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Nanoparticles and Sunshine Split Water Molecule for Hydrogen Gas

Just in case you believed that companies announce some nano-related research for a bit of buzz and then abandon the research, I am here to tell you that is not always the case. Back in March, I covered Santa Barbara, Calif.-based Hypersolar’s grand proposal for producing hydrogen gas in a zero-carbon process from wastewater.

To Hypersolar’s credit they have decided to chronicle their achievements (and perhaps failures) in a development process in which there are no guarantees of success. In the video below, Tim Young, CEO of HyperSolar, narrates a proof of concept prototype that demonstrates the effectiveness of the process. As Young explains, an inexpensive plastic baggy was filled with wastewater from a paper mill and on the bottom of the baggy is a small-scale solar device that is protected with Hypersolar’s polymer coating. Add sunlight, and hydrogen comes bubbling up.

“A big hurdle in using a solar to fuel conversion process is the stabilization of the semiconductor material against photocorrosion,” explains Young in a company press release announcing the development. “Our development of an efficient and low cost protective polymer coating that also allows good electrical conductivity is a significant achievement in our development of a cost effective means for using the power of the Sun to extract renewable hydrogen from water.”

Young suggests in the video that the small-scale solar device used in the prototype will be replaced with Hypersolar’s nanoparticles, which can be mass-produced and lead to large-scale production of hydrogen gas.

“The implications of our technology may be world changing,” claims Young in another company press release. “If we can successfully complete the development of a low cost, highly efficient solar powered water-splitting nanoparticle, we can use readily available seawater, runoff water, river water, or wastewater, to produce large quantities of hydrogen fuel to power the world. When the hydrogen fuel is used in fuel cells or combustion, clean water (pure H2O) returns back to the Earth. HyperSolar is making steady technical progress to enable this vision.”

It should be interesting to see whether this mimicking of photosynthesis will be able to compete with processes that simply replace platinum with a nanomaterial as a catalyst in the tried and tested electrocatalytic processes for producing hydrogen gas. 

Samsung Creates a Graphene Transistor with a Band Gap and Electron Mobility

 

Getting a graphene-based transistor to turn on and off has typically meant sacrificing its incredible electron mobility in the bargain. And the truth of it is that graphene's electron mobility—which is 200 times greater than that of silicon—is what has made it such an attractive alternative in a post silicon world.

Lately, research has been focused on coming up with different varieties of graphene better suited to electronics applications. A so-called “graphene monoxide (GMO)” looks promising, and an isotopically engineered graphene could find use in heat management applications for electronics. 

Researchers at the Samsung Advanced Institute of Technology have taken a different approach. Instead of altering the graphene, they have re-engineered the basic operating principles of digital switches.

They developed a three-terminal active device (described in the journal Science) in which the key feature is a “an atomically sharp interface between graphene and hydrogenated silicon.” The device, capable of switching on and off via a Schottky barrier that controls the flow of current by changing its height, does so without the graphene losing any of its precious electron mobility. 

Whenever you demonstrate a transistor, you get the usual refrain of: “Let me know when you make a simple logic circuit.” Ask and it shall be given. The Samsung researchers have reported the most basic logic gate (inverter) and logic circuits (half-adder) as part of their research, and demonstrated a basic operation (adding).

With nine patents already filed around this research, maybe this will be the way forward in bringing graphene to commercial electronics.

Nano Devices Based on Block Copolymers Could Lead to Next Generation of Computing

 

As far back as 2007 in the ITRS roadmap, the use of block copolymers has been targeted for reducing chip size. Since then they have been used to push the possibilities of self-assembled photoresists  as well as improve insulation within chips. 

During this period, researchers at CRANN, the nanoscience institute based at Trinity College Dublin—which partners with University College Cork (UCC)—along with researchers from the University of Wisconsin and Intel’s Researchers in Residence based in CRANN—namely, Professor Mick Morris of UCC—have been characterizing the block copolymer to better understand its self-assembling properties.

The results from the research, which were published in the journal Nanoscale, has demonstrated a method for fabricating large-area arrays of silicon nanowires through directed self-assembly of block copolymer nanopatterns that can be easily integrated into current manufacturing techniques.

In a press release issued by the Science Foundation of Ireland, Morris commented,  “The potential of our research is extremely exciting and reflects many years of hard work. This is the first time that anyone has demonstrated that large areas of nano-electronic devices can be developed in this fashion and highlights a pathway to commercial applications. I am looking forward to exploring commercial opportunities to further advance our work.”

Those associated with the project believe that the development could revolutionize the manufacturing of silicon chips and lead to a new generation of computers and real-time 3D video processing.

These types of claims are pretty regular in press releases covering this kind of research. In this case, however, given how deeply involved Intel was in the research one can’t help but give it a bit more credence than usual.

Graphene Combined with Quantum Dots Result in Efficient Photodetector

Graphene research has been turning increasingly towards its potential in optoelectronic applications.  This is not a surprise because graphene’s optical properties are as astounding as its electrical conductivity capabilities.

But just as graphene has the glaring Achilles Heel in electronics applications of lacking a band gap, it also suffers a couple of fatal flaws in optoelectronics. For example, while nearly every single photon the material absorbs generates an electron-hole pair, it doesn’t really absorb that much light. According to some estimates, it absorbs less than 3 percent of the photons falling on it.

So, researchers at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain thought about the possibility of combining graphene with quantum dots to see if they couldn’t overcome graphene’s shortcomings.

The research, which was published in the journal Nature Nanotechnology last week,  demonstrated that the combination of the two nanomaterials did the trick. Instead of absorbing just 3 percent of the light that hits it, the graphene/quantum dot hybrid material is capable of absorbing 25 percent of the light falling on it. This new absorption capability is due to the quantum dots, and when you combine that with the graphene’s ability to make every photon into an electron-hole pair, the potential for generating current is significant.

"In our work, we managed to successfully combine graphene with semiconducting nanocrystals to create complete new functionalities in terms of light sensing and light conversion to electricity," Gerasimos Konstantatos, co-leader of the team at the Institute of Photonic Sciences (ICFO) in Barcelona, told physicsworld.com. "In particular, we are looking at placing our photodetectors on ultrathin and flexible substrates or integrating the devices into existing computer chips and cameras," added co-leader Frank Koppens in the same article.

The researchers offer a range of applications for the graphene-and-quantum-dot combination, including digital cameras and sensors. But it seems the researchers seem particularly excited about one application in particular. They expect the material will be used for night-vision technologies in automobiles—an application I have never heard trotted out before in relation to nanotech.

"We expect that most cars will be equipped with night-vision systems in the near future and our arrays could form the basis of these," Koppens told physicsworld.com.

Nanostructured Silicon Anodes Improve, But Is It Enough for EVs?

Lithium-ion (Li-ion) batteries are ubiquitous but flawed, especially for electric vehicle applications. The problem has been poor charge life. But researchers have shown that if you replace the graphite on the anodes with silicon, the charge can be increased by a factor of ten. Problem is that after a few charge-discharge cycles the silicon cracks and becomes inoperable from the expansion and contraction of the material.

One solution: nanostructured silicon anodes that improve on the traditional silicon variety in this area of charge-discharge cycles. While there’s been improvement from silicon’s poor performance, the nanostructured variety still doesn’t measure up to plain old graphite in this regard.

That's a shame, because silicon anodes just crush graphite when it comes charge life. So, if there were a way to get silicon to work, it would offer some considerable benefits to Li-ion batteries, and nanotechnology has been the prayer. At least one commercial interest believes that the nano-based solution has already been developed for enabling silicon anodes to survive a large number of charge-discharge cycles.

Now research, led by Yi Cui of Stanford, who holds the distinction of having the most cited paper at ACS journal Nano Letters over the past 10 years, has come up with a nanostructured silicon capable of 6,000 cycles while maintaining 85% of its capacity.

That sounds good…for lithium-ion batteries, but Cui demonstrated just last year that potassium or sodium ions in place of the lithium variety can create batteries capable of 40,000 cycles while maintaining 83% of its charge. The issue there was that they had the cathode sorted but hadn’t yet developed the anode.

Then there's the issue of applications. The sodium- or potassium-based ion battery was targeted for large-scale energy storage on the electrical grid. Again, the Li-ion battery Cui and his colleagues has developed is being targeted for electric vehicle applications.

Cui himself started a company, Amprius, in which he was going to use his silicon nanowire anode technology with the aim of doubling the energy density of Li-ion batteries. I hope the company succeeds, but even if you achieve a doubling of energy density in the Li-ion battery you still only get to 400Wh/kg for powering vehicles. According to Stephen Chu, Li-ion batteries will need to get to 1000Wh/kg to really be competitive with fossil fuel-powered vehicles. Why can’t powering laptops be good enough for these batteries?

Nanocatalyst Splits Water Molecules at a Fraction the Cost of Platinum

Nanotechnology-based solutions for improving fuel cells have fallen a bit short of expectations. So  recent research has focused instead on using nanotech to produce hydrogen gas for existing fuel cells more cheaply and efficiently.

Some of these solutions—like those from University of California, San Diego, or those of Angela Belcher of MIT—have been aimed at breaking down a water molecule into its constituent parts of hydrogen and oxygen by replicating photosynthesis. This is really cutting edge stuff and pretty far removed from the process currently used to create hydrogen gas, which involves applying electricity to water in the presence of a catalyst.

One of the main problems with this current method has been the cost of platinum, which is the best material to serve as a catalyst for the process. With platinum going for about $50,000 per kilogram, it’s pretty clear why this gets to be a very expensive process.

To address this issue researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have developed a new nanomaterial that can duplicate the capabilities of platinum at a fraction of the cost.

“We wanted to design an optimal catalyst with high activity and low costs that could generate hydrogen as a high-density, clean energy source,” said Brookhaven Lab chemist Kotaro Sasaki in a press release covering the research. “We discovered this exciting compound that actually outperformed our expectations.”

The researchers—whose results were initially published online yesterday in the journal Angewandte Chemie International Edition—determined early on that nickel can take the reactive place of platinum, but didn’t have the same electron density. While the introduction of metallic molybdenum to the nickel improved its reactivity, it still wasn’t up to platinum standards.

Sasaki and his colleagues believed that they could push the nickel-molybdenum material up to platinum levels by applying nitrogen, based on the understanding that this had been done with bulk materials. They weren’t quite sure what to expect when you applied the nitrogen to nanoscale nickel-molybdenum but they suspected that it would change the structure of the material into discrete, sphere-like nanostructures. That’s not what they got.

To the surprise of the researchers, the infusing of nitrogen with nickel-molybdenum material produced two-dimensional nanosheets.

“Despite the fact that metal nitrides have been extensively used, this is the first example of one forming a nanosheet,” said research associate Wei-Fu Chen, the paper’s lead author in the Lab’s press release. “Nitrogen made a huge difference – it expanded the lattice of nickel-molybdenum, increased its electron density, made an electronic structure approaching that of noble metals, and prevented corrosion.”

While the researchers are realistic in their understanding that this new catalyst doesn’t answer all the issues facing the production of hydrogen gas, it does have the advantage over other solutions in that it can be directly substituted into current processes that use platinum as a catalyst to cut the costs dramatically. Whether this will usher in the age of the hydrogen economy is impossible to say, but it's a step in the right direction.

Nanogenerators Easier and Cheaper to Produce than Ever Before

Professor Zhong Lin Wang at Georgia Tech has been championing his work in exploiting the piezoelectric qualities of zinc oxide nanowires for years now with his so-called "nanogenerators".

Now researchers at the Korea Advanced Institute of Science and Technology  (KAIST) have taken up the mantle of Wang’s work by creating a piezoelectric “nanogenerator” more easily and cheaply than ever before.

The research, which was initially published in the Wiley journal Advanced Materials, produced a piezoelectric nanocomposite through relatively simple processes such as spin-casting and the bar-coating method. So this new generation of “nanogenerators” is not restricted by a complicated and high-cost process or even size.

Even Wang himself is impressed by this work. “This exciting result first introduces a nanocomposite material into the self-powered energy system, and therefore it can expand the feasibility of nanogenerator in consumer electronics, ubiquitous sensor networks, and wearable clothes," says Wang.

The lead researcher on this project, Keon Jae Lee, a Professor at the Department of Materials Science and Engineering at KAIST, has a comprehensive website that covers much of the work.

One of the videos from that website (below) manages to demonstrate just how uncomplicated the process is to create this nanocomposite and shows how it works in generating an electric charge from the movement of a finger.

While Wang has been expert at getting this research into the media, it hasn't yet found itself in commercial products. It should be interesting to see if these manufacturing simplifications and cost reductions will help push this technology into consumer electronics where Wang always envisioned it could be.

NIST Develops Laser Feedback Method for Nudging Nanoparticles Just Enough

The example of the Lycurgus Cup, as a paradigm of nanotechnology, has always bothered me. Yes, the glass of the cup changes colors depending on the light because of the presence of nanoparticles, but it's not really nanotechnology. While the  Romans knew the process that would make this glass, they didn’t know why it performed the way it did. Without that kind of knowledge—and the concomitant ability to manipulate an effect—what you have is at most craft, and not science.

That's the reason many trace the real beginning of nanotechnology to the development of microscopy tools like the scanning tunneling microscope (STM). Without the array of tools we have for seeing, measuring and manipulating the world on the scale of atoms and molecules, there would have been little to no advancement in nanotechnology. In other words, nanotechnology is not just the world of the very small but having the tools to know what we’re doing at that scale and setting about to do it.

Now researchers at the National Institute of Standards & Technology (NIST) have added a new tool to the arsenal that should allow researchers to better user lasers in manipulating nanoparticles inside biological cells without damaging them. The researchers have developed a control and feedback system that lets the laser nudge nanoparticles to exactly where they are needed for analysis.

In the NIST press release covering the technology, Thomas LeBrun, one of the researchers on the project, explains: "You can think of it like attracting moths in the dark with a flashlight. A moth is naturally attracted to the flashlight beam and will follow it even as the moth flutters around apparently at random. We follow the fluttering particle with our flashlight beam as the particle is pushed around by the neighboring molecules in the fluid. We make the light brighter when it gets too far off course, and we turn the light off when it is where we want it to be. This lets us maximize the time that the nanoparticle is under our control while minimizing the time that the beam is on, increasing the particle's lifetime in the trap."

The researchers report two key results:

  • 100-nanometer gold particles remained trapped 26 times longer than had been seen in previous experiments
  • Silica particles 350 nanometers in diameter lasted 22 times longer, but with the average beam power reduced by 33 percent.

LeBrun characterizes this development as pushing the field an order of magnitude further than it was before. He says the researchers will now begin work in building complex nanoscale devices and testing nanoparticles as sensors and drugs in living cells.

Nanocomposite Fillings Kill Bacteria and Regenerate the Tooth

Earlier this year, I was teased by news that graphene could be ‘tattooed’ to one’s tooth to detect harmful bacteria. I say teased because the bacteria that could be detected was not the Streptococcus mutans bacteria that causes tooth decay. Instead the device could detect just about every other bacteria except that one. So, what appeared to be a story that might be able to redeem me in the eyes of the dental community—after I echoed others’ doubts about the efficacy of a nanofilm in promoting cell growth in decayed teeth—just wasn’t the opportunity I had hoped for.

This week, however, researchers at the University of Maryland have offered up a technology that should be of keen interest to the dentists of the world, and those who visit them. The researchers have developed a nanocomposite that can be used not only as a filling for the cavity, but also can kill any remaining bacteria in the tooth and regenerate that tooth’s structure that had been lost due to the decay. You can access a PDF file that offers up a poster presentation of the research here.

The basis of the nanocomposite are calcium phosphate nanoparticles that regenerate tooth minerals. The ingredient that kills off the remaining bacteria in the tooth is made up of silver nanoparticles and quaternary ammonium along with a high pH. According to the news release, the alkaline pH is the feature that limits the acid production by the bacteria. This begs the question: why not just develop a mouthwash with these ingredients so you don’t need the cavity filling in the first place?

One answer may be the use of silver nanoparticles, which are not without some controversy when associated with anything that might be consumed by humans. Sure enough, just a quick perusal to see how this story was being covered turned up a blog called “Beyond Pesticides” that offered up this headline: “New Dental Fillings Utilize Controversial Nanotechnology to Kill Bacteria”. The blog goes into some detail about the potential risks of silver nanoparticles.

The researchers are continuing with their animal and human testing with the nanocomposite. Given that some sectors of the public are concerned about the potential risks of silver nanoparticles, they should probably take a look at the issue as part of their research.

President's Council Wants a Few More Things from the National Nanotechnology Initiative

Just four months after the National Nanotechnology Initiative (NNI) responded to the President’s Council of Advisors on Science and Technology’s (PCAST) 2010 report on the status of nanotechnology, PCAST has offered up a new assessment.

While the PCAST report on the NNI in 2010 wanted to see greater efforts towards commercialization and some attempt to address environmental, health and safety (EHS) concerns, this time they just wanted to see how well the NNI had done in meeting their previous recommendations.

In the Whitehouse.gov blog covering the announcement it seems PCAST are satisfied:

“PCAST found that the Federal agencies in the NNI have made substantial progress in addressing many of the 2010 recommendations that were aimed at maintaining U.S. leadership in nanotechnology… The PCAST assessment particularly commends the expanded efforts of the NNCO in the area of commercialization and coordination with industry, and the NNCO’s release of a focused research strategy for addressing environmental, health, and safety (EHS) implications of nanotechnology.”

Okay, pat on the back, job well done…uh, wait, there are still some new recommendations that PCAST would like to see addressed.  You can find them in the PDF of the full report on page vii. They fall into the areas of strategic planning, program management, metrics for assessing nanotechnology’s commercial and societal impacts, and…wait for it…increased support for EHS research.

Additional support for EHS research might be a required element for every PCAST report in the future. More interesting to me, however, is this continued emphasis on improved “metrics for assessing nanotechnology’s commercial and societal impacts.”

It seems to me that this is an area in which everyone from governments to corporations wants a formula that will churn out a sense of what kind of impact nanotechnology is really having. While nobody is satisfied with the metrics that we have,  I would suggest that there are few number-counting options that will really be able to sort out the full impact of nanotechnology. But again, it should be interesting to see what they come up with.

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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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