Abstract
Abstract Active layers for detecting NO 2 have been obtained by adding a low amount of oxygen-functionalized MWCNTs to three different types of metal oxides (SnO 2 , WO 3 or TiO 2 ). We show that the responsiveness towards NO 2 of micro-sensors based on some of the resulting metal oxide/MWCNT hybrid films is considerably improved. In particular, the sensors based on hybrid SnO 2 /MWCNTs films present excellent sensitivity towards NO 2 when operated at room temperature. Additionally, the sensors show a total recovery of their baseline resistance and reasonable response and recovery times. A mechanism of response based on the development of two depletion layers, one at the surface of metal oxide grains and another at the interface of the n-metal oxide/p-MWCNT hetero-structure, is postulated as responsible for the improvement observed. Our results suggest that there should be an optimum amount of carbon nanotubes to be added to each specific metal oxide in order to enhance sensitivity.
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