Facile ultrasound-assisted synthesis of ZnO nanorods in an ionic liquid

ZnO nanocrystals have been synthesized by ultrasound-assisted synthesis from Zn(CH₃COO)₂2H₂O and NaOH in the neat room-temperature ionic-liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C₄mim][Tf₂N]. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the formed ZnO nanocrystals are of rod like shape with lengths from 50 to 100 nm and diameters of about 20 nm. X-ray diffraction (XRD) confirms the crystallinity as well as the sample purity. The band gap of the as-prepared ZnO nanorods was estimated to be 3.31 eV from UV–Vis absorption measurements. The photoluminescence spectrum shows the characteristic greenish emission of ZnO at room temperature (λ_max = 563 nm). The ZnO bonding levels have been determined by X-ray photoelectron spectroscopy (XPS). Nitrogen adsorption–desorption measurements show typical samples to have a specific surface area of 49.93 m²/g.     

Ultrasound-assisted synthesis of dentritic ZnO nanostructure in ionic liquid

A facile and environment-friendly sonochemical route to fabricate well-defined dentritic ZnO nanostructures in a room-temperature ionic liquid has been reported. The structure and morphology of the synthetic branch-shaped ZnO products were characterized by X-ray diffraction and transmission electron microscopy. The photoluminescence (PL) spectrum of the synthetic dentritic ZnO nanostructures exhibits a strong ultraviolet emission at 378 nm and a weak green emission at 532 nm respectively at room temperature. A plausible formation mechanism of dentritic ZnO nanostructures was discussed in detail.     

Low-temperature synthesis of binary cuprates from hydroxide precursor

Binary cuprates of Sr₂CuO₃₊ and SrCuO₂ have been synthesized at low temperatures below 500 °C under various values of partial oxygen-pressure by thermal decomposition of hydroxide precursors, Sr₂Cu(OH)₆ and SrCu(OH)₄, respectively. The tetragonal Sr₂CuO₃₊ ( 0.3) is obtained by the heat-treatment at 400 ° C and 0.2 atm. The value of appears to be independent of and unchangeable. On the other hand, the orthorhombic Sr₂CuO₃₊ ( 0) is obtained by the heat-treatment at 400 °C in flowing gas of N₂. For 0 < < 0.2 atm, a mixture of the tetragonal and orthorhombic phases is obtained. The orthorhombic SrCuO₂ is obtained by the heat-treatment at 500 ° C in flowing gas of N₂, although the tetragonal SrCuO₂, namely, the so-called infinite-layer compound is not obtained.     

Solution precursor plasma deposition of nanostructured ZnO coatings

Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance (∼65-80%) and reflectivity (∼65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 mΩ cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.     

Polyoxometalate-assisted electrochemical deposition of ZnO spindles in an ionic liquid

With the assistance of polyoxometalate (POM), ZnO spindles have been successfully synthesized in ionic liquid by electrochemical deposition. The as-obtained ZnO spindles are composed of small nanoparticles and have a porous structure with a specific surface area of 97.95 m²/g. Parallel experiments were also performed to understand the formation mechanism of the spindle-like ZnO. The experimental results showed that POM played a key role for the formation of the spindle-like ZnO. A possible formation mechanism was also proposed. The photoluminescence spectrum of the ZnO spindles exhibits a strong ultraviolet emission at 390 nm and a very weak visible emission at around 560 nm.     

Multi-capping agents in size confinement of ZnO nanostructured particles

In the present paper, we report a new approach to synthesize crystalline zinc oxide (ZnO) nanoparticles in the presence of multi-capping agents namely poly-vinylpyrrolidone (PVP) and citric acid (CA), with zinc acetate dihydrate and sodium hydroxide (NaOH as pellets) as a source material and their characteristic studies. The ZnO nanoparticles grown under this simple chemical process involve a heterogeneous chemical reaction in the presence of water as a solvent medium and reaction temperature of 100 °C for 48 h in a closed environment. The structural, optical and chemical features of ZnO nanoparticles were systematically studied by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Ultra Violet–visible (UV–vis) absorption spectroscopy. The Williamson–Hall (W–H) plot was also performed to distinguish the effect of crystalline size-induced broadening and strain-induced broadening at Full Width Half Maximum (FWHM) of the XRD profile. The growth mechanism of ZnO nanoparticles and the effective capping mechanism shown by each capping agent are briefly discussed.     

离子液体中氧化锌纳米结构的合成

以离子液体为介质，采用一步化学热分解反应制备出直径为10nm左右，长度达40-110nm的氧化锌纳米棒。利用IR，XRD，TEM以及SAED等测试手段对其进行了表征。实验结果表明：体系中离子液体的加入对产物形貌有着重要的影响。同时讨论了氧化锌纳米结构的生长机理。     

离子液体中微波辅助制备ZnO纳米棒及光学性能研究

在离子液体1-丁基-3甲基咪唑六氟磷酸盐[BMIM][PF6]水溶液中通过微波加热10min制备出ZnO纳米棒。用X射线衍射仪、场发射扫描电镜、紫外分光光度计和荧光分光光度计对其形貌、结构和性能进行了表征。研究表明,产物结晶性良好,产率高,大小均匀,平均直径为20nm,长度为400～500nm。通过对ZnO纳米棒形成机理和实验条件进行系统探讨,提出了三步反应机理,同时发现离子液体对产物的形貌起着关键作用。该方法简便、快速、环保,可推广运用于其它一维纳米功能材料的制备。     

A task specific basic ionic liquid for synthesis of flower-like ZnO by hydrothermal method

Flower-like ZnO morphology, with different shapes, have been successfully synthesized via a novel and environment-friendly hydrothermal method using zinc acetate and a task specific dicationic dibasic ionic liquid, [mmpim]₂[OH]₂, which plays an important role in fabrication of ZnO structure. The structure and morphology of the product were characterized by X-ray diffraction and scanning electron microscopy, which show different flower-like morphologies. Photoluminescence spectrum of the product exhibits a strong ultraviolet emission at 391 nm and two weak blue-green emissions at about 450 and 500 nm.     

Synthesis of nanostructured TiO2 particles in room temperature ionic liquid and its photocatalytic performance

Nanostructured TiO₂ particles were synthesized by sol-gel method with room temperature ionic liquid (RTIL) 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) as a reaction medium. The structure and morphology of TiO₂ nanoparticles were characterized with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The as-prepared TiO₂ nanoparticles present anatase crystal phase even without being calcined at high temperature, and show better photocatalytic performance in the degradation of methyl orange. The photocatalytic efficiency increases evidently along with increasing the concentration of nanostructure TiO₂, and the degradation percent can reach 100% at the optimal catalyst concentration (2.0 g/L).     

An efficient room-temperature route to uniform ZnO nanorods with an ionic liquid

Rod-like ZnO nanocrystals have been synthesized via an ultrasound-assisted way by the reaction between Zn(CH₃COO)₂·2H₂O and NaOH in the ionic liquid 1-butyl-3-methyl imidazole six hexafluorophosphoric acid salts ([BMIM][PF₆]) aqueous solution. The products were characterized by XRD, EDX, FESEM, TEM, HRTEM, UV-Vis and PL techniques. The as-prepared ZnO nanorods have a diameter of about 50 nm and a length of 1-2 μm. A plausible four-step mechanism was proposed to explain the formation of ZnO nanorods. It was found that the lowered ion diffusion velocity in the water-ionic liquid medium could largely contribute to the formation of the ZnO nanorods. The effects of experimental parameters on the formation of the products were also explored.     

Microwave-assisted hydrothermal synthesis of zinc oxide particles starting from chloride precursor

Zinc oxide (ZnO) was synthesized using a microwave assisted hydrothermal (MAH) process based on chloride/urea/water solution and under 800 W irradiation for 5 min. In the bath, Zn²⁺ ions reacted with the complex carbonate and hydroxide ions to form zinc carbonate hydroxide hydrate (Zn₄CO₃(OH)₆·H₂O), and the conversion from Zn₄CO₃(OH)₆·H₂O to ZnO was synchronously achieved by a MAH process. The as-prepared ZnO has a sponge-like morphology. However, the initial sponge-like morphology of ZnO could change to a net-like structure after thermal treatment, and compact nano-scale ZnO particles were finally obtained when the period of thermal treatment increased to 30 min. Pure ZnO nanoparticles was obtained from calcination of loose sponge-like ZnO particles at 500 °C. The analysis of optical properties of these ZnO nanoparticles showed that the intensity of 393 nm emission increased with the calcination temperature because the defects were reduced and the crystallinity was improved.     

Lyotropic liquid crystal directed synthesis of nanostructured materials

Abstract

This review introduces and summarizes lyotropic liquid crystal (LLC) directed syntheses of nanostructured materials consisting of porous nanostructures and zero-dimensional (0-D), one-dimensional (1-D) and two-dimensional (2-D) nanostructures. After a brief introduction to the liquid crystals, the LLCs used to prepare mesoporous materials are discussed; in particular, recent advances in controlling mesostructures are summarized. The LLC templates directing the syntheses of nanoparticles, nanorods, nanowires and nanoplates are also presented. Finally, future development in this field is discussed.     

Lyotropic liquid crystal directed synthesis of nanostructured materials

This review introduces and summarizes lyotropic liquid crystal (LLC) directed syntheses of nanostructured materials consisting of porous nanostructures and zero-dimensional (0-D), one-dimensional (1-D) and two-dimensional (2-D) nanostructures. After a brief introduction to the liquid crystals, the LLCs used to prepare mesoporous materials are discussed; in particular, recent advances in controlling mesostructures are summarized. The LLC templates directing the syntheses of nanoparticles, nanorods, nanowires and nanoplates are also presented. Finally, future development in this field is discussed.     

Fast one-step synthesis of ZnO sub-microspheres in PEG200

ZnO sub-microspheres were synthesized via a new, simple, and one-step method by using zinc acetate dihydrate as a precursor and PEG200 as a solvent and modifier. The effect of temperature (160–210 °C) on the crystallization, surface morphology, and luminescence properties of ZnO spheres was investigated using different characterization techniques, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, and room temperature photoluminescence. The results show that the ZnO crystal has a hexagonal wurtzite structure. The products have monodispersed spherical morphology with diameters in the range of 200–600 nm. They have intensive UV emission peaks at ~380 nm and relatively weak and broad green peaks at ~550 nm. The PEG200 molecules adsorb on the surface of ZnO spheres. On the basis of the experimental results, a mechanism was proposed to elucidate the formation of ZnO sub-micron spheres.     

Shape-controlled synthesis of single-crystalline cupric oxide by microwave heating using an ionic liquid

Cupric oxide (CuO) with leaf-like, chrysanthemum-like and rod shapes have been synthesized by microwave-assisted approach using an ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM]BF₄). By controlling the concentration of [BMIM]BF₄ and reaction time, shape transformation of CuO nanostructures could be achieved in a short period of time. The crystal structure and morphology of products were characterized by XRD, TG, FESEM/EDS, and TEM/SAED. A possible mechanism for the shape transformation of CuO nanostructures was proposed. In addition, UV–vis spectra were employed to estimate the band gap energies of the nanosized semiconductors.     

Synthesis,characterization and photocatalytic properties of nanostructured ZnO particles obtained by low temperature air-assisted-USP

ZnO nanoparticles were synthesized in a horizontal three zones furnace at 500 °C using different zinc nitrate hexahydrate concentrations (0.01 M, 0.1 M, and 1.0 M) as a reactive precursor solution by air assisted Ultrasonic Spray Pyrolysis (USP) method. The physico-chemical, structural and functional properties of synthesized ZnO nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), Brunauer, Emmett and Teller (BET) method, UV–vis spectroscopy and photoluminescence (PL) measurements. Also, the photocatalytic activities of ZnO synthesized from different precursor concentrations were evaluated by removal rate of methyleneblue (MB) under UV irradiation (365 nm) at room temperature. SEM revealed two types of ZnO nanoparticles: a quasi-spherical, desert-rose like shape of the secondary particles, which does not change significantly with the increasing of precursor solution concentration as well as some content of the broken spheres. Increasing the precursor solution concentration leads to the increase in the average size of ZnO secondary particles from 248 ± 73 to 920 ± 190 nm, XRD reveals the similar tendency for the crystallite size which changes from 23 ± 4 to 55 ± 12 nm in the analyzed region. HRTEM implies the secondary particles are with hierarchical structure composed of primary nanosized subunits. The PL spectra imply a typical broad peak of wavelength centered in the visible region exhibiting the corresponding red-shift with the increase of solution concentration: 560, 583 and 586 nm for the 0.01, 0.1 and 1.0 M solution, respectively. The reported results showed the photocatalytic efficiency of ZnO nanoparticles was enhanced by increased precursor concentration.     

Microwave-assisted hydrothermal synthesis of coralloid nanostructured nickel hydroxide hydrate and thermal conversion to nickel oxide

Coralloid nanostructured nickel hydroxide hydrate has been successfully synthesized by a simple microwave-assisted hydrothermal process using nickel sulfate hexahydrate as precursor and urea as hydrolysis-controlling agent. A pure coralloid nanostructured nickel oxide can be obtained from the nickel hydroxide hydrate after calcination at 400 °C. The thermal property, structure and morphology of samples were characterized by thermogravimetry (TG), temperature-programmed reduction (TPR), X-ray (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).     

One-pot synthesis of supported-nanoparticle materials in ionic liquid solvents

Highly porous supported-nanoparticle materials were synthesized by a rational method involving the encapsulation of poly(vinylpyrrolidone) (PVP)-stabilized Au nanoparticles into titania xerogels employing room temperature ionic liquids (1-butyl-3-methylimidazolium hexaflurophosphate, [BMIM]PF₆) as a medium followed by solvent extraction of the ionic liquid and calcination of the materials. The materials were thoroughly characterized by TEM, nitrogen adsorption-desorption isotherms, and XRD. After calcinations at 350 °C, the Au-titania system resulted in the formation of a highly mesoporous materials with BET surface areas of 200 m²/g and average pore sizes of 3-5 nm. These materials can find potential applications in catalysis and photocatalysis.     

Rapid carbothermal synthesis of nanostructured silicon carbide particles and whiskers from rice husk by microwave heating method

This paper reported a simple and rapid route to large-scale synthesis of nanostructured SiC powders using rice husk as the precursor. Rapid carbothermal reduction reactions were achieved in a 2.45 GHz microwave field in an argon atmosphere. The XRD patterns revealed that complete carbothermal reduction of silica was achieved at 1300 °C for 60 min or at 1500 °C for only 15 min by microwave heating, resulting in β-SiC formation. The FE-SEM images showed that the β-SiC powders were mixtures of particles and whiskers. The β-SiC particles had diameters of 60–130 nm and the β-SiC whiskers, which were several to tens of micrometers in length, had diameters of 110–170 nm. The β-SiC powder synthesized at 1500 °C for 15 min showed the highest BET surface area of 12.2 m²/g. Compared to the conventional heating method, the microwave heating method proved to be an efficient approach for synthesis of SiC in terms of energy and time saving, as well as for fabrication of nanostructured SiC.