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Abstract: Nanocrystalline NaNbO3 and NaTaO3 have been synthesized by the reverse micellar technique for the first time. The particle size of NaNbO3 was found to be 18nm while that of NaTaO3 was found to be 40nm (much smaller size than most of the earlier reports on NaTaO3). Rietveld refinement of X-ray diffraction data and Raman spectroscopy confirm that the nanoparticles of NaNbO3 and NaTaO3 have orthorhombically distorted structures with Pmc21 and Pbnm space groups, respectively. The dielectric constant at 25°C of NaNbO3 and NaTaO3 was found to be 209 and 147 at 1kHz, respectively. The antiferroelectric transition in NaNbO3 shifts to lower temperature (325°C) in the nanocrystalline solid. [Copyright &y& Elsevier]

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]