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Sudipta Seal, materials scientist and engineer at the University of Central Florida, holds a bottle containing billions of ultra-small, engineered nanoceria.Credit: Sudipta Seal, University of Central Florida

Sudipta Seal is enthralled by nanoparticles, particularly those of a rare earth metal called cerium. The particles are showing potential for a wide range of applications, from medicine to energy. Seal is a professor of materials science and engineering at the University of Central Florida (UCF), and several years ago, he and his colleagues engineered nanoparticles of cerium oxide (CeO2), a material long used in ceramics, catalysts, and fuel cells. The novel nanocrystalline form is non-toxic and biocompatible--ideal for medical applications.Since then, the researchers found that cerium oxide nanoparticles have two additional medical benefits: they behave like an antioxidant, protecting cells from oxidative stress, and they can be fine-tuned to potentially deliver medical treatments directly into cells.
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The alternating pattern of PE-b-PEO formed on SWNTs with a 12 nm period imaged using transmission electron microscopy. The dark and bright stripes represent the PEO and PE domains, respectively.Image Source: Drexel University

Professor Christopher Li in Drexel University’s Department of Materials Science and Engineering and colleagues are one step closer to making personal electronic devices even smaller.  Their research demonstrates that it is possible to manipulate a carbon nanotube, the building block of nanotechnology applications, for the future miniaturization of electronic devices, including computers, cell phones, and PDAs. Carbon nanotubes, or CNTs -- the diameter of only a few millionths of a human hair -- are favored in nanotechnology research and applications for their unusual properties.  To be able to use CNTs to create ever smaller electronic devices, a nanotube would have to be furnished with multiple transistors. To achieve this goal, one has to be able to fabricate uniform, large-scale, controllable patterns on CNTs at a few tenths of a nanometer scale, a difficult task which to date has not been successfully addressed.  Drexel researchers, led by Professor Li, have now demonstrated that it is possible to create periodic, alternating patterns on carbon nanotubes with a period of 12 nanometers by decorating carbon nanotubes with judiciously selected crystalline block copolymers (in this case polyethylene-block-poly(ethylene oxide)).  Block copolymers are comprised of two chemically different polymer chains that are covalently linked together at one end. The trick is to select two blocks of the copolymer so that one has a strong tendency to crystallize on the carbon nanotube surface and the other block can then be brought to the vicinity of the carbon nanotube. The period of the pattern can be easily controlled to be ~10-100 nanometers by simply varying the molecular weight of the block copolymers.
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Bright red-orange photoluminescence observed from porous silicon nanoparticles with human HeLa cells, magnified 1000x and viewed in the reflection from a silicon wafer. Prepared from high-purity silicon wafers, these nanoparticles provide a non-toxic and biodegradable alternative to conventional quantum dots for in-vitro and in-vivo fluorescence imaging. The cell nuclei are stained blue.Credit: Luo Gu, Ji-Ho Park, UCSD

The first biodegradable fluorescent nanoparticle to safely image tumors and organs in live mice could be used for cancer detection and treatment in humans. Chemistry professor Michael Sailor and a team including National Science Foundation supported researchers at the University of California, San Diego, report developing the first nanoscale "quantum dot" particle that glows brightly enough to allow physicians to examine internal organs and lasts long enough to release cancer drugs before breaking down into harmless by-products. The research is another step towards mainstreaming the use of nanotechnology in medicine. Many researchers say using nanomaterials for medical reasons is the health field's next major frontier. The payoff, they say, could be lower drug toxicity, lower treatment costs, more efficient drug use, and better patient diagnosis. "There are a lot of nanomaterials that have an ability to do fluorescence imaging," says Sailor, referring to a useful property that potentially could help doctors further see organs, diagnose patients and perform surgeries. "But they're generally toxic and not appropriate for putting into people." The problem results from toxic organic or inorganic chemicals used to make the materials glow. For example, fluorescent semiconductor nanoparticles known as quantum dots can release potentially harmful heavy metals when they break down. A paramount issue in determining the efficacy of nanomaterials is the body's ability to harmlessly get rid of residual leftovers after the nanomaterial helps diagnose or treat a disease. So Sailor's team designed a new, non-toxic quantum dot nanoparticle made from silicon wafers, the same high-purity wafers that go into the manufacture of computer chips. Reseachers took the thin wafers and ran electric current through them drilling billions of pores. They then used ultrasound waves to break the wafer into bits as small as 100 nanometers. The resulting spongy silicon particles contained nano-scale features capable of displaying quantum confinement effects, or the so-called "quantum dots." The ones in the UCSD experiment glowed a reddish color when exposed to red, blue, or ultraviolet light.
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Credit: Cornell University

Researchers at Cornell University recently made a major breakthrough when they invented a method to test and demonstrate a long-held hypothesis that some very, very small metal particles work much better than others in various chemical processes such as converting chemical energy to electricity in fuel cells or reducing automobile pollution. Nanoscale metal particles naturally have a wide variety of shapes and sizes and chemists long suspected that some particles work much better than others when it comes to catalyzing chemical processes. Researchers at Cornell University recently confirmed the hypothesis and discovered that some nanoparticles randomly change from good particles to bad particles. The breakthrough, reported in this week's edition of the journal Nature Materials, also came with a surprise. By devising a way to watch individual molecules react with a single nanoscale particle of gold in real time, researchers confirmed that some gold particles are better at increasing the rate of a chemical reaction than others, but they also found that a good catalyst sometimes spontaneously turns bad. Understanding why these particles change and how to stabilize the "good" particles may lead to solutions for a wide range of problems such as the current global energy challenge.
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James Tour and coworkers at Rice University synthesized a molecular car with four carbon-based wheels that roll on axles made from linked carbon atoms. The nano-car's molecular wheels are 5,000 times smaller than a human cell. A powerful technique that allows viewing objects at the atomic level called scanning tunneling microscopy reveals the wheels roll perpendicular to the axles, rather than sliding about like a car on ice as the car moves back and forth on a surface.Credit: Y. Shirai/Rice University

A recent paper published in Scientific American, asks readers to imagine producing vehicles so small they would be about the size of a molecule and powered by engines that run on sugar. To top it off, a penny would buy a million of them. The concept is nearly unthinkable, but it's exactly the kind of thing occupying National Science Foundation supported researchers at Penn State and Rice universities. For several years, Ayusman Sen, who heads Penn State's department of chemistry, and his colleague Thomas E. Mallouk, director of the Center for Nanoscale Science at Penn State, have investigated technologies that could realize these remarkable machines whose uses might include delivering medicine to specific tissue, accomplishing surgeries or communicating with the outside world from inside the human body. Though researchers consistently have improved ways to build nano-machines, the stumbling block has been finding a way to power them. Shrinking energy producers--internal combustion engines, electric motors or jet engines--below millimeter dimensions is not an easy task, but researchers may be closer to a fantastic solution. In the 1966 movie Fantastic Voyage, scientists shrink a submarine to microscopic size and inject it into the blood stream of a brilliant scientist, who has a blood clot forming in his brain. The nano-sized surgeons then set out to remove the blood clot. Today, researchers can steer nano-machines, use them to convey cargo, and guide them using electromagnetic forces or chemical interactions. All of this, they say, makes the world seen in Fantastic Voyage not so far-fetched.
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Researchers at Rensselaer have discovered a new technique for provoking unusual crazing behavior in epoxy composites. The crazing, which causes the composite to deform into a network of nanoscale pillar-like fibers that bridge together both sides of a crack and slow its growth, could lead to tougher, more durable components for aircraft and automobiles.Image Source: Rensselaer Polytechnic Institute

A new research discovery at Rensselaer Polytechnic Institute could lead to tougher, more durable composite frames for aircraft, watercraft, and automobiles. Epoxy composites are increasingly being incorporated into the design of new jets, planes, and other vehicles. Composite material frames are extremely lightweight, which lowers the overall weight of the vehicle and boosts fuel efficiency. The downside is that epoxy composites can be brittle, which is detrimental to its structural integrity. Professor Nikhil Koratkar, of Rensselaer’s Department of Mechanical, Aerospace, and Nuclear Engineering, has demonstrated that incorporating chemically treated carbon nanotubes into an epoxy composite can significantly improve the overall toughness, fatigue resistance, and durability of a composite frame. When subjected to repetitive stress, a composite frame infused with treated nanotubes exhibited a five-fold reduction in crack growth rate as compared to a frame infused with untreated nanotubes, and a 20-fold reduction when compared to a composite frame made without nanotubes.
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An atom-level view of the nanoscale interface between amorphous carbon and diamond. At such a small scale, the surfaces are rough, although researchers have been treating them as smooth.Image source: University of Wisconsin-Madison

To understand friction on a very small scale, a team of University of Wisconsin-Madison engineers had to think big. Friction is a force that affects any application where moving parts come into contact; the more surface contact there is, the stronger the force. At the nanoscale—mere billionths of a meter—friction can wreak havoc on tiny devices made from only a small number of atoms or molecules. With their high surface-to-volume ratio, nanomaterials are especially susceptible to the forces of friction. Yet, researchers have trouble describing friction at such small scales because existing theories are not consistent with how nanomaterials actually behave. Through computer simulations, the group demonstrated that friction at the atomic level behaves similarly to friction generated between large objects. Five hundred years after Leonardo da Vinci discovered the basic friction laws for large objects, the UW-Madison team has shown that similar laws apply at the nanoscale. Current nanoscale friction theories are based on the idea that nanoscale surfaces are smooth—yet in reality, the surfaces resemble a mountain range, where each peak corresponds to an atom or a molecule. The researchers discovered simple laws of nanoscale friction. They found that friction is proportional to the number of atoms that interact between two nanoscale surfaces. The researchers’ simulations showed that, at the nanoscale, materials in contact behave more like large rough objects rubbing against each other, rather than as two perfectly smooth surfaces, as was previously imagined.
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