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

Leti to Demo Wristband with Embedded Sensors to Diagnose Sleep Apnea: APNEAband, Which Will Be Demonstrated at CES 2018, Also Monitors Mountain Sickness, Dehydration, Dialysis Treatment Response and Epileptic Seizures December 12th, 2017

Leti Develops World’s First Micro-Coolers for CERN Particle Detectors: Leti Design, Fabrication and Packaging Expertise Extends to Very Large Scientific Instruments December 11th, 2017

Untangling DNA: Researchers filter the entropy out of nanopore measurements December 8th, 2017

Device makes power conversion more efficient: New design could dramatically cut energy waste in electric vehicles, data centers, and the power grid December 8th, 2017

JPK Instruments announce partnership with Swiss company, Cytosurge AG. The partnership makes Cytosurge’s FluidFM® technology available on the JPK NanoWizard® AFM platform December 8th, 2017

Graphene/ Graphite

UCLA chemists synthesize narrow ribbons of graphene using only light and heat: Tiny structures could be next-generation solution for smaller electronic devices December 8th, 2017

Thin films

MIPT scientists revisit optical constants of ultrathin gold films October 20th, 2017

Rice University chemists make laser-induced graphene from wood July 31st, 2017

Graduate Students from Across the Country Attend Hands-on NanoCamp: Prominent scientists Warren Oliver, Ph.D., and George Pharr, Ph.D., presented a weeklong NanoCamp for hand-picked graduate students across the United States July 26th, 2017

Studying Argon Gas Trapped in Two-Dimensional Array of Tiny "Cages": Understanding how individual atoms enter and exit the nanoporous frameworks could help scientists design new materials for gas separation and nuclear waste remediation July 17th, 2017

Discoveries

UCLA chemists synthesize narrow ribbons of graphene using only light and heat: Tiny structures could be next-generation solution for smaller electronic devices December 8th, 2017

Untangling DNA: Researchers filter the entropy out of nanopore measurements December 8th, 2017

Device makes power conversion more efficient: New design could dramatically cut energy waste in electric vehicles, data centers, and the power grid December 8th, 2017

Wheat gets boost from purified nanotubes: Rice University toxicity study shows plant growth enhanced by -- but only by -- purified nanotubes December 6th, 2017

Announcements

Leti to Demo Wristband with Embedded Sensors to Diagnose Sleep Apnea: APNEAband, Which Will Be Demonstrated at CES 2018, Also Monitors Mountain Sickness, Dehydration, Dialysis Treatment Response and Epileptic Seizures December 12th, 2017

Leti Develops World’s First Micro-Coolers for CERN Particle Detectors: Leti Design, Fabrication and Packaging Expertise Extends to Very Large Scientific Instruments December 11th, 2017

Untangling DNA: Researchers filter the entropy out of nanopore measurements December 8th, 2017

Device makes power conversion more efficient: New design could dramatically cut energy waste in electric vehicles, data centers, and the power grid December 8th, 2017

Photonics/Optics/Lasers

Leti Integrates Hybrid III-V Silicon Lasers on 200mm Wafers with Standard CMOS Process December 6th, 2017

Scientists make transparent materials absorb light December 1st, 2017

Going swimmingly: Biotemplates breakthrough paves way for cheaper nanobots: By using bacterial flagella as a template for silica, researchers have demonstrated an easier way to make propulsion systems for nanoscale swimming robots November 30th, 2017

Fast flowing heat in graphene heterostructures: Surprisingly fast heat flow from graphene to its surrounding November 29th, 2017

Research partnerships

Wheat gets boost from purified nanotubes: Rice University toxicity study shows plant growth enhanced by -- but only by -- purified nanotubes December 6th, 2017

Copper will replace toxic palladium and expensive platinum in the synthesis of medications: The effectiveness of copper nanoparticles as a catalyst has been proven December 5th, 2017

Researchers advance technique to detect ovarian cancer: Rice, MD Anderson use fluorescent carbon nanotube probes to achieve first in vivo success November 30th, 2017

Tiny robots step closer to treating hard-to-reach parts of the body November 25th, 2017

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



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project