Graphene and Carbon Nanotubes: Two Great Materials Even Better Together


James Tour at Rice University has a history of finding links between carbon nanotubes and graphene, which are often regarded merely as rivals for a host of electronic applications .

A few years back, Tour developed a process for “unzipping” carbon nanotubes so that they transformed into graphene.

Now Tour and his colleagues have used that unzipping technique to develop a method in which carbon nanotubes are used as a kind of reinforcing rebar for graphene , protecting it during the manufacturing process.

Because to produce  high-quality graphene  for electronic applications (a promising one is  replacing indium tin oxide as a transparent conductor in displays for controlling pixels), a manufacturing process known as chemical vapor deposition (CVD) is used, and CVD has an Achilles heel: while it is possible to grow large sheets of graphene on a copper substrate in a furnace, when you try to remove the graphene sheets from the copper, you find that it is difficult to do so without breaking the graphene.

A reinforcement polymer is usually laid over the graphene to keep it from breaking during its removal, but this polymer leaves impurities.


http://spectrum.ieee.org/nanoclast/semiconductors/materials/graphene-and-carbon-nanotubes-two-great-materials-even-better-together

Nanotech roundup: turning seawater into drinking water, and body power

This month's roundup includes the promise of a filter that extracts salt from seawater, and a battery powered by the heart



Graphene, the sheet of carbon just one atom thick, has already featured a few times on this blog thanks to its unique promise for many applications.

The researchers will try out ways to prevent the swelling, so that the nanochannels are so small that they block small ions while water still flows through quickly: a perfect filter for removing salt from water.

Graphene, which has ultra-efficient electronic properties, seems an ideal candidate for transistors in fast, wireless circuits, which convert radio-frequency signals into electrical currents.

Now researchers from Wuhan, China, have used nanoparticles to reveal the merest smudge of a print, even on difficult surfaces such as plastic and coins.


http://www.theguardian.com/p/3n7xt/tw

RV: Butterfly inspires new nanotechnology

 

 

Fuente: Swinburne Media Centre - Latest News
Expuesto el: lunes, 02 de septiembre de 2013 1:00
Autor: Swinburne Media Centre - Latest News
Asunto: Butterfly inspires new nanotechnology

 

By mimicking microscopic structures in the wings of a butterfly, an international research team has developed a device smaller than the width of a human hair that could make optical communication faster and more secure. The researchers, from Swinburne University of Technology in Australia and Friedrich-Alexander Universität Erlangen-Nürnberg in Germany, have produced a photonic crystal that can split both left and right circularly polarised light. The design for this crystal was inspired by the Callophrys Rubi butterfly, also known as the Green Hairstreak. This butterfly has 3D nano-structures within its wings which give them their vibrant green colour. Other insects also have nano-structures that provide colour, but the Callophrys Rubi has one important difference. "This butterfly's wing contains an immense array of interconnected nano-scale coiled springs that form a unique optical material. We used this concept to develop our photonic crystal device," Swinburne PhD graduate, Dr Mark Turner, said. Using 3D laser nano-technology, the Swinburne researchers built a photonic crystal with properties that don't exist in naturally occurring crystals, specifically one that works with circular polarisation. This miniature device contains over 750,000 tiny polymer nano-rods. The photonic crystal acts as a miniature polarising beamsplitter, similar to a device invented by Scottish scientist William Nicol in 1828. Polarising beamsplitters used in modern technology - such as telecommunications, microscopy and multimedia - are built from naturally occurring crystals, which work for linearly polarised light but not circularly polarised light. "We believe we have created the first nano-scale photonic crystal chiral beamsplitter," Director of the Centre for Micro-Photonics at Swinburne, Professor Min Gu, said. "It has the potential to become a useful component for developing integrated photonic circuits that play an important role in optical communications, imaging, computing and sensing. "The technology offers new possibilities for steering light in nano-photonic devices and takes us a step closer towards developing optical chips that could overcome the bandwidth bottleneck for ultra-high speed optical networks." The research has been published in the journal Nature Photonics. The researchers involved were Mark Turner, Qiming Zhang, Benjamin Cumming and Min Gu (Swinburne University of Technology) and Matthias Saba and Gerd E Schröder-Turk (Friedrich-Alexander Universität Erlangen-Nürnberg). Dr Turner is now working in California's Silicon Valley to develop and commercialise new photonic technologies for real world applications. This project is part of the Centre for Excellence for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), funded by the Australian Research Council under the Centres of Excellence Program, with further support from seven constituent universities, and fifteen partner investigators. Dr Turner's PhD project was also partly supported by the Australian Cooperative Research Centre for Polymers. Lea Kivivali lkivivali@swin.edu.au Department: Corporate and Government Affairs Phone: +61 3 9214 5428 Mobile Phone: 0410 569 311

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RV: The potential risks of nanomaterials: a review carried out for ECETOC

 

 

Fuente: Edinburgh Research Explorer RSS
Expuesto el: lunes, 29 de julio de 2013 16:44
Autor: Edinburgh Research Explorer RSS
Asunto: The potential risks of nanomaterials: a review carried out for ECETOC

 

Paul Ja Borm David Robbins Stephan Haubold Thomas Kuhlbusch Heinz Fissan Ken Donaldson Roel Schins Vicki Stone Wolfgang Kreyling Jurgen Lademann Jean Krutmann David Warheit Eva Oberdorster School of Clinical Sciences ·         Download as Adobe PDF Rights statement: © 2006 Borm et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Publisher final version (usually the publisher pdf) , Text, 972 KB, PDF-document 29/07/13 http://www.particleandfibretoxicology.com/content/3/1/11 Original language English Pages 11 Journal Particle and fibre toxicology Journal publication date 1 Jan 2006 Journal number 1 Volume 3 DOIs http://dx.doi.org/10.1186/1743-8977-3-11 State Published During the last few years, research on toxicologically relevant properties of engineered nanoparticles has increased tremendously. A number of international research projects and additional activities are ongoing in the EU and the US, nourishing the expectation that more relevant technical and toxicological data will be published. Their widespread use allows for potential exposure to engineered nanoparticles during the whole lifecycle of a variety of products. When looking at possible exposure routes for manufactured Nanoparticles, inhalation, dermal and oral exposure are the most obvious, depending on the type of product in which Nanoparticles are used. This review shows that (1) Nanoparticles can deposit in the respiratory tract after inhalation. For a number of nanoparticles, oxidative stress-related inflammatory reactions have been observed. Tumour-related effects have only been observed in rats, and might be related to overload conditions. There are also a few reports that indicate uptake of nanoparticles in the brain via the olfactory epithelium. Nanoparticle translocation into the systemic circulation may occur after inhalation but conflicting evidence is present on the extent of translocation. These findings urge the need for additional studies to further elucidate these findings and to characterize the physiological impact. (2) There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure. However, the question has been raised whether the usual testing with healthy, intact skin will be sufficient. (3) Uptake of nanoparticles in the gastrointestinal tract after oral uptake is a known phenomenon, of which use is intentionally made in the design of food and pharmacological components. Finally, this review indicates that only few specific nanoparticles have been investigated in a limited number of test systems and extrapolation of this data to other materials is not possible. Air pollution studies have generated indirect evidence for the role of combustion derived nanoparticles (CDNP) in driving adverse health effects in susceptible groups. Experimental studies with some bulk nanoparticles (carbon black, titanium dioxide, iron oxides) that have been used for decades suggest various adverse effects. However, engineered nanomaterials with new chemical and physical properties are being produced constantly and the toxicity of these is unknown. Therefore, despite the existing database on nanoparticles, no blanket statements about human toxicity can be given at this time. In addition, limited ecotoxicological data for nanomaterials precludes a systematic assessment of the impact of Nanoparticles on ecosystems. ID: 8543360

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RV: To make tiny graphene ribbons, simply add water

 

 

Fuente: Futurity.org
Expuesto el: miércoles, 31 de julio de 2013 14:42
Autor: Mike Williams-Rice
Asunto: To make tiny graphene ribbons, simply add water

 

Chemist James Tour says any method to form long wires only a few nanometers wide should catch the interest of microelectronics manufacturers as they approach the limits of their ability to miniaturize circuitry. (Credit: Jason Bolonski/Flickr) RICE (US) — Forming long graphene nanoribbons less than 10 nanometers wide is possible—if water is added into the mix. Researchers discovered that a bit of water adsorbed from the atmosphere was found to act as a mask in a process that begins with the creation of patterns via lithography and ends with very long, very thin graphene nanoribbons. The ribbons form wherever water gathers at the wedge between the raised pattern and the graphene surface. The team describes the method in a study published in the journal ACS Nano. A fine line of conductive graphene sits atop a boron nitride substrate in this electron microscope image. (Credit: Tour Group/Rice University) Straight from the Source Read the original study DOI: 10.1021/nn403057t The water formation is called a meniscus; it is created when the surface tension of a liquid causes it to curve. In the process, the meniscus mask protects a tiny ribbon of graphene from being etched away when the pattern is removed. Rice University chemist James Tour says any method to form long wires only a few nanometers wide should catch the interest of microelectronics manufacturers as they approach the limits of their ability to miniaturize circuitry. "They can never take advantage of the smallest nanoscale devices if they can't address them with a nanoscale wire," he says. "Right now, manufacturers can make small features, or make big features and put them where they want them. But to have both has been difficult. "To be able to pattern a line this thin right where you want it is a big deal because it permits you to take advantage of the smallness in size of nanoscale devices." Water is key to success Tour says water's tendency to adhere to surfaces is often annoying, but in this case it's essential to the process. "There are big machines that are used in electronics research that are often heated to hundreds of degrees under ultrahigh vacuum to drive off all the water that adheres to the inside surfaces," he explains. "Otherwise there's always going to be a layer of water. "In our experiments, water accumulates at the edge of the structure and protects the graphene from the reactive ion etching (RIE). So in our case, that residual water is the key to success. "Nobody's ever thought of this before, and it's nothing we thought of," Tour says. "This was fortuitous." Lead study author Vera Abramova and co-author Alexander Slesarev, both graduate students in Tour's lab, had set out to fabricate nanoribbons by inverting a method developed by another Rice lab to make narrow gaps in materials. The original method utilized the ability of some metals to form a native oxide layer that expands and shields material just on the edge of the metal mask. The new method worked, but not as expected. "We first suspected there was some kind of shadowing," Abramova says. But other metals that didn't expand as much, if at all, showed no difference, nor did varying the depth of the pattern. "I was basically looking for anything that would change something." No special tools required It took two years to develop and test the meniscus theory, during which the researchers also confirmed its potential to create sub-10-nanometer wires from other kinds of materials, including platinum. They also constructed field-effect transistors to check the electronic properties of graphene nanoribbons. To be sure that water does indeed account for the ribbons, they tried eliminating its effect by first drying the patterns by heating them under vacuum, and then by displacing the water with acetone to eliminate the meniscus. In both cases, no graphene nanoribbons were created. The researchers are working to better control the nanoribbons' width, and they hope to refine the nanoribbons' edges, which help dictate their electronic properties. "With this study, we figured out you don't need expensive tools to get these narrow features," Tour says. "You can use the standard tools a fab line already has to make features that are smaller than 10 nanometers." The Air Force Office of Scientific Research and the Office of Naval Research Multidisciplinary University Research Initiative Graphene Program supported the research. Source: Rice University

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RV: York Nanocentre researchers image individual atoms in a living catalytic reaction

 

 

Fuente: University of York - Latest news
Expuesto el: viernes, 12 de julio de 2013 12:52
Autor: University of York - Latest news
Asunto: York Nanocentre researchers image individual atoms in a living catalytic reaction

 

Groundbreaking new electron microscopy technology developed at the York JEOL Nanocentre at the University of York is allowing researchers to observe and analyse single atoms, small clusters and nanoparticles in dynamic in-situ experiments for the first time.

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RV: Sound waves precisely position nanowires

Fuente: Penn State News - Research
Expuesto el: domingo, 23 de junio de 2013 5:52
Autor: Penn State News - Research
Asunto: Sound waves precisely position nanowires

 

UNIVERSITY PARK, Pa. -- The smaller components become, the more difficult it is to create patterns in an economical and reproducible way, according to an interdisciplinary team of Penn State researchers who, using sound waves, can place nanowires in repeatable patterns for potential use in a variety of sensors, optoelectronics and nanoscale circuits. "There are ways to create these devices with lithography, but it is very hard to create patterns below 50 nanometers using lithography," said Tony Jun Huang, associate professor of engineering science and mechanics, Penn State. "It is rather simple now to make metal nanomaterials using synthetic chemistry. Our process allows pattern transfer of arrays of these nanomaterials onto substrates that might not be compatible with conventional lithography. For example, we could make networks of wires and then pattern them to arrays of living cells." The researchers looked at the placement of metallic nanowires in solution on a piezoelectric substrate. Piezoelectric materials move when an electric voltage is applied to them and create an electric voltage when compressed. In this case, the researchers applied an alternating current to the substrate so that the material's movement creates a standing surface acoustic wave in the solution. A standing wave has node locations that do not move, so the nanowires arrive at these nodes and remain there. If the researchers apply only one current, then the nanowires form a one-dimensional array with the nanowires lined up head to tail in parallel rows. If perpendicular currents are used, a two-dimensional grid of standing waves forms and the nanowires move to those grid-point nodes and form a three-dimensional spark-like pattern. "Because the pitch of both the one-dimensional and two-dimensional structures is sensitive to the frequency of the standing surface acoustic wave field, this technique allows for the patterning of nanowires with tunable spacing and density," the researchers report in a recent issue of ACS Nano. The nanowires in solution will settle in place onto the substrate when the solution evaporates, preserving the pattern. The researchers note that the patterned nanowires could then be transferred to organic polymer substrates with good accuracy by placing the polymer onto the top of the nanowires and with slight pressure, transferring the nanowires. They suggest that the nanowires could then be transferred to rigid or flexible substrates from the organic polymer using microcontact-printing techniques that are well developed. "We really think our technique can be extremely powerful," said Huang. "We can tune the pattern to the configuration we want and then transfer the nanowires using a polymer stamp." The spacing of the nodes where nanowires deposit can be adjusted on the fly by changing the frequency and the interaction between the two electric fields. "This would save a lot of time compared to lithography or other static fabrication methods," said Huang. The researchers are currently investigating more complex designs. Other researchers working on this project include Yuchao Chen, Xiaoyun Ding, Sz-Chin Steven Lin, Po-Hsun Huang, Nitesh Nama, Yanhui Zhao, Ahmad Ahsan Nawaz and Feng Guo, all graduate students in engineering science and mechanics; Shikuan Yang, postdoctoral researcher in engineering science and mechanics; Yeyi Gu, graduate student in food science; and Thomas E. Mallouk, Evan Pugh Professor of Chemistry, and Wei Wang, graduate student in chemistry. The National Institutes of Health, National Science Foundation and the Penn State Center for Nanoscale Science supported this research.

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