title: Adsorption of carbendazim pesticide on plasmonic nanoparticles studied by surface-enhanced Raman scattering.
abstract: Surface-Enhanced Raman Spectra (SERS) of methyl N-(1H-benzimidazol-2-yl)carbamate (MBC), usually named carbendazim, have been recorded on silver colloids at different pH values. In order to identify the neutral, protonated or deprotonated species of MBC that originate the SERS, the vibrational wavenumbers of these three isolated forms and linked to a silver atom have been predicted by carrying out DFT calculations. The results indicate that the active SERS species in the studied pH range correspond to the neutral MBC and its deprotonated ion in the amidate form. According to theoretical calculations, neutral MBC is linked to the metal through the imidazolic nitrogen atom, while the deprotonated MBC could be linked through the imidazolic nitrogen together with the amidic nitrogen atom or the carbonyl oxygen atom. Both adsorbed species, neutral and deprotonated, have the benzimidazolic ring orientated almost perpendicular to the silver surface and no molecular reorientation has been detected. pH of the bulk controls the relative abundance of the neutral MBC and its amidate anion which can be monitored through the intensities of the SERS bands recorded at about 1230 and 1270cm(-1). These two key bands correspond to the in-plane NH deformation of amidic and imidazolic groups, respectively.
authors.affiliation: FCT, Universidade Estadual Paulista, Presidente Prudente, SP, Brazil.
authors.forename: L N
authors.initials: LN
authors.lastname: Furini
authors.affiliation: FCT, Universidade Estadual Paulista, Presidente Prudente, SP, Brazil.
authors.forename: C J L
authors.initials: CJ
authors.lastname: Constantino
authors.affiliation: Instituto de Estructura de la Materia, CSIC, Serrano 121, E-28006 Madrid, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Sanchez-Cortes
authors.affiliation: Department of Physical Chemistry, Faculty of Science, University of Málaga, Unidad Asociada CSIC, E-29071 Málaga, Spain.
authors.forename: J C
authors.initials: JC
authors.lastname: Otero
authors.affiliation: Department of Physical Chemistry, Faculty of Science, University of Málaga, Unidad Asociada CSIC, E-29071 Málaga, Spain. Electronic address: tocon@uma.es.
authors.forename: I
authors.initials: I
authors.lastname: López-Tocón
keywords: Adsorption on colloidal suspensión; Carbendazim; SERS spectroscopy