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Concentration dependence of the SERS of some water‐soluble cationic porphyrins on an electrochemically prepared silver surface
Author(s) -
Qu J.,
Arnold D. P.,
Fredericks P. M.
Publication year - 2000
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/1097-4555(200006)31:6<469::aid-jrs558>3.0.co;2-t
Subject(s) - porphyrin , aqueous solution , chemistry , chloride , raman scattering , cationic polymerization , raman spectroscopy , molecule , inorganic chemistry , photochemistry , polymer chemistry , organic chemistry , physics , optics
Surface‐enhanced Raman scattering (SERS) spectra, taken with 632.8 nm excitation, are reported for the water‐soluble tetrakis(3‐ N ‐methylpyridyl)porphyrin chloride [TMPyP(3)], tetrakis(4‐ N ‐methylpyridyl)porphyrin chloride [TMPyP(4)] and tetrakis(4‐ N,N,N ‐trimethylanilinium)porphyrin chloride (TMAP) using an electrochemically prepared Ag surface. Known amounts of the samples were placed on the surface as aqueous solutions and the water was allowed to evaporate. It was found that the spectra vary as increasing amounts of the compounds are placed on the surface to give surface concentrations in the approximate range 80–0.07 pmol mm −2 . We suggest that the reason for the changes is that the orientations of the porphyrin macrocyclic molecules change, i.e. the porphyrin molecules lie flat on the Ag surface at low concentration but are arranged edge‐on, perpendicularly or slightly tilted, on the surface at higher concentrations. Copyright © 2000 John Wiley & Sons, Ltd.