Hierarchical Plasmonic Au@ZnO Chemosensor Enhanced the Sensitivity and Detection Limit of Pb²⁺ Metallic Ions

Pb²⁺ contamination poses significant environmental and health risks that can be detected from Au-doped ZnO (Au@ZnO) nanograins as selective and sensitive chemosensors. Microstructural analysis reveals that the crystallite size and bandgap decreased from 18 to 9 nm and from 3.2 to 2.91 eV, while the strain increased from 3.3 × 10^-3 to 6.39 × 10^-3 as the Au concentration increased from 0 to 5 at. %, respectively, and further confirmed by DFT calculations. XPS analysis confirmed the substitution of Zn with Au, inducing tensile stress and enhancing charge transfer. Localized surface plasmon resonance (LSPR) effects improved the light absorption and carrier generation with the highest Pb²⁺ detection limit (1.78 mM at 369 nm for Au = 2 at. %). Recent studies demonstrated the selectivity and stability across four cycles in the presence of competing ions (Co²⁺, Cd²⁺, and Hg²⁺). These findings of Au2@ZnO established a promising platform for Pb²⁺ detection, offering stability, sensitivity, and operational longevity for environmental remediation and heavy metal monitoring.