Small and Sharp Triangular Silver Nanoplates Synthesized Utilizing Tiny Triangular Nuclei and Their Excellent SERS Activity for Selective Detection of Thiram Residue in Soil

The great harm of thiram residue in soil to environment and human health is usually ignored. Due to the complexity of soil compositions, the detection of thiram residue in soil faces considerable difficulties. In this work, a highly sensitive and selective surface-enhanced Raman scattering (SERS) substrate based on the triangular silver nanoplates (TSNPs) with small size and sharp corners is developed and used for the detection of thiram residue in soil for the first time. These TSNPs are synthesized by replacing the conventional seeds in the seed-mediated chemical reduction route with the tiny and uniform triangular silver nuclei (TSN) which can provide more growing space for generating sharp corners during the growth of TSNPs. It is interesting that the TSNPs with the smaller size have the better SERS performance. The possible mechanism behind this phenomenon is explained by the electromagnetic enhancement theory. On the basis of the Raman activity of the smallest TSNPs, a SERS-active substrate is prepared for detecting the thiram residue in soil. The thiram solution detection shows that the limit of detection (LOD) of these smallest TSNPs is lower than other nanoparticles, such as nanospheres, nanocubes, etc. For sensing the thiram residue in soil, the addition of poly­(sodium 4-styrenesulfonate) realizes the specific adsorption of thiram by TSNPs. This method exhibits a good linear response from 0.12 to 4.8 μg/g with a low LOD of 90 ng/g, which is better than conventional methods. This work shows the great potential of the small TSNPs as a novel SERS substrate and its broader applications in pesticides detection.