Dust Causes Explosions, And Apparently Nanodust Causes Mega-Explosions

By Rebecca Boyle

Dust Explosion FMGlobal via YouTube

Along with annoyingly adhering to your TV screen and tabletops, dust can be a deadly material, exploding with enormously destructive force in places like coal mines, sugar refineries and grain silos. The explosive properties of everyday dust are well known, but what about non-traditional dust? Not all dusts are created equal — and dust derived from the materials of the future could present a very different type of danger.

Led by S. Morgan Worsfold of Dalhousie University in Halifax, a team of researchers from Canada and Norway set out to determine these properties. They surveyed the small body of published research on blowing up nanoparticles, flocculent materials — fluffy synthetic stuff — and hybrid dust mixtures, which they define as any dust with an added liquid or gas.

Dust is defined as a teeny solid less than 420 microns in diameter, but that does not cover the nanoscale world. Nanodust and its potential explosive properties are relatively under-studied. A general rule of thumb in the world of dust research holds that the smaller the particle size and the greater its surface area, the more explosive it is. Nanoparticles are tiny but have a large relative surface area because of how atoms are arranged. They also tend to want to clump together, and this is one of the properties that makes items like carbon nanotubes and graphene so interesting to study. But these large agglomerations of nanoparticles, called nanopowders, are also pretty explosive, igniting with just 1 millijoule of energy. According to Worsfold and colleagues, they could ignite with a spark, a collision or mere friction. And because they’re so small, nanoparticles can remain suspended in the air for days or weeks, and you would never know it.

Then there’s flocculent dust, which is made of fibres and has a non-spherical shape and is derived from all the synthetic materials in our homes, like polyesters, acrylics and nylons. These materials don’t fall under the standard definition of dust. Still, the researchers say they are dangerous — flocculent materials are often manufactured using electrostatics, so they could ignite if something goes wrong. Hybrid mixtures could be any type of dust particle with a liquid or gas, so those are more variable.

The researchers say much more study is needed to understand the explosivity of these dusts, especially nanodust, as nanotechnology grows more prevalent. Their paper appears in the journal Industrial & Engineering Chemistry Research.

Exploding Carbon Nanotubes Could Act as Drug Grenades

Heating water inside carbon nanotubes until they explode could deliver drugs precisely, say chemists

KFC 

Carbon nanotubes offer a number of exotic options for therapies. For example, tubes filled with drugs and sealed with biodegradable caps, could work their way inside cells where they deliver their load. 

But the worry is that such a scheme may not target the drugs well enough if the caps degrade too quickly or too slowly. 

So Vitaly Chaban and Oleg  Prezhdo at the University of Rochester in New York state have a suggestion. Their idea is to fill the tubes with a mixture of drugs and water molecules and seal them with a secure cap.

Inside the body, the tubes enter various types of cell. But a treatment would involve illuminating only the cells of interest with an infrared laser which heats the tubes and boils the water they contain. The resulting increase in pressure bursts the cap and forces the water and drug molecules into the cell, like a grenade bursting.

These guys have carried out a molecular dynamics simulation to study how such a process might work. They say confinement in a nanotube substantially changes the boiling point of water and that just a small increase in temperature can boil the water and create pressures equivalent to hundreds of atmospheres.

That could be another tool in the rapidly expanding armoury of drug delivery mechanisms. But  Chaban and Prezhdo will need to answer some additional questions about the safety of this process. 

One obvious potential problem is that the explosive destruction of carbon nanotubes could damage the molecular machinery inside cells. That could cause more problems than it solves. 

The advantage, though, is that the drug is delivered only at the spot where it is required at the instant it is needed.

It's an idea that could be relatively easily tested and may turn out to be hugely useful.

Ref: arxiv.org/abs/1202.1328: Water Boiling inside Carbon Nanotubes: Towards Efficient Drug Release       

New solar cells made

SWINBURNE UNIVERSITY OF TECHNOLOGY

"Light trapping technology is of paramount importance to increase the performance of thin film solar cells and make them competitive with silicon cells." Image: R-J-Seymour/iStockphoto In a boon for the local solar industry, a team of researchers from Swinburne University of Technology and Suntech Power Holdings have developed the world's most efficient broadband nanoplasmonic solar cells. In a paper published in Nano Letters, the researchers describe how they have manufactured thin film solar cells with an absolute efficiency of 8.1 per cent. The research was conducted under the auspices of the Victoria-Suntech Advanced Solar Facility (VSASF) at Swinburne, a $12 million program jointly funded by the Victorian Government, Swinburne and Suntech. The group is working to dramatically increase the efficiency of thin film solar technology. According to Swinburne Professor Min Gu, Director of the VSASF, thin film cells have attracted enormous research interest as a cheap alternative to bulk crystalline silicon cells. However, the significantly reduced thickness of their silicon layer makes it more difficult for them to absorb sunlight. "Light trapping technology is of paramount importance to increase the performance of thin film solar cells and make them competitive with silicon cells," Professor Gu said. "One of the main potential applications of the technology will be to cover conventional glass, enabling buildings and skyscrapers to be powered entirely by sunlight." The VSASF group has been improving thin film cell efficiency by embedding gold and silver nanoparticles into the cells. This increases the wavelength range of the absorbed light, improving the conversion of photons into electrons. In their most efficient cells yet, the researchers went one step further, using what are known as nucleated or ‘bumpy' nanoparticles. Senior Research Fellow at Swinburne Dr Baohua Jia said: "The broadband plasmonic effect is an exciting discovery of the team. It is truly a collaborative outcome between Swinburne and Suntech over the last 12 months." Dr Jia believes that this new technology will have an important impact on the solar industry. "What we have found is that nanoparticles that have an uneven surface scatter light even further into a broadband wavelength range. This leads to greater absorption, and therefore improves the cell's overall efficiency. Professor Gu applauded the quick timeframe in which the research group has been able to achieve 8.1 per cent total efficiency, however he believes there is still considerable scope to improve the cells and transform the way the world sources energy. "We are on a rapid upwards trajectory with our research and development. With our current rate of progress we expect to achieve 10 per cent efficiency by mid 2012," he said. "We are well on track to reach the VSASF's target to develop solar cells that are twice as efficient and run at half the cost of those currently available." Professor Gu said that another advantage of the group's approach is that nanoparticle integration is inexpensive and easy to upscale and therefore can easily be transferred to the production line. "We have been using Suntech solar cells from the outset, so it should be very straightforward to integrate the technology into mass manufacturing. We expect these cells to be commercially available by 2017." Suntech CEO Dr Zhengrong Shi said: "Our team has achieved an impressive milestone with the world record for the most efficient broadband nanoplasmonic thin-film cell. This is an important step in demonstrating the potential of nanotechnology in leading the next generation of solar cells." The Nano Letters paper was authored by Dr Xi Chen, Dr Baohua Jia, Dr Jhantu Saha, Mr Boyuan Cai, Dr Nicholas Stokes, and Professor Min Gu from Swinburne and Dr Qi Qiao, Dr Yongqian Wang and Dr Zhengrong Shi from Suntech. Editor's Note: Original news release can be found here.

New way to create stem cells

THE UNIVERSITY OF QUEENSLAND

Image: Pgiam/iStockphoto University of Queensland scientists have developed a world-first method for producing adult stem cells that will substantially impact patients who have a range of serious diseases. The research is a collaborative effort involving UQ's Australian Institute for Bioengineering and Nanotechnology (AIBN) and is led by UQ Clinical Research Centre's (UQCCR) Professor Nicholas Fisk. It revealed a new method to create mesenchymal stem cells (MSCs), which can be used to repair bone and potentially other organs. “We used a small molecule to induce embryonic stem cells over a 10 day period, which is much faster than other studies reported in the literature,” Professor Fisk said. “The technique also worked on their less contentious counterparts, induced pluripotent stem cells. “To make the pluripotent mature stem cells useful in the clinic, they have to be told what type of cell they need to become (pre-differentiated), before being administered to an injured organ, or otherwise they could form tumours. “Because only small numbers of MSCs exist in the bone marrow and harvesting bone marrow from a healthy donor is an invasive procedure, the ability to make our own MSCs in large number in the laboratory is an exciting step in the future widespread clinical use of MSCs. “We were able to show these new forms of stem cells exhibited all the characteristics of bone marrow stem cells and we are currently examining their bone repair capability." AIBN Associate Professor and Co-Investigator on the project, Ernst Wolvetang said the new protocol had overcome a significant barrier in the translation of stem cell-based therapy. “We are very excited by this research, which has brought together stem cell researchers from two of the major UQ research hubs UQCCR and AIBN,” Associate Professor Wolvetang said. The research is published in the February edition of the STEM CELLS Translational Medicine journal. Editor's Note: Original news release can be found here.

New power source found

RMIT UNIVERSITY

The researchers learned that a nanotube is an excellent conductor of heat from burning fuel. Image: 3dts/iStockphoto Researchers at the Massachusetts Institute of Technology (MIT) and RMIT University have made a breakthrough in energy storage and power generation. The power generated relative to the energy source size is three to four times greater than what is currently possible with the best lithium-ion batteries. While on sabbatical from RMIT in 2009 and 2010, Associate Professor Dr Kourosh Kalantar-zadeh, from the School of Electrical and Computer Engineering, joined MIT Associate Professor Michael Strano's nanotechnology research group. The team was working on measuring the acceleration of a chemical reaction along a nanotube when they discovered that the reaction generated power. Now the two researchers are using their combined expertise in chemistry and nanomaterials to explore this phenomenon. Their work titled Nanodynamite: Fuel-coated nanotubes could provide bursts of power to the smallest systems is in the December IEEE Spectrum Magazine, the publication of the IEEE, the world's largest professional technology association. Associate Professor Kalantar-zadeh said that his experimental system, based on one of the materials that have come from nanotechnology — carbon nanotubes — generates power, something researchers had not seen before. “By coating a nanotube in nitrocellulose fuel and igniting one end, we set off a combustion wave along it and learned that a nanotube is an excellent conductor of heat from burning fuel. Even better, the combustion wave creates a strong electric current,” he said. “Our discovery that a thermopower wave works best across these tubes because of their dual conductivity turns conventional thermoelectricity on its head. “It's the first viable nanoscale approach to power generation that exploits the thermoelectric effect by overcoming the feasibility issues associated with minimising dimensions. “But there are multiple angles to explore when it comes to taming these exotic waves and, ultimately, finding out if they're the wave of the future.” Editor's Note: Original news release can be found here.

Engineers Weld Nanowires With Light

A titled, cross-sectional scanning electron microscope image of plasmonically welded nanowires of silver. (Credit: Mark Brongersma, Stanford)

Science Daily  — At the nano level, researchers at Stanford have discovered a new way to weld together meshes of tiny wires. Their work could lead to innovative electronics and solar applications. To succeed, they called upon plasmonics.

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One area of intensive research at the nanoscale is the creation of electrically conductive meshes made of metal nanowires. Promising exceptional electrical throughput, low cost and easy processing, engineers foresee a day when such meshes are common in new generations of touch-screens, video displays, light-emitting diodes and thin-film solar cells.

Standing in the way, however, is a major engineering hurdle: In processing, these delicate meshes must be heated or pressed to unite the crisscross pattern of nanowires that form the mesh, damaging them in the process.

In a paper just published in the journal Nature Materials, a team of engineers at Stanford has demonstrated a promising new nanowire welding technique that harnesses plasmonics to fuse the wires with a simple blast of light.

Self-limiting

At the heart of the technique is the physics of plasmonics, the interaction of light and metal in which the light flows across the surface of the metal in waves, like water on the beach.

"When two nanowires lay crisscrossed, we know that light will generate plasmon waves at the place where the two nanowires meet, creating a hot spot. The beauty is that the hot spots exist only when the nanowires touch, not after they have fused. The welding stops itself. It's self-limiting," explained Mark Brongersma, an associate professor of materials science engineering at Stanford and an expert in plasmonics. Brongersma is one of the study's senior authors.

"The rest of the wires and, just as importantly, the underlying material are unaffected," noted Michael McGehee, a materials engineer and also senior author of the paper. "This ability to heat with precision greatly increases the control, speed and energy efficiency of nanoscale welding."

In before-and-after electron-microscope images, individual nanowires are visually distinct prior to illumination. They lay atop one another, like fallen trees in the forest. When illuminated, the top nanowire acts like an antenna of sorts, directing the plasmon waves of light into the bottom wire and creating heat that welds the wires together. Post-illumination images show X-like nanowires lying flat against the substrate with fused joints.

Transparency

In addition to making it easier to produce stronger and better performing nanowire meshes, the researchers say that the new technique could open the possibility of mesh electrodes bound to flexible or transparent plastics and polymers.

To demonstrate the possibilities, they applied their mesh on Saran wrap. They sprayed a solution containing silver nanowires in suspension on the plastic and dried it. After illumination, what was left was an ultrathin layer of welded nanowires.

"Then we balled it up like a piece of paper. When we unfurled the wrap, it maintained its electrical properties," said co-author Yi Cui, an associate professor materials science and engineering. "And when you hold it up, it's virtually transparent."

This could lead to inexpensive window coatings that generate solar power while reducing glare for those inside, the researchers said.

"In previous welding techniques that used a hotplate, this would never have been possible," said lead author, Erik C. Garnett, PhD, a post-doctoral scholar in materials science who works with Brongersma, McGehee and Cui. "The Saran wrap would have melted far sooner than the silver, destroying the device instantly."

"There are many possible applications that would not even be possible in older annealing techniques," said Brongersma. "This opens some interesting, simple and large-area processing schemes for electronic devices -- solar, LEDs and touch-screen displays, especially."

This research was supported by the Center for Advanced Molecular Photovoltaics (CAMP) at Stanford University funded by King Abdullah University of Science and Technology (KAUST).

Nanotube Paint Can Spot Structural Defects and Alert Authorities Before Damage Occurs

By Rebecca Boyle 

Nano Paint Mohamed Saafi of the University of Strathclyde examines a piece of material coated with a new nano paint, which can detect structural damage when electrodes are attached. University of Strathclyde

A new paint made of power plant waste and carbon nanotubes can automatically detect structural faults, alerting authorities before damage occurs. It could be a cheaper, easier way to monitor facilities like bridges, mines and even wind turbines.
It’s made from aligned carbon nanotubes, which can carry an electric current, and fly ash, which is a byproduct of coal burning. The paint can be sprayed onto any surface, and electrodes are attached to it, according to developers at the University of Strathclyde in Glasgow. If the nanotubes bend, their conductivity will change, which will be detected by the electrodes. Small wireless transmitters placed throughout the structure would receive data from the electrodes. If they detect a change in conductivity, this would be considered a sign of a defect in the structure. Then the system could conceivably alert the company or government body responsible for maintaining said structure.

Technology, Rebecca Boyle, bridges, carbon nanotubes, coal, coal plants, structural analysis, structural engineering, tunnels, wind turbines

This would be much cheaper and simpler than current monitoring methods, Strathclyde scientists said — currently, wind turbine foundations are inspected visually, and bridges and tunnels only have monitoring networks in certain areas, not throughout the whole structure. Early defect detection could be cheaper to repair, not to mention safer. A network of electrode-embedded nanotubes doesn’t sound inexpensive, but the researchers say it would be cheap — one percent the cost of alternative inspection methods — in part because of the fly ash component. Fly ash is a byproduct of coal combustion and it’s generally stored at power plants and landfills or it’s recycled. The nanotube paint could be one new use for it. It also lends the paint some added durability, which means it could last in a wide range of environmental conditions.
For now, the electrode transmitters would be powered by batteries, but other designs could incorporate solar panels, piezoelectrics or other energy-harvesting technology, the researchers say. Strathclyde Ph.D candidate David McGahon and civil engineering professor Mohamed Saafi have built a prototype and it was shown to be effective, according to a Strathclyde news release. They plan to carry out larger-scale tests in Glasgow in the future.
[via Science Daily]

Smallest-Ever Nanotube Transistors Outperform Silicon

COMPUTING

A nine-nanometer device shows that nanotubes could be a viable alternative to silicon as electronics get even tinier.

• BY KATHERINE BOURZAC

The smallest carbon-nanotube transistor ever made, a nine-nanometer device, performs better than any other transistor has at this size.

For over a decade, researchers have promised that carbon nanotubes, with their superior electrical properties, would make for better transistors at ever-tinier sizes, but that claim hadn't been tested in the lab at these extremes. Researchers at IBM who made the nanotube transistors say this is the first experimental evidence that any material is a viable potential replacement for silicon at a size smaller than 10 nanometers.

"The results really highlight the value of nanotubes in the most sophisticated type of transistors," says John Rogers, professor of materials science at the University of Illinois at Urbana-Champaign. "They suggest, very clearly, that nanotubes have the potential for doing something truly competitive with, or complementary to, silicon."

The shrinkage of silicon transistors over the past several decades has reduced the cost of electronics and led to more processing power with less energy consumption. But the downsizing of silicon electronics might hit a roadblock at around 10 nanometers, says Aaron Franklin, a researcher at the IBM Watson Research Center in Yorktown Heights, New York. "We are now reaching physical limits," he says. As transistors are made smaller, it gets more difficult to control how electrons move through the silicon channel to turn the transistor on and off. Faced with this unruly, power-draining behavior, Intel announced last year that it would switch to a new, three-dimensional transistor design for its 22-nanometer generation of chips. Other companies are working on so-called ultrathin body transistors. No matter how it's shaped, though, silicon is silicon, and dealing with it at extremely small sizes presents problems even in these new transistor designs.

Many materials have been hyped as a potential replacement for silicon, including carbon nanotubes. That material and others have shown promise in larger transistors, but until now, no one had demonstrated a carbon-nanotube transistor smaller than 10 nanometers. "If nanotubes can't go much further than silicon, then working on them is a waste of time," says Franklin. "We've made nanotube transistors at aggressively scaled dimensions, and shown they are tremendously better than the best silicon devices."

To test how the size of a nanotube transistor affected its performance, Franklin's group made multiple transistors of different sizes along a single nanotube. This enabled them to control for any variations that might occur from nanotube to nanotube. First, they had to lay down a very thin layer of insulating material for the nanotube to sit on. And they developed a two-step process for adding electrical gates to the nanotube without damaging it. These techniques are by no means ready for manufacturing, but they enabled the IBM group to make the first nanotube devices smaller than 10 nanometers to test in the lab. The work is described online in the journal Nano Letters.

The IBM group demonstrated that its nine-nanometer nanotube transistor had much lower power consumption than other transistors the same size. And it can carry more current than comparable silicon devices, which means a better signal.

Several major engineering problems remain, says Franklin. First, researchers have to come up with better methods for making pure batches of semiconducting nanotubes—metallic tubes in the mix will short out integrated circuits. Second, they must come up with a way to place large numbers of nanotubes on a surface with perfect alignment.

Electron Holography Produces First Image of a Single Protein

A non-destructive method for imaging single proteins could help solve one of the biggest challenges in biology

KFC 

The behaviour and function of proteins is largely determined by their shape.  So one of the great ongoing quests in biology is to understand and model the structure of proteins. 

That's a tricky task. Biologists currently do it using techniques such as X-ray crystallography, which requires millions of protein chains to form into a crystal.  The trouble is that most proteins don't form crystals. And even when they do, not all the molecules will be in the same conformation and so the diffraction pattern can end up being a kind of average of several different shapes.

That's why biologists know the shape of less than 2 per cent of the proteins in humans.

What's needed, of course, is a way of imaging individual proteins. One idea is to us x-rays or electron beams to do the trick and indeed some groups have had some success with this technique. But the disadvantage is that beams with an energy of a few KeV tend to destroy biomolecules so it's not clear how accurate these images can be. Nether is it possible to view the molecules over time.

Today, Jean Nicholas Longchamp and pals at the University of Zurich in Switzerland have found a way round this. These guys make the entirely sensible suggestion of imaging proteins using low energy electron beams that don't destroy biomolecules. 

At this energy, electron beams have a wavelength of a nanometre or so, making them perfect not just for imaging with atomic resolution, but for holography. 

And that's exactly what these guys have done. They've created an electron hologram of a protein molecule called ferritin--that's the football-shaped protein that stores and releases iron and is found in almost all living things.

The technique is fairly straightforward. They mix ferritin and carbon nanotubes in water which they then allow to evaporate. This leaves carbon nanotubes with single ferritin proteins bonded to them.

The evaporation takes place in a sieve-like container and leaves some of the ferritin-carrying nanotubes suspended across the holes in the sieve. That allows Longchamp and co to send the low energy electron beam from one side of the hole and then record the interference pattern on the other. 

The result is the first atomic resolution electron hologram of ferritin ever made in a non-destructive way. "We have reported the very first non-destructive investigation of an individual protein by means of  low-energy electron holography," they say.

They've even compared their images to ones of ferritin imaged with high energy electrons and are able to show the damage that the high energy bombardment causes.

That's exciting news. The problem of accurately determining the structure, and therefore the function, of proteins is a major headache for biologists and one that low energy electron holography could help to solve quickly. "The sample preparation method can be applied to a broad class of molecules," say Longchamp and friends.

They now want to improve the resolution of their technique and have a number of tricks up their sleeves that they are no doubt investigating.

Given that the techniques is relatively straightforward and inexpensive, expect to see an explosion of interest in single molecule structural biology at atomic resolution.

Ref: arxiv.org/abs/1201.4300: Non-Destructive Imaging Of An Individual Protein

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