Nanoplasmonic Au/Ag/Au nanorod arrays as SERS-active substrate for the detection of pesticides residue

Trace analysis of pesticides' residue found in an agricultural product is a vital topic, which is still a timeconsuming and unreliable approach. A fast and effective chemical sensing technique is therefore required. Surface-enhanced Raman spectroscopy (SERS) has been well developed for detecting target species at e.g., single molecule level. Herein, we used focus-ion beam and nano-indentation methods for fabricating Au/Ag/Au nanorods (NRs) and Au nanocavity array for subsequent SERS applications. The as-prepared SERS-active substrate was firstly evaluated by different wavelengths of Raman laser using rhodamine 6G as a probe molecule at low concentrations. The optimized Au/Ag/Au NRs array exhibited a strong SERS effect with an enhancement factor of 2.15 x 10(8). Furthermore, Au/Ag/Au NR substrates were competent to detect various types of pesticides' residue, i.e., permethrin, cypermethrin, carbaryl, and phosmet at low concentrations. Presumably high SERS signals may occur at the interface between pesticide molecules and NRs surface. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.