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Showing Spotlights 97 - 104 of 118 in category Graphene (newest first):

 

Bottom-up fabrication of carbon nanosystems by trapping single metal atoms

graphene_sheetAmong the various production methods for carbon nanotubes and graphene, currently only chemical vapor deposition techniques demonstrate a significant opportunity for mass production of CNT material. Using the CVD process, which is based on the catalytic action of metals, manufacturers can combine a metal catalyst such as iron with reaction gases such as hydrogen to form carbon nanotubes inside a high-temperature furnace. In order to optimize the synthesis process, a detailed understanding of the interaction between nanotubes or graphene and metal atoms is required - something that has been missing so far. Researchers in France have now shown that it is possible to create atomic-scale defects in carbon nanotubes and in graphene in preselected positions with a focused electron beam and to use these defects as trapping centers for foreign atoms.

Posted: May 31st, 2010

New findings about the activity of graphene oxide sheets at interfaces

graphene_oxideGraphite oxide sheet, now being named graphene oxide - a compound of carbon, oxygen, and hydrogen obtained by treating graphite with strong oxidizers - has attracted substantial interest as a possible intermediate for the manufacture of graphene. It has been largely viewed as hydrophilic - having a strong affinity for water illustrated by its excellent colloidal stability in water. In what should help to better understand and improve the solution processing of graphite oxide-based graphene materials and open up opportunities to design new functional graphite oxide-based hybrid materials, researchers have now reported that graphite oxide is amphiphilic - possessing both hydrophilic and lipophilic (fat-liking) properties - and can adsorb onto air-water, oil-water and solid-water interfaces.

Posted: May 26th, 2010

Flexible nano-power with fully transparent and rollable graphene nanogenerators

nanogeneratorAs it is becoming clearer that one of the critical issues for developing functional nanomachines is the generation of energy required to power them, research into developing nanoscale energy sources has been picking up substantially. The energy to be fed into a nanogenerator is likely to be mechanical energy that is converted into electric energy that then will be used to power nanodevices without using a battery. With the emergence of nanotechnology and the use of nanomaterials, the field of piezoelectrics and nanopiezotronics has experienced a lot of new and interesting research efforts. Researchers in Korea have now demonstrated the first use of chemical vapor deposition-grown large-scale graphene sheets as transparent electrodes for fully transparent and flexible nanogenerators.

Posted: Apr 19th, 2010

Graphene photodetectors for high-speed optical communications

grapheneSilicon has dominated solid-state electronics for more than four decades but now a variety of other materials are being explored in photonic devices to expand the wavelength range of operation and to improve performance. Graphene is such a material - although most research on graphene so far has focused mainly on electronics. IBM researchers have now shown that graphene-based devices can be used in optical communications. Introducing this new material system into photonics could have a significant impact on mainstream optical applications. By using graphene, researchers make use of the internal electric field that exists at the interface of graphene and metal. Through a sophisticated combination of palladium and titanium electrodes they created a photodetector that does not rely on external current.

Posted: Apr 7th, 2010

Multifunctional graphene mats for sensor and catalyst applications

nanoparticles_on_grapheneCarbon-supported catalysts are widely used in many applications. For example, platinum nanoparticles supported on bulk carbon frameworks are used as fuel cell electrodes. The obvious challenge is to have a large area of carbon surface so that the catalyst particles can be dispersed without any aggregation. Graphene with its 2D nanostructure provides a large surface area (theoretically, the surface area of graphene is about 2600 square meters per gram) to anchor catalyst particles. Scientists have now succeeded in dispersing two different types of nanoparticles - silver and titanium dioxide - on a reduced graphene oxide at different sites without any aggregation.

Posted: Jan 21st, 2010

The rise of graphene in ultra-fast photonics

graphene_absorberA group of researchers from Singapore, led by Professor Dingyuan Tang from Nanyang Technological University and Professor Kian Ping Loh from National University of Singapore, have reported the first breakthrough in using few-layer graphene as a saturable absorber for the mode locking of lasers. Despite its prominent mechanical and electrical properties, graphene's optical response has previously been considered to be weak and featureless, so the main interests of the research community are centered on its electronics properties. But now, Tang and Loh demonstrate that graphene can be used for telecommunications applications and that its weak and universal optical response might be turned into advantages for ultrafast photonics applications.

Posted: Jan 6th, 2010

New imaging technique allows quick evaluation of graphene sheets

grapheneGraphene based sheets such as pristine graphene, graphene oxide, or reduced graphene oxide are basically single atomic layers of carbon network. They are the world's thinnest materials. A general visualization method that allows quick observation of these sheets would be highly desirable as it can greatly facilitate sample evaluation and manipulation, and provide immediate feedback to improve synthesis and processing strategies. Current imaging techniques for observing graphene based sheets include atomic force microscopy, transmission electron microscopy, scanning electron microscopy and optical microscopy. Some of these techniques are rather low-throughput. And all the current techniques require the use of special types of substrates. This greatly limits the capability to study these materials. Researchers from Northwestern University have now reported a new method, namely fluorescence quenching microscopy, for visualizing graphene-based sheets.

Posted: Dec 14th, 2009

Graphene nanotechnology for tomorrow's nanoelectronic circuits

grapheneChip structures already have reached nanoscale dimensions but as they continue to shrink below the 20 nanometer mark, ever more complex challenges arise and scaling appears not to be economically feasible any more. And below 10 nm, the fundamental physical limits of CMOS technology will be reached. One promising material that could enable the chip industry to move beyond the current CMOS technology is graphene, a monolayer sheet of carbon. Notwithstanding the intense research interest, large scale production of single layer graphene remains a significant challenge. Researchers at Cornell University have now reported a new technique for producing large scale single layer graphene sheets and fabricating transistor arrays with uniform electrical properties directly on the device substrate.

Posted: Dec 2nd, 2009