Binding Interactions and Raman Spectral Properties of Pyridine Interacting with Bimetallic Silver–Gold Clusters

Abstract

The binding interactions between pyridine and bimetallic silver-gold clusters are investigated using density functional theory (DFT). The binding energies of pyridine-bimetallic cluster complexes indicate that the bonding depends strongly on the binding site (Au or Ag atom) and bonding molecular orbitals in a given configuration. The donation of the lone-pair electrons of the nitrogen of pyridine to an appropriate unoccupied orbital of each metal cluster plays an important role. The low-lying excited states and charge-transfer states of four stable complexes of interest are calculated on the basis of a time-dependent DFT method. In nonresonance Raman scattering processes, the influence of binding interactions on the relative Raman intensity of totally symmetric pyridine vibrational modes is discussed. These calculated relative Raman intensities are compared with observed surface-enhanced Raman spectra of pyridine adsorbed on silver-gold alloy surfaces.

The mechanism of N–Ag bonding determined tunability of surface-enhanced Raman scattering of pyridine on MAg (M = Cu, Ag, Au) diatomic clusters

“…The conventional DFT method is only suitable for computing chemical enhancements in SERS. 12,29 In contrast, the recently developed TDDFT 26 method implemented in the ADF program package 30 can simulate both chemical and EM enhancement for pyridine adsorbed onto metal clusters. 21,22,27 The new method is based on a short-time approximation to the Raman cross-section.…”

“…2,4,5,10 The presence of the heteronuclear metal atoms changes the electronic properties of clusters, as well as their Fermi levels, band gaps, and electronic orbitals. 11,12 The complicated and changeable structures of the mixed-metal clusters allow optimization of the structure to fulfil the requirements of SERS detection.…”

Mechanical tuning of conductance and thermopower in helicene molecular junctions

“…These systems were selected for three reasons: (i) they are fully aromatic and highly conductive, (ii) they are synthetically accessible and were previously prepared by some of the authors [56] and (iii) they provide for reasonably good binding to gold surfaces via the nitrogen functionalities. [57][58][59] For this reason, azamolecules such as 4,4'-bipyridine are often used in single molecule conductance experiments, for example break junction measurements. [60] Based on our DFT calculations, position 2 in helicenes appears more suitable for binding than, for example, position 1, for steric reasons.…”

Density functional study of molecular nitrogen adsorption on gold-copper and gold-silver binary clusters

“…The bimetallic Au/Cu nanoparticles confined in SBA-15 have much better performance than monometallic particles in catalyzing CO oxidation even with the presence of excess H 2 [11]. Pyridine prefers binding to silver when both silver and gold atoms co-exist at active sites of a mixed Au/Ag cluster [12]. Li et al studied the small cationic Au n Cu m + (n+m≤6) clusters and their monocarbonyls Au n Cu m CO + by first-principles calculations [13].…”

“…In recent years, bimetallic coinage metal clusters have attracted considerable attention both experimentally and theoretically primarily because they often exhibit distinct physical and chemical properties from the pure coinage clusters [2][3][4][5][6][7][8][9][10][11][12][13][14]. The bimetallic Au/Cu nanoparticles confined in SBA-15 have much better performance than monometallic particles in catalyzing CO oxidation even with the presence of excess H 2 [11].…”