[en] Zr-doped and pure TiO₂ nanoparticles (NPs) were synthesized using a simple inexpensive sol-gel method. X-ray powder diffractometry and Fourier transform infrared spectrometry revealed the presence of anatase-phase TiO₂ NPs. Scanning electron microscopy and transmission electron microscopy revealed that the average nanocrystalline size of approximately 15 nm. The photocatalytic activities of these materials were evaluated using Rhodamine B (Rh B) as an organic contaminant. The photocatalytic activity of pure and Zr-doped TiO₂ NPs (with at% 4, 8, 12 and 16) was measured in terms of the degradation of Rh B under UV light. The antibacterial activities of pure and Zr-doped (with 8 at%) TiO₂ NPs were evaluated against Bacillus subtillis, Escherichia coli, and Pseudomonas aeruginosa. A maximum inhibition zone (19 mm) was observed for pure TiO₂ NPs, against Bacillus subtillis and Pseudomonas aeruginosa, while Zr-doped TiO₂ (8 at%) exhibited a lesser inhibition zone (18 mm) against the same Bacillus subtillis and Pseudomonas aeruginosa (18 mm). However, Zr-doped TiO₂ (8 at%) NPs exhibited a greater inhibition zone against Escherichia coli (17 mm), while the activity of pure TiO₂ NPs against Escherichia coli (15 mm) was retarded. Thus, pure TiO₂ NPs and Zr-doped TiO₂ (8 at%) NPs have competent activities and can be used as antibacterial agents against different bacteria. (paper)