Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Tiny pores in graphene could give rise to membranes: New membranes may filter water or separate biological samples


A high-resolution scanning transmission electron microscope image taken at Oak Ridge National Laboratory showing a large hole in the graphene (black region in the center). The image is 32 nm by 32 nm, hence the hole is about 10 nm in diameter. The white on the surface of the graphene is contamination, which is a recurring problem for anyone imaging graphene using this technique.
Image courtesy of Juan-Carlos Idrobo
A high-resolution scanning transmission electron microscope image taken at Oak Ridge National Laboratory showing a large hole in the graphene (black region in the center). The image is 32 nm by 32 nm, hence the hole is about 10 nm in diameter. The white on the surface of the graphene is contamination, which is a recurring problem for anyone imaging graphene using this technique.

Image courtesy of Juan-Carlos Idrobo

Abstract:
Much has been made of graphene's exceptional qualities, from its ability to conduct heat and electricity better than any other material to its unparalleled strength: Worked into a composite material, graphene can repel bullets better than Kevlar. Previous research has also shown that pristine graphene a microscopic sheet of carbon atoms arranged in a honeycomb pattern is among the most impermeable materials ever discovered, making the substance ideal as a barrier film.

Tiny pores in graphene could give rise to membranes: New membranes may filter water or separate biological samples

Cambridge, MA | Posted on October 23rd, 2012

But the material may not be as impenetrable as scientists have thought. By engineering relatively large membranes from single sheets of graphene grown by chemical vapor deposition, researchers from MIT, Oak Ridge National Laboratory (ORNL) and elsewhere have found that the material bears intrinsic defects, or holes in its atom-sized armor. In experiments, the researchers found that small molecules like salts passed easily through a graphene membrane's tiny pores, while larger molecules were unable to penetrate.

The results, the researchers say, point not to a flaw in graphene, but to the possibility of promising applications, such as membranes that filter microscopic contaminants from water, or that separate specific types of molecules from biological samples.

"No one has looked for holes in graphene before," says Rohit Karnik, associate professor of mechanical engineering at MIT. "There's a lot of chemical methods that can be used to modify these pores, so it's a platform technology for a new class of membranes."

Karnik and his colleagues, including researchers from the Indian Institute of Technology and King Fahd University of Petroleum and Minerals, have published their results in the journal ACS Nano.

Karnik worked with MIT graduate student Sean O'Hern to look for materials "that could lead to not just incremental changes, but substantial leaps in terms of the way membranes perform." In particular, the team cast around for materials with two key attributes, high flux and tunability: that is, membranes that quickly filter fluids, but are also easily tailored to let certain molecules through while trapping others. The group settled on graphene, in part because of its extremely thin structure and its strength: A sheet of graphene is as thin as a single atom, but strong enough to let high volumes of fluids through without shredding apart.

The team set out to engineer a membrane spanning 25 square millimeters a surface area that is large by graphene standards, holding about a quadrillion carbon atoms. They used graphene synthesized by chemical vapor deposition, borrowing on expertise from the research group of Jing Kong, the ITT Career Development Associate Professor of Electrical Engineering at MIT. The team then developed techniques to transfer the graphene sheet to a polycarbonate substrate dotted with holes.

Once the researchers successfully transferred the graphene, they began to experiment with the resulting membrane, exposing it to flowing water containing molecules of varying sizes. They theorized that if graphene were indeed impermeable, the molecules would be blocked from flowing across. However, experiments showed otherwise, as researchers observed salts flowing through the membrane.

As another test, the team exposed a copper foil with graphene grown on it to a chemical agent that dissolves copper. Instead of protecting the metal, graphene let the agent through, corroding the underlying copper. To test the size of the pores within graphene, the group attempted to filter water with larger molecules. It appeared that there was a limit to the size of the pores, as larger molecules were unable to pass through the membrane.

As a final experiment, Karnik and O'Hern observed the actual holes in the graphene membrane, looking at the material through a high-powered electron microscope at ORNL in collaboration with Juan-Carlos Idrobo. They found that pores ranged in size from about 1 to 12 nanometers just wide enough to selectively let some small molecules through.

"Right now we know from this characterization how the graphene behaves, and what kind of intrinsic pores it has," Karnik says. "In some sense it's the first step to practically realizing graphene-based membranes."

Karnik adds that a near-term application for such membranes may include a portable sensor in which a layer of graphene "could shield the sensor from the environment," letting through only a molecule or contaminant of interest. Another use may be in drug delivery, with graphene, dotted with pores of a determined size, delivering therapies in a controlled release.

"We're right now in the process of transferring more graphene to different substrates and making holes of our own, making a viable membrane for water filtration," O'Hern says.

Scott Bunch, an assistant professor of mechanical engineering at the University of Colorado, says the group's results are the first demonstration that graphene bears defects. The membrane developed by the group "has the potential to be a revolutionary membrane" that separates particles at the molecular scale.

"The issue that now needs to be addressed is whether one can discriminate between smaller molecules," Bunch says. "Once this happens, graphene membranes will eventually live up to the truly remarkable properties that they promise."

Other researchers involved in the work are Cameron Stewart, Michael Boutilier, Sreekar Bhaviripudi, Sarit Das, Tahar Laoui and Muataz Atieh. This work was funded by the King Fahd University of Petroleum and Minerals through the Center for Clean Water and Clean Energy at MIT and KFUPM, and was also supported by the ORNL ShaRE program.

Written by: Jennifer Chu, MIT News Office

####

For more information, please click here

Contacts:
Caroline McCall
MIT News Office

617-253-1682

Copyright © MIT

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

Study finds long-term survival of human neural stem cells transplanted into primate brain April 23rd, 2014

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

National Space Society Congratulates SpaceX on the Success of CRS-3 and the First Flight of the Falcon 9R April 22nd, 2014

Nanoreporters tell 'sour' oil from 'sweet': Rice University's hydrogen sulfide nanoreporters gather intel on oil before pumping April 22nd, 2014

Graphene

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Nanomaterial Outsmarts Ions April 22nd, 2014

Thinnest feasible membrane produced April 17th, 2014

Laboratories

Berkeley Lab Researchers Demonstrate First Size-based Chromatography Technique for the Study of Living Cells April 22nd, 2014

Govt.-Legislation/Regulation/Funding/Policy

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

Cloaked DNA nanodevices survive pilot mission: Successful foray opens door to virus-like DNA nanodevices that could diagnose diseased tissues and manufacture drugs to treat them April 22nd, 2014

Berkeley Lab Researchers Demonstrate First Size-based Chromatography Technique for the Study of Living Cells April 22nd, 2014

Nanomedicine

Study finds long-term survival of human neural stem cells transplanted into primate brain April 23rd, 2014

Cloaked DNA nanodevices survive pilot mission: Successful foray opens door to virus-like DNA nanodevices that could diagnose diseased tissues and manufacture drugs to treat them April 22nd, 2014

Berkeley Lab Researchers Demonstrate First Size-based Chromatography Technique for the Study of Living Cells April 22nd, 2014

Amino-functionalized carbon nanotubes act as a carrier for nerve growth factor April 21st, 2014

Discoveries

Study finds long-term survival of human neural stem cells transplanted into primate brain April 23rd, 2014

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

Berkeley Lab Researchers Demonstrate First Size-based Chromatography Technique for the Study of Living Cells April 22nd, 2014

Announcements

Study finds long-term survival of human neural stem cells transplanted into primate brain April 23rd, 2014

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

National Space Society Congratulates SpaceX on the Success of CRS-3 and the First Flight of the Falcon 9R April 22nd, 2014

Tools

MRI, on a molecular scale: Researchers develop system that could one day peer into the atomic structure of individual molecules April 20th, 2014

Oxford Instruments Asylum Research Introduces the MFP-3D InfinityTM AFM Featuring Powerful New Capabilities and Stunning High Performance April 18th, 2014

More effective kidney stone treatment, from the macroscopic to the nanoscale April 17th, 2014

Scientists Capture Ultrafast Snapshots of Light-Driven Superconductivity: X-rays reveal how rapidly vanishing 'charge stripes' may be behind laser-induced high-temperature superconductivity April 16th, 2014

Water

Thinnest feasible membrane produced April 17th, 2014

Trees go high-tech: process turns cellulose into energy storage devices April 7th, 2014

Dais Analytic Wins SBIR Grant: Dais Analytic Receives US Army Small Business Innovation Research Grant to Further Its Demonstrated Successes in Cleaning Most Forms of Wastewater March 28th, 2014

University of Waterloo Engineering to Showcase Student Design March 14th, 2014

Nanobiotechnology

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

Cloaked DNA nanodevices survive pilot mission: Successful foray opens door to virus-like DNA nanodevices that could diagnose diseased tissues and manufacture drugs to treat them April 22nd, 2014

Targeting cancer with a triple threat: MIT chemists design nanoparticles that can deliver three cancer drugs at a time April 15th, 2014

Biologists Develop Nanosensors to Visualize Movements and Distribution of Plant Stress Hormone April 15th, 2014

Research partnerships

University of Waterloo Visits China to Strengthen Bonds With Research Partners April 21st, 2014

Novel stapled peptide nanoparticle combination prevents RSV infection, study finds April 17th, 2014

Scientists Capture Ultrafast Snapshots of Light-Driven Superconductivity: X-rays reveal how rapidly vanishing 'charge stripes' may be behind laser-induced high-temperature superconductivity April 16th, 2014

Scalable CVD process for making 2-D molybdenum diselenide: Rice, NTU scientists unveil CVD production for coveted 2-D semiconductor April 8th, 2014

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







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE