A sol-gel chemistry approach was used to fabricate nanoparticles of TiO2 in its anatase form. The particle size is shown to be sensitive to the use of HClO4 or HNO3 as acid catalyst. The gold-capped TiO2 nanocomposites were processed by the reduction of gold on the surface of the TiO2 nanoparticles via a chemical reduction or a photoreduction method. Different percentages of vanadium-doped TiO2 nanoparticles, which extended the TiO2 absorption wavelength from the ultraviolet to the visible region, were successfully prepared. The synthesized nanocomposites have a size of about 12-18 nm and an anatase phase as characterized by XRD, TEM, AFM, and UV-vis spectroscopy. The TiO2 nanocomposite coatings have been applied on glass slide substrates. The antibacterial activity of TiO2 nanocomposites was investigated qualitatively and quantitatively. Two types of bacteria, Escherichia coli (DH 5α) and Bacillus megaterium (QM B1551), were used during the experiments. Good inhibition results were observed and demonstrated visually. The quantitative examination of bacterial activity for E. coli was estimated by the survival ratio as calculated from the number of viable cells, which form colonies on the nutrient agar plates. The antimicrobial efficiency and inhibition mechanisms are illustrated and discussed.