Surface-Enhanced Raman Spectroscopy Studies on the Interaction of Imidazole with a Silver Electrode in Acetonitrile Solution

Abstract

Surface-enhanced Raman scattering (SERS) spectrum of imidazole adsorbed at a silver electrode in nonaqueous acetonitrile solution has been investigated as a function of applied potential. The electrolyte is 0.1 M LiClO4. Results show that imidazole adsorbs on silver as a neutral molecule via the pyridine nitrogen atom. Coadsorption of perchlorate anion with imidazole, possibly by forming intermolecular hydrogen bonding, is also suggested by the enhancement of the ClO4 - band at 933 cm-1. An edge-on orientation of imidazole at more positive potentials is proposed by the observation of the increase in frequency of the ring breathing modes, along with the enhancement of most of the in-plane modes of imidazole. When the potential is made more negative, particularly near −0.5 V, the imidazole ring may change from vertical to be slightly inclined to the silver surface at an intermediate angle from the surface normal. At the same time, a slight rotation of the imidazole ring plane may occur, evidenced by the observation of the changes in relative intensity of ν(C2H) to asymmetric ν(HCCH) vibration. In addition, the decomposition reaction of the solvent acetonitrile at the silver surface is also assumed by the appearance of a characteristic band of cyanide ion at ca. 2110 cm-1. Competitive adsorption of imidazole at more positive potentials inhibits significantly the decomposition of acetonitrile.

Structural properties of bombesin‐like peptides revealed by surface‐enhanced Raman scattering on roughened silver electrodes

“…A m(CÀ ÀS) band corresponding to the À À(H 2 )CÀ ÀSÀ À group was expected to appear in the 640-680 cm 21 ) gave rise to several well-defined vibrational bands in the vibrational spectra of NMB and PG-L (Table II). [51][52][53] None of the ]phyllolitorin spectra because these peptides do not contain Phe 13 and His 12 residues, respectively. On the other hand, the strong bands due to the aromatic ring system of Trp 8 (W18, W17, W7, and W3) were observed in all the spectra.…”

Potential-dependent SERS profile of orthanilic acid on silver electrode

“…From the fact that SERS became effective after laser illumination, it was proposed that the photographitization of organic compounds on the metal surface, rather than the metal itself, was responsible for the SERS phenomenon. 40,41 Cao et al 42 also reported broad background features between 1300 and 1600 cm 1 and have attributed them to the presence of surface carbon impurities.…”

Elimination of oxidation and decomposition by SnCl2 in the SERS study of pyridoxine on a roughened Au electrode

“…These features just exhibit an 'edge-on' adsorption mode of pyridine ring. [38] However, we exclude the direct adsorption of PN on the roughened substrate for the interaction between Sn(II) and Au is stronger than that between PN and Au. That is why PN is not decomposed by the giant EMF in the absence of the 'first-layer' effect.…”