Room temperature synthesis and characterization of different morphological TbF3 nano/microcrystals

At room temperature, a simple solution-based procedure employing NaBF₄ as the fluoride source has been developed to selectively prepare different morphological TbF₃ nano/microcrystals (disks, peanuts and spindles) with an orthorhombic structure. The crystal structure, morphology and photoluminescence properties of the as-prepared TbF₃ crystals were investigated by x-ray powder diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The results revealed that large-scale and uniform disks with a mean thickness of 20 nm can be easily synthesized, and the spindle-like and peanut-like TbF₃ crystals were assembled from nanodisks. The effects of synthesis parameters such as NaBF₄, reaction time and molar ratio of the reactants were systematically investigated. The room temperature PL properties of these different morphological TbF₃ microcrystals were measured.     

Sonochemical synthesis and characterization of disk-like copper microcrystals

Disk-like Cu microcrystals were successfully synthesized with assistance of ultrasonic irradiation. The products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and thermogravimetric/differential thermal analysis (TGA/DTA). It was found that as-prepared Cu microcrystals were single crystals in nature and had a high crystallinity. They were mainly composed of disk-like and triangular Cu microcrystals with an average diameter of about 1 μm. There existed CuO on the outermost surface of the products, while a thin layer of Cu₂O was found between CuO and inner Cu microcrystals. Moreover, CTAB molecules were adsorbed on the surface of Cu microcrystals and they were desorbed while heated during TGA analysis. In addition, the influences of magnetic stirring, stillness, concentration of hexadecyltrimethylammonium bromide (CTAB) surfactant, and starting Cu salts on the morphology and size distribution of the final products have also been studied.     

微纳米结构硫酸钡的仿生合成与表征

以天然棉花和棉布作为生物模板成功制备了具有棉花和棉布纤维形貌的微纳米BaSO4晶体.研究了反应物浓度、反应温度、超声时问等因素对所得产物形貌的影响,确定了最佳反应条件.并用SEM、IR、XRD对最佳反应条件所得产物进行了表征.     

Preparation and characterization of reduced graphene oxide using ascorbic acid and sodium citrate as binary reductant

In this article, we successfully prepared transparent and gauze-like reduced graphene oxide (RGO) film with the thickness of only 1.32 nm using modified Hummers method and binary reductant consisting of ascorbic acid and sodium citrate. SEM, TEM, AFM, XRD, UV-Vis, and FTIR results all convincingly demonstrated that the reduction of graphite oxide using binary reductant is a feasible method to prepare RGO. In addition, the results also revealed that extending the oxidation time and increasing the ultrasonic oscillation reasonably might improve the oxidation degree of the graphite oxide, the ratio of the D-band Raman intensity to that of the G band (I_D/I_G) reached up to 1.244 in the as-obtained graphite oxide. Moreover, sodium citrate not only increased the reducibility of binary reduction system but also improved the dispersion of graphite oxide. Furthermore, reasonable annealing treatment could reduce the defects of RGO. It is a potential route to prepare RGO films and increase practical applications in large-scale production of graphene.     

Hydrothermal synthesis of bismuth sodium titanate particles with different morphologies

Nanostructured Na_0.5Bi_0.5TiO₃ particles have been synthesized by a hydrothermal synthesis method using a layered titanate H_1.07Ti_1.73O₄·nH₂O as a Ti precursor. The obtained Na_0.5Bi_0.5TiO₃ particles showed different morphologies including plate-like, wire-like, and cubic-like structures in different hydrothermal conditions. The effect of the NaOH concentration on the growth and morphology evolution of hydrothermally derived Na_0.5Bi_0.5TiO₃ powders were investigated. It was found that alkaline concentration had a great effect on the phase and morphology of the resultant powders. The dissolution–recrystallization and in situ topotactic transformation mechanisms were suggested in different alkaline concentrations according to the evolution process.     

Optical materials based on molecular nano/microcrystals and ultrathin films

Methodologies that we developed recently for the fabrication of molecular crystals with size variation in the nano to micro regime and polyelectrolyte templated mono and multilayer Langmuir-Blodgett films, are reviewed. The electronic absorption and strong fluorescence in the molecular nano/microcrystals are found to be size-dependent. Crystal structure and computational investigations provide a unified model to explain these observations. Role of polyelectrolyte templating in achieving stable and enhanced optical second harmonic generation response from LB films based on a hemicyanine amphiphile is highlighted.     

静电纺丝制备纳米海藻酸钠/魔芋葡甘聚糖-菊糖纤维膜

采用静电纺丝技术制备纳米海藻酸钠/魔芋葡甘聚糖-菊糖（SA/KGM-INU）纤维膜。采用流变仪分析研究了加入不同量SA对SA/KGM-INU溶胶流变特性的影响,利用SEM、DSC、FTIR和TGA研究了不同量SA对纳米SA/KGM-INU纤维膜结构和性能的影响。结果表明,纳米SA/KGM-INU复合纤维膜表面粗糙程度随SA含量增加而减小,黏度随SA含量的增加而增大,热稳定性随SA含量的增加而增强。纳米SA/KGM-INU纤维膜的制备,旨在为其它天然高分子基复合材料的研究开发提供一定的实验数据及理论基础。     

Hydrothermal synthesis and characterization of bismuth titanate regular tetrahedron crystallites

Bi₁₂TiO₂₀ (BTO) single crystals were synthesized by a hydrothermal process in KOH solution at 180 °C for 4 h from Ti(OC₄H₉)₄ and Bi(NO₃)₃·5H₂O compounds. The effects of processing parameters on the growth and morphology of BTO single crystals were investigated. The KOH concentration, reaction time and temperature had a great effect on the phase composition and morphology of the resultant crystals. BTO phase could not be obtained with KOH concentrations lower than 3 M or higher than 5 M. XRD, SEM and TEM were used to characterize the samples. BTO single crystals were regular tetrahedron in morphology and 10 μm or so in size.     

Solvothermal synthesis of sphere-like CuS microcrystals and improvement as nonenzymatic glucose sensor

In this article, we report the obtention of sphere-like copper sulfide (CuS) microcrystals with 3–5 μm diameter on a large scale by the solvothermal approach, which is simple, facile, and effective. The as-prepared products are well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), indicating that the sphere-like CuS microcrystals are composed of nanosheets with the uniform thickness of about 50 nm and have good morphology and high purity. The factors influencing the formation of the sphere-like CuS microcrystals are investigated in detail using SEM characterizations. Specially adjusting the quantity of thiourea can effectively control the formation of the flower-like, sphere-like, or irregularly spindle-like CuS microcrystals built by nanosheets. Based on the “oriented attachment mechanism,” CuS nanosheets are aligned with one another and point toward the spherical center, and further construct the sphere-like CuS microcrystals. The electrocatalytic oxidation of glucose in alkaline medium at the sphere-like CuS microcrystal-modified electrode has been monitored by cyclic voltammograms (CVs). Compared to the bare glassy carbon electrode, a couple of obvious redox peaks and the improved peak currents toward the glucose redox are examined at the sphere-like CuS sensor with the sensitivity of 117.3 μA cm^?2 mM^?1. The high electrochemical activity, good repetition, and stability indicate that the sphere-like CuS sensor has the potential application in the nonenzymatic glucose sensor.     

次亚磷酸钠还原法制备纳米铜颗粒

利用液相还原两步法,油酸为萃取荆和保护剂,葡萄糖和次亚磷酸钠将五水硫酸铜分别还原为氧化亚铜和单质铜,制备得到了粒度为50～100nm左右分散均匀的球形纳米铜颗粒,并用XRD、SEM和TEM对其进行了表征.结果表明,在油酸的保护下,采用液相还原两步法可制得分散性好、具有抗氧化性能的球形纳米铜颗粒.     

Hydrothermal synthesis and characterization of micro to nano sized carbon particles

Experiments under hydrothermal conditions were carried out to study the formation of elemental carbon through the decomposition of β-Silicon carbide (β-SiC) in the presence of organic compounds. The organic compounds were known to dissociate at low P-T conditions and produce the C–O–H supercritical fluids, which will have great influence on the decomposition of β-SiC. These hydrothermal runs under the influence of supercritical fluids will not only help in dissociating the silicon carbide into SiO₂ and free elemental carbon but also control the type of carbon phase formation. The Scanning Electron Microscopic (SEM) studies of the run products indicate the formation of the micron sized carbon particles having characteristic shapes like spherical/ovoid, scaly with metallic lustre and in some runs we find the formation of nano sized octahedral crystallites. Micro Raman study of these carbon particles reveals that bulk of the carbon formed in these runs were disordered / sp²–hybridized carbon but we also noticed the formation of black scales over the spherical particles and the octahedral crystallites which exhibits the sp³-hybridization having the characteristic sharp band at 1332 cm^-1, comparable to that of diamond powder. The octahedral crystallites are formed at the inner walls of the hollow spherical carbon particles. In any of the experimental runs we haven't used either the metal catalysts or the diamond seed with the charge material. Thus, the nucleation and formation of nano sized octahedral crystallites of diamond (sp³-hybridized carbon) in the present study at lower P-T conditions compared to that of its formation in nature is a significant breakthrough in the study of diamond synthesis.     

Tuning the size and optical properties in molecular nano/microcrystals: manifestation of hierarchical interactions

Intermolecular interactions, such as hydrogen bonding, dipolar and van der Waals, occurring in molecular crystals cover a range of magnitudes. As the crystal evolves from a relatively softer state in the nanoscopic size regime to a harder one in the microcrystalline and bulk solid state, the impact of the hierarchy of intermolecular interactions can be expected to emerge in a progressive fashion. The strongest interactions alone would be manifested at small sizes; as the crystal grows, the effect of the weaker ones will be added on, with the bulk crystals exhibiting the cumulative impact of the different interactions. We demonstrate this phenomenon through investigations of the solution, colloid, and solid state of a novel zwitterionic molecule based on the diaminodicyanoquinodimethane framework. A reprecipitation-digestion protocol is developed for the fabrication of nano/microcrystals of varying sizes. Microscopic and spectroscopic characterizations reveal tuning of the size and optical properties of this material. The optical absorption of the colloidal particles evolves with size towards that of the bulk solid, the emission showing a steady enhancement of intensity. Crystallographic investigations coupled with semiempirical computations provide a viable model to describe the range of observations in terms of the gradual accumulation of hierarchical intermolecular interactions.     

Bio-assisted synthesis and characterization of nanostructured bismuth (III) sulphide using Clostridium acetobutylicum

Nanostructured bismuth (III) sulphide is synthesized at room temperature using a hydrogen sulphide producing microorganism namely Clostridium acetobutylicum. On contrary to chemical routes involving both the high and room temperature methods, the present experimental procedure involves a bio-assisted approach. This method is free from the usage of toxic and hazardous chemicals making it an environment friendly route. The synthesized bismuth sulphide is characterized using transmission electron microscope (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). From our experiments we find that bismuth sulphide produced using this bio-assisted approach exhibits a hexagonal shaped plate-like structures and is stabilized by the extracellular proteins present in the culture medium.     

Novel solution route synthesis of low thermal conductivity nanocrystalline bismuth telluride

A novel synthesis approach based on a solution route has been developed for the fabrication of nanocrystalline bismuth telluride. The method consists of dissolving both bismuth and tellurium into the same organic solvent with the assistance of complexing agents and one-step coprecipitation of bismuth telluride. The synthesized nanocrystalline bismuth telluride powders possess rhombohedral crystal structure and are nanosheet/nanorod-like with an average size of between 30 and 40 nm. The thermal conductivity of the hot-pressed compact consolidated from the as-synthesized nanopowders is 0.39-0.45 Wm(-1)K(-1) in the temperature range of 323 to 523 K, which is at most one third of that of bulk bismuth telluride-based materials reported in the literature. Such low thermal conductivity of the investigated bismuth telluride is mainly attributed to substantially high concentration of grain boundaries provided by nanostructuring to scatter phonons intensively.     

Microwave synthesis of ZnO microcrystals with novel asymmetric morphology

This paper reports a discovery of novel morphological features of ZnO asymmetric micron-sized single crystals synthesized by microwave irradiation of W/O emulsions containing a Zn source in the inner aqueous phase. The influence of the zinc ion concentration on the size and shape is studied in detail. The morphological and structural properties show that the obtained ZnO powders are almost mono-dispersed ZnO single crystals with a novel morphology of truncated hexagonal pyramids ca. 1 μm in diameter. A scanning precession electron diffraction analysis reveals that the asymmetrically shaped ZnO single crystals thus obtained have a crystallographic c-axis perpendicular to the bottom hexagonal flat surfaces, and annular bright-field imaging indicates that the bottom surfaces are Zn-terminated ZnO(0001)-Zn polar faces. These new findings are led from a combination of well-controllable liquid-phase emulsion synthesis of the oxide powders and highly advanced atomic-resolution TEM imaging technique, suggesting for the first time a highly probable relationship between the polarity of the wurtzite-type crystal structure and the novel asymmetric morphology of the ZnO microcrystals obtained in this study.     

Preparation of a Novel Micro/nano Tubes via Electrospun Fiber as a Template

Poly (para-xylylene) hollow fibers with inner diameters can be prepared via template fibers electrospun from solutions. The PPX is deposited from the vapor phase and the template fiber is selectively removed by heat treatment or solvent extraction. The PPX is partially crystalline and the crystal modification depending on the route is used to extract the template fiber. The thermal stability of the hollow fibers is only slightly reduced relative to the bulk material and the same holds for the UV-stability.     

无模板剂法合成介孔NiAl_(10)O_(16)纳米粉及表征

不添加模板剂或者有机表面活性剂,通过摩尔比为1∶10的镍和铝硝酸盐水溶液与碳酸铵溶液水解的方法制备了高比表面积的介孔NiAl_(10)O_(16)纳米粉体。研究了焙烧温度对介孔NiAl_(10)O_(16)纳米粉体的比表面积和镍物种的影响。采用热重差热分析(TGDSC)、X射线粉末衍射(XRD)、氢气程序升温还原(H2-TPR)扫描电镜(SEM)、透射电镜(TEM)及N2吸附-脱附等手段表征。结果表明,制备的NiAl_(10)O_(16)纳米粉具有虫孔状介孔结构,比表面积在123~402m~2/g,孔径集中在2.9~6.6nm,孔容为0.20~0.29cm~3/g。随着焙烧温度的增加,样品的比表面积减小,孔径增加。样品中出现的表面铝酸镍和骨架铝酸镍,能够满足不同催化反应对镍物种的需求。     

Novel soft solution synthesis and characterization of submicromic LiCoVO4

A novel soft solution process has been used to prepare LiCoVO₄ by reacting Co(CH₃CH₂COO)₂, Li₂CO₃, NH₄VO₃ and citric acid. LiCoVO₄ powders were successfully prepared at as low as 450 °C in 4 h. Compared to the solid-state reaction processes, the soft solution process greatly reduced the temperature and the time for preparing LiCoVO₄. The inverse spinel structure and high crystallinity of the synthesized product has been confirmed by X-ray diffraction. Thermal analysis proves that the phase formation of the compound occurs at about 450 °C. The results of the IR investigations show that the band located at 820 cm⁻¹ corresponds to the stretching vibration mode of VO₄ tetrahedron with the A symmetry. SEM examination reveals a spherical grain distribution, the average particle size being typically lower than 1 μm. The quantitative result from ICP-AES analysis is Li_0.967Co_0.994VO₄.     

Controllable synthesis and optical properties of NdOHCO3 dodecahedral microcrystals

NdOHCO₃ dodecahedral microcrystals with an orthorhombic structure have been successfully synthesized by the hydrothermal method used urea as the precipitator. Experimental parameters, such as the reaction temperature, the reaction time, and the molar ratio of the starting reagents were examined. The as-synthesized products were characterized by powder X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence. The possible growth process of NdOHCO₃ dodecahedral microcrystals was discussed.     

Fabrication and characterization of nano/amorphous dual-phase FINEMET microwires

A nano/amorphous dual-phase FINEMET microwire was fabricated directly from molten alloy without any interstage annealing by a home-built melt extraction technique (MET). The microstructure, mechanical and pronounced electromagnetic interference shielding (EMI) effectiveness of this dual-phase microwire has been systematically evaluated. The structural analysis reveals that the as-cast FINEMET microwire consists of two distinct structures, i.e., amorphous and nanocrystalline phase due to their different cooling characteristics. Compared with other reported FINEMET alloys, the extracted microwire exhibits a superior high tensile strength of 1800 MPa. These nanocrystals enabled dual-phase microwires also exhibit large EMI SE values in the frequency range of 8–12 GHz (X-band) due to the multiple magnetic loss mechanisms associated with their intrinsic structural characteristics. The combination of excellent mechanical properties and electromagnetic properties make this kind of melt-extracted dual-phase FINEMET microwire promising for a range of structure and multifunctional applications.