Adsorption of carbendazim pesticide on plasmonic nanoparticles studied by surface-enhanced Raman scattering

7 págs.; 5 figs.; 1 app. Supplementary materialSurface-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. These two key bands correspond to the in-plane NH deformation of amidic and imidazolic groups, respectively. 2015 Elsevier Inc. All rights reserved.We are grateful to the Spanish MINECO (CTQ2012-31846, FIS2014-52212-R) and Junta de Andalucía (FQM-5156 and 6778), and to the Brazilian agencies CAPES, CNPq and FAPESP, for financial support. The authors thank to SCAI and Rafael Larrosa (UMA) for computational facilities.Peer Reviewe

Vibrational spectra of phenylacetate and phenylglycinate ions

Abstract The force fields of phenylacetate (PAC) and phenylglycinate (PGLY) ions have been calculated at B3LYP/6-31 þ G* level of theory and improved by using Pulay's scaling methodology by directly transferring scale factors from related molecules. On this basis, a general assignment of the Raman spectra of these ions has been proposed.

Detection of Pesticide Carbendazim by Surface-enhanced Raman Scattering (SERS) on Nanoparticles with different morphologies.

4th International Colloids Conference: Surface Design & Engineering, Madrid, Spain, 15–18 June 2014Peer Reviewe

Detection and quantitative analysis of carbendazim herbicide on Ag nanoparticles via surface-enhanced Raman scattering

7 págs.; 4 figs.;Carbendazim (MBC) is a fungicide widely used in agriculture, and there are serious concerns regarding the health risks that could be caused by this fungicide. Here, we explore its ultrasensitive detection by surface-enhanced Raman scattering (SERS). First, to obtain maximum SERS signal, the adsorption of the target molecule onto metallic surface is essential. Therefore, we study the adsorption of the MBC onto the nanoparticle surface by SERS under different experimental conditions, such as different synthesis methods of nanoparticle, variable excitation wavelength, and fungicide concentration with the aim to detect MBC at low concentrations. Experiments are carried out with three kinds of colloidal nanoparticles: Ag and Au reduced by citrate and Ag reduced by hydroxylamine. However, mainly Ag colloids are highly efficient in the SERS detection of MBC. In addition, theoretical calculations of MBC Raman spectrum and that of the surface complex are used to help with the understanding the mechanisms responsible for the interaction between MBC and Ag. Ultraviolet-visible absorption spectroscopy showed displacement to the red of the plasmon resonance of Ag colloid in the presence of MBC. Copyright © 2015 John Wiley & Sons, Ltd.This work is supported by CAPES, CNPq, FAPESP, POSMAT/UNESP,MINECO (project ref. FIS2014-52212-R, CTQ2012-31846) and Juntade Andalucía (FQM-5156 and 6778) for financial support.Peer Reviewe

Intramolecular and metal-to-molecule charge transfer electronic resonances in the surface-enhanced raman scattering of 1,4-Bis((E)-2-(pyridin-4-yl)vinyl)naphthalene

Electrochemical surface-enhanced Raman scattering (SERS) of the cruciform system 1,4-bis((E)-2-(pyridin-4-yl)vinyl)naphthalene (bpyvn) was recorded on nanostructured silver surfaces at different electrode potentials by using excitation laser lines of 785 and 514.5 nm. SERS relative intensities were analyzed on the basis of the resonance Raman vibronic theory with the help of DFT calculations. The comparison between the experimental and the computed resonance Raman spectra calculated for the first five electronic states of the Ag2-bpyvn surface complex model points out that the selective enhancement of the SERS band recorded at about 1600 cm−1, under 785 nm excitation, is due to a resonant Raman process involving a photoexcited metal-to-molecule charge transfer state of the complex, while the enhancement of the 1570 cm−1 band using 514.5 nm excitation is due to an intramolecular π→π* electronic transition localized in the naphthalenyl framework, resulting in a case of surface-enhanced resonance Raman spectrum (SERRS). Thus, the enhancement of the SERS bands of bpyvn is controlled by a general chemical enhancement mechanism in which different resonance processes of the overall electronic structure of the metal-molecule system are involved.This research has been supported by EU-FEDER, the Spanish Ministerio de Economía y Competitividad (Project CTQ2015-65816-R and FIS2017-84318-R) and Junta de Andalucía (UMA18-FEDERJA-049). P.L. and E.I. acknowledge the financial supports from the projects FONDECYT 1140810 and Beca Doctorado Nacional Nº 21140360 from CONICYT.Peer reviewe

Espectroscopía SERS aplicada a la detección de multicomponentes en una muestra

XXII Reunión Nacional de Espectroscopía. VI Congreso Iberico de Espectroscopía, Porto 8th to 10th September 2010S0505/TIC-0191/MICROSERESPeer Reviewe

Multicomponent direct detection of polycyclic aromatic hydrocarbons by surface-enhanced Raman spectroscopy using silver nanoparticles functionalized with the viologen host lucigenin

Silver nanoparticles (NPs) functionalized with the molecular assembler bis-acridinium dication lucigenin (LG) have been used as a chemical sensor system to detect a group of polycyclic aromatic hydrocarbon (PAH) pollutants in a multicomponent mixture by means of surface-enhanced raman scattering (SERS). The effectiveness of this system was checked for a group of PAHs with different numbers of fused benzene rings, namely anthracene, pyrene, triphenylene, benzo[c]phenanthrene, chrysene, and coronene. In order to determine the host capacity of this sensor system, the self-assembly of the LG viologen on a metallic surface has been checked by analyzing SERS intensities of PAH bands at different LG concentrations. The NP-LG-analyte affinity is derived from the analysis of PAH band intensities at different concentrations of pollutants, the adsorption isotherm of each PAH on NP-LG cavities has been studied, and the corresponding adsorption constants have been evaluated. The limit of detection at trace-level concentration is confirmed by the presence of their characteristic fingerprint vibrational bands. The SERS spectra of PAH mixtures confirm that LG viologen dication shows a higher analytical selectivity to PAHs constituted by four fused benzene rings, mainly pyrene and benzo[c]phenanthrene, in agreement with their higher affinity which is also related to their better fit into the intermolecular LG cavities. As a conclusion, SERS spectra recorded on modified NP-LG surfaces are a powerful chemical tool to detect organic pollutants. © 2011 American Chemical Society.This work was supported by Spanish MICINN (projects CTQ2009-08549 and FIS2010-15405) and by Comunidad Aut onoma de Madrid (project S2009/TIC-1476 MICROSERES II).Peer Reviewe

Application of surface-enhanced resonance Raman scattering (SERS) to the study of organic functional materials: Electronic structure and charge transfer properties of 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene

9 pags., 6 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 3.0The electron donor-acceptor properties of 9,10-bis((E)-2-(pyridin-4-yl)vinyl) anthracene (BP4VA) are studied by means of surface-enhanced Raman scattering (SERS) spectroscopy and vibronic theory of resonance Raman spectroscopy. The SERS spectra recorded in an electrochemical cell with a silver working electrode have been interpreted on the basis of resonance Raman vibronic theory assisted by DFT calculations. It is demonstrated that the adsorbate-metal interaction occurs through the nitrogen atom of the pyridyl moiety. Concerning the electron donor-acceptor properties of the adsorbate, it is shown that the charge transfer excited states of BP4VA are not optically active, in contrast, an internal transition to an excited state of BP4VA, which is localized in the anthracene framework, is strongly allowed. The charge transfer states will be populated by an ultrafast non-radiative process, that is, internal conversion. Thus, irradiation of BP4VA interacting with an appropriate surface creates an effective charge separation.This research has been supported by the Spanish Ministerio de Economıa y Competitividad (Projects: FIS2017-84318-R and CTQ2015-65816-R). EI and PL acknowledges the financial supports from the projects FONDECYT 1140810 and Beca Doctorado Nacional No. 21140360 from CONICYT. The authors thank Rafael Larrosa and Dar´ıo Guerrero for the technical support in running the calculations and the SCBI (Supercomputer and Bioinformatics) center of the University of Malaga for computer resources