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New Technique Allows for Single Atomic Layer Patterning of Graphene

Last month when I suggested an imagined rivalry between graphene and molybdenite for replacing silicon in future transistors, I was pleased with the comments the piece received.

It would seem some are looking more towards the memristor replacing the transistor all together rather than just looking at how to improve transistors, and considering that a paper in IEEE Computer Magazine inspired an article in the New York Times maybe this will be the case.

But getting back to the transistor and graphene, it seems that researchers at Rice University have stumbled upon a way to pattern a single atomic layer of graphene.

The research, which was published last week in the journal Science, provides a technique for controlling the number of layers that are removed when patterning graphene, which previous techniques could not achieve.

“One cannot make a layer thinner than a single atomic layer. That’s it,” explains James Tour, Rice's T.T. and W.F. Chao Chair in Chemistry in the video below. “We have hit the bottom.” 

According to Ayrat Dimiev, a postdoctoral scientist in Tour's lab, the discovery of the patterning technique was a complete accident. “We had no idea that we would be removing a single carbon layer from graphene,” he says in the video. “We were trying to reduce the graphene in a new way using zinc and hydrochloric acid.”

While the patterning technique may not have a bottom on the vertical dimension, the researchers recognize that the ideal would be to achieve the same precision on the horizontal dimension. 

So graphene can be imbued with a band gap and it’s possible to achieve single atomic layer patterning so when can we expect to see someone making an electronic device out of the stuff?

High-throughput Analyzer Provides Size and Concentration Measurements of Nanoparticles

I have detailed in the past how biologists have felt forlorn in the world of imaging on the nanoscale.

Dejected biologists have continued to seek out some tools to aid them in seeing the nanoscale world. This search found some sympathetic researchers at the University of California Santa Barbara.

In an article over at Nanowerk, which delves into the details of the research that was first published in Nature Nanotechnology, the lead researcher on the project explains the motivation for developing what is being described as a “high-throughput label-free nanoparticle analyzer”.

"Our collaborators informed us of the significant need for similar technologies for particle analysis on the nanoscale for studying blood and other potential clinical applications, and we set to work," explains Jean-Luc Fraikin, the first author of the paper. "Only once we became more deeply involved in the project did we begin to appreciate the broader context for this work, given the range of applications for which nanoparticles in this size range are being developed, and the lack of practical sizing technologies that were available."

The device they developed is able to measure both the size of nanoparticles and their concentration in solution at a rate of 100,000 particles per second. This stands in stark contrast to the other methods that have been available for measuring these metrics, namely averaging and electron microscopy. With averaging there was no way of determining the varying sizes of the particles and electron microscopy was time consuming and expensive.

"The low-cost, scalable fabrication method, as well as the simple readout electronics, make this analyzer potentially useful in a wide range of applications," noted Fraikin in the Nanowerk article.

The analyzer is a micro-fluidic design with a micro channel that leads the analyte through a sensor consisting of “two voltage-bias electrodes and a single, optically lithographed readout electrode embedded in the microchannel.”

"Together, these components form a fluidic voltage divider that yields wide-bandwidth electrical detection of particles as they pass through the nanoconstriction," Fraikin explains in his Nanowerk interview. "The sensing electrode is embedded in the channel between the fluidic resistor and the nanoconstriction. As a particle enters the nanoconstriction, it alters the ionic current and, because of the voltage division between the fluidic resistor and the nanoconstriction, changes the electrical potential of the fluid in contact with the sensing electrode."

It would seem the time is right for having a cheap and easy-to-use device for measuring the size and concentration of nanoparticles in all sorts of solutions, not just biological ones. If Geoffrey Ozin is correct in his estimation that nanomaterials are at a saturation point where some more measurement of what we have is needed, then this could be tool to help in that regard.

But as the Nanowerk article points out, “While the nanoparticle analyzer discussed here measures two very basic physical properties of nanoparticles – their size and concentration in solution – many other characteristics of nanoparticles, such as surface charge, surface roughness, detailed particle shape and electric or magnetic polarizability are critical to their applications and will require tools for the high-throughput measurement these properties as well.”

Nanotech-enabled Products Face Numerous Obstacles on the Way to Market

It is with great pleasure I can report that I read a really first-rate article on nanotechnology from the mainstream press. It comes from the Irish Times and is based around an interview with Prof Peter Dobson of Oxford University, who had been in Ireland in early February for the Nanoweek conference

I had the pleasure of meeting Prof. Dobson in his role as Academic Director of Oxford University’s Begbroke Science Park when I was helping to give some visiting researchers a tour of UK research facilities. With no other motivation than to share his knowledge and experience, he gave us all some rich insights into how it can be possible to lift mere lab research into really making an impact.

The same too goes for this interview in the Irish Times. What is so intriguing about Dobson’s thoughts on nanotechnology and its commercialization is that he remains one of the few who is both a first-rate scientist with both an academic and industrial background and an accomplished businessman.

For me, the greatest lessons are often learned from failures rather than successes, so it is in his explanation of a recent failure of one of his spinout companies Oxford Biosensors that I found a good one. 

“That is a terribly sad story,” he recalls of Oxford Biosensors in the Irish Times article. Adding it was “too disruptive for any licence deal” and the costs of gaining regulatory approval proved overwhelming. 

“We developed a sensor for substances, in a pinprick of blood, which would be markers of cardiac risk. We were within eight or nine months of having a commercial product on the market, but we ran out of money.”

There are all sorts of ways for a company to fail, especially one that is using an emerging technology, but running out of money seems to be a common complaint. But what can’t be overlooked is that established players in the market, even if their technology is comparatively inferior, are not going to make it easy for anyone to introduce a technology into the market that will make their product obsolete.

As I was quoted in an article on the pages of Spectrum when discussing Nantero’s long-awaited nanotube memory chip: ”It is competing with large companies. Samsung, for instance, has created a $4 billion market for themselves with flash memory. Do you think they are going to idly sit by while some start-up says they are going to make that business obsolete? Not likely; they have their own approach, which they are developing in conjunction with University of Cambridge.”

The important lesson here to me is that even if there is strong market pull for your technology, even if you can bridge any regulatory obstacles, you still have to contend with entrenched market giants who just aren’t going to let you walk off with their business.

Nanostructured Material Promises to Double Li-ion Battery Capacity

Nanosys, the Palo Alto, CA-based nanomaterials company, which has long been touted as the IP King of Nanotech with over 500 patents for nanomaterials, has made an announcement recently about a nanomaterial to improve Li-ion battery capacity.

Yimin Zhu, director, battery & fuel cell, at Nanosys, made the announcement while speaking at the IEEE Bay Area Nanotechnology Council lunch forum last month. While the article is light on specifics, it seems that the company has developed a silicon-based, “architected” material that fills in the voids of the carbon anode material matrix.

According to Nanosys’s claims, the material “remains intact and fully functional after 100% DoD cycle testing.” It also “demonstrated a >2× capacity improvement using 10% additive in a Li+ battery anode.”

I managed to glean from the graphic below that the new material will increase density to 300Wh/kg from 170Wh/kg of a graphite coating, and do so with the addition of cutting costs.

While going through this article and Nanoys' website to get some more information, I noticed one annoying bit about the company's latest marketing copy is the term “architected”. Why create a word like this when there are already quite reasonable real words that would suffice: designed, structured, or fabricated. Just annoying.

Anyway, Nanosys is still in the business of making nanostructured materials (or should that be nanoarchitected materials?) and finding industry partners to apply these materials to some device.

Last year, at the CES show they were demonstrating how a nanomaterial they had developed could make the color of LED lights more vivid. On their website, they have a business unit called “LED backlighting”, but I haven’t heard whether they have started shipping that material to LED device manufacturers in bulk. 

According to the article in which Zhu is quoted, “volume revenue shipments are expected in 2011” for the material that promises to boost Li-ion battery capacity. I would like to hear later how it all works out because over the years I have developed some serious doubts about companies that are just selling nanomaterials rather than actual devices and other products.

Hydrogen Fuel Cells for Automobiles Look More Feasible with Nanostructured Storage Material

I have been skeptical of claims that nanotechnology was going to help usher in the hydrogen economy. This skepticism is not without reason.

When it turned out that carbon nanotubes were in fact pretty poor at storing hydrogen and their storage capacity was closer to 1wt% in practicality than the lofty 50wt% storage that some research had claimed, I became somewhat jaded.

But there is a new, shiny knight that is challenging my cynicism. It’s a UK-based company called Cella Energy.

I came to know of them through their recent winning of the Shell Springboard Awards, which earns them £40,000 (approximately US$65,000) and a press release.

Now, while some have waxed poetic about hydrogen fuel cells powering cars of the future, others have whispered that the complete lack of any infrastructure for transporting and delivering hydrogen was a pretty steep obstacle, not to mention the extraordinary cost of isolating hydrogen.

But it is in the former barrier that Cella has offered a solution. It seems they have developed a way of trapping hydrides in a nanoporous polymer, or microbeads, which allows the hydrogen to be stored at low pressure and ambient temperatures.

Just to give you a sense of how difficult it has been to store hydrogen (and imagine this system strapped to your automobile), the pressure needed for storing hydrogen has been typically “700 times atmospheric pressure (700bar or 10,000psi) or super-cooled liquids at -253°C (-423°F).” That could be described as a ticking time bomb traveling with you underneath your car.

With the Cella system since there is no special cooling system required or pressurized storage cylinders the hydrogen storage packaging will look pretty much like a typical fuel tank found on cars today.

Cella has not made any dramatic claims about percentage of hydrogen storage capacity like the carbon nanotubes hullabaloo. At the moment, they say that their materials are performing at “6wt% weight percentage of hydrogen, but Cella is now working with complex hydrides that store hydrogen at up to 20wt%.” According to the company website, this exceeds “the revised 2009 Department of Energy targets to produce hydrogen storage materials that would compete with gasoline.”

This all sounds great, but perhaps what is most intriguing about this technology is that the microbeads can be added to conventional fuels in today’s engines and would lower the emissions of those vehicles “to meet the new EU Euro 6 standards for emissions with minor vehicle modifications.”

Apparently, the nanoporous polymer is cheap to produce and Cella claims to be ready to ramp up production, it has applications for both hydrogen fuels cells cars or if that never gets off the ground it makes a fine fuel additive for reducing emissions. So, what’s not to love?

I’m not really sure, but I am bit troubled by their remarks that £40,000 is going to tip them over the edge and now they can ramp up industrial scale production. I am sure they were just be grateful for the prize money, but if they are sincere I can’t see how that amount does much more than pay their staff a month’s salary.

Could Super Conducting Graphene Quantum Dots Lead to Solid-State Qubits?

Quantum computers are sometimes referred to as the Holy Grail of computing, or maybe the Philosopher’s Stone of computing might be another appropriate medieval reference to a nearly unattainable quest. In any case, while some outfits have claimed they have achieved fairly significant quantum computer prototypes despite being met with skepticism, creating a quantum computer that can calculate something beyond what a kid in elementary school can factor has proven difficult.

One of the fundamental issues researchers have faced in developing quantum computers has been the problem of getting the computers to maintain more than a few quantum bits (or qubits). One of the more promising ways of getting beyond a mere seven qubits has been the use of quantum dots.

Now researchers at the University of Illinois led by Nadya Mason have brought a new wrinkle into this field of research. The research, which was initially published in the journal Nature Physics, was looking at what happens when a normal conducting material like a metal or graphene is sandwiched between two superconducting materials and observing the interface of the materials.

While it has been observed previously that normal metals in these instances take on the characteristics of the superconductor material when current is passed through it (namely, that it too will pass electron pairs through it rather than a single stream of electrons), the Illinois researchers by working with graphene quantum dots were able to better understand the fundamental physics at play: Andreev bound states (ABS).

To date, ABS have proven to difficult to both measure and observe. At is at this point that the researchers developed a novel method to isolate individual ABS by connecting probes to quantum dots made from graphene. As quantum dots do they confined the confined ABS into discrete energy states, which permitted the researchers to not only measure the ABS but to manipulate them.

"Before this, it wasn't really possible to understand the fundamentals of what is transporting the current," Mason said. "Watching an individual bound state allows you to change one parameter and see how one mode changes. You can really get at a systematic understanding. It also allows you to manipulate ABS to use them for different things that just couldn't be done before."

The concurrence of the two nanomaterials, graphene and quantum dots, along with the superconducting material made the breakthrough possible. 

"This is a unique case where we found something that we couldn't have discovered without using all of these different elements – without the graphene, or the superconductor, or the quantum dot, it wouldn't have worked. All of these are really necessary to see this unusual state," Mason said.

The Blue Dye in the Ink of Your Pen Provides New Development in Both Spin and Molecular Electronics

In collaborative research between Karlsruhe Institue of Technology (KIT) Center for Functional Nanostructures (CFN) and the Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), scientists have developed what is being dubbed the ‘world’s smallest magnetic field sensor’ by using the organic molecule hydrogen-phtalocyanin, used as the blue dye in pens.

The research, which was initially published in the journal Nature Nanotechnology, has drawn together the fields of spin electronics (or, “spintronics”) and molecular electronics by using one organic molecule to generate giant magneto resistance (GMR). As the Nature article terms it, “Giant magnetoresistance through a single molecule.”

It looks as though it could have an immediate impact where the grand daddy of the spintronics revolution—GMR—already holds sway in read heads for hard disk drives but make the reading speed even faster and the data density even greater.

But according to Prof. Wulf Wulfhekel, the lead researcher on the project, in an interview he gave for an article on the research, hard disk drive sensors are just the beginning.

“The use of spin for information encoding has several advantages — it’s non-volatile so you don’t need power to save the state of your machine,” explains Wulfhekel. “If you switch off your computer and switch it back on again, you don’t need to boot up. And also the power consumption is far lower, so this has advantages for mobile devices especially.”

It’s not clear to me, however, whether the researchers see this merely as a breakthrough in the area of hard disk memory or they see it as a move towards some kind of transistor and logic circuit of the future. The article, in which Wulfhekel is quoted, brings up this issue by comparing the scales of this component (one nanometer in diameter) to a carbon nanotube-based transistor that is on the scale of tens of nanometers.

In any case, it seems researchers at KIT have been pursuing molecular electronics rigorously recently with work done “to form a rigid light-emitting device based on single molecules."

While the electro-luminescence research didn’t have a clear application area, this latest research in creating a GMR effect with one molecule seems to be targeting mobile devices.

More Proposals for Nanotechnology in Addressing Oil Spills

Last May when the news cycle was providing non-stop coverage of the Gulf of Mexico oil spill, I wondered how long it would take for someone to ask how nanotechnology could be applied to solve the problem.

The issue that I came to realize was not that there weren’t any interesting proposals for using nanotechnology to address oil spills, but that there weren’t any real commercial solutions that could be applied in that instance. The one commercial product that was available, a nanoparticle-based dispersant, seemed to generate more controversy than offer a remedy.

So now that we're in a new year, it seems that someone has sat down to do a thorough review of the possibilities of applying nanotechnology to oil spills, and it appears to be the work of an organization out of India called Centre for Knowledge Management of Nanoscience and Technology.

But as impressive a catalogue as it is, it still amounts only to possible solutions, which kind of misses the point of what I discovered is the problem. If you want to solve a problem, you have to set aside time, resources and focus one’s will to creating a solution, which no one has done. Making a list of possible solutions may help organize the process but somebody really has to roll up their sleeves and develop one of them. 

It might make sense if regulators required that if an oil company is going to engage in deep-sea drilling then they need to have the resources for containing and cleaning up possible oil spills. In such an instance, not only are we protected from huge environmental disasters but we also create a commercial need that may lead to new companies that can come up with nanotechnology-based solution.

Worm-like Nanoparticles Could Be Planted Under Our Skin for Glucose Monitoring

In collaborative work between researchers at MIT and Northeastern University in Boston, MA a comparatively long and hollow nanoparticle has been developed that could be implanted under the skin and remain anchored at its original location to monitor levels of glucose or salt or other targets over time.

The work, which was initially published online last month in the journal Proceedings of the National Academy of Sciences, builds on the work of Karen Gleason, one of the lead researchers on this project, in using chemical vapor deposition (CVD) to create a coating with microscopic pores.

The breakthrough of the new nanoparticle, which is being called “microworms”, has to do with their shape. While spherical nanoparticle have been developed that could be filled with specific chemicals to detect various biomedical conditions and then implanted under the skin, they just wouldn’t stay where they were. They would get washed away.

To combat this, the research team developed tubes that were narrow enough to keep them more or less on the same dimensions as the spherical nanoparticles but were long enough in length so that they would better anchor to the location at which they were originally implanted.

Where this particular research seems a bit odd to me is in the area of its proposed applications. Now I try to remember Eric Drexler’s point in his blog late last year that scientists are held to two different standards when discussing applications to fellow scientists and then to lay people, but I can’t imagine these applications would be particularly attractive to lay people.

To copy and paste a bit the application proposals they go something like ‘microworms’ would “someday lead to implantable devices that would allow, for example, people with diabetes to check their blood sugar just by glancing at an area of skin.”

Now I’ve known people that had to regularly check their glucose levels, and this amounted to a pin prick of their finger and a drop of blood on test strip, then into the meter and voila. Pretty quick and pretty painless. But do I really want some area under my skin to reveal my glucose level? Seems kind of a long way to go for a fairly diminished return.

New Microscopy Technique Could Reveal Mechanisms of Cancer

Typically when asked about the role of nanotechnology in treating cancer, people refer to nanoparticle-based drug delivery systems (DDS) that target cancer cells. While these DDS treatments certainly add a new weapon to the arsenal used in the killing of cancer cells, they are still, as George Whitesides has said, our cells. So, killing cancer cells with more targeted poisons remains somewhat problematic.

In some ways a more hopeful, albeit a less immediate, method of addressing cancer with nanotechnology, is the use of microscopy tools for both early detection and unraveling the mechanisms by which cancer develops in us.

It is in the latter case that Nongjian (N.J.) Tao and his fellow researchers at the Biodesign Institute at Arizona State University have developed a method for improving the spatial information to the microscopy technique known as electrochemical impedance spectroscopy (EIS).

The work that went into developing this technique was published in the journal Nature ChemistryIt seems the researchers have created a hybrid technique that combines EIS with a technique based on surface plasmon resonance (SPR).

The hybrid technique is being dubbed electrochemical impedance microscopy (EIM) and differs from traditional EIS in that it does not measure current but instead employs the plasmon resonance to show the changes in impedance optically.

This development means that it is now “possible to study individual cells, but also resolve subcellular structures and processes without labels, and with excellent detection sensitivity (~2 pS).”

What these characteristics of the new technique enable is made clear in the video below in which researchers at Arizona State University now have the tools they need to look at the chemical modifications of the proteins that wrap up DNA up to control gene expression.

“Lots of people have gene defects that could lead to cancer but few actually get cancer,” explains Dr. Stuart Lindsay, Director, Center for Single Molecule Biophysics, at the Biodesign Institute at ASU. “Cancer is not a disease based on gene defects per se, but rather based on the chemical factors that control gene expression and those are the factors that we want to probe.”

 

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
Contributor
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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