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Take Nanocrystals, Add Boiling Water, and Get a 400-Fold Increase in Luminescence

Just when you were about to throw out those old nanocrystals, a last minute shine from an ultraviolet light reveals previously non-existent luminescence. Is there a word for something that is even more serendipitous than serendipity?

Perhaps we will have to invent one after Prashant Jain, out of habit, put some nanocrystals that he was about to throw out under an ultraviolet light and discovered a significant increase in their luminescence.

Jain, now a chemist with the University of Illinois, was part of a team of researchers led by chemist Paul Alivisatos at the U.S. Department of Energy's Lawrence Berkeley National Laboratory. The team was looking at the "cation-exchange" technique for creating core/shell nanocrystals, in which one type of semiconductor is enclosed within another.

While this type of nanocrystal and technique for making them added a new contestant to compete with quantum dots and nanorods synthesized from colloids, they weren’t really impressing with their luminescence.

"While holding promise for the simple and inexpensive fabrication of multi-component nanocrystals, the cation-exchange technique has yielded quantum dots and nanorods that perform poorly in optical and electronic devices," explains Alivisatos in a press release.

But you put those same crystals on the shelf for six months and things change. Upon discovering the change, Jain thought that maybe he could make them change faster by heating the crystals…and it did.

"It was an accidental finding and very exciting," Jain says, "but since no one wants to wait six months for their samples to become high quality I decided to heat the nanocrystals to speed up whatever process was causing their luminescence to increase."

"By heating these nanocrystals to 100 degrees Celsius, we were able to remove the impurities and increase their luminescence by 400-fold within 30 hours," says Jain. "When the impurities were removed the optoelectronic properties of nanocrystals made through cation-exchange were comparable in quality to dots and nanorods conventionally synthesized. "Jain and his colleagues have published their work in the journal Angewandte Chemie under the title "Highly Luminescent Nanocrystals From Removal of Impurity Atoms Residual From Ion Exchange Synthesis".

Why Ener1 Went Bankrupt

It’s hard to deny that when Ener1 announced that it had built “a pilot nanotechnology-based manufacturing facility to fabricate electrodes for high discharge rate, lithium-ion batteries” that it sounded like we were about to witness a new successful nanotechnology company.

The fate of the company might have been foreseen, however, if one examined the use of this technology for this particular application area—namely Li-ion batteries for electric vehicles (EVs).

What was likely whispered among some battery experts became a bit more public when the US Secretary of Energy, Stephen Chu, implied over a year ago that the Li-ion battery might not be the best solution for powering EVs.

Just to be clear, I would like to see some technology replace the internal combustion engine for powering automobiles. I just don’t think it’s clear that the Li-ion battery is the best alternative.

It would seem that the marketplace agreed. In announcing its Chapter 11 bankruptcy yesterday, Ener1’s CEO, Alex Sorkin, acknowledged, “Our business plan was impacted when demand for lithium-ion batteries slowed due to lower-than-expected adoption for electric passenger vehicles."

If I may turn Mr. Sorkin’s assessment around somewhat, it might be that there are customers for electric passenger vehicles but those vehicles need to have the same level of functionality as the fossil-fuel-powered variety and come in at the same, or at least competitive, price. So, come up with a power source that does that and the demand for electric vehicles is there, especially at the current price for gasoline. It may be that the demand for EVs exists, just not for Li-ion-battery-powered EVs.

The Chapter 11 debt restructuring will allow the company to recapitalize itself to the tune of $81 million, but one has to wonder what $81 million will accomplish that a matching grant of $118 million from the US government couldn’t.

It seems accepted wisdom that technologies currently exist for eliminating a fossil-fuel economy and that just acts of will—including capital investment—will simply make this happen. But perhaps we’re not as far along as we imagine in the technological struggle or in the strategic application of capital to bring those technologies to market.

Carbon Nanotubes Bend and Stretch and Still Conduct

It seems the most desirable characteristic for electronics at the moment is flexibility, at least as far as nanotechnology research is concerned. Somehow—and I am not sure why—being able to bend electronic devices into various shapes seemed to take hold as a much sought-after quality with Nokia's conceptual introduction of the Morph phone four years ago based on joint research with Cambridge University.

I for one have always felt that a longer lasting battery was a more attractive feature in a phone than being able to wrap it around my wrist. But artificial skin has been raised as a possible application for flexible electronics recently and that sounds a good deal more like market pull than technology push.

Whatever the future holds for flexible electronics, the one thing we can say for certain is that nanotechnology, specifically carbon nanotubes, are pretty good at enabling it.

The most recent research in this vein comes from researchers at North Carolina State University who have developed a method for using carbon nanotubes as elastic conductors.

"We're optimistic that this new approach could lead to large-scale production of stretchable conductors, which would then expedite research and development of elastic electronic devices," says Dr. Yong Zhu, an assistant professor of mechanical and aerospace engineering at NC State, and lead author of a paper describing the new technique.

The approach, which was published online Jan. 23 in Advanced Materials, involves placing carbon nanotubes in parallel lines onto an elastic substrate. When the substrate material is stretched, the nanotubes are separated and maintain their parallel alignment. When the substrate is relaxed, the carbon nanotubes do not fall back into their previous positions but instead form into squiggly shapes and are now elastic and flexible while still retaining their excellent electrical properties.

The proposed list of applications includes “implantable medical devices, and sensors that can be stretched over unmanned aerial vehicles.” A bit of a new twist for flexible electronics.

Is this a quality of carbon nanotubes that simply works or is it truly useful? We’ll see if industry comes knocking.

Quantum Dots with Built-in Charge Could Lead to Highly Efficient Solar Cells

When you see 45 percent energy conversion efficiency for solar cells, you stop and take notice.

The story of nanotechnology in solar cells over the last decade has often been about pushing energy conversion efficiency higher and higher while dragging prices lower and lower. It hasn’t always been easy to sustain that dual-pronged attack.

Certainly, quantum dots have been looked at by researchers in this area as a possibility for achieving high conversion efficiency at a lower cost.

But I had no reason to expect that the use of quantum dots in solar cells would yield 45 percent conversion efficiency. Nonetheless that’s the figure I saw when University of Buffalo, in collaboration with both the Army Research Laboratory and the Air Force Office of Scientific Research,  announced a way of embedding charged quantum dots into solar cells that allows the cells to harvest infrared light.

The research, which was originally published in the ACS journal Nano Letters last May, used selective doping of some of the quantum dots so they have a built-in charge that repels incoming electrons. This in turn forces the electrons to travel around the quantum dots.

As the abstract explains: “We found that the quantum dots with built-in charge (Q-BIC) enhance electron intersubband quantum dot transitions, suppress fast electron capture processes, and preclude deterioration of the open circuit voltage in the n-doped structures. These factors lead to enhanced harvesting and efficient conversion of IR energy in the Q-BIC solar cells.”

The three University of Buffalo researchers behind this work—Vladimir Mitin, Andrei Sergeev and Nizami Vagidov—have spun-out a company called Optoelectronic Nanodevices LLC that presumably will attempt to commercialize this technology.

Can a New Public Private Partnership Be the Spur to Give Nanotechnology its Industrial Push?

The estimated $10 billion the US Federal government has invested in nanotechnology over the last decade was all intended to create a new economic stimulus for the US economy.  The plan was that nanotechnology would be a new source of jobs in the US and a partial remedy for the loss of its manufacturing base.

However, during that 10-year period there has been a fair amount of disappointment and frustration at what nanotechnology promised  and what it in fact delivered in economic terms.

Frankly, this kind of reaction was inevitable after investors and business types were still hung over from the Internet bubble bursting.

Seven to ten years of long-term investment just did not work with the funding mechanisms--like venture capital--that had fueled the Internet’s development.  And it seemed no one could really come to terms with this. So significant has been this funding gap that I have argued that it has likely been the most important story about nanotechnology over the last decade.

While I have expressed my doubts about Russia’s nanotechnology initiative, I have admired their decision to not only fund basic research but set up a funding mechanism that can move basic research into products and commercialization.

Now I have learned from a piece from Scott E. Rickert over at Industry Week that the US has established a new public/private consortium called the Advanced Manufacturing Partnership (AMP) that will invest more than $500 million in moving nanotechnology from the lab to the fab. President Barack Obama announced the AMP back in June 2011 and at the end of December 2011 plans were announced to establish a new office within the Department of Commerce to oversee the AMP.

Rickert in his piece breaks down how that half-a-billion dollars will be allocated:

  • $300 million in domestic manufacturing in critical national security industries. That includes high-efficiency batteries and advanced composites —where nanotech leads.
  • $100 million for the research, training and infrastructure to develop and commercialize advanced materials at twice the speed and a greatly reduced price.
  • $12 million from the Commerce Department for an advanced manufacturing technology consortium charged with streamlining new product commercialization.
  • $24 million from the Defense Department for advances in weaponry and programs to reduce development timetables that enable entrepreneurs get into the game.
  • $12 million for consortia to tackle common technological barriers to new product development—the way earlier partnerships approached nanoelectronics
  • A group of the nation's top engineering schools will collaborate to accelerate the lab-to-factory timetable with AMP connecting them to manufacturers.

While I am not entirely clear on how the $300 million will be spent on “domestic manufacturing in critical national security industries”, I do hope that it will bridge that funding gap for companies that don’t want another SBIR grant or can’t get one, but need capital to go on to an industrial scale.

My concern is that a small company that has spun itself out from a university, developed some advanced prototypes, lined up their market, and picked their management group still need by some estimates somewhere in the neighborhood of $10 to $30 million to scale up to being an industrial manufacturer of a product.

That means that $300 million could start up anywhere from 10 to 30 companies. Not exactly the next industrial revolution.

I more or less agree with Rickert’s conclusion that the AMP should remain focused on private investment. But perhaps there needs to be a bigger priming of the pumps to make the investment more appealing to the private sector. When capital can be invested in derivatives and credit swap defaults that provide huge returns, breaking even after 5-10 years is not as appealing as one might think.

Carbon Nanotubes Get a New and Simple Bulk Sorting Process

Recently researchers at the Lawrence Berkeley National Laboratory, Stanford University, and the University of California Davis devised methods for sorting single-walled carbon nanotubes (SWNTs) so that semi-conducting and non-conducting SWNTs are separated. One obvious application is artificial skin.

This has long been a bottleneck in using SWNTs for electronics applications and it seems that dam has broken because now researchers at the London Centre for Nanotechnology at Imperial College London, UK, have also developed a simple separation solution for SWNTs.

Previous methods for separating nanotubes have been fantastically expensive—billions of pounds per kilo, as Milo Shaffer, head of the London Centre, notes in an interview with Chemistry World.

In contrast, the method that the London researchers developed should allow for bulk separation at an industrial scale. But cautious optimism seems called for at this point.

“There are many different methodologies in the literature that can achieve separation but the work here has the additional benefit of being potentially scalable,” says Karl Coleman, a nanotechnologist at the University of Durham, UK, who was also quoted in the article. “There is still plenty to be done as, in the grand scheme of things, the work still discusses milligrams and it remains to be seen whether you can use this methodology for kilograms.”

This line of research began after researchers at the University College London, UK observed that Buckminster fullerenes dissolved in ammonia. The two labs then collaborated on finding a separation method for SWNTs by seeing what would happen when they mixed SWNTs with sodium-ammonia solution.

This mixture results in what is described as an ammonia solution of sodium “nanotubide”. The next step is to remove the ammonia from the mixture, which leaves behind a dry powder of the nanotubide salt. When dry dimethylformamide is added to this nanotubide salt, a portion of immediately dissolves. The portion that dissolves is the part that contains the metallic SWNTs.

What this presents is the possibility of developing a large-scale separation method that relies just on the different electronic characteristics of the SWNTs and eliminates the need for centrifugation. This method could find itself fairly quickly adopted into commercial usage—Chemistry World also reports that Shaffer’s team has already licensed the technology to the industrial gas company, Linde.

Are We Witnessing an "Axis of Evil" in Nanotech?

I imagine that if you want to send shivers down the spine of a US diplomat, you would simply mention either Venezuela or Iran.

In case you missed the last decade, the bellicose rhetoric that goes on between the US and both Venezuela and Iran seems to get periodically ratcheted up. Last week may have been no exception, but with a bit of a new wrinkle.

If perhaps your role in the US government is to oversee the development of nanotechnology, then you may have received a panicked call from someone in the State Department last week asking how the US is doing in the field, after it was announced that Venezuela and Iran would expand their cooperation in nanotechnology.

In addition to flaunting their capabilities in uranium enrichment, Iran has been promoting its capabilities in nanotechnology of late, and as it turns out they are just as capable as Western countries in over-hyping their capabilities.

While TNTLog may have deemed Iran’s nanotechnology capabilities that of a “world-class player", I certainly have my doubts. In fact Iran’s nanotech capabilities only appear impressive if you add a very strong qualifier: “considering”.

Yes, considering the years of sanctions and the isolation of Iranian scientists from the rest of the world, it is indeed impressive that they have managed much of a nanotechnology initiative at all.

But outside of this recent announcement, I admit to not having heard one word about nanotechnology in Venezuela. Certainly Venezuela with its recent oil riches fits the profile of a government that can pursue any line of research it wishes without much concern about what its population would like.

After doing a little background research on this story, it seems the Venezuelan and Iranian leaders initially forged this nanotechnology agreement last year, at which time the Venezuelans acknowledged that they didn’t have much of background in the field.

"We travelled to Iran to visit this festival [Nanotechnology Festival in Iran on the 25-29 October 2010] and sign MoUs of cooperation within the scope of nanotechnology study affairs because Venezuela is at the preliminary stages in nanotechnology and the researches of Iranian experts could be useful in helping Venezuela to develop nanotechnology", said Guillermo Barrerto the CEO of Science and Technology Center at Venezuelan Ministry of Science, according to the Iran Nanotechnology Initiative Council press release on the MoU with Venezuela.

You have to feel a bit of sympathy for Venezuela in that they are newbies to the field and they are relying on a country whose developments in nanotechnology are only impressive when one adds the qualifier: considering. It would seem for both countries, it's not a relationship that is going to do much to further either one in their nanotechnology research.

Magnetic Nanoparticles Lead to a New Class of Composites

How can you make a material that is simultaneously strong, flexible and light? The answer has long been advanced composites that combine plastics, metals and ceramics to get the best characteristics out of each of them.

But achieving a balance between these materials' qualities of strength, flexibility and lightness is difficult to come by and often comes down to being able to manipulate the various materials into the perfect orientation to each other.

Researchers at ETH-Zürich have developed a process that gives them a far greater control over that orientation than ever before. The result is an entirely new class of composite that mimics the precise layering seen in nature's abalone seashell.

The idea was simple. Why not get the materials to move to where you wanted them to go by the use of magnetic force, not unlike a bar magnet orienting iron fillings? However, the obvious problem is that not all materials used in composites are magnetic.

The researchers, who published their work in the January 13th issue of the journal Science in an article entitled "Composites Reinforced in Three Dimensions by Using Low Magnetic Fields," overcame this obstacle by adding a small amount of magnetic nanoparticles to the nonmagnetic materials.

The researchers discovered that this process of adding magnetic nanoparticles only works with stiff elements in the micrometer size range, which just so happens to overlap with the sizes the composite industry uses.

One would have to believe that this research will quickly find itself in commercial use as the ETH-Zürich researchers are continuing this work in collaboration with composite companies to get this straight into industrial processes.

The material will certainly get early adopters in any industry in which strong, light and flexible are sought after characteristics. While aerospace immediately comes to mind, the growing market of wind turbines should likely be another.

The addition of nanomaterials into advanced composites no longer seems like a mere marketing ploy,  but is increasingly becoming a way of actually making composites stronger or imbuing them with greater functionality. Perhaps nanocomposites are finally coming into their own.

Largest Quantum Computer Calculation to Date—But Is It Too Little Too Late?

After erring on the side of caution—if not doubt—when IEEE Spectrum cited D-Wave Systems as one of its “Big Losers” two years ago,  it seems that there was a reversal of opinion within this publication back in June of last year when Spectrum covered D-Wave’s first big sale of a quantum computer with an article and then a podcast interview of the company's CTO.

In the job of covering nanotechnology, one develops—sometimes—a bit more hopeful perspective on the potential of emerging technologies. Basic research that may lead to applications such as quantum computers get more easily pushed up in the development cycle than perhaps they should. So, I have been following the developments of D-Wave for at least the last seven years with a bit more credence than Spectrum had offered the company earlier.

In the continuing expansion of the company’s credibility in the development of quantum computers, D-Wave Systems has published a paper [pdf] in which they demonstrate an 84-qubit calculation of the notoriously difficult to calculate Ramsey numbers.

As the paper published in Cornell University’s arXiv journal states: “This computation is the largest experimental implementation of a scientifically meaningful quantum algorithm that has been done to date.”

The D-Wave researchers were able to complete this calculation in 270 milliseconds. This is a far cry from the much-ballyhooed ability of a quantum computer to factor the number 15.

But as impressive as this may sound, the blog Next Big Future conducted an interview with D-Wave’s CTO Geordie Rose just last month  in which Rose contends that the papers the company publishes are about two years behind where the company actually is in its research.

In Brian Wang's interview with D-Wave’s Rose, there's a discussion of the company’s new 512-qubit chip that should be, according to their calculations, 1000 times faster than the 128-qubit chips that D-Wave is currently working with.

As we learned from Steven Cherry’s podcast with Rose back in June, D-Wave was able to secure the $10-million sale of its hardware and software support so that Lockheed Martin could tackle some of their more difficult optimization problems.

So, it would seem optimization problems have become the measure by which D-Wave calculates how much more effective doubling the number of qubits on a chip can be in solving problems.

From the Next Big Future piece: “One application of the D-Wave system is for the optimization problem of creating treatment plans for cancer radiation treatment based on a 3D body scan. This treatment plan takes 1 week using the 128-qubit system but minutes with the 512-qubit system.”

While it may seem that D-Wave is on irreversible upward technological slope, one problem indicated in the Next Big Future interview is that capital may be beginning to dry up.

If so, it would seem almost ironic that after years of not selling anything and attracting a lot of capital, D-Wave would make a $10-million sale and then not be able to get any more funding.

But alas this is the sometimes topsy-turvy world of applying capital at the right time and in the right amount to emerging technologies.

This article was edited on 12 January 2012.

New Form of Graphene Opens up Applications in Thermal Conductivity for Electronics

Much has been made of how graphene’s lack of an inherent band gap holds it back in electronics applications.

But there are a couple of flaws in this argument. For one, not all would-be applications require the band gap seen in silicon-based materials. And what if there is actually more than one type of graphene?

Researchers at the University of Calfornia Riverside, in collaboration with researchers from The University of Texas at Austin, The University of Texas at Dallas and Xiamen University in China have in fact developed a new form of graphene whose purpose makes its lack of a bandgap irrelevant.

The researchers, led by Aelxander Balandin, a professor of electrical engineering at UC Riverside, and Professor Rodney S. Ruoff of UT Austin, have isotopically engineered graphene so it that has concentrations of 99.99 percent 12C (carbon) as opposed to the naturally occurring graphene that is found in concentrations of 98.9 percent 12C and 1.1 percent 13C.

What difference does 1 percent make? In a paper ("Thermal conductivity of isotopically modified graphene") published in the 8 Jan online version of the journal Nature Materials, the team reported that the slight variation in graphene's composition that they were able to achieve using chemical vapor deposition yielded a material that had remarkable heat dissipation qualities.  They say that the isotopically engineered graphene should should be useful in heat removal applications in a number of electronics applications as well as in photovoltaics.

“The important finding is the possibility of a strong enhancement of thermal conduction properties of isotopically pure graphene without substantial alteration of electrical, optical and other physical properties,” said Balandin in the UC Riverside press release. “Isotopically pure graphene can become an excellent choice for many practical applications provided that the cost of the material is kept under control.”

Importantly, the proposed applications do not call for graphene to replace silicon in the integrated circuit of the future, but for its use in the interconnects and thermal spreaders within computers or in transparent electrodes in photovoltaics.

Still, it's important to remember that while application proposals are intriguing at this stage, this is basic research. As Balandin remarks: “The experimental data on heat conduction in isotopically engineered graphene is also crucially important for developing an accurate theory of thermal conductivity in graphene and other two-dimensional crystals.”

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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
 
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Rachel Courtland
Associate Editor, IEEE Spectrum
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