Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > New hydrogen sensor faster, more sensitive

Abstract:
Coating used dramatically enhances the sensitivity and reaction time of hydrogen sensors

New hydrogen sensor faster, more sensitive

Argonne, ILL | June 01, 2005

The same kind of chemical coating used to shed rainwater from aircraft and automobile windows also dramatically enhances the sensitivity and reaction time of hydrogen sensors. Hydrogen sensor technology is a critical component for safety and other practical concerns in the proposed hydrogen economy. For example, hydrogen sensors will detect leaks from hydrogen-powered cars and fueling stations long before the gas becomes an explosive hazard.

The discovery was made by a team led by Zhili Xiao, a physicist in the Materials Science Division at the U.S. Department of Energy's Argonne National Laboratory and an associate professor of physics at Northern Illinois University. The scientists demonstrated that the enhanced sensor design shows a rapid and reversible response to hydrogen gas that is repeatable over hundreds of cycles. A report on the team's research was published in May in Applied Physics Letters.

The sensor material is made by depositing a discontinuous palladium thin film on a glass slide coated with a grease-like self-assembled monolayer of siloxane anchored to the surface.

“By adding the siloxane self-assembled monolayer, we have changed the thin film dynamics,” said Michael Zach, a chemist and holder of the Glenn Seaborg Postdoctoral Fellowship at Argonne. “Other sensors have a response time of several seconds upon exposure to 2 percent hydrogen; ours works in tens of milliseconds.” Also, the scientists reported that the enhanced sensors are sensitive enough to detect hydrogen levels as low as 25 parts per million (ppm), far below hydrogen's lower explosive limit around 40,000 ppm. Their sensitivity and speed are superior to any available commercial sensors.

Palladium is an ideal material for hydrogen sensing because it selectively absorbs hydrogen gas and forms a chemical species known as a palladium hydride. Thick-film hydrogen sensor designs rely on the fact that palladium metal hydride's electrical resistance is greater than the metal's resistance. In such systems, the absorption of hydrogen is accompanied by a measurable increase in electrical resistance.

However, a palladium thin-film sensor is based on an opposing property that depends on the nanoscale structures within the thin film. In the thin film, nanosized palladium particles swell when the hydride is formed, and in the process of expanding, some of them form new electrical connections with their neighbors. The increased number of conducting pathways results in an overall net decrease in resistance.

Palladium is good at “wetting” bare glass surfaces – it spreads across the glass in puddle-like clusters a few nanometers thick and tens of nanometers across. After pre-coating the glass with the siloxane monolayer, the Argonne scientists saw a remarkable shift in the size and spatial distribution of the palladium. Like water beading on the surface of a freshly waxed car, the palladium formed granular clusters just a few nanometers across. The gaps between neighboring palladium clusters on the siloxane-coated glass were more numerous and ten times smaller on average than the gaps between the much larger, spread-out clusters on the bare glass.

“The shorter gap distance is important for giving you a fast, sensitive response,” said Tao Xu, a chemist and the first inventor of the submitted patent application on fast hydrogen sensors. Even a slight swelling of the clusters produces many more new electrical contacts between neighbors and links together many new pathways for an electrical current to travel.

The scientists also have evidence that the surface treatment of the glass reduces the adhesion – or “stiction” – between the metal and glass that hinders the expansion and contraction of the palladium nanoparticles on bare glass. This effect contributes to the increased speed of the sensor response.

The scientists spent nearly a year optimizing the procedure to make the palladium films on coated glass, and they developed a new test system that could inject hydrogen quickly enough to test the sensors on a millisecond time scale. They say their approach to making sensors is easily scalable to an industrial level. “We are using techniques that the semiconductor industry already uses,” Zach said.

The sensor will be affordable too. Although palladium is an expensive precious metal, Zach estimated that the amount in each sensor is so small that the metal cost is less than a penny.

Several outstanding questions include whether the sensors can be made to withstand poisonous contaminants in the air and whether the sensors will stand up to long-term operation. Wai-Kwong Kwok, leader of the Superconductivity and Magnetism group in the Materials Science Division, expressed confidence that these issues can be handled on an engineering level. The sensors are being developed for commercial use by an industrial partner in collaboration with Argonne.

####

About Argonne National Laboratory:
The nation's first national laboratory, Argonne National Laboratory conducts basic and applied scientific research across a wide spectrum of disciplines, ranging from high-energy physics to climatology and biotechnology. Since 1990, Argonne has worked with more than 600 companies and numerous federal agencies and other organizations to help advance America's scientific leadership and prepare the nation for the future. Argonne is operated by the University of Chicago for the U.S. Department of Energy's Office of Science.

For more information, visit www.anl.gov

Contact:
Catherine Foster
(630/252-5580
cfoster@anl.gov

Copyright © Argonne National Laboratory

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

Sensors

Shape matters when light meets atom: Mapping the interaction of a single atom with a single photon may inform design of quantum devices December 4th, 2016

Deep insights from surface reactions: Researchers use Stampede supercomputer to study new chemical sensing methods, desalination and bacterial energy production December 2nd, 2016

Tip-assisted chemistry enables chemical reactions at femtoliter scale November 16th, 2016

'Back to the Future' inspires solar nanotech-powered clothing November 15th, 2016

Materials/Metamaterials

Physicists decipher electronic properties of materials in work that may change transistors December 6th, 2016

Infrared instrumentation leader secures exclusive use of Vantablack coating December 5th, 2016

Construction of practical quantum computers radically simplified: Scientists invent ground-breaking new method that puts quantum computers within reach December 5th, 2016

Inside tiny tubes, water turns solid when it should be boiling: MIT researchers discover astonishing behavior of water confined in carbon nanotubes November 30th, 2016

Announcements

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D: Up-close, real-time, chemical-sensitive 3-D imaging offers clues for reducing cost/improving performance of catalysts for fuel-cell-powered vehicles and other applications December 8th, 2016

Exotic insulator may hold clue to key mystery of modern physics: Johns Hopkins-led research shows material living between classical and quantum worlds December 8th, 2016

Arrowhead Pharmaceuticals to Webcast Fiscal 2016 Year End Results December 7th, 2016

Journal Nanotechnology Progress International (JONPI), newest edition out December 7th, 2016

Environment

Semiconductor-free microelectronics are now possible, thanks to metamaterials November 9th, 2016

First time physicists observed and quantified tiny nanoparticle crossing lipid membrane November 7th, 2016

Nanosensors on the alert for terrorist threats: Scientists interested in the prospects of gas sensors based on binary metal oxide nanocomposites November 5th, 2016

Marsden minds: Amazing projects revealed November 3rd, 2016

Energy

Research Study: MetaSOLTM Shatters Solar Panel Efficiency Forecasts with Innovative New Coating: Coating Provides 1.2 Percent Absolute Enhancement to Triple Junction Solar Cells December 2nd, 2016

Deep insights from surface reactions: Researchers use Stampede supercomputer to study new chemical sensing methods, desalination and bacterial energy production December 2nd, 2016

Throwing new light on printed organic solar cells December 1st, 2016

Physics, photosynthesis and solar cells: Researchers combine quantum physics and photosynthesis to make discovery that could lead to highly efficient, green solar cells November 30th, 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