**1. Introduction**

The discovery of photoinduced superhydrophilic behavior of Titanium dioxide (TiO2) so that it is considered as most promising photo-responsive wetting material (Wang et al. in 1997) [1]. TiO2 is a semiconductor, on excitation of titanium with suitable light energy, the photocatalysis process takes place on the surface so that organic dirt molecules adsorbed on the surface and decomposed with the process of photocatalysis. Photocatalysis is followed by the washing of surface with flow of water and finally surface will be clean and sterilized. TiO2 an extensively acceptable applicant for superhydrophilic self-cleaning surfaces and coatings due to its superior optoelectronic properties, photostability, low-cost production, nontoxicity, and environmental friendliness. The structural and surface properties and also intrinsic

electronic characteristics of titanium dioxide are responsible for its photocatalytic efficiency and photo-induced wettability and consequently its self-cleaning property. In recent times, the research has shown the most interest in field of the development and commercialization of self-cleaning coatings and surfaces with the properties of antireflective, antifouling, and antifogging. Self-cleaning coatings and surfaces have potential applications in major sectors such as the medical industry (especially medical aids with anti-microbial surfaces), food industry, optical industry (lenses, camera, and sensors), marine industry (corrosion protection), aircraft industry, construction industry (cement & paint), automobile industry, etc. In this review article, we give a significant evaluation of the superhydrophilic self-cleaning materials and surfaces, environmental applications, and sustainability. In this chapter, we introduce the concept of superhydrophilicity and self-cleaning action of TiO2 as a photocatalyst and later water treatment mechanism of such systems. This review emphasizes the potential applications and practical challenges of self-cleaning surfaces and coatings in real-life situations.
