David Kirkpatrick

September 10, 2010

Single ions crossing a nano bridge

Filed under: Science — Tags: , , , , , — David Kirkpatrick @ 11:11 am

Don’t see any current practical applications — aside from desalination — on this right now (but now with a proof-of-concept I bet this’ll be leveraged in new research), but it is impressively cool.

From the link:

In the Sept. 10 issue of Science, MIT researchers report that charged molecules, such as the sodium and  that form when salt is dissolved in water, can not only flow rapidly through carbon nanotubes, but also can, under some conditions, do so one at a time, like people taking turns crossing a bridge. The research was led by associate professor Michael Strano.

The new system allows passage of much smaller molecules, over greater distances (up to half a millimeter), than any existing nanochannel. Currently, the most commonly studied nanochannel is a silicon nanopore, made by drilling a hole through a silicon membrane. However, these channels are much shorter than the new nanotube channels (the nanotubes are about 20,000 times longer), so they only permit passage of large molecules such as DNA or polymers — anything smaller would move too quickly to be detected.

Strano and his co-authors — recent PhD recipient Chang Young Lee, graduate student Wonjoon Choi and postdoctoral associate Jae-Hee Han — built their new nanochannel by growing a nanotube across a one-centimeter-by-one-centimeter plate, connecting two water reservoirs. Each reservoir contains an electrode, one positive and one negative. Because electricity can flow only if protons — positively charged , which make up the electric current — can travel from one electrode to the other, the researchers can easily determine whether  are traveling through the nanotube.

September 6, 2010

Self-assembling and reassembling solar cells

Okay, just yesterday I blogged that a lot of the time the mundane “a ha” moment that puts together well-known materials and processes leads to scientific advancement (the case I was referring to in the post was a simple acid bath technique that made creating solar cells much cheaper). And then again sometimes the big sexy breakthrough gets the headline (as usual) and really deserves it.

If this technique for solar cells that self-assembles the light-harvesting element in the cell, and then breaks it down for re-assembly essentially copying what plants do in their chloroplast, is able to reach acceptable levels of efficiency, it will be an absolute game-changer. Instead of a solar cell that’s (hopefully) constantly bombarded with the full effect of the sun and constantly degrading under the solar assault, these cells will essentially be completely renewed by each reassembly. No degradation over time, just a brand new light-harvesting element with a relatively simple chemical process.

From the second link:

The system Strano’s team produced is made up of seven different compounds, including the carbon nanotubes, the phospholipids, and the proteins that make up the reaction centers, which under the right conditions spontaneously assemble themselves into a light-harvesting structure that produces an electric current. Strano says he believes this sets a record for the complexity of a self-assembling system. When a surfactant — similar in principle to the chemicals that BP has sprayed into the Gulf of Mexico to break apart oil — is added to the mix, the seven components all come apart and form a soupy solution. Then, when the researchers removed the surfactant by pushing the solution through a membrane, the compounds spontaneously assembled once again into a perfectly formed, rejuvenated photocell.

“We’re basically imitating tricks that nature has discovered over millions of years” — in particular, “reversibility, the ability to break apart and reassemble,” Strano says. The team, which included postdoctoral researcher Moon-Ho Ham and graduate student Ardemis Boghossian, came up with the system based on a theoretical analysis, but then decided to build a prototype cell to test it out. They ran the cell through repeated cycles of assembly and disassembly over a 14-hour period, with no loss of efficiency.

September 1, 2010

Nanotech making water more safe

This development can make a real quality of life difference in developing countries without running water and disaster areas, and it can make “roughing it” just a little bit less rough.

The release:

High-speed filter uses electrified nanostructures to purify water at low cost

IMAGE: This scanning electron microscope image shows the silver nanowires in which the cotton is dipped during the process of constructing a filter. The large fibers are cotton.

Click here for more information.

By dipping plain cotton cloth in a high-tech broth full of silver nanowires and carbon nanotubes, Stanford researchers have developed a new high-speed, low-cost filter that could easily be implemented to purify water in the developing world.

Instead of physically trapping bacteria as most existing filters do, the new filter lets them flow on through with the water. But by the time the pathogens have passed through, they have also passed on, because the device kills them with an electrical field that runs through the highly conductive “nano-coated” cotton.

In lab tests, over 98 percent of Escherichia coli bacteria that were exposed to 20 volts of electricity in the filter for several seconds were killed. Multiple layers of fabric were used to make the filter 2.5 inches thick.

“This really provides a new water treatment method to kill pathogens,” said Yi Cui, an associate professor of materials science and engineering. “It can easily be used in remote areas where people don’t have access to chemical treatments such as chlorine.”

Cholera, typhoid and hepatitis are among the waterborne diseases that are a continuing problem in the developing world. Cui said the new filter could be used in water purification systems from cities to small villages.

Faster filtering by letting bacteria through

Filters that physically trap bacteria must have pore spaces small enough to keep the pathogens from slipping through, but that restricts the filters’ flow rate.

IMAGE: This is professor of materials science and engineering Yi Cui.

Click here for more information.

Since the new filter doesn’t trap bacteria, it can have much larger pores, allowing water to speed through at a more rapid rate.

“Our filter is about 80,000 times faster than filters that trap bacteria,” Cui said. He is the senior author of a paper describing the research that will be published in an upcoming issue of Nano Letters. The paper is available online now.

The larger pore spaces in Cui’s filter also keep it from getting clogged, which is a problem with filters that physically pull bacteria out of the water.

Cui’s research group teamed with that of Sarah Heilshorn, an assistant professor of materials science and engineering, whose group brought its bioengineering expertise to bear on designing the filters.

Silver has long been known to have chemical properties that kill bacteria. “In the days before pasteurization and refrigeration, people would sometimes drop silver dollars into milk bottles to combat bacteria, or even swallow it,” Heilshorn said.

Cui’s group knew from previous projects that carbon nanotubes were good electrical conductors, so the researchers reasoned the two materials in concert would be effective against bacteria. “This approach really takes silver out of the folk remedy realm and into a high-tech setting, where it is much more effective,” Heilshorn said.

Using the commonplace keeps costs down

But the scientists also wanted to design the filters to be as inexpensive as possible. The amount of silver used for the nanowires was so small the cost was negligible, Cui said. Still, they needed a foundation material that was “cheap, widely available and chemically and mechanically robust.” So they went with ordinary woven cotton fabric.

“We got it at Wal-mart,” Cui said.

To turn their discount store cotton into a filter, they dipped it into a solution of carbon nanotubes, let it dry, then dipped it into the silver nanowire solution. They also tried mixing both nanomaterials together and doing a single dunk, which also worked. They let the cotton soak for at least a few minutes, sometimes up to 20, but that was all it took.

The big advantage of the nanomaterials is that their small size makes it easier for them to stick to the cotton, Cui said. The nanowires range from 40 to 100 billionths of a meter in diameter and up to 10 millionths of a meter in length. The nanotubes were only a few millionths of a meter long and as narrow as a single billionth of a meter. Because the nanomaterials stick so well, the nanotubes create a smooth, continuous surface on the cotton fibers. The longer nanowires generally have one end attached with the nanotubes and the other end branching off, poking into the void space between cotton fibers.

“With a continuous structure along the length, you can move the electrons very efficiently and really make the filter very conducting,” he said. “That means the filter requires less voltage.”

Minimal electricity required

The electrical current that helps do the killing is only a few milliamperes strong – barely enough to cause a tingling sensation in a person and easily supplied by a small solar panel or a couple 12-volt car batteries. The electrical current can also be generated from a stationary bicycle or by a hand-cranked device.

The low electricity requirement of the new filter is another advantage over those that physically filter bacteria, which use electric pumps to force water through their tiny pores. Those pumps take a lot of electricity to operate, Cui said.

In some of the lab tests of the nano-filter, the electricity needed to run current through the filter was only a fifth of what a filtration pump would have needed to filter a comparable amount of water.

The pores in the nano-filter are large enough that no pumping is needed – the force of gravity is enough to send the water speeding through.

Although the new filter is designed to let bacteria pass through, an added advantage of using the silver nanowire is that if any bacteria were to linger, the silver would likely kill it. This avoids biofouling, in which bacteria form a film on a filter. Biofouling is a common problem in filters that use small pores to filter out bacteria.

Cui said the electricity passing through the conducting filter may also be altering the pH of the water near the filter surface, which could add to its lethality toward the bacteria.

Cui said the next steps in the research are to try the filter on different types of bacteria and to run tests using several successive filters.

“With one filter, we can kill 98 percent of the bacteria,” Cui said. “For drinking water, you don’t want any live bacteria in the water, so we will have to use multiple filter stages.”

Cui’s research group has gained attention recently for using nanomaterials to build batteries from paper and cloth.

###

David Schoen and Alia Schoen were both graduate students in Materials Science and Engineering when the water-filter research was conducted and are co–lead authors of the paper in Nano Letters. David Schoen is now a postdoctoral researcher at Stanford.

Liangbing Hu, a postdoctoral researcher in Materials Science and Engineering, and Han Sun Kim, a graduate student in Materials Science and Engineering at the time the research was conducted, also contributed to the research and are co-authors of the paper.

August 18, 2010

The world’s darkest material

I’ve previously blogged on a world’s darkest material in the past (couldn’t find the post in the archives, however) and it was nanotech-based as well so it’s possible this is the same stuff. Pretty cool either way.

From the link:

Harnessing darkness for practical use, researchers at the National Institute of Standards and Technology have developed a laser power detector coated with the world’s darkest material — a forest of carbon nanotubes that reflects almost no light across the visible and part of the infrared spectrum.

NIST will use the new ultra-dark detector, described in a new paper in ,* to make precision laser power measurements for advanced technologies such as optical communications, laser-based manufacturing, solar energy conversion, and industrial and satellite-borne sensors.

Inspired by a 2008 paper by Rensselaer Polytechnic Institute (RPI) on “the darkest man-made material ever,”** the NIST team used a sparse array of fine nanotubes as a coating for a thermal detector, a device used to measure . A co-author at Stony Brook University in New York grew the nanotube coating. The coating absorbs  and converts it to heat, which is registered in pyroelectric material (lithium tantalate in this case). The rise in temperature generates a current, which is measured to determine the power of the laser. The blacker the coating, the more efficiently it absorbs light instead of reflecting it, and the more accurate the measurements.

This is a colorized micrograph of the world’s darkest material — a sparse “forest” of fine carbon nanotubes — coating a NIST laser power detector. Image shows a region approximately 25 micrometers across. Credit: Aric Sanders, NIST

July 17, 2010

Manufacturing carbon nanotubes at room temperature

This document outlines a method of creating carbon nanotubes that doesn’t require high temperature or pressure. This potentially will dramtically lower the cost of manufacturing carbon nanotubes.

From the link:

We develop a new chemical route to carbon nanotubes at room temperature. Graphite powder was immersed in a mixed solution of nitric and sulphuric acid with potassium chloride. After heating the solution up to 70‰ and leaving them in the air for 3 days, we obtained carbon nanotube bundles. The process could readily give an easy way of preparing carbon nanotubes without high temperature and high pressure. We develop a new chemical route to carbon nanotubes at room temperature. Graphite powderwas immersed in a mixed solution of nitric and sulphuric acid with potassium chloride. After heatingthe solution up to 70‰ and leaving them in the air for 3 days, we obtained carbon nanotube bundles.The process could readily give an easy way of preparing carbon nanotubes without high temperatureand high pressure.
And:
In summary, we have presented a simple chemical method for producing CNTs in liquid solution at 70‰ without any pressure treatment. The CNTs form bundles containing crystalized and multi-walled single CNTs with a diameter of around 14.6nm. The electron diffraction patterns demonstrate its zigzag edge structure. We expect this new synthesizing method may produce cheap CNTs and as a result open an easy access to the industrial device based on CNTs.
Here’s an illustration and an image from the link:
FIG. 1: (a) mixture of graphite, sulfuric acid (H2SO4, and nitric acid (HNO3). (b) potassium chlorate (KClO3) was put in the solution. (c) floating carbons produced from the pro- cess (b) were transferred into DI water. (d) the sample was dried after filtration. The process (b) and (c) were repeated 4 times.

FIG. 3: (a) transmission electron microscope (TEM) images of CMT bundles. Panels (b) and (c) magnificently present the regions pointed by number 1 and 2 in panel (a), respectively. A single CNT noticed by an arrow in panel (b) proves CNT’s flexibility. (d) the enlarged region of panel (c) (arrow 3), revealing a multi-walled nanotube with a diameter of 14.6nm.

July 15, 2010

Nanotech improves submarine sonar

Filed under: et.al. — Tags: , , , , , — David Kirkpatrick @ 2:05 am

Carbon nanotubes really are an amazing material.

The release:

Submarines could use new nanotube technology for sonar and stealth

IMAGE: Submarines of the future could be equipped with “nanotube speakers ” to help improve sonar to probe the ocean depths and make the vessels invisible to enemies.

Click here for more information.

Speakers made from carbon nanotube sheets that are a fraction of the width of a human hair can both generate sound and cancel out noise — properties ideal for submarine sonar to probe the ocean depths and make subs invisible to enemies. That’s the topic of a report on these “nanotube speakers,” which appears in ACS’ Nano Letters, a monthly journal.

Ali Aliev and colleagues explain that thin films of nanotubes can generate sound waves via a thermoacoustic effect. Every time that an electrical pulse passes through the microscopic layer of carbon tubes, the air around them heats up and creates a sound wave. Chinese scientists first discovered that effect in 2008, and applied it in building flexible speakers. In a remarkable demonstration, which made its way onto YouTube, the Chinese nanoscientists stuck a sheet of nanotubes onto the side of a flag, and attached it to an mp3 player. They used the nanotube-coated flag to play a song while it flapped in the breeze. But they did not test its ability to operate under water.

Aliev’s group took that step, showing that nanotube sheets produce the kind of low-frequency sound waves that enable sonar to determine the location, depth, and speed of underwater objects. They also verified that the speakers can be tuned to specific frequencies to cancel out noise, such as the sound of a submarine moving through the depths.

###

ARTICLE FOR IMMEDIATE RELEASE “Underwater Sound Generation Using Carbon Nanotube Projectors”

DOWNLOAD FULL TEXT ARTICLE http://pubs.acs.org/stoken/presspac/presspac/full/10.1021/nl100235n

June 4, 2010

A cyborg transistor

Via KurzweilAI.net — Interesting, if not a little bit creepy.

Part-human, part-machine transistor devised
Discovery News, June 2, 2010

University of California, Merced scientists have embedded a carbon nanotube-based transistor inside a lipid bilayer (cell-like membrane) and powered it with an ion pump and a solution of adenosine triphosphate (ATP) to fuel the ion pump.


Artist’s representation of a new transistor that’s contained within a cell-like membrane (Scott Dougherty, LLNL)

The research could lead to new types of man-machine interactions where embedded devices could relay information about the inner workings of disease-related proteins or toxins inside the cell membrane, and eventually even treat diseases. It could also lead to new ways to read, and even influence, brain or nerve cells.

The headline is misleading — the device is simply biomimetic. – Ed.
Read Original Article>>

May 27, 2010

More nanotech medical treatment

Filed under: Science, Technology — Tags: , , , , , — David Kirkpatrick @ 4:23 pm

Both via KurzweilAI.net, and both as a follow-up to my previous post on killing tumors with gold nanoparticles.

First up is using carbon nanotubes as a radiotherapy delivery system:

Nanocapsule delivers radiotherapy
PhysOrg.com, May 26, 2010

Oxford University chemists have encapsulated radionuclides within carbon nanotubes and set new records for highly concentrated in vivo radiodosage, while demonstrating zero leakage of isotopes to high-affinity organs, such as the thyroid.


Artist’s rendition of nanocapsules (Gerard Tobias)
Read Original Article>>

And second is using nanoporous particles as a molecular therapy deliver system to tumors:

Nanoporous Particles Deliver Novel Molecular Therapies to Tumors
PhysOrg.com, May 26, 2010

Using nanoporous silicon particles, two teams of investigators have created drug delivery vehicles capable of ferrying labile molecular therapies deep into the body, creating new opportunities for developing innovative anticancer therapies.
Read Original Article>>

April 21, 2010

More cancer-fighting nanotech

Filed under: Science, Technology — Tags: , , , , , , — David Kirkpatrick @ 1:26 am

Research has found carbon nanotubes can help the body’s immune system fight cancer. Hit this link for all my cancer-related nanotechnology blogging.

From the first link:

Carbon nanotubes boost cancer-fighting cells

New Haven, Conn.—Yale University engineers have found that the defects in carbon nanotubes cause T cell antigens to cluster in the blood and stimulate the body’s natural immune response. Their findings, which appear as the cover article of the April 20 issue of the journal Langmuir, could improve current adoptive immunotherapy, a treatment used to boost the body’s ability to fight cancer.

Adoptive immunotherapy involves extracting a patient’s blood so that the number of naturally occurring T cells (a type of white blood cell) can reproduce more effectively in the laboratory. Although the body produces its own tumor-fighting T cells, they are often suppressed by the tumor and are too few to be effective. Scientists boost the production of T cells outside the body using different substances that encourage T cell antigens to cluster in high concentrations. The better these substances are at clustering T cell antigens, the greater the immune cell proliferation. Once enough T cells are produced, the blood is transferred back into the patient’s body.

The Yale team had previously reported the unexpected effect that carbon nanotubes had on T cell production. They found that the antigens, when presented on the surface of the nanotubes, stimulated T cell response far more effectively than coating other substrates such as polystyrene in the antigens, even though the total amount of antigens used remained the same.

Now they have discovered the reason behind the increased stimulation. They found that the antigens cluster in high concentrations around the tiny defects found in the carbon nanotubes.

“Carbon nanotube bundles resemble a lymph node microenvironment, which has a labyrinth sort of geometry,” said Tarek Fahmy, associate professor of chemical engineering and biomedical engineering at Yale and senior author of the paper. “The nanotube bundles seem to mimic the physiology and adsorb more antigens, promoting a greater immunological response.”

Current adoptive immunotherapy takes weeks to produce enough T cells, but lab tests showed that the nanotubes produced the same T cell concentration in just one-third the time, Fahmy said.

Carbon nanotubes can cause problems, such as an embolism, when used in the body. But this isn’t the case when they are used in blood that has been extracted from the patient, Fahmy said. Next, the team will work on a way to effectively remove the carbon nanotubes from the blood before it is returned to the patient.

“We think this is a really interesting use of carbon nanotubes. It’s a way to exploit the unique properties of this material for biological application in a safe way.”

###

Other authors of the paper include lead author Tarek Fadel, Michael Look, Peter Staffier, Gary Haller and Lisa Pfefferle, all of the Yale School of Engineering & Applied Science.

April 18, 2010

Carbon nanotubes and new states of matter

Now this is some fascinating research on carbon nanotube properties.

From the link:

“For the first time, fields of study relating both to cold atoms and to the nanoscale have intersected,” Lene Vestergaard Hau tells PhysOrg.com. “Even though both have been active areas of research, cold atoms have not been brought together with nanoscale structures at the single nanometer level. This is a totally new system.”

Hau is the Mallinckrodt Professor of Physics and Applied Physics at Harvard University. Along with colleague J.A. Golovchenko, and graduate students Anne Goodsell and Trygve Ristroph, who are in her lab at Harvard, Hau was able to set up an experiment that allows for the observation of capture and field ionization of cold atoms. Their work can be found in : “Field  of Cold Atoms near the Wall of a Single Carbon Nanotube.”

And:

“When the electron is pulled in, it goes through a tunneling process,” Hau explains. “It has to go through areas that are classically forbidden. The process is quantum mechanical. We can observe the interaction of the atom and the nanotube as the electron is trying to tunnel, and this offers us a chance to peek at some of the interesting dynamics that happen at the nanoscale.”

Another possibility is that this combination of cold atoms with  could lead to new states of matter. “Since we now know how to suck atoms into orbit at such high spin rates, it could lead to a new state of cold-atomic matter that could be super interesting to study,” Hau points out.

Practical applications?:

Practically, this new system has potential as well. “We could make very sensitive detectors,” Hau says. “Things like ‘atom sniffers’ that detect trace gases could be an application for this work. Additionally, the possibility of single nanometer precision means super high spatial resolution. This system could be used in interferometers — interferometers built on a single chip and based on , which would be of importance for navigation, for example.”

For the raw material, here’s the release the linked article sprung from.

April 6, 2010

Nanotech and medicine

New research on how carbon nanotubes may be used in medical applications.

The release:

[PRESS RELEASE, 5 April 2010] A team of Swedish and American scientists has shown for the first time that carbon nanotubes can be broken down by an enzyme – myeloperoxidase (MPO) – found in white blood cells. Their discoveries are presented in Nature Nanotechnology and contradict what was previously believed, that carbon nanotubes are not broken down in the body or in nature. The scientists hope that this new understanding of how MPO converts carbon nanotubes into water and carbon dioxide can be of significance to medicine.

“Previous studies have shown that carbon nanotubes could be used for introducing drugs or other substances into human cells,” says Bengt Fadeel, associate professor at the Swedish medical university Karolinska Institutet. “The problem has been not knowing how to control the breakdown of the nanotubes, which can caused unwanted toxicity and tissue damage. Our study now shows how they can be broken down biologically into harmless components.”

Carbon nanotubes are a material consisting of a single layer of carbon atoms rolled into a tube with a diameter of only a couple of nanometres (1 nanometer = 1 billionth of a metre) and a length that can range from tens of nanometres up to several micrometers. Carbon nanotubes are lighter and stronger than steel, and have exceptional heat-conductive and electrical properties. They are manufactured on an industrial scale, mainly for engineering purposes but also for some consumer products.

Carbon nanotubes were once considered biopersistent in that they did not break down in body tissue or in nature. In recent years, research has shown that laboratory animals exposed to carbon nanotubes via inhalation or through injection into the abdominal cavity develop severe inflammation. This and the tissue changes (fibrosis) that exposure causes lead to impaired lung function and perhaps even to cancer. For example, a year or two ago, alarming reports by other scientists suggested that carbon nanotubes are very similar to asbestos fibres, which are themselves biopersistent and which can cause lung cancer (mesothelioma) in humans a considerable time after exposure.

This current study thus represents a breakthrough in nanotechnology and nanotoxicology, since it clearly shows that endogenous MPO can break down carbon nanotubes. This enzyme is expressed in certain types of white blood cell (neutrophils), which use it to neutralise harmful bacteria. Now, however, the researchers have found that the enzyme also works on carbon nanotubes, breaking them down into water and carbon dioxide. The researchers also showed that carbon nanotubes that have been broken down by MPO no longer give rise to inflammation in mice.

“This means that there might be a way to render carbon nanotubes harmless, for example in the event of an accident at a production plant,” says Dr Fadeel. “But the findings are also relevant to the future use of carbon nanotubes for medical purposes.”

The study was led by researchers at Karolinska Institutet, the University of Pittsburgh and the National Institute for Occupational Safety and Health (NIOSH), and was financed in part through grants from the National Institutes of Health (NIH) and the Seventh Framework Programme of the European Commission. The work was conducted as part of the NANOMMUNE project, which is coordinated by associate professor Bengt Fadeel of the Institute of Environmental Medicine, Karolinska Institutet, and which comprises a total of thirteen research groups in Europe and the USA.

March 7, 2010

Carbon nanotubes open new area of energy research

Nanotechnology is revolutionizing how we see and deal with electricity, everything from storage to wiring. Now a team at MIT has discovered carbon nanotubes produce electricity in an entirely new way, opening a brand new area in energy research.

From the final link:

A team of scientists at MIT have discovered a previously unknown phenomenon that can cause powerful waves of energy to shoot through minuscule wires known as carbon nanotubes. The discovery could lead to a new way of producing electricity, the researchers say.

The phenomenon, described as thermopower waves, “opens up a new area of energy research, which is rare,” says Michael Strano, MIT’s Charles and Hilda Roddey Associate Professor of Chemical Engineering, who was the senior author of a paper describing the new findings that appeared in  on March 7. The lead author was Wonjoon Choi, a doctoral student in mechanical engineering.

Like a collection of flotsam propelled along the surface by waves traveling across the ocean, it turns out that a thermal wave — a moving pulse of heat — traveling along a microscopic wire can drive electrons along, creating an electrical current.

The key ingredient in the recipe is carbon nanotubes — submicroscopic hollow tubes made of a chicken-wire-like lattice of carbon atoms. These tubes, just a few billionths of a meter () in diameter, are part of a family of novel carbon molecules, including buckyballs and graphene sheets, that have been the subject of intensive worldwide research over the last two decades.

February 23, 2010

Metal-free carbon nanotube production

Via KurzweilAI.net — I’ll just let the quoted bit below do all the explaining …

A Stellar, Metal-Free Way to Make Carbon Nanotubes
Physorg.com, Feb. 22, 2010

A new method of growing carbon nanotubes without requiring platinum or another metal as a catalyst has been developed by researchers at NASA‘s Goddard  Center.

The carbon nanotubes are produced when graphite dust particles are exposed to a mixture of carbon monoxide and hydrogen gases.

The method was suggested by a 2008 discovery that the long, thin carbon structures known as graphite whiskers — essentially, bigger cousins of carbon nanotubes — were identified in three meteorites. Researchers suspect that it could have produced at least some of the simple carbon-based compounds in the early solar system.

The work also could help researchers understand puzzling observations about some supernovas.


Nanotubes grown on graphite (Yuki Kimura, Tohoku University)


Read Original Article>>

December 9, 2009

Want a lightweight battery? Try nanotech paper on for size

Filed under: Science, Technology — Tags: , , , — David Kirkpatrick @ 5:02 pm

If this becomes market-ready, it’ll blow the walls off size and weight issues with portable devices. One more amazing use for carbon nanotubes.

From the link:

Ordinary paper can be turned into a battery electrode simply by dipping it into carbon-nanotube inks. The resulting electrodes, which are strong, flexible, and highly conductive, might be used to make cheap energy storage devices to power portable electronics.

It’s now possible to print lightweight circuits and screens for electronics like e-readers, but conventional batteries still weigh these devices down. Carbon nanotubes are a promising material for printing batteries because, in addition to their strength, light weight, and conductivity, they can store a large amount of energy–a quality that helps portable electronics run longer between charges.

Now a group of Stanford University researchers, led by materials science professor Yi Cui, have demonstrated that ordinary office paper soaks up carbon nanotubes like a sponge and can be turned into electrodes for batteries and supercapacitors. The advantage of paper, says Cui, is that it’s cheap and interacts strongly with nanotubes without the need for putting additives in the ink. “We take advantage of the porous structure of paper,” says Cui. “Carbon nanotubes absorb into the paper and stick on really tightly.”

December 8, 2009

Nanotech in space

Well, theoretically in space in the form of improving ion-propulsion systems. In reality if interstellar, or even travel within the solar system beyond Mars, has any hope feasibility, it’s going to require a major breakthrough in getting from point A (ostensibly Earth) and point B. It’ll be interesting to see where emerging science like nanotech will take us. We’re already seeing actual medical, electronics and other uses for nanotechnology. I do a lot of nanotech blogging because the field is so exciting and still harbors untold potential.

From the first link:

Ion-propulsion systems have propelled a handful of Earth-orbiting and interplanetary spacecraft over the past 50 years. Now researchers at Georgia Institute of Technology are developing more efficient ion thrusters that use carbon nanotubes for a vital component

Ion propulsion works by accelerating electrically charged, or ionized, particles to propel a spacecraft. One of the most common ion engines, known as a “Hall Effect” thruster, ionizes gas using electrons trapped in a magnetic field. The resulting ions are then accelerated using the potential maintained between an anode and a cathode. But some of the emitted electrons must also be used to neutralize the ions in the plume emitted from the spacecraft, to prevent the spacecraft from becoming electrically charged. Existing Hall Effect thrusters must use about 10 percent of the spacecraft’s xenon gas propellant to create the electrons needed to both run the engine and neutralize the ion beam.

The Georgia Tech researchers created a field emission cathode for the thruster using carbon nanotubes. In this type of cathode, electrons are emitted after they tunnel through a potential barrier. The carbon nanotube design is especially efficient because nanotubes are incredibly strong and electrically conductive. “By using carbon nanotubes, we can get all the electrons we need without using any propellant,” says Mitchell Walker, principal investigator of the project and an assistant professor in the High-Power Electric Propulsion Laboratory at Georgia Tech. This means that 10 percent more of the ion thruster’s propellant is available for the actual mission, extending a spacecraft’s lifetime.


Efficient emitters: A micrograph of square arrays of carbon nanotubes on a one centimeter by one centimeter silicon wafer. The arrays are designed for use in an experimental cathode.
Credit: Georgia Institute of Technology

December 1, 2009

Carbon nanotubes capture CO2

Filed under: Business, Science, Technology — Tags: , , , , — David Kirkpatrick @ 1:42 am

Nanotech provides a solution to yet another vexing problem.

From the link:

Membranes made with carbon nanotubes could reduce the amount of energy needed to capture carbon-dioxide emissions from smokestacks, and therefore cut costs, according to a company that will receive $1 million from the new advanced-research projects agency for energy, Arpa-e, to develop the technology.

The company, Hayward, CA-based Porifera, claims that its carbon-nanotube membranes could capture one billion to three billion tons of carbon dioxide a year and save $10 billion a year compared to existing CO2 capture technology. At this point, however, the work is at an early stage, says Olgica Bakajin, Porifera’s chief technology officer. She expects that it will be another year before the first prototype is ready.

November 21, 2009

Carbon nanotube supercapacitors

Flawed carbon nanotubes may lead to supercapacitors.

From the link:

Most people would like to be able to charge their cell phones and other personal electronics quickly and not too often. A recent discovery made by UC San Diego engineers could lead to carbon nanotube-based supercapacitors that could do just this.

In recent research, published in , Prabhakar Bandaru, a professor in the UCSD Department of Mechanical and Aerospace Engineering, along with graduate student Mark Hoefer, have found that artificially introduced defects in nanotubes can aid the development of supercapacitors.

“While batteries have large , they take a long time to charge; while electrostatic capacitors can charge quickly but typically have limited capacity. However, supercapacitors/electrochemical capacitors incorporate the advantages of both,” Bandaru said.

Of course I mostly ran this post just to add to the excuse for running this awesome image of a carbon nanotube. Earlier this week I featured an incredible image of graphene. We’re getting some just simply amazing looks into the atomic world right now. And it’ll only get better.

Carbon nanotubes could serve as supercapacitor electrodes with enhanced charge and energy storage capacity (inset: a magnified view of a single carbon nanotube).

Credit: UC San Diego

November 10, 2009

Carbon nanotubes are the wiring of the future

Filed under: et.al. — Tags: , , , , — David Kirkpatrick @ 3:16 pm

Previously I’ve blogged about carbon nanotubes replacing copper wiring, and here’s news of a new manufacturing technique that gets that idea closer to the mainstream. This shift in wiring is most likely a “when” instead of an “if.”

From the second link:

A new method for assembling carbon nanotubes has been used to create fibers hundreds of meters long. Individual carbon nanotubes are strong, lightweight, and electrically conductive, and could be valuable as, among other things, electrical transmission wires. But aligning masses of the nanotubes into well-ordered materials such as fibers has proven challenging at a scale suitable for manufacturing. By processing carbon nanotubes in a solution called a superacid, researchers at Rice University have made long fibers that might be used as lightweight, efficient wires for the electrical grid or as the basis of structural materials and conductive textiles.

Others have made carbon-nanotube fibers by pulling the tubes from solid hair-like arrays or by spinning them like wool as they emerge from a chemical reactor. The problem with starting from a solid, says Rice chemical engineering professor Matteo Pasquali, is that “the alignment is not spectacular, and these methods are difficult to scale up.” The better aligned and ordered the individual nanotubes in a larger structure, the better the collective structure’s electrical and mechanical properties. Using the Rice methods, well-aligned nanotube fibers can be made on a large scale, shot out from a nozzle similar to a showerhead.

The late Nobel laureate Richard Smalley started the Rice project in 2001. Smalley knew solution-processing would be a good way to assemble nanotube fibers and films because of nanotubes’ shape. Carbon nanotubes are much longer than they are wide, so when they’re in a flowing solution, they line up like logs floating down a river. But carbon nanotubes aren’t soluble in conventional solvents. The Rice group laid the foundations for liquid processing of the nanotubes five years ago, when they discovered that sulfuric acid brings the nanotubes into solution by coating their surfaces with positively charged ions.


Nanotube fiber: This fiber, which is about 40 micrometers in diameter, is made up of carbon nanotubes.
Credit: Rice University

November 3, 2009

Breakthrough in large-scale nanotube processing

Via KurzweilAI.net — These manufacturing breakthroughs aren’t as exciting and sexy as a groundbreaking medical application or replacing copper wiring with carbon nanotubes or graphene, but they are key to turning nanotechnology into a viable industry.

Breakthrough In Industrial-scale Nanotube Processing
ScienceDaily, Nov. 3, 2009

Rice University scientists have unveiled a method for high-throughput industrial-scale processing of carbon-nanotube fibers, using chlorosulfonic acid as a solvent.

The process that could lead to revolutionary advances in materials science, power distribution and nanoelectronics.

 

Read Original Article>>

October 5, 2009

Carbon nanotubes make tomatos germinate faster

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 3:02 pm

Via KurzweilAI.net — I’ll have to say the idea carbon nanotubes “appear to penetrate the thick seed coat” is one of those cautionary details on nanotech.

A sprinkling of nanotubes makes plants shoot up

New Scientist Tech, Oct. 4, 2009

Tomato seeds planted in growth medium that contained carbon nanotubes germinated sooner and seedlings grew faster, University of Arkansas researchers have found.

The nanotubes appear to penetrate the thick seed coat, which would allow water to enter the dry seeds more rapidly.

Read Original Article>>

September 21, 2009

Getting carbon nanotubes under control

Filed under: Science, Technology — Tags: , , , — David Kirkpatrick @ 3:47 pm

An important aspect of creating nanotubes is controlling their atomic-level structure. Looks like these researchers have found a solution to the issue.

From the link:

Single‐walled carbon nanotubes, made of a cheap and abundant material, have so much potential because their function changes when their atomic‐level structure, referred to as chirality, changes.

But for all their promise, building tubes with the right structure has proven a challenge.

A pair of Case Western Reserve University researchers mixed metals commonly used to grow nanotubes 
and found that the composition of the catalyst can control the chirality.

In a letter to be published Sept. 20 in the online edition of Nature Materials, R. Mohan Sankaran, an assistant professor of chemical engineering at the Case School of Engineering, and Wei‐Hung Chiang, who received his doctorate degree in chemical engineering in May, describe their findings.

“We have established a link between the structure of a catalyst and the chirality of carbon nanotubes,” 
Sankaran said. “Change the catalyst structure by varying its composition, and you can begin to control the chirality of the nanotubes and their electrical and optical properties.”

The chirality of a single‐walled  describes how a lattice of carbon  is rolled into a tube. The rolling can occur at different angles, producing different structures that exhibit very different properties.

Nanotubes are normally grown in bulk mixtures. When using a nickel catalyst, typically one‐third of those grown are metallic and could be used like metal wires to conduct electricity. About two‐thirds are semiconducting nanotubes, which could be used as transistors, Chiang explained. But, separating them according to properties, “is costly and can damage the nanotubes.”

September 11, 2009

Carbon nanotubes and electronics

Via KurzweilAI — This post is a two-fer on nanotech and carbon nanotubes.

From the “two” link:

Using Nanotubes in Computer Chips

PhysOrg.com, Sep. 10, 2009

A simple enough manufacturing process developed by MITresearchers could enable carbon nanotubes to replace the vertical wires in chips, permitting denser packing ofcircuits.

Read Original Article>>

And from the “fer” link:

Capsules for Self-Healing Circuits

Technology Review, Sept. 11, 2009

Nanotube-filled capsules could restore conductivity to damaged electronics, University of Illinois at Urbana-Champaign researchers have found.

Read Original Article>>

August 16, 2009

DNA scaffolding and circuit boards

A release red hot from the inbox:

IBM Scientists Use DNA Scaffolding To Build Tiny Circuit Boards

Nanotechnology advancement could lead to smaller, faster, more energy efficient computer chips

SAN JOSE, Calif., Aug. 17 /PRNewswire-FirstCall/ — Today, scientists at IBM Research (NYSE:IBM) and the California Institute of Technology announced a scientific advancement that could be a major breakthrough in enabling the semiconductor industry to pack more power and speed into tiny computer chips, while making them more energy efficient and less expensive to manufacture.

  (Photo:  http://www.newscom.com/cgi-bin/prnh/20090817/NY62155-a )
  (Photo:  http://www.newscom.com/cgi-bin/prnh/20090817/NY62155-b )
  (Logo:  http://www.newscom.com/cgi-bin/prnh/20090416/IBMLOGO )

IBM Researchers and collaborator Paul W.K. Rothemund, of the California Institute of Technology, have made an advancement in combining lithographic patterning with self assembly – a method to arrange DNA origami structures on surfaces compatible with today’s semiconductor manufacturing equipment.

Today, the semiconductor industry is faced with the challenges of developing lithographic technology for feature sizes smaller than 22 nm and exploring new classes of transistors that employ carbon nanotubes or silicon nanowires. IBM’s approach of using DNA molecules as scaffolding — where millions of carbon nanotubes could be deposited and self-assembled into precise patterns by sticking to the DNA molecules – may provide a way to reach sub-22 nm lithography.

The utility of this approach lies in the fact that the positioned DNA nanostructures can serve as scaffolds, or miniature circuit boards, for the precise assembly of components – such as carbon nanotubes, nanowires and nanoparticles – at dimensions significantly smaller than possible with conventional semiconductor fabrication techniques. This opens up the possibility of creating functional devices that can be integrated into larger structures, as well as enabling studies of arrays of nanostructures with known coordinates.

“The cost involved in shrinking features to improve performance is a limiting factor in keeping pace with Moore’s Law and a concern across the semiconductor industry,” said Spike Narayan, manager, Science & Technology, IBM Research – Almaden. “The combination of this directed self-assembly with today’s fabrication technology eventually could lead to substantial savings in the most expensive and challenging part of the chip-making process.”

The techniques for preparing DNA origami, developed at Caltech, cause single DNA molecules to self assemble in solution via a reaction between a long single strand of viral DNA and a mixture of different short synthetic oligonucleotide strands. These short segments act as staples – effectively folding the viral DNA into the desired 2D shape through complementary base pair binding. The short staples can be modified to provide attachment sites for nanoscale components at resolutions (separation between sites) as small as 6 nanometers (nm). In this way, DNA nanostructures such as squares, triangles and stars can be prepared with dimensions of 100 – 150 nm on an edge and a thickness of the width of the DNA double helix.

IBM uses traditional semiconductor techniques, the same used to make the chips found in today’s computers, to etch out patterns, creating the lithographic templates for this new approach. Either electron beam or optical lithography are used to create arrays of binding sites of the proper size and shape to match those of individual origami structures. The template materials are chosen to have high selectivity so that origami binds only to the patterns of “sticky patches” and nowhere else.

The paper on this work, “Placement and orientation of DNA nanostructures on lithographically patterned surfaces,” by scientists at IBM Research and the California Institute of Technology will be published in the September issue of Nature Nanotechnology and is currently available at: http://www.nature.com/nnano/journal/vaop/ncurrent/abs/nnano.2009.220.html.

For more information about IBM Research, please visit http://www.research.ibm.com/.

To view and download DNA scaffolding images, in high or low resolution, please go to: http://www.thenewsmarket.com/ibm.

Photo:  http://www.newscom.com/cgi-bin/prnh/20090416/IBMLOGO
http://www.newscom.com/cgi-bin/prnh/20090817/NY62155-b
http://www.newscom.com/cgi-bin/prnh/20090817/NY62155-a
PRN Photo Desk, photodesk@prnewswire.com
Source: IBM
  

Web Site:  http://www.research.ibm.com/

June 12, 2009

Assembly with graphene

Interesting research on the properties of one of the more exciting nanotech materials out there.

The release:

Penn materials scientist finds plumber’s wonderland on graphene

IMAGE: This is an electron micrograph showing the formation of interconnected carbon nanostructures on a graphene substrate, which may be harnessed to make future electronic devices.

Click here for more information. 

PHILADELPHIA –- Engineers from the University of Pennsylvania, Sandia National Laboratories and Rice University have demonstrated the formation of interconnected carbon nanostructures on graphene substrate in a simple assembly process that involves heating few-layer graphene sheets to sublimation using electric current that may eventually lead to a new paradigm for building integrated carbon-based devices.

Curvy nanostructures such as carbon nanotubes and fullerenes have extraordinary properties but are extremely challenging to pick up, handle and assemble into devices after synthesis. Penn materials scientist Ju Li and Sandia scientist Jianyu Huang have come up with a novel idea to construct curvy nanostructures directly integrated on graphene, taking advantage of the fact that graphene, an atomically thin two-dimensional sheet, bends easily after open edges have been cut on it, which can then fuse with other open edges permanently, like a plumber connecting metal fittings.

The “knife” and “welding torch” used in the experiments, which were performed inside an electron microscope, was electrical current from a Nanofactory scanning probe, generating up to 2000°C of heat. Upon applying the electrical current to few-layer graphene, they observed the in situ creation of many interconnected, curved carbon nanostructures, such as “fractional nanotube”-like graphene bi-layer edges, or BLEs; BLE rings on graphene equivalent to “anti quantum-dots”; and nanotube-BLE assembly connecting multiple layers of graphene.

Remarkably, researchers observed that more than 99 percent of the graphene edges formed during sublimation were curved BLEs rather than flat monolayer edges, indicating that BLEs are the stable edges in graphene, in agreement with predictions based on symmetry considerations and energetic calculations. Theory also predicts these BLEs, or “fractional nanotubes,” possess novel properties of their own and may find applications in devices.

The study is published in the current issue of the journal Proceedings of the National Academy of Sciences. Short movies of the fabrication of these nanostructures can be viewed at www.youtube.com/user/MaterialsTheory.

Li and Huang observed the creation of these interconnected carbon nanostructures using the heat of electric current and a high-resolution transmission electron microscope. The current, once passed through the graphene layers, improved the crystalline quality and surface cleanness of the graphene as well, both important for device fabrication.

The sublimation of few-layer graphene, such as a 10-layer stack, is advantageous over the sublimation of monolayers. In few-layer graphene, layers spontaneously fuse together forming nanostructures on top of one or two electrically conductive, extended, graphene sheets.

During heating, both the flat graphene sheets and the self-wrapping nanostructures that form, like bilayer edges and nanotubes, have unique electronic properties important for device applications. The biggest obstacle for engineers has been wrestling control of the structure and assembly of these nanostructures to best exploit the properties of carbon. The discoveries of self-assembled novel carbon nanostructures may circumvent the hurdle and lead to new approach of graphene-based electronic devices.

Researchers induced the sublimation of multilayer graphene by Joule-heating, making it thermodynamically favorable for the carbon atoms at the edge of the material to escape into the gas phase, leaving freshly exposed edges on the solid graphene. The remaining graphene edges curl and often welded together to form BLEs. Researchers attribute this behavior to nature’s driving force to reduce capillary energy, dangling bonds on the open edges of monolayer graphene, at the cost of increased bending energy.

“This study demonstrates it is possible to make and integrate curved nanostructures directly on flat graphene, which is extended and electrically conducting,” said Li, associate professor in the Department of Materials Science and Engineering in Penn’s School of Engineering and Applied Science. “Furthermore, it demonstrates that multiple graphene sheets can be intentionally interconnected. And the quality of the plumbing is exceptionally high, better than anything people have used for electrical contacts with carbon nanotubes so far. We are currently investigating the fundamental properties of graphene bi-layer edges, BLE rings and nanotube-BLE junctions.”

 

###

 

The study was performed by Li and Liang Qi of Penn, Jian Yu Huang and Ping Lu of the Center for Integrated Nanotechnologies at Sandia and Feng Ding and Boris I. Yakobson of the Department of Mechanical Engineering and Materials Science at Rice.

It was supported by the National Science Foundation, the Air Force Office of Scientific Research, the Honda Research Institute, the Department of Energy and the Office of Naval Research.

June 2, 2009

Nanotube heatsink

Via KurzweilAI.net — This is just very cool nanotech.

Biomimetic-engineering design can replace spaghetti tangle of nanotubes in novel material
PhysOrg.com, June 1, 2009

An arrangement of carbon nanotubes similar to those found in the cytoskeleton of cells will create a heat sink (effectively dissipating heat), which could prevent a Nanoelectromechanical systems (NEMS)device from failing or melting, scientists in MIT’s Department of Civil and Environmental Engineering have found.

 
Read Original Article>>

April 8, 2009

Nanotubes making Plexi stronger

A nanotech breakthroughwith immediate applications. Carbon nanotubes make PMMA plastic, used in manufacturing shatterproof glass-substitutes, more strong.

From the link:

The plastic, known as PMMA, is most commonly used to make shatterproof glass-substitute materials, such as the brands Plexiglas and Lucite. The researchers reinforced PMMA with both single-walled and multi-walled carbon nanotubes and found that, while both types were effective, the highest was achieved with the multi-walled nanotubes, which resemble several single-walled nanotubes nested together.

Bulk materials reinforced with nanostructures are the future of materials, beginning to replace composites made with micrometer-sized particles. Carbon nanotubes are a natural choice because they are exceptionally strong, and the multi-walled varieties are especially tough because of their more complex structures; they can contain up to 50 nested nanotubes.

A nanotube-enforced PMMA fiber being stretched, forming narrow “necks.” Image courtesty H. Daniel Wagner.

A nanotube-enforced PMMA fiber being stretched, forming narrow “necks.” Image courtesty H. Daniel Wagner.

March 27, 2009

Nanotubes strengthen epoxy composites

Filed under: Science, Technology — Tags: , , , — David Kirkpatrick @ 1:11 am

The lastest in carbon nanotube applications.

The release:

Fitter Frames: Nanotubes Boost Structural Integrity of Composites

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.

New research finding could lead to more durable aircraft, automotive components

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.

This newfound toughness and crack resistance is due to the treated nanotubes, which enhance the molecular mobility of the epoxy at the interface where the two materials touch.  When stressed, this enhanced mobility enables the epoxy to craze – or result in the formation of a network of pillar-like fibers that bridge together both sides of the crack and slow its growth.

“This crazing behavior, and the bridging fibers it produces, dramatically slows the growth rate of a crack,” Koratkar said. “In order for the crack to grow, those fibers have to first stretch, deform plastically, and then break. It takes a lot of energy to stretch and break those fibers, energy that would have otherwise gone toward enlarging the crack.”

Results of the study were published this week in the journal Small.

Epoxy composites infused with carbon nanotubes are known to be more resistant to cracks than pure epoxy composites, as the nanotubes stitch, or bridge, the two sides of the crack together. Infusing an epoxy with carbon nanotubes that have been functionalized, or treated, with the chemical group amidoamine, however, results in a completely different bridging phenomenon.

At the interface of the functionalized nanotubes and the epoxy, the epoxy starts to craze, which is a highly unusual behavior for this particular type of composite, Koratkar said. The epoxy deforms, becomes more fluid, and creates connective fibers up to 10 microns in length and with a diameter between 100 nanometers and 1,000 nanometers.

“We didn’t expect this at all. Crazing is common in certain types of thermoplastic polymers, but very unusual in the type of epoxy composite we used,” Koratkar said. “In addition to improved fatigue resistance and toughness, the treated nanotubes also enhanced the stiffness, hardness, and strength of the epoxy composite, which is very important for structural applications.” 

Koratkar said the aircraft, boat, and automobile industries are increasingly looking to composites as a building material to make vehicle frames and components lighter. His research group plans to further investigate crazing behavior in epoxy composites, in order to better understand why the chemical treatment of nanotubes initiates crazing.

Co-authors of the paper include Rensselaer Associate Professor Catalin Picu, of the Department of Mechanical, Aerospace, and Nuclear Engineering; Rensselaer doctoral students Wei Zhang and Iti Srivastava; and Yue-Feng Zhu, professor in the Department of Mechanical Engineering at Tsinghua University in China.

Visit Koratkar’s Web site for more information on his nanomaterials research.

Published March 26, 2009

March 7, 2009

Nanotech medical imaging breakthrough

More medical nanotechnology news. Better medical imaging (CTs, MRIs, et.al.) means better diagnosis and treatment.

The release:

UConn chemists find secret to increasing luminescence efficiency of carbon nanotubes

Breakthrough procedure has potential applications in medical imaging, homeland security, biological sensors

STORRS, Conn. – Chemists at the University of Connecticut have found a way to greatly increase the luminescence efficiency of single-walled carbon nanotubes, a discovery that could have significant applications in medical imaging and other areas.

Increasing the luminescence efficiency of carbon nanotubes may someday make it possible for doctors to inject patients with microscopic nanotubes to detect tumors, arterial blockages and other internal problems. Rather than relying on potentially harmful x-rays or the use of radioactive dyes, physicians could simply scan patients with an infrared light that would capture a very sharp resolution of the luminescence of the nanotubes in problem areas.

UConn’s process of increasing the luminescence efficiency of single-walled carbon nanotubes will be featured in Science magazine on Friday, March 6, 2009. The research was performed in the Nanomaterials Optoelectronics Laboratory at the Institute of Materials Science at the University of Connecticut, in Storrs, CT. A patent for the process is pending.

University of Connecticut Chemist Fotios Papadimitrakopoulos describes the discovery as a major breakthrough and one of the most significant discoveries in his 10 years of working with single-walled carbon nanotubes. Assisting Papadimitrakopoulos with the research were Polymer Program graduate student Sang-Yong Ju (now a researcher at Cornell University) and William P. Kopcha, a former Chemistry undergraduate assistant in the College of Liberal Arts and Sciences who is now a first-year graduate student at UConn.

Although carbon is used in many diverse applications, scientists have long been stymied by the element’s limited ability to emit light. The best scientists have been able to do with solution-suspended carbon nanotubes was to raise their luminescence efficiency to about one-half of one percent, which is extremely low compared to other materials, such as quantum dots and quantum rods.

By tightly wrapping a chemical ‘sleeve’ around a single-walled carbon nanotube, Papadimitrakopoulos and his research team were able to reduce exterior defects caused by chemically absorbed oxygen molecules.

This process can best be explained by imagining sliding a small tube into a slightly larger diameter tube, Papadimitrakopoulos says. In order for this to happen, all deposits or protrusions on the smaller tube have to be removed before the tube is allowed to slip into the slightly larger diameter tube. What is most fascinating with carbon nanotubes however, Papadimitrakopoulos says, is the fact that in this case the larger tube is not as rigid as the first tube (i.e. carbon nanotube) but is rather formed by a chemical “sleeve” comprised of a synthetic derivative of flavin (an analog of vitamin B2) that adsorbs and self organizes onto a conformal tube.

Papadimitrakopoulos claims that this process of self-assembly is unique in that it not only forms a new structure but also actively “cleans” the surface of the underlying nanotube. It is that active cleaning of the nanotube surface that allows the nanotube to achieve luminescence efficiency to as high as 20 percent.

 

NOTE: To see a QuickTime animation of how a single-walled carbon nanotube is wrapped with the synthetic flavin derivative to increase its luminescence go to: http://www.ims.uconn.edu/~papadim/research.htm

“The nanotube is the smallest tube on earth and we have found a sleeve to put over it,” Papadimitrakopoulos says. “This is the first time that a nanotube was found to emit with as much as 20 percent luminescence efficiency.”

Papadimitrakopoulos has been working closely with the UConn Center for Science and Technology Commercialization (CSTC) in transferring his advances in research into the realm of patents, licenses and corporate partnerships. The CSTC was created several years ago as a way to help expand Connecticut’s innovation-based economy and to help create new businesses and jobs around new ideas.

This is the second major nanotube discovery at UConn by Papadimitrakopoulos in the past two years. Last year, Papadimitrakopoulos and Sang-Young Ju, along with other UConn researchers, patented a way to isolate certain carbon nanotubes from others by seamlessly wrapping a form of vitamin B2 around the nanotubes. It was out of that research that Papadimitrakopoulos and Sang-Yong Ju began wrapping nanotubes with helical assemblies and probing their luminescence properties.

The more luminescent the nanotube, the brighter it appears under infrared irradiation or by electrical excitation (such as that provided by a light-emitting diode or LED). A number of important applications may be possible as a result of this research, Papadimitrakopoulos says. Carbon nanotube emissions are not only extremely sharp, but they also appear in a spectral region where minimal absorption or scattering takes place by soft tissue. Moreover, carbon nanotubes display superb photo bleaching stability and are ideally suited for near-infrared emitters, making them appropriate for applications in medicine and homeland security as bio-reporting agents and nano-sized beacons. Carbon nanotube luminescence also has important applications in nano-scaled LEDs and photo detectors, which can readily integrate with silicon-based technology. This provides an enormous repertoire for nanotube use in advanced fiber optics components, infrared light modulators, and biological sensors, where multiple applications are possible due to the nanotube’s flavin-based (vitamin B2) helical wrapping.

 

###

 

A complete copy of the research article that will appear in Science magazine on Friday, March 6, will be available after 2 p.m. on Thursday, March 5 at: http://www.sciencemag.org/sciencexpress/recent.dtl

More information about the University of Connecticut’s Nanomaterials Optoelectronics Laboratory can be found at: http://chemistry.uconn.edu/papadim/index.htm
Photo available at: http://dropbox.uconn.edu/dropbox?n=Papadim.zip&p=Wwe748VCBRIWDUDwv

March 4, 2009

Nanostitching improves aerospace materials

Nanotech news from MIT.

The release:

MIT: ‘Nanostitching’ could strengthen airplane skins, more

CAMBRIDGE, Mass.–MIT engineers are using carbon nanotubes only billionths of a meter thick to stitch together aerospace materials in work that could make airplane skins and other products some 10 times stronger at a nominal increase in cost.

Moreover, advanced composites reinforced with nanotubes are also more than one million times more electrically conductive than their counterparts without nanotubes, meaning aircraft built with such materials would have greater protection against damage from lightning, said Brian L. Wardle, the Charles Stark Draper Assistant Professor in the Department of Aeronautics and Astronautics.

Wardle is lead author of a theoretical paper on the new nanotube-reinforced composites that will appear in the Journal of Composite Materials (http://jcm.sagepub.com/). He also described the work as keynote speaker at a Society of Plastics Engineers conference this week.

The advanced materials currently used for many aerospace applications are composed of layers, or plies, of carbon fibers that in turn are held together with a polymer glue. But that glue can crack and otherwise result in the carbon-fiber plies coming apart. As a result, engineers have explored a variety of ways to reinforce the interface between the layers by stitching, braiding, weaving or pinning them together.

All of these processes, however, are problematic because the relatively large stitches or pins penetrate and damage the carbon-fiber plies themselves. “And those fiber plies are what make composites so strong,” Wardle said.

So Wardle wondered whether it would make sense to reinforce the plies in advanced composites with nanotubes aligned perpendicular to the carbon-fiber plies. Using computer models of how such a material would fracture, “we convinced ourselves that reinforcing with nanotubes should work far better than all other approaches,” Wardle said. His team went on to develop processing techniques for creating the nanotubes and for incorporating them into existing aerospace composites, work that was published last year in two separate journals.

How does nanostitching work? The polymer glue between two carbon-fiber layers is heated, becoming more liquid-like. Billions of nanotubes positioned perpendicular to each carbon-fiber layer are then sucked up into the glue on both sides of each layer. Because the nanotubes are 1000 times smaller than the carbon fibers, they don’t detrimentally affect the much larger carbon fibers, but instead fill the spaces around them, stitching the layers together.

“So we’re putting the strongest fibers known to humankind [the nanotubes] in the place where the composite is weakest, and where they’re needed most,” Wardle said. He noted that these dramatic improvements can be achieved with nanotubes comprising less than one percent of the mass of the overall composite. In addition, he said, the nanotubes should add only a few percent to the cost of the composite, “while providing substantial improvements in bulk multifunctional properties.”

 

###

 

Wardle’s co-authors on the Journal of Composite Materials paper are Joaquin Blanco, a visiting graduate student in the Department of Aeronautics and Astronautics, Enrique J. Garcia SM ’06, and Roberto Guzman deVilloria, a postdoctoral associate in the department.

This research was sponsored by MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium (necst.mit.edu).

Written by Elizabeth Thomson, MIT News Office

January 6, 2009

Improving nanotube production

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 2:45 pm

From KurzweilAI.net — The cycloparaphenylene “nanohoop” molecule is the shortest segment of a carbon nanotube and may pave the way toward better production methods for longer tubes, offering much greater precision and consistency.

 

A Better Way to Make Nanotubes
PhysOrg.com, Jan. 5, 2009

The newly synthesized cycloparaphenylene “nanohoop” molecule, the shortest segment of a carbonnanotube, could help grow much longer carbon nanotubesin a controlled way and in large batches, with each nanotube identical to the next.

This combination of precision and high yield will be needed if carbon nanotubes are to make the jump from the lab to the commercial sector. To replace silicon wafers in electronics, for example, they’ll need to be just as unblemished as silicon wafers, and just as easy to make in large numbers.

 
Read Original Article>>

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