Research On Electrochemical Surface-Enhanced Raman Scattering Spectroscopic Characteristics Of2-Picolinic Acid

Surface-Enhanced Raman Scattering (SERS) used in electrochemistry with its strong Raman scattering signal can make a profound study of electrochemical adsorption behavior of the absorbed molecules in the metal electrode surface, the electrochemical reaction process and the electrode/solution interface features and other aspects. This paper took2-picolinic acid molecule as a probe molecule because of its special structure with an N atom in pyridine ring, carboxylate ion and a π electron system can produce great Raman scattering signal, Its spectroscopic characteristics with different external conditions can further reveal the characteristics of the electrochemical behavior of molecules and molecular adsorption on the electrode surface.This paper had studied detailed the electrochemical behavior of the2-picolinic acid molecule on the electrode surface.The results showed that a reduction reaction was rose by2-picolinic acid on the surface of the silver electrode with the irreversible diffusion-controlled electrochemical process. Forms of2-picolinic acid molecule under different acidity conditions were determined according to Numerical Fitting, while the electrochemical surface-enhanced Raman scattering (EC-SERS) spectroscopy monitoring the electrochemical reduction process from molecular change with the vibration characteristics on the electrode surface provided the basis for the electrode reaction, and the research suggested that the electrode reduction reaction was the carboxylic acid anions on the pyridine ring, lost first two-electron conduced to the aldehyde.SERS and EC-SERS spectroscopic characteristics of2-picolinic acid molecule in the different base solution conditions, acidities, potentials, accumulation times and concentrations were examined systematically in the work, and the study showed that the different external conditions affected significantly molecular vibration characteristics and adsorption characteristics of the2-picolinic acid molecule on the electrode surface. Changing in vibration peaks of Pyridine ring breathing (including the N atom in pyridine ring) and the carboxylate ion stretching vibration determined the molecular adsorption characteristics and adsorption orientation on the electrode surface after the structure of the molecular had been analysed. Comparing the molecular normal Raman spectra and SERS spectra could be seen, the molecules on the roughed silver electrode showed great enhanced raman scattering signal, a competitive adsorption on the electrode surface was found when Cl" was added to2-picolinic acid solution; Acidity changed the forms of the existence of2-picolinic acid molecule in solution; The interaction between different characteristic groups of molecule and the silver electrode surface was caused by electrode potentials;Accumulation times changed the electrode surface characteristics and the concentration of the molecule affected molecule adsoiption characteristics on the electrode surface.Comparing two main molecular vibration peaks (pyridine ring breathing vibration peak and the carboxylate anion symmetric stretching vibration peak) with the variation of external conditions, a similar enhancement mechanism could be found that carboxylic acid anions formed molecular metal bond with substrate silver atoms and pyridine ring chemical adsorbed on the silver electrode surface via the lone-pair electrons of the N atom, showing the charge transfer enhancement mechanism.