NEW TECHNIQUE FOR ATR/FT-IR SPECTRA MEASUREMENTS OF ADSORBED LAYERS ON A SOLID-PHASE LIQUID BOUNDARY

An ATR/FT-IR technique is described which employs thermoplastic halcogenide glass with a low melting point to bring a solid plate (or a film) into optical contact with the ATR element. The sensitivity of the ATR/FT-IR method with one reflection was one-tenth of a surface monolayer. It was achieved by obtaining spectra at critical angles of incident radiation. Such an approach allows the study of in situ solid/liquid interfaces, where a solid may be relatively opaque over the IR range. The intensity and frequency of the ATR band delta(s)(H2O) are found to depend strongly on wetting properties of the surface. Monitoring relative hydrophobicity/hydrophilicity of the surface in situ simultaneously with analysis of the surface composition is valuable for numerous technologically significant areas, such as flotation, synthesis of coatings with definite wetting properties (water-proof or water-attractive), adhesion, etc. This technique permits the recording of spectra in the kinetic and static regimes and the study of different crystallographic planes. The relative inertness of the halcogenide glass makes it possible to apply a wide range of potentials to the sample (or pH of solutions). Therefore, the technique may be applied in electrochemistry or catalysis. The spectroscopic data obtained by means of this approach for galena/xanthate and pyrite/xanthate systems in berate buffer (pH 9.2) were shown to agree satisfactorily with previous flotation results.