Navigation Links
Material world: Graphene's versatility promises new applications
Date:7/9/2009

Since its discovery just a few years ago, graphene has climbed to the top of the heap of new super-materials poised to transform the electronics and nanotechnology landscape. As N.J. Tao, a researcher at the Biodesign Institute of Arizona State University explains, this two dimensional honeycomb structure of carbon atoms is exceptionally strong and versatile. Its unusual properties make it ideal for applications that are pushing the existing limits of microchips, chemical sensing instruments, biosensors, ultracapacitance devices, flexible displays and other innovations.

In the latest issue of Nature Nanotechnology Letters, Tao describes the first direct measurement of a fundamental property of graphene, known as quantum capacitance, using an electrochemical gate method. A better understanding of this crucial variable should prove invaluable to other investigators participating in what amounts to a gold rush of graphene research.

Although theoretical work on single atomic layer graphene-like structures has been going on for decades, the discovery of real graphene came as a shock. "When they found it was a stable material at room temperature," Tao says, "everyone was surprised." As it happens, minute traces of graphene are shed whenever a pencil line is drawn, though producing a 2-D sheet of the material has proven trickier. Graphene is remarkable in terms of thinness and resiliency. A one-atom thick graphene sheet sufficient in size to cover a football field, would weigh less than a gram. It is also the strongest material in natureroughly 200 times the strength of steel. Most of the excitement however, has to do with the unusual electronic properties of the material.

Graphene displays outstanding electron transport, permitting electricity to flow rapidly and more or less unimpeded through the material. In fact, electrons have been shown to behave as massless particles similar to photons, zipping across a graphene layer without scattering. This property is critical for many device applications and has prompted speculation that graphene could eventually supplant silicon as the substance of choice for computer chips, offering the prospect of ultrafast computers operating at terahertz speeds, rocketing past current gigahertz chip technology. Yet, despite encouraging progress, a thorough understanding of graphene's electronic properties has remained elusive. Tao stresses that quantum capacitance measurements are an essential part of this understanding.

Capacitance is a material's ability to store energy. In classical physics, capacitance is limited by the repulsion of like electrical charges, for example, electrons. The more charge you put into a device, the more energy you have to expend to contain it, in order to overcome charge repulsion. However, another kind of capacitance exists, and dominates overall capacitance in a two-dimensional material like graphene. This quantum capacitance is the result of the Pauli exclusion principle, which states that two fermionsa class of common particles including protons, neutrons and electronscannot occupy the same location at the same time. Once a quantum state is filled, subsequent fermions are forced to occupy successively higher energy states. As Tao explains, "it's just like in a building, where people are forced to go to the second floor once the first level is occupied."

In the current study, two electrodes were attached to graphene, and a voltage applied across the material's two-dimensional surface by means of a third, gate electrode. Plots of voltage vs. capacitance can be seen in fig1. In Tao's experiments, graphene's ability to store charge according to the laws of quantum capacitance, were subjected to detailed measurement. The results show that graphene's capacitance is very small. Further, the quantum capacitance of graphene did not precisely duplicate theoretical predictions for the behavior of ideal graphene. This is due to the fact that charged impurities occur in experimental samples of graphene, which alter the behavior relative to what is expected according to theory.

Tao stresses the importance of these charged impurities and what they may mean for the development of graphene devices. Such impurities were already known to affect electron mobility in graphene, though their effect on quantum capacitance has only now been revealed. Low capacitance is particularly desirable for chemical sensing devices and biosensors as it produces a lower signal-to-noise ratio, providing for extremely fine-tuned resolution of chemical or biological agents. Improvements to graphene will allow its electrical behavior to more closely approximate theory. This can be accomplished by adding counter ions to balance the charges resulting from impurities, thereby further lowering capacitance.

The sensitivity of graphene's single atomic layer geometry and low capacitance promise a significant boost for biosensor applications. Such applications are a central topic of interest for Tao, who directs the Biodesign Institute's Center for Bioelectronics and Biosensors. As Tao explains, any biological substance that interacts with graphene's single atom surface layer can be detected, causing a huge change in the properties of the electrons.

One possible biosensor application under consideration would involve functionalizing graphene's surface with antibodies, in order to precisely study their interaction with specific antigens. Such graphene-based biosensors could detect individual binding events, given a suitable sample. For other applications, adding impurities to graphene could raise overall interfacial capacitance. Ultracapacitors made of graphene composites would be capable of storing much larger amounts of renewable energy from solar, wind or wave energy than current technologies permit.

Because of graphene's planar geometry, it may be more compatible with conventional electronic devices than other materials, including the much-vaunted carbon nanotubes. "You can imagine an atomic sheet, cut into different shapes to create different device properties," Tao says.

Since the discovery of graphene, the hunt has been on for similar two-dimensional crystal lattices, though so far, graphene remains a precious oddity.


'/>"/>

Contact: Joe Caspermeyer
joseph.caspermeyer@asu.edu
480-727-0369
Arizona State University
Source:Eurekalert  

Related biology technology :

1. Cordex Completes Production of ATPace(TM) Clinical Trial Material
2. Oxford Performance Materials Introduces OXPEKK PermettaTM High Performance Polymer Films
3. Biomimetic-engineering design can replace spaghetti tangle of nanotubes in novel material
4. Tepha Partner Launches Novel Monofilament Absorbable Suture Utilizing Tephas Proprietary Biomaterial
5. SAFC Hitech & Air Water Inc. Extend High-End Materials Research Services Collaboration to Support Japan Chip Industry
6. Putting the squeeze on an old material could lead to instant on electronic memory
7. Connecting Materials Science With Biology, K-State Engineers Create DNA Sensors That Could Identify Cancer Using Material Only One Atom Thick
8. Researchers create catalysts for use in hydrogen storage materials
9. How Long Will the Economic Downturn Affect the Dental Biomaterials Market?
10. MIT: New material could lead to faster chips
11. New organic material may speed Internet access
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Material world: Graphene's versatility promises new applications
(Date:5/25/2016)... ... May 25, 2016 , ... The ... by the Office of the National Coordinator for Health IT (ONC) outlining a ... clinically relevant data were available when and where it was needed. The organization ...
(Date:5/25/2016)... ... ... Lady had been battling arthritis since the age of two and at the ... Hannah sought the help of Dr Jeff Christiansen of Superior Veterinary Surgical Solutions ... help with the pain of Lady’s arthritis. Dr Christiansen suggested that in conjunction with ...
(Date:5/24/2016)... 24, 2016   MedyMatch Technology Ltd ., the data ... real-time decision support tools in the emergency room, announced today ... Israeli Advanced Technology Industries (IATI) BioMed Conference. ... 15th National Life Sciences and Technology Week, and is ... Hotel in Tel Aviv, Israel . ...
(Date:5/23/2016)... Texas (PRWEB) , ... May 23, 2016 , ... The need for blood donations in ... this week by the South Texas Blood & Tissue Center, blood donations are on the ... 30 years, and they are down 21 percent in South Texas in the last four ...
Breaking Biology Technology:
(Date:3/31/2016)... , March 31, 2016   ... ("LegacyXChange" or the "Company") LegacyXChange is excited ... of its soon to be launched online site for ... https://www.youtube.com/channel/UCyTLBzmZogV1y2D6bDkBX5g ) will also provide potential shareholders a ... DNA technology to an industry that is notorious for ...
(Date:3/23/2016)... 2016 Einzigartige ... und Stimmerkennung mit Passwörtern     ... MESG ), ein führender Anbieter digitaler Kommunikationsdienste, ... SpeechPro zusammenarbeitet, um erstmals dessen Biometrietechnologie einzusetzen. ... Möglichkeit angeboten, im Rahmen mobiler Apps neben ...
(Date:3/21/2016)... , March 22, 2016 ... recognition with passcodes for superior security   ... a leading provider of secure digital communications services, today ... biometric technology and offer enterprise customers, particularly those in ... facial recognition and voice authentication within a mobile app, ...
Breaking Biology News(10 mins):