pH Dependence of the Surface-Enhanced Raman Scattering ofp-Nitroaniline Adsorbed on Silver Sols

Abstract

The surface-enhanced Raman (SER) scattering of p-nitroaniline adsorbed on silver colloids was investigated and compared with previous results obtained on a silver electrode. The SER spectra change signiÐcantly on varying the pH of the colloidal dispersions and correspond to di †erent adsorbed species identiÐed by comparison with the normal Raman spectra. In acidic medium the neutral molecule is adsorbed on the metal substrate via the nitro group, whereas at alkaline pH p-nitroaniline adsorbs as an anion in a quinonoidic electronic state. 1997

Adsorption of dicarboxylic acids onto nano‐structured silver surfaces – surface‐enhanced Raman scattering studies of pH‐dependent adsorption geometries

“…Our work emphasizes the previously demonstrated [69][70][71] potential of this technique to study the adsorption orientations of molecules at the interface between nano-structured metal surfaces and a liquid phase. This issue is subject to contemporary research and a critical determinant for many catalytic processes.…”

Adsorption of aniline on silver mirror studied by surface‐enhanced Raman scattering spectroscopy and density functional theory calculations

“…Previous experimental results have indicated that the adsorption of aniline might occur via the π orbital of the aromatic ring or the lone pairs of the nitrogen atom of the amino group 41. In order to obtain further insight into the adsorption of aniline on the Ag mirror surface, DFT calculations were performed.…”

SERS and DFT study of nitroarenes adsorbed on metal nanoparticles

“…The employment of a mixed basis set in the DFT calculations has allowed reproducing satisfactorily both the spectral positions of the SERS bands and the frequency-shifts of these latter with respect to the Raman bands of the free ligand. This computational method will be extended to other nitroarenes, whose SERS spectra in Ag colloids are reported in the literature, like p-nitroaniline [5,7], 2-amino,5-nitropyrimidine [20] and p-nitrobenzoic acid [21], in order to get a better insight into their adsorption processes. In addition, we would like to re-examine the SERS spectra of p-nitrophenol adsorbed on Ag colloid, which have been recently interpreted [22] on the basis of a molecule/metal interaction via nitrogroup by means of DFT calculations performed with basis sets different from those employed in the present work.…”

“…The most important p-conjugated push-pull molecule is p-nitroaniline (hereafter PNA), where an internal charge transfer occurs between the electron donor aminogroup and the acceptor nitrogroup. The spectroscopic properties of PNA were widely investigated [4][5][6][7]. 2-Amino,5-nitropyridine (hereafter ANP) can be considered a push-pull chromophore like PNA, due to the resonance between the benzenoid and quinonoid forms (Fig.…”