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Adsorption of mercaptoacetic acid on a colloidal silver surface as investigated by Raman spectroscopy
Author(s) -
Castro J. L.,
LópezRamírez M. R.,
Centeno S. P.,
Otero J. C.
Publication year - 2004
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20060
Subject(s) - chemistry , deprotonation , carboxylate , carboxylic acid , monolayer , hydrogen bond , raman spectroscopy , adsorption , metal , raman scattering , group (periodic table) , inorganic chemistry , photochemistry , polymer chemistry , molecule , organic chemistry , ion , biochemistry , physics , optics
The vibration ν(SH) has never been observed in the surface‐enhanced Raman scattering of mercaptoacetic acid recorded in a wide range of pH. This behavior enables us to deduce that the SH group is deprotonated and links to the metal forming an AgS bond as 1‐alkanethiols do. On the contrary, the carboxylic or carboxylate groups do not link to the metal and the carboxylic group is preserved even at pH values under which it should be deprotonated. This fact enables the stabilization of the adsorbed monolayer by removing the electrostatic repulsions between COO ‐ groups and by the formation instead of hydrogen bonds between carboxylic groups. Only under rather basic conditions (pH > 8) does the carboxylic groups dissociate, but the ν s (OCO) band is neither enhanced nor shifted toward low frequencies. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004