TiO2 based photocatalytic materials show effective antibacterial activity typically under a high-power UV light. However, exposure to high-intensity radiation may be detrimental to biological as well as non-biological materials. In this work, we demonstrate a significantly higher antibacterial activity at even low power UV where TiO2 nanoparticles are decorated on silica nanoparticles. The antibacterial activity of the nanoparticles with varying Si : Ti molar compositions were explored against E. coli to obtain effective antibacterial activity with minimal power of UV radiation (8 W). The nanoparticles with a molar ratio of SiO2 : TiO2=2 : 1 (Si2Ti) showed the best antibacterial activity. The minimum inhibitory concentration (MIC) of the Si2Ti catalyst was also determined for varying duration of exposure to 8 W UV radiation. Even at a very low concentration of 5 mg/mL Si2Ti sample, where the active catalyst amount was only 1.66 mg/mL, 100 % killing of E. coli was observed after 90 minutes of UV exposure. For the exposure time of 120 minutes, MIC was reduced even further to 3 mg/mL with an active catalyst amount of 1 mg/mL. The excellent antibacterial activity is attributed to the small crystallite size of TiO2 along with enhanced interaction with bacteria owing to the presence of SiO2. In addition, Si2Ti showed good biocompatibility with more than 87 % cell viability with fibroblast cells for 500 μg/mL of the sample. © 2023 Wiley-VCH GmbH.