We report the fluorescence and surface-enhanced Raman scattering (SERS) analysis of methyl red (MR) isomers (o-MR, m-MR, p-MR) on silver (Ag) colloids at different pH conditions. The changes in simultaneous fluorescence quenching around 400 nm accompanied by enhancement around 540 nm with pH are closely related to energy transfer efficiency and the interaction between the carboxylic group and the Ag surface. The change of SERS signals with pH values can be ascribed to different adsorption orientations of MR on the Ag surface, from near flat (o-MR) to near perpendicular (p-MR).
Vol. 6, Iss. 10 Virtual Journal for Biomedical Optics
Szetsen Lee, Jian-How Wong, and Shiao-Jun Liu, "Fluorescence and Raman Study of pH Effect on the Adsorption Orientations of Methyl Red on Silver Colloids," Appl. Spectrosc. 65, 996-1003 (2011)