**1. Introduction**

Nanotechnology encompasses biology, chemistry, materials science, medicine and physics. Today, With the advent of nanoscience and titanium dioxide nanostructured materials nanotechnology, nanostructured materials are an important research area due to their various unique properties. Among all transition metal oxides, TiO2 nanostructures are the most attractive materials in modern science and technology [1]. TiO2 is used commercially in donuts, cosmetics, pigments [2], catalysts, sunscreens [3, 4], solar cells [5], water splitting, and more. TiO2 is used in plastics, paints, varnishes, paper, pharmaceuticals, inks, pharmaceuticals, toothpaste, food, and

industry [6, 7]. Nanostructured titanium dioxide (NS-TiO2) is a non-toxic, environmentally friendly, inexpensive, and efficient functional material with a broad range of applications [8–11]. In the past decade, nanostructured TiO2, which can have either a stoichiometric or nonstoichiometric composition, has attracted increasing attention from researchers around the world as a promising highly efficient photocatalyst for the synthesis of organic compounds that meets the principles of green chemistry [12–17]. Today, nano-structured materials are an important area of research due to their several unique characteristic features. Among all the transition metal oxides, TiO2 nanostructures are the best-looking materials in modern science and technology [1]. Nano-TiO2 nanostructures include titanium dioxide nanoparticles (TiO2-NPs) and titanium dioxide nanotubes (TNTs) [18]. With the advent of nanotechnology, NS–TiO2 has found many applications. Nanoscale titanium dioxide (nano-TiO2) has been widely used in environmental protection, cosmetics, antibacterial agents, self– cleaning coatings and cancer treatment, solar cells, photocatalysis, and composite nanofillers [19–21]; due to the fact of its unique size and high specific surface area, nano-TiO2 has more stable physical and chemical properties compared to titanium dioxide. In addition, nano-TiO2 has great application potential in biomedical fields [22, 23] due to the fact of its good antibacterial activity, favorable biocompatibility, and unique photocatalytic activity [24]. Research has shown that nanostructured TiO2 elicits a favorable molecular response and osseointegration, with better bone formation than non-nanostructured materials [25–27]. The unique physicochemical properties of all these forms of NS–TiO2, render this material a promising future in many applications. Several reviews and reports on different aspects of titanium dioxide, including its properties, preparation, modification, and application, have been published. However, despite advances in the development of nanostructured TiO2 systems for bone repair, review articles addressing this topic are still scanty [28].

The purpose of this chapter is to introduce and discuss the properties [29], fabrication, modification, and applications of nanostructured titanium dioxide (NS-TiO2). With the advent of nanotechnology, NS-TiO2 has found many applications.
