Electrochemical synthesis of CdS nanowires by underpotential deposition in anodic alumina membrane templates

Cadmium sulfide (CdS) nanowires were electrosynthesized within the pores of the anodic alumina membranes (AAM) using underpotential deposition (UPD) through an electrochemical co-deposition at room temperature (25 °C). The nanowire arrays were grown from an aqueous solution of CdSO₄, ethylenediaminetetraacetic acid (EDTA), and Na₂S at pH 4.0. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy, and energy dispersive spectroscopy (EDS) were employed to characterize the nanowires. These nanowires have uniform diameters of approximately 90 nm, and their lengths are up to 7 μm. XRD analysis reveals that the electrosynthesized nanowires deposited at −500 mV (vs. Ag/AgCl) have a preferential orientation along (1 1 0) direction for hexagonal crystal. Electrochemical and EDS results of the deposits confirm that the atomic ratio of Cd to S is very close to 1:1 stoichiometry. UV-vis absorption measurement shows a blue-shifted absorption at 488 nm because of the quantum confinement at low dimensions.     

纳米氧化锌的生物法合成及固定脂肪酶的研究

采用植物乳杆菌合成了纳米氧化锌粒子并成功用于脂肪酶的固定化。将筛选得到的高耐硫酸锌的植物乳杆菌株LP4用于纳米氧化锌的合成,采用扫描电镜、透射电镜和X射线衍射等一系列分析测试手段对得到的产物进行了表征。结果显示合成的材料为直径9~35 nm球形颗粒,在359 nm处有最大吸收峰,晶体呈六方体纤锌矿结构,X射线衍射峰与标准纳米氧化锌对比结果一致,这些结果表明植物乳杆菌株LP4成功合成了纳米氧化锌。然后将合成得到的纳米氧化锌粒子用于固定假丝酵母（Candida sp.）脂肪酶,与普通氧化锌以及传统法合成的纳米氧化锌粒子相比,生物法合成的纳米氧化锌固定效果最好,固定化酶的酶活收率分别比普通氧化锌和传统纳米氧化锌提高114.2%和20.5%。论文还对该生物纳米固定化酶的pH和热稳定性以及重复使用性能进行了测定,结果表明酶固定化后稳定性明显提高,而且具有较好的重复使用性能。     

Effect of nickel doping on structural,optical, electrical and ethanol sensing properties of spray deposited nanostructured ZnO thin films

Undoped and nickel (Ni)-doped ZnO thin films were spray deposited on glass substrates at 523 K using 0.1 M of zinc acetate dihydrate and 0.002–0.01 M of nickel acetate tetrahydrate precursor solutions and subsequently annealed at 723 K. The effect of Ni doping in the structural, morphological, optical and electrical properties of nanostructured ZnO thin film was investigated using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV–vis Spectrophotometer and an Electrometer respectively. XRD patterns confirmed the polycrystalline nature of ZnO thin film with hexagonal wurtzite crystal structure and highly oriented along (002) plane. The crystallite size was found to be increased in the range of 15–31 nm as dopant concentration increased. The SEM image revealed the uniformly distributed compact spherical grains and denser in the case of doped ZnO thin films. All the films were highly transparent with average transmittance of 76%. The measured optical band gap was found to be varied from 3.21 to 3.09 eV. The influence of Ni doping in the room temperature ethanol sensing characteristics has also been reported.     

Formation of nanoparticles during melt mixing a thermotropic liquid crystalline polyester and sulfonated polystyrene ionomers: Morphology and origin of formation

The formation of nanoparticles and the mechanism of their formation in a blend of a thermotropic liquid crystalline polyester (LCP) and the zinc salt of a lightly sulfonated polystyrene ionomer (Zn-SPS) were investigated using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and gas chromatography-mass spectroscopy (GC-MS). Transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) were used to study the morphology of the blends and structure of nanoparticles. The origin of nanoparticle formation appeared to be related to the development of phenyl acetate chain ends on the LCP that arose due to a chemical reaction between the LCP and residual catalytic amounts of zinc acetate and/or acetic acid that were present from the neutralization step in the preparation of the ionomer. Two-dimensional X-ray diffraction patterns for the blends revealed that chain-packing within nanoparticles was different than that of the LCP or the homopolymers prepared from the LCP co-monomers. The crystals formed in the nanoparticles were also stable to much higher temperature (>350 °C) than the parent LCP crystallites that melted at ∼280 °C.     

PECVD of h-BN and c-BN films from boranedimethylamine as a single source precursor

Boron nitride (BN) thin films have been successfully synthesised via low pressure plasma enhanced chemical vapour deposition (PECVD) by using boranedimethylamine, BH₃NH(CH₃)₂, as a single source precursor in the temperature range 280-550 °C in a nitrogen-argon atmosphere. The plasma power was optimised with the aim of obtaining suitable cubic/hexagonal phase ratios. The annealing of the h-BN films at temperatures up to 1000 °C in a nitrogen atmosphere, at normal pressure, gave rise to a complete transformation into the cubic phase. FTIR measurements provided a suitable method for identifying the structure of BN films. UV-vis spectroscopy was carried out in order to investigate the optical behaviour of the films.     

Iron oxide supported sulfated TiO2 nanotube catalysts for NO reduction with propane

Sulfated TiO₂ nanotubes and a series of iron oxide loaded sulfated TiO₂ nanotubes catalysts with different iron oxide loadings (1 wt%, 3 wt%, 5 wt% and 7 wt%) were prepared and calcined at 400 °C. The physico-chemical properties of the catalysts were studied by using XRD, N₂-physisorption, Raman spectroscopy, SEM-EDX, TEM, XPS, and pyridine adsorption using FTIR and H₂-TPR techniques. It was observed that iron oxide was highly dispersed on the sulfated TiO₂ nanotube support due to its strong interaction. The activity of these catalysts in the catalytic removal of NO with propane was also studied in the temperature range of 300–500 °C. Highest activity (90% NO conversion) was observed with 5 wt% iron oxide supported on sulfated TiO₂ catalyst at 450 °C. Selective catalytic reduction of NO activity of the catalysts was correlated with iron oxide loading, reducibility, and the Brönsted and Lewis acid sites of the catalysts. The catalyst also showed good stability under studied reaction conditions that no deactivation was observed during the 50 h of reaction.     

Synthesis of LaAlO3 powder using triethanolamine

LaAlO₃ powders were successfully synthesized by pyrolysis of complex compounds of lanthanum and aluminum with triethanolamine (TEA). The precursors and the derived powders were characterized by simultaneous thermogravimetry analysis (TG) and differential scanning calorimetry analysis (DSC), X-ray diffractometry (XRD), specific surface area measurements, and transmission electron microscopy (TEM). Pure LaAlO₃ phase was obtained at 775 °C for 2 h or 750 °C for 4 h, without formation of any intermediate phase. Pores were found from TEM images of LaAlO₃ powders prepared at 800 °C for 2 h.     

Solvothermal synthesis of microsphere ZnO nanostructures in DEA media

Microsphere ZnO nanostructures (ZnO-MNs) were synthesized via solvothermal method in diethanolamine (DEA) media. DEA was utilized to terminate the growth of ZnO nanoparticles which forms the ZnO-MNs. The ZnO-MNs were characterized by a number of techniques, including X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (SEM). The ZnO-MNs prepared by solvothermal process at the temperature of 150 °C for 6, 12, 18, and 24 h exhibited a hexagonal (wurtzite) structure with sizes ranging from 2 to 4 μm. The growth mechanism and morphology of the ZnO-MNs were also investigated, and it was found that the ZnO-MNs were formed by ZnO nanoparticles with average particle size of 25 ± 5 nm. To show role of DEA in the formation of Zn-MNs, effect of MEA (monoethanolamine) and TEA (triethanolamine) on morphology of the final product are also investigated. The results showed that DEA is a good polymerization agent that can be used as a stabilizer in the solvothermal technique for preparing fine ZnO powder.     

Preparation and characterization of transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency

Transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency were reported in this paper. First, zinc oxide (ZnO) precursor was synthesized via the homogeneous precipitation method and ZnO nanoparticles were then made by calcination of the precursor at different temperature. The structural properties of the as-prepared ZnO nanoparticles were studied in detail using thermogravimetry (TGA), differential thermal analysis (DTA), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and transmission electron microscopy (TEM), respectively. Transparent ZnO/epoxy nanocomposites were subsequently prepared from transparent epoxy (EP-400) and as-prepared ZnO nanoparticles via in situ polymerization. Optical properties of ZnO/epoxy nanocomposites, namely visible light transparency and UV light shielding efficiency, were studied using an ultraviolet-visible (UV-vis) spectrophotometer. The optical properties of the as-obtained nanocomposites were shown to depend on ZnO particle size and content. The nanocomposite containing a very low content (0.07% in weight) of ZnO nanoparticles with an average particle size of 26.7 nm after calcination at 350 °C possessed the most optimal optical properties, namely high-visible light transparency and high-UV light shielding efficiency, that are desirable for many important applications.     

Investigation of phase separation of nano-crystalline anatase from TiO2SiO2 thin film

In this work, a set of SiO₂–TiO₂ mixed oxides was prepared by the polymeric sol–gel route and deposited on glass substrate through the dip coating technique. Then, the effect of different important preparation parameters (sol–gel stabilizers, Ti content, and heat treatment) on the phase separation was investigated. The developed films were heat treated at 500 °C and characterized using TGA/DTA, FTIR, XRD, SEM, and AFM. The results showed that TiO₂ segregation can be controlled by selecting an appropriate composition of diethanolamine (DEA) and methyl methacrylate (MMA) for preparation of polymeric silica–titania sol. Besides, anatase phase in the samples were crystallized without any stabilizers within heat treatment procedure at 500 °C; however, using appropriate composition of DEA and MMA crystallization rate significantly decreased.     

Poly(acrylic acid)-guided synthesis of helical polyaniline microwires

We present a facile method to prepare helical polyaniline (PANI) microwires or rods guided by poly(acrylic acid) (PAA). The average length and diameter of the helical strands were about 3.5 μm and 500 nm, respectively. The pitch distance was about 400 nm. The morphology of the helical PANI microwires was affected by the concentration of PAA. As the concentration was decreased to below 0.05 mg/ml, helical wire- or rod-like products were observed. The structure of the helical polyaniline microwires were characterized by means of TEM, SEM, XRD, FTIR and UV-vis spectroscopy.     

Formation of nanosize ZnO particles by thermal decomposition of zinc acetylacetonate monohydrate

Formation of ZnO particles by thermal decomposition of zinc acetylacetonate monohydrate in air atmosphere has been investigated using XRD, DTA, FT-IR, and FE-SEM as experimental techniques. ZnO as a single phase was produced by direct heating at ≥200 °C. DTA in air showed an endothermic peak at 195 °C assigned to the ZnO formation and exothermic peaks at 260, 315 and 365 °C, with a shoulder at 395 °C. Exothermic peaks can be assigned to combustion of an acetylacetonate ligand released at 195 °C. ZnO particles prepared at 200 °C have shown no presence of organic species, as found by FT-IR spectroscopy. Particles prepared for 0.5 h at 200 °C were in the nanosize range from ∼20 to ∼40 nm with a maximum at 30 nm approximately. The crystallite size of 30 nm was estimated in the direction of the a₁ and a₂ crystal axes, and in one direction of the c-axis it was 38 nm, as found with XRD. With prolonged heating of ZnO particles at 200 °C the particle/crystallite size changed little. However, with heating temperature increased up to 500 or 600 °C the ZnO particle size increased, as shown by FE-SEM observation. Nanosize ZnO particles were also prepared in two steps: (a) by heating of zinc acetylacetonate monohydrate up to 150 °C and distillation of water and organic phase, and (b) with further heating of so obtained precursor at 300 °C.     

Synthesis and characterization of nanocrystalline forsterite through citrate–nitrate route

Nanocrystalline forsterite, Mg₂SiO₄, powder was synthesized according to the citrate–nitrate technique using an aqueous solution of magnesium nitrate, colloidal silica, citric acid, and ammonia. The dried precursor and the powders calcined at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The initial crystallization temperature of forsterite was around 770 °C while fully crystallized forsterite was obtained at 860 °C with a crystallite size of about 30 nm.     

Characterization of SrWO4-PVA and SrWO4 spiders’ webs synthesized by electrospinning

Mixtures of strontium acetate, ammonium metatungstate hydrate, and different contents of poly (vinyl alcohol) (PVA, 125,000 MW) were electrospun by a +15 kV direct voltage to synthesize SrWO₄-PVA spiders’ webs. The spider's web, synthesized from the solution containing 1.3 g PVA, was further calcined in air at 300-600 °C for 3 h. The SrWO₄-PVA spider's web was analyzed by thermogravimetric analyzer (TGA) to specify the evaporation and decomposition of PVA and volatile components. In addition, the SrWO₄-PVA and SrWO₄ spiders’ webs were characterized by X-ray diffractometer (XRD), selected area electron diffraction (SAED), scanning and transmission electron microscopes (SEM, TEM), and ultraviolet (UV)-visible and photoluminescence (PL) spectrometers, including the vibration modes by Fourier transform infrared (FTIR) and Raman spectrometers. A possible formation mechanism of SrWO₄-PVA and SrWO₄ spiders’ webs was also proposed according to the experimental results.     

Synthesis and characterization of Al2O3 nanopowders by a simple chitosan-polymer complex solution route

Al₂O₃ nanopowders were synthesized by a simple chitosan-polymer complex solution route. The precursors were calcined at 800–1200 °C for 2 h in air. The prepared samples were characterized by XRD, FTIR and TEM. The results showed that for the precursors prepared with pH 3–9 γ-Al₂O₃ and δ-Al₂O₃ are the two main phases formed after calcination at 800–1000 °C. Interestingly, when the precursor prepared with pH 2 was used, α-Al₂O₃ was formed after calcination at 1000 °C, and pure α-Al₂O₃ was obtained after calcination at 1200 °C. The crystallite sizes of the prepared powders were found to be in the range of 4–49 nm, as evaluated by the XRD line broadening method. TEM investigation revealed that the Al₂O₃ nanopowders consisted of rod-like shaped particles and nanospheres with particle sizes in the range of 10–300 nm. The corresponding selected-area electron diffraction (SAED) analysis confirmed the formation of γ- and α-Al₂O₃ phases in the samples.     

Large scale synthesis of non-transformable tetragonal Sc2O3, Y2O3 doped ZrO2 nanopowders via the citric acid based gel method to obtain plasma sprayed coating

Non-transformable tetragonal scandia, yttria doped zirconia (SYDZ) nanopowders were prepared in large scale by the citric acid (CA) based gel method. The effect of ethylene glycol monobutyl ether (EGM):CA ratios and pH on the structure, morphology and SYDZ particle size was investigated. The microstructure of SYDZ was characterized by XRD, Raman scattering, TG–DTA, SEM, TEM, and FTIR analyses. The SYDZ nanopowders, synthesized with 1Zr⁴⁺:4EGM:4CA mole ratio in acidic medium (pH ∼1) at 700 °C, had an average diameter of 15±2 nm. Finally, air plasma spray (APS) coatings were produced from nanostructured SYDZ agglomerated powders.     

Preparation of highly crystalline nanofibers on Fe and Fe-Ni catalysts with a variety of graphene plane alignments

The present study confirmed that highly crystalline nanofibers with controlled structure may be prepared over Fe and Fe-Ni alloy catalysts. The degree of graphitization of various carbon nanofibers (CNFs) was analyzed by using C(0 0 2) peaks from the XRD profiles. The C(0 0 2) peaks of CNFs over Fe catalyst shifted to higher angle and became narrower as the preparation temperature increased from 560 to 620 °C. Tubular CNFs prepared at temperature higher than 630 °C showed lower 2θ angles compared to those of platelet fibers. CNFs prepared over Fe-Ni catalysts tended to resemble those prepared over Fe catalysts. The degree of graphitization of platelet CNFs resembled natural graphite, while d_0 0 2 of the tubular CNFs showed values below the 3.39 Å reported as a theoretical minimum for a cylindrical alignment. Lc_0 0 2 of platelet and tubular CNFs increased by heat treatment at 2000 and 2800 °C though d_0 0 2 changed little. A transverse section of platelet and tubular CNFs had a hexagonal shape, not a round shape. The hexagonal column allows AB stacking of hexagonal planes that can give perfect hexagonal alignment.     

Electrodeposited Prussian blue films: Annealing effect

The correlation between the temperature-dependent electrochromic (EC) activity and other properties of galvanostatically deposited Prussian Blue (PB) films is presented here. Films subjected to annealing treatment in air at temperatures up to 500 °C were characterized by a variety of techniques which include TGA, XRD, FTIR, UV-vis spectrophotometry, SEM, XPS, cyclic voltammetry etc. The as-deposited X-ray amorphous hydrated PB films were blue in color and had Fe in both Fe^II and Fe^III valence states and were electrochromically active. Consequent to changes in the valence state, degree of hydration and coordination environment of the iron ions upon annealing, EC activity and morphology of the films exhibited dramatic changes. Annealing at moderate temperatures retained the blue color of the films and decreased the EC activity consistent with dehydration and decreased the Fe^II content. Lack of EC activity at higher temperatures was consistent with dehydration and quenching of Fe^II states accompanied with change of color from blue to rust (Fe^III) typical of Fe₂O₃. Independent of the annealing temperature, the films retained their amorphicity, however, prolonged annealing at 500 °C yielded hexagonal Fe₂O₃.     

Fabrication of highly dispersed crystallized nanoparticles of barium strontium titanate in the presence of N,N-dimethylacetamide

Highly dispersed nanoparticles of barium strontium titanate (BST) were successfully synthesized by hydrolysis method using N,N-dimethylacetamide as a solvent at 120 °C and 140 °C. X-ray diffraction analysis (XRD) showed that the as-prepared particles presented a perovskite polycrystalline structure. The result of transmission electron microscopy (TEM) images revealed the particle size in the range of 5-30 nm. The composition without any annealing treatment characterized with the parallel plate capacitor method displayed good dielectric properties.     

Formation of nano SiC whiskers in bauxite-carbon composite materials and their consequences on strength and density

SiC whisker is excellent in characteristics such as specific strength and chemical stability, and is useful as a composite reinforcing material. In this paper, the effect of the formation of in situ nano SiC whiskers on strength and density of bauxite-carbon composites was studied. Samples were prepared composed of 65 wt.% bauxite, 15 wt.% SiC-containing material, 10 wt.% coke, 10 wt.% resole and different values of silicon additives. The pressed samples were cured at 200 °C (2 h) and fired at 1100 °C and 1400 °C (2 h). XRD, SEM, TEM, EDX, FTIR and STA were used to characterize the samples. These characterizations indicated that SiC nano whiskers, 50-90 nm, are single crystalline β-SiC with mechanism of the formation VLS. So, firing temperature is an important factor. As, SiC nano whisker was formed at 1400 °C and improved CCS values up to four times in sample containing 6 wt.% ferrosilicon.