In Situ FTIR-ATR Studies of Functionalized Self-Assembled Bilayer Interactions with Metal Ions in Aqueous Solutions.

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The affinity of selected metal ions for palmitic (PAL) and hexadecanesulfonic acid (HDSA) monolayers self-assembled onto an octadecyl silane (ODS) monolayer covalently bound to a Ge internal reflection element has been examd. in situ in aq. electrolytes by attenuated total reflection Fourier transform IR spectroscopy. Marked changes in the bands assocd. with the sym. and asym. stretches of the carboxylate groups induced by metal-ion binding could be discerned for PAL/ODS self-assembled bilayers (SABs) in contact with Cd2+ solns. of pH = 6 even at concns. in the sub-μM range. Subsequent exposure of Cd2+/PAL/ODS SABs to solns. of pH < 4 devoid of Cd2+ led to the removal of Cd2+ from the bilayer leaving behind a better ordered structure, as judged by the shift of the C-H stretching modes toward lower wavenumbers. Spectral evidence for strong metal-terminal sulfonate group interactions was also obtained for HDSA/ODS SABs immersed in solns. contg. Cd2+, Fe3+, and Fe2+, for which the effects on the characteristic sym. and asym. modes of the terminal sulfonate moieties were found to be unique to the nature of each of the metal ions. [on SciFinder(R)]


CAPLUS AN 2002:590912(Journal)