Sensitive determination of arsenic in water using fluorescent CdS nanostructures

This study presents a simple and sensitive fluorescence-based sensing platform for arsenic (As) detection in water using cadmium sulfide (CdS) nanostructures. Three morphologically distinct CdS nanostructures (nanorods, nanoparticles, and nanocubes) were synthesized via thermal decomposition of cadmium(II) bis(dibutylcarbamodithioate) and evaluated as fluorescent probes. Among them, CdS nanocubes exhibited the highest fluorescence quenching efficiency (86%), attributed to their high surface energy and enhanced interaction with arsenic species. The sensing system showed a linear response over the concentration range of 0-20 mg L^-1, with a limit of detection of 0.012 mg L^-1, a limit of quantification of 0.041 mg L^-1, and a relative standard deviation of 2.11%, demonstrating excellent sensitivity and precision. Practical applicability was validated using arsenic-spiked water samples, with results in close agreement with those obtained using the commercial QUICK™ arsenic field test kit. Density functional theory (DFT) calculations further revealed favorable adsorption of arsenic species on the CdS (001) surface, providing atomic-level insight into the fluorescence quenching mechanism. These findings demonstrate a cost-effective, robust, and mechanistically informed sensing strategy for arsenic monitoring in environmental waters.