Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Graphene: Singles and the few

Fig.1: FE-SEM images of two platinum thin-film electrodes separated by 70 nm, (a) without graphene, and (b) with different types of graphene crossing the gap: (b) RGO, (c) HG, and (d) EG
Fig.1: FE-SEM images of two platinum thin-film electrodes separated by 70 nm, (a) without graphene, and (b) with different types of graphene crossing the gap: (b) RGO, (c) HG, and (d) EG

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

Graphene: Singles and the few

UK | Posted on November 8th, 2010

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 {www.sciencemag.org/cgi/content/abstract/306/5696/666}

[2] Science and Technology of Advanced Materials 11 (2010) October. {iopscience.iop.org/1468-6996/11/5/054502} 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 {www.jncasr.ac.in/annview.php?id=239}

[4] Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India
{sscu.iisc.ernet.in/ }

[5] National Institute for Materials Science {www.nims.go.jp/eng/}

####

For more information, please click here

Contacts:
Media contacts:
Mikiko Tanifuji (Ms.)
National Institute for Materials Science, Tsukuba, Japan

Tel. +81-(0)29-859-2494

Copyright © ResearchSEA

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Academic/Education

Rice University launches Rice Synthetic Biology Institute to improve lives January 12th, 2024

Multi-institution, $4.6 million NSF grant to fund nanotechnology training September 9th, 2022

National Space Society Helps Fund Expanding Frontier’s Brownsville Summer Entrepreneur Academy: National Space Society and Club for the Future to Support Youth Development Program in South Texas June 24th, 2022

How a physicist aims to reduce the noise in quantum computing: NAU assistant professor Ryan Behunin received an NSF CAREER grant to study how to reduce the noise produced in the process of quantum computing, which will make it better and more practical April 1st, 2022

Chip Technology

New chip opens door to AI computing at light speed February 16th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

Electrons screen against conductivity-killer in organic semiconductors: The discovery is the first step towards creating effective organic semiconductors, which use significantly less water and energy, and produce far less waste than their inorganic counterparts February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Nanotubes/Buckyballs/Fullerenes/Nanorods/Nanostrings

Catalytic combo converts CO2 to solid carbon nanofibers: Tandem electrocatalytic-thermocatalytic conversion could help offset emissions of potent greenhouse gas by locking carbon away in a useful material January 12th, 2024

TU Delft researchers discover new ultra strong material for microchip sensors: A material that doesn't just rival the strength of diamonds and graphene, but boasts a yield strength 10 times greater than Kevlar, renowned for its use in bulletproof vests November 3rd, 2023

Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023

Detection of bacteria and viruses with fluorescent nanotubes July 21st, 2023

Nanoelectronics

Interdisciplinary: Rice team tackles the future of semiconductors Multiferroics could be the key to ultralow-energy computing October 6th, 2023

Key element for a scalable quantum computer: Physicists from Forschungszentrum Jülich and RWTH Aachen University demonstrate electron transport on a quantum chip September 23rd, 2022

Reduced power consumption in semiconductor devices September 23rd, 2022

Atomic level deposition to extend Moore’s law and beyond July 15th, 2022

Announcements

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project