The gas sensing performances of gas sensors based on the dielectrophoretically manipulated multi-wall carbon nanotubes with various functionalized groups towards NH3

Abstract

Gas sensors based on pristine multi-wall carbon nanotubes (MWNTs) and functionalized multi-wall carbon nanotubes (MWNTs-x, x: NH2, OH, COOH) were fabricated on the chromium-silver-gold microelectrode chips by dielectrop- horesis process. The dielectric response behavior of MWNTs and MWNTs-x were investigated. The electrophoresis parameters of 2 MHz and 8 V were determined as the fabrication condition of MWNTs gas sensors. The particles of MWNTs and MWNTs-x were captured to the electrode tip under the dielectrophoretic force, which was the positive dielectrophoresis (p-DEP). The gas sensing performances of the fabricated gas sensors towards different concentra- tions of SO2 were tested at room temperature. It was found that the response time, recovery time and sensitivity of gas sensors towards SO2 were increased with the increase of SO2 concentrations. The functionalized MWNTs gas sensors showed remarkably higher sensitivity than pristine MWNTs gas sensors. The sensitivity of the aminoated MWNTs (MWNTs-NH2) gas sensors was the highest and 17-23 times higher than that of pristineMWNTs. We conclude that the interactions between carbon tubes and SO2 such as capillary forces, surface tensions, hydrogen bonding and chemical bonds are influential factors for the gas sensing performances of these gas sensors.