Featured Research

from universities, journals, and other organizations

Size matters in nanocrystals' ability to adsorb/release gases

Date:
August 6, 2013
Source:
Vanderbilt University
Summary:
More efficient catalytic converters on autos, improved batteries and more sensitive gas sensors are some of the potential benefits of a new system that can directly measure the manner in which nanocrystals adsorb and release hydrogen and other gases.

These are palladium nanocrystals.
Credit: Bardhan Laboratory

More efficient catalytic converters on autos, improved batteries and more sensitive gas sensors are some of the potential benefits of a new system that can directly measure the manner in which nanocrystals adsorb and release hydrogen and other gases.

Related Articles


The technique, which was developed by Vanderbilt University Assistant Professor of Chemical and Biomolecular Engineering Rizia Bardhan, is described in a paper published online Aug. 4 by the journal Nature Materials.

In the last 30 years, there has been a tremendous amount of research studying nanocrystals -- tiny crystals sized between one to 100 nanometers in size (a nanometer is to an inch what an inch is to 400 miles) -- because of the expectation that they have unique physical and chemical properties that can be used in a broad range of applications.

One class of applications depends on nanocrystals' ability to grab specific molecules and particles out the air, hold on to them and then release them: a process called adsorption and desorption. Progress in this area has been hindered by limitations in existing methods for measuring the physical and chemical changes that take place in individual nanocrystals during the process. As a result, advances have been achieved by trial-and-error and have been limited to engineered samples and specific geometries.

"Our technique is simple, direct and uses off-the shelf instruments so other researchers should have no difficulty using it," said Bardhan. Collaborators in the development were Vanderbilt Assistant Professor of Mechanical Engineering Cary Pint, Ali Javey from the University of California, Berkeley and Lester Hedges, Stephen Whitelam and Jeffrey Urban from the Lawrence Berkeley National Laboratory.

The method is based on a standard procedure called fluorescence spectroscopy. A laser beam is focused on the target nanocrystals, causing them to fluoresce. As the nanocrystals adsorb the gas molecules, the strength of their fluorescent dims and as they release the gas molecules, it recovers.

"The fluorescence effect is very subtle and very sensitive to differences in nanocrystal size," she explained. "To see it you must use nanocrystals that are uniform in size." That is one reason why the effect wasn't observed before: Fabrication techniques such as ball milling and other wet-chemical approaches that have been widely used produce nanocrystals in a range of different sizes. These differences are enough to mask the effect.

To test their technique, the researchers studied hydrogen gas sensing with nanocrystals made out of palladium. They choose palladium because it is very stable and it readily releases adsorbed hydrogen. They used hydrogen because of the interest in using it as a replacement for gasoline. One of the major technical obstacles to this scenario is developing a safe and cost-effective storage method. A nanocrystal-based metal hydride system is one of the promising approaches under development.

The measurements they made revealed that the size of the nanocrystals have a much stronger effect on the rate that the material can adsorb and release hydrogen and the amount of hydrogen that the material can absorb than previously expected -- all key properties for a hydrogen storage system. The smaller the particle size, the faster the material can absorb the gas, the more gas it can absorb and faster it can release it.

"In the past, people thought that the size effect was limited to sizes less than 15 to 20 nanometers, but we found that it extends up to 100 nanometers," said Bardhan.

The researchers also determined that the adsorption/desorption rate was determined by just three factors: pressure, temperature and nanocrystal size. They did not find that additional factors such as defects and strain had a significant effect as previously suggested. Based on this new information, they created a simple computer simulation that can predict the adsorption/desorption rates of various types and size ranges of nanocrystals with a variety of different gases.

"This makes it possible to optimize a wide range of nanocrystal applications, including hydrogen storage systems, catalytic converters, batteries, fuel cells and supercapacitors," Bardhan said.


Story Source:

The above story is based on materials provided by Vanderbilt University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Rizia Bardhan, Lester O. Hedges, Cary L. Pint, Ali Javey, Stephen Whitelam, Jeffrey J. Urban. Uncovering the intrinsic size dependence of hydriding phase transformations in nanocrystals. Nature Materials, 2013; DOI: 10.1038/nmat3716

Cite This Page:

Vanderbilt University. "Size matters in nanocrystals' ability to adsorb/release gases." ScienceDaily. ScienceDaily, 6 August 2013. <www.sciencedaily.com/releases/2013/08/130806171602.htm>.
Vanderbilt University. (2013, August 6). Size matters in nanocrystals' ability to adsorb/release gases. ScienceDaily. Retrieved November 23, 2014 from www.sciencedaily.com/releases/2013/08/130806171602.htm
Vanderbilt University. "Size matters in nanocrystals' ability to adsorb/release gases." ScienceDaily. www.sciencedaily.com/releases/2013/08/130806171602.htm (accessed November 23, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Sunday, November 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

AFP (Nov. 21, 2014) Toyota presented its hydrogen fuel-cell compact car called "Mirai" to US consumers at the Los Angeles auto show. The car should go on sale in 2015 for around $60.000. It combines stored hydrogen with oxygen to generate its own power. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
Google Announces Improvements To Balloon-Borne Wi-Fi Project

Google Announces Improvements To Balloon-Borne Wi-Fi Project

Newsy (Nov. 21, 2014) In a blog post, Google said its balloons have traveled 3 million kilometers since the start of Project Loon. Video provided by Newsy
Powered by NewsLook.com
Raw: Paralyzed Marine Walks With Robotic Braces

Raw: Paralyzed Marine Walks With Robotic Braces

AP (Nov. 21, 2014) Marine Corps officials say a special operations officer left paralyzed by a sniper's bullet in Afghanistan walked using robotic leg braces in a ceremony to award him a Bronze Star. (Nov. 21) Video provided by AP
Powered by NewsLook.com
British 'Bio-Bus' Is Powered By Human Waste

British 'Bio-Bus' Is Powered By Human Waste

Buzz60 (Nov. 21, 2014) British company GENeco debuted what its calling the Bio-Bus, a bus fueled entirely by biomethane gas produced from food scraps and sewage. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins