Coadsorbed state of uracil, water and sulfate species on the gold electrode surface

Coadsorption of water and sulfate species with uracil was found on the gold electrode using attenuated total reflection–infrared spectroscopy. The adsorbed sulfate species vary with the pH in the electrolyte solution. The peak frequencies of the S–O stretching mode from the sulfate adspecies do not depend on the electrode potential, in contrast to the results in uracil-free H2SO4 or Na2SO4 solutions. The coadsorption of the water and sulfate species is intrinsically suppressed by a hydrophobic methyl group added to the carbon atom in the pyrimidine ring. Thus, we have detected the water and sulfate species located outside the uracil monolayer.