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Gold Nanoparticles Enable Simple and Sensitive Sensor for Early Disease Detection

When it comes to nanosensors for medical diagnostics, gold nanoparticles are often the first choice for enabling early disease detection. This is due to gold nanoparticles’ ability to detect biomarkers at very low concentrations. They undergo intense color changes when in the presence of certain targets.

Just last year, researchers from London Centre for Nanotechnology at Imperial College London used gold nanoparticles and plasmonics to create a biosensor capable of detecting minute amounts of a biomarker.

Now, in research led by Professor Warren Chan of the University of Toronto’s Institute of Biomaterials and Biomedical Engineering (IBBME), gold nanoparticles’ capabilities have been exploited again to create a simple but highly sensitive diagnostic tool for detecting diseases.

The typical design for other gold nanoparticle-based biosensors involves DNA strands being attached to the particles. In these methods, the gold nanoparticles clump together when in the presence of a target gene turning the sample blue.

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Nanotube Membrane Could Revolutionize Osmotic Power

Two years ago, Stanford University researcher Yi Cui took a break from his work on solving the silicon-versus-graphite conundrum of anodes in Lithium-ion batteries to look into an alternative method for generating electricity that has become known as pressure-retarded osmosis.

Pressure-retarded osmosis exploits the difference in salinity between fresh water and salt water to generate electricity. Norway-based Statkraft has been a leading commercial proponent of the technology, building its first pilot plant in 2009.

Despite new plants being planned and this alternative energy source theoretically capable of generating 1 terawatt—the equivalent of 1000 nuclear reactors—a group of European researchers believed the technology was still not a truly viable energy source.

Now researchers at the Institut Lumière Matière in Lyon (CNRS/Université Claude Bernard Lyon 1), in collaboration with the Institut Néel (CNRS) claim to have developed a new membrane technology that will make new pressure-retarded systems 1000 times more efficient than today's systems.

The researchers didn’t set out to create a new membrane. The original aim of the research was just to measure dynamics of fluids confined in nanometric spaces. The research, which was published in the journal Nature ("Giant osmotic energy conversion measured in a single transmembrane boron-nitride nanotube"), did succeed in achieving the world’s first measurement of osmotic flow through a single nanotube. However, in achieving their initial aim they also managed to create a membrane design that could revolutionize the nascent industry.

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Nano Beads of Silicon Could String Together Li-ion Batteries of the Future

Traditional graphite-based anodes for Lithium-ion (Li-ion) batteries just don’t measure up in terms of charge life for the demands that are being put on them in today’s personal gadget applications. Silicon-based anodes as an alternative have demonstrated drastically improved charge life, but they begin to crack after a relatively few charge-discharge cycles.

As a result, much research has been devoted to finding nanomaterials that have the improved charge life of silicon but also the ability to withstand numerous charge-discharge cycles of graphite. Nanostructured silicon has been the nanomaterial that has been looked at the longest for achieving this dual aim.

Despite all the efforts, it wasn’t until last year that Yi Cui of Stanford and SLAC found a solution that consisted of a double-walled silicon nanotube coated with a thin layer of silicon oxide. This design was capable of storing 10 times more charge than graphite anodes and could survive 6000 charge-discharge cycles.

While Cui has been simplifying the process for making the double-wall silicon nanotubes, researchers at the University of Maryland have taken a different material approach. YuHuang Wang, an assistant professor of chemistry and biochemistry, and his colleagues have successfully grown tiny beads of silicon on a carbon nanotube to serve as an anode in a Li-ion battery.

The research, which was published in the journal ACS Nano (“A Beaded-String Silicon Anode”), attached a molecule sometimes used in food flavoring to carbon nanotubes less than 50 nanometers wide. After flooding the molecule and carbon nanotube with silicon gas, the molecule caused beads of silicon to grow on the nanotube.

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Graphene Can Create "Hot Carrier" Cells for Photovoltaics

Graphene’s potential applications in photovoltaics (PVs) have remained fairly limited. Nanomaterials of nearly every stripe, including quantum dots, nanowires and carbon nanotubes, have offered alternatives in the solar collecting cells of PVs. But research has really only offered graphene as a replacement to indium-tin-oxide (ITO) used in the electrodes for organic solar cells.

Now researchers at the Barcelona, Spain-based Institute of Photonic Science (ICFO), in collaboration with the Massachusetts Institute of Technology, Max Planck Institute for Polymer Research in Germany and Graphenea S.L. Donostia-in San Sebastian, Spain have taken some initial steps in using graphene in the conversion and the conduction layers of a PV cell.

The research, which was published in the journal Nature Physics (“Photoexcitation cascade and multiple hot-carrier generation in graphene”), has demonstrated that graphene is capable of converting one photon into multiple electrons, leading to electric current.

Until now, researchers had been looking at quantum dots to generate electron multiplication or creating so-called “hot carrier” cells in PVs.  While this line of research has gained some skeptics, it has been pursued for nearly a decade. The international team in this latest research has demonstrated that graphene can be used to create these hot carrier cells.

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Why Did NanoInk Go Bust?

One of the United State’s first nanotechnology companies, NanoInk, has gone belly up, joining a host of high-profile nanotechnology-based companies that have shuttered their doors in the last 12 months: Konarka, A123 Systems and Ener1.

These other three companies were all tied to the energy markets (solar in the case of Konarka and batteries for both A123 and Ener1), which are typically volatile, with a fair number of shuttered businesses dotting their landscapes. But NanoInk is a venerable old company in comparison to these other three and is more in what could be characterized as the “picks-and-shovels” side of the nanotechnology business, microscopy tools. NanoInk had been around so long that they were becoming known for their charity work in bringing nanotechnology to the Third World

So, what happened? The news tells us that NanoInk’s primary financial backer, Ann Lurie, pulled the plug on her 10-year and $150-million life support of the company. After a decade of showing little return on her investment, Lurie decided that enough was enough. But that’s like explaining that a patient died because their heart stopped. What caused the heart to stop?

The technology foundation of NanoInk was an atomic force microscope-based dip-pen to execute lithography on the nanoscale. This so-called nanolithography would create nanostructures by delivering 'ink' via capillary transport from the AFM tip to a surface. One thing that always seemed problematic with this technology was that it wasn’t really scalable.

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Carbon Nanotube-Based Thin Film Creates Hybrid Organic/Silicon Solar Cells

Research into improving photovoltaics (PVs) is one of the most dynamic areas of nanotechnology. The range of nanomaterials and approaches to using them for increasing the energy conversion efficiency and lowering the cost of PVs are impressive.

Quantum dots have generated some of the more attractive approaches to creating solar cells with extremely high conversion efficiencies. Even the wonder material graphene has gotten into the act recently by offering an inexpensive alternative to indium-tin-oxide (ITO) used in the electrodes of organic solar cells.

But industry adoption of nanotechnology-based solar power solutions has been rocky, epitomized by last year's bankruptcy of Konarka. Often in emerging technologies—and perhaps in the case of nano-enabled PVs—it’s better not to reinvent the wheel but just figure out a way for it to roll a bit better.

To this end researchers at Yale University have developed a carbon nanotube-based thin film that, when applied to today’s crystalline silicon solar cells, create a hybrid carbon/silicon solar cells with far greater power-conversion efficiency than they currently possess.

“Our approach bridges the cost-effectiveness and excellent electrical and optical properties of novel nanomaterials with well-established, high efficiency silicon solar cell technologies,” said André D. Taylor, assistant professor of chemical and environmental engineering at Yale and a principal investigator of the research, in a university press release.

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Nanocapsule Could Serve as Both Vaccine and Cure for a Hangover

Researchers at UCLA have developed a nanoscale-polymer capsule capable of containing two complimentary enzymes to create a pill that helps the body quickly eliminate the effects of a hangover—an “anti-hangover pill”, if you will.

If my own hangover this morning is any indication, the news of this research is likely to capture the interest of the general public and generate a bit more interest in the field of nanotechnology.

Yunfeng Lu, a professor of chemical and biomolecular engineering at UCLA, and his colleagues described their nanoscale pill in the journal Nature Nanotechnology (“Biomimetic enzyme nanocomplexes and their use as antidotes and preventive measures for alcohol intoxication”).  Look at that title again—not only are they claiming the pill could serve as antidote for a hangover, but it might also be used to prevent them in the first place.

Lu and his colleagues attempted to mimic the body's reaction to hangovers by combining two enzymes that carry out different functions. Together they eliminate the toxins of the alcohol.

The first, alcohol oxidase, supports the body’s oxidation of alcohol. The unfortunate side effect of this oxidation, however, is the production of hydrogen peroxide, which is itself toxic. So the pill contains another enzyme that transforms the hydrogen peroxide into water and oxygen.

“The pill acts in a way extremely similar to the way your liver does," Lu says in the university press release. "With further research, this discovery could be used as a preventative measure or antidote for alcohol intoxication."

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Christine Peterson Looks into the Future of Nanotechnology

I ran afoul of the Foresight Institute in my very first blog post here on the Spectrum website. The fiery response that post received from one of its members really should have come as no surprise to me based on the religious-like fervor Foresight members often exercise. Nonetheless, if pressed, I might have to concede it was invigorating to be so assaulted on my very first blog post here. So when I saw that there was a new video interview with co-founder and long-time President of the Foresight Institute, Christine Peterson, it seemed like a good opportunity to dive into the fray once again.

A little background might be helpful first. After my initial post that rankled at least one its members, I had another run-in with the Foresight folks about three years ago when I wrote about a sudden flurry of interest generated around the topic of “nanobots.”  I discussed Ray Kurzweil’s recent admission that his interest in the Singularity was at least partly motivated by his wish to resurrect his dead father. And I mentioned the addition of a new blogger to the Foresight blog, Nanodot.

The Nanodot blogger and Foresight President of that moment, J Storrs Hall, noticed the post and felt I needed a lesson in economics based on this comment of mine in the post:

“But if I may apply some dime-store psychology to this sudden surge of interest, it might be due to things just being so terrible [a reference to the economic crisis] at the moment were in. It is far better to imagine some day in the future when we can use nanobots to bring our lost loved ones back to life, or to press the button on our home-installed nanofactory that says “Ferrari.”

We can dream about that or face the grim realities of the now.”

I won't repeat my response to Storrs Hall’s economics lesson here. Suffice it to say that I believed he was minimizing the impact of the world’s worst economic crisis since the Great Depression by employing flimsy comparisons to Sci-fi doomsday scenarios. I think the last three years of suffering throughout the world supports my judgment that things were pretty terrible at that time.

While that exchange was mostly cordial--albeit challenging--the ensuing comments from other Foresight members became hostile and once again revealed how unhelpful religious-like fervor can be in discussions of technology.

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Commercial Applications for Graphene Begin to Emerge

Graphene is certainly the “wonder material” of the moment, surpassing the former bearer of that title—carbon nanotubes. To support this research, funding mechanisms around the world are cranking up to full throttle. Some large investments in the UK to secure its position as a “graphene hub” and the €1 billion the EU has poured into graphene research are just the most recent examples of this.

Presumably all this research and all this funding is intended—eventually—to lead to some commercial applications. Things appear to be moving in the right direction with some significant advances in the mass production of graphene (liquid phase, thermal exfoliation, and chemical vapor deposition, to name a few).

Then again, you can mass-produce sealing wax but there’s not a whole lot of demand for the material anymore. To see what cheap production of a nanomaterial gets you, just take a look at the huge capacity glut for multi-walled carbon nanotubes that have left producers begging for applications.

Even the so-called “patent surge” in graphene doesn’t promise much more than the old “patented nanomaterial and a prayer” sensibility that governed investment in the early 2000s. 

There remains a very real possibility at this stage that graphene funding will not produce new economic development for some regions any more than investments in carbon nanotubes did.

Nonetheless there are real applications for which graphene could be used today. Those applications may not be—at least immediately—in the electronics industry, desperate though it is to keep Moore’s Law alive for another generation, but in more mundane areas such as for membranes for natural gas processing or water purification.

With this landscape as the backdrop, the National Science Foundation (NSF) wanted to highlight Jessup, Md.-based Vorbeck Materials, which just received a grant from the NSF to bring its graphene-based technology to market.

According to the NSF press release, the company claims to be “one of the first (if not the first) graphene products to go to market.” In 2009, Vorbeck introduced its Vor-ink graphene-based conductive ink for electronics at the Printed Electronics Europe 2009 tradeshow.

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Quantum Dots Demonstrate a New Wrinkle in Enabling High-Efficiency Photovoltaics

Quantum dots have attracted a lot of interest for researchers in photovoltaics because of their claimed ability to achieve extraordinary conversion efficiencies.

Last year researchers at the University of Buffalo said they could reach 45-percent conversion efficiency with solar cells enabled by quantum dots. And for nearly a decade now quantum dots have even been proposed as a way to achieve electron multiplication or to create so-called “hot carrier” cells for reaching higher conversion rates. However, this line of research has earned some skeptics of late who dismiss the possibility that more than one electron-hole pair can be generated from one photon.

Now researchers at the National Renewable Energy Laboratory (NREL) in conjunction with an international team have demonstrated that quantum dots can self assemble onto nanowires in a way that once again promises improved conversion efficiencies for photovoltaics.

Among their key discoveries, which were published in the journal Nature MaterialsSelf-assembled Quantum Dots in a Nanowire System for Quantum Photonics,” was that the quantum dots self assemble at the apex of the gallium arsenide/aluminum gallium arsenide core/shell nanowire interface. Further the quantum dots can be positioned precisely relative to the center of the nanowire. When this precise positioning is combined with quantum dots’ ability to confine both the electrons and the holes, the possibilities for this approach look encouraging.

In high-energy materials, the electrons and holes would typically locate themselves at the lowest energy position. But because the quantum dots can create this quantum confinement the electrons and holes overlap so that they are confined within the quantum dot, which stays located at the high-energy position. The high-energy position for this material is the gallium-arsenide core. This location results in the quantum dots being extraordinarily bright while maintaining a narrow spectral range.

While Swiss scientists had proposed this quantum confinement previously, no one quite believed them, according to Jun-Wei Luo, one of the co-authors of the study. This disbelief set Luo onto developing the quantum-dot-in-nanowire system that validated the previous research. While using NREL’s supercomputer he determined that despite the fact that the band edges were formed by the gallium Arsenide core, the aluminum-rich edges provided the quantum confinement that is observed.

In addition to applications in photovoltaics, this development should impact any area in which the detection of electric and magnetic fields are involved.

Images: NREL



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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