Featured Research

from universities, journals, and other organizations

Titania Nanotube Hydrogen Sensors Clean Themselves

Date:
March 29, 2004
Source:
Penn State
Summary:
Self-cleaning hydrogen sensors may soon join the ranks of self-cleaning ovens, self-cleaning windows and self-cleaning public toilets, according to Penn State researchers.

FESEM images of the titania nanotube array prepared using an anodization potential of 10 V, top view.
Credit: Image courtesy Penn State

Self-cleaning hydrogen sensors may soon join the ranks of self-cleaning ovens, self-cleaning windows and self-cleaning public toilets, according to Penn State researchers.

"The photocatalytic properties of titania nanotubes are so large -- a factor of 100 times greater than any other form of titania -- that sensor contaminants are efficiently removed with exposure to ultraviolet light, so that the sensors effectively recover or retain their original hydrogen sensitivity in real world application," says Dr. Craig A. Grimes, associate professor of electrical engineering and materials science and engineering.

Previous research showed that titania nanotubes at room temperature have a completely reversible electrical resistance change of about 100,000,000 percent when exposed to 1000 parts per million of hydrogen. These nanotube sensors can monitor hydrogen levels from parts per billion to about 4 percent, the explosive limit.

Hydrogen sensors are widely used in the chemical, petroleum and semiconductor industries. They are also used as diagnostic tools to monitor certain types of bacterial infections.

"In a bakery, for example, sensors sniff hydrogen and measure temperature to determine when goods are done," says Grimes. "Hydrogen sensors are also used in combustion systems of automobiles to monitor pollution."

However, the environments where people use hydrogen sensors, such as petroleum plants, can get very dirty. In addition to Grimes, the researchers include: Gopal K. Mor and Oomman K. Varghese, postdoctoral fellows; Michael V. Pishko, associate professor of chemical engineering, and Maria A. Carvalho, graduate student in chemical engineering, investigated the photocatalytic oxidation of contaminants on the hydrogen sensors. They reported their results in recent issues of the Journal of Materials Research and Sensor Letters.

The hydrogen sensors are titania nanotubes coated with a discontinuous layer of palladium. The researchers tried to contaminate the sensors with a variety of substances including stearic acid – a fatty acid, cigarette smoke and different types of oil. While all these contaminants were self-cleanable via photocatalytic properties of the nanotubes, most experiments focused on recovery of the sensor after immersion in different types of motor oils, viewed as the ultimate contamination by the investigators.

The researchers exposed the hydrogen sensors to 1000 parts per million of hydrogen, at room temperature, finding in their initial sensor designs a 175,000 percent change in resistance. The sensors were then coated with a layer of motor oil several tens of microns thick, that completely extinguished their hydrogen sensitivities.

In an air atmosphere, the researchers exposed the sensor to ultraviolet light for 10 hours. After one hour, the sensors had recovered a large portion of their sensitivity, and after 10 hours the sensors, compared to their uncontaminated selves, had almost fully regained their hydrogen sensitivities.

"The recovered sensor has a 1000 part per million hydrogen normalized resistance value of approximately .0005 percent, compared with the .0006 percent value of the sensor prior to contamination," says Grimes.

The sensors could not recover from all contaminants, for example a coating of the spray-on oil WD-40, as these contaminants contain salts, which degrade the photocatalytic properties of the nanotubes.

"By doping the titania nanotubes with trace amounts of different metals such as tin, gold, silver, copper, niobium and others, a wide variety of chemical sensors can be made," says Grimes. "This doping does not alter the photocatalytic properties of the titania nanotubes."

Sensors in uncontrolled locations – in the real world – become contaminated by a variety of substances including volatile organic vapors, carbon soot and oil vapors as well as dust and pollen. A self-cleaning function, capable of oxidizing contaminants, would extend sensor lifetime and minimize sensor errors.


Story Source:

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


Cite This Page:

Penn State. "Titania Nanotube Hydrogen Sensors Clean Themselves." ScienceDaily. ScienceDaily, 29 March 2004. <www.sciencedaily.com/releases/2004/03/040325073047.htm>.
Penn State. (2004, March 29). Titania Nanotube Hydrogen Sensors Clean Themselves. ScienceDaily. Retrieved September 23, 2014 from www.sciencedaily.com/releases/2004/03/040325073047.htm
Penn State. "Titania Nanotube Hydrogen Sensors Clean Themselves." ScienceDaily. www.sciencedaily.com/releases/2004/03/040325073047.htm (accessed September 23, 2014).

Share This



More Matter & Energy News

Tuesday, September 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Will Living Glue Be A Thing?

Will Living Glue Be A Thing?

Newsy (Sep. 23, 2014) Using proteins derived from mussels, engineers at MIT have made a supersticky underwater adhesive. They're now looking to make "living glue." Video provided by Newsy
Powered by NewsLook.com
Company Copies Keys From Photos

Company Copies Keys From Photos

Newsy (Sep. 22, 2014) A new company allows customers to make copies of keys by simply uploading a couple of photos. But could it also be great for thieves? Video provided by Newsy
Powered by NewsLook.com
The Hyped-Up Big Bang Discovery Has A Dust Problem

The Hyped-Up Big Bang Discovery Has A Dust Problem

Newsy (Sep. 22, 2014) An analysis of new satellite data casts serious doubt on a previous study about the Big Bang that was once hailed as revolutionary. Video provided by Newsy
Powered by NewsLook.com
Rockefeller Oil Heirs Switching To Clean Energy

Rockefeller Oil Heirs Switching To Clean Energy

Newsy (Sep. 22, 2014) The Rockefellers — heirs to an oil fortune that made the family name a symbol of American wealth — are switching from fossil fuels to clean energy. Video provided by Newsy
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