This study investigates the antibacterial efficacy of TiO₂ and TiO₂/Cu nanoparticles synthesized via the sol–gel method. The materials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. SEM and TEM revealed spherical morphology, while EDS and XPS confirmed Cu incorporation into TiO₂. XRD confirmed the tetragonal anatase phase of TiO₂/Cu, and FTIR identified functional groups linked to doped TiO₂. TGA showed lower thermal stability for TiO₂/Cu compared to pure TiO₂. The nanoparticles demonstrated notable antibacterial activity against Bacillus subtilis and Escherichia coli, with 90% and 80% inhibition rates, respectively. The addition of Cu did not significantly affect antibacterial activity due to its low weight content. The study highlights the potential of TiO₂ and TiO₂/Cu nanoparticles as effective antibacterial agents for water treatment, particularly under dark conditions without light sources. The results indicate that these nanoparticles can inhibit bacterial growth efficiently, making them promising candidates for environmental and medical applications.This study investigates the antibacterial efficacy of TiO₂ and TiO₂/Cu nanoparticles synthesized via the sol–gel method. The materials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. SEM and TEM revealed spherical morphology, while EDS and XPS confirmed Cu incorporation into TiO₂. XRD confirmed the tetragonal anatase phase of TiO₂/Cu, and FTIR identified functional groups linked to doped TiO₂. TGA showed lower thermal stability for TiO₂/Cu compared to pure TiO₂. The nanoparticles demonstrated notable antibacterial activity against Bacillus subtilis and Escherichia coli, with 90% and 80% inhibition rates, respectively. The addition of Cu did not significantly affect antibacterial activity due to its low weight content. The study highlights the potential of TiO₂ and TiO₂/Cu nanoparticles as effective antibacterial agents for water treatment, particularly under dark conditions without light sources. The results indicate that these nanoparticles can inhibit bacterial growth efficiently, making them promising candidates for environmental and medical applications.