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Adsorbed states of substituted α‐aminophosphinic acids on a silver electrode surface: comparison with a colloidal silver substrate
Author(s) -
Podstawka Edyta,
Kudelski Andrzej,
Dra̧g M.,
Oleksyszyn J.,
Proniewicz Leonard M.
Publication year - 2009
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/jrs.2301
Subject(s) - electrode , ring (chemistry) , raman scattering , substrate (aquarium) , adsorption , chemistry , benzene , aqueous solution , raman spectroscopy , crystallography , molecule , colloid , metal , analytical chemistry (journal) , organic chemistry , optics , physics , oceanography , geology
We investigated the interfacial structures of various aromatic (each compound contains one or two phenyls) di‐α‐amino ( L 1 – L 3 ) and α‐amino‐α‐hydroxyphosphinic ( L 4 – L 6 ) acids immobilized onto an electrochemically roughened silver electrode surface in an aqueous solution using surface‐enhanced Raman scattering (SERS). These structures were compared to those on a colloidal silver surface to determine the relationship between adsorption strength and geometry. The presence of an enhanced ν 19a ring band in the SERS spectra of L 6 , L 2 , and L 3 on the electrode indicated that the benzene rings of those molecules interact with the electrode surface through localized CC bond(s). We observed significant band broadening of the benzene ring modes for all α‐hydroxyphosphinic acids on both substrates, except for L 1 deposited onto the electrode surface. This suggests the possibility of direct interaction between the ring and Ag, although the benzene ring–surface π overlap is weaker for the colloidal silver than for the Ag electrode. The downward shift in wavenumber and alternations in the enhancement of a ν 12 ring band indicate a general increase of tilt angle on both silver substrates in the order L 3 < L 4 < L 5 < L 6 . The altered enhancement of the bands due to the vibrations of the NH 2 and OPO fragments, a finding observed on both silver substrates, strongly suggests that the groups interact with different strength and geometry with these substrates. Copyright © 2009 John Wiley & Sons, Ltd.