Rapid colorimetric detection of mercury using biosynthesized gold nanoparticles

There is an increasing focus on expanding the applicability of biologically synthesized nanomaterials. Herein, we show the use of Cinnamomum tamala (cinnamon) leaf extract for the synthesis of gold nanoparticles with controllable optical properties. This ability to synthesize optically tunable AuNPs was exploited for the detection of mercuric ions (Hg2+) by capitalizing upon the amalgamation tendency of mercury with gold. The changes in both the longitudinal and transverse plasmon absorption bands of gold nanoparticles (AuNPs) suggest the potential of using both of these SPR features either independently using traditional analyses or in combination using discriminant analysis for the detection of mercury in aqueous media. Minimal cross-reactivity with other environmentally relevant metal ions confirms that the change in the optical property is exclusively due to the strong amalgamation of mercury and gold. Natural plant-based esters were found to act as capping agents during biological synthesis of AuNPs, and the involvement of these esters during Hg2+ ions sensing revealed underlying mechanistic processes.