State-of-the-art strategies for the colorimetric detection of heavy metals using gold nanorods based on aspect ratio reduction

The differential polarization of the incident light along the short and long axes of AuNRs provide unique optical properties that can be used for sensing applications. Since the longitudinal surface plasmon resonance responds to variations in the local environments, it can be used as a sensitive tool for the detection of different analytes based on the modification in the aspect ratio of AuNRs caused by the preferential interaction of metal ions with particular AuNR facets. This feature can be used for the detection of metals that are toxic or important for the functioning of the body. A summarized report of the different metals detected and the current strategies devised to attain improved sensitivity and selectivity based on the variations in the AuNR aspect ratio have been discussed in this mini-review. The various etchants and conditions used and the mechanism proposed have also been elaborated. We conclude the discussion by highlighting the future prospects and the challenges that need to be overcome for the development of probes for the on-site detection of metals in the environment.