Surface-enhanced Raman scattering study of the adsorption of the anthraquinone pigment alizarin on Ag nanoparticles

• Published in: Journal of Raman spectroscopy Vol. 35; no. 11; pp. 921 - 927
• Main Authors: Cañamares, M. V., Garcia-Ramos, J. V., Domingo, C., Sanchez-Cortes, S.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.11.2004
• Subjects: Adsorption; Alizarin; Anthraquinones; dye; Mathematical models; Metal surfaces; pigment; Raman scattering; Silver; Surface chemistry; surface-enhanced Raman scattering
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.1228

FT‐Raman and surface‐enhanced Raman scattering (SERS) spectroscopy were applied in the vibrational characterization and study of the adsorption and acidity behavior of the highly fluorescent anthraquinone dye alizarin on Ag colloids prepared by chemical reduction with hydroxylamine hydrochloride. The SERS spectra were obtained at different conditions of pH, excitation wavelength and pigment concentration in order to deduce the adsorption mechanism of this molecule. On the basis of the results found we propose an adsorption model for alizarin, which has a different acidic behavior on the metal surface to that in solution. On the metal the deprotonation order of the OH groups changes with respect to the aqueous solution, the OH in position 1 being the first to be ionized instead of that in position 2 as occurs in solution. The two main alizarin forms identified on the metal surface correspond to the mono‐ and dianionic alizarin species. Copyright © 2004 John Wiley & Sons, Ltd.