The presented thesis is focusing on the development of new homogenous and heterogeneous photocatalysts. Different titanium dioxides were selected as photocatalytically active and heterogeneous species and chelate complexes were chosen as homogenous catalysts. Combined with graphene-modified nanomaterials, new systems for the light induced photocatalysis were developed.The first section of the work addresses the production and thorough spectroscopic characterization of different graphene/TiO2 composites. In order to study the photocatalytic activity, all composites were irradiated with different light sources in selected reactions. As reactions, the decomposition of methyl orange and the reduction of benzaldehyde were chosen. The subsequent analysis showed that the method of production of the composites exerts a considerable influence on the photocatalytic activity. At the same time, it was shown that the combination of graphene-based nanomaterials increased the selectivity regarding the desired reaction product.The second section of the work initially focused on the synthesis of the complexes. Different terpyridines were catalyzed as ligands - these were subsequently complexed with different metals via coordinative bonds. The terpyridines were functionalized covalently and over --stacking after complete characterization with graphene oxide.Ultimately, a new and highly reactive photocatalytic system was developed via a peptide linkage between graphene oxide and a 4' amino phenyl group of [Ru(terpy(C6H4NH2))2]. The new catalyst possesses under very mild reaction condition in the presence of light with a wave length of 490-495 nm, a very high reactivity. The use of palladium catalyzed C-C-coupling reactions such as Heck, Sonogashira, Suzuki and Stille leads to yields of up to 100 % at room temperature.