as an appealing alternative for selectively detecting halides in water. This nanosensor leverages the optical properties of silver nanoparticles (ranging from 50 to 250 nm) embedded in epoxy resin and printed on filter paper. We elucidate the colorimetric behavior of this nanosensor in response to specific halides (chloride, bromide, and iodide) upon contact. Importantly, this sensor discerns, through a single measurement, the presence of these halides in aqueous media with remarkable selectivity. The nanosensor manifests distinct color changes in reaction to different halides, particularly at elevated concentrations (ranging from 2 to 400 mM), surpassing the saturation levels observed in other proposed sensors. These discernible color changes are due to the oxidation of silver nanoparticles, changing their morphology and aggregation density, and can be readily detected and analyzed directly from a captured image. Consequently, it demonstrates considerable potential for integration into automated qualitative monitoring devices based on chromaticity analysis.