Book excerpt: The rapid pace of industrialization and its resulting by-products have affected the environment by producing hazardous wastes, which have been released into the environment. Environmental pollution is a global menace, the magnitude of which is increasing day-by-day due to urbanization, heavy industrialization, and changing lifestyles. Nanostructures as functional building blocks are an ideal candidate for investigation into the dependence of structural, optical, electrical, and magnetic properties of the quantum confinement effect and morphology, which paves the way for novel nanotechnological applications. Both physical and chemical properties of nanostructures are associated with their size, shape, and dimensionality; therefore, morphology controlled synthesis of functional nanostructures gains importance from a scientific and technological perspective.Semiconductor nanomaterials at the nanoscale are gaining significant attention in the areas of energy conversion and storage, sensing, electronics, photonics, and biomedicine. In this book, we discuss semiconducting metal oxide nanostructures like TiO2, ZnO, conducting polymers and nanocomposites for their efficient detection of harmful and toxic chemicals, and nanomaterials for photocatalytic degradation, with an emphasis on the applications of semiconducting materials for renewable energy. The book includes a brief literature survey, properties and the latest research advances in the development of various metal oxide nanostructures, and how nanocomposites and conducting polymer based nanomaterials are efficient for environmental remediation.The application of nanomaterials in the detection and removal of pathogens provides greater sensitivity, lower cost, shorter turn-around times, smaller sample sizes, in-line and real-time detection, as well as higher throughput and portability in environmental remediation. Furthermore, semiconductor photocatalysis for remediation has real potential for combating water pollution. This book provides a comprehensive look at the morphological, structural, crystalline, optical, electrical, and electrochemical properties of semiconducting metal oxides and their applications for environmental cleaning. The preparation and modification of semiconducting nanomaterials could be promising for the reliable and effective detection of harmful chemicals, and renewable energy.