Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes

The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g^?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g^?1 for the CNOs/Ppy bilayer (electrochemical deposition).     

Tips and Tricks for the Surface Engineering of Well-Ordered Morphologically Driven Silver-Based Nanomaterials

Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface-regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted.     

Solvothermal synthesis of TiO2: anatase nanocrystals and rutile nanofibres from TiCl4 in acetone

This work reports a new synthetic approach for single‐phase TiO₂ nanomaterials by solvothermal treatment of titanium tetrachloride in acetone at 80–110 °C. Small, uniform, and yet size‐tunable (5–10 nm) anatase titania nanocrystallites were obtained using a low concentration of TiCl₄ in acetone (i.e., at molar ratios of TiCl₄/acetone ≤ 1:15) in the temperature range of 80–110 °C, while rutile nanofibers were synthesized using a high concentration of TiCl₄ (e.g., TiCl₄/acetone = 1:10) at 110 °C. Copyright © 2007 John Wiley & Sons, Ltd.     

Reverse micellar synthesis and properties of nanocrystalline GMR materials (LaMnO3, La0.67Sr0.33MnO3 and La0.67Ca0.33MnO3): Ramifications of size considerations

Nanoparticles of complex manganites (viz. LaMnO₃, La_0.67Sr_0.33MnO₃ and La_0.67Ca{0.33}MnO₃) have been synthesized using the reverse micellar route. These manganites are prepared at 800‡C and the monophasic nature of all the oxides has been established by powder X-ray diffraction studies. TEM studies show an average grain size of 68, 80 and 50 nm for LaMnO₃, La_0.67Sr_0.33MnO₃ and La_0.67Ca{0.33}MnO₃respectively. Ferromagnetic ordering is observed at around 250 K for LaMnO₃, 350 K for La_0.67Sr_0.33MnO₃ and 200 K for La_0.67Ca{0.33}MnO₃. These Curie temperatures correspond well with those reported for bulk materials with similar composition.     

无机分子纳米材料的研究进展

无机分子纳米材料是至少在一个维度上为纳米尺寸的分子及以其为单元组成的材料。由于其特殊的结构和性质，这种材料可以作为未来纳米分子电子器件、小分子吸附及储存材料。本文将从合成、结构、性质、应用等方面, 结合最新进展对这一充满活力并有着应用前景的领域作一简要概述。     

联二炔囊泡的光致聚合、热致变色及应用

物理化学实验为各大高校本科化学教学的主干实验课程之一。虽然各高校的物理化学实验内容已十分丰富,但仍然缺乏将不同章节知识点融会贯通以及与学科前沿密切联系的综合型实验内容。我们根据南开大学郭东升教授课题组发表的一篇有关联二炔程序性响应检测胆碱酯酶的工作设计了“联二炔囊泡的光致聚合、热致变色及应用”的物理化学实验,涉及到联二炔缔合胶体的制备、联二炔的紫外光致聚合反应和聚联二炔的热致变色,进而显示其在防伪领域的潜在应用价值。希望通过此实验,使学生对物理化学中的缔合胶体、光化学、热力学、动力学等章节有更深一步的贯通性掌握,并了解自组装、光聚合、变色材料和防伪等相关研究领域的前沿动态。     

电子显微技术应用于生物纳米材料表征与测试的研究进展

该文简述了电子显微技术的发展历程,并介绍了现代电子显微镜的新功能。针对生物纳米材料理化性能与功能应用的特殊性,结合研究实例,重点阐述运用电子显微结构表征与原位分析测试技术指导构建新颖纳米结构、揭示材料与细胞/组织相互作用并发挥功能的机制。并在此基础上,展望了电子显微技术在生物纳米材料研究领域的发展方向(大尺寸图像拼接、三维重构、动态原位实时成像)。     

气相法合成一维无机纳米材料的研究进展

一维无机纳米材料是研究电子传输行为、光学特性和力学机械性能等物性的尺寸和维度效应的理想系统，将在构筑纳米电子和光电子器件等集成线路和功能性元件的进程中充当非常重要的角色，已成为当前纳米材料科学领域的前沿和热点。本文将从一维无机纳米材料的合成、表征和物性研究等方面，结合近年来国内外的最新进展对这一新兴领域作一概述。     

不同光滑度立方体氧化铁对液晶电光性能的改善

向列相液晶被广泛应用于液晶显示中,但是由于杂质的存在,会导致液晶的驱动电压变大,增加能耗。 为了降低阈值电压和饱和电压,通常向液晶中添加纳米颗粒来提高电光性能。 本文利用水热法制备了表面粗糙和光滑的两种立方体Fe₂O₃纳米颗粒,其形貌均匀,尺寸约550 nm。 将二者分别掺杂到向列相液晶E7中,结果表明,粗糙立方体Fe₂O₃/E7复合体系具有比光滑立方体Fe₂O₃/E7复合体系和向列相液晶E7更优的电光性能,且在掺杂质量分数为0.4%时,其电光性能达到最优,阈值电压和饱和电压分别降低9.9%和11.6%,对比度增大80%,响应时间降低至6.0 ms。 这归因于粗糙立方体Fe₂O₃具有足够的表面积和表面所带电荷更多,所以会更易吸附体系中的杂质离子和减弱杂质离子的屏蔽作用,从而提高了电光性能。     

Application of fractal geometry for studies of heterogeneity properties of nanomaterials

Calculations based on the fractal geometry in the estimation of surface heterogeneity are superior compared with conventional calculation methods (e.g. from the data of gas adsorption or X-ray radiation scattering) as they can be applied without limitation as far as the range of surface sizes of the studied structures is concerned. This paper presents structural characteristics of carbon and carbon- free nanomaterials based on the determined surface and volumetric fractal coefficients. Fractal coefficients were determined from the data obtained by means of two independent methods: sorptometry and atomic force microscopy (AFM). Correlation between porosity parameters and fractal coefficients is presented.