Plasmonic Detection of Mercury via Amalgamation on Gold Nanorods Coated with PEG-Thiol

Gold nanorods (AuNRs) have emerged as a powerful element in the development of nanomaterial-based sensors due to their localized surface plasmon resonance extinction at visible and near-infrared wavelengths. In this study, we present a strategy for plasmonic detection of mercury using PEG-thiol-coated AuNRs (PEG@AuNRs). The PEG@AuNRs, prepared by a simple ligand exchange, demonstrate superior advantages including sensitivity, stability, and specificity than the as-synthesized hexadecyltrimethylammonium bromide-coated AuNRs. The plasmonic responses of PEG@AuNRs toward the same amount of Hg in the system can be significantly manipulated by adjusting the AuNR concentration in the system and the incubation time between AuNRs and Hg2+. Both Hg2+–S complexation and amalgam formation contribute to the unique behavior of plasmonic response which enable the design of a smart Hg2+-sensing platform with an adjustable peak plasmonic response region. This study not only demonstrates the advantages of mercury-sensing systems based on PEG@AuNRs but also advances the fundamental understanding of ligand impacts on plasmonic properties for the plasmonic detection of mercury.