11-06/07 :: June/July 2011

nanotimes News in Brief

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in the air, but fail to sniff out a massive release of the gas. The range of the new nanowire sensors runs from just 50 parts per billion up to 1 part per 100, or 1 percent of the air in a room. These new sensors, built using the same fabrication processes that are commonly used for silicon computer chips, operate using the same basic principle, but on a much smal- ler scale: the gallium nitride wires are less than 500 nanometers across and less than 10 micrometers in length. Despite their microscopic size, the nanowires and titanium dioxide nanoclusters they‘re coated with have a high surface-to-volume ratio that makes them exquisitely sensitive.

“The electrical current flowing through our nano- sensors is in the microamps range, while traditional sensors require milliamps,” explains NIST‘s Abhishek Motayed. “So we‘re sensing with a lot less power and energy. The nanosensors also offer greater reliability and smaller size. They‘re so small that you can put them anywhere.” Ultraviolet light, rather than heat, promotes the titanium dioxide to react in the pre- sence of a volatile organic compound.

Further, each nanowire is a defect-free single crystal, rather than the conglomeration of crystal grains in thin-film sensors, so they‘re less prone to degrada-

tion. In reliability tests over the last year, the nano- sized sensors have not experienced failures. While the team‘s current experimental sensors are tuned to detect benzene as well as the similar volatile orga- nic compounds toluene, ethylbenzene and xylene, their goal is to build a device that includes an array of nanowires and various metal oxide nanoclusters for analyzing mixtures of compounds. They plan to collaborate with other NIST teams to combine their ultraviolet light approach with heat-induced nano- wire sensing technologies.

The portion of this work conducted at George Ma- son University was funded by the National Science Foundation.

G.S. Aluri, A. Motayed, A.V. Davydov, V.P. Oleshko, K.A. Bertness, N.A. Sanford and M.V. Rao: Highly selective GaN-nanowire/TiO2

-nanocluster hybrid sensors for de-

tection of benzene and related environment pollutants, In: Nanotechnology, Vol. 22, Number 29, July 22, 2011, Article 295503, DOI: 10.1088/0957-4484/22/29/295503: http://dx.doi.org/10.1088/0957-4484/22/29/295503