Science Quick Picks » Nanotechnology

Another Stunning Graphene Experimental Surprise

Jorge Goncalves — Thu, 29 Jul 2010 18:53:53 +0000

Graphene, the extraordinary form of carbon that consists of a single layer of carbon atoms, has produced another in a long list of experimental surprises. In the current issue of the journal Science, a multi-institutional team of researchers headed by Michael Crommie, a faculty senior scientist in the Materials Sciences Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley, reports the creation of pseudo-magnetic fields far stronger than the strongest magnetic fields ever sustained in a laboratory – just by putting the right kind of strain onto a patch of graphene.

“We have shown experimentally that when graphene is stretched to form nanobubbles on a platinum substrate, electrons behave as if they were subject to magnetic fields in excess of 300 tesla, even though no magnetic field has actually been applied,” says Crommie. “This is a completely new physical effect that has no counterpart in any other condensed matter system.”

Crommie notes that “for over 100 years people have been sticking materials into magnetic fields to see how the electrons behave, but it’s impossible to sustain tremendously strong magnetic fields in a laboratory setting.” The current record is 85 tesla for a field that lasts only thousandths of a second. When stronger fields are created, the magnets blow themselves apart. The ability to make electrons behave as if they were in magnetic fields of 300 tesla or more – just by stretching graphene – offers a new window on a source of important applications and fundamental scientific discoveries going back over a century. This is made possible by graphene’s electronic behavior, which is unlike any other material’s.

A carbon atom has four valence electrons; in graphene (and in graphite, a stack of graphene layers), three electrons bond in a plane with their neighbors to form a strong hexagonal pattern, like chicken-wire. The fourth electron sticks up out of the plane and is free to hop from one atom to the next. The latter pi-bond electrons act as if they have no mass at all, like photons. They can move at almost one percent of the speed of light. The idea that a deformation of graphene might lead to the appearance of a pseudo-magnetic field first arose even before graphene sheets had been isolated, in the context of carbon nanotubes (which are simply rolled-up graphene). In early 2010, theorist Francisco Guinea of the Institute of Materials Science of Madrid and his colleagues developed these ideas and predicted that if graphene could be stretched along its three main crystallographic directions, it would effectively act as though it were placed in a uniform magnetic field. This is because strain changes the bond lengths between atoms and affects the way electrons move between them. The pseudo-magnetic field would reveal itself through its effects on electron orbits.

In classical physics, electrons in a magnetic field travel in circles called cyclotron orbits. These were named following Ernest Lawrence’s invention of the cyclotron, because cyclotrons continuously accelerate charged particles (protons, in Lawrence’s case) in a curving path induced by a strong field. Viewed quantum mechanically, however, cyclotron orbits become quantized and exhibit discrete energy levels. Called Landau levels, these correspond to energies where constructive interference occurs in an orbiting electron’s quantum wave function. The number of electrons occupying each Landau level depends on the strength of the field – the stronger the field, the more energy spacing between Landau levels, and the denser the electron states become at each level – which is a key feature of the predicted pseudo-magnetic fields in graphene.

Describing their experimental discovery, Crommie says, “We had the benefit of a remarkable stroke of serendipity.”

Continue reading the press release Graphene Under Strain Creates Gigantic Pseudo-Magnetic Fields at Lawrence Berkeley National Laboratory’s News Center.

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Another Stunning Graphene Experimental Surprise

OECD on Risks and Benefits of Nanomaterials

Jorge Goncalves — Fri, 16 Jul 2010 15:16:14 +0000

Innovation can bring benefits, but possible risks too. The emergence of nanotechnology, which manipulates barely visible materials for industrial purposes, is a case in point, and policymakers are taking a close look.

All kinds of nanomaterials are now found in common household items, from sports gear and sunscreens to socks and dresses, from beds and shampoos for pets to mobile phones and computer processors. Like any innovative technology, nanotechnology has the potential for producing unimagined benefits–and unintended risks. The OECD has been at the forefront of international efforts to minimise those risks since 2005. These days, co-operation is intensifying as nanomaterials become part of our everyday landscape.

Continue reading the OECD Observer article Nanomaterials: Getting the measure.

See all the information about OECD Safety of Manufactured Nanomaterials. Research and development in nanotechnologies is directed toward understanding and creating improved materials, devices, and systems that exploit these new properties. Such properties have been found to be very useful for an increasing number of commercial applications, for example: protective coatings; light-weight materials; self-cleaning clothing, to name but a few.

But different properties mean that nanomaterials are differed from conventional molecules with respect to human health and environmental safety. The traditional testing and assessment methods used to determine the safety of traditional chemicals are not necessarily (fully) applicable to nanomaterials. There should be a responsible and co-ordinated approach to ensure that potential safety issues are being addressed at the same time as the technology is developing.

OECD Database on Research into the Safety of Manufactured Nanomaterials. This database is a global resource which collects research projects that address environmental, human health and safety issues of manufactured nanomaterials. This database helps identify research gaps and assists researchers in future collaborative efforts. The database also assists the projects of the OECD’s Working Party on Manufactured Nanomaterials (WPMN) as a resource of research information.

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

OECD on Risks and Benefits of Nanomaterials

New Fluorescent Silicon Nanoparticles

Jorge Goncalves — Tue, 30 Jun 2009 18:39:53 +0000

University of Leicester researchers discover new fluorescent silicon nanoparticles. Researchers in the Department of Physics and Astronomy at the University of Leicester have developed a new synthesis method, which has led them to the discovery of fluorescent silicon nanoparticles and may ultimately help track the uptake of drugs by the body’s cells.

Dr Klaus von Haeften explained: “A key advantage of the new method is the independent control of the nanoparticles’ size and their surface properties. The method is extremely versatile and produces the fluorescent suspensions in one go. The findings may revolutionise the performance of electronic chips while satisfying the increasing demand for higher integration densities.”

The nanoparticles contain just a few hundred silicon atoms and their fluorescence were discovered after mixing them with water. This resulted in stability in fluorescence intensity over more than a three month period.

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

New Fluorescent Silicon Nanoparticles

Next Generation Nanofilms

Jorge Goncalves — Wed, 15 Apr 2009 17:54:31 +0000

Next generation nanofilms created – new research described in AIP’s the Journal of Chemical Physics. ‘With the human genome in hand, biochemists have cataloged the 3-D structures of thousands of proteins isolated from living cells. But one important class of proteins — those stuck in the cell membranes — has proven difficult to extract and study in 3-D crystals. Now an international team of scientists has developed a way to train such molecules to line up neatly on the surface of water in thin, tissue-like layers called nanofilms. This technique should allow biochemists to better see and study the molecules and may lead to a new generation of molecular electronics and ultra-thin materials only one molecule thick.

“To the best of our knowledge, this is the first time aligned films less than a nanometer thick have been produced,” say Iftach Nevo, a Marie Curie fellow at the University of Aarhus in Denmark, and Leslie Leiserowitz of the Weizmann Institute of Science in Israel. Together with their colleagues at these institutions and at the Max-Planck Institute of Colloids and Interfaces in Germany and Northwestern University in Evanston, they describe their research in the 14 April 2009 issue of The Journal of Chemical Physics, published by the American Institute of Physics.

One way of creating a nanofilm is to build it on the surface of water. First, the building blocks of the film are dissolved in a volatile substance. When a drop of this solution is splashed onto water, the solvent evaporates. The building blocks left floating on the water interact with each other and spontaneously come together – like soap scum in a bathtub – to create a thin crystalline layer.

The shortcoming of this technique is that the thin crystals in the film created will be a mess. Like a mob in a dance club, molecules floating on a surface tend to spin around chaotically with little regard for order. Different patches of molecules will point different, random directions. Because the orientation of these molecules dictates the electrical, magnetic, and optical properties of the final film, these jumbled regions are difficult to develop into useful technologies. They are also difficult to analyze using imaging techniques like X-ray diffraction.

To force the molecules to line up, the team blasted them with nanosecond laser pulses. These pulses create an electric field that interacts with the molecules, rotating them slowly. The electric field associated with these laser pulses is polarized, filtered so that all of the light waves vibrate in the same direction. Molecules caught in the laser feel most stable when they line up along this direction, a process analogous to the needle in a compass swinging to line up with the Earth’s magnetic field. Eventually, this forms an aligned film with long range order.

The technique has not been completely perfected yet. Its success rate is about 30 percent, but the group believes that a better understanding of what is happening during the evaporation process and how the molecules interact with each other just before solidifying into a film will improve the efficiency.’

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Next Generation Nanofilms

On the Road to an Antitumor Vaccine

Jorge Goncalves — Sun, 20 Jan 2008 20:54:17 +0000

Polymeric Nanoparticles for Tumor Vaccines. ‘The quest for an effective antitumor vaccine has received a boost from the results of work aimed at developing a nanoparticle that delivers tumor antigens to the immune system cells that trigger antibody production. The results of this effort, led by Shinsaku Nakagawa, Ph.D., and Naoki Okada, Ph.D., of Osaka University in Japan, were published in the journal Biochemical and Biophysical Research Communications.

Vaccines are complex preparations of proteins and other materials designed to produce maximal immune response to those proteins. One factor that determines a vaccine’s potency is the ability of this mixture to trigger a recognition event between the protein antigen and immune system cells known as antigen-presenting cells (APCs). Using the biocompatible polymer poly(y-glutamic acid), the investigators were able to create self-assembling nanoparticles that entrap proteins as they form. The resulting nanoparticles were relatively stable, releasing their protein content over the course of a month. The investigators also demonstrated that they could freeze-dry these nanoparticles and reconstitute them without altering the functionality of the entrapped protein, a desirable property for any vaccine vehicle designed for use outside of major medical centers.’

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

On the Road to an Antitumor Vaccine

Identifying Tumors with Gold Nanoparticles and ScFv Peptides

Jorge Goncalves — Sun, 23 Dec 2007 20:56:54 +0000

Gold nanoparticle probes may allow earlier cancer detection. ‘Using tiny gold particles embedded with dyes, researchers have shown that they can identify tumors under the skin of a living animal. These tools may allow doctors to detect and diagnose cancer earlier and less invasively

Studded with antibody fragments called ScFv peptides that bind cancer cells, the gold particles grab onto tumors after their injection into a mouse. When illuminated with a laser beam, the tumor-bound particles send back a signal that is specific to the dye, scientists at Emory University and the Georgia Institute of Technology report.

The results appear online Dec. 23 in the journal Nature Biotechnology and are scheduled for publication in the Jan. 1, 2008 print edition.

“This is a new class of nanotechnology agents for tumor targeting and imaging,” says senior author Shuming Nie, PhD, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

Dr. Nie and his collaborators at the Emory/Georgia Tech Cancer Nanotechnology Center of Excellence have been developing light-emitting semiconductor crystals called “quantum dots” into tools for cancer detection and treatment for several years. However, colloidal gold, or gold particles in suspension, offers advantages compared with quantum dots in that the gold appears to be non-toxic and the particles produce a brighter, sharper signal, Dr. Nie says.

“The detail is like a fingerprint, and because of the enhancement provided by the gold surface, the signal from the dye tags is very bright,” he says, adding that the distinct peaks in the dye signal mean several different probes could be used at the same time.’

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Identifying Tumors with Gold Nanoparticles and ScFv Peptides

Plastic Steel: Light and Transparent but Strong as Steel

Jorge Goncalves — Sun, 14 Oct 2007 18:10:09 +0000

U-M research: New plastic is strong as steel, transparent. ‘By mimicking a brick-and-mortar molecular structure found in seashells, University of Michigan researchers created a composite plastic that’s as strong as steel but lighter and transparent. It’s made of layers of clay nanosheets and a water-soluble polymer that shares chemistry with white glue.

Engineering professor Nicholas Kotov almost dubbed it “plastic steel,” but the new material isn’t quite stretchy enough to earn that name. Nevertheless, he says its further development could lead to lighter, stronger armor for soldiers or police and their vehicles. It could also be used in microelectromechanical devices, microfluidics, biomedical sensors and valves and unmanned aircraft.

Kotov and other U-M faculty members are authors of a paper on this composite material, “Ultrastrong and Stiff Layered Polymer Nanocomposites”, published in the Oct. 5 edition of Science.

The scientists solved a problem that has confounded engineers and scientists for decades: Individual nano-size building blocks such as nanotubes, nanosheets and nanorods are ultrastrong. But larger materials made out of bonded nano-size building blocks were comparatively weak. Until now.’

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Plastic Steel: Light and Transparent but Strong as Steel

Two Nanotechnology Breakthroughs from IBM: Single-Atom Data Storage and Molecular Computers

Jorge Goncalves — Fri, 31 Aug 2007 18:59:24 +0000

IBM Unveils Two Major Nanotechnology Breakthroughs as Building Blocks for Atomic Structures and Devices – Magnetic Atom Milestone Brings Single-Atom Data Storage Closer to Reality; Single-Molecule Switching Could Lead to Molecular Computers. ‘IBM announced two major scientific achievements in the field of nanotechnology that could one day lead to new kinds of devices and structures built from a few atoms or molecules.

Although still far from making their way into products, these breakthroughs will enable scientists at IBM and elsewhere to continue driving the field of nanotechnology, the exploration of building structures and devices out of ultra-tiny, atomic-scale components. Such devices might be used as future computer chips, storage devices, sensors and for applications nobody has imagined yet. The work will be unveiled tomorrow in two reports being published by the journal Science.

In the first report, IBM scientists describe major progress in probing a property called magnetic anisotropy in individual atoms. This fundamental measurement has important technological consequences because it determines an atom’s ability to store information. Previously, nobody had been able to measure the magnetic anisotropy of a single atom.
With further work it may be possible to build structures consisting of small clusters of atoms, or even individual atoms, that could reliably store magnetic information. Such a storage capability would enable nearly 30,000 feature length movies or the entire contents of YouTube – millions of videos estimated to be more than 1,000 trillion bits of data – to fit in a device the size of an iPod. Perhaps more importantly, the breakthrough could lead to new kinds of structures and devices that are so small they could be applied to entire new fields and disciplines beyond traditional computing.

In the second report, IBM researchers unveiled the first single-molecule switch that can operate flawlessly without disrupting the molecule’s outer frame – a significant step toward building computing elements at the molecular scale that are vastly smaller, faster and use less energy than today’s computer chips and memory devices.
In addition to switching within a single molecule, the researchers also demonstrated that atoms inside one molecule can be used to switch atoms in an adjacent molecule, representing a rudimentary logic element. This is made possible partly because the molecular framework is not disturbed.’

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Two Nanotechnology Breakthroughs from IBM: Single-Atom Data Storage and Molecular Computers

Nanofluids: No “Magic” Cooling Capabilities

Jorge Goncalves — Fri, 31 Aug 2007 18:29:10 +0000

Not so super-cool after all: MIT researchers knock down theory about nanofluids. ‘MIT engineers have shown that nanofluids, which once held promise as a super-coolant, do not have the theoretical cooling capabilities many scientists believed they had.

Nanofluids are suspensions of tiny particles on the nanometer, or billionth of a meter, scale. When nanofluids were first engineered in the early 1990s, experiments showed that their thermal conductivity – a measure of their heat-removing capability – was much higher than expected.

Several new theories were offered in recent years to explain this anomalous behavior. Among them, the “microconvection” theory predicted an astonishing increase of several orders in the thermal conductivity of the fluid just by adding light nanoparticles less than ten nanometers in size.

MIT researchers recently conducted experiments to test the microconvection effect and found that nanofluids in fact do not have the advanced cooling properties ascribed to them. The team reports its findings in the Aug. 31 issue of Physical Review Letters.’

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Nanofluids: No “Magic” Cooling Capabilities

Call for Public Comments: Prioritization of Environmental, Health, and Safety Research Needs for Engineered Nanoscale Materials

Jorge Goncalves — Sat, 18 Aug 2007 23:36:22 +0000

Prioritization of Environmental, Health, and Safety Research Needs for Engineered Nanoscale Materials (PDF). The National Nanotechnology Coordination Office (NNCO), on behalf of the Nanoscale Science, Engineering, and Technology (NSET) Subcommittee of the Committee on Technology, National Science and Technology Council (NSTC), is requesting public comments on the newly released document Prioritization of Environmental, Health, and Safety Research Needs for Engineered Nanoscale Materials. Comments can be submitted through September 17, 2007.

This is a post from Science Quick Picks, a blog with quick links to the world of Science.

Call for Public Comments: Prioritization of Environmental, Health, and Safety Research Needs for Engineered Nanoscale Materials

Science Quick Picks » Nanotechnology

Another Stunning Graphene Experimental Surprise

Related posts

OECD on Risks and Benefits of Nanomaterials

Related posts

New Fluorescent Silicon Nanoparticles

Related posts

Next Generation Nanofilms

Related posts

On the Road to an Antitumor Vaccine

Related posts

Identifying Tumors with Gold Nanoparticles and ScFv Peptides

Related posts

Plastic Steel: Light and Transparent but Strong as Steel

Related posts

Two Nanotechnology Breakthroughs from IBM: Single-Atom Data Storage and Molecular Computers

Related posts

Nanofluids: No “Magic” Cooling Capabilities

Related posts

Call for Public Comments: Prioritization of Environmental, Health, and Safety Research Needs for Engineered Nanoscale Materials

Related posts