Wetting in narrow gaps and capillaries: temperature- and surface-pressure-induced wetting transitions: a comment

Evanescent-wave-generated or total-reflection-fluorescence spectroscopy was shown by Fattinger et al. (Ch. Fattinger, F. Honegger, W. Lukosz, Phys. Re v. Lett. 57 (1986) 2536) to offer an elegant route to the study of liquid/s olid wetting phenomena near liquid-liquid critical solution points. Their p ioneering work was confined to a particular kind of mixture exhibiting a lo wer critical solution point. Here we review the principal factors, some not explicitly discussed by Fattinger et al., which determine the fluorescence -temperature profile in such measurements, and we generalize their discussi on inter alia to include the more common case of mixtures exhibiting an upp er critical solution temperature. Additionally, we draw attention to newer methods of characterising the identity of the wetting and wetted phases bas ed on the effect of the changing compositions of these phases on (i) the ab sorption and emission spectra and (ii) the luminescence lifetime of the flu orescent probe molecule which widen the scope of the application of the tec hnique. (C) 1999 Published by Elsevier Science B.V. All rights reserved.