The detection of the lead heavy metal (Pb) in water is crucial in many chemical processes, as it is associated with serious health hazards. Here, we report the selective and precise colorimetric detection of Pb²⁺ ions in water, exploiting the aggregation and self-assembly mechanisms of glutathione (GSH)-functionalized gold nanoparticles (GNPs). The carboxyl functional groups are able to create coordination complexes with Pb²⁺, inducing aggregation amongst the GSH-GNPs in the presence of Pb²⁺ due to the chelation of the GSH ligands. The resulting aggregation amongst the GSH-GNPs in the presence of Pb²⁺ increases the aggregate size depending on the available Pb²⁺ ions, affecting the plasmonic coupling. This causes a substantial shift in the plasmon wavelength to a longer wavelength side with increasing Pb²⁺ concentration, resulting in a red-to-blue colorimetric or visual change, enabling the instant determination of lead content in water.

A highly sensitive biosensing platform comprised of CdSe-ZnO core–shell nanostructures for targeted applications in protein detection is demonstrated. This innovative technique uses a microwave-assisted thermal decomposition method to produce a rapid, less hazardous, and user-friendly procedure to synthesize a semiconductor core surrounded by nanometer-thick metal oxide shells. The benefit of using a metal oxide shell includes mitigating the toxicity of the CdSe core, thus increasing its biocompatibility and minimizing its photochemical corrosion and oxidation. We present a simple one-pot microwave-assisted protocol for the formation of CdSe-ZnO core–shell quantum dots (QDs). These QDs optimize the recognition limit of bovine serum albumin (BSA) protein through a spectral signal at a considerably low concentration (2.5 × 10⁻⁶ M), thus demonstrating its potential to become a highly effective surface-plasmon-enhanced Raman spectroscopy (SERS)-like sensing platform. We report a QD material that can mimic a strong SERS-like behavior due to charge transfer affecting the local electric field.