Looking for upconverting biocompatible nanoparticles, we have prepared by the sol–gel method, silica–calcia glass nanopowders doped with different concentration of Tm³⁺ and Yb³⁺ ions (Tm³⁺ from 0.15 mol% up to 0.5 mol% and Yb³⁺ from 1 mol% up to 4 mol%) and characterized their structure, morphology, and optical properties. X-ray diffraction patterns indicated an amorphous phase of the silica-based glass with partial crystallization of samples with a higher content of lanthanides ions. Transmission electron microscopy images showed that the average size of particles decreased with increasing lanthanides content. The upconversion (UC) emission spectra and fluorescence lifetimes were registered under near infrared excitation (980 nm) at room temperature to study the energy transfer between Yb³⁺ and Tm³⁺ at various active ions concentrations. Characteristic emission bands of Tm³⁺ ions in the range of 350 nm to 850 nm were observed. To understand the mechanism of Yb³⁺–Tm³⁺ UC energy transfer in the SiO₂–CaO powders, the kinetics of luminescence decays were studied.

A highly bioactive glass solvBG76 in a binary system 76SiO₂–24CaO (wt%) was prepared following a solvothermal path of the synthesis. The facile synthesis, in terms of the steps and reagents needed, enabled the achievement of a mesoporous material. Many factors such as nano-size (<50 nm), different morphology (non-spherical), use of an unconventional network modifier (calcium hydroxide) during the synthesis, a structure free of crystalline impurities, and textural properties greatly enhanced the kinetic deposition process of hydroxyapatite (HA) when contacting with physiological fluids. The formation of a HA layer on the glass was analyzed by various techniques, namely XRD, IR-ATR, Raman, XPS, EDS analyses, SEM, and HR-TEM imaging. The results obtained were compared to the 45S5 glass tested as a reference biomaterial as well as 70S30C—a glass with similar size and composition to reported solvBG76 but obtained by the conventional sol–gel method. For the first time, superior apatite-mineralization ability in less than 1 h in a physiological-like buffer was achieved. This unique bioactivity is accompanied by biocompatibility and hemocompatibility, which was indicated by a set of various assays in human dermal fibroblasts and MC3T3 mouse osteoblast precursor cells, as well as hemolytic activity determination.