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Nanoparticle Enables World Record for Energy Storage in Batteries

With just one week under our belts in this New Year, we already have some world-record news in relation to lithium-ion (Li-ion) batteries and nanoparticles. Researchers at Stanford University and the SLAC National Accelerator Laboratory have developed a Li-ion battery in which its sulfur cathode was capable of storing five times more energy than is possible with today’s commercially available batteries.

The research—not surprisingly—was led by Stanford’s Yi Cui. What may be somewhat surprising is that Cui has focused his attention in this research on the cathode rather than the anode of the battery. Much of Cui’s most recent work has been on improving the anodes of Li-ion batteries through the use of nanostructured silicon. In this latest research, he has not only shifted his attention to the cathode, but also developed an entirely new material to do it.

The new material, which is described in the Jan. 8 edition of Nature Communications (“Sulphur–TiO2 yolk–shell nanoarchitecture with internal void space for long-cycle lithium–sulphur batteries”),  is a nanoparticle that is made up of an inner core of sulfur surrounded by an outer layer of porous titanium-oxide. The nanoparticles architecture resembles that of the yolk and shell of an egg.

This nanoparticle’s new architecture has broken down an obstacle to using sulfur in the cathode of Li-ion batteries that has persisted for around 20 years.

While it has been known that sulfur could store more lithium ions than other cathode materials, the combination of sulfur atoms with lithium ions resulted in a compound—though necessary for the cathode to operate—that kept dissolving and limited the storage capacity of the battery. Also, when the lithium ions went into the cathode, it would expand the size of the cathode by 80 percent. Attempts to employ protective coatings to correct the first problem of the compound dissolving just resulted in them cracking as soon the lithium ions expanded the cathode.

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Graphene Takes Aim at Treating Alzheimer’s and Cancer

When graphene was first introduced, it seemed everyone wanted to apply it to electronics, especially after carbon nanotubes were turning into such a disappointment in the field.  But graphene has a huge strike against it in electronics: it lacks a band gap. So everyone, including major electronics players like IBM and Samsung, looked for ways to give graphene a band gap.

While researchers were hard at work wrestling graphene into a role it didn’t seem to want to play, others were looking at what it might like to do. This led to work that looked at using graphene for applications ranging from rustproofing to photovoltaics.

Now the biomedical field is increasingly looking at graphene as a material for advancing therapeutics and diagnostics where its capabilities might be ideally suited. An article in the journal Advanced Materials ("New Horizons for Diagnostics and Therapeutic Applications of Graphene and Graphene Oxide") outlines some of the ways that graphene and its oxide are promising improved diagnostics and therapeutics for maladies ranging from Alzheimer’s to cancer.

Of course, some of the applications for graphene in the biomedical field are within areas that are at least tangential to those already mentioned, like electronic devices and transparent conductors. But graphene is also being looked at for drug and gene delivery applicationsphoto-therapy of cancer  and biosensors. In particular, researchers have been experimenting with combining graphene with near-Infrared (NIR) phototherapy and imaging.  There has been some progress in using graphene-enabled NIR photothermal therapy for cancer and Alzheimer's disease (AD).

While both pure graphene and graphene oxide have exhibited some toxicity to cell and animals, it has been found that coating the graphene with a biocompatible polymer results in no detectable toxicity in both cellular and animal testing.

Graphene’s application to this field is still in its infancy, however, early testing has shown promise that it could play an important role in future disease diagnostics and treatment.

Image:  Luis E. F. Foa Torres

Graphene Still Trying to Replace ITO in Organic Solar Cells

Almost two years ago, researchers at MIT were heralding graphene as a possible replacement for the expensive indium-tin-oxide used in electrodes for organic solar cells. They showed a way in which the entire solar cell could be flexible—including its electrodes—and transparent.

Not long after that, research at Rice University picked up on the use of graphene for replacing ITO, but aimed their work towards creating a thin film for touch-screen displays.

Now researchers at MIT are reporting on work that, like the Rice team, combines flexible sheets of graphene with a grid of metallic nanowires. In so doing, they turned their attention back to photovoltaics. The research (“Graphene Cathode-Based ZnO Nanowire Hybrid Solar Cells”) was published in the journal Nano Letters.

While this latest research is not the first time graphene was used a replacement for ITO—even at MIT—it does have the distinction of being a graphene-nanowire solar cell with a respectable energy conversion efficiency of 4.2 percent. While this may not sound like a world-beating number, it stands up well to that of ITO-based devices with similar architectures.

“We’ve demonstrated that devices based on graphene have a comparable efficiency to ITO,” says Silvija Gradečak, one of the MIT researchers involved in the project, in a press release. “We’re the first to demonstrate graphene-nanowire solar cells without sacrificing device performance.”

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Fundamental Photoconductivity Mechanisms of Graphene Revealed

A team from the IBM Nanoscale Science and Technology group has revealed some of the fundamental mechanisms of photoconductivity in graphene. In particular, the researchers demonstrated that the photoconductivity of graphene can be either positive or negative depending on its gate bias.

The research team includes Marcus Freitag, Tony Low, Fengnian Xia and Phaedon Avouris (who we interviewed on this blog for his work in creating a band gap in graphene). The group works out of IBM's T. J. Watson Research Lab, in Yorktown Heights, N.Y. and published their work (“Photoconductivity of graphene”) in the online version of Nature Photonics.

The impetus for their “classic photoconductivity experiment” was the appealing optoelectronic properties of graphene. It at once possesses high carrier mobility, zero bandgap, and electron-hole symmetry.

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Nanoparticle Coated Lens Converts Light into Sound for Precise Non-invasive Surgery

Remember how Leonard McCoy performed surgery in Star Trek? He would wave a device over the patient. The outer layers of the skin didn't need not be cut, even when operating on internal organs, and the precision of 23rd century instrument reached down to the level of individual cells.

Well, we already have a bit of that in the 21st. Research at the University of Michigan, led by Jay Gou, has developed a device that employs a carbon-nanotube-coated lens capable of converting light into tightly focused sound waves. The new ultrasound therapeutic tool that reaches new levels of precision—its high-amplitude sound waves are able to target an object with dimensions of 75 by 400 micrometers.

In the image to the right, you can see a150-µm hole that the researchers drilled into a confetti-sized artificial kidney stone.

"A major drawback of current strongly focused ultrasound technology is a bulky focal spot, which is on the order of several millimeters," says Hyoung Won Baac, who worked on the project as a doctoral student and is now a research fellow at Harvard Medical School, in a press release. "A few centimeters is typical. Therefore, it can be difficult to treat tissue objects in a high-precision manner, for targeting delicate vasculature, thin tissue layer and cellular texture. We can enhance the focal accuracy 100-fold."

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DNA Nanotechnology Takes Two Big Steps Forward in Manufacturing

A fundamental, unproven assumption in the field of DNA nanotechnology was that the nanoscale objects produced through DNA self-assembly achieved atomically precise positional accuracy.

Researchers at Technische Universitaet Muenchen (TUM), led by Hendrik Dietz, have challenged that assumption head on and built a 3-D object using DNA self assembly techniques and found that indeed the object met its design specifications down to the sub-nanometer scale.

For years now, research has shown that DNA could be programmed to take the shape of pre-determined objects. If a five-pointed star was desired, it was possible to program the DNA so that it took a shape that resembled very closely the original design. But no one really knew if the final objects met the original designs at the atomic scale.

To prove this assumption, the TUM researchers designed a test object that was suitable for low-temperature electron microscopy. This object allowed for an electron density map to be generated of the object in which the resolution of the map was sufficient for a pseudo-atomic model that could be flexibly fitted to the entire object. The object, which was comprised of 460 000 atoms, incorporated a variety of designs that should make it useful in further study in the field.

A video describing the object and its model can be seen below along with further information about the research, which was published in the journal Proceedings of the National Academy of Sciences:

Finally having proof of the atomic precision of the DNA manufactured objects is a huge confirmation for the hopes of bottom-up manufacturing.

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Sale of A123 Systems to Chinese-Owned Company Points to Futility of Nationalistic Technology Investments

The continuing saga of A123 Systems Inc. has culminated this past week in most of its assets being sold for US $256.6 million to the Chinese-owned Wanxiang America Corporation, an auto parts conglomerate.

The sale of A123 to Wanxiang had been in the works since this past August. But because of strong opposition from Washington politicians the final sale was delayed.  The main objection to the sale centered on the fact that the US government had floated A123 a “grant” for $250 million as recently as 2009 to expand the company’s production capacity.

Why the US government would give a grant to expand the company’s production capacity when the market problem it faced was that its main customer wasn’t selling any of its own products is probably a worthy discussion. However, combating crony capitalism with more crony capitalism, which some U.S. Senators seemed engaged in with their fight to block the sale, hardly seems to be a solution.

There were concerted efforts by U.S.-based Johnson Controls Inc. to purchase the bulk of A123’s assets. But the prospect of paying Wanxiang back the $75 million the Chinese company had loaned A123 before A123's bankruptcy likely poured cold water on any other plausible deal.

For anyone seeking—from a U.S. nationalistic perspective—some sort of positive takeaway from the deal perhaps comfort can be taken in the news that Navitas Systems, an Illinois battery company, will get all of A123’s defense contracts.

I am sure that this sale is a bitter pill to swallow, especially for those who believe that national nanotechnology investments will translate into new jobs and economic growth.  We have already seen how, after years of government investment in nanotechnology research and commercialization, the benefiting companies can be easily picked up for a song. Not just by shrewd investors, but by other governments.

The last U.S.-based nanotechnology-based Li-ion battery company to go bankrupt (Ener1) ended up being purchased by a Russian interest. Even the former CEO of Ener1 served as an advisor to Wanxiang in its purchase of the A123 assets.

Governments around the world are going to have to come to terms with the notion that investments in technology have a slim chance of producing jobs and economic growth within the region that happens to make those investments. It may in fact be the only the chance, but in the current innovation framework those chances remain slim. A123 beat the odds; it managed to turn a university research project into a commercial product. There just wasn’t any market for the product.

What governments should be doing is reexamining the entire innovation infrastructure. Apparently, they have not done this to date because there has been no pressure to do so. Sure, technology that has been languishing for years in research labs never seems to get to market, but nobody misses what wasn’t there in the first place. But once it leaves the lab for the marketplace there's something to miss: the millions—even billions—being spent without much to show for it.

Nanostructure Material Makes Organic Solar Cells 175 Percent More Efficient in Lab

Organic solar cells have remained a bit of a commercial disappointment. There are a number of reasons for this. Some point to the use of the expensive indium-tin-oxide (ITO) in the electrodes.  Still others believe the use of fullerenes as electron acceptors has kept organic solar cells from achieving wider commercial adoption.

Researchers at Princeton University, led by electrical engineer Stephen Chou, have developed a nanostructure that promises an economical way to nearly triple the efficiency of organic solar cells and garner them a stronger foothold in the commercial market.

The Princeton research (“Ultrathin, high-efficiency, broad-band, omni-acceptance, organic solar cells enhanced by plasmonic cavity with subwavelength hole array”), which was published in the journal Optics Express, claims to have developed a nansostructured sandwich of metal and plastic that increases the efficiency of the solar cells by 175 percent. The nanostructure manages this feat by reducing the amount of light reflecting off the cell and increasing the amount of light captured by it.

The “sandwich” as it has been dubbed is in fact a subwavelength plasmonic cavity. Plasmonics exploits the phenomenon of "photons striking small, metallic structures to create plasmons, which are oscillations of electron density in the metal." The subwavelength plasmonic cavity--or sandwich—at once dampens the reflection of light and traps light.

The result was a solar cell that reflects a mere 4 percent and absorbs 96 percent of the light that hits it. The researchers claim to have demonstrated a solar cell with this design that produces 52 percent higher efficiency in converting light to electrical energy than conventional solar cells.

These figures are for direct sunlight. On cloudy days, when sunlight hits the solar cells at an angle, the numbers are even more astounding. Efficiency is increased by an additional 81 percent over conventional solar cells, with a total increase of 175 percent.

The breakthrough of the design is the top layer of the sandwich, which is a metal mesh only 30 nanometers thick. The holes in the mesh are only 175 nanometers in diameter and are placed 25 nanometers apart. This first “window” layer means that the ITO typically used in this layer can be omitted, leading to a far cheaper design.

The bottom layer is made of the same metal films found in conventional solar cells. The top and the bottom layers are very close to each other separated only by a thin semiconducting material (silicon, plastic or gallium arsenide can be used). In the Princeton prototype an 85-nanometer-thick layer of plastic was used.

Because the design can use a variety of silicon materials, the researchers believe that it could be used in traditional silicon solar panels and reduce the thickness of the panels by a thousand fold.

Here we have a design that both significantly reduces manufacturing costs and dramatically increases energy efficiency. That’s what we call a win-win in solar cell technology.

Carbon Nanotubes Show Promise in Neural Engineering

Research this summer out of Rice University showed that newly developed nanoparticles could be an effective emergency treatment for traumatic brain injuries.

Now researchers at Duke University have come up with an ultra-pure carbon nanotube—dubbed “few-walled carbon nanotubes” (a reference to the single-walled and multi-walled varieties)—that can regulate excessive levels of chloride in nerve cells.

The research, which was published in the Wiley journal Small (“Highly Conductive Carbon Nanotube Matrix Accelerates Developmental Chloride Extrusion in Central Nervous System Neurons by Increased Expression of Chloride Transporter KCC”), was specifically focused on the impact of carbon nanotubes on neurons.

Carbon nanotubes have been a source of great interest for neuroscientists because of the material’s electrical and mechanical properties. The hope has been that those properties could be exploited in creating devices that could interface with nervous tissue. However, previous experiments with neurons and carbon nanotubes came up with mixed results, largely due to the impurities within the carbon nanotubes.

The Duke team found that by employing the high purity few-walled carbon nanotubes that not only did the nanotubes not harm the nerve cells but they actually seemed to nourish the neurons.

"Previous studies have looked at the behavior of carbon nanotubes on neurons. However, the impurity in the nanotubes significantly affected the results. After we developed pure few-walled carbon nanotubes in our lab, we discovered that nanotubes actually accelerated the growth of the neuronal cells significantly," said Jie Liu, Professor of Chemistry at Duke University and senior author of the study, in a press release.

This accelerated growth of neuronal cells also can regulate chloride levels in the nerve cells. Excessive amounts of chloride can disrupt a neuron's proper function. Epilepsy, chronic pain, and traumatic brain injury all involve this kind of neural circuit damage.

The human body typically regulates these chloride levels by producing a protein known as KCC2 (chloride-extruding transporter, potassium chloride cotransporter 2). As nerve cells mature their KCC2 levels increase and their ability to regulate chloride levels becomes more powerful. By exposing the nerve cells to the carbon nanotubes the researchers found that neurons matured faster and the chloride levels in them dropped rapidly.

This research does not appear intended to serve as a treatment in itself but a step towards developing neural engineering devices that employ the carbon nanotubes.

Lead author Wolfgang Liedtke, associate professor of medicine and neurobiology at Duke, adds: "We hope that carbon nanotubes will work as well in injured nerves as they did in our study of developing neurons...The use of carbon nanotubes is just in its infancy, and we are excited to be part of a developing field with so much potential."

Hyperbolic Reporting on Nanotechnology in Food Wreaks Havoc

This past summer Nature published an article outlining some of the causes for the recent bombing attacks on nanotechnology labs. At the time, I suggested on this blog that most of the article scanned about right except for one notable omission: poor reporting on nanotechnology in the mainstream press. 

One of the clearest indications of how this bad journalism has misinformed the public was when the terrorist group “Individuals Tending Toward the Savage,” which attacked a nanotech lab in Mexico, made public its raison d’etre. In it they demonstrated a truly distorted idea of what nanotechnology is and what scientists working on the nansoscale are doing. In their letter they demonstrated the misapprehension that the nanotechnology of today threatens us with the prospect of “grey goo” as tiny nanobots eat the world and leave behind a waste product of goo.

I laid at least part of the blame for this terrorist group confusing science with science fiction at the feet of mainstream journalists, who, not being familiar with the field, mistake Michael Crichton’s Prey with Eric Drexler’s Engines of Creation. It’s probably not fair to say they are confused; it’s more likely the case they have never heard of the latter.

The perfect example of this comes in an article appearing on the website for the local PBS TV station in Los Angeles (KCET). In it the author, explains that Crichton’s Prey is “actually turning out to be more prescient than pessimistic.” The author based his conclusion on article he read in a publication called “E-The Environmental Magazine”.

While that article is filled with a bit more hyperbole and conjecture presented as cold-hard fact than I care for, at least it has an inkling of what a nanoparticle is. But the writer for KCET doesn’t even get that. He believes “nanoparticles” are just another way of saying, “small robots that can move about your body as they please.”

 I am sorry, but nanoparticles are not small robots wandering around in our bodies delivering nutrients, or “attacking from the insides.” Let’s just start there.

Now onto the more reality-based arguments presented in both the E Magazine and KCET articles.  We get this in the E Magazine article: “There is no doubt that nanoparticles are in the food supply and have been for years.” As proof of this statement, the author references research that found carbon nanoparticles in “caramelized sugar, including bread and corn flakes”.

If you have ever heated sugar in a chemistry class you probably recall that carbon, oxygen and hydrogen in the sugar separate. The oxygen and hydrogen burn off leaving carbon behind—probably in nanoscale particles. Is this some deliberate attempt by unscrupulous food company scientists to put nanoparticles (oops, I mean nanobots) into the food supply? Probably not. But if the E Magazine editor wants real proof of nanoparticles in our food, she need only turn to mayonnaise, which is an emulsion of lipids and proteins that are on the nanoscale. I wonder if over 250 years of mankind eating mayonnaise passes the long-term-health-risk test?

Two years ago, the UK government's House of Lords Science and Technology Committee decided they were going to get to the bottom of this nanotechnology-in-food issue. They put together a panel of experts, interviewed experts from all aspects of the issue and concluded that they couldn’t really say to what extent nanotechnology is used in our food.

But I am sure that the author at E Magazine understands the issue better than some UK government committee (it’s likely just some conspiracy anyway to cover up the entire issue) and the reporter can come to conclusions that were not possible for the experts.

One clear conclusion we can make from all of this, however, is that the reporter at E Magazine, in an attempt to heighten the fear factor, got another reporter to believe that nanoscale robots were circulating through our body doing some good, but also possibly some unknown harm. Now there is a much wider swath of the general public that believes nanoscientists are producing nanobots that will result in some scenario from the novel Prey.

We’ve already witnessed the damage, maiming and destruction that one small group of people can wreak when they don’t really understand what nanotechnology is. At present that violence far exceeds any harm that nanotechnology has perpetrated upon anyone. Maybe we should be hyping just how careless and misguided the coverage of the subject is and the harm that may be doing.

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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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