ZnO nanopowders and their excellent solar light/UV photocatalytic activity on degradation of dye in wastewater

Low-cost and scalable preparation,high photocatalytic activity,and convenient recycle of Zn O nanopowders(NPs)would determine their practical application in purifying wastewater.In this contribution,ZnO NPs were scalably synthesized via the simple reaction of Zn powder with H_2O vapor in autoclave.The structural,morphological and optical properties of the samples were systematically characterized by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectra,transmission electron microscopy,Micro-Raman,photoluminescence,and ultraviolet-visible spectroscopy.The as-prepared Zn O NPs are composed of nanoparticles with 100–150 nm in diameter,and have a small Brunauer-Emmett-Teller surface area of 6.85 m^2/g.The formation of Zn O nanoparticles is relative to the peeling of H_2 release.Furthermore,the product has big strain-stress leading to the red-shift in the band gap of product,and shows a strong green emission centered at 515 nm revealing enough atomic defects in Zn O NPs.As a comparison with P25,the obtained dust gray Zn O NPs have a strong absorbance in the region of 200–700 nm,suggesting the wide wave-band utilization in sunlight.Based on the traits above,the Zn O NPs show excellent photocatalytic activity on the degradation of rhodamine B(Rh-B)under solar light irradiation,close to that under UV irradiation.Importantly,the Zn O NPs could be well recycled in water due to the quick sedimentation in themselves in solution.The low-cost and scalable preparation,high photocatalytic activity,and convenient recycle of Zn O NPs endow themselves with promising application in purifying wastewater.

Tuning the Microstructural and Magnetic Properties of ZnO Nanopowders through the Simultaneous Doping of Mn and Ni for Biomedical Applications

Undoped and Mn＋Ni doped ZnO nanopowders were synthesized using a simple soft chemical route by varying the Ni doping level （1, 3, 5 and 7 at.%） and keeping the Mn doping level （10 at.%） constant, X-ray diffraction studies reveal that the incorporated Ni^2＋ ions form a secondary phase of cubic NiO beyond the Ni doping level of 3 at.%, which is also confirmed by Fourier transform infrared spectroscopy. The band gap of the nanopowders increases （from 3.32 to 3.44 eV） up to 3 at.% of Ni doping and decreases with further doping. ZnO：Mn：Ni nanopowders with 3 at.% of Ni concentration exhibit good antibacterial efficiency. The variation in the size of the nanoparticles, as observed from the TEM images and hydroxyl radicals as evidenced from the photoluminescence results, clearly substantiate the discussion on the antibacterial efficiency of the synthesized nanopowders. Magnetic properties of the synthesized nanopowders were studied using a vibrating sample magnetometer, and the results showed that the doping of Mn and Ni largely influences the magnetic properties of ZnO nanopowders.

Enhancing the Antibacterial Efficiency of ZnO Nanopowders Synthesized by Combustion Method Through Ag+Fe Co-doping

（Ag ＋ Fe）-doped ZnO nanopowders have been synthesized using combustion method. Ag doping level was kept as 2 at.%, and Fe doping level was varied from 3 to 6 at,%, and the structural, optical, surface morphological, and antibacterial properties have been investigated. The structural studies show that ZnO/（Ag 4-Fe） nanopowders have hexagonal wurtzite structure with a preferential orientation along the （101） plane. The FE-SEM images indicate that there is a gradual decrease in the grain size with the increase in the doping level of Fe, and the TEM images are correlated well with FE-SEM images. The XPS profile clearly confirms the presence of expected elemental composition. Photolumi- nescence studies reveal the presence of extrinsic defects in the material. Antibacterial activity of Ag- and Fe-doped ZnO nanopowders against Vibrio parahaemolyticus, Vibrio Cholerae, and Staphylococcus aureus bacteria was also investigated.

Synthesis and photoluminescence of Y and Cd co-doped ZnO nanopowder

Y and Cd co-doped ZnO nanopowders were prepared via chemical precipitation method in order to modify the band gap and increase the luminescent intensity. The structures and optical properties of the as-synthesized samples were characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and photoluminescence （PL）. The effects of Y and Cd ions on the optical properties of the samples were studied. Doping of Y into ZnO evidently increases the intensity of UV emission, or co-doping of Y and Cd enhances the UV emission, narrows the band gap of ZnO and hence red shifts the UV emission at the same time. Therefore, Y and Cd co-doped ZnO nanopowders exhibit an intense violet emission in the room temperature PL spectrum, which could be a potential candidate material for optoelectronic applications.

Synthesis of ZnO：Dy Nanopowder and Photoluminescence of Dy^3＋ in ZnO

A type of dysprosium-doped ZnO （ZnO：Dy） nanopowder was synthesized by high temperature calcinations. XRD was used to analyze the structure. Photoluminescence spectra were used to study the optical characteristic. PL of ZnO：Dy shows two different spectra which are broad band resulted from the defect of Dy in ZnO and sharp lines from the 4f→4f transition of isolated Dy^3 ＋ luminescence center. The emission and excitation spectra depend on the excitation wavelength and the concentration of Dy^3＋ . The broad bands with peaks at 600 and 760 nm are attributed to the recombination from an electron of the defect Dy in ZnO to a hole in VB.

Hydrothermal synthesis and physicochemical characterization of CuO/ZnO/Al_2O_3 nanopowder.Part I:Effect of crystallization time

A hydrothermal method was successfully used for synthesis of CuO/ZnO/AI203 （CZA） nanopowder with atomic ratio of 6：3：1. The effect of crystallization time （3, 6, 9, and 12 h） on physicochemical properties of nanopowder was investigated. Nanopowders were characterized using XRD, FESEM, EDX, FTIR, TG, and BET techniques. The XRD patterns confirmed metal oxides formation and their good crystallinity with average crystallite size of 20nm as obtained by the Scherrer equation. Relative crystallinity was shown to increase with increasing crystallization time. In agreement with XRD results, FESEM images also illustrated nanosized particles. EDX mapping indicated homogenous dispersion of elements. BET specific surface area analysis showed acceptable surface area for CZA nanopowder, FTIR spectroscopy confirmed metal oxides formation during hydrothermal and calcination processing. TG results illustrated high thermal stability of the synthesized nanopowders. TG-DTG and FTIR analyses were used to propose a reaction mechanism for nanopowder formation during processing. Physicochemical characterization showed optimal crystallization time to be 6 h.