| Summary: | This paper studies the influence of B<sub>2</sub>O<sub>3</sub> on the structure, properties and antibacterial abilities of sol-gel-derived TiO<sub>2</sub>/TeO<sub>2</sub>/B<sub>2</sub>O<sub>3</sub> powders. Titanium(IV) butoxide, telluric(VI) acid and boric acid were used as precursors. Differences were observed in the degree of decomposition of Ti butoxide in the presence of H<sub>3</sub>BO<sub>3</sub> and H<sub>6</sub>TeO<sub>6</sub> acids. The phase transformations of the obtained gels in the temperature range of 200–700 °C were investigated by XRD. Composite materials containing an amorphous phase and different crystalline phases (metallic Te, α-TeO<sub>2</sub>, anatase, rutile and TiTe<sub>3</sub>O<sub>8</sub>) were prepared. Heating at 400 °C indicated a crystalline-to-amorphous-phase ratio of approximately 3:1. The scanning electron microscopy (SEM) analysis showed the preparation of plate-like TiO<sub>2</sub> nanoparticles. The IR results showed that the short-range order of the amorphous phases that are part of the composite materials consists of TiO<sub>6</sub>, BO<sub>3</sub>, BO<sub>4</sub> and TeO<sub>4</sub> structural units. Free B<sub>2</sub>O<sub>3</sub> was not detected in the investigated compositions which could be related to the better connectivity between the building units as compared to binary TiO<sub>2</sub>/B<sub>2</sub>O<sub>3</sub> compositions. The UV-Vis spectra of the investigated gels exhibited a red shift of the cut-off due to the presence of boron and tellurium units. The binary sample achieved the maximum photodegradation efficiency (94%) toward Malachite green dye under UV irradiation, whereas the ternary sample photoactivity was very low. The compositions exhibited promising antibacterial activity against <i>E. coli</i> NBIMCC K12 407.
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