Growth and characterization of the Al-doped and Al–Sn co-doped ZnO nanostructures

In the present work, well-dispersed structures of spherical-like pure ZnO, Al doped ZnO (AZO) and Al, Sn co-doped ZnO (ATZO) nanocrystals were successfully synthesized by using zinc acetate dihydrate as the starting material and also the low temperature hydrothermal process without any additional surfactant or catalytic agent. The ZnO structures were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The XRD results revealed that ZnO powders have a hexagonal crystal structure and the TEM indicated that the nanoparticles self-aggregate. An X-ray photoelectron spectroscopy (XPS) study confirmed the substitution of Zn²⁺ by Sn and Al ions. Optical properties of the ZnO structures were investigated by Raman spectroscopy and room-temperature photoluminescence (PL) spectroscopy. The Raman spectroscopy results demonstrated that the doped ZnO nanoparticles had a higher crystalline quality than that of pure ZnO. Room-temperature PL spectra of these structures showed a strong UV emission peak and a relative weak green emission peak, and the UV peak of the doped ZnO nanoparticles was blue-shifted with respect to that of the undoped ZnO nanoparticles.     

Optical properties of group-I-doped ZnO nanowires

Undoped and group-I elements doped ZnO nanowires were synthesized using a thermal evaporation method. Field emission scanning electron microscopy (FESEM) results showed that, the undoped ZnO nanowires were ultra-long with uniform diameters. On the other hand, the length of the doped ZnO nanowires was in the range of some hundred of nanometers. X-ray diffraction (XRD) patterns clearly indicated hexagonal structures for all of the products. X-ray photoelectron spectroscopy (XPS) studies confirmed the oxidation states of Li, Na, K, in the ZnO lattice. An asymmetric O 1s peak indicated the presence of oxygen in an oxide layer. The effect of doping on the optical band-gap and crystalline quality was also investigated using photoluminescence (PL), UV–vis, and Raman spectrometers. The Raman spectra of the products indicated a strong E₂ (high) peak. The PL spectra exhibited a strong peak in the ultraviolet (UV) region of the electromagnetic spectrum for all of the ZnO nanowires. The UV peak of the doped ZnO nanowires was red-shifted compared to the undoped ZnO nanowires. In addition, the UV–vis spectra of the samples showed similar results compared to the PL results.     

Ultra-rapid microwave-assisted synthesis of gallium doped zinc oxide for enhanced photocurrent generation

Ultra-rapid microwave-assisted hydrothermal synthesis was performed, zinc oxide nanoparticles were fabricated and doped with gallium. Different times (5, 15, and 30 min) and concentrations of doped Ga (1, 3, and 6%) were used to improve their characteristic properties. In addition, the relation between time/dopant was analyzed. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and UV–Vis diffuse reflectance spectroscopy. Photoluminescence (PL) to verify number of defects. SEM analysis showed the formation of nanorods morphology even with a short synthesis time. The X-ray diffractograms and Raman spectra suggest the successful insertion of Ga into the ZnO lattice. The crystallite size obtained by doping was between 36 and 50 nm. The lattice parameters determined by the Rietveld refinement confirmed the formation of a wurtzite hexagonal structure. The band gap range found was 3.12–3.22 eV, which increases the potential of ZnO for optical applications. The presence of defects as result of doping was confirmed by PL. The microstructural changes of the material are enhanced by doping, which causes the photocurrent to increase from 0,002 to 0.012 mA/cm² in doped ZnO. The synthesis time and Ga doping facilitated the production of ZnO nanoparticles with improved properties.     

Studies of thermoelectric transport properties of atomic layer deposited gallium-doped ZnO

The thermoelectric transport properties of atomic layer deposited (ALD) gallium doped zinc oxide (GZO) thin films were investigated to identify their potential as a thermoelectric material. The overall thermoelectric properties, such as the Seebeck coefficient and electrical conductivity, were probed as a function of Ga concentration in ZnO. The doping concentration was tuned by varying the ALD cycle ratio of zinc oxide and gallium oxide. The GZO was deposited at 250 °C and the doping concentration was modified from 1% to 10%. Sufficient thermoelectric properties appeared at a doping concentration of 1%. The crystallinity and electronic state, such as the effective mass, were investigated to determine the enhancement of the thermoelectric properties. The efficient Ga doping of GZO showed a Seebeck coefficient of 60 μV/K and an electrical conductivity of 1808.32 S/cm, with a maximum power factor of 0.66 mW/mK².     

Investigation of ZnFe2O4 spinel ferrite nanocrystalline screen-printed thick films for application in humidity sensing

Zinc ferrite nanocrystalline powder was obtained by solid state synthesis of starting zinc oxide and hematite nanopowders. Field emission scanning electron microscopy and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the formation of nanocrystalline zinc-ferrite powder with a mixed spinel structure with small amounts of remaining zinc oxide and hematite as impurities. Thick film paste was formed and screen printed on test interdigitated PdAg electrodes on alumina substrate. Formation of a porous nanocrystalline structure was confirmed by scanning electron microscopy and Hg porosimetry. Humidity sensing properties of zinc ferrite thick films were investigated by monitoring the change in impedance in the relative humidity interval 30%-90% in the frequency range 42 Hz-1 MHz at room temperature (25°C) and 50°C. At 42 Hz at both analyzed temperatures the impedance reduced ~46 times in the humidity range 30%-90%. The dominant influence of grain boundaries was confirmed by analysis of complex impedance with an equivalent circuit.     

Sm掺杂ZnO QDs的制备及其荧光性能研究

通过研究不同碱/锌、钐/锌物质的量比制备了分散性良好的Sm掺杂氧化锌量子点（ZnO QDs）。通过紫外可见光谱（UV-vis）、X射线衍射（XRD）、场致发射透射电子显微镜（TEM）、能量色散X射线谱（EDS）、X射线光电子能谱（XPS）对样品做了表征。研究结果表明,n（Zn）∶n（OH^-）=1∶1、Sm掺杂量为4%（物质的量分数）时制备的ZnO QDs在383 nm紫外光激发下的荧光发射强度最强。并发现稀土钐离子的掺杂与ZnO QDs的氧空位（OV）形成有关。Sm掺杂后的ZnO QDs的氧空位浓度比未掺杂的高,且ZnO QDs氧空位的浓度越大,其荧光发射强度越强。     

Charge-Transfer Effect of GZO Film on Photochemical Water Splitting of Transparent ZnO@GZO Films by RF Magnetron Sputtering

With the purpose of enhancing the photochemical water splitting performance, GZO film has been used to increase the charge transfer of the ZnO@GZO films. The characterization of ZnO film, GZO film and ZnO@GZO films was carried out by X-ray diffraction (XRD), atomic force microscope, DRUV-vis spectra (DRUV-vis), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and photochemical water splitting. All samples show a related highly c-axis peak (002) from XRD patterns. DRUV-vis results show that the formed GZO film with wide band gap but low resistivity, would not affect the band gap of the ZnO@GZO films. PL results reveal that the decreased recombination of electron and hole, via the increased charge transfer by GZO film. XPS results hint that the obvious change of chemisorbed oxygen species on the surface of ZnO and GZO, and Ga atoms mainly substitute into Zn sites in the ZnO matrix. Compared with that of ZnO film, the ZnO@GZO films even with lower specific surface area, could efficiently enhance the photochemical water splitting performance via the charge-transfer effect of the GZO film.     

Effect of incorporating two-dimensional transition metal Mo and photoelectric element Ga on micro-characteristic of chalcogenide-based ZnS/Se

There is a challenge to increase the application range of chalcogenide materials due to the fixed photoelectric properties and complex preparation process. To solves the problem, bulk ceramics with different doping ratios should be investigated. Here, the influence of the doping ratio of molybdenum MO and Ga oxide on the composition, structure, morphology and luminescence properties of bulk ceramics is studied, the optimal doping ratio in this range is determined by analysis of mass loss and volume shrinkage. The cubic crystal structure is confirmed by X-ray diffraction results. The results showed that molybdenum was successfully doped Mo into the matrix material is revealed by Raman spectroscopy. The X-ray fluorescence is used to study the composition ratio changes of bulk ceramics before and after sintering. The molecular structure model of Mo–ZnSe/ZnS with different concentration is constructed. The X-ray photoelectron spectroscopy shows the spin orbits of Zn 2p and S 2p, as well as the +3 valences in terms of Mo and Ga. The optical performance is enhanced the light-emitting band is enlarged to the near infrared region. All the work suggest that this new compound has an improved micro-structural, optical and electrical properties. This research can provide theoretical and experimental reference for the doping research of chalcogenide materials and new optoelectronic devices.     

均相共沉淀及凝胶燃烧法制备Yb:GGG纳米粉的比较(英文)

用均相沉淀法和凝胶燃烧法分别合成了掺镱钆镓石榴石粉体(Yb3+Gd3Ga5O12,gadolinium gallium garnet doped with ytterbium,Yb:GGG).借助X射线衍射、透射电镜、热分析、红外光谱及荧光光谱等手段对制备粉体的结构、形貌、热分解过程及光谱特性进行对比分析.结果表明:在900℃煅烧8 h后,2种方法均能获得单相立方的Yb:GGG纳米粉体.均相沉淀法及凝胶燃烧法得到的粉体平均粒径分别约为80 nm和47nm.在488nm激发波长下,2种方法获得的Yb:GGG粉体的荧光光谱相似,荧光发射的最强峰位于1 027nm处,是Yb3+的2F7/2→2F5/2谱相导致的荧光发射.     

Sol–gel synthesis of novel cobalt doped zinc tin oxide composite for photocatalytic application

A novel photocatalyst based on cobalt doped zinc tin oxide is proposed. Cobalt doped zinc tin oxide thin films were deposited using a sol–gel deposition method and characterized by scanning electron microscopy (SEM), X-ray diffraction, Raman spectroscopy, photoluminescence emission measurement and UV–vis spectroscopy. It was found that the addition of Co into the zinc tin oxide does influence the structural and optical properties of the thin films and increases the overall photocatalytic degradation of methylene blue.     

MoS2/ZnO纳米复合材料的光学和光催化性能

在溶剂热法制备ZnO纳米粒子的基础上,利用物理剥离和纳米粒子互剪切作用成功制备了MoS₂/ZnO异质结构纳米复合物。以扫描电子显微镜、透射电子显微镜、X射线能量色散光谱、粉末X射线衍射、拉曼光谱仪、紫外-可见漫反射光谱、光致发光谱等对样品进行了结构形貌和性能表征。结果表明,利用物理剥离和互剪切作用能有效地获得MoS₂/ZnO复合物,复合作用使得MoS₂位于378cm^-1(E¹_2g)和400cm^-1(A_1g)处的两个特征拉曼峰显著增强。复合物中MoS₂含量越少,两个特征拉曼峰强度反而越高,且两峰波数间隔相应减小。可归因于MoS₂含量较低时,ZnO纳米粒子对MoS₂的物理剥离效果越显著,同时,MoS₂体现出良好的分散性和较小的厚度。MoS₂含量对MoS₂/ZnO的发光具有明显的调制作用,显著增强了复合物在可见光区域的吸收。随着MoS₂含量增加,其可见光发光强度迅速减小,紫外峰出现明显的蓝移。纯ZnO对苯酚的降解率最高达90%,而MoS₂/ZnO复合物对苯酚的降解率达100%,复合物对苯酚的最终降解率明显高于纯氧化锌。     

An assessment of zinc oxide nanosheets as a selective adsorbent for cadmium

Zinc oxide nanosheet is assessed as a selective adsorbent for the detection and adsorption of cadmium using simple eco-friendly extraction method. Pure zinc oxide nanosheet powders were characterized using field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The zinc oxide nanosheets were applied to different metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III). Zinc oxide nanosheets were found to be selective for cadmium among these metal ions when determined by inductively coupled plasma-optical emission spectrometry. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on zinc oxide nanosheets.     

Low-temperature synthesis of nanosized bismuth ferrite by the soft chemical method

This paper describes research on a simple low-temperature synthesis route to prepare bismuth ferrite nanopowders by the polymeric precursor method using bismuth and iron nitrates. BiFeO₃ (BFO) nanopowders were characterized by means of X-ray diffraction analyses, (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy (Raman), thermogravimnetric analyses (TG-DTA), ultra-violet/vis (UV/Vis) and field emission scanning electron microscopy (FE-SEM). XRD patterns confirmed that a pure perovskite BiFeO₃ structure with a rhombohedral distorted perovskite structure was obtained by heating at 850 °C for 4 hours. Typical FT-IR spectra for BFO powders revealed the formation of a perovskite structure at high temperatures due to a metal–oxygen bond while Raman modes indicated oxygen octahedral tilts induced by structural distortion. A homogeneous size distribution of BFO powders obtained at 850 °C for 4 hours was verified by FE-SEM analyses.     

Application of impregnation combustion method for fabrication of nanostructure CuO/ZnO composite oxide: XRD,FESEM, DRS and FTIR study

Nanostructured CuO/ZnO composite oxide was prepared by a novel impregnation combustion method using copper nitrate and zinc oxide tetrapod. The X-ray diffraction patterns revealed that CuO/ZnO composite oxide was formed. The effects of different impregnation combustion parameters on the properties of composite were studied by field-emission scanning electron microscope (FESEM), powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and UV–vis diffuse reflectance spectrum (DRS). The synthesis of ZnO–CuO nanocomposites through impregnation of a zinc oxide tetrapod with copper nitrate aqueous sodium carbonate solutions is reported. During thermal treatment the samples evolve toward the formation of nanocrystalline ZnO particles (zincite phase) dispersed onto tenorite, CuO annealed at 450 °C. XRD patterns of the precursors calcined at 450 °C showed the formation of the zincite–tenorite phases. Field emission scanning electron microscopy (FESEM) exhibited loosely agglomerated hexagonal particles with uniform morphology having a size around 50 nm.     

Synthesis of zinc oxide and carbon nanotube composites by CVD method: photocatalytic studies

The present work describes the synthesis of multiwall carbon nanotubes (CNT), zinc oxide (ZnO) and their photocatalytic evolutions. Nickel doped fumed SiO₂ used as substrate for the synthesis of CNT by in chemical vapour deposition method. In-situ synthesis of ZnO:CNT composites was achieved in alkaline ethanolic medium with zinc chloride and CNT. The prepared composites were investigated by the Fourier Transform Infrared spectroscopy, confocal Raman spectroscopy, diffuse reflectance UV–visible spectrophotometer (DRS), X-ray diffraction, X-ray Photoelectron Spectroscopy (XPS), Brunaur–Emmett–Teller surface area and field emission scanning/transmission electron microscopy. The composites were employed in the degradation methylene blue and Reactive red-198 under visible light irradiation. The photocatalytic activity was determined by the spectrophotometric technique. The percentage of degradation was more for ZnO:CNT composites and shows higher capacitance, when compared to that of ZnO and CNTs. The recovered and reused catalysts catalytic activity was compared with that of fresh catalyst.     

Time-resolved cathodoluminescence and photoluminescence of nanoscale oxides

The nanostructured oxide materials such as ZnO, ZrO₂, and Y₃Al₅O₁₂ (YAG) are perspective materials for transparent scintillating and/or laser ceramics. The luminescence properties of single crystals, nanopowders and ceramic were compared. Nominally pure and rare-earth doped nanopowders and ceramics have been studied by means of time-resolved luminescence spectroscopy.The fast blue luminescence band was studied in ZnO ceramics sintering from different raw materials.The luminescence centres of ZrO₂:Y were compared in a single crystal, ceramic and nanopowder.It is shown that ceramic sintering parameters have a strong influence on time-resolved luminescence characteristics in cerium-doped YAG.     

Effect of defect states in the optical and magnetic properties of nanocrystalline NiO synthesised in a single step by an aerosol process

Nanocrystalline nickel oxide (NiO) was successfully synthesised as a phase-pure product from an inorganic precursor through a “single-pot”, gas-phase synthesis method, nebulised spray pyrolysis (NSP). Functional properties such as magnetic behaviour, luminescence and band gap were studied and compared with the properties of NiO powder synthesised by a conventional reverse co-precipitation process (RCP) which also needed an additional calcination step. Although NiO crystallised in the cubic (rocksalt) form, Rietveld analysis of X-ray diffraction data revealed the synthesised nanopowders to be in a distorted cubic (rocksalt) or monoclinic form. This distortion resulted from the antiferromagnetic exchange interaction energy and increased magnetic surface anisotropy, as seen from the bond lengths determined from Fourier transform infra-red (FTIR) studies. Raman spectroscopy also confirmed the distortion in the structure indicated by the presence of a first order phonon peak. The band gap decreased in case of both the powders and was attributed to the shallow donor or acceptor levels created due to the presence of defect states as determined from photoluminescence studies. The NSP powders also exhibited a dependence on the excitation wavelength during emission luminescence. A mixed antiferromagnetic and ferromagnetic behaviour was observed in the NSP powders and the susceptibility of each was deconvoluted through low and high field magnetometry studies. Further, the nanopowders from both the processes showed “core-shell” magnetism, with paramagnetic behaviour in the shell and antiferromagnetism in the core. The thicknesses of the core and shell were also determined.     

Electrodeposition of Cu-doped ZnO nanowire arrays and heterojunction formation with p-GaN for color tunable light emitting diode applications

Copper-doped zinc oxide (ZnO:Cu) nanowires (NWs) were electrochemically deposited at low temperature on fluor-doped tin oxide (FTO) substrates. The electrochemical behavior of the Cu–Zn system for Cu-doped ZnO electrodeposition was studied and the electrochemical reaction mechanism is discussed. The synthesized ZnO arrayed layers were investigated by using SEM, XRD, EDX, photoluminescence and Raman techniques. X-ray diffraction analysis demonstrates a decrease in the lattice parameters of Cu-doped ZnO NWs. Structural analyses show that the nanomaterial is of hexagonal structure with the Cu incorporated in ZnO NWs probably by substituting zinc in the host lattice. Photoluminescence studies on pure and Cu-doped ZnO NWs shows that the near band edge emission is red-shifted by about 5 or 12 nm depending on Cu(II) concentration in the electrolytic bath solution (3 or 6 μmol l⁻¹). Cu-doped ZnO NWs have been also epitaxially grown on Mg doped p-GaN single-crystalline layers and the (ZnO:Cu NWs)/(p-GaN:Mg) heterojunction has been used to fabricate a light-emitting diode (LED) structure. The emission was red-shifted to the visible violet spectral region compared to pure ZnO. The present work demonstrates the ability of electrodeposition to produce high quality ZnO nanowires with tailored optical properties by doping. The obtained results are of great importance for further studies on bandgap engineering of ZnO, for color-tunable LED applications and for quantum well preparation.     

Synthesis and characterization of chlorinated hydroxyapatite as novel synthetic bone substitute with negative zeta potential

In the present work, chlorine doped hydroxyapatite (ClHA), with varying degrees of ion replacement was successfully synthesized by a simple ball milling technique. The resulting powders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy and particle size analyzer. The zeta potential of the powders was performed in physiological saline (0.154 M). The results confirmed the formation of apatite as the main phase in all chlorine substituted powders except for some incremental changes in the lattice parameter ‘a’ and unit cell volumes of the resultant powders. However, the crystallinity of the powders declined from 96% to 83%. Fourier transform infrared spectroscopy results confirmed the incorporation of Cl ions in the apatite lattice by the appearance of new bands at 677 cm^-1. FESEM results revealed that the crystallites have grown into grains with no major agglomeration. Vicker hardness test results revealed a hardness value of 2.65 ± 0.258 GPa for ClHA4 dense bodies at a load of 200g. Zeta potential analysis of the powders suggested that ClHA nanopowders can prove to be a potential bone implant material.     

Synthesis and magnetic properties of Zr doped ZnO Nanoparticles

Zr doped ZnO nanoparticles are prepared by the sol-gel method with post-annealing. X-ray diffraction results show that all samples are the typical hexagonal wurtzite structure without any other new phase, as well as the Zr atoms have successfully entered into the ZnO lattices instead of forming other lattices. Magnetic measurements indicate that all the doping samples show room temperature ferromagnetism and the pure ZnO is paramagneism. The results of Raman and X-ray photoelectron spectroscopy indicate that there are a lot of oxygen vacancies in the samples by doping element of Zr. It is considered that the observed ferromagnetism is related to the doping induced oxygen vacancies.