欧美伦理一区二区-91视频网页-国产高清在线视频-国产黄色在线-免费的黄色-日本精品视频在线观看

新聞動(dòng)態(tài)
NEWS
Location:Chinese Academy of Sciences > NEWS  > News in field Carbon Nanotubes

Shaking Things Up Researchers Propose New Old Way to Purify Carbon Nanotubes

Come: Chinese Academy of Sciences    Date: 2013-06-04 09:39:09


An old, somewhat passé, trick used to purify protein samples based on their affinity for water has found new fans at the National Institute of Standards and Technology (NIST), where materials scientists are using it to divvy up solutions of carbon nanotubes, separating the metallic nanotubes from semiconductors. They say it s a fast, easy and cheap way to produce high-purity samples of carbon nanotubes for use in nanoscale electronics and many other applications.
 
Carbon nanotubes are formed from rolled-up sheets of carbon atoms arranged in a hexagonal pattern resembling chicken wire. One of the amazing features of nanotubes is that, depending on just how the sheet rolls up, a quality called chirality, the resulting tube can behave either like a semiconductor, with various properties, or like a metal, with electrical conductance up to 10 times better than copper. One big issue in creating commercially viable electronics based on nanotubes is being able to efficiently sort out the kind you want.
Thinking about how to do this, says NIST researcher Constantine Khripin, brought up the subject of biochemists and so-called  two-phase liquid extraction.   Biologists used this to separate proteins, even viruses,  says Khripin,  It s an old technique, it was popular in the 70s, but then HPLC [high-performance liquid chromatography] replaced a lot of those techniques.  People use HPLC to partition carbon nanotubes as well, he says, but it s less successful. HPLC divides things by exploiting differences in the mobility of the desired molecules as they travel small columns loaded with tiny spheres, but carbon nanotubes tend to stick to the spheres, reducing yield and eventually clogging the equipment.
The concept of liquid extraction is relatively straightforward. You make a mixture in water of two polymers that you ve selected to be just slightly different in their  hydrophobicity,  or tendency to mix with water. Add in your sample of stuff to be separated, stir vigorously and wait. The polymer solutions will gradually separate into two distinct portions or  phases,  the lighter one on top. And they ll bring along with them those molecules in your sample that share a similar degree of hydrophobicity.
It turns out that this works pretty well with nanotubes because of differences in their electronic structure -- the semiconductor forms, for example, are more hydrophobic than the metallic forms. It s not perfect, of course, but a few sequential separations ends up with a sample where the undesired forms are essentially undetectable.
Be honest. It s not that easy.  No,  agrees, Khripin,  People tried this before and it didn t work. The breakthrough was to realize that you need a very subtle difference between the two phases. The difference in hydrophobity between nanotubes is tiny, tiny, tiny.  But you can engineer that with careful addition of salts and surfactants.
 This technique uses some vials and a bench-top centrifuge worth a couple hundred dollars, and it takes under a minute,  observes team member Jeffrey Fagan.  The other techniques people use require an HPLC on the order of $50,000 and the yields are relatively low, or an ultracentrifuge that takes 12 to 20 hours to separate out the different metals from semiconductors, and it s tricky and cumbersome.
 The nanotube metrology project at NIST has been around for a quite a number of years,  says senior team member Ming Zheng.  It has been a constant interest of ours to develop new ways to separate nanotubes, cheaper ways, that industry can use in the development of nanoelectronics and other applications. We really think we have a method here that fits all the criteria that people are looking for. It s easy, it s scalable, it s high resolution -- all the good attributes put together.


Three examples of partitioning carbon nanotubes in liquid phases. Left: nanotubes partitioned by diameter. Smaller diameters, on the bottom, appear purple. Center: partitioned between semiconductors (amber, top) and metals. Right: A sample with different diameter range partitioned between metals (yellow) and semiconductors. Color differences are due to differences in electronic structure.

< Previous Super-Nanotubes: Remarkable Spray-O...Scientists Control Chirality in Carbo... Next >

?
Tel:+86-28-85241016,+86-28-85236765    Fax:+86-28-85215069,+86-28-85223978    E-mail:carbon@cioc.ac.cn,times@cioc.ac.cn,nano@cioc.ac.cn
QQ:800069832    Technical Support ac57.com
Copyright © Chengdu Organic Chemicals Co. Ltd., Chinese Academy of Sciences 2003-2025. manage 蜀ICP備05020035號(hào)-3
主站蜘蛛池模板: 久久只有这才是精品99 | 美女视频黄色网址 | 自怕偷自怕亚洲精品 | 国内精品影院久久久久 | 欧美日韩一区二区三区视频在线观看 | 国产精品久久久久久久久久一区 | 欧美极品在线播放 | 日本a级片免费观看 | 香蕉自拍视频 | 亚洲美女福利视频在线 | 日本特级黄毛片毛片视频 | 亚洲免费一区 | 欧美成人私人视频88在线观看 | 亚洲午夜精品一级在线播放放 | 香港免费毛片 | 国产成人高清精品免费5388密 | 色拍拍在精品视频69影院在线 | 中日韩美中文字幕 | 国产男女交性视频播放免费bd | 欧美午夜精品久久久久久黑人 | 亚洲天堂免费看 | 国产成人系列 | 欧美精品xxx | 国产亚洲精品国看不卡 | 女在床上被男的插爽叫视频 | 日本巨乳中文字幕 | a毛片在线观看 | 国产高清一区 | 日韩成人在线观看 | 国产成人精品亚洲2020 | 特级淫片欧美高清视频蜜桃 | 91热久久免费频精品黑人99 | 久久精品国产一区二区三区 | 久色视频在线 | 久久国产片 | 国产码一区二区三区 | 国产高清在线精品一区二区 | 亚洲国产cao | 成人免费视频国产 | 国产一区二区三区精品视频 | 国产uv1区二区三区 国产va免费精品高清在线观看 |