Gold Nanoparticles: Synthesis, Mechanism and Applications as Colorimetric Metal Ions Sensor

The environment, consist of the lithosphere, atmosphere, hydrosphere and biosphere, is gradually threatened by various pollutants, among which heavy metal ions pose significant ecological and health risks. Natural phenomena in everyday life contribute to metal ion contamination in the environment. Prolonged exposure to heavy metals can cause severe health issues, including neurological disorders, organ damage and increased cancer risk. Hence, the development of sensitive, selective and efficient detection probes for metal ions, especially in aqueous media, is essential. Gold nanomaterials have gained importance as promising sensors due to their unique size-dependent optical, electronic and chemical properties. Their strong localized surface plasmon resonance (LSPR), high surface-to-volume ratio and ease of functionalization make them excellent candidates for colorimetric of metal ions. This review emphasize on the application of functionalized and label-free gold nanoparticles for metal ion detection. Recent advances and examples from the literature show that these nanoprobes are effective for environmental monitoring, and we cover their production, surface modification strategies and sensing processes.