Donor-acceptor graphene-based hybrid materials for managing photoinduced electrontransfer reactions

Graphene research and in particular the topic of chemical functionalization has been exploded in the last decade. The main aim is to induce solubility and thereby enhance processability of the material, which is otherwise insoluble and inapplicable for technological applications when stacked in the form of graphite. In this frame, initially, graphite was oxidized under harsh conditions to yield exfoliated graphene oxide sheets, soluble in aqueous media and amenable to chemical modifications due to the presence of carboxylic acid groups at the edges of the lattice. Some donor-acceptor hybrid materials with photo- and/or electro-active components were prepared and characterized, while their charge-transfer properties were evaluated. However, it was obvious that the highly defected framework of graphene oxide cannot be really utilized in applications that are governed by charge-transfer processes, for example in solar cells. The alternative route for solubilizing and modifying graphene by exfoliating graphite is the current method of choice for the realization of novel hybrid materials and further boost their direct applicability in artificial photosynthesis and the construction of photovoltaic devices. In this review article, the routes for obtaining donor-acceptor graphene-based hybrid materials for managing charge-transfer phenomena, mainly, but not exclusively, with porphyrins and phthalocyanines are presented. Earlier examples and studies performed on graphene oxide modified with organic electron donors are also given