Effects of incorporated vanadium and its chemical states on morphology and mesostructure of mesoporous bioactive glass particles

Abstract

The incorporation of ions into mesoporous bioactive glass (MBG) may affect its mesostructure and properties, but the mechanism remains unclear. This study focuses on the effects of the contents and the chemical states of the incorporated vanadium on the morphology and mesostructure of MBG. Firstly, the vanadium incorporated MBG (MBG-V) particles with different vanadium contents were prepared via hydrothermal synthesis method utilizing a triblock copolymer (P123) as the structure-directing agent. The vanadium existence was characterized by IR spectroscopy, UV–vis diffuse reflectance spectra, UV Raman spectroscopy, and 51V, 29Si and 31P NMR spectra. It was revealed that most of vanadium species existed in the form of the amorphous calcium vanadate clusters and located at pore wall, while few vanadium species were incorporated in the silica network in an isolated tetrahedral V5+coordination and some polymeric V–O–V vanadium species primarily existed in the surface of the MBG at a higher vanadium loading. With the increase of vanadium contents, the specific surface area, wall thickness, mesopore size, total pore volume, total micropore volume and mesoporous ordered degree decreased, which was partly due to the deposition of three different forms of vanadium species at the inner pore walls and/or external surface areas. Nevertheless, more primary reasons were attributed to the effect of vanadate ions on the initial P123 micellization and the cooperative assembled interaction between P123 micellization and silicon species. In addition, the incorporation of vanadate led to smaller macroscopic particles size of individual particles but a larger primary particles size of P123 micelles/silicon polymer aggregates during preparation process. Overall, our results have preliminarily revealed the influence mechanism of the incorporation of vanadium elements on the morphology and mesostructure of MBG-V, which would be of great significance to regulate the vanadium dissolution behavior and biological properties of vanadium incorporated bone repair materials.