ELECTROMODULATED FOURIER-TRANSFORM INFRARED REFLECTANCE SPECTROSCOPY AT THE GOLD-AQUEOUS TETRAMETHYLTHIOUREA INTERFACE

The interaction of tetramethylthiourea with a polycrystalline gold ele ctrode in alkali and acid media has been studied. The behavior of the adsorbate was investigated by cyclic voltammetry, capacitance, and rot ating disk measurements, and its orientation at the surface was determ ined by in-situ subtractively normalized interfacial Fourier transform infrared spectroscopy. In alkaline solutions tetramethylthiourea exhi bits reversible potential dependent adsorption. Application of the IR metal-surface selection rule clearly shows that the molecule is adsorb ed with the NC(S)N plane parallel to the surface. In acid solutions, t etramethylthiourea (TMTU) is adsorbed at the surface throughout the po tential range investigated and at sufficiently positive potentials, di ssolution of an Au(I)-TMTU complex into the thin layer between the ele ctrode surface and the cell window was observed.