A DFT Approach to the Surface-Enhanced Raman Scattering of 4-Cyanopyridine Adsorbed on Silver Nanoparticles

Abstract

A Surface-Enhanced Raman Scattering (SERS) spectrum of 4-cyanopyridine (4CNPy) was recorded on silver plasmonic nanoparticles and analyzed by using Density Functional Theory (DFT) calculations. Two simple molecular models of the metal–4CNPy surface complex with a single silver cation or with a neutral dimer (Ag+–4CNPy, Ag2–4CNPy), linked through the two possible interacting sites of 4CNPy (aromatic nitrogen, N, and nitrile group, CN), were considered. The calculated vibrational wavenumbers and intensities of the adsorbate and the isolated species are compared with the experimental Raman and SERS results. The analysis of the DFT predictions and the experimental data indicates that 4CNPy adsorbs preferentially on neutral/charged active sites of the silver nanoparticles through the nitrogen atom of the aromatic ring with a perpendicular orientation.

Insights into the Thermal and Photochemical Reaction Mechanisms of Azidoacetonitrile. Spectroscopic and MS‐CASPT2 Calculations

“…This figure represents the energy of the electronic states (kcal/mol) as a function of the RN‐NN internuclear distance (Å), taking as initial point the Franck‐Condon point, that is, the geometry of the minimum of AZN (M0, Figure a) and the final point corresponds to the minima of the two fragments (triplet nitrene (N0, 1 3 A“, Figure a) and N 2 separated by 4.7 Å. These potential curves have been obtained by applying the full linear interpolation method in all internal coordinates . Concerning the photodissociation of AZN, the most striking feature of Figure is that after excitation at the S 1 (1 1 A”) state of the azide, the system gains enough energy to decay into the final dissociation products without extra energy.…”

Palladium Oxide Nanoparticles: Preparation, Characterization and Catalytic Activity Evaluation

“…Optimized geometries were obtained at the DFT level of theory, employing the widely adopted Becke 3-parameter hybrid exchange functional (B3) combined with the Lee-Yang-Parr correlation functional (LYP) [24,25], along with the Lanl2DZ basis set and pseudopotential [26][27][28]. The latter was successfully used in the simulation of the Raman spectra of complexes containing heavy metals [29][30][31]. All parameters were let free to relax and all calculations converged toward optimized geometries corresponding to energy minima, as revealed by the lack of negative values in the frequency calculation.…”

Spectroscopic and Microscopic Analyses of Fe3O4/Au Nanoparticles Obtained by Laser Ablation in Water

“…We observe that the prominent SERS bands (at 353, 651, The addition of NaCl was necessary to obtain a satisfactory SERS spectrum of bpy. The presence of chloride anions, which strongly adsorb on the surface of the gold nanoparticles, has double validity because it can promote both the nanoparticle aggregation necessary for an efficient SERS response and the formation of active sites capable of strongly binding ligand molecules, similar to what occurs with silver nanoparticles activated by chloride anions [46][47][48]. In practice, in our bimetallic suspension it was not possible to obtain a valid SERS spectrum of 2,2 -bipyridine, even at 10 −4 M concentration, unless we added NaCl.…”

“…We also tested the reliability of this basis set by examining the free 2,2 -bipyridine molecule in its typical trans conformation and comparing our DFT results with those reported in the literature [48] for the same molecule, with the same functional but with a different basis, 6-31+G*. The Lanl2DZ basis set used by us provided results generally comparable with those reported in the literature, as shown in the Supplementary Materials, regarding both structural parameters (Table S1) and vibrational frequencies (Table S2).…”