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Electron Multiplication for Thin Film Solar Gets Some Skeptics

I have been very reluctant to get on the bandwagon that nanotechnology offered us any clear, never mind easy, solutions to getting solar power to be more efficient in generating electricity.

But I am always willing to consider the possibility that nanotechnology holds the key to making cheap and highly efficient solar power. One of the nano-related alternatives I discussed was the use of quantum dots for either electron multiplication or creating so-called “hot-carrier” cells.

As I had explained previously, “Electron multiplication involves making multiple electron-hole pairs for each incoming photon while with hot carrier cells the extra energy supplied by a photon that is usually lost as heat is exploited to make in higher-energy electrons which in turn leads to a higher voltage.”

The concept of electron multiplication has been a line of research vigorously pursued since 2004 when it was first proposed. In my blog on the subject, I highlighted research coming from the University of Minnesota and Texas that had investigated further the possibility of creating multiple charge carriers from one photon.

But Eran Rabani, a researcher at Tel Aviv University, was not so convinced by the research on electron multiplication.

"Our theory shows that current predictions to increase efficiencies won't work,” Rabani is quoted as saying in the linked article above. “The increase in efficiencies cannot be achieved yet through Multiexciton Generation, a process by which several charge carriers (electrons and holes) are generated from one photon."

Rabani has published two articles on his research, one is in the journal Chemical Physical Letters and the other in Nano Letters

While Rabani seems to be dismissing this line of research and the possibility that more than one electron pair can be generated from one photon, he believes that by eliminating this line of research it will open up other research directions that are more promising for solar technology.

However, it’s not clear that this has permanently closed the door on Multiexciton Generation as Rabani quote seems to indicate: “The increase in efficiencies cannot be achieved YET through Multiexciton Generation.”

Graphene Demonstrates Capabilities in Spintronics

Perhaps two of the most important recent developments in advanced materials for electronics have been giant-magneto resistance (GMR) and graphene.

While the GMR phenomenon was identified over twenty years ago, it wasn’t until 2008 that it garnered a Nobel Prize for its discoverers. However, in the years between its discovery and its Nobel Prize recognition it transformed hard-disk drive (HDD) memories into the terabyte stratosphere of today from the few gigabyte level they were at just a decade ago.

Graphene didn’t have to wait twenty years for its discoverers to earn a Nobel Prize. It managed to do that in just six years.

Whether there is something to the shorter elapsed time, I am not sure. But where GMR use of “spintronics” as opposed to “electronics” has remained in the HDD component of the computer, research is now showing that graphene may be able to extend spintronics into other areas of computers.

Researchers from the Nano-Science Center at the Niels Bohr Institute, University of Copenhagen, in collaboration with Japanese researchers, have discovered that bending graphene into a curved shape influences the spin of the electrons.

While the term “graphene” is oddly never used in the article on this research, graphene has not been considered a prime candidate for advancing spintronics because when it is laid out flat the electrons do not affect the spin and its direction remains random rather than patterned.

"However, our results show that if the graphite layer is curved into a tube with a diameter of just a few nanometers, the spin of the individual electrons are suddenly strongly influenced by the motion of the electrons. When the electrons on the nanotube are further forced to move in simple circles around the tube the result is that all the spins turn in along the direction of the tube", explain the researchers Thomas Sand Jespersen and Kasper Grove-Rasmussen at the Nano-Science Center at the Niels Bohr Institute.

The research, which was originally published in the journal Nature Physics, breaks out of the long-standing belief that this phenomenon could only be achieved with a single electron on a “perfect carbon nanotube.”

The researchers have not only demonstrated that this kind of alignment can be achieved with any number of electrons and with carbon nanotubes that have defects and impurities, but also have shown that you can control the strength of the effect and even turn it off completely.

These developments make a path to real-world applications seem far clearer.

Building 3D Nano Structures with RNA Resistant to Enzymes

The field of so-called RNA nanotechnology has been around for awhile, but it has had difficulty advancing as much as DNA nanotechnology despite its more flexible capabilities because of an enzyme known as RNase that eats RNA within minutes, making it extremely difficult to build anything with RNA without it being cut up into pieces in short order.

But Peixuan Guo and his colleagues at the University of Cincinnati have developed a method by which they replace a chemical group in the RNA making it become resistant to the RNase enzyme. Guo has been spearheading research with RNA and with this latest paper published in the American Chemical Society’s journal Nano he and his team may have established a way to take advantage of this macromolecule for building nanostructures from the bottom up.

Guo and his team focused their research on the ribose rings that along with alternating phosphate groups make up the backbone of RNA. By replacing one of the rings the researchers made it so the RNase could not attach itself to the RNA.

The advantages of RNA over DNA in bottom-up fabrication are that it can be manipulated like DNA “while possessing noncanonical base-pairing, versatile function, and catalytic activity similar to proteins.”

The Foresight Institute’s blog Nanodot has excellent coverage of this development that was written by Jim Lewis, who, according to his article, has spent most of his research career working with RNA.

Guo will be using the RNA in “gearing a powerful nanomotor that packages viral DNA into the protein shells of a bacterial virus named phi29.” 

Lewis’ closing sentence in his Foresight report sums it up eloquently: “It will be interesting to watch over the next several years if this variety of 3D structures leads to useful structures and devices for the development of molecular machine systems and ultimately productive nanosystems.”

"Nanoscoop" Material Promises 40x Faster Charging of Batteries

Researchers at Rensselaer Polytechnic Institute (RPI) in Troy, NY have developed a new type of nanomaterial they have dubbed “nanoscoops” because of its resemblance to an ice cream cone. The novel material promises to enable li-ion batteries to charge 40 to 60 times faster than conventional batteries.

The research, which was led by Professor Nikhil Koratkar and initially published in the journal Nano Letters, demonstrated how a “nanoscoop” electrode was able to achieve its faster charge in 100 continuous charge/discharge cycles.

“Charging my laptop or cell phone in a few minutes, rather than an hour, sounds pretty good to me,” said Koratkar in a RPI press release. “By using our nanoscoops as the anode architecture for Li-ion rechargeable batteries, this is a very real prospect. Moreover, this technology could potentially be ramped up to suit the demanding needs of batteries for electric automobiles.”

While this technology could increase the charge/discharge rates of li-ion batteries, I didn’t see any discussion within the coverage of the research whether it will improve the watt-hours of energy per kilogram (Wh/kg), which I noted last month to much criticism Secretary Steven Chu had suggested should reach a level of 1000Wh/kg in electric vehicles to compete with fossil fuels.

At any rate, Koratkar also intriguingly suggests in the piece that the nanoscoop material could enable the bringing together of supercapacitors—used for power-intensive functions such as starting the car—and traditional batteries—that provide high energy density for normal driving—into one single battery unit.

The trick to the nanoscoops capabilities lies in its composition, structure and size. In composition and structure it sounds like a good ice cream cone. They are “made from a carbon (C) nanorod base topped with a thin layer of nanoscale aluminum (Al) and a “scoop” of nanoscale silicon (Si)”.

It is this structure that accounts for the material’s ability to accept and discharge Li ion batteries at extremely fast rates and without causing damage. The layered structure of the nanoscoop transfers strain from the carbon layer to the aluminum layer and then finally to the silicon.

The next steps for the researchers will be to overcome the lack of overall mass of the electrode. They are investigating growing longer scoops or perhaps stacking numerous scoops on top of each other.

Just Because It's Smaller Doesn't Make It Nanotechnology

Andrew Maynard is often the first stop for mainstream journalists when they need to cover the story of nanotech. This is no doubt due to Maynard’s unique blend of scientific knowledge and his ability to communicate the science effectively to both the layman and his fellow scientist.

So when PBS decided to launch a new program as part of the Nova series entitled Making Stuff, hosted by New York Times technology columnist David Pogue, they must have been a little concerned that Maynard was less than enthusiastic about a clip from the program’s coverage of bioengineered materials both in terms of its ethical and safety point of view, the latter of which is Maynard’s bailiwick.

So David Levin, Nova's resident podcaster, contacted Maynard and they produced a podcast entitled The Dangers of Nanotech. Well, if anyone thought the program was being too soft on the safety aspect of bioengineered materials, it appears they more than made up for it by creating an alarmist title for a podcast on nanotechnology.

But Maynard tries mightily to fight back the alarmism by stating out front, “At the moment, the health issues [around nanotech] are very speculative.” And he continues on this vein balancing concerns with what we really know, not an easy task to perform.

But there is a notable omission in the whole discussion. We get initially the typical scare screed: “Nanotechnology is in everything from our pants to sunscreen, but how safe is it really?” And then not once in this nine-minute podcast do we get a discussion on the safety of the products that contain nanotech. It is like deciding to do a safety segment on electronics and you decide to spend the entire presentation on the toxicity of mercury. That’s all fine and good but shouldn’t we talk about the lifecycle of the products, just for 30 seconds or so.

The actual of topic of "Making Stuff" with nanotechnology is scheduled to air initially on January 26th, and is ingeniously entitled Making Stuff: Smaller. It is a pity that the description of the episode feels it necessary to trot out “micro-robots that probe the human body” as what the future holds as technology continues to go smaller. But I suppose that’s what really grabs the audience’s attention when it comes to nanotech.

But just a tip to the program’s producers in case they’re interested, just because the robots are small doesn’t make them nanobots, or even nanotech-related. in fact, the practice of combining the concepts of nanotechnology and micro robots really just confuses the matter.

Graphene for Electrodes in Organic Solar Cells Could Reduce Costs

While organic solar cells have been promising an inexpensive way to exploit solar power in comparison to their silicon-based cousins, things have not panned out in the marketplace quite as expected with flexible solar cells being rolled out onto roofs like asphalt roofing material.

But researchers at MIT believe they have overcome at least one obstacle with organic solar cells by finding a material for the electrodes that will match organic cells’ flexibility and replace the expensive indium-tin-oxide (ITO).

The magic material is none other than graphene, the wonder material of the latter half of the first decade of the 21st century.

Of course, this is not the first time that graphene has been discussed in relation to organic solar cells, but actually getting the graphene to go where you want it to go remained an obstacle.

In a paper published in the Dec. 17 edition of the Institute of Physics journal Nanotechnology, MIT professors Jing Kong and Vladimir Bulovic demonstrated how they were able to overcome the material’s resistance to adhering to the panel. The solution turned out to be a doping process that introduced impurities into the graphene that made it bond with the panel.

After having overcome this manufacturing obstacle, the graphene performed much like ITO except that it was more flexible and also transparent to allow all available sunlight to pass through. But perhaps most importantly, carbon is far more abundant than the increasingly rare ITO, which would likely reduce the cost of the product.

Big Story in Nanotech for Last Decade: The Funding Gap

In a gesture to recognize its tenth anniversary, TNTLog asked its readers what has been the best and worst stories surrounding nanotechnology in the last 10 years.

In my estimation, the big story in nanotech would be the funding gap, or, as it might alternately be termed, the innovation gap.

It seems governments around the world are anxious to invest billions of dollars into nanotechnology and then leave the small start-ups that this investment germinates to die on the vine while they are left to search in vain for the funding that could bring their technologies to market.

While IBM and other large companies, especially in the electronics and chemical industries, have invested heavily in nanotech, and this likely accounts for a large portion of non-government investment in the field, funding for small to medium enterprises attempting to bring a product to market just has not been strong or effective enough.

I have argued that financial institutions that have typically funded start-ups like these, such as venture capitalists or other private capital institutions, just have not been effective at bridging the seven to ten year of funding that these start-ups need. 

I bring this all up because we have another cautionary tale of how a company with a promising technology and some initial funding, ends up in bankruptcy due to little more than under capitalization.

The story of Carbon Nanoprobes Inc.’s failure is presented to us in contrast to the success of Saladax Biomedical Inc. The story gives us no information on why Saladax was successful in raising more financing than Carbon Nanoprobes. It could be any number of reasons, but a very likely reason would be that the ROI horizon was so far off for Carbon Nanoprobes that it constituted a much riskier investment.

This has been the overarching issue for nanotechnology’s development in the last 10 years. A generation of investors has been so conditioned by the era and hedge funds fueled by derivatives and glorified Ponzi schemes that the prospect of having to wait 7 to 10 years for their investment to pay off is just beyond their attention span.

I suppose that some Darwinian-influenced economic theory would be plugged in right about now, i.e. these companies failed because they were not strong enough.

Fair enough. But we are facing challenges so grand now in terms of feeding our growing population, supplying energy and even having clean drinking water that maybe we should find some way of supporting innovation in areas where we desperately need it, instead of allowing those potential solutions to disappear because it presented too much risk for financiers’ portfolios.

Where are my solutions? I don’t have a solution of my own but I like the direction that both Andrew Maynard and Tim Harper are going with the innovation framework they are developing as part of their roles with the World Economic Forum. 

Perhaps there are better ways to separate the wheat from the chaff in emerging technologies than just letting the financiers decide.

Is Determining the Impact of Nanotechnology a Useful Exercise?

The latest organization to take a crack at sorting out how nanotechnology is going to make its impact is the Organization for Economic Cooperation and Development (OECD), which has just published a report entitled The Impacts of Nanotechnology on Companies.

Sorting out the impact of nanotechnology is a favorite pastime for governments and extra-governmental organizations , and this time the method involves performing 51 case studies of companies from all over the world and all different sizes. We already have a breakdown of the report from Nanowerk that gives us the main points. And as you might expect when distilling a 111-page report into a blog post, the main points seem pretty…well, predictable.

We get the none-too-illuminating insights that nanotechnology is an enabling technology, larger companies can excel at the early stages of assimilating nanotechnology into their products and that nanotechnology is a complex field due to its calling upon various disciplines.

It seems that many of the reports quasi determinations have been long understood by anyone in the business of bringing to market a nano-enabled product, such as VCs are absent from the funding mechanisms available for companies trying to commericalize a nano-eanbled product.

Sometimes I wonder who this kind of information is supposed to benefit. It seems to be researched and written by bureaucrats, who then are the people who read and base policy upon it and then it all gets ignored, or worse followed.

Silver Nanoparticles Enable Real-time, Hand-held Biomarker Measurement Device for Athletes

While emerging technologies have often found early adoption in military applications where spendthrift practices have resulted in $500 toilet seats, perhaps the new area for prodigious spending on emerging technologies is in recreational sports.

Weekend athletes can now use carbon nanotubes in their tennis racquets, golf clubs and bicycles. And they’re willing to spend big bucks for the privilege.

So, it’s little surprise that a hand-held, self-diagnostic device is being touted as a tool for British athletes training for 2012 London Olympics rather than for application in the multiple-billon-dollar, point-of-care (PoC) market.

Argento Diagnostics, of course, is not ignoring the vast PoC market, but just like about every other company either making nanomaterials or developing a finished product enabled by nanomaterials, they are initially pursing sports applications for a very attractive introduction to the commercial marketplace.

On the one hand, you have a market that will provide all sorts of publicity for your technology (you can imagine that UK-based Argento after the London Olympics will be getting David Beckham to spit into their device) and then you have middle-aged, weekend athletes willing to spend any amount of money to ensure that they can improve their record-best time in their next triathlon.

However, what might make sense for an athlete training for an Olympic event, may not necessarily translate into use by a regular Joe. Either way, this application angle has won the technology a fair bit more media pixels than if they just been plodding through doctor’s offices trying to get them to use the device.

Artificial Palladium Is a Big Story in the Midst of Japan's Rare Earth Squeeze

The story of Japanese researchers who were able to combine rhodium and silver in a way to make an artificial palladium alloy “with nanotechnology” has been making the rounds this week as a new wrinkle in the medieval practice of alchemy.

However, I see it a bit differently. It seems to me more like a brilliant stroke of geo-economic politics.

This past Summer there was a rather significant imbroglio between China and Japan in which it was reported that China was suspending delivery of rare earth minerals to Japan over a fishing boat incident. (The issue of China’s current stranglehold on rare earths I covered myself here last Spring.)

Whatever the true story is on this Japan/China incident, ever since Japan has been looking into finding new sources of rare earths. It’s not like these rare earth minerals don’t exist anywhere else, it’s just that the rest of the world has stopped mining for them. In fact, as recently as the 1980s, the US dominated production.

While palladium is not strictly speaking a rare earth mineral, but rather a chemical element and belongs to the platinum group of metals, it is quite rare and in high demand from the electronics industry. So being able to synthesize palladium from the elements of rhodium and silver could conceivably make Japan less dependent on its sources for this element.

Geo-economic politics aside, the claims of this research are quite impressive, although some circles are already expressing skepticism over the results.

While one of the charges is that Japanese academics are typically quick to patent anything, even if it has questionable commercial applications, I imagine the context of the rare earth squeeze made the sound of trumpeting a new way to make palladium too attractive to pass up.



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

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