Selective and ultrasensitive detection of the herbicide glyphosate by means of plasmon catalysis on Ag nanoparticles

Abstract

This work aims at the detection of the important herbicide glyphosate based on the previous modification of glyphosate in two stages and final detection by surface-enhanced Raman spectroscopy (SERS). In a first step, the affinity of glyphosate for metal plasmonic surfaces was increased by inclusion of a sulphur containing group (dithiocarbamate). In a second step, the cyclization of the latter intermediate rendered a thiazole derivative of the herbicide. The latter compound exhibits higher Raman cross section which lead to stronger SERS enhancement factors. The second step was possible thanks to the plasmon catalysis driven by metal nanoparticles, specifically silver adatoms created at the surface, and irradiated at a proper wavelength. This methodology was optimized by selecting the most appropriate experimental conditions for the chemical reactions. Density Functional Theory treatment of all the involved molecules was done in order to obtain the theoretical spectra and to identify the structural marker bands. A key goal of this work was to develop an effective system of glyphosate detection based on portable PickMolTM technology developed and patented by the SAFTRA Photonics Ltd. company to ensure an easy, quick, low cost, in-situ, and univocal detection of glyphosate in the environment.