Green chemistry is required for ecofriendly treatment of effluents and pollutants; hence, sustainable development. Application of nanomaterials such as TiO2 and ZnO for photodegradation of organic pollutants is well-known. However, there are some drawbacks in their application, e.g. high agglomeration, low dispersion in medium, and their activity only under UV irradiation. This book covers surface modification of metal oxide doped TiO2 and ZnO nanomaterials synthesized under mild hydrothermal conditions. The materials have been arranged in such a way to be easily understandable for students and researchers. A comprehensive illustrated examples have been provided regarding to characterization and application of the surface modified nanomaterials applicable in the field of environmental engineering and science.