Shape-Induced Enhanced Raman Scattering (SIERS) Platforms Modified with Gold Nanorods for Ultradiluted Atrazine Pesticide Detection

Abstract

Herein, we explored the shape-induced enhanced Raman scattering (SIERS) effect to detect Atrazine pesticides in different concentrations (1.6 × 10–8–1.6 × 10–20 mol L–1). For this, the performance of the SIERS effect compared to the conventional Raman signal was evaluated using a silicon substrate with a V-shaped (Si–V) microchannel and a flat silicon substrate (flat Si). Experimental data free of metallic nanostructure show that the SIERS effect increases up to a 7-fold signal for the Atrazine molecule compared to the conventional Raman signal. Combining SIERS and surface-enhanced Raman scattering (SERS) effects (SIERS@SERS) using metallic nanostructures is the key feature used to achieve lower limit detection of the target molecule. The performance of SIERS@SERS was evaluated by using gold nanorods (AuNRs) metallic structure deposited onto Si–V and flat Si for the detection of Atrazine in different concentrations (1.6 × 10–8–1.6 × 10–20 mol L–1). The geometric design of V-shaped microchannels also enables a “trap” for the molecule confinement and builds up an excellent electromagnetic field distribution by AuNR aggregates. The AuNRs aggregation is also favored by incubating a AuNRs colloidal suspension mixed with Atrazine using different solvents (water and methanol). In this sense, the results reveal that the solvent plays an important role in the signal intensity as well as spectra definition and band identification. The IDMAP statistical projection reveals good data discrimination with a silhouette coefficient of 0.64 for Si–V substrate (1.6 × 10–8–1.6 × 10–20 mol L–1) against 0.51 for flat Si (1.6 × 10–8–1.6 × 10–16 mol L–1), indicating that the SIERS@SERS effect provides more sensitivity for the sensor. The Si–V platforms are a robust option for commercial sensors, since they can be reusable with or without plasmonic nanostructures.