By variation of reaction temperature and time during the hydrothermal synthesis process, TiO2 nanoparticles in anatase, rutile, and mixture of rutile-anatase phases are formed without adding any mineralizer. Differential thermal analysis studies indicate the rutile phase crystallization at a comparatively lower temperature and a low weight loss. The material synthesized by hydrothermal reaction required no post-calcination for the crystallization. Transmission electron microscopy, selected-area diffraction, Brunauer–Emmett–Teller, and x-ray diffreaction studies confirmed the compositions to be anatase and rutile with the particle size ranging from 5 to 25 nm with surface area as high as 260 m2/g for the anatase and 65 m2/g for rutile. The prepared nanoparticles exhibited a blue shift of the absorption edge in the ultraviolet-visible spectrum greater than 10 nm. The particles with average size around 5 nm showed two band edges in the absorption spectra attributed to two different particle sizes. Simple photocatalytic reactions were tried to demonstrate the photochemical activity of the synthesized material. The synthesized nanoparticles exhibited an ultraviolet radiation simultaneous photoreduction of Cr(VI) to Cr(III) and oxidation of formic acid into carbon dioxide and water.