Apr 12, 2012
Nanoclusters tailor the response of nanowire-based gas sensors
Previously, researchers have shown that gallium nitride nanowires decorated with nanoclusters of titanium dioxide can be used to detect volatile organic compounds, such as benzene, toluene, ethylbenzene, and xylene – commonly referred to as BTEX. What’s more, these sensors operate at room temperature, and require only low-power ultraviolet light. Now, the team from the University of Maryland, the National Institute of Standards and Technology, and George Mason University has found that by adding platinum to the titanium dioxide nanoclusters, the same sensors can be “retuned” to respond to hydrogen, methanol, and ethanol. Following the modification, the devices become insensitive to the abovementioned aromatic compounds.
Reporting their results in the journal Nanotechnology, the scientists have demonstrated sensing of ethanol and methanol concentrations as low as 100 parts per billion in air with a response time of approximately 100 s, and hydrogen concentrations from 1 parts per million to 1% in nitrogen with a response time less than 60 s. In comparison, it is difficult for humans to smell methanol in the air at less than 2000 parts per million concentration.
Commercial multi-analyte monitoring devices often use multiple sensors, each designed for a specific set of chemicals. Such monitors are often used by industrial workers and first responders. To be effective, the units need to be small and should be able to identify different chemicals at very low concentrations, without consuming too much power.
The team's approach could lead to the development of multi-analyte sensors on a single chip, which can be integrated with smart phones. As these sensors are made from wide band gap materials and stable metal-oxides, the devices should be able to withstand harsh environmental conditions encountered in battlefields, industrial plants and other challenging situations.
The hybrid nanowire-nanocluster sensors are fabricated using standard microfabrication steps. Photolithography and metal deposition were used to make two-terminal devices. Nanoclusters of titanium dioxide and platinum, respectively, were then sputter-deposited on these nanowire devices.
Building on these results, the team is now designing nanoclusters targeting analyte groups such as NOx, SOx, and other industrial and environmental pollutants. They are also working on developing sensors with high sensitivity to trace explosives. The group’s ultimate goal is to develop techniques that allow these sensors to be manufactured on a commercial scale.
Further information can be found in the journal Nanotechnology.
About the author
Geetha S Aluri is a PhD student at George Mason University, advised by Dr M V Rao. Dr Abhishek Motayed is a research scientist at University of Maryland, College Park, and the principle investigator for this project. Dr Albert V Davydov, Dr Vladimir P Oleshko, Dr Norman A Sanford, and Dr Kris A Bertness are scientists with the National Institute of Standard and Technology.