Alloyed Zn x Ti y O z nanostructures were prepared by a thermal condensation process employing ethanolic mixtures of zinc acetate dihydrate and titanium alkoxide, without additional use of additives. It has been found that the nanocrystal growth takes place at temperatures above 350 °C yielding cubic spinel Zn2TiO4, cubic ZnTiO3, or hexagonal ilmenite ZnTiO3. Their preferential appearance and size tuning between 5 and 80 nm was possible by varying the starting sol condensation conditions, Zn/Ti-ratio and sintering temperature. The electronic transitions in these ternary oxide semiconductor nanocrystals were observed at photon energies between 3.6 and 3.8 eV that reflects the presence of a wider optical gap than that known for the corresponding binary oxides ZnO and TiO2. We also noticed a strong influence of Eu3+ doping on the resulting structural and optical properties. Despite its large ionic size, this lanthanide efficiently intervenes in the evolution process by blocking the nanocrystal growth and the cubic-to-hexagonal transformation in ZnTiO3. Its preferential incorporation into spinel phase is manifested by the activation of a strong red intrashell fluorescence and a significant Stark splitting of the 5FJ states. The comparison of the spectral response and asymmetry ratio values deduced from the experimental Eu3+ luminescence data collected on structurally similar Zn2TiO4 and ZnTiO3 nanophases suggests the hypothesis that cubic ZnTiO3 has a structure of an inverse defect spinel. Our study has not confirmed the existence of the previously reported and often recalled defect spinel Zn2Ti3O8.

Optical fibers have recently attracted a noticeable interest for biomedical applications because they provide a minimally invasive method for in vivo sensing, imaging techniques, deep‐tissue photodynamic therapy or optogenetics. The silica optical fibers are the most commonly used because they offer excellent optical properties, and they are readily available at a reasonable price. The fused silica is a biocompatible material, but it is not bioresorbable so it does not decompose in the body and the fibers must be ex‐planted after in vivo use and their fragments can present a considerable risk to the patient when the fiber breaks. In contrast, optical fibers made of phosphate glasses can bring many benefits because such glasses exhibit good transparency in ultraviolet‐visible and near‐infrared regions, and their solubility in water can be tailored by changing the chemical composition. The bioresorbability and toxicity of phosphate glass–based optical fibers were tested in vivo on male laboratory rats for the first time. The fiber was spliced together with a standard graded‐index multi‐mode fiber pigtail and an optical probe for in vitro pH measurement was prepared by the immobilization of a fluorescent dye on the fiber tip by a sol‐gel method to demonstrate applicability and compatibility of the fiber with common fiber optics.

No abstract