Ion-mediated etching of Au-Ag core-shell nanorods for LSPR-based discrimination of hazardous ions

The detection of metal ions represents a critical analytical challenge due to their persistent environmental accumulation and severe toxic effects on ecosystems and human health. Even at trace concentrations, toxic metal ions can cause irreversible biological damage, necessitating the development of sensitive, selective, and rapid monitoring platforms. Advanced detection systems are urgently needed for environmental surveillance, industrial effluent control, and food/water safety applications where regulatory compliance and early warning capabilities are paramount.

This work presents an etching-based sensor array to identify and discriminate Pb²⁺, Hg²⁺, Cu²⁺, NO₂^-, Cr⁶⁺, and As³⁺ as hazardous ions. Au@Ag core@shell nanorods were utilized as sensing elements in different pH values in the presence of thiosulfate and thiourea as key elements in the oxidation of nanoparticles. Analytes' response patterns in the range of 1.0-30 μM were analyzed via various methods, including heatmap, bar plot, and linear discriminant analysis (LDA), showing perfect discrimination. To ensure the sensor's applicability in real samples, we conducted meticulous testing on different sources, including tap water, well water, tilapia pond water, tomato soil extract, and urine samples.

The sensor demonstrated excellent performance in classifying mixture samples and providing precise and accurate detection in real samples. This innovation offers a promising future for etching-based sensor arrays by utilizing core-shell nanoparticles as sensitive sensing elements and a significant contribution to global efforts in safeguarding public health and the environment from the threat of pollutants.