## 4 Summary and Conclusions  
This review summarizes the present state of knowledge about the structural and application issues of the presence of graphene as an important part of composites with the semiconducting metal oxides in their promising forms, such as faceted particles, various morphological particulate systems and photonic crystals. The incorporation of graphene into mentioned composites is responsible for the introduction of unique properties such as improvement of charge carriers transfer, including exceptional enhancement of electron-hole separation, and also the extension of light absorption properties towards visible region of solar spectrum. Furthermore, the improvement of adsorption capacity for reagents participating in the photocatalytic reactions, resulting from the presence of graphene structures, is also important for an increase in the overall photocatalytic performance. The enhancement of photocatalytic properties originates also from the synergistic effects between the presence of specified morphological form of novel photocatalysts, such as faceted particles, nanotubes/nanowires, opal/inverse opal (slow photon effect) and graphene, or the simultaneous presence of semiconductor modifier or semiconductors' heterojunction system combined with graphene. Moreover, the coupling of G/GO/rGO with ferromagnet particles, such as Fe, Co, Zn, Bi etc. ferrites oxides, does not only increase the photocatalytic activity due to charge carriers separation and more efficient light harvesting, but also allows the recycling and reusing of the photocatalysts. Undemanding separation in external magnetic field fits perfectly into the green chemistry trend due to limitation of post-process photocatalysts' waste and energy costs. Despite the fact that the number of studies on graphene-based photocatalysts is constantly growing, some details describing the mechanism of their exceptional photocatalytic activities are not still entirely clear. Therefore, more research on this topic is needed to clarify this issue, and to enable the design of more efficient, stable and reusable photocatalytic graphene-based materials with a wide application potential, especially in the field of environmental aspects. For application purposes, the antimicrobial activity of graphene and its derivatives are very attractive as they might be used in fight against viruses, bacteria (including antibiotic  
Figure 17: Fe\({}_{3}\)O\({}_{4}\)/G nanocomposites saturation magnetization values presented as hysteresis loops. Reprinted with permission from [172]. Copyright (2016) Creative Commons Attribution. resistant strains), yeast or filamentous fungi. However, the mechanism has not been clearly understood yet, and there are some concerns about the cytotoxicity against higher animals and human cells. For that reason, the primary objective of follow-up study should be the research conducted in parallel on advance scientific understanding on the mechanisms of action at the biochemical or molecular level. A complete understanding of that issue might create great opportunities to develop the smart bandages or wound dressing against particular pathogens. Moreover, graphene-based materials provide a potentially promising tool for real-time diagnostics of the pathogen population or cancer cells in each patient that enables the development of new target therapies. Other possible applications are engineered biomaterials with high biocompatibility and long-life medical devices, such as body implants (teeth and bones). Writing--original draft preparation, M.J., M.E.-K., Z.W., Z.B., T.R.M., T.M.K., K.W., A.M.-S. and E.K. ; Writing--review and editing, M.J., M.E.-K., Z.W., Z.B., T.R.M., T.M.K., K.W., A.M.-S. and E.K. All authors have read and agreed to the published version of the manuscript. This research was financially supported by National Natural Science Foundation of China (NSFC; contract No.