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一.Published online: 23 May 2007 | doi:10.1038/nchina.2007.86 Mesoporous materials: Carbon-black magic Hongfei Wang Abstract:An aerosol-assisted self-assembly approach is being used to make mesoporous carbon-rich spheres Many applications could use a simple and efficient technique to create mesoporous (containing nanoscale pores) carbon-rich spheres with high surface areas and large uniform pores. Dongyuan Zhao and co-workers1 at the Fudan University in Shanghai have performed this feat with a one-step synthesis using an aerosol-assisted self-assembly approach, initially developed for mesoporous silica articles2. The aerosol consists of a carbon-based precursor solution containing phenolic resols, a type of liquid resin, and triblock copolymers, which act as templates for the mesopores. To make the spheres, the aerosol is passed through a special tool to form aerosol droplets. When these droplets dry, the triblock copolymer templates are removed by heating and calcination in nitrogen gas. The size and structure of the pores are controlled by changing the amount and type of copolymer templates, as well as the amount of phenolic resol used in the droplet-making process. Using this approach, the researchers made ordered mesoporous carbon-rich spheres with diameters from 100 nm to 5 m. Previous approaches could not preserve the quality and structure of the mesopores under harsh fabrication conditions and template-removal processes. Structural analysis of the new material reveals well-ordered pores with a uniform pore size — ideal for use in separation and catalysis. The authors in this work are from: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Key Laboratory of Molecular Engineering of Polymers, Advanced Materials Laboratory, Fudan University, Shanghai, China. References: 1.Yan, Y., Zhang, F., Meng, Y., Tu, B. & Zhao, D. One-step synthesis of ordered mesoporous carbonaceous spheres by an aerosol-assisted self-assembly. Chem. Commun. (2007). | Article | 2.Lu, Y. et al. Aerosol-assisted self-assembly of mesostructured spherical nanoparticles. Nature 398, 223–226 (1999). | Article | ISI | ChemPort | 二.Nanocrystals: The more the better Wei Zeng Abstract:Tetrahexahedral platinum nanocrystals can be synthesized using an electrochemical method The catalytic performance of nanocrystals can be enhanced by increasing their number of facets (flat faces). It is, however, rather difficult to synthesize nanocrystals with many facets because of their high surface energy. Now, Shigang Sun, Zhonglin Wang and co-workers1 have produced tetrahexahedral (24 facets) platinum nanocrystals of high purity using an electrochemical method that has a high yield and is cost efficient. Platinum nanospheres, 750 nm in size, are deposited onto a 'glassy carbon' electrode in a standard three-electrode cell. When a square-wave potential is applied to the glassy carbon, small tetrahexahedral nanocrystals begin to grow on the electrode surface at the expense of the larger nanospheres. By varying the operation conditions, nanocrystals with sizes from 20 nm to 240 nm were achieved. Tetrahexahedral crystals occasionally exist in nature in fluorite and diamond, but very rarely in metals. The surfaces of these platinum nanocrystals are not only chemically and thermally stable (up to 800 ºC), but they also enhance catalytic activity for electro-oxidation of small organic fuels up to four times as much as bulk platinum. In addition, they can be used in a wide range of applications, including car converters and gas sensors. The authors in this work are from: State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA. References Tian, N., Zhou, Z. Y., Sun, S. G., Ding, Y. & Wang, Z. L. Synthesis of tetrahexahedral platinum nanocrystals with high-index facets and high electro-oxidation activity. Science 316, 732–735 (2007). 三.Solar Cells: Taking the sun Anne Pichon Abstract：Novel organometallic polymers make highly efficient solar cells Photoactive materials have been investigated as a way of developing cost-effective solar-powered devices. So far, conventional solar cells fabricated by blending organic polymers with fullerene have reached power-conversion efficiencies of only up to 5%, although theoretical calculations predict that efficiency could be up to 11% with a fully optimized coverage of the solar spectrum. Using lower-bandgap polymers with optimized energy levels and electron-transfer processes, a number of organic polymers have still met with limited success. Raymond Wai Yeung Wong, Aleksandra Djurisic and co-workers1 have explored the combination of other novel materials. The researchers found that solar cells fabricated using different blend ratios of platinum polyyne — a low-bandgap organometallic polymer — and fullerene have power-conversion efficiencies with an average of 4%, without the need for complicated device structures. This value is two to three times higher than that reported for other lower-bandgap polymers. Although the power-conversion efficiency is still lower than the best result ever reported, solar cells fabricated using such organometallic materials could be improved by optimizing both the chemical composition of the polymer and the device structure. The authors in this work are from: Department of Chemistry and Centre for Advanced Luminescence Materials, Hong Kong Baptist University, Hong Kong, China; Department of Physics and Department of Chemistry, University of Hong Kong, Hong Kong, China. References Wong, W. Y. et al. Metallated conjugated polymers as a new avenue towards high-efficiency polymer solar cells. Nature Mater. (2007). | Article | [ Last edited by luo.henry on 2008-4-25 at 15:45 ] |
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