The coordination of photosensitizing dyes to zinc oxide nanoparticles (ZnO NPs) has attracted extensive attention as promising candidates for applications in solar cells. Here, we report the synthesis of ZnO NPs functionalized with geometric isomers of ruthenium(II)-polypyridyl complexes and a preliminary study of their photophysical properties by fluorescence spectroscopy. ZnO NPs synthesis was carried out by direct precipitation. IR, UV-Vis spectroscopy, XRD and TG-DTA techniques were used for ZnO NPs characterization. Trans and cis complexes of Ru(II) using 2,2 '-bipyridine and 2,2'-bipyridine-4,4'-dicarboxylic acid as ligands were assembled to ZnO NPs. The presence not only of a band of around 355 nm, but also at 465 nm, in the electronic spectrum indicates the modification of the ZnO surface with the synthesized complexes. The fluorescence behaviour of Ru(II) complexes modified ZnO NPs suggested an electron transfer process through the system. Remarkably, the trans isomer modified system showed better response during the electron transfer. This information could be considered during the design of photoanodes in Dye-Sensitized Solar Cells.