Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Graphene offers protection from intense laser pulses: Researchers from Singapore and the UK have jointly announced a new benchmark in broadband, non-linear optical-limiting behavior using single-sheet graphene dispersions in a variety of heavy-atom solvents and film matrices

The new optical-induced absorption mechanisms [a] Photoexcitation of a dispersed graphene single sheet gives long-lived electron-hole pairs. Further excitation causes the appearance of localized states such as (i) excitons (neutral excited state) or (ii) polarons (charged excited state) due to interactions. [b] For comparison, graphite gives on electron-hole gas that is very short-lived due to fast cooling and re-combination.

Credit: National University of Singapore
The new optical-induced absorption mechanisms [a] Photoexcitation of a dispersed graphene single sheet gives long-lived electron-hole pairs. Further excitation causes the appearance of localized states such as (i) excitons (neutral excited state) or (ii) polarons (charged excited state) due to interactions. [b] For comparison, graphite gives on electron-hole gas that is very short-lived due to fast cooling and re-combination.

Credit: National University of Singapore

Abstract:
Single-sheet graphene dispersion when substantially spaced apart in liquid cells or solid film matrices can exhibit novel excited state absorption mechanism that can provide highly effective broadband optical limiting well below the onset of microbubble or microplasma formation.

Graphene offers protection from intense laser pulses: Researchers from Singapore and the UK have jointly announced a new benchmark in broadband, non-linear optical-limiting behavior using single-sheet graphene dispersions in a variety of heavy-atom solvents and film matrices

Singapore | Posted on December 30th, 2011

Graphenes are single sheets of carbon atoms bonded into a hexagonal array. In nature, they tend to stack to give graphite.

In a breakthrough, researchers from the National University of Singapore (NUS), DSO National Laboratories and University of Cambridge have developed a method to prevent the re-stacking of these sheets by attaching alkyl surface chains to them, while retaining the integrity of the nano-graphene pockets on the sheets.

This method in turn produced a material that can be processed in a solution and dispersible into solvents and film matrices. As a consequence, the researchers observed a new phenomenon. They found that the dispersed graphenes exhibit a giant non-linear optical-absorption response to intense nanosecond laser pulses over a wide spectral range with a threshold that was much lower than that found in carbon black suspensions and carbon nanotubes suspensions. This set a new record in energy limiting onset of 10 mJ/cm^2 for a linear transmittance of 70%.

The mechanism for this new phenomenon is outlined in Figure 1 in which the initially delocalized electron-hole gas localizes at high-excitation densities in the presence of heavy atoms, to produce strong absorbing excitons. The resultant excited-state absorption mechanism can be very effective.

These optical limiting materials can now be used for protection of sensitive sensors and devices from laser damage, and for optical circuits. They can be also used in anti-glare treated devices.

The principal investigator of the NUS Organic Nano Device Laboratory's graphene team, Professor Lay-Lay Chua who is also from the NUS Department of Chemistry and Department of Physics, says: "We found from ultrafast spectroscopy measurements that dispersed graphene sheets switch their behavior from induced optical transparency which is well-known, to induced optical absorption depending on its environment. This is a remarkable finding that shows graphene can still surprise!"

The principal investigator of the graphene team at DSO National Laboratories, Professor Geok-Kieng Lim who is also an Adjunct Professor at NUS Department of Physics, says: "This is an important first step in the development of practical graphene nano-composite films for applications where the graphene sheets remain fully dispersed. The induced change in their non-linear optical behavior is amazing and highly practical!"

####

About National University of Singapore
A leading global university centred in Asia, the National University of Singapore (NUS) is Singapore's flagship university which offers a global approach to education and research, with a focus on Asian perspectives and expertise.

NUS has 16 faculties and schools across three campuses. Its transformative education includes a broad-based curriculum underscored by multi-disciplinary courses and cross-faculty enrichment. Over 36,000 students from 100 countries enrich the community with their diverse social and cultural perspectives.

NUS has three Research Centres of Excellence (RCE) and 21 university-level research institutes and centres. It is also a partner in Singapore's 5th RCE. NUS shares a close affiliation with 16 national-level research institutes and centres. Research activities are strategic and robust, and NUS is well-known for its research strengths in engineering, life sciences and biomedicine, social sciences and natural sciences. It also strives to create a supportive and innovative environment to promote creative enterprise within its community.

For more information, please visit National University of Singapore.

For more information, please click here

Contacts:
Lay-Lay Chua

65-651-64834

Copyright © National University of Singapore

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 Links

'Giant broadband nonlinear optical absorption response in dispersed graphene single sheets' by Geok-Kieng Lim, Zhi-Li Chen, Jenny Clark, Roland G.S. Goh, Wee-Hao Ng, Hong-Wee Tan, Richard H. Friend, Peter K. H. Ho and Lay-Lay Chua was published on 21 August 2011 in Nature Photonics and is available at www.nature.com/nphoton (doi:10.1038/nphoton.2011.177).

Related News Press

News and information

Oxford Instruments announces Dr Kate Ross as winner of the 2018 Lee Osheroff Richardson Science Prize for North and South America February 20th, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Unconventional superconductor may be used to create quantum computers of the future: They have probably succeeded in creating a topological superconductor February 19th, 2018

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

Graphene/ Graphite

Graphene on toast, anyone? Rice University scientists create patterned graphene onto food, paper, cloth, cardboard February 13th, 2018

A new radiation detector made from graphene: A new bolometer exploits the thermoelectric properties of graphene February 6th, 2018

Engineers develop flexible, water-repellent graphene circuits for washable electronics January 24th, 2018

New catalyst for hydrogen production is a step toward clean fuel: Carbon-based nanocomposite with embedded metal ions yields impressive performance as catalyst for electrolysis of water to generate hydrogen January 16th, 2018

Thin films

A simple new approach to plastic solar cells: Osaka University researchers intelligently design new highly efficient organic solar cells based on amorphous electronic materials with potential for easy printing January 28th, 2018

Scientists reveal the fundamental limitation in the key material for solid-state lighting January 25th, 2018

Discoveries

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Unconventional superconductor may be used to create quantum computers of the future: They have probably succeeded in creating a topological superconductor February 19th, 2018

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers February 15th, 2018

Announcements

Oxford Instruments announces Dr Kate Ross as winner of the 2018 Lee Osheroff Richardson Science Prize for North and South America February 20th, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Unconventional superconductor may be used to create quantum computers of the future: They have probably succeeded in creating a topological superconductor February 19th, 2018

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

Photonics/Optics/Lasers

Photonic chip guides single photons, even when there are bends in the road February 16th, 2018

Rutgers-Led Innovation Could Spur Faster, Cheaper, Nano-Based Manufacturing: Scalable and cost-effective manufacturing of thin film devices February 14th, 2018

Understanding brain functions using upconversion nanoparticles: Researchers can now send light deep into the brain to study neural activities February 14th, 2018

Graphene on toast, anyone? Rice University scientists create patterned graphene onto food, paper, cloth, cardboard February 13th, 2018

Research partnerships

Computers aid discovery of new, inexpensive material to make LEDs with high color quality February 20th, 2018

Rutgers-Led Innovation Could Spur Faster, Cheaper, Nano-Based Manufacturing: Scalable and cost-effective manufacturing of thin film devices February 14th, 2018

Understanding brain functions using upconversion nanoparticles: Researchers can now send light deep into the brain to study neural activities February 14th, 2018

Vanadium dioxyde: A revolutionary material for tomorrow's electronics: Phase-chance switch can now be performed at higher temperatures February 5th, 2018

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