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A recipe for controlling carbon nanotubes
September 21, 2009Case Western Reserve University researchers find mixing different metals in a catalyst can help determine structure, function
CLEVELAND - Nanoscopic tubes made of a lattice of carbon just a single atom deep hold promise for delivering medicines directly to a tumor, sensors so keen they detect the arrival or departure of a single electron, a replacement for costly platinum in fuel cells or as energy‐saving transistors and wires.
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 carbon nanotube describes how a lattice of carbon atoms 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."
Better to make what you want.
Chiang and Sankaran found that a mixed iron and nickel catalyst could change the outcome. Of the compositions tested, a catalyst of 27 percent nickel and 73 percent iron produced the most dramatic result: the vast majority of the nanotubes were semiconducting. They are now working on assessing the purity and integrating the nanotubes into thin film transistors.
The authors say their findings open the door to experimenting with other elements as catalysts and different combinations, which may produce near‐pure nanotubes with desired properties.
Case Western Reserve University
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 carbon nanotube describes how a lattice of carbon atoms 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."
Better to make what you want.
Chiang and Sankaran found that a mixed iron and nickel catalyst could change the outcome. Of the compositions tested, a catalyst of 27 percent nickel and 73 percent iron produced the most dramatic result: the vast majority of the nanotubes were semiconducting. They are now working on assessing the purity and integrating the nanotubes into thin film transistors.
The authors say their findings open the door to experimenting with other elements as catalysts and different combinations, which may produce near‐pure nanotubes with desired properties.
Case Western Reserve University
Carbon Nanotubes Current Events and Carbon Nanotubes News RSSCaltech scientists develop DNA origami nanoscale breadboards for carbon nanotube circuits
In work that someday may lead to the development of novel types of nanoscale electronic devices, an interdisciplinary team of researchers at the California Institute of Technology (Caltech) has combined DNA's talent for self-assembly with the remarkable electronic properties of carbon nanotubes, thereby suggesting a solution to the long-standing problem of organizing carbon nanotubes into nanoscale electronic circuits.
Breakthrough in industrial-scale nanotube processing
Rice University scientists today unveiled a method for the industrial-scale processing of pure carbon-nanotube fibers that could lead to revolutionary advances in materials science, power distribution and nanoelectronics.
Next-generation microcapsules deliver 'chemicals on demand'
Scientists in California are reporting development of a new generation of the microcapsules used in carbon-free copy paper, in which capsules burst and release ink with pressure from a pen.
Study shows how carbon nanotubes can affect lining of the lungs
Carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems.
Advance in 'nano-agriculture': Tiny stuff has huge effect on plant growth
With potential adverse health and environmental effects often in the news about nanotechnology, scientists in Arkansas are reporting that carbon nanotubes (CNTs) could have beneficial effects in agriculture.
Friction force differences could offer a new means for sorting and assembling nanotubes
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New biosensor can detect bacteria instantaneously
A research group from the Rovira i Virgili University (URV) in Tarragona has developed a biosensor that can immediately detect very low levels of Salmonella typhi, the bacteria that causes typhoid fever.
Researchers design new graphene-based, nano-material with magnetic properties
An international team of researchers has designed a new graphite-based, magnetic nano-material that acts as a semiconductor and could help material scientists create the next generation of electronic devices like microchips.
Researchers Pinpoint Neural Nanoblockers in Carbon Nanotubes
A team of Brown University scientists has pinpointed why carbon nanotubes tend to block a critical signaling pathway in neurons.
Pitt researchers harness carbon nanomaterials for drug delivery systems, oxygen sensors
Two nanoscale devices recently reported by University of Pittsburgh researchers in two separate journals harness the potential of carbon nanomaterials to enhance technologies for drug or imaging agent delivery and energy storage systems, in one case, and, in the other, bolster the sensitivity of oxygen sensors essential in confined settings, from mines to spacecrafts.
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