Direct synthesis of UO2 nanoparticles in aqueous solutions of uranyl nitrate containing different concentrations of 2-propanol and acetone has been carried out through photochemical route. The formation of these nanoparticles was found to take place through the reduction reactions of UO2+2 ions with (CH3)2C•OH radicals, which could be generated by two different routes; (i) photoexcitation of acetone followed by H atom abstraction from 2-propanol molecules and (ii) H atom abstraction from 2-propanol molecules by the photoexcited uranyl ions. The growth of UO2 nanoparticles was associated with an induction period, which could be tuned by 2-propanol and acetone contents in the reaction mixture. These nanoparticles were spherical in shape and stable under ambient conditions for several days.