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MIT Researchers Able to Control Properties of Nanowires as They Grow

Researchers at MIT have developed a method by which they can control the growth process of nanowires and thereby control the composition, structure, and even their resulting properties.

The MIT research team, led by Silvija Gradečak, assistant professor of materials science and engineering, followed the usual method of growing nanoparticles by using “seed” particles (metal nanoparticles), but in their experiments the researchers closely controlled the amount of gases used in the growth process.

The results, which were published in the journal Nano Letters, demonstrated that by controlling the gases interacting with the seed particles, the researchers were able to control the width and composition of the resulting nanowires.

Gradečak's team used an electron microscope to observe the effects that the gases were having on the growth process, and then the researchers adjusted the amount of gases to get the characteristics they wanted in terms of both structure and composition.

While the research team restricted their seed particles to indium nitride and indium gallium nitride, they say that the process will work with a variety of different materials.

Naturally, the goal of controlling the size and composition of nanowires is to change their properties. If you could fine tune the exact properties you wanted in a nanowire, you could use it in applications for which they are best suited.

The application that seems to be at the top of the list for the nanowires created by the MIT team is LED light bulbs. In this case, the nanowires would be used as a substrate replacing the expensive sapphire or silicon carbide typically used. Not only could the nanowires be a less expensive substrate, but they could also prove to be more efficient, according to Gradečak.

The varying diameters and structures could also make the nanowires useful in thermoelectric devices, in which waste heat can be turned into electricity. By changing the structure and thickness of the nanowires along their length, it’s possible to make them good conductors of electricity but bad conductors of heat, a much-desired property for thermoelectric power systems.

Construction Company Plans to Build a Space Elevator by 2050

When proponents of carbon nanotubes (CNTs) first introduced them to the public, claiming them to be one of the strongest materials by weight in the world, one of the beneficiary applications they trotted was the space elevator.

The notion of a space elevator had been around for some time before CNTs came along to reinvigorate it. But with the introduction of carbon-nanotube composites in around 2000, the idea started to gain more widespread acceptance. And it’s never really lost traction, with blogs sprouting up and conferences being held.

Although it dates back a few years now, IEEE Spectrum did a pretty thorough run down on the potential of actually building a space elevator.

It all seemed a bit far-fetched but there were respected scientists who believed it was possible. Nonetheless it didn’t seem as though anyone, or, better put, any company, was willing to take the bold step of setting out to build one.

That is, until now. Obayashi Corp., headquartered in Tokyo, Japan, has announced that it intends to build a space elevator by the year 2050.

With a project deadline 38 years hence, the company has certainly given itself plenty of wiggle room. But you have to wonder why would a company that is described as a major construction company make any plans of the sort?

Whatever the reason, they have made the announcement and naturally, they have turned to carbon nanotubes. While CNTs have long been heralded as the only material that could be light and strong enough to carry out the job, there have been some doubts as to whether material could actually do it.

One commenter to the IEEE Spectrum piece noted as recently as 2009: “The current limited understanding of the CNT growth process and the inter-fiber forces in a spun yarn does not allow us to build a sufficiently strong wire for the space elevator from CNTs.” Strength is not the only problem apparently. It seems they can’t grow a wire from CNT that is long enough.

Without a material as yet up to the job it raises the question again: Why make this announcement?

We do get a hint as to why in the press release as an Obayashi official says, “We'll try to make steady progress so that it won't end just up as simply a dream."

Sometimes I guess you just have to dream big.

With the “Wonders and Worries” of Nanotechnology, the Worries Seem to Be Accentuated

About a year-and-a-half ago, I came across a treasure trove of nanotechnology-related videos  posted by an organization called NISE (Nanoscale Informal Science Education) Network. And while visiting Andrew Maynard’s 2020 Science blog today, I saw a new video produced by the Science Museum of Minnesota for NISE Network. The video (see below) is designed to resemble a circa-1950s educational movie and purports to be an “aid in the discussion of the societal and ethical implication of nanotechnology.”

There is no doubt that the premise of the video is clever, but I can’t help but think that it actually muddies the discussion of nanotechnology rather than furthering it.

Recently it is has become quite popular with political groups to produce videos that make heavy use of satire to get their point across. But in these instances, the facts of the matter become obscured in the attempt to win a political argument.

In this case, the satire seems misplaced and incongruous, especially when the aim is to lay down a level foundation for discussing nanotechnology. On one hand, there does appear to have been some attempt made to strike some balance between the good and the bad that nanotechnology may represent. But on the other hand, can it really be considered even-handed when it links nanotechnology with “modern day wonders” such as nuclear power, lead paint and asbestos?

I suppose the attempt at balance in that particular gag is the mention of items—computers, Whiteout and the TV remote—that, to the filmmakers, must represent positive (or at least innocuous) uses of technology. But it might be worth noting that even those items contain all sorts of chemicals that are dangerous to human health. Where is the satirical piece lampooning the introduction of these items into the consumer market?

The video also seems to be advocating the labeling of products that contain nanoparticles rather than merely introducing it as an idea and presenting alternatives.

This video is 5 months old now. But you can’t help but wonder whether, if it was produced today, its creators would note irony in the fact that a group that had urged manufacturer labeling created a list of so-called “nano-free” sunscreens that included products containing nanoparticles. 

Of course, some things are so outlandish that they simply defy satire.

Nanocatalyst Improves Production of Plastic Precursors from Plant Material

Plastics are a petroleum product. To make plastics, oil is broken down into lower olefins--such as ethylene and propylene--at  large petrochemical plants. These lower olefins serve as precursors in the production of plastics.

There has been some research into making these lower olefins from something other than oil. One method involves burning plant material to create a synthesis gas (syngas) that reacts with a catalyst to breakdown the syngas into these lower olefins. The problem, however, has been that the yield of lower olefins from this process has been low--only 40%.

Now researchers from Utrecht University and Dow Chemical Company have developed a new, iron-based catalyst using nanoscale particles that improves the yield for this plant-based process by 50%.

The research, which was published in February 17th edition of Science, led by Krijn P. de Jong, professor of inorganic chemistry and catalysis at Utrecht University, focuses on an iron-based catalyst that allowed for much smaller grains (measured at a mere 20 nanometers) than the 500-nanometer grain size typically seen for these types of catalysts.

As with all nanocatalysts the benefit of the nanoscale is that you get more overall surface area, which makes the catalysts more reactive.

In this particular case, the Dutch researchers also serendipitously discovered that the catalyst’s effectiveness improved when some of the material became contaminated with sulfur and sodium.

This method of producing plastics from plant materials should not in any way be confused with the synthesis of plastics from corn and sugar—so-called bioplastics. Perhaps the most notable difference between these two is that bioplastics are biodegradable, whereas the lower olefin-derived plastics are not.

Of course, some environmentalists may be disturbed that we are creating another plastic that is non-biodegradable. However, they may take some comfort in knowing that at least now these olefins could potentially come from a renewable resource as opposed to the finite resources of oil.

While there is a 50% improvement in this catalyst’s ability to change the syngas into lower olefins, it still only manages to turn 60% of the syngas into the plastic precursors (as opposed to 40% with the previous catalysts), leaving 40% still as natural gas or leftover materials.

A 50% improvement in yield of just about any chemical process is significant, however, it’s not clear, according to some independent scientists interviewed in the Los Angeles Times, whether this promising experiment will make economic sense in the long run.

Spray-on Nanoparticle Mix Turns Trees Into Antennas

A small company called ChamTech Operations based in Utah has developed a nanoparticle mix that can be sprayed on any vertical object—like a tree—and make that object act as a high-powered antenna.

Not only can the sprayed-on nanoparticles make trees into antennas, but it can also extend the range of an existing antenna by a factor of 100, according to one of the principals of the company, Anthony Sutera. For instance, in RFID tags the nanoparticle spray extended the readable range of the tag from a mere five feet (1.5 meters) to 700 feet (200 m).

The material that Chamtech came up with contains nanoparticles that when sprayed on a surface act as nanocapacitors. The nanocapacitors charge and discharge very quickly and don’t create any heat that can reduce the efficiency of your typical copper antenna. The trick was to get the nanocapacitors to spread out in just the right pattern.

While watching the unassuming Sutera deliver his presentation (see below), I have to confess to being a bit incredulous.

But from the little I could find out about the technology, it seems to be what Sutera claims. A patent was issued last month. However, as far as some of the capabilities for the spray-on antenna, I haven’t been able to confirm them.

Nonetheless it’s not without precedent for nanoparticles to improve antenna range. Last year researchers at the University of Illinois used nanoparticles to create a 3-D antenna for cellphones. In that case, the 3-D antennas that the research team developed were an order of magnitude better—using such performance metrics as gain, efficiency, bandwidth, and range—than the typical monopole designs.

This product seems to take it all to another level. Perhaps most intriguing from an everyday electronics user perspective is that they sprayed the nanoparticles onto an iPhone antenna and put it into a Faraday cage. When they compared the dBm from the standard antenna to the one they sprayed, they measured an increase of 20 dBm from the standard antenna.

Another intriguing application, Sutera suggests in the video, is using the spray-on material in the white lines of the highway. This could make it possible to have high bandwidth connectivity in your car.

In the meantime, it appears that the technology was originally intended for military applications. According to the video, the military was suitably impressed.

Nanostructure of Butterfly Wings Could Lead the Way to Inexpensive Infrared Detectors

The goal of nanotechnology is often just duplicating what nature does. Whether it’s replicating the way that geckos walk on ceilings without falling down, or duplicating plants' use of photosynthesis to design improved solar cells, nature is the source of much inspiration and guidance in nanotech research.

Researchers at GE Global Research have found such inspiration from nature in their recent work in developing better thermal imaging.

The research, published in the journal Nature Photonics, was on “low-thermal-mass resonators inspired by the architectures of iridescent Morpho butterfly scales.”

The experiment involved the doping of Morpho butterfly scales with single-walled carbon nanotubes (SWNTs). When the researchers blew on butterfly wings coated with the SWNTs, the wings detected temperature changes down to a mere 0.02 degrees Celsius within 1/40 of a second.

"The iridescence of Morpho butterflies has inspired our team for yet another technological opportunity. This time we see the potential to develop the next generation of thermal imaging sensors that deliver higher sensitivity and faster response times in a more simplified, cost-effective design,” said Radislav Potyrailo, principal scientist at GE Global Research who leads GE’s bio-inspired photonics programs. “This new class of thermal imaging sensors promises significant improvement over existing detectors in their image quality, speed, sensitivity, size, power requirements, and cost.”

It should be noted that the SWNTs only enhance the heat absorption of the butterfly wings. The phenomenon occurs mainly because the wings are composed of nanoscale structures made of chitin. These structures create the reflections and refractions of light that our eyes perceive as the iridescence associated with this species of butterfly. The light effect is also caused by the expansion of the chitin when it absorbs infrared radiation.

The GE researchers were especially interested in chitin’s ability to expand by actually absorbing the infrared light, and it was this feature that they magnified by doping the wings with SWNTs.

While this is a very promising demonstration, it will likely take some time to convert these observations into any kind of device that could replace today's infrared detectors. However, the researchers are hopeful that the work they are doing with the Morpho butterfly in vapor sensing applications could reach the market as soon as five years.

Some Australians Prefer Skin Cancer to Sunscreens with Nanoparticles

In a survey conducted last month and commissioned by the Australian Department of Industry, Innovation, Science, Research and Tertiary Education, 17 percent of respondents said they would rather risk skin cancer than use sunscreens containing nanoparticles.

This survey—along with three other papers on nanoparticles in sunscreens—was  presented this week at the 2012 International Conference on Nanoscience and Nanotechnology (ICONN) in Perth, Australia.

Of the three other papers, two of them seem to indicate that the risks from using sunscreens containing nanoparticles are no greater than those of traditional sunscreens. The third paper demonstrates that some sunscreens that claim to be “nano-free” sometimes do contain nanoparticles.

Each year, 440,000 Australians receive medical treatment for skin cancers, and more than 1,700 people die from all types of skin cancer annually, according to the Cancer Council of Australia.

So, it’s clear that choosing to avoid sunscreen altogether just because it might contain nanoparticles could threaten your life. This seems an especially grave decision when two of the three reports at ICONN conference indicate that nanoparticle-based sunscreens don’t appear to be any more dangerous than the traditional variety.

Instead of stepping back and reassessing their position on this subject, the Friends of Earth (FoE) remain unconvinced by the mounting evidence that sunscreens containing nanoparticles are not dangerous to our health and have doubled down on their objections to nanoparticles in sunscreens.

The FoE have taken one of the three reports from the ICONN conference that showed that some so-called “nano-free” sunscreens actually contained nanoparticles and used that to call for a government intervention.

"What we see with this research is that in the absence of government regulation, the nanotech industry is able to more or less make up their own rules about what constitutes a nano material," said Elena McMaster, a FoE spokesperson.

That’s one interpretation, I suppose. But it could also be that traditional sunscreens might contain nanoscale particles even though no attempt had been made to manufacture or add them to the mix. Unintentional nanoparticles, if you will, not unlike those created when the tires of your car drive over the pavement.

I wonder what kind of government regulations the FoE will request. Will each container of sunscreen have to be opened and its contents examined with a scattering of synchrotron light to determine particle size?

The result of all this has been confusion for the consumer. Unfortunately, it’s the kind of confusion that could mean people risking skin cancer so as to avoid another threat the science increasingly seems to be saying isn’t one.

Super Wear-Resistant AFM Tip Pushes the Boundaries of Nanomanufacturing

In collaborative research among scientists from the University of Pennsylvania, the University of Wisconsin-Madison and IBM Research–Zürich a new ultrasharp silicon carbide tip for an atomic force microscope (AFM) has been fabricated that is thousands of times more wear-resistant at the nanoscale than previous designs.

In their manufacturing of the tip, the researchers took as their inspiration the way in which steel is strengthened through tempering. They exposed the silicon tips typically used in these devices to carbon ions and then annealed them so that a silicon carbide layer was formed while still maintaining the sharpness of the original silicon tip.

This is not the first time this team has pushed the capabilities of AFM tips. Last year the researchers developed silicon oxide-doped diamond-like carbon tips.

At the time, those tips represented the state-of-the-art, with their wear-resistance at the nanoscale being measured as 3000 times greater than silicon. The latest design is 10 000 times more wear resistant at the nanoscale.

IBM's press release quotes University of Pennsylvania professor Robert W. Carpick as saying that "compared to our previous work in silicon, the new carbide tip can slide on a silicon dioxide surface about 10 000 times farther before the same wear volume is reached and 300 times farther than our previous diamond-like carbon tip. This is a significant achievement that will make nanomanufacturing both practical and affordable."

The researchers believe that this new super-hard tip will open up new application areas for probe-based technologies like biosensors for measuring glucose levels. This is due to its ability to resist wear when being slid across the surface of silicon dioxide.

Mark Lantz, manager in storage research at IBM Research-Zurich predicted that the technology will be used in microscopic sensors that monitor "everything from water pollution to patient care."

While biosensors may be the longer range goal of the research, which was published online on 8 February in the journal Advanced Functional Materials, the researchers will initially look to put the tip to work in nanomanufacturing and nanolithography applications.

Nanotechnology Used to Create a "Desalination Battery"

Many places in the world face a shortage of drinkable water, and the situation is getting worse rather than better.

When there's not enough naturally occurring fresh water, various desalination processes become attractive technological solutions. The most recent estimate of desalination prodution that I’ve seen—dating back to 2007—was about 30 billion liters a day.

That number sounds significant, but most of the production is  limited to the oil-producing countries of the Persian Gulf that can afford the huge energy costs of running the multi-stage flash (MSF) process. It generally costs $0.5 to $0.85 per cubic meter of water, with 70% of that cost from energy consumption.

Outside of the Middle East, reverse osmosis (RO) is the most common technique. Even though it is more energy efficient, it still burns up huge amounts of energy. Striking a balance between the needs for freshwater and lower energy consumption remains a struggle. The National Research Council in its Desalination and Water Purification Technology Roadmap (PDF) has set a goal of reducing the cost of desalination by 50-80% in 2020.

Research on nanomaterials has led to several promising ideas for improving desalination. For example, one research group used nanoscale magnetic particles, originally intended for a new memory device, to enable a forward osmosis process that is more energy efficient. Another has used carbon nanotubes to filter out harmful ions from water

Now, German researchers, led by Fabio La Mantia at Center for Electrochemical Sciences at Ruhr-Universität Bochum, have developed what they call a “desalination battery.” (The work was published in the January 23, 2012 online edition Nano Letters A Desalination Battery”)

"By using electric energy, the device is able to capture the salt from a sea water stream, and release it in another sea water stream,” La Mantia explained to Nanowerk. “Our technology is, in this very early stage, very near in efficiency of reverse osmosis, one of the most efficient techniques available today."

This work builds on the work done with Yi Cui and his team at Stanford last year in developing manganese-dioxide nanorod that makes up an electrode for a battery that exploits the difference in salinity between freshwater and saltwater.

The new research runs the Stanford team's process in reverse. Instead of generating electricity from the difference in salinity, the desalination battery introduces electrical energy to extract sodium and chloride ions from seawater. The result? Desalination.

"In the first step, the fully charged electrodes, which do not contain mobile sodium or chloride ions when charged, are immersed in seawater,” explains La Mantia to Nanowerk. “A constant current is then applied in order to remove the ions from the solution. In the second step, the fresh water solution in the cell is extracted and then replaced with additional seawater. The electrodes are then recharged in this solution, releasing ions and creating brine. In the final, fourth step, the brine solution is replaced with new seawater, and the desalination battery is ready for the next cycle."

The attractive feature of the desalination battery is that it can run on low voltages, which means that a solar power source could run the battery. Perhaps it will some day be powered by nanotech-enabled  photovoltaics.

via Nanowerk

UK Reveals Plans for Becoming “Graphene Hub”

The University of Manchester in the UK has been at the forefront of graphene research ever since Andre Geim and Konstantin Novoselov fabricated the single atom-thick sheets of carbon back in 2004 and were awarded the Nobel Prize for Physics in 2010 for it.

Since then researchers across the globe have been exploring the possibilities of this wonder material, especially in the field of electronics despite it not possessing an inherent band gap. The research has not only been geographically spread out but also in terms of both commercial and government research institutions being involved in it. In short, it seems like just about any lab doing work in nanomaterials has at least one researcher working on graphene.

But the UK government was intent on not relinquishing their lead in graphene, or so it seems. So they promised £50 million ($79 million) in additional funding specifically targeted at graphene research and yesterday they announced the details of how that money is to be used.

The press release emphasizes how “The graphene hub will build on this by taking this research through to commercial success." So I was wondering if there would be any discussion of how they intended to build up an electronics industry that it never really had in the first place to exploit the material.

But the whole “commercialization” idea is left pretty vague. Instead, we get what we typically get whenever governments decide to support nanotechnology research: a building.

Nanotechnology really must be one of the biggest boons for the construction industry over the last 10 years. It certainly is putting a smile on the face of cement contractors in and around Manchester with a £45 million ($71 million) to be spent on building a new graphene institute.

The “commercial”aspect? Well, both researchers and businesses will have access to the facility.

I have heard it argued that the UK’s nanotechnology initiative might have benefited from focusing its funds and resources on a few large research institutes rather than spreading them out among a much larger number of labs. That may be true and this announcement seems to be following that line of logic.

Nonetheless, I can’t help but think that funding the construction of one large institute is an overly simplified way of maintaining your perceived leadership in graphene research and later commercialization.

While it would certainly have been more complicated to plan out how you would take all the research that already exists in the field and see how government funds could help bring the fruits of that research to market, it might have had a greater impact on the commercial aspect of keeping the UK as a leader in the field of graphene.

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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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