In situ electrochemical static contact angle measurements are employed to probe photoinduced electron transfer processes at electrode surfaces. Photosystems consisting of tris(2,2 0 -bipyridyl)ruthenium(II), (Ru(bpy) 3 2+ ), N,N 0 -dimethyl-4,4 0 -bipyridinium (MV 2+ ), Na 2 EDTA or CdS nanoparticles, MV 2+ , triethanolamine (TEOA) were included in aqueous droplets that were coupled with a ferrocene monolayer-functionalized electrode. Upon the oxidation of the interface (0.5 V vs. Ag

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... ence electrode), and the illumination of the systems, photoinduced electron transfer to the modified electrode proceeds. The electron transfer processes yield photocurrents, and the photoelectrochemical transformations are followed by contact angle measurements. Similarly, a CdS/bipyridinium monolayer is assembled on an Au electrode support. The redox transformations of the bipyridinium units control the hydrophilic/hydrophobic properties of the interface, and are followed by contact angle analyses. Irradiation of the CdS/bipyridinium layer associated with the electrode biased at À0.3 V yields a photocurrent. The changes in the wetting properties of the irradiated interface are investigated by contact angle measurements.