The vibrational spectra of platinum nanoparticles (12 nm) capped with tetradecyltrimethylammonium bromide, C 14 TAB, were investigated by Fourier transform infrared (FTIR) spectroscopy. We have shown that the thermal decay of Pt−C 14 TAB nanoparticles in N 2, H 2, and O 2 atmospheres leads to the release of the hydrocarbon chain of the surfactant and the formation of a strongly bonded layer of ammonium cations on the platinum surface. The platinum atoms accessible to CO chemisorption were not reducible by hydrogen in the temperature range from 30 to 200 °C. A FTIR spectrum of C 14 TAB adsorbed on Pt nanoparticles was dramatically perturbed as compared with pure C 14 TAB. New intense and broad bands centered at 1450 cm −1 and 760 cm −1 are making their appearance in Pt−C 14 TAB. It may be speculated that new bands are the result of coupling between conducting electrons of Pt and molecular vibrations of adsorbed C 14 TAB, and as a consequence, specific vibrational modes of ammonium cation are transformed into electron-vibrational modes.
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Borodko et al. (2009) studied this question.