Carbon Nanotube – Molecular Stucture

Rotating Carbon Nanotube

PhysOrg.com, April 12, 2010  –  An international study based at the University of Pittsburgh provides the first identification of a human enzyme that can biodegrade carbon nanotubes—the superstrong materials found in products from electronics to plastics—and in laboratory tests offset the potentially damaging health effects of being exposed to the tiny components, according to findings published online in Nature Nanotechnology.

The results could open the door to the use of carbon nanotubes as a safe drug-delivery tool and also could lead to the development of a natural treatment for people exposed to nanotubes, either in the environment or the workplace, the team reported. The researchers found that carbon nanotubes degraded with the human enzyme myeloperoxidase (hMPO) did not produce the lung inflammation that intact nanotubes have been shown to cause. Furthermore, neutrophils, the white blood cells that contain and emit hMPO to kill invading microorganisms, can be directed to attack carbon nanotubes specifically.

“The successful medical application of carbon nanotubes rely on their effective breakdown in the body, but carbon nanotubes also are notoriously durable,” said lead researcher Valerian Kagan, a professor and vice chair in the Department of Environmental and Occupational Health in Pitt’s Graduate School of Public Health. “The ability of hMPO to biodegrade carbon nanotubes reveals that this breakdown is part of a natural inflammatory response. The next step is to develop methods for stimulating that inflammatory response and reproducing the biodegradation process inside a living organism.”

Kagan and his research group led the team of more than 20 researchers from four universities along with the laboratory groups of Alexander Star, an assistant professor of chemistry in Pitt’s School of Arts and Sciences, and Judith Klein-Seethharaman, an assistant professor of structural biology in Pitt’s School of Medicine. Additional Pitt researchers included Yulia Tyurina, a Pitt assistant professor of environmental and occupational health in the Graduate School of Public Health, and Donna Stolz, an associate professor of cell biology and physiology in Pitt’s medical school; other researchers are from Sweden’s Karolinska Institute, Trinity College in Ireland, the National Institute for Occupational Safety and Health, and West Virginia University.

 

Test tube with a solution of carbon nanotubes, which were sorted by diameter using density-gradient ultracentrifugation.

Carbon nanotubes are one-atom thick rolls of graphite 100,000 times smaller than a human hair yet stronger than steel. They are used to reinforce plastics, ceramics, or concrete; are excellent conductors of electricity and heat; and are sensitive chemical sensors. However, a nanotube’s surface also contains thousands of atoms that could react with the human body in unknown ways. Tests on mice have shown that nanotube inhalation results in severe lung inflammation coupled with an early onset of fibrosis. The tubes’ durability raises additional concern about proper disposal and cleanup. In 2008, Star and Kagan reported in Nano Letters that carbon nanotubes deteriorate when exposed to the plant enzyme horseradish peroxidase, but their research focused on cleanup after accidental spills during manufacturing or in the environment.

For the current study, the researchers focused on human MPO because it works via the release of strong acids and oxidants—similar to the chemicals used to break down carbon nanotubes. They first incubated short, single-walled nanotubes in an hMPO and hydrogen peroxide solution—the hydrogen peroxide sparks and sustains hMPO activity—for 24 hours, after which the structure and bulk of the tube had completely degenerated. The nanotubes degenerated even faster when sodium chloride was added to the solution to produce hypochlorite, a strong oxidizing compound known to break down nanotubes.

After establishing the effectiveness of hMPO in degrading carbon nanotubes, the team developed a technique to prompt neutrophils to attack nanotubes by capturing them and exposing them to the enzyme. They implanted a sample of nanotubes with antibodies known as immunoglobulin G (IgG), which made them specific neutrophil targets. After 12 hours, 100 percent of IgG nanotubes were degraded versus 30 percent of those without IgG. The researchers also tested the ability of macrophages, another white blood cell, to break down nanotubes, but after two days, only 50 percent of the tubes had degenerated.

In subsequent laboratory tests, lung tissue exposed to the degraded nanotubes for seven days exhibited negligible change when compared to unexposed tissue. On the other hand, tissue exposed to untreated nanotubes developed severe inflammation.   Provided by University of Pittsburgh

Types of carbon nanotubes and related structures

Single-walled

Researchers report a major boost in energy-harvesting devices

MIT Technology Review, April 12, 2010, by Katherine Bourzac  –  This Tuesday at the Materials Research Society spring meeting in San Francisco I sat down with Zhong Lin Wang, director of the center for nanostructure characterization at Georgia Tech. We featured Wang’s work on self-powered nanosensors in our “10 Emerging Technologies” issue last year. The payoff from this concept would be huge: nanoscale sensors are exquisitely sensitive, very frugal with power, and, of course, tiny. They could be useful for detecting molecular signs of disease in the blood, minute amounts of poisonous gases in the air, and trace contaminants in food. Eliminating the batteries needed to drive these devices would make it possible to fully miniaturize them.

Wang has been developing devices based on nanowires that exhibit piezoelectricity. That is, they generate a voltage when they’re bent. He has been integrating these nanowires into devices that can harvest energy from biomechanical motion–including the running movements of a hamster on a wheel or the tapping of a finger–and use it to power a small sensor.

The problem with these devices has been getting a significant voltage out of them. This Tuesday morning, Wang presented recent data showing he has boosted the voltage produced by his nanowire devices by two orders of magnitude. The new design integrates millions of piezoelectric zinc-oxide nanowires in layered arrays on a plastic backing. Wang has coupled these devices with pH and UV-light sensors and demonstrated that they can power the sensor to take a measurement when stressed. Earlier this month, in the journal Nature, Wang reported a flexible device that produces 1.2 volts when it’s stressed; he says he has now made devices that produce 2.4 volts. This is enough to start thinking about integrating a charge-storage device that will make it possible to regulate the voltage going into the sensors for better control of measurements. Indeed, Wang says, that’s his next step.

Wang says he proposed the idea of self-powered nanotechnology based on these energy-harvesting devices in 2006, and at the time, there were many skeptics. Now others have started to replicate his results and other groups in academia and even at Samsung are starting their own research in the area.

SEM images showing the nanowire arrays in the T-shirt fabric, and diagram illustrating the cross-section of the carbon microfibre coated with boron carbide-nanowires. Image (c) Advanced Materials

April 7, 2010

Carbon Nanotube

PhysOrg.com, April 12, 2010 — A simple cotton T-shirt may one day be converted into tougher, more comfortable body armor for soldiers or police officers.

Researchers at the University of South Carolina, collaborating with others from China and Switzerland, drastically increased the toughness of a T-shirt by combining the carbon in the shirt’s cotton with boron – the third hardest material on earth. The result is a lightweight shirt reinforced with boron carbide, the same material used to protect tanks.

Dr. Xiaodong Li, USC College of Engineering and Computing Distinguished Professor in Mechanical Engineering, co-authored the recent article on the research in the journal, Advanced Materials.

“USC is playing a leading role in this area. This is a true breakthrough,” Li said, calling the research “a conceptual change in fabricating lightweight, fuel-efficient, super-strong and ultra-tough materials. This groundbreaking new study opens up unprecedented opportunities.”

The scientists started with plain, white T-shirts that were cut into thin strips and dipped into a boron solution. The strips were later removed from the solution and heated in an oven. The heat changes the cotton fibers into carbon fibers, which react with the boron solution and produce boron carbide.

The result is a fabric that’s lightweight but tougher and stiffer than the original T-shirt, yet flexible enough that it can be bent, said Li, who led the group from USC. That flexibility is an improvement over the heavy boron-carbide plates used in bulletproof vests and body armor.

“The currently used boron-carbide bulk material is brittle,” Li said. “The boron-carbide nanowires we synthesized keep the same strength and stiffness of the bulk boron carbide but have super-elasticity. They are not only lightweight but also flexible. We should be able to fabricate much tougher body armors using this new technique. It could even be used to produce lightweight, fuel-efficient cars and aircrafts.”

The resulting boron-carbide fabric can also block almost all ultraviolet rays, Li said.

Provided by University of South Carolina

Types of Carbon Nanotubes

This formerly was a featured picture on the English language Wikipedia (Featured pictures) and was considered one of the finest images

Aligned nanotubes are preferred for many applications.

An electronic device known as a diode can be formed by joining two nanoscale carbon tubes with different electronic properties.  This image is a work of a United States Department of Energy (or predecessor organization) employee, taken or made during the course of an employee’s official duties. As a work of the U.S. federal government, the image is in the public domain.

Carbon Nanotubes

Model of a bucky ball (fulleren) and carbon nanotubes