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小木虫论坛-学术科研互动平台 » 材料区 » 微米和纳米 » 前沿热点 » 纳米材料研究动态系列报道专栏
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wshk1980

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[交流] 纳米材料研究动态系列报道专栏

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美化学家发现金纳米棒自发地将自己组装成一种环状超结构
Science Daily — Rice University chemists have discovered that tiny building blocks known as gold nanorods spontaneously assemble themselves into ring-like superstructures.
链接：http://www.SciEI.com/news/science/Chemistry/Index.html
This finding, which will be published the chemistry journal Angewandte Chemie, could potentially lead to the development of novel nanodevices like highly sensitive optical sensors, superlenses, and even invisible objects for use in the military.

“Finding new ways to assemble nano-objects into superstructures is an important task because at the nanoscale, the properties of those objects depend on the arrangement of individual building blocks,” said principal investigator Eugene Zubarev, the Norman Hackerman-Welch Young Investigator and assistant professor of chemistry at Rice.

Although ring-like assemblies have been observed in spherical nanoparticles and other symmetrical molecules, until now such structures had not been documented with rod-shaped nanostructures.

Like many nanoscale objects, gold nanorods are several billionths of a meter, or 1,000 times smaller than a human hair. Zubarev used hybrid nanorods for this research because attached to their surface are thousands of polymer molecules, which are flexible chainlike structures. The central core of the nanorods is an inorganic crystal, but the polymers attached to the outside are organic species. The combination of the inorganic and organic features resulted in a hybrid structure that proved to be critical to the study.

英文全文：http://www.sciencedaily.com/releases/2007/03/070310145606.htm

[ Last edited by popsheng on 2007-4-28 at 18:12 ]
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1楼 2007-03-22 20:49:37
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zhaokelun1975

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New nanocomposites may mean more durable tooth fillings

A calcium phosphate nanocomposite filling in a tooth. The nanocomposite can "smartly" release decay-fighting agents to buffer against acids produced by bacteria, and rebuild the lost tooth minerals by releasing ions into the mineral-deficient area of the tooth. Credit: NISTThe mouth is a tough environment—which is why dentists do not give lifetime guarantees. Despite their best efforts, a filling may eventually crack under the stress of biting, chewing and teeth grinding, or secondary decay may develop where the filling binds to the tooth. Fully 70 percent of all dental procedures involve replacements to existing repairs, at a cost of $5 billion per year in the United States alone.

Now, however, scientists at the American Dental Association’s Paffenbarger Research Center, a joint research program at the National Institute of Standards and Technology, have shown that nanotechnology has the potential to lessen that toll by producing tooth restorations that are both stronger than any decay-fighting fillings available today, and more effective at preventing secondary decay. They report their findings in a recent issue of The Journal of Dental Research.

The researchers’ new technique solves a problem with the standard composite resin filling, a natural-looking restoration that is the method of choice when appearance is an issue. A dentist creates the filling by mixing the pure liquid resin with a powder that contains coloring, reinforcement and other materials, packing the resulting paste into the cavity, and illuminating the tooth with a light that causes the paste to polymerize and harden. For decay-fighting composite fillings, the problem arises from an additive that is included in the powder to provide a steady release of calcium and phosphate ions.

These ions are essential to the long-term success of the filling because they not only strengthen the crystal structure of the tooth itself, but buffer it against the decay-causing acid produced by bacteria in the mouth. Yet the available ion-releasing compounds are structurally quite weak, to the point where they weaken the filling as a whole．

To get around this conundrum, the Paffenbarger researchers have devised a spray-drying technique that yields particles of several such compounds, one of which being dicalcium phosphate anhydrous, or DCPA, that are about 50 nanometers across—20 times smaller than the 1-micrometer particles in a conventional DCPA powder.

Because these nanoscale particles have a much higher surface to volume ratio, they are much more effective at releasing ions, which means that much less of the material is required to produce the same effect. That, in turn, leaves more room in the resin for reinforcing fibers that strengthen the final filling. To exploit that opportunity, the Paffenbarger researchers also have developed nanoscale silica-fused fibers that produce a composite resin nearly twice as strong as the currently available commercial variety.

Citation: H.H.K. Xu, M.D. Weir, L. Sun, S. Takagi and L.C. Chow. Effects of calcium phosphate nanoparticles on Ca-PO4 composite, J Dent Res 86(4):378-383m 2007.

Source: National Institute of Standards and Technology
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11楼2007-04-28 17:47:23
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wshk1980

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Aberration-Corrected Imaging of Active Sites on Industrial Catalyst
Nanoparticle

Lionel Cervera Gontard, Lan-Yun Chang, Crispin J. D. Hetherington, Angus I. Kirkland,
Dogan Ozkaya, and Rafal E. Dunin-Borkowski

Angew. Chem. Int. Ed. 2007, 46, 1 – 4

http://www3.interscience.wiley.c ... /114199478/PDFSTART
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2楼2007-03-24 14:00:24
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wshk1980

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评价一下啊！！！！！！！！！！！！！
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3楼2007-03-29 16:27:40
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zhaokelun1975

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IBM将摩尔定律推进到三维时代


赛迪网2007年4月27日讯    日前，IBM宣布在制造环境中实现了一种突破性的芯片堆叠技术，此举为制造三维芯片扫清了障碍，摩尔定律也将因此而突破原来预期的极限。这种被称为“穿透硅通道（through-silicon vias）”的技术可以大大缩小不同芯片组件之间的距离，从而设计出速度更快、体积更小和能耗更低的系统。

    IBM的这项突破实现了从二维芯片设计到三维芯片堆叠的转变，将传统上并排安装在硅圆片上的芯片和内存设备以堆叠的方式相互叠加在一起，最终实现了一种紧凑的组件层状结构，大大减小了芯片的体积，并提高了数据在芯片上各个功能区之间的传输速度。

    IBM半导体研发中心副总裁Lisa Su表示：“这一突破性的进展是IBM开展十多年探索研究的成果。我们可以将三维芯片从实验室走向制造生产环节，来支持各种各样的应用。”

    这种IBM新方法是依靠新的穿透硅通道技术而非长金属电线来连接目前的二维芯片，这实际上是在硅圆片上蚀刻出来的垂直连接通道，并在其中注满金属。这些通道可以使多个芯片堆叠在一起，同时支持芯片之间更大信息量的传输。

    这项工艺将信息在芯片上传输的距离缩短了1000倍，与二维芯片相比可以增加最多100倍的信息通道或路径。

    IBM已经在自己的生产线上运行使用这种穿透硅通道技术的芯片，并将在2007年下半年开始为客户提供使用这种方法制造的芯片样本，同时在2008年投入生产。这种穿透硅通道技术最早将被用于无线通信芯片领域，这些芯片将被安装在无线LAN和蜂窝应用所使用的功率放大器之中。另外，三维技术也将应用于更广泛的芯片应用领域，包括目前那些运行在IBM高性能服务器和超级计算机中的芯片，这些服务器和超级计算机支持着全球的商业活动、政府和科学研究工作。
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5楼2007-04-28 17:06:23
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