Tag Archives: Chinese Academy of Sciences

Danish Chinese collaboration on graphene project could lead to smaller, faster, greener electronic devices

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A mixed team of Danish and Chinese scientists have made a transistor from a single molecular monolayer that works on a computer chip according to a June 19, 2013 University of Copenhagen news release,

The molecular integrated circuit was created by a group of chemists and physicists from the Department of Chemistry Nano-Science Center at the University of Copenhagen and Chinese Academy of Sciences, Beijing. Their discovery “Ultrathin Reduced Graphene Oxide Films as Transparent Top-Contacts for Light Switchable Solid-State Molecular Junctions”  has just been published online in the prestigious periodical Advanced Materials. The breakthrough was made possible through an innovative use of the two dimensional carbon material graphene.

Here’s how the transistor works (from the news release),

The molecular computer chip is a sandwich built with one layer of gold, one of molecular components and one of the extremely thin carbon material graphene. The molecular transistor in the sandwich is switched on and of using a light impulse so one of the peculiar properties of graphene is highly useful. Even though graphene is made of carbon, it’s almost completely translucent.

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Using the new graphene chip researchers can now place their molecules with great precision. This makes it faster and easier to test the functionality of molecular wires, contacts and diodes so that chemists will know in no time whether they need to get back to their beakers to develop new functional molecules, explains Nørgaard [Kasper Nørgaard, an associate professor in chemistry at the University of Copenhagen].

“We’ve made a design, that’ll hold many different types of molecule” he says and goes on: “Because the graphene scaffold is closer to real chip design it does make it easier to test components, but of course it’s also a step on the road to making a real integrated circuit using molecular components. And we must not lose sight of the fact that molecular components do have to end up in an integrated circuit, if they are going to be any use at all in real life”.

In addition to the other benefits of this graphene chip, greater precision, etc., it is also greener, requiring no rare earths or heavy metals.

If you have problems accessing the news release, you can find the information in a June 20, 2013 news item on Nanowerk.

Self-assembling, size-specific nanopores or nanotubes mimic nature

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I guess you can call this biomimicry or biomimetics as it’s also known. From the  State University of New York at Buffalo  July 17, 2012 news releaseby Charlotte Hsu,

Inspired by nature, an international research team has created synthetic pores that mimic the activity of cellular ion channels, which play a vital role in human health by severely restricting the types of materials allowed to enter cells.

The pores the scientists built are permeable to potassium ions and water, but not to other ions such as sodium and lithium ions.

This kind of extreme selectivity, while prominent in nature, is unprecedented for a synthetic structure, said University at Buffalo chemistry professor Bing Gong, PhD, who led the study.

Here’s how they did it (from the news release),

To create the synthetic pores, the researchers developed a method to force donut-shaped molecules called rigid macrocycles to pile on top of one another. [emphasis mine] The scientists then stitched these stacks of molecules together using hydrogen bonding. The resulting structure was a nanotube with a pore less than a nanometer in diameter.

The July 17, 2012 media advisory by Tona Kunz from the Argonne National Laboratory (one of the partners in this research) describes why creating consistently sized nanopores/nanotubes has been so difficult and offers more information about the macrocycles,

Nanopores and their rolled up version, nanotubes, consist of atoms bonded to each other in a hexagonal pattern to create an array of nanometer-scale openings or channels. This structure creates a filter that can be sized to select which molecules and ions pass into drinking water or into a cell. The same filter technique can limit the release of chemical by-products from industrial processes.

Successes in making synthetic nanotubes from various materials have been reported previously, but their use has been limited because they degrade in water, the pore size of water-resistant carbon nanotubes is difficult to control, and, more critically, the inability to assemble them into appropriate filters.

An international team of researchers, with help of the Advanced Photon Source at Argonne National Laboratory, have succeeded in overcoming these hurdles by building self-assembling, size-specific nanopores. This new capability enables them to engineer nanotubes for specific functions and use pore size to selectively block specific molecules and ions.

Scientists used groupings of atoms called ridged macrocycles that share a planar hexahenylene ethynylene core that bears six amide side chains. Through a cellular self-assembly process, the macrocycles stack cofacially, or atom on top of atom. Each layer of the macrocycle is held together by bonding among hydrogen atoms in the amide side chains. This alignment creates a uniform pore size regardless of the length of the nanotube. A slight misalignment of even a few macrocycles can alter the pore size and greatly compromise the nanotube’s functionality.

Here’s an image of the macrocycles supplied by the Agronne National Labortory,

A snapshot of a helical stack of macryocycles generated in the computer simulation.

The size specificity is  important if  nanopores/nanotubes are going to be used in medical applications,

The pore sizes can be adjusted to filter molecules and ions according to their size by changing the macroycle size, akin to the way a space can be put into a wedding ring to make it fit tighter. The channels are permeable to water, which aids in the fast transmission of intercellular information. The synthetic nanopores mimic the activity of cellular ion channels used in the human body. The research lays the foundation for an array of exciting new technology, such as new ways to deliver directly into cells proteins or medicines to fight diseases.

The research group’s paper has appeared in Nature Communications as of July 17, 2012, from Hsu’s news release,

The study’s lead authors are Xibin Zhou of Beijing Normal University; Guande Liu of Shanghai Jiao Tong University; Kazuhiro Yamato, postdoctoral scientist at UB; and Yi Shen of Shanghai Jiao Tong University and the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. Other institutions that contributed to the work include the University of Nebraska-Lincoln and Argonne National Laboratory. Frank Bright, a SUNY Distinguished Professor of chemistry at UB, assisted with spectroscopic studies.

Why asbestos and carbon nanotubes are so dangerous to cells

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Sphere or spear? Apparently cells can’t tell that an asbestos fibre or long carbon nanotube are spears due to their rounded tips according to researchers at Brown University. From the Sept. 18, 2011 news item on Nanowerk,

Through molecular simulations and experiments, the team reports in Nature Nanotechnology that certain nanomaterials, such as carbon nanotubes, enter cells tip-first and almost always at a 90-degree angle. The orientation ends up fooling the cell; by taking in the rounded tip first, the cell mistakes the particle for a sphere, rather than a long cylinder. By the time the cell realizes the material is too long to be fully ingested, it’s too late.

Here’s a representation of what the scientists mean,

 

Something perpendicular this way comes Cells ingest things by engulfing them. When a long perpendicular fiber comes near, the cell senses only its tip, mistakes it for a sphere, and begins engulfing something too long to handle. Credit: Gao Lab/Brown University

Here’s what happens when a cell encounters a carbon nanotube, asbestos fibre, gold nanowires, and other materials that are long and perpendicular with rounded tips,

Like asbestos fibers, commercially available carbon nanotubes and gold nanowires have rounded tips that often range from 10 to 100 nanometers in diameter. Size is important here; the diameter fits well within the cell’s parameters for what it can handle. Brushing up against the nanotube, special proteins called receptors on the cell spring into action, clustering and bending the membrane wall to wrap the cell around the nanotube tip in a sequence that the authors call “tip recognition.” As this occurs, the nanotube is tipped to a 90-degree angle, which reduces the amount of energy needed for the cell to engulf the particle.

Once the engulfing — endocytosis — begins, there is no turning back. Within minutes, the cell senses it can’t fully engulf the nanostructure and essentially dials 911. “At this stage, it’s too late,” Gao [Huajian Gao] said. “It’s in trouble and calls for help, triggering an immune response that can cause repeated inflammation.”

I gather this is the starting point for mesothelioma. Here’s a description of the process (from the Brown University Sept. 18, 2011 news release,

“We thought the tube was going to lie on the cell membrane to obtain more binding sites. However, our simulations revealed the tube steadily rotating to a high-entry degree, with its tip being fully wrapped,” said Xinghua Shi, first author on the paper who earned his doctorate at Brown and is at the Chinese Academy of Sciences in Beijing. “It is counter-intuitive and is mainly due to the bending energy release as the membrane is wrapping the tube.”

Here’s a video from Brown illustrating the process,

Cells bite off more than they can chew from Brown PAUR on Vimeo.

The whole thing has me wondering about long vs. short carbon nanotubes. Does this mean that short carbon nanotubes can be ingested successfully? If so, at what point does short become too long to ingest? It doesn’t seem like my questions are going to be answered too soon since the team would like to go in this direction (from the Brown news release),

The team would like to study whether nanotubes without rounded tips — or less rigid nanomaterials such as nanoribbons — pose the same dilemma for cells.

“Interestingly, if the rounded tip of a carbon nanotube is cut off (meaning the tube is open and hollow), the tube lies on the cell membrane, instead of entering the cell at a high-degree-angle,” Shi said.

Nanotechnology and European NGOs; 2009 Nobel in Physics has Canadian connections; China’s nanotechnology roadmap; Canada Research Chair Hongbin Li

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Lately (as in this year), there’s been a lot of substantive interest in regulating nanotechnology:

  • the recent joint Transatlantic Regulatory project which brought together the London School of Economics, Chatham House, the Environmental Law Institute and the Project on Emerging Nanotechnologies (PEN) for a report and a series of presentations.  (I discussed the PEN presentation here.)
  • the recent announcement from the US Environmental Protection Agency about their new nanomaterials research which will presumably result in discussion about regulations. (I mentioned the announcement here.)
  • the January 2009 announcement by Environment Canada that they would be conducting a one time nanomaterials inventory. This type of announcement offers the distinct possibility that future regulation may be on the agenda. (I first discussed  this initiative in my Feb. 3, 2009, Feb. 4, 2009, and Feb.8, 2009 postings.)

Now a new group has issued a report, the European Environment Bureau (from the news item on Nanowerk),

The European Environmental Bureau (EEB), Europe’s largest federation of environmental citizens’ organisations, launched a report (“Nanotechnologies in the 21st Century – A Critical Review of Governance Issues in Europe and Elsewhere (October 09”)  outlining the critical governance structures needed for the safe development and use of nanotechnology.

You can read more here.

As I noted in my headline, the 2009 Nobel Prize for Physics has some Canadian connections. From the Fast Company article by Kit Eaton,

Half the prize went to Charles Kao for work that led to long-distance fiber-optic communications. Born in Shanghai, he was educated in the U.K. and worked in one of the early companies that became the current Nortel (emphasis mine). This is where he did research into the fiber-optic systems available at the time, which had been puzzling scientists and engineers by not nearing their theoretical efficiency, and remaining good only for short-distance signaling. Kao’s experiments proved the reason behind these inefficiencies was impurities in the glass making up the fibers–this effected the refractive index of the medium as well as how much light was wasted by scattering instead of being neatly piped down the fiber to the receiving electronics.

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The other half of the prize was shared by Canadian (emphasis mine) Willard Boyle and American George Smith for their co-invention of the Charge-Coupled Device. This little optically-sensitive chip, with its neat shift-bit way of getting data from the individual light-sensitive pixels to the data pipe that connects the sensor to a computer, is basically the invention that made possible the whole field of digital photography.

If you have any interest in China’s science and technology scene, Springer and the Chinese Academy of Sciences have announced that they are publishing a series of reports, roadmaps for the next 40 years.  The first reports are out on Oct. 14, 2009 and there will be more in 2010. I see that one of the 2010 reports will be on nanotechnology. For more details, you can go here.

I almost missed the announcement that Dr. Hongbin Li at the University of British Columbia has received a Canada Research Chair in Molecular Nanoscience and Protein Engineering. Congratulations Dr. Li! I posted a two-part interview in 2008 that  Dr. Li kindly granted me here and here.