| AVS 54th International Symposium | |
| Nanometer-scale Science and Technology | Thursday Sessions |
| Session NS-ThA |
| Session: | Nanoscale Sensors |
| Presenter: | C. Berven, University of Idaho |
| Authors: | C. Berven, University of Idaho S. Chava, University of Idaho A. Heieren, University of Idaho R. Abdelrahaman, University of Idaho D. McIlroy, University of Idaho M.G. Norton, Washington State University |
| Correspondent: | Click to Email |
We report on the use of macroscopic mats of gold-nanoparticle-decorated GaN nanowires for the detection of CO2 and the possible generation of CO2 along with H2 by interactions of CO and H2O on the surfaces of the gold nanoparticles. The sensor consisted of a mat of GaN nanowires grown on a sapphire substrate (d ~ 1 cm) using a vapor-liquid-solid growth technique.1 The mat was ~ 20 µm thick and the nanowire diameters and lengths were ~ 200 nm and ~ 5 µm, respectively. The nanowires were decorated with gold nanoparticles using a chemical vapor deposition process resulting in a continuous layer.2 The gold was reduced by selective wet etching to create a sparse coverage of nanoparticles. Current-voltage (I-V) measurements were performed when exposed to vacuum, CO, CO2 and water vapor. All measurements were performed at 300 K and in the dark at pressures of 50 Torr to 1 atm with a maximum vacuum of 5 mTorr. When exposed to just water vapor or CO the currents were only attenuated slightly from the vacuum state. When exposed to CO2, the current was attenuated to a much larger degree. We have previously published data and a model to explain the sensitivity of similar device to methane3 which was due to the nanowires acting like Chem-FETs and where the selectivity was attributed to the morphology of the nanoparticles. When the device was exposed to CO followed by H2O, we saw significant reduction in the current, similar to that of just CO2 implying that what is being sensed is CO2 that was the by-product of the reaction of CO + H2O occurring on the gold nanoparticles. This is not unreasonable since nanoparticle gold is known to be quite reactive.4 As a consequence of CO2 being detected after the mixing of CO and H2O on the nanoparticles, we speculate that H2 is also being generated giving a possible new mechanism for H2 generation for fuel cells.
1V. Dobrokhotov, C. Berven et al., J. Appl. Phys. 99, 104302 (2006)
2A. D. LaLonde, et al., J. Mater. Res. 20, 549 (2005)
3 V. V. Dobrokhotov, C. Berven et al., Nanotechnology 17, 4135-4142 (2006)
4 M. Haruta, Applied Catalysis A: General 222, 427 (2001) .