In this study, high specific surface area of anatase TiO2 quantum dots were successfully synthesized through a novel one-step microwave-hydrothermal method in rapid synthesis time (20 min) without further heat treatment. XRD analysis and HR-TEM images showed that the as-prepared TiO2 quantum dots of ~2 nm size have high crystallinity with anatase phase. Optical properties showed that the energy band-gap (Eg) of as-prepared TiO2 quantum dots was 3.60 eV, which is higher than the standard TiO2 bandgap, which might be due to the quantum size effect. Raman studies showed shifting and broadening of the peaks of TiO2 quantum dots due to the reducing of the crystallite size. The obtained BET specific surface area (381 m2/g) of TiO2 quantum dots is greater compared to the surface area (181 m2/g) of commercial TiO2 nanoparticles. The photocatalytic activities of TiO2 quantum dots were conducted by the inactivation of E. coli under ultraviolet light irradiation and compared with commercially available anatase TiO2 nanoparticles. The photocatalytic inactivation ability of E. coli was estimated to be 91% at 60 μg/ml for TiO2 quantum dots, which is superior to the commercial TiO2 nanoparticles. Hence, the present study provides new insight into the rapid synthesis of TiO2 quantum dots without any annealing treatment to increase the absorbance of ultraviolet light for superior photocatalytic inactivation ability of E. coli.