Polyvinylpyrrolidone-assisted ultrasonic synthesis of SnO nanosheets and their use as conformal templates for tin dioxide nanostructures

Single crystalline SnO nanosheets with exposed {001} facets have been prepared by an ultrasonic aqueous synthesis in the presence of polyvinylpyrrolidone, which hinders the spontaneous formation of the truncated bipyramidal SnO microcrystals and exfoliate them into layer-by-layer hierarchical structures and further into separate SnO nanosheets. The SnO nanosheets have been used as conformal sacrificial templates converted into polycrystalline SnO(2), as well as layered SnO/SnO(2) nanostructures, by calcination in air. The concept of fabrication of two-dimensional tin oxide nanostructures demonstrated here may be relevant for the crystal design of layered materials, in general.     

Facile synthesis of hydrophobic fluoroalkyl functionalized silsesquioxane nanostructures

New fluorinated polyhedral oligomeric silsesquioxane (F-POSS) structures possessing a high degree of hydrophobicity have been prepared via a facile corner-capping methodology.     

Facile synthesis of anisotropic Au@SiO2 core-shell nanostructures

Anisotropic Au@SiO(2) core-shell nanostructures have been fabricated from CTABr-stabilized Au nanoparticles with a facile synthesis involving a single growth solution. This procedure circumvents tedious surface modification steps and allows for the SiO(2) shell thickness to be tuned from 5 to 20 nm by modulating the nanoparticle number density and concentration of silica precursor.     

Controlled synthesis and enhanced catalytic and gas-sensing properties of tin dioxide nanoparticles with exposed high-energy facets

A morphology evolution of SnO(2) nanoparticles from low-energy facets (i.e., {101} and {110}) to high-energy facets (i.e., {111}) was achieved in a basic environment. In the proposed synthetic method, octahedral SnO(2) nanoparticles enclosed by high-energy {111} facets were successfully synthesized for the first time, and tetramethylammonium hydroxide was found to be crucial for the control of exposed facets. Furthermore, our experiments demonstrated that the SnO(2) nanoparticles with exposed high-energy facets, such as {221} or {111}, exhibited enhanced catalytic activity for the oxidation of CO and enhanced gas-sensing properties due to their high chemical activity, which results from unsaturated coordination of surface atoms, superior to that of low-energy facets. These results effectively demonstrate the significance of research into improving the physical and chemical properties of materials by tailoring exposed facets of nanomaterials.     

Mechanochemical synthesis of nanosize tin dioxide powders

Structural parameters, dispersity, morphology, and magnetic properties of a tin dioxide-magnetite nanosize composite material mechanochemically synthesized from salt systems were studied. The possibility of using the composite nanopowder as a sorbent for nucleic acids was analyzed.     

Facile synthesis of biphenyl-fused BODIPY and its property

A biphenyl-fused BODIPY was synthesized through a facile oxidative cyclization of peripheral aryl-substituents at the β-position of the BODIPY unit. The extended π-system of the fused BODIPY induces near-infrared (NIR) absorption and strong π-π interactions in the solid state. These features are beneficial for the application of the dye as a functional material. The biphenyl-fused BODIPY dye was demonstrated to exhibit photocurrent conversion ability on the basis of its n-type semiconducting property.     

Controllable synthesis and property of graphene-based magnetic metal nanostructures

A facile and effective solution phase reduction method was developed to synthesize graphene-based magnetic metal nanocomposites. Metals (Co, and Ni) or alloys (Fe₅₁Co₄₉, Fe₄₈Ni₅₂, Ni₄₉Co₅₁, Co₅₁Cu₄₉, and Ni₅₂Cu₄₈)/reduced graphene oxide (RGO) nanocomposites were successfully prepared by reduction of the corresponding aqueous metal ions and ethylenediamine (EDA)–graphene oxide (GO) with hydrazine hydrate at 353 K for 1 h under N₂ atmosphere. The effects of synthetic parameters such as metal ions concentration, adding sequence of NaOH and N₂H₄·H₂O, linkage agent and reaction time on the formation of nanocomposites were investigated. The experimental results showed that using ethylenediamine and adding sequence played critical roles in the formation of metals or alloys/RGO nanocomposites. Magnetic hysteresis measurements revealed that the as-synthesized metals or alloys in nanocomposites showed excellent soft magnetic behavior with enhanced saturation magnetization, and could have promising applications in biotechnology, catalysis, and magnetic storage devices.     

Facile synthesis of tin oxide nanoparticles stabilized by dendritic polymers

Tin(IV) oxide nanoparticles were synthesized via the reaction of carbon dioxide with stannate ions immobilized by dendritic polymers. For PAMAM and PPI dendrimer hosts, resultant nanoparticle diameters were 2.5-3 nm; 3-3.5 nm nanoparticles resulted from use of a poly(ethyleneimine) hyperbranched polymer. Our conditions represent the only precedent for SnO2 nanoparticulate growth using dendritic architectures, as well as a novel application for CO2 as a reactive gas for the controlled growth of metal oxide nanoparticles.     

Facile synthesis of palladium nanoparticles supported on urea-based porous organic polymers and its catalytic properties in Suzuki-Miyaura coupling

By using urea linked porous organic polymers as template, a new nano palladium catalyst with low Pd loading can be easily prepared (1.0 wt% Pd only). Although such less amount of Pd was contained in this new catalyst, it is still an effective catalyst for the Suzuki-Miyaura coupling of aryl iodines and aryl boric acids, affording biphenyl products in excellent yields with outstandingly enhanced turnover numbers (up to 10,536) under green solvent (water).     

Green synthesis of nanowire-like Pt nanostructures and their catalytic properties

We reported a simple and effective green chemistry route for facile synthesis of nanowire-like Pt nanostructures at one step. In the reaction, dextran acted as a reductive agent as well as a protective agent for the synthesis of Pt nanostructures. Simple mixing of precursor aqueous solutions of dextran and K₂PtCl₄ at 80 °C could result in spontaneous formation of the Pt nanostructures. Optimization of the experiment condition could yield nanowire-like Pt nanostructures at 23:1 molar ratio of the dextran repeat unit to K₂PtCl₄. Transmission electron microscopy results revealed that as-prepared nanowire-like Pt nanostructures consisted of individual Pt nanoparticles with the size range from 1.7 to 2.5 nm. Dynamic light scattering analysis indicated that as-prepared nanowire-like nanostructures have already formed in solution. The as-prepared nanowire-like Pt nanostructures were further characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. In addition, the ratio dependence and temperature dependence of this reaction have also been investigated. The as-prepared nanowire-like Pt nanostructures can be immobilized on glassy carbon electrodes using an electrochemical coupling strategy, and the resulting nanowire-like Pt nanostructures modified film exhibited an excellent electrocatalytic activity for the reduction of oxygen and the oxidation of NADH.     

辐射状钯纳米花的可控合成及其电催化性能的研究

水体系中,以十六烷基三甲基溴化铵(CTAB)和L-精氨酸为表面活性剂,抗坏血酸还原PdCl42-,制得了直径范围在50~80 nm之间的辐射状钯纳米花.实验表明,CTAB和L-精氨酸对辐射状钯纳米花的形成起着协同作用.此外,还研究了辐射状钯纳米花对甲酸氧化的电催化活性.在0.5 mol/L H2SO4+0.5 mol/L HCOOH溶液中的循环伏安结果表明,辐射状钯纳米花修饰电极在酸性溶液中电催化氧化甲酸的峰电流密度约为101 mA/mg,明显优于实心钯纳米粒子修饰的电极(峰电流密度为50 mA/mg),且表现出较高的稳定性.     

Copper oxide nanostructures: Controlled synthesis and their catalytic performance

Oval-plate-like, sphere-like, bundle-like and plate-like copper oxide (CuO) nanostructures were prepared by hydrothermal method using Cu(CH₃COO)₂·H₂O and NaOH as the reagents in the absence of any surfactants or templates. The morphology and structure of CuO nanostructures could be easily tailored by adjusting the amount of NaOH. The catalytic activity of the as-prepared CuO nanostructures was demonstrated by catalytic oxidation of methylene blue (MB) in presence of hydrogen peroxide (H₂O₂). The oval-plate-like CuO exhibited better catalytic activity and which was mainly attributed to the larger specific surface area.     

An electron microscope study of tin dioxide and antimony-doped tin dioxide

Crystals of tin dioxide, SnO₂, have been grown pure or doped with a few percent of antimony using vapor growth methods in order to investigate the microstructures of reduced and oxidized SnO₂. They were examined by X-ray diffraction and by optical and electron microscopy. SnO₂ crystals were found to contain few faults, but the antimony-doped crystals were extensively twinned in some regions. Reduction of SnO₂ crystals to yield CS phases was unsuccessful. These results are discussed in terms of the known crystal chemistry of the oxides involved.     

Facile synthesis of ternary AgInS2 nanowires and their self-assembly of fingerprint-like nanostructures

Nanowires (NWs) and self-assemble nanostructures made of chalcogenide semiconductor nanocrystals (NCs) are of great interests to the fundamental studies and practical applications. In this study, we reported a seeded-mediated growth of AgInS₂ NWs and their intriguing self-assembly nanostructures with fingerprint-like shape. The key to the formation and self-assembly of AgInS₂ NWs was the presence of In-S species that was a type of molecular metal chalcogenide complexes, serving as specific inorganic ligands for the growth of NWs and cross-linker molecules for the self-assembly of fingerprint-like nanostructures. Systematic studies were carried out to investigate the reaction factors, including the thermodynamics, amount and type of In precursors, and 1-dodecanethiol usage, to the success of the desired products.     

Facile synthesis of optically functional,highly organized nanostructures: dye-surfactant complexes

Multiply charged dye molecules can be precipitated from water by complexation with oppositely charged surfactants. It is shown that this complex formation occurs with 1:1 stoichiometry in a highly cooperative fashion. The resulting solids show either a gel-like or a supramolecular fibrillar morphology with a very high degree of order on the nanoscale, as evidenced by small-angle X-ray scattering and pleochroic behavior under plane-polarized light.     

Facile synthesis of biomass-derived hierarchical porous carbon microbeads for supercapacitors

Using the facile method of solvent evaporation, the leonardite fulvic acids (LFA)-based porous carbon microbeads (PCM) have been successfully prepared at ambient pressure, followed by carbonization and KOH activation (a low mass ratio alkali/LFA = 1.5) in an inert atmosphere. The effects of KOH treatment on pore structures and the formation mechanism of the PCM were discussed. The results showed that the sample exhibited remarkable improvement in textural properties. The activated carbon microbeads had high surface area (2269 m² g^?1), large pore volume (1.97 cm³ g^?1), and displayed excellent capacitive performances, compared with carbon powder. The porous carbon material electrodes with the “porous core structure” behaved superiorly at a specific capacitance of 320 F g^?1 at a current density of 0.05 A g^?1 in 6 M KOH electrolyte, which could still remain 193 F g^?1 when the current density increased to 100 A g^?1. Remarkably, in the 1 M TEABF₄/PC electrolyte, the PCM samples could reach 156 F g^?1 at 0.05 A g^?1, possess an outstanding energy density of 39.50 Wh kg^?1, and maintain at 22.05 Wh kg^?1 even when the power density rose up to 5880 W kg^?1. The balance of structural characteristic and high performance makes the porous carbon microbeads a competitive and promising supercapacitor electrode material.     

金属纳米结构的氧化刻蚀调控与催化性能优化

金属纳米结构的可控合成,对其性能优化和高效应用至为关键．氧化刻蚀作为金属纳米晶可控合成中的新兴有效调控手段之一,受到越来越多的关注．本文以本课题组近期的研究工作为例,说明了氧化刻蚀对金属纳米晶的形貌、尺寸、结构及组成等合成参数的有效调控作用．由此总结认为,在金属纳米晶可控合成的一般过程,尤其是成核和生长过程中,氧化刻蚀的本质是有效调控“两个速率”和“两个力学”,即减缓原子的生成速率与晶种的形成速率、选择性接受反应热力学和反应动力学的控制作用．我们将通过氧化刻蚀法调控合成得到的具有独特结构的Pd,Pt纳米晶,用于氧活化和电催化这两个重要的催化体系,获得了理想的催化结果,表明氧化刻蚀在金属纳米晶的功能改性和应用拓展方面,具有令人称奇的广阔应用前景．     

Topochemical synthesis of cobalt oxide-based porous nanostructures for high-performance lithium-ion batteries

Two kinds of topochemical conversion routes from cobalt hydroxide precursors to cobalt oxide-based porous nanostructures are presented: pyrolysis in air and hydrothermal treatment by the Kirkendall diffusion effect. These cobalt hydroxide precursors were synthesized by a simple hydrothermal approach with sodium acetate as mineralizer at 200 °C. Detailed proof indicates that the process of cobalt hydroxide precursor growth is dominated by a nucleation, dissolution, renucleation, growth, and exfoliation mechanism. By the topochemical conversion processes several Co(3)O(4) nanostructures, such as cobalt oxide-coated cobalt hydroxide carbonate nanowires, cobalt oxide nanotubes, hollow cobalt oxide spheres, and porous cobalt oxide nanowires, have been synthesized. The obtained Co(3)O(4) nanostructures have also been evaluated as the anode materials in lithium-ion batteries. It was found that the as-prepared Co(3)O(4) nanostructures exhibited high reversible capacity and good cycle performance due to their porous structure and small size.