Nanotechnology Now





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Laying down a discerning membrane

Abstract:
One of the thinnest membranes ever made is also highly discriminating when it comes to the molecules going through it. Engineers at the University of South Carolina have constructed a graphene oxide membrane less than 2 nanometers thick with high permeation selectivity between hydrogen and carbon dioxide gas molecules.

Laying down a discerning membrane

Columbia, SC | Posted on October 4th, 2013

The selectivity is based on molecular size, the team reported in the journal Science. Hydrogen and helium pass relatively easily through the membrane, but carbon dioxide, oxygen, nitrogen, carbon monoxide and methane permeate much more slowly.

"The hydrogen kinetic diameter is 0.289 nm, and carbon dioxide is 0.33 nm. The difference in size is very small, only 0.04 nm, but the difference in permeation is quite large" said Miao Yu, a chemical engineer in USC's College of Engineering and Computing who led the research team. "The membrane behaves like a sieve. Bigger molecules cannot go through, but smaller molecules can."

In addition to selectivity, what's remarkable about the USC team's result is the quality of the membrane they were able to craft on such a small scale. The membrane is constructed on the surface of a porous aluminum oxide support. Flakes of graphene oxide, with widths on the order of 500 nm but just one carbon atom thick, were deposited on the support to create a circular membrane about 2 square centimeters in area.

The membrane is something of an overlapping mosaic of graphene oxide flakes. It's like covering the surface of a table with playing cards. And doing that on a molecular scale is very hard if you want uniform coverage and no places where you might get "leaks." Gas molecules are looking for holes anywhere they can be found, and in a membrane made up of graphene oxide flakes, there would be two likely places: holes within the flakes, or holes between the flakes.

It's the spaces between flakes that have been a real obstacle to progress in light gas separations. That's why microporous membranes designed to distinguish in this molecular range have typically been very thick. "At least 20 nm, and usually thicker," said Miao. Anything thinner and the gas molecules could readily find their way between non-uniform spaces between flakes.

Miao's team devised a method of preparing a membrane without those "inter-flake" leaks. They dispersed graphene oxide flakes, which are highly heterogeneous mixtures when prepared with current methods, in water and used sonication and centrifugation techniques to prepare a dilute, homogeneous slurry. These flakes were then laid down on the support by simple filtration.

Their thinnest result was a 1.8-nm-thick membrane that only allowed gas molecules to pass through holes in the graphene oxide flakes themselves, the team reported. They found by atomic force microscopy that a single graphene oxide flake had a thickness of approximately 0.7 nm. Thus, the 1.8-nm-thick membrane on aluminum oxide is only a few molecular layers thick, with molecular defects within the graphene oxide that are essentially uniform and just a little too small to let carbon dioxide through easily.

The advance has a range of potential applications. With widespread concerns about carbon dioxide as a greenhouse gas, the efficient separation of carbon dioxide from other gases is a high research priority. Moreover, hydrogen represents an integral commodity in energy systems involving, for example, fuel cells, so purifying it from gas mixtures is also an active area of interest.

Yu also notes that the dimensions of the molecular sieve are on the order of the size of water, so, for example, purifying the copious amounts of tainted water produced by hydraulic fracturing (fracking) is another possibility.

Being able to reduce membrane thickness - and by an order of magnitude - is a big step forward, Yu said. "Having membranes so thin is a big advantage in separation technology," he said. "It represents a completely new type of membrane in the separation sciences."

####

For more information, please click here

Contacts:
Steven Powell

803-777-1923

Copyright © University of South Carolina

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

The Hydrogen-Fuel cell will revolutionize the economy of the world: New non-platinum and nanosized catalyst for polymer electrolyte fuel cell June 29th, 2015

June 29th, 2015

Efforts to Use Smart Nanocarriers to Cure Leukemia Yield Promising Results June 29th, 2015

Making new materials with micro-explosions: ANU media release: Scientists have made exotic new materials by creating laser-induced micro-explosions in silicon, the common computer chip material June 29th, 2015

Graphene

Angstron Materials Appoints VP for Business Development And Engineering June 27th, 2015

Spain nanotechnology featured at NANO KOREA 2015 June 26th, 2015

Breakthrough graphene production could trigger revolution in artificial skin development June 25th, 2015

Towards graphene biosensors June 24th, 2015

Discoveries

The Hydrogen-Fuel cell will revolutionize the economy of the world: New non-platinum and nanosized catalyst for polymer electrolyte fuel cell June 29th, 2015

June 29th, 2015

Efforts to Use Smart Nanocarriers to Cure Leukemia Yield Promising Results June 29th, 2015

Making new materials with micro-explosions: ANU media release: Scientists have made exotic new materials by creating laser-induced micro-explosions in silicon, the common computer chip material June 29th, 2015

Materials/Metamaterials

Green Chemistry Methods Used in Iran to Produce Zinc Oxide Nanoparticles June 27th, 2015

Spain nanotechnology featured at NANO KOREA 2015 June 26th, 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

Iranian Researchers Synthesize Nanostructures with Controlled Shape, Structure June 25th, 2015

Announcements

The Hydrogen-Fuel cell will revolutionize the economy of the world: New non-platinum and nanosized catalyst for polymer electrolyte fuel cell June 29th, 2015

June 29th, 2015

Efforts to Use Smart Nanocarriers to Cure Leukemia Yield Promising Results June 29th, 2015

Making new materials with micro-explosions: ANU media release: Scientists have made exotic new materials by creating laser-induced micro-explosions in silicon, the common computer chip material June 29th, 2015

Environment

The peaks and valleys of silicon: Team of USC Viterbi School of Engineering Researchers introduce new layered semiconducting materials as silicon alternative June 27th, 2015

NNI Publishes Workshop Report and Launches Web Portal on Nanosensors: Both outputs support the Nanotechnology Signature Initiative ‘Nanotechnology for Sensors and Sensors for Nanotechnology: Improving and Protecting Health, Safety, and the Environment’ June 24th, 2015

New composite material as CO2 sensor June 8th, 2015

Cheap Method to Measure Medications in Contaminated Water June 6th, 2015

Energy

The Hydrogen-Fuel cell will revolutionize the economy of the world: New non-platinum and nanosized catalyst for polymer electrolyte fuel cell June 29th, 2015

June 29th, 2015

Making new materials with micro-explosions: ANU media release: Scientists have made exotic new materials by creating laser-induced micro-explosions in silicon, the common computer chip material June 29th, 2015

X-rays and electrons join forces to map catalytic reactions in real-time: New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions June 29th, 2015

Water

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

Ceramic Nanomembrane, New Material for Dehydration of Natural Gas June 7th, 2015

Cheap Method to Measure Medications in Contaminated Water June 6th, 2015

Fuel Cells

The Hydrogen-Fuel cell will revolutionize the economy of the world: New non-platinum and nanosized catalyst for polymer electrolyte fuel cell June 29th, 2015

X-rays and electrons join forces to map catalytic reactions in real-time: New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions June 29th, 2015

Buckle up for fast ionic conduction June 16th, 2015

A protective shield for sensitive catalysts: Hydrogels block harmful oxygen June 15th, 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