Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

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

Raman Whispering Gallery Detects Nanoparticles September 1st, 2014

A new, tunable device for spintronics: An international team of scientists including physicist Jairo Sinova from the University of Mainz realises a tunable spin-charge converter made of GaAs August 29th, 2014

Nanoscale assembly line August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Chemistry

Production of Toxic Ion Nanosorbents with High Sorption Capacity in Iran August 17th, 2014

Scientists fold RNA origami from a single strand: RNA origami is a new method for organizing molecules on the nanoscale. Using just a single strand of RNA, this technique can produce many complicated shapes. August 14th, 2014

Could hemp nanosheets topple graphene for making the ideal supercapacitor? August 12th, 2014

Iranians Find Novel Method for Processing Highly Pure Ceramic Nanoparticles August 12th, 2014

Govt.-Legislation/Regulation/Funding/Policy

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Leading European communications companies and research organizations have launched an EU project developing the future 5th Generation cellular mobile networks August 28th, 2014

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

Discoveries

Raman Whispering Gallery Detects Nanoparticles September 1st, 2014

A new, tunable device for spintronics: An international team of scientists including physicist Jairo Sinova from the University of Mainz realises a tunable spin-charge converter made of GaAs August 29th, 2014

Nanoscale assembly line August 29th, 2014

Copper shines as flexible conductor August 29th, 2014

Announcements

Raman Whispering Gallery Detects Nanoparticles September 1st, 2014

Nanoscale assembly line August 29th, 2014

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Military

Fonon Announces 3D Metal Sintering Technology: Emerging Additive Nano Powder Manufacturing Technology August 28th, 2014

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

Introducing the multi-tasking nanoparticle: Versatile particles offer a wide variety of diagnostic and therapeutic applications August 26th, 2014

Biomimetic photodetector 'sees' in color: Rice lab uses CMOS-compatible aluminum for on-chip color detection August 25th, 2014

Energy

Novel 'butterfly' molecule could build new sensors, photoenergy conversion devices August 28th, 2014

Aspen Aerogels, Inc. to Present at Barclays CEO Energy-Power Conference August 27th, 2014

Competition for Graphene: Berkeley Lab Researchers Demonstrate Ultrafast Charge Transfer in New Family of 2D Semiconductors August 26th, 2014

Chemical reaction yields "tapes" of porphin molecules: Flexible tapes from the nanoworld August 13th, 2014

Aerospace/Space

Fonon Announces 3D Metal Sintering Technology: Emerging Additive Nano Powder Manufacturing Technology August 28th, 2014

Nanodiamonds Are Forever: A UCSB professor’s research examines 13,000-year-old nanodiamonds from multiple locations across three continents August 27th, 2014

Creation of a Highly Efficient Technique to Develop Low-Friction Materials Which Are Drawing Attention in Association with Energy Issues August 26th, 2014

Thermal Block Coatings Developed in Iran Using Nanotechnology August 26th, 2014

Fuel Cells

Media Advisory: Minister Rempel to Announce Support for Alberta's Nanotechnology Sector June 20th, 2014

Evolution of a Bimetallic Nanocatalyst June 6th, 2014

University of Surrey collaborates with India and Tata Steel to revolutionise renewable energy March 26th, 2014

Novel membrane reveals water molecules will bounce off a liquid surface: Study may lead to more efficient water-desalination systems, fundamental understanding of fluid flow March 16th, 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