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Various contents of Ag nanoparticles were successfully introduced into the N-doped TiO 2 photocatalysts via a hydrothermal procedure in the silver-ammonia solutions with different Ag concentrations. Effects of Ag loading on the structure and properties of N-doped TiO 2 photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, fluorescence spectroscopy (FL), UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and N 2 physical adsorption analysis. The relationship between the stability of N dopants in TiO 2 lattice and the Ag loading content was investigated for the first time. The results confirm that Ag nanoparticles loading on TiO 2 surfaces significantly restrain the escape of the N dopants from the oxide during the hydrothermal process, and the escape rate of N dopants decreased gradually with the increase of Ag loading amount. The dependence of photocatalytic activity on Ag content was also investigated through degradation of rhodamine B (RhB) under visible light irradiation. It was found that the photocatalytic activity increases gradually with increasing Ag content first, and then decreases after exceeding the optimal Ag content. Therefore, the photocatalytic activity of Ag/N co-modified TiO 2 photocatalysts can be adjusted by the Ag content.

High purity BaTiO3 nanopowders were pressed into pellets and annealed between 100 and 1200 °C. The crystal quality and grain size of the BaTiO3 nanocrystals were characterized by X-ray diffraction measurements. Annealing induces an increase in the grain size from 44 to 82 nm with temperature increasing up to 1200 °C. XRD and Raman spectroscopy studies confirm that all the samples were single phase with a tetragonal structure after annealing at different temperatures. Positron annihilation measurements reveal large number of vacancy defects in the grain boundary region. These interfacial defects remain stable after annealing at temperatures below 400 ° C and begin to disappear rapidly above 700 °C. After annealing at 1200 °C, most of the interfacial defects have been removed. Hysteresis loops are observed for the 100 ° C annealed samples, which indicate ferromagnetism in BaTiO3 nanocrystals. The ferromagnetism becomes a little weaker after annealing at 700 °C, and it disappears after 1200 ° C annealing. This change of ferromagnetism coincides with the defect recovery process after annealing, suggesting that ferromagnetism might originate from the interfacial defects.

Fe ions were implanted into ZnO single crystals with multiple energies between 50 and 380 keV up to a total fluence of 12.5 × 1 0 17 cm−2. The crystal quality of Fe+ implanted ZnO was investigated by X-ray diffraction 2 θ scans and ω -rocking curve measurements. The appearance of Fe related diffraction peaks after 700 ° C annealing of the implanted sample indicates possibly formation of Fe nanoparticles. Superconducting quantum interference device measurements revealed ferromagnetic behavior below 250 K for both the as-implanted and post-annealed ZnO. Photoluminescence and Raman scattering as well as X-ray rocking curve measurements all indicate introduction of structural defects after Fe implantation. Some of the defects act as nonradiative recombination centers, and suppress the visible and ultraviolet (UV) emission in ZnO. These defects also break the Raman selection rule, and lead to the activation of some silent phonon modes. Annealing of the implanted sample at 700 ° C causes partial recovery of the defects, however, the X-ray diffraction results of the anneal ZnO show even an improvement of the crystal quality compared with the un-implanted one. This could be attributed to the recovery of the grown-in defects in ZnO.