Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration

The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.     

Synthesis, characterization and optical properties of star-like ZnO nanostructures

Star-like ZnO nanostructures were synthesized in bulk quantity by thermal evaporation method. The morphologies and structure of ZnO nanostructures were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor-solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow ultraviolet emission at around 380 nm and a broad green emission around 491 nm. Raman spectrum of the ZnO nanostructures was also discussed.     

Structural and magnetic properties of Zn1-xcoxO nanorods prepared by microwave irradiation technique

We have successfully synthesized large-scale aggregative flowerlike Zn1-xCo(x)O (0.0 < or = x < or = 0.07) nanostructures, consisting of many branches of nanorods at different orientations with diameter within 100-150 nm (tip diameter approximately 50 nm) and length of approximately 1 microm. The rods were prepared using Zinc nitrate, cobalt nitrate and KOH in 180 Watt microwave radiation for short time interval. The synthesized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and DC magnetization measurements. XRD and TEM results indicate that the novel flowerlike nanostructures are hexagonal with wurtzite structure and Co ions were successfully incorporated into the lattice position of Zn ions in ZnO matrix. The selected area electron diffraction (SAED) pattern reveals that the nanorods are single crystal in nature and preferentially grow along [0 0 1] direction. Magnetic studies show that Zn1-xCo(x)O nanorods exhibit room temperature ferromagnetism. This novel nanostructure could be a promising candidate for a variety of future spintronic applications.     

Influence of synthetic parameters on the enhanced photocatalytic properties of ZnO nanoparticles for the degradation of organic dyes: a green approach

Herein, we report a green synthetic strategy using aqueous leaves extract of Actinodaphne madraspatna Bedd (AMB) for the synthesis of ZnO NPs. The physical shape, size, thermal stability, surface area, surface composition and chemical state, morphological and optical properties of the synthesized ZnO NPs are well characterized through UV–Visible diffuse reflectance spectroscopy (DRS UV), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis–differential thermal analysis (TGA–DTA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) and X-ray photon spectroscopy (XPS). FT-IR spectrum of ZnO NPs showed a characteristic peak at 416.62 cm^?1. Optical studies of prepared ZnO NPs showed the bandgap values are reduced in the range of 3.05 to 2.96 eV. The XRD and TEM data revealed the synthesized ZnO NPs exist in wurtzite crystal structure with crystallite sizes of 18 nm to 68 nm range. The variation in bandgap, surface area and crystallite structure of ZnO NPs would be achieved by changing the experimental parameters. FESEM showed spherical-shaped structure. XPS result confirmed the atomic states of Zn and O. The green synthesized ZnO NPs were examined for the photocatalytic degradation of methylene blue (MB) and acid violet 17 (AV17) dyes under UV light and the rate constants ‘k’ was calculated. It is found that the green synthesized ZnO NPs with reduced bandgap showed enhanced photocatalytic activity with higher rate constant.

     

Structural and morphological studies of zinc oxide incorporating single-walled carbon nanotubes as a nanocomposite thin film

Pure zinc-oxide and a composition of zinc oxide-single walled carbon nanotubes (ZnO-SWCNTs) thin films were prepared by using a sol–gel doctor blade technique. A precursor of zinc acetate dehydrate (Zn(CH₃COO)₂·2H₂O), absolute ethanol (C₂H₅OH) and triethanolamine were mixed in one solution. Non-acid treatment SWCNTs were doped in the prepared solution. Structural and morphological properties of ZnO and ZnO-SWCNTs thin films were studied by means of X-ray diffractometer (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). XRD measurements indicated that the crystallite size of ZnO was bigger than the crystallite size of ZnO-SWCNTs; 0.4331 and 0.3386 nm, respectively. The FESEM images showed the hexagonal and nanorod structures of ZnO thin film and a broccoli-like ZnO nanostructures coated with CNTs for ZnO-SWCNTs thin film. The AFM analysis revealed smoother surface morphology of ZnO-SWCNTs thin film compared to the surface of pure ZnO thin film. TEM results captured the inner structures of ZnO and ZnO-SWCNTs. Inner and outer diameter of non-acid treatment SWCNTs were recorded about 5.09 and 14.95 nm, respectively. Photovoltaic performance of ZnO-SWCNTs based dye-sensitized solar cell (DSSC) showed high power conversion efficiency of 0.102 % compared to ZnO based DSSC (0.019 %). This study suggests that SWCNTs should be acid-treated to produce highly porous structure and greater surface area for better photovoltaic performance of the DSSCs.     

ZnO纳米棒阵列膜的制备及其光电化学性能研究

采用化学溶液沉积法,在ZnO纳米颗粒膜修饰的FTO导电玻璃基底上,制备了ZnO纳米棒阵列。用X射线衍射仪（XRD）、场发射扫描电子显微镜（FESEM）、透射电子显微镜（TEM）对样品进行表征。研究结果表明所制备的ZnO纳米棒为六方纤锌矿相单晶结构,沿c轴择优取向生长,平均直径约为40nm,长度约为900nm;ZnO纳米棒阵列生长致密,取向性较一致。以曙红Y敏化的ZnO纳米棒阵列膜为光阳极制作了染料敏化太阳能电池原型器件,在光照强度为100mW/cm2下,其开路电压为0.418V,短路电流为0.889mA/cm2,总的光电转换效率为0.133%。     

Synthesis of zinc oxide nanotetrapods by a novel fast microemulsion-based hydrothermal method

ZnO nanotetrapods have been successfully synthesized via a novel microemulsion-mediated hydrothermal route at 120 °C for 12 h. X-ray power diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffraction analysis (SAED), and electrochemical analysis (EA) were employed to study the structural features and electrochemical behavior of the products. It was found that these tetrapod ZnO nanostructures had a single crystal hexagonal wurtzite structure with lattice constants of a = 0.3249 nm and c = 0.5205 nm. And they exhibited a clearly electrocatalytic response, showing potential applications for sensor constructions.     

Synthesis and luminescence properties of ZnS:Mn/ZnS core/shell nanorod structures

Mn-doped ZnS nanorods synthesized by solvothermal method were successfully coated with ZnS shells of various thicknesses. The powder X-ray diffraction (XRD) measurements showed the ZnS:Mn nanorods were wurtzite structure with preferential orientation along c-axis. Transmission electron microscopy images (TEM) revealed that the ZnS shells formed from small particles, growing along a-axis orientation, which was proved by the XRD measurements. Room temperature photoluminescence (PL) spectra showed that the intensity of Mn emission first increased and then decreased with the thickening of the ZnS shells. The effects of ZnS shells on the luminescence properties of ZnS:Mn nanorods is discussed.     

Synthesis of ZnO flowers and their photoluminescence properties

Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH₃)₄²⁺ precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV (∼375 nm), blue (∼465 nm), and yellow (∼585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly found that the intensity of light emission at ∼585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 °C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.     

ZnO纳米棒Al掺杂和A1,N共掺杂的制备技术与光致发光性能

采用水热法首先合成了Al掺杂ZnO(AZO)纳米棒,在此基础上通过550℃的氨气氛中退火制备了Al,N共掺杂ZnO(ANZ())纳米棒.运用X射线衍射(XRD),场发射扫描电镜(FESEM),透射电子显微镜(TEM),X射线能谱(EDS)和光致发光(PL)对样品进行了表征与分析.结果表明,制备的AZO和ANZ()纳米棒...     

Self-assembly of ZnO nanosheets into nanoflowers at room temperature

A singularity flower-like ZnO nanostructure was prepared on a large scale through a very simple solution method at room temperature and under ambient pressure in a very short time. The flower-like ZnO nanostructures were self-assembled by thin and uniform nanosheets, with a thickness of around 5 nm. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology. The possible growth mechanism was discussed based on the reaction process. The blue shift in the UV-vis spectra of the ZnO nanostructures was also observed.     

Photocatalytic degradation of organic dyes with manganese-doped ZnO nanoparticles

Manganese-doped and undoped ZnO photocatalysts were synthesized via wet-chemical techniques. Doping of ZnO with manganese (Mn(2+)) was intended to create tail states within the band gap of ZnO. These can subsequently be used as efficient photocatalysts which can effectively degrade organic contaminants only with visible light irradiation. Photocatalysts prepared with these techniques, which were characterized with transmission electron microscopy (TEM), infrared spectroscopy (FTIR), photo-co-relation spectroscopy (PCS) and UV-vis-spectroscopy showed significant difference in the optical absorption of Mn-doped ZnO. Enhancement in optical absorption of Mn-doped ZnO indicates that it can be used as an efficient photocatalyst under visible light irradiation. The photo-reduction activities of photocatalysts were evaluated using a basic aniline dye, methylene blue (MB) as organic contaminant irradiated only with visible light from tungsten bulb. It was found that manganese-doped ZnO (ZnO:Mn(2+)) bleaches MB much faster than undoped ZnO upon its exposure to the visible light. The experiment demonstrated that the photo-degradation efficiency of ZnO:Mn(2+) was significantly higher than that of undoped ZnO and might also be better than the conventional metal oxide semiconductor such as TiO(2) using MB as a contaminant.     

Synthesis and characterization of ZnO nanowires for nanosensor applications

In this paper we report the synthesis of ZnO nanowires via chemical vapor deposition (CVD) at 650 °C. It will be shown that these nanowires are suitable for sensing applications. ZnO nanowires were grown with diameters ranging from 50 to 200 nm depending on the substrate position in a CVD synthesis reactor and the growth regimes. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Raman spectroscopy (RS) have been used to characterize the ZnO nanowires. To investigate the suitability of the CVD synthesized ZnO nanowires for gas sensing applications, a single ZnO nanowire device (50 nm in diameter) was fabricated using a focused ion beam (FIB). The response to H₂ of a gas nanosensor based on an individual ZnO nanowire is also reported.     

Synthesis of ZnO nanosheets by room-temperature decomposition of a layered precursor synthesized by microwave heating

ZnO nanosheets with the wurtzite structure have been successfully synthesized via a microwave-assisted solution method. The thicknesses of ZnO nanosheets are in the range of 5–10 nm and lateral sizes up to 1 μm. The surfaces of ZnO nanosheets are planes of wurtzite structure. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM). The optical and thermal properties were investigated with UV–Visible absorption spectra, thermogravimetric analysis (TG) and differential scanning calorimetric analysis (DSC).     

Nanoforests composed of ZnO/C core–shell hexagonal nanosheets: fabrication and growth in a sealed thermolysis reactor and optical properties

An efficient method was developed for fabricating a highly porous nanoforest structure composed of ZnO/C core–shell hexagonal nanosheets (HNSs). Compact thermolysis of zinc acetate dihydrate in a sealed bath reactor at 400 °C over 20 h yielded the nanoforest structures. A carbon shell layer coating was applied in situ during the growth of the ZnO nanosheet core. The structures, morphologies, growth processes, compositions, and binding characteristics of the ZnO/C core–shell HNS nanoforests were analyzed using multi-purpose high-performance X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS) techniques. XRD and XPS results suggest the existence of oxygen vacancy defects in the core surface of ZnO/C core–shell. The ZnO/C core–shell HNS nanoforests exhibited strong absorption features from the visible to the near-IR region (400–1670 nm), and the nanoforest films showed high electrical conductivity.     

Utilization of ZnO nanocones for the photocatalytic degradation of acridine orange

A facile aqueous solution process was used to synthesize well-crystalline ZnO nanocones at 60 degrees C by using zinc nitrate hexahydrate and sodium hydroxide. The morphological, structural and optical properties of the synthesized ZnO nanocones were investigated by using field emission scanning electron microscopy (FESEM) attached with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) equipped with high-resolution (HRTEM), X-ray diffraction (XRD) pattern, Fourier transform infrared (FTIR) spectroscopy and UV-Vis. spectroscopy measurements. The structural and optical properties of the as-synthesized nanocones confirmed a pure and well crystalline product possessing wurtzite hexagonal phase. The as-synthesized ZnO nanocones were used as photocatalyst for the efficient photocatalytic degradation of acridine orange. The acridine orange was almost completely degraded within 105 minutes. This research demonstrates that the simply synthesized ZnO nanostructures could be efficient photocatalyst for the photocatalytic degradation of various organic dyes and chemicals.     

Single crystalline ZnO nanorods grown by a simple hydrothermal process

Single crystalline ZnO nanorods with wurtzite structure have been prepared by a simple hydrothermal process. The microstructure and composition of the products were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, energy dispersive X-ray spectrum (EDS) and Raman spectrum. The nanorods have diameters ranging from 100 nm to 800 nm and length of longer than 10 µm. Raman peak at 437.8 cm^− 1 displays the characteristic peak of wurtzite ZnO. Photoluminescence (PL) spectrum shows a blue light emission at 441 nm, which is related to radiative recombination of photo-generated holes with singularly ionized oxygen vacancies.     

One-pot simple synthesis and characterisation of Mn2+-doped GaN nanorods by RAPET method

In this work, we display one-step reactions under autogenic pressure at elevated temperature (RAPET) method-based synthesis of Mn-doped GaN nanorods by varying the atomic ratio of Mn:Ga as 0, 0.02, 0.04, 0.06 and 0.08, respectively. The synthesised nanorods are characterised by X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) and Raman spectral methods. It is observed that there is a decrease in the lattice constant with an increase in the concentration of Mn (from 0.02 to 0.08 wt%). Moreover, the smaller covalent radius of Mn is the key for the doping process. The Mn-doped GaN nanocrystals show rod-like morphology with a length of 40–50 nm and width of 8–12 nm. This size factor mainly depends on the doping of Mn [from transmission electron microscopy (TEM) analysis] into GaN components. Well-defined lattice fringes are elucidated for the growth of crystalline hexagonal GaN (wurtzite type) nanocrystals.     

Synthesis of SiO2-coated ZnMnFe2O4 nanospheres with improved magnetic properties

A core-shell structured composite, SiO2 coated ZnMnFe2O4 spinel ferrite nanoparticles (average diameter of approximately 80 nm), was prepared by hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of ZnMnFe2O4 nanoparticles (average diameter of approximately 10 nm) synthesized by a hydrothermal method. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). The magnetic measurements were carried out on a vibrating sample magnetometer (VSM), and the measurement results indicate that the core-shell samples possess better magnetic properties at room temperature, compared with paramagnetic colloids with a magnetic core by a coprecipitation method. These core-shell nanospherical particles with self-assembly under additional magnetic fields could have potential application in biomedical systems.     

Green hydrothermal synthesis and photoluminescence property of ZnO2 nanoparticles

ZnO₂ nanoparticles were synthesized via a green hydrothermal method using ZnO powder and 30% H₂O₂ aqueous solution as the starting materials, and characterized by X-ray diffraction (XRD), Raman spectra, energy dispersive X-ray (EDX) spectra, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and room temperature photoluminescence (RTPL) spectra. It was found that suitable reaction temperature (e.g., 80-140 °C) played an important role in obtaining pure cubic phase ZnO₂ nanoparticles. The RTPL spectra disclosed that the as-synthesized ZnO₂ nanoparticles exhibit one strong emission band centered at around 400 nm and one very weak emission band at around 474 nm, which may have originated from the band edge emission and the oxygen vacancy, respectively.