JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2002; 33: 455–459 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jrs.853 Surface-enhanced Raman scattering of 3-phenylpropionic acid (hydrocinnamic acid)

Raman and surface-enhanced Raman scattering (SERS) spectra of 3-phenylpropionic acid on silver colloids at several concentrations and pH values were recorded. The analysis of the spectra indicated that 3-phenylpropionic acid links to the metal through its carboxylate group, keeping the aromatic ring almost perpendicular to the surface. Moreover, the acid undergoes an a, b-dehydrogenation in some extension in such a way that the recorded SERS is the result of the competitive adsorption of 3-phenylpropionic and trans-cinnamic acids. Likewise, the contribution of the charge-transfer mechanism to the enhancement of the SERS of 3-phenylpropionic acid was estimated, making evident its important participation in the enhancement of modes 6a, 9a and 8a. Copyright 2002 John Wiley & Sons, Ltd