Synthesis and characterization of new SiO2–CaO hollow nanospheres by sol–gel method: Bioactivity of the new system

A new binary system of SiO2–CaO nanospheres has been successfully prepared by sol–gel method in W/O emulsion. Tetraethyl orthosilicate (TEOS) and calcium nitrate tetrahydrate were used as silica and calcia source, respectively, and an ammonia solution was used as catalyst. The choice of the components of the oil and water phase, which stabilize the emulsion, is the key factor contributing to the formation of spherical particles. The surfactants, Span 80 and Tween 20, were used to control the shell thickness, the surface form, the size and form of the pores. The resulting nanospheres with diameter from 110 to 180 nm were obtained after calcination at 600 °C. Calcium bid fair to conduce in narrow size distribution. The in vitro bioactivity study was carried out by soaking in a simulated body fluid (SBF) at 37 °C. Formation of crystalline phase was observed on the surface of nanospheres after soaking in SBF. The properties of all samples were determined by FT-IR, SEM and XRD techniques.