Nanotechnology Now





Heifer International

Wikipedia Affiliate Button


DHgate

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

Miniature Technology, Large-Scale Impact: Winner of the 2015 Lindros Award for translational medicine, Kjeld Janssen is pushing the boundaries of the emerging lab-on-a-chip technology - See more at: http://www.news.ucsb.edu/2015/015744/miniature-technology-large-scale-impact#stha July 7th, 2015

Tel Aviv/Tsinghua University project uses crowd computing to improve water filtration: The research, a product of the new TAU-Tsinghua XIN Center, was conducted by 150,000 volunteers at IBM's World Community Grid July 6th, 2015

Transition from 3 to 2 dimensions increases conduction, MIPT scientists discover July 6th, 2015

A Stretchy Mesh Heater for Sore Muscles July 6th, 2015

Graphene

Transition from 3 to 2 dimensions increases conduction, MIPT scientists discover July 6th, 2015

BBC World Service to broadcast Forum discussion on graphene July 6th, 2015

Graphene flexes its electronic muscles: Rice-led researchers calculate electrical properties of carbon cones, other shapes June 30th, 2015

Laboratories

Influential Interfaces Lead to Advances in Organic Spintronics July 1st, 2015

NIST ‘How-To’ Website Documents Procedures for Nano-EHS Research and Testing July 1st, 2015

Ultra-stable JILA microscopy technique tracks tiny objects for hours July 1st, 2015

Govt.-Legislation/Regulation/Funding/Policy

Surfing a wake of light: Researchers observe and control light wakes for the first time July 6th, 2015

New technology using silver may hold key to electronics advances July 2nd, 2015

NIST Group Maps Distribution of Carbon Nanotubes in Composite Materials July 2nd, 2015

Influential Interfaces Lead to Advances in Organic Spintronics July 1st, 2015

Nanomedicine

Miniature Technology, Large-Scale Impact: Winner of the 2015 Lindros Award for translational medicine, Kjeld Janssen is pushing the boundaries of the emerging lab-on-a-chip technology - See more at: http://www.news.ucsb.edu/2015/015744/miniature-technology-large-scale-impact#stha July 7th, 2015

A Stretchy Mesh Heater for Sore Muscles July 6th, 2015

New Biosensor Produced in Iran to Detect Effective Drugs in Cancer Treatment July 4th, 2015

Groundbreaking research to help control liquids at micro and nano scales July 3rd, 2015

Discoveries

Miniature Technology, Large-Scale Impact: Winner of the 2015 Lindros Award for translational medicine, Kjeld Janssen is pushing the boundaries of the emerging lab-on-a-chip technology - See more at: http://www.news.ucsb.edu/2015/015744/miniature-technology-large-scale-impact#stha July 7th, 2015

Fundamental observation of spin-controlled electrical conduction in metals: Ultrafast terahertz spectroscopy yields direct insight into the building block of modern magnetic memories July 6th, 2015

Surfing a wake of light: Researchers observe and control light wakes for the first time July 6th, 2015

Transition from 3 to 2 dimensions increases conduction, MIPT scientists discover July 6th, 2015

Announcements

Miniature Technology, Large-Scale Impact: Winner of the 2015 Lindros Award for translational medicine, Kjeld Janssen is pushing the boundaries of the emerging lab-on-a-chip technology - See more at: http://www.news.ucsb.edu/2015/015744/miniature-technology-large-scale-impact#stha July 7th, 2015

Tel Aviv/Tsinghua University project uses crowd computing to improve water filtration: The research, a product of the new TAU-Tsinghua XIN Center, was conducted by 150,000 volunteers at IBM's World Community Grid July 6th, 2015

Transition from 3 to 2 dimensions increases conduction, MIPT scientists discover July 6th, 2015

A Stretchy Mesh Heater for Sore Muscles July 6th, 2015

Tools

A 'movie' of ultrafast rotating molecules at a hundred billion per second: A quantum wave-like nature was successfully observed in rotating nitrogen molecules July 4th, 2015

Clues to inner atomic life from subtle light-emission shifts: Hyperfine structure of light absorption by short-lived cadmium atom isotopes reveals characteristics of the nucleus that matter for high precision detection methods July 3rd, 2015

Nanometrics to Announce Second Quarter Financial Results on July 23, 2015 July 2nd, 2015

Ultra-stable JILA microscopy technique tracks tiny objects for hours July 1st, 2015

Water

Tel Aviv/Tsinghua University project uses crowd computing to improve water filtration: The research, a product of the new TAU-Tsinghua XIN Center, was conducted by 150,000 volunteers at IBM's World Community Grid July 6th, 2015

Visible Light-Sensitive Photocatalysts Used for Purification of Contaminated Water in Iran June 30th, 2015

Dais Analytic Unveils New Version of Aqualyte Membrane Technology: Updates to the Basis of the Company's Industry-Changing Nanotechnology Designed to Strengthen Position in Global Air, Energy, and Water Markets June 26th, 2015

Bacteria Cellulose, Natural Polymers with Applications in Various Industries Synthesized in Iran June 22nd, 2015

Nanobiotechnology

Groundbreaking research to help control liquids at micro and nano scales July 3rd, 2015

Engineering the world’s smallest nanocrystal July 2nd, 2015

Nanometric sensor designed to detect herbicides can help diagnose multiple sclerosis June 23rd, 2015

Newly-Developed Biosensor in Iran Detects Cocaine Addiction June 23rd, 2015

Research partnerships

Fundamental observation of spin-controlled electrical conduction in metals: Ultrafast terahertz spectroscopy yields direct insight into the building block of modern magnetic memories July 6th, 2015

Surfing a wake of light: Researchers observe and control light wakes for the first time July 6th, 2015

Tel Aviv/Tsinghua University project uses crowd computing to improve water filtration: The research, a product of the new TAU-Tsinghua XIN Center, was conducted by 150,000 volunteers at IBM's World Community Grid July 6th, 2015

Groundbreaking research to help control liquids at micro and nano scales July 3rd, 2015

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