BARIUM FLUORIDE AS AN INTERNAL-REFLECTION ELEMENT FOR IR-ATR SPECTROELECTROCHEMISTRY

The suitability of barium fluoride (BaF2) as an internal reflection clement for ir-ATR spectroelectrochemistry has been examined in this paper. Thin gold or platinum electrodes have been sputtered onto a hemispherical BaF2 ir transparent crystal and the ir spectra of a third (air or water) medium were obtained at a number of different angles of incidence. These results have then been compared with theoretical results calculated via the Fresnel formulae. In general, good agreement between the theoretical and experimental results was obtained. In the case of platinum electrodes, the predicted desirable properties could not be experimentally realized due to the poor adhesion of Pt upon BaF2 in an aqueous environment. It is shown in this work that the BaF2 + Au ATR system is very useful for use in ir spectroelectrochemistry for a number of reasons, in particular due to the possibility of using relatively thick (30 nm) electrode layers and also because of the high reflected light intensity inherent in the system (minimizing noise effects).