In the present study, Fe3O4/ZnO core/shell nanocrystals (NCs) are synthesized via seed-meditated growth approach in nonhydrolytic condition. The controlling process of thermal pyrolysis of zinc acetate (ZnAc) renders a condition to overgrow ZnO layer on the surface of Fe3O4 NCs (seeds). The transmission electron microscope (TEM) micrograph shows that Fe3O4/ZnO NCs are spherical in shape, highly monodispersed, and exhibiting responding shell thickness by varying the mole ratio of seed to shell precursor. The X-ray powder diffraction patterns (XRD) for Fe3O4/ZnO NCs reveal the coexistence of both Fe3O4 and ZnO crystal structures, which the patterns can be well indexed with the standard powder diffraction patterns of both materials. The NCs exhibit superparamagnetism corresponding to an external magnet field provided by vibrating sample magnetometer (VSM) and show red-shift phenomenon under UV excitation at room temperature. The NCs are magnetically separable upon application of 0.6 T magnet, which shows that high potentiality of the NCs to be used as regenerable catalyst material.

We report several significant photodecomposition rates of methylene blue (MB) obtained before and after the refluxing process of own-synthesized two-dimensional (2D) zinc oxide (ZnO) nanopellets. Each photodecomposition rate of MB was found highly dependent on the weight of photocatalyst. The existing photodecomposition rate has been successfully improved to a factor of 22.0 times through refluxing process in excessive pyridine where the surface capping ligand (oleic acid) is removed from the 2D ZnO nanopellets. On the other hand, the refluxed photocatalyst (0.04 g) in this study was found to exhibit excellent recyclability up to three cycles. Furthermore, X-ray powder diffraction spectrums for the refluxed photocatatalyst, respectively, before and after three cycles of photocatalytic reactions, has generated the same patterns showing that the photocatalyst is stable and feasible to be used as an efficient photocatalyst material. Hence, these 2D ZnO nanopellets would provide a new alternative route as a highly efficient photocatalyst for wastewater treatment.

In this work we have tried to prepare Ni and Ag doped ZnO nanopowders using the sol gel technique. The influence of Ni and Ag (1, 3 and 5 mol.%) on the crystalline structure and optical properties of ZnO was investigated. The samples were characterized by XRD, FTIR and UV–visible spectrophotometer. XRD patterns confirmed the wurtzite formation of doped and undoped ZnO nanopowders. The average crystallite sizes of the prepared samples found from XRD were 19 nm for undoped ZnO, from 17 to 22 nm for Ni-ZnO and from 19 to 26 nm for Ag-ZnO. The average crystallite size of Ag-ZnO increased with increasing Ag contents. Different optical properties of Ni-ZnO and Ag-ZnO nanopowders were observed for different Ni and Ag content. The band gaps of Ni-ZnO and Ag-ZnO nanopowders were lower than that of the undoped ZnO (3.1 eV). The band gaps of Ag-ZnO were lower than that of Ni-ZnO. The optical properties of ZnO were enhanced by Ni (mol.%) in the UV region and by Ag (3 and 5 mol.%) in the visible region.

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