Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button

Home > Press > A hot bath for gold nanoparticles

A schematic diagram shows a gold nanoparticle stabilized with polyvinyl alcohol (PVA) ligands.
A schematic diagram shows a gold nanoparticle stabilized with polyvinyl alcohol (PVA) ligands.

Abstract:
Gold nanoparticles, says Chris Kiely, are fast becoming some of the most effective diplomats of the nanoworld.

They facilitate a wide range of chemical reactions between molecules that would not normally interact or would do so only at much higher temperatures.

And in most cases, they effect a single favorable outcome with few, if any, unwanted side reactions.

A hot bath for gold nanoparticles

Bethlehem, PA | Posted on August 2nd, 2011

In short, says Kiely, a professor of materials science and engineering, the nanoparticles are extremely good catalysts.

Conventional methods of preparing gold nanoparticles, however, alter the morphology and catalytic activity of the particles.

Now, an international team of researchers has developed a procedure that enhances the surface exposure of gold nanoparticles and their catalytic activity over a range of reactions.

A new procedure improves on convention

The team reported its results in July in Nature Chemistry in an article titled "Facile removal of stabilizer-ligands from supported gold nanoparticles."

Its members include Kiely and Graham Hutchings, a chemist at Cardiff University in Wales in the U.K., who have studied nanogold together for more than a decade.

"In industry," says Kiely, "the most common way of preparing gold nanocatalysts is to first impregnate a nanocrystalline oxide support, such as titanium oxide (TiO2) with chloroauric acid. A reduction reaction then converts the acid into metal nanoparticles.

"Unfortunately, this leads to a variety of gold species being dispersed on the support, such as isolated gold atoms, mono- and bi-layer clusters, in addition to nanoparticles of various sizes."

An alternative technique that allows more precise control over particle size and structure, is to pre-form the gold nanoparticles in a colloidal solution before depositing them onto the support.

The disadvantage to this method is that during fabrication the nanoparticles are coated with organic molecules - ligands - that prevent them from clumping together. Once they are deposited onto a support, these ligands tend to impair the nanoparticle's catalytic performance by blocking the approach of molecules to active sites on the metal surface.

A milder form of ligand removal

Previous methods for stripping away these ligands have involved heat treatments of up to 400 degrees C.

"At these temperatures the morphology of the nanoparticles changes and they begin to coalesce," says Kiely. "There is also significant decrease in their catalytic activity."

The Kiely-Hutchings team developed a milder alternative for removing the ligands from polyvinyl alcohol-stabilized gold nanoparticles deposited on a titanium oxide support - a simple hot water wash.

Graduate student Ramchandra Tiruvalam used Lehigh's aberration-corrected JEOL 2200 FS transmission electron microscope to examine the catalysts before and after washing and to compare them with those that had undergone heat treatment to remove the ligands.

"Hot water washing had very little effect on particle size," says Kiely, who directs Lehigh's Nanocharacterization Laboratory, "and while the particles retain their cub-octahedral morphology, their surfaces appear to become more distinctly faceted. This is presumably due to some surface reconstruction occurring after losing a significant fraction of the protective PVA ligands."

"Heating the samples to 400 degrees C was also effective at removing the ligands but the average particle size increased from 3.7 to 10.4nm," says Kiely. "There was also tendency for the particles to restructure and develop flatter, more extended interfaces with the underlying TiO2 support."

For the oxidation of carbon monoxide to carbon dioxide, catalysts prepared by this colloidal/hot water wash displayed more than double the activity of conventional gold/TiO2 catalysts. This particular reaction is crucial for the removal of carbon monoxide from enclosed spaces such as submarines and space craft, prolonging the life of fuel cells, and extending the usable lifetime of a firefighter's mask.

This work was funded in part by the National Science Foundation. Tiruvalam is now a research scientist with Haldor Topsoe, a catalyst company in Copenhagen, Denmark.

####

About Lehigh University
Lehigh is a premier residential research university, ranked in the top tier of national research universities each year. We are a coeducational, nondenominational, private university that offers a distinct academic environment of undergraduate and graduate students from across the globe.

For more information, please click here

Contacts:
Carol Kiely

Copyright © Lehigh University

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

New remote-controlled microrobots for medical operations July 23rd, 2016

New superconducting coil improves MRI performance: UH-led research offers higher resolution, shorter scan time July 23rd, 2016

New probe developed for improved high resolution measurement of brain temperature: Improved accuracy could allow researchers to measure brain temperature in times of trauma when small deviations in temperature can lead to additional brain injury July 23rd, 2016

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

Chemistry

New reaction for the synthesis of nanostructures July 21st, 2016

Pushing a single-molecule switch: An international team of researchers from Donostia International Physics Center, Fritz-Haber Institute of the Max Planck Society, University of Liverpool, and the Polish Academy of Sciences has shown a new way to operate a single-molecule switch July 19th, 2016

Rice's 'antenna-reactor' catalysts offer best of both worlds: Technology marries light-harvesting nanoantennas to high-reaction-rate catalysts July 18th, 2016

Researchers improve catalyst efficiency for clean industries: Method reduces use of expensive platinum July 8th, 2016

Govt.-Legislation/Regulation/Funding/Policy

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

New reaction for the synthesis of nanostructures July 21st, 2016

Weird quantum effects stretch across hundreds of miles July 21st, 2016

Scientists glimpse inner workings of atomically thin transistors July 21st, 2016

Discoveries

New remote-controlled microrobots for medical operations July 23rd, 2016

New superconducting coil improves MRI performance: UH-led research offers higher resolution, shorter scan time July 23rd, 2016

Nanoparticle versus cancer: Scientists have created nanoparticles which cure cancer harmlessly July 22nd, 2016

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

Announcements

New remote-controlled microrobots for medical operations July 23rd, 2016

New superconducting coil improves MRI performance: UH-led research offers higher resolution, shorter scan time July 23rd, 2016

New probe developed for improved high resolution measurement of brain temperature: Improved accuracy could allow researchers to measure brain temperature in times of trauma when small deviations in temperature can lead to additional brain injury July 23rd, 2016

Quantum drag:University of Iowa physicist says current in one iron magnetic sheet can create quantized spin waves in another, separate sheet July 22nd, 2016

Military

Scientists develop way to upsize nanostructures into light, flexible 3-D printed materials: Virginia Tech, Livermore National Lab researchers develop hierarchical 3-D printed metallic materials July 20th, 2016

Rice's 'antenna-reactor' catalysts offer best of both worlds: Technology marries light-harvesting nanoantennas to high-reaction-rate catalysts July 18th, 2016

'Green' electronic materials produced with synthetic biology July 16th, 2016

New method can identify chemical warfare agents more easily: The method could help governments protect people from horrifying toxic effects July 15th, 2016

Energy

Researchers discover key mechanism for producing solar cells: Better understanding of perovskite solar cells could boost widespread use July 21st, 2016

The future of perovskite solar cells has just got brighter -- come rain or shine: Korean researchers at POSTECH have succeeded in developing high-efficiency perovskite solar cells that retain excellent performance over two months in a very humid condition July 21st, 2016

Scientists develop way to upsize nanostructures into light, flexible 3-D printed materials: Virginia Tech, Livermore National Lab researchers develop hierarchical 3-D printed metallic materials July 20th, 2016

Rice's 'antenna-reactor' catalysts offer best of both worlds: Technology marries light-harvesting nanoantennas to high-reaction-rate catalysts July 18th, 2016

Aerospace/Space

Scientists move 1 step closer to creating an invisibility cloak July 15th, 2016

Bouncing droplets remove contaminants like pogo jumpers: Researchers at Duke University and the University of British Columbia are exploring whether surfaces can shed dirt without being subjected to fragile coatings July 7th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Novel capping strategy improves stability of perovskite nanocrystals: Study addresses instability issues with organometal-halide perovskites, a promising class of materials for solar cells, LEDs, and other applications June 13th, 2016

Fuel Cells

3-D paper-based microbial fuel cell operating under continuous flow condition July 5th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

VentureLab nanotechnology startup wins TechConnect Innovation Award June 2nd, 2016

Tiny probe could produce big improvements in batteries and fuel cells: A new method helps scientists get an atom's level understanding of electrochemical properties June 1st, 2016

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







Car Brands
Buy website traffic