Search

Single phase nanocrystalline biocompatible A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4.2H2O powders in open air at room temperature within 2 h of milling. The A-type carbonation in HAp is confirmed by FTIR analysis. Structural and microstructure parameters of as-milled powders are obtained from both Rietveld's powder structure refinement analysis and transmission electron microscopy. Size and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Mechanical alloying causes amorphization of a part of crystalline A-cHAp which is analogous to native bone mineral. Some primary bond lengths of as-milled samples are critically measured. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of biological apatite. [ABSTRACT FROM AUTHOR]

The photocatalytic properties of SnO 2 nanocrystals are tuned by varying their morphology and microstructure. SnO 2 nanoparticles and nanowedges have been synthesized using hydrothermal methods, while microwave irradiation techniques have given nanospheres. Detailed structural and chemical characterization of these different morphologies has been accomplished. The influence of SnO 2 morphology on photocatalytic activity has been examined by monitoring the degradation of aqueous methylene blue dye. Results demonstrate that changing the morphology of the SnO 2 modulates both surface area and levels of surface defects and that these alterations are reflected in the photocatalytic properties of the materials. The degradation of methylene blue dye (98%) in the presence of SnO 2 nanoparticles under simulated solar irradiation is superior to previously reported photocatalyst performance and is comparable to that of standard TiO 2 (Degussa P-25). The SnO 2 nanoparticles perform better than both the nanowedges and nanospheres and this is attributed to the number of surface defects available to the high surface area material. They also reveal outstanding recyclability and stability. SnO 2 nanoparticles, nanowedges and nanospheres have been synthesized and the influence of morphology on the photocatalytic degradation of methylene blue investigated. Structure elucidation explains how the change of morphology modulates both surface area and levels of surface defects and how these alterations are reflected in the photocatalytic properties. Good catalyst recyclability is demonstrated. Image 1 • We report a facile approach to SnO 2 nanoparticles, nanowedges and nanospheres. • Our new route to SnO 2 nanostructures is environmentally benign and cost-effective. • A detailed understanding of structure, morphology and stability is developed. • Nanoparticulate SnO 2 show brilliant activity in the degradation of methylene blue. • Correlation of the oxygen vacancies and surface defects with photocatalyst properties. [ABSTRACT FROM AUTHOR]