A Unique Bridging Facet Assembly of Gold Nanorods for the Detection of Thiram through Surface-Enhanced Raman Scattering

Abstract

Concerns have grown in recent years about the widespread use of the pesticide thiram (TRM), which has been linked to negative effects on local ecosystems. This highlights the critical need for quick and accurate point-of-need pesticide analysis tools for real-time applications. The detection of TRM using gold nanorods (Au NRs) with a limit of detection of 10–11 M (10 pM) and an enhancement factor of 2.8 × 106 along with 6.2% of signal homogeneity (with respect to the peak at 1378 cm–1) is achieved through surface-enhanced Raman scattering (SERS). The formation of an Au–S bond emphasizes the adsorption of TRM on Au NRs. The addition of Au NRs to TRM of higher and lower concentrations yields a side-by-side assembly (SSA) and a bridging facet assembly (BFA), respectively, and exhibited excellent hotspots for the ultralow detection of TRM. Bridging facets of Au NRs, such as (5 12 0) and (5 0 12) planes, are mainly responsible for the BFA. This kind of interaction is observed for the first time and not reported elsewhere. The detailed facets of Au NRs, namely, side facets, bridging facets, and pyramid facets were demonstrated with the 3D model of Au NRs. The computational studies confirming the SSA and BFA for Au NRs with varying concentrations of TRM are in well agreement with the experimental results. The interaction of Au NRs with TRM is highly sensitive, and the ultralow detection of hazardous TRM through SERS is an ideal technique for environmental protection, real-time applications, and analysis of one-of-a-kind materials.