Gold nanorods etching as a powerful signaling process for plasmonic multicolorimetric chemo-/biosensors: Strategies and applications

Abstract

Localized surface plasmon resonance (LSPR) is an optical phenomenon produced by an incident light’s impact on the conductive nanoparticles smaller than the light wavelength. Generally, LSPR is applied as a label-free sensing technique that exhibits a superior sensitivity depending on the size, shape, and structure of the conductive nanoparticles. Gold nanorods (AuNRs), when etched into small nanoparticles, are appeared as a powerful tool in the fabrication of numerous chemo-/bio-sensors due to the unique optical properties resulted from the excitation of LSPR in the range from visible to near-infrared. The etching of AuNRs is a non-aggregation-based plasmonic technique that leads to a decreased AuNRs aspect ratio and the blue-shifted longitudinal LSPR band. Etching of the AuNRs makes it feasible to fabricate a sensor with progress in selectivity, sensitivity, detection limits, and response time. In this review, at first, the optical properties of AuNRs are briefly explained. Then, the physical principles of the LSPR and LSPR-based detection strategies were discussed. After describing the etching process, the chemo-/biosensors and sensor arrays that have been reported so far are subtly summarized in several tables containing important information about AuNRs characteristics, sensing mechanisms, and analytical parameters. The tables have been arranged to make it possible to compare the sensor characteristics and evaluate their feasibilities. The way forward was also tried to be determined by highlighting each sensor mechanism and characterizations. Eventually, the ultimate perspective for AuNRs etching, including the challenges and future directions for applying these sensors for either research or commercial purposes, is considered.