Recent advances in the application of noble metal nanoparticles in colorimetric sensors for lead ions

Recent developments in nanotechnology and engineering have produced a plethora of nanomaterials with amazing physical/chemical properties and enhanced sensing potential for various heavy metals in the environment. Noble metal nanoparticles (NPs), particularly those made from gold and silver, have attracted a great deal of attention mainly due to ease of synthesis, a high degree of surface functionalization, biocompatibility, and tunable physico-chemical properties. The use of noble metal nanoparticles has enabled fast and multiplexed detection of metal ions with excellent sensitivity and selectivity. The optical characteristics of Au–Ag NPs and noble metal-based nanozymes enable the detection of metals based on colorimetry. Color changes of these metal nanoparticles upon interaction with lead ions are based on inter-particle interactions (aggregation/dis-aggregation) and changes in surface modification. This review presents up-to-date information on the applications of noble metal NPs in the colorimetric sensing of lead (Pb2+) ions with special attention on selectivity, sensitivity, and practicality. The extensive potential of noble metal nanomaterials as the next-generation and on-site sensing tools has been explored for the rapid detection of lead ions in environmental matrices.