Publication Date:
2015-09-02
Description:
Nitric oxide NO is one of the major targets for environmental monitoring, but the existing NO sensors are limited by their low sensitivity and narrow test range. Here, a NO gas sensor employing multiwalled carbon nanotubes (MWCNTs) was fabricated, and its properties in NO–N 2 mixture were investigated from both emission and ionization. The current I e passing through the nanotubes cathode was found to decrease with increasing NO concentration and increase linearly in different slopes with the extracting voltage U e . It is shown that the Schottky barrier of the MWCNTs calculated by I e increased with NO concentration due to the adsorption of NO gas, which restrained the electron emission and consequently weakened the ionization. The positive ion currents I c passing through the collecting electrode at different voltages of U e were found to monotonically decrease with increasing NO concentration, which was induced by both of the reduced electron emission and the consumption of the two excited metastable states N 2 (A 3 ∑ u + ) and N 2 (a′ 1 ∑ u − ) by NO. The sensor exhibited high sensitivity at the low temperature of 30 °C. The calculated conductivity was found to be able to take place of I c for NO detection in a wide voltage range of 80–150 V U e .
Print ISSN:
0003-6951
Electronic ISSN:
1077-3118
Topics:
Physics
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