基于AuCl(油胺)复合物合成形貌可控的金纳米结构

简要综述了使用一价金复合物AuCl(油胺)作为前驱物合成形貌可控的金纳米结构的相关工作. 通过改变有机溶剂、添加异质金属纳米粒子及控制反应温度等手段, 成功合成出球形的金纳米粒子(平均直径12.7 nm)、超细金纳米线(平均直径1.8 nm)及超细金纳米棒(平均直径2 nm); 并通过牺牲磁性纳米粒子模板的方法合成出枝状金纳米结构. 除了对合成方法和过程的介绍, 还简要讨论了每种纳米结构的形成机制.     

Electrophoretic co-deposition of biomimetic nanoplatelet–polyelectrolyte composites

Bio-inspired assembly of platelet particles and polyelectrolytes into ordered layered composites is of great technological importance in developing light-weight reinforced materials, separation membranes, and gas-barrier coatings. Unfortunately, the broadly applied layer-by-layer self-assembly technology is tedious in generating thick multilayered coatings. Here, we report a rapid and scalable cathodic electrophoretic co-deposition technology that enables simultaneous assembly of positively charged gibbsite nanoplatelets and cationic polyelectrolytes into ordered multilayers in a single step. The resulting nanocomposites have similar organic/inorganic weight ratio and ordered brick-and-mortar nanostructure as natural nacres. Nanoindentation tests show that the electrodeposited nanocomposites exhibit similar hardness and reduced modulus as those of pure gibbsite coatings.     

蝴蝶翅膀表面水滴各向异性黏附性质

采用扫描电子显微镜(SEM)观察了双带闪蝶(Morpho Achilles)翅膀表面的微观形貌, 通过样品的表观接触角表征了其浸润性, 采用高敏感性微电力学天平比较了水滴在蝴蝶翅膀表面不同方向运动时受到的黏附力. 实验结果表明, 水滴沿着干燥的蝴蝶翅膀鳞片堆叠方向运动时受到的黏附力要明显小于其它方向运动时受到的力, 且受力较稳定; 当蝴蝶翅膀被水滴浸润后, 水滴沿着湿润的蝴蝶翅膀鳞片堆叠方向运动时受到的黏附力接近甚至大于逆着鳞片堆叠方向运动时受到的力.     

Electrostatically Controlled Nematic and Smectic Assembly of Gold Nanorods

The assembly of gold nanorods(GNRs) into different liquid crystalline structures can be controlled by tuning their surface electric potential. After mildly removing excess surfactants in the GNRs solution, the electrostatic interaction between GNRs can be tuned by adjusting counter ion concentration. Specifically, nematic and smectic structures formed after solvent evaporation at low and high bromide concentrations, respectively. These results could be helpful for fabricating anisotropy enabled devices composed of metal and semiconductor nanorods.     

Characterization of Nanostructures in Acellular Cementum of Human Tooth Roots

Determining the microstructure in human cementum might help us design new kinds of replacement materials for the treatment of teeth injury and disease. The authors characterized the nanostructures in the cementum of health human teeth via scanning electronic microscopy(SEM). It was found that the acellular cementum is mainly composed of two kinds of nanostructures―inorganic nanoparticles and organic nanofibers. And the inorganic nanoparticles show a tendency to arrange along the organic nanofibers. Based on the micro-molding in capillary strategy, the distribution of organic component in acellular cementum was copied with UV curable resin. After removing the inorganic nanoparticles by acid etching, many isolated spindle shape nanopores were left in polymer, which su- ggested that the inorganic nanoparticles should have been isolated by the organic component in cementum, and should be oval or nanosheet in shape. We hope the present work could provide reference for the biomimetic preparation of tissue engineering materials, and help us design new types of tooth implant.     

Synthesis,structural, dielectric and magnetic properties of spinel structure of Ca2+ substitute in Cobalt ferrites (Co1−xCaxFe2O4)

Non magnetic material Ca²⁺ as a substitute in Cobalt ferrite (Co_1?xCa_xFe₂O₄x?=?0.00, 0.05, 0.10 & 0.15) is prepared by self auto combustion method. The synthesized samples were carried out for various characterizations such as X-ray diffraction, Field emission scanning electron microscope (FE-SEM), Dielectric measurement and Magnetic property. X-ray diffraction reveals the values of crystalline size, lattice parameter and x-ray density by using the standard formula. The saturation magnetization (M_s) decreases from 63.92 to 43.17 emu/g for x?=?0.00 to 0.15 and the coercivity (H_c) increases gradually from 819.85 to 1312.32?Oe with the increase in Ca²⁺ concentration. The dielectric properties of synthesized nano materials were carried out at room temperature. The dielectric parameters such as tangent loss, Cole–Cole plot (Impedance, Modulus), and AC Conductivity were determined for various Ca²⁺ concentration. The frequency dependent dielectric dispersion behaviour of all the samples can be explained by the Maxwell–Wagner two-layer model along with Koop's phenomenological theory. As a result, Ca²⁺ substituted Cobalt ferrite is enhanced with their dielectric and magnetic property which is suitable for a memory device, recording media application and high frequency device.     

A simple synthesis of large-scale SiC–SiO2 nanocables by using thermal decomposition of methanol: Structure, FTIR, Raman and PL characterization

Large-scale SiC nanocables were synthesized on a Ni(NO₃)₂-catalyzed Si substrate by using a simple and cheap method based on thermal decomposition of methanol. Based on X-ray diffraction and high-magnification transmission electron microscopy, the as-grown nanocables consisted of crystalline SiC cores and amorphous SiO₂ shells. The diameters of SiC cores were 5.7–10 nm and the thicknesses of SiO₂ shells were 9–20 nm. Dividing of nanocables was observed and its origin was investigated. An asymmetric feature of SiC TO band with a shoulder at the high-frequency side was attributed to the contribution of SiC TO mode. The nanocables displayed strong violet–blue emission. A possible growth mechanism was proposed.     

Studies on the formation of hierarchical zeolite T aggregates with well-defined morphology in different template systems

In this paper, the disk-like and pumpkin-like hierarchical zeolite T aggregates consisted of primary nano-grains have been hydrothermally synthesized with and without the aid of the second template. The first template is used with tetramethylammonium hydroxide (TMAOH) and the second template is used with triethanolamine (TEA) or polyving akohol (PVA). A combination of characterization techniques, including XRD, SEM, TEM and N₂ adsorption–desorption to examine the crystal crystallinity, morphology and surface properties of hierarchical zeolite T aggregates. In the single-template preparation process, the two-step varying-temperature treatment has been used to improve the meso-porosity of zeolite T aggregates. In the double-template preparation process, the amounts of PVA or TEA on the crystallinity, morphology and meso-porosity of zeolite T aggregates have been studied. It has been proved that the interstitial voids between the primary grains of aggregates are the origin of additional mesopores of samples. The micro- and meso-porosities of samples prepared with and without the second template have been contrasted in detail at last. In particular, the sample synthesized with the addition of PVA presents a hierarchical pore structure with the highest S_ext value of 122 m²/g and V_meso value of 0.255 cm³/g.     

导电聚合物的纳米结构及其在生物医学领域的应用

由于表面效应、小尺寸效应和量子效应,使纳米结构的导电聚合物材料与传统聚合物材料相比,显示出更优越的性能。基于神经组织对电场和电刺激敏感性,使得导电聚合物纳米材料在生物医学应用方面很有前景。本文综述了纳米结构的导电聚合物的合成方法,及其在生物医学领域的应用。合成方法主要关注于硬模板法、软模板法和无模板自组装法,以及这些方法中导电聚合物纳米结构的形成机理。总结了具有纳米结构的导电聚合物,如纳米颗粒、纳米纤维和纳米管等作为神经电极涂层材料和生物传感器等方面的应用。     

Mesoporous cobalt oxide for largely improved lithium storage properties

We report the microstructure,application for lithium-ion batteries of mesoporous Co3O4 prepared by modified KIT-6 template method.The sample was characterized by XRD,TEM,HRTEM and nitrogen adsorption.Their electrochemical behaviors as electrode reactants for lithium ion batteries were evaluated by cyclic voltammograms and static charge-discharge.A direct comparison of electrochemical behaviors between mesoporous nanostructure and bulk reflects interesting "nanostructure effect",which is reasonably discussed in terms of how the 3D nanostructures of Co3O4 materials function in tuning their electrochemistry.The results demonstrate that further improvement of electrochemical performance in transition metal-oxide-based anode materials can be realized via the design of multiporous nanostructured materials.