Synthesis and Characterization of Luminescent and Antibacterial Europium-Titanate nanotubes

Antibacterial resistance poses a growing threat to public health by reducing the effectiveness of conventional antibiotics. Nanohybrid materials, such as titanate nanotubes (TiNts), represent a promising alternative owing to their low cost, chemical stability, and biocompatibility. In this study, we functionalized TiNts with europium ions (Eu³⁺) to enhance both optical properties and antibacterial activity. The incorporation of Eu³⁺ extended the material's absorption from the ultraviolet into the visible region. Two luminescent hybrids were obtained: (i) TiNts/Eu, prepared by Eu³⁺ adsorption onto nanotubes, synthesized via an alkaline hydrothermal treatment, and (ii) TiNts-[Eu-(tta)₃phen], produced through coordination of Eu³⁺ ions with the TiNts and the organic ligands thenoyltrifluoroacetone (tta) and 1,10-phenanthroline (phen). TiNts/Eu displayed the characteristic red emission of Eu³⁺, arising from the ⁵D₀ → ⁷F _J (J = 0-4) transitions, confirming efficient energy transfer from both the inorganic host and organic ligands. The introduction of tta and phen further improved the material's light absorption in the UV region (200-400 nm). Antibacterial assays revealed inhibition zones of 5 and 11 mm against Staphylococcus aureus and Escherichia coli, respectively, for TiNts/Eu. In contrast, the fully coordinated hybrid TiNts-[Eu-(tta)₃phen] exhibited enhanced antibacterial activity, with inhibition zones of 14 mm. These findings highlight Eu³⁺ functionalized titanate nanohybrids as highly potent antimicrobial agents and versatile luminescent materials for biomedical applications.