Mesoporous bioactive glasses (MBGs) have become important bone implant materials because of their high specific surface area resulting in high bioactivity. Doping MBGs with Ag removes one of the remaining challenges to their applications, namely their lack of intrinsic antibacterial properties. In present work we demonstrate that Ag-doped MBGs can be prepared in one-step spray pyrolysis (SP) process. The SP preparation method offers the advantages of short processing times and continuous production over the sol-gel method previously used to prepare MBGs. Using scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction we demonstrate that the synthesized MBG particles have amorphous structure with nanocrystalline Ag inclusions. The scanning transmission electron microscopy-X-ray energy dispersive spectrometry of cross-sectional samples shows that the distribution of the Ag dopant nanoparticles within MBGs can be controlled by using the appropriate formulation of the precursors. The distribution of the Ag dopant nanoparticles within the MBG particles was found to affect their surface areas, bioactivities and antibacterial properties. Based on the observations, we propose a mechanism describing MBG particle formation and controlling dopant distribution.

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Strontium titanate (SrTiO3) is a potential photocatalyst of H2 evolution for providing green energy. One of the main strategies for increasing the efficiency of H2 evolution is to increase the surface area of photocatalysts. In this study, spray pyrolysis was used because of its superior flexibility in morphological control. Three typical reactants, nitric acid, acetic acid, and citric acid, were added to Sr and Ti precursors to form various morphological SrTiO3 powders. The SrTiO3 powders were investigated by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, focused ion beam technique, and the Brunauer–Emmett–Teller (BET) method to determine the phase composition, surface morphology, geometry, inner structure, and specific surface area, respectively. Four main morphologies of SrTiO3 particles, namely, porous, concave porous, wrinkled spherical, and hollow porous structures, were obtained. Among these powders, SrTiO3 particles prepared with citric acid had the highest surface area (46.9 m2/g) because of their hollow porous structure. Finally, the formation mechanisms of these four distinct SrTiO3 morphologies are discussed.

In this study, bioactive glass (BG) particles were synthesized directly using spray pyrolysis (SP). Since the bioactivity of glass particles is well correlated with their chemical composition, how to obtain homogenous bioactive glass becomes an important issue. For SP, the main reason for chemical inhomogeneity was considered to be caused by the difference in the precipitation speed of each precursor. So, two Si-containing precursors of BG, namely tetraethyl orthosilicate (TEOS) and silicon acetate (SiA), have been applied to prepare BG particles. The bioglasses were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy to examine their phase composition, and surface structures, inner morphologies and chemical compositions. It was observed that, under the calcination temperature of 700 degrees C, TEOS-derived powder contained Si-rich nanoparticles and Si-deficit submicron particles as inhomogeneity, whereas the SiA-derived powder was homogenous. The reason of inhomogeneity is that TEOS dissolves in "volatile" ethanol more readily than in water via the SP mechanism of "gas-to-particle-conversion" to form Si-rich nanoparticles. The presence of Si-rich nanoparticles causes Si-deficit "wollastonite submicron particles" to form, which impairs the bioactivity. Finally, BG particle formation mechanisms from different precursors have been proposed.