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Highlights: [•] Ag-ZnO core-shell structure was obtained via a simple one-step solvothermal process. [•] The approach was simple, mild, low cost, reproducible and easy-to-handle. [•] The obvious enhancement of UV luminescent has been observed. [•] Effects of the calcining temperature to luminescence were investigated in detail. [Copyright &y& Elsevier]

Abstract: Well-oriented ZnO nanorod arrays are successfully fabricated on different substrates. They are formed on different substrates at low temperature via a hydrothermal method, without adding any catalysts or templates. This approach is convenient and inexpensive. The morphologies of ZnO crystals could be controlled and transformed to other morphologies successfully by using different substrates. The effects of the substrates on the ZnO nanorod arrays have been systematically studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterizations of XRD and scanning electron microscopy (SEM) reveal that these products are pure single-crystal and the structure is uniform. The photoluminescence property has been detected by photoluminescence (PL) spectrum and Raman spectrum. Photoluminescence measurements show that each spectrum consists of the ultraviolet (UV) band and a relative broad visible light emission peak. But substrates play roles in the intensity of ultraviolet and visible light emission peak. The green emission in Raman measurement may be related to the surface states. [Copyright &y& Elsevier]

ZnSe(en) 0.5 (en = ethylenediamine) nanosheets were successfully synthesized via a facile solvothermal method using en-water mixture as solvent. When ZnSe(en) 0.5 composite were calcined at 300 °C in air atmosphere, ZnSe(en) 0.5 nanosheets first converted to ZnSe nanosheets. When the calcination temperature was increased to 400 °C, ZnSe nanosheets completely converted to porous ZnO nanosheets. The possible conversion mechanism was proposed based on X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis of the as-prepared samples. ZnSe and porous ZnO nanosheets had the same hexagonal wurtzite crystal structure and maintained the shape and size of ZnSe(en) 0.5 nanosheets. The optical and photocatalytic properties of ZnSe(en) 0.5 , ZnSe and ZnO nanosheets were compared. The experiment of rhodamine B (RhB) photodegradation revealed that ZnSe exhibited the highest photocatalytic activity compared to other samples under ultraviolet (UV) light irradiation. [ABSTRACT FROM AUTHOR]

ZnO nanopowders with different morphologies were successfully synthesized via hydrothermal method. By using different surfactants and controlling the concentration of surfactant in the reaction mixture, ZnO nanoparticles and nanoplates were obtained at 160 °C. The analysis of photoluminescence spectra shows that there exist more oxygen vacancies in the samples with small particle size and rough surface. The as prepared samples are used as photocatalysts for the rhodamine B (RhB) photodegradation, and the results show that ZnO with small particle size is more active for the photocatalytic process. This is attributed to the fact that the smaller particles have larger BET surface area and contain more surface oxygen vacancies, which are considered as stimulative for catalyzing the RhB reaction. The results suggest a positive relationship among particle size, oxygen vacancies and photocatalytic activity for RhB. [ABSTRACT FROM AUTHOR]

The ZnO nanorods/ZnSe nanosheets heterostructure had been successfully fabricated by the spin coating method. The evolution of the structural, optical and photocatalytic properties of the samples with different spin coating times was comprehensively investigated. The X-ray diffraction (XRD) patterns showed that the relative intensities of ZnSe peaks increased gradually with the increase of spin coating times, but the ZnO peaks were relatively suppressed, which had a good agreement with the results of Raman spectra. The scanning electron microscope (SEM) and transmission electron micrograph (TEM) images further confirmed that the ZnSe nanosheets (NSs) had been successfully assembled on the top surfaces of the ZnO nanorods (NRs) and in the upper parts of the gaps between the rods. At room temperature, the ZnO/ZnSe heterostructures exhibited a relatively suppressed UV emission together with a dramatically enhanced deep-level emission. In addition, the heterostructures exhibited remarkable photocatalytic activities. The type-II staggered band alignment and defects formed at the ZnO/ZnSe interfaces should be the key factors for improved photocatalytic performance, and the probable photocatalytic mechanism was discussed in detail. [ABSTRACT FROM AUTHOR]

ZnO nanocages and other nanostructures have been synthesized via a simple one-pot hydrothermal method with different reaction times. It is worth mentioning that this is a completely green method which does not require any other chemicals except that Zn foil served as Zn source in the experiment. X-ray diffraction (XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and UV–Vis diffuse reflection spectra were used to characterize the crystallinity, morphology and optical property of ZnO structures. Growth mechanisms of ZnO were proposed based on these results. Furthermore, ZnO films with different morphologies and crystal growth habits exhibited different activities to rhodamine B degradation. The influence of the reaction time on the morphology of ZnO films and the effect of the morphologies on the photocatalytic activity are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Large-scale arrayed ZnO nanocrystals with two different expose surfaces, including ZnO hexagonal nanoplatforms with the major expose plane of (0001) and hamburger-like samples with the nonpolar planes of {} mainly exposed, were successfully fabricated by a simple hydrothermal method. Mechanisms for compare the photocatalytic activity of two typical ZnO nanostructures were systematic explained as the key point in the paper. Compared with the hamburger-like ZnO nanostructures, the ZnO with hexagonal platform-like morphology exhibited improved ability on the photocatalytic degradation of Rhodamine B (RhB) in aqueous solution under UV radiation. The relative higher photocatalytic activity of the ZnO hexagonal nanoplatforms was attributed to the exposed polar surfaces and the content of oxygen vacancy on the nanostructures surface. The Zn-terminated (0001) polar face and the surface defects are facile to adsorb O2− and OH− ions, resulting in a greater production rate of O2 − and OH −, hence promoting the photocatalysis reaction. [Copyright &y& Elsevier]

Abstract: Eu-doped ZnO nanosheets with irregular porous microstructure were successfully prepared by a simple hydrothermal method. The microstructures, morphologies and optical properties of the as-prepared nanosheets were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and Raman spectroscopy. XRD and XPS results indicated that trivalent europium ions were successfully doped into the crystal lattice of ZnO matrix. Nanosheets with irregular porous can be seen from the TEM images. PL spectroscopy indicated that the peaks located at 580, 587 and 614nm were attributed to the 4f–4f intrashell transitions of 5D0→7F0, 5D0→7F1 and 5D0→7F2 of Eu3+ ions,respectively, and the intensity ratio of 5D0→7F2 to 5D0→7F1 indicated that Eu3+ ions were incorporated into wurtzite ZnO host by substitution on the Zn sublattice and located at a low-symmetry site (C3v) without inversion center. [Copyright &y& Elsevier]

Abstract: Mn-doped ZnO nanorods were synthesized from aqueous solutions of zinc nitrate hexahydrate, manganese nitrate and methenamine by the chemical solution deposition method (CBD). Their microstructures, morphologies and optical properties were studied in detail. X-ray diffraction (XRD) results illustrated that all the diffraction peaks can be indexed to ZnO with the hexagonal wurtzite structure. Scanning electron microscope (SEM) results showed that the average diameter of Mn-doped ZnO nanorods was larger than that of the undoped one. Photoluminescence (PL) spectra indicated that manganese doping suppressed the emission intensity and caused the blue shift of UV emission position compared with the undoped ZnO nanorods. In the Raman spectrum of Mn-doped ZnO nanorods, an additional mode at about 525cm−1 appeared which was significantly enhanced and broadened with the increase of Mn doping concentration. [Copyright &y& Elsevier]