Titanium dioxides (Ti02) have been widely studied, due to its interesting general properties in a wide range of fields including catalysis, photocatalysis, and antibacterial agents and in civil as nano-paint (self-cleaning) that affect the quality of life. Therefore, TiO2 and doped with noble metal are good candidates in the performance these applications. The fascinating physical and chemical features of TiO2 depend on the crystal phase, size and shape of particles. For example, varying phases of crystalline TiO2 have different band gaps that ruble TiO2 of 3.0 eV and anatase TiO2 of 3.2 eV, determine the photocatalytic performance of Ti02. This chapter explains some applications and theoretical concepts of nanostructure of TiO2 nanoparticles. Also, it demonstrates electrical, optical and morphological properties which make TiO2 preferable for environmental applications. (C) 2019 The Authors. Published by Elsevier Ltd.