Flower-like boehmite nanostructure formation in two-steps

Reaction between AlCl₃ and TEA (triethanolamine) gave Al(OH)₃ colloidal nanocrystals that were precursors to nucleation and growth of boehmite under hydrothermal conditions. Transition electron microscopic (TEM) observations revealed that flower-like nanostructures were produced through a binary self-assembly system. In the first stage, nanostrips organize themselves to form a bundle, because of NH₄⁺ and TEA. In the second stage, the bundles form flower-like nanostructures due to the interaction of nitrate with TEA. The size of the nanopetals (length 100–200?nm; width 100–150?nm; and thickness 20–70?nm) was measured through TEM. X-ray diffraction and Brunauer–Emmett–Teller (BET-N₂) results demonstrate that the obtained nanostructures were composed of a pure AlOOH phase with a surface area of 160?m^2?g^?1. The effect of Cl?ˉ on the growth of boehmite 3-D nanoarchitectures in the presence of NO₃ˉ was also investigated.     

Synthesis of single crystal manganese oxide octahedral molecular sieve (OMS) nanostructures with tunable tunnels and shapes

A new and facile route is reported to manipulate the self-assembly synthesis of hierarchically ordered Rb-OMS-2 and pyrolusite with an interesting flowerlike morphology by a direct and mild reaction between rubidium chromateand manganese sulfate without any organic templates. The crystal forms, morphologies, and tunnel sizes of the obtained OMS materials can be controlled. A mechanism for the growth of manganese dioxides with flowerlike architectures was proposed. The obtained products exhibit potential for use in catalysis and other applications.     

Solution-based chemical synthesis of boehmite nanofibers and alumina nanorods

This article reports an easy chemical method of synthesizing boehmite nanofibers by a modified sol-gel process involving aluminum isopropoxide precursor. Nanorods of gamma-alumina have been successfully prepared after dehydration of the viscous sol at 600 degrees C for 4 h in air. The boehmite nanofibers and gamma-alumina nanorods were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy for surface chemistry and functional groups, scanning electron microscopy, high-resolution transmission electron microscopy with selected area electron diffraction, and energy-dispersed spectroscopy for morphology and structure identification. The length of the boehmite nanofibers was found to be more than 10 mum with a crystalline lattice structure. The mechanism of formation of the boehmite nanofibers included the preferential growth along the longitudinal axis due to interaction between the solvent molecules and the surface OH- groups of hydrogen bonds. It is also suggested that the boehmite nanofibers may have formed due to the inherent instability of the planar structure of the boehmite lattice. The diameter of the gamma-alumina nanorods was found to be less than 10 nm with a varying length in the range of 50-200 nm. Boehmite to gamma-Al2O3 transformation was attributed to the loss of water molecules by internal condensation of protons and hydroxyl ions.     

Effect of boehmite nanorods on the properties of glycidoxypropyl-trimethoxysilane (GPTS) hybrid coatings

AlOOH boehmite nanorods, synthesized by a solid-based process, were incorporated into a sol–gel coating in which GPTS was used as a precursor. Transparent composite coatings with nanorod content up to 40 wt% were obtained by spin coating the sol–gel mixture on glass substrates. Nanorods in the coating were found be aligned parallel to the substrate surface. Mechanical properties, such as modulus and hardness of the nanorod filled coating, were slightly lower than coatings of the same composition but filled with commercially available nanosized boehmite particles. However, crack toughness was greatly improved, as supported by nanoindentation test results. The improvement in crack toughness was attributed to the high aspect ratio of the rigid nanorods, in addition to the fact that the nanorods were aligned within the composite parallel to the surface.     

Hydrothermal preparation of boehmite nanorods by selective adsorption of sulfate

A facile hydrothermal method was developed to synthesize boehmite nanorods with a length of 50-2000 nm, a diameter of 6-20 nm, and a preferential growth along [100] by treating the Al(OH)(3) gel in acidified sulfate solutions at 240 degrees C. Studies on the hydrothermal treatment of Al(OH)(3) gel in sulfate solutions showed that the morphology and the composition of the hydrothermal products were connected with the sulfate concentration and the pH of the hydrothermal solution. The aspect ratio of the boehmite nanorods increased to 300 as the initial H(2)SO(4) concentration increased to 0.043 mol x L(-1), whereas boehmite nanorods and (H(3)O)Al(3)(SO(4))(2)(OH)(6) cubic particles coexisted in the case of the initial H(2)SO(4) concentration > or = 0.054 mol x L (-1). Sole boehmite nanoflakes with a diameter of about 50 nm were formed under alkaline conditions (pH 10.5) despite the existence of the sulfate. The chemical and Raman analyses indicated that SO(4)(2-) in acidified solutions adsorbed on the boehmite surface via H-bonds. On the basis of the above results, the growth of boehmite along the [100] direction was attributed to the selective adsorption of SO(4) (2-) on the (010) and (001) planes of boehmite.     

簇形和花形CdS纳米结构的自组装及光催化性能

通过可控溶剂热法, 利用乙二胺作为模板制备出簇形和花形硫化镉(CdS)纳米结构. 通过X射线衍射(XRD)和扫描电镜(SEM)观测其形貌和结构特征. XRD谱线显示, 簇形CdS为六方晶体结构, 而花形CdS纳米结构则为立方晶体. 实验结果表明, 整个自组装过程是由成核以及成核竞争引起的不同生长过程所组成的, 并且乙二胺的模板功能起了重要的作用. 通过不同时间和温度的实验, 深入探讨了簇形和花形CdS纳米结构的自组装机理. 室温光致发光谱(PL)显示这两种纳米结构在433 nm和565 nm附近有较强的发射峰, 分别对应激子发射和表面缺陷发光. 通过Brunauer-Emmett-Teller (BET)方法测试其比表面积. 研究了高压汞灯照射下, 簇形和花形CdS纳米结构在甲基橙(MeO)溶液中的光催化性能. 结果显示, 由于其较大的比表面积, 花形CdS纳米结构的光催化性能要远优于其它CdS材料.     

Template-free preparation of bunches of aligned boehmite nanowires

A simple method based on a hydrothermal process using alkali salts as mineralizers is proposed for the synthesis of aligned bunches of boehmite (gamma-AlOOH) nanowires without a template's assistance. Most bunches of aligned boehmite nanowires are constructed by two separated shorter bundles with widths of 700 to approximately 800 nm and lengths of about 1 microm. XRD patterns, FTIR spectra, and SEM and TEM images were used to characterize the products. The specific surface area and pore-size distribution of the obtained product as determined by gas-sorption measurements show that the boehmite bundles possess a high BET surface area and porosity properties. The importance of adding Na2B4O7 salts for the formation of bundle morphologies has been discussed.     

Assembled Vitamin B2 Nanocrystals with Optical Waveguiding and Photosensitizing Properties for Potential Biomedical Application

Great success has been achieved in recent years in the development of synthetic or assembled nanobiomaterials. Among these, biomolecule‐based nanoarchitectures with special optical property are of particular interest. Here, we demonstrate that vitamin B₂ nanocrystals assembled as nanorods can be obtained with precise control. Excitingly, such one‐dimensional nanostructures not only exhibit intrinsic optical waveguiding properties but also the ability to sensitize oxygen to produce reactive oxygen species. With these properties, we applied the obtained vitamin B₂ nanorods under remotely localized light illumination into single tumour cells in vitro for anticancer photodynamic therapy. Further, vitamin B₂ nanorods were explored for in vivo photodynamic therapy by using a tumour model. With such bionanostructures, new features and functions of vitamin B₂ and its derivatives have been developed.     

Optical and photocatalytic properties of single crystalline ZnO at the air-liquid interface by an aminolytic reaction

Crystalline flowerlike ZnO was synthesized by an aminolytic reaction at the air-liquid interface in an aqueous media at an alkaline pH. A thin visible film was formed at the air-liquid interface by self-assembly of flowerlike ZnO. Diffraction studies show rearrangement of the single crystalline units at the air-liquid interface leading to the formation of nanobelts. These nanobelts overlap systematically to form petals of the flowerlike structure; individual petals get curved with time. Each nanobelt is found to be single crystalline and can be indexed as the hexagonal ZnO phase. The organic product formed in the aminolytic reaction and dissolution-reprecipitation mechanism is the driving force for the formation of flowerlike ZnO at the air-liquid interface. A clear relationship between the surface, photocatalytic, and photoluminescent properties of ZnO is observed. The flowerlike structure exhibits a blue shift (3.56 eV) in the band emission as compared to bulk ZnO (3.37 eV). The photodegradation of methylene blue over the flowerlike ZnO catalyst formed at the air-liquid interface and in the sediments shows enhanced photocatalytic activity. The sub-bands formed due to surface defects facilitate separation of charge carriers increasing their lifetime, leading to enhanced photocatalytic activity of flowerlike ZnO.     

Synthesis and characterization of mesoporous ceria with hierarchical nanoarchitecture controlled by amino acids

In this work, we report the synthesis and characterization of mesoporous ceria with hierarchical nanoarchitectures controlled by amino acids. During the synthesis procedure, cerium oxalate precipitate was treated hydrothermally with different amino acids as crystallization modifiers, and hierarchically structured cerium oxalate precursors were obtained. Ceria can be produced after thermal decomposition of the cerium oxalate precursors. Structure and properties of the product were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, N2 adsorption analysis, and X-ray photoelectron spectroscopy (XPS) methods. The results indicate that the mesoporous ceria with hierarchical nanoarchitectures are composed of nanosized ceria crystallites as building units and possess high surface area and high concentration of oxygen vacancy. Depending on different amino acids as the crystallization modifiers, the ceria exhibit different morphologies, such as dendritic aggregation of rods, dumbbells of nanorod arrays, or aggregated spheres. It is proposed that both the type of functional side groups and the length of the side groups of the amino acids influence the morphologies of the ceria. Meanwhile, the solvent and hydrothermal treatment temperatures also play important roles in the morphological control. The method reported in this work would be regarded as a general way to fabricate mesoporous metal oxides with hierarchical nanoarchitectures.     

Boehmite nanorod‐reinforced‐polyethylenes and ethylene/1‐octene thermoplastic elastomer nanocomposites prepared by in situ olefin polymerization and melt compounding

Nanocomposites of polyethylene (HDPE) and poly(ethylene‐co‐1‐octene) thermoplastic elastomers, both containing boehmites with variable sizes, shapes, and aspect ratios (1–20), were prepared by means of in situ olefin polymerization and melt compounding. The in situ olefin polymerization in the presence of boehmite nanorods afforded nanocomposites containing 4–8 wt % of boehmite. In an alternative process, the in situ olefin polymerization was used to produce polyolefins with high boehmite content of 50 wt % as masterbatches for polyolefin melt compounding with ethylene homo‐ and copolymers. The addition of the boehmite nanofillers improved the stiffness without sacrificing high elongation at break. The stiffness, as expressed by Young's modulus, increased with increasing boehmite aspect ratio. In case of thermoplastic elastomer nanocomposites the increase of stiffness was accompanied by a simultaneous increase of elongation at break. According to transmission electron microscopy (TEM), fine dispersion of the polar boehmite nanorods and nanoplatelets within the nonpolar hydrocarbon polymer matrix was obtained without requiring the addition of special dispersing agents or functionalized polyolefin compatibilizers. The comparison of melt compounding of polyethylene with boehmites or polyethylene/boehmite masterbatches revealed that compounding of masterbatches prepared by in situ polymerization filling afforded much finer and more uniform nanoboehmite dispersions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2755–2765, 2008     

Stability electrochemical performance of self-assembled hierarchical MnCO<Subscript>3</Subscript>/MWCNT nanocomposite as anode material for lithium-ion batteries

The self-assembled hierarchical MnCO₃/MWCNT nanoarchitectures are prepared by a facile solvothermal method and used as anode material for lithium-ion batteries. The results of SEM and TEM show that the hierarchical nanorods are made of the primary MnCO₃ nanocrystals. The hierarchical nanorods MnCO₃ are heterogeneously distributed among retiform MWCNTs. Those MnCO₃/MWCNT nanoarchitectures are able to buffer the physical aggregation of the MnCO₃ nanorods and volume expansion of MnCO₃ in the charge/discharge process. The self-assembled hierarchical MnCO₃/MWCNT nanocomposite delivers a reversible capacity of 704 mAh g^?1 after 110 cycles at a current density of 100 mA g^?1. The excellent electrochemical performance is attributed to the self-assembled hierarchical MnCO₃/MWCNT nanoarchitectures and the high conductivity of MWCNTs.     

Preparation and Optoelectronic Property of a SnO2/CdS Nanocomposite Based on the Flowerlike Clusters of SnO2 Nanorods

A SnO₂/CdS nanocomposite based on the flowerlike clusters of SnO₂ nanorods was prepared and characterized with x-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and EDX analysis. The SEM and TEM images show the nanocomposite is composed of CdS nanoparticles and flowerlike clusters of SnO₂ nanorods. The UV–vis spectrum of the nanocomposite displays a new absorption band in the region of 350 to 530 nm, compared with that of the flowerlike clusters of SnO₂ nanorods. The measurement of optoelectronic property indicates that the photoresponse of the composite is extended into the visible region and the incident photon-to-current conversion efficiency (IPCE) of the composite is up to 6.5 in the range of 400 to 440 nm. These phenomena ought to be ascribed to the special nanostructure of the SnO₂/CdS composite obtained.     

级次纳米结构材料及其液相合成

级次纳米结构材料因其新颖的结构,独特的化学、物理性质,以及形貌和尺寸对这些性质极大地影响,使得它在光、电、磁等方面的性质更加丰富, 为实现由下到上构建纳米器件提供了坚实的基础。由此级次纳米结构材料引起化学家和材料学家的极大兴趣, 成为纳米材料化学领域中引人注目的研究方向之一。本文综述了近年来国内外级次纳米结构材料的最新研究进展,重点介绍了介孔材料、具有级次结构的空心球、气凝胶和其他典型的级次纳米结构,归纳了级次纳米结构制备中的各种液相合成方法及其特点,讨论了级次纳米结构的合成机制及各种影响因素,并在此基础上对级次纳米结构材料在一些领域的应用前景进行了展望。     

Spontaneous self-assembly of cerium oxide nanoparticles to nanorods through supraaggregate formation

Self-assembly of cerium oxide nanoparticles to nanorods is reported. Such nanorods have an aspect ratio of 6 with a diameter of approximately 40 nm. The formation of cylindrical supraaggregates and their subsequent growth by preferential assembling of ceria nanocrystallites along the longitudinal direction was proposed to be the probable mechanism of spontaneous self-assembly of nanorods. The supraaggregate formation was facilitated by influencing the local curvature of the micelle surface in the presence of nitrate ions as a precursor solution. The nanorods were characterized using high-resolution transmission electron microscopy with energy dispersive spectroscopy and selected area electron diffraction for their morphology, chemistry, and crystal structure.     

原位透射电子显微镜观察电荷驱动的氧化物纳米颗粒水中自组装

以四氧化三钴Co_3O_4纳米棒为研究对象,我们利用液体环境透射电子显微镜,原位观察了四氧化三钴纳米棒在水中的自组装过程。研究发现在电子束辐照的水环境下,四氧化三钴纳米棒的晶面存在互补式自组装现象。随着纳米棒之间的距离越来越近,纳米棒之间的相对运动速率逐渐增加,纳米棒之间的相互作用力逐渐增加。通过进一步分析纳米棒的形貌发现,纳米棒的暴露晶面大多数为{100}、{110}以及{111}晶面,而Co_3O_4属于极性氧化物,这些晶面往往会带有一定的电荷。在液体环境下,正是由于这些易暴露面都带有不同大小的电荷,在晶面电荷的驱动下,电荷属性相反的四氧化三钴纳米棒会互相吸引,形貌结构上进行互补,实现快速驱动的纳米棒之间自组装。     

Study on the synthesis of poly(diglycidyl maleate-co-stearyl methacrylate) and morphology conversion of their self-assembly systems

A novel polymer of poly(diglycidyl maleate-co-stearyl methacrylate) (P(DGMA-co-SMA)) was synthesized by reaction between poly(maleic anhydride-co-stearyl methacrylate) (P(MA-co-SMA)) and epichlorohydrin. The self-assembly behavior of the resultant copolymer was investigated. It was found that the spheral aggregates could converse to nanorods after being aged for 2.5 days and nanolines composed of the nanorods were obtained after being aged for an additional 5.5 days. The mechanism of their self-assembly behavior and morphology conversion of self-assembly systems is discussed.     

Novel self-assembled MgO nanosheet and its precursors

A novel self-assembled microstructure, nestlike Mg(5)(CO(3))(4)(OH)(2).4H(2)O spheres, is formed by a self-assembly of nanosheets in the hydrothermal process. MgO with the similar morphology can be obtained by calcination of nestlike Mg(5)(CO(3))(4)(OH)(2).4H(2)O. MgO precursors with a uniform, ellipsoid-shaped, and smooth surface or flowerlike architecture, built by individual thin sheets, can be well-obtained by carefully controlling pH values of the initial reaction solution. The nestlike MgO exhibits a unique geometrical shape; its surface is composed of uniform MgO nanosheets. The unique MgO microstructure with high surface areas may possess promising applications as the sorbent for chemisorption and destructive adsorption of various pollutants.     

Boehmite silica sulfuric acid: as a new acidic material and reusable heterogeneous nanocatalyst for the various organic oxidation reactions

In this research, project boehmite silica sulfuric acid (Boehmite-SSA) has been applied as new acidic porous catalyst for the selective oxidation of sulfides to sulfoxides and oxidative coupling of thiols to corresponding disulfides using hydrogen peroxide as oxidizing agent. The products have been obtained in short reaction times and high yields. Boehmite nanoparticles was prepared, coated by silica and then reacted with chlorosulfuric acid to obtain Boehmite-SSA. This catalyst was characterized by FT-IR, TGA/DTA, XRD, TEM, SEM, EDS and BET techniques. BET curve of boehmite nanoparticles identified as a typical type IV isotherm (definition by IUPAC), which are the characteristics of mesoporous material. Nitrogen adsorption/desorption measurement indicated that boehmite nanoparticles had BET surface area of about 122.8 m²/g. The catalyst was easily separated and reused for the several runs without significant loss of its catalytic efficiency.     

Surface tension and fluid flow driven self-assembly of ordered ZnO nanorod films for high-performance field effect transistors

Colloidal nanorods of inorganic semiconductors are of interest for a range of optoelectronic devices. The ability to self-assemble these materials into ordered arrays by solution-processing techniques is crucial for achieving adequate device performance. Here we show that uniform ZnO nanorod films with defined nanorod alignment can be solution-deposited over large areas by controlling the surface energy of the nanorods through the choice of suitable ligands and by the fluid flow direction during growth. ZnO nanorods with long carbon chain ligands exhibit a smaller surface free energy than those with short carbon chain ligands resulting in better in-plane alignment and large domain sizes up to dozens of micrometers in spin-coated films. A model is presented to rationalize the observed self-assembly behavior. It is based on the formation of a lyotropic liquid crystalline phase on the surface of the liquid film which is facilitated by enhanced segregation of nanorods with low surface tension to the surface. Alignment of the nanorods is controlled by radial and vertical liquid flows in the drying solution. The ability to control the orientation of the nanorods and to achieve large domain size results in significant device performance improvement. Field-effect transistors with mobilities of up to 1.2-1.4 cm2/V.s are demonstrated in spin-coated, in-plane aligned ZnO nanorod films subject to postdeposition hydrothermal growth.