Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Graphene: Singles and the few

C.N.R. Rao and colleagues have published a timely review analyzing the correlation of synthesis methods and physical properties of single-layer and few-layered graphene flakes. The paper was published in Science and Technology of Advanced Materials.

A timely review analyzing the correlation of synthesis methods and physical properties of single-layer and few-layered graphene flakes.

A review of methods used for synthesizing both single and few-layer graphene and the resulting properties is presented by C.N.R. Rao and colleagues at the Jawaharlal Nehru Centre for Advanced Scientific Research and Indian Institute of Science, Bangalore. The article was published recently in Science and Technology of Advanced Materials.

The group not only compares the electrical, magnetic and surface properties of the resulting graphene [2] but based on their own research, the authors describe the physical properties of graphene-polymer composites and field-effect transistors fabricated using graphene.

Since the first report on the mechanical isolation of graphene from graphite, the interest in the physical properties and potential applications—such as transparent electrodes for solar cells, nano-electronics and robust mechanical structures—has led to an unprecedented increase in the number of publications on the synthesis, properties and applications of this unique 2D-material.

But the field is still in its infancy, with challenges and issues to be resolved, in particular the effects of the synthesis method on the properties of the resulting graphene.

The Nobel Prize in Physics 2010 was awarded to Andre Geim and Konstantin Novoselov of University of Manchester "for groundbreaking experiments regarding the two-dimensional material graphene"—a unique structure of carbon just one atom thick that has caught the imagination of materials scientists world-wide.

The Manchester researchers reported on the extraction and properties of graphene in 2004 [1]. The simplicity of the ‘synthesis’ surprised many scientists, for who would have imagined being able to isolate an atomic layer of carbon from a block of graphite with a piece of adhesive tape?

Single-layer graphene (SLG) is produced by mechanically ‘peeling off’ a layer of carbon from highly ordered pyrolytic graphite, which is then transferred onto a silicon substrate. Chemically, SLG is prepared by the reduction of a dispersion of single-layer graphene oxide with hydrazine. This resulting reduced graphene oxide (RGO) is a black suspension that contains residual oxygen, and this distinguishes it from SLG obtained by other methods.

Non-chemical methods of producing SLG layers include heating Si-terminated (0001) single-crystal 6H-SiC in vacuum between 1250 and 1450 ºC for a few minutes and decomposition of hydrocarbons— methane, ethylene, acetylene and benzene— on sheets of catalytic transition metals such as Ni. The authors’ own research on chemical vapor deposition on nickel and cobalt films showed the number of layers to depend on the choice of hydrocarbons and experimental conductions, and importantly, that the graphene layers were difficult to remove from the metal surface after cooling.

Well-known methods for producing few-layer graphene are thermal exfoliation of graphite oxide at 1050 ºC, the chemical reaction of an aqueous solution of SGO with hydrazine hydrate at the refluxing temperature or by microwave heating, heating 4–6 nm nanodiamond particles in an inert or reducing atmosphere above 1500 ºC, and arc evaporation of graphite in a hydrogen atmosphere. The team found the latter method yields graphene with only 2–3 layers of 100–200 nm sized flakes although they note that controlling the number of layers of graphene is still a challenge.

The surface area of graphene is an important parameter for applications such as gas sensing and storage of gases such as hydrogen. In comparison to single-layer graphene, which theory predicts to have a large surface area of 2600 m2/g, measurements by the Bangalore group on few-layer graphene showed the surface area to be 270–1550 m2/g.

The electronic structure of graphene is determined by the ‘edge states’ of graphene flakes, with bilayer graphene predicted to be ferromagnetic. Rao and co-workers showed the Curie-Weiss temperatures obtained from the high-temperature inverse susceptibility data to be negative in all samples measured by them, indicating antiferromagnetism. The authors note the possibility of the coexistence of different types of magnetic states within a single flake of graphene. In addition, all graphene samples showed magnetic hysteresis at room temperature, with electron paramagnetic resonance measurements suggesting that this behavior did not originate from transition-metal impurities.

Electrical measurements showed semiconducting behavior in few-layer graphenes with conductivity increasing between 35 and 300 K, which is different from the metallic nature exhibited by the single-layer graphene, and the electrical conductivity of graphene samples decreased with increasing number of layers. Furthermore, few-layer graphene samples were n-type and suitable for the fabrication of field-effect transistors, and the best transistors were realized with few-layer graphene produced by arc discharge of graphite in hydrogen. In measurements on composites of a polymer and few-layer graphene (PMMA-RGO, PMMA-HG and PVA-EG), the electrical conductivity of the composites increased with increasing graphene content. Thermoelectric measurements revealed a relatively small thermopower in few-layer graphenes compared with single-layer graphene. Interestingly, few-layer graphenes with the largest surface area showed the strongest interaction with electron-donor and acceptor molecules via molecular charge transfer.

This review contains 68 references and 21 figures and provides an invaluable source of up-to-date information for newcomers and experts in this exciting area of research.

References and related websites

[1] Science 306 (2004) p. 666
[2] Science and Technology of Advanced Materials 11 (2010) October. {}
Sci Technol Adv Mater Vol.11 (2010) 054502
doi: 10.1088/1468-6996/11/5/054502
[3] Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India {}

[4] Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India { }

[5] National Institute for Materials Science {}

Media contacts:
Mikiko Tanifuji (Ms.)
National Institute for Materials Science, Tsukuba, Japan
Tel. +81-(0)29-859-2494
Journal information
Sci Technol Adv Mater Vol.11 (2010) 054502 doi: 10.1088/1468-6996/11/5/054502

Mikiko Tanifuji | Research asia research news
Further information:

More articles from Materials Sciences:

nachricht From ancient fossils to future cars
21.10.2016 | University of California - Riverside

nachricht Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>