Room Temperature Gas Sensor Application of Carbon Nanowalls using Electrical Resistance Change by Surface Adsorption of Toxic Gases

Abstract

Carbon is not only a readily available material, but also has appropriate properties through various structural modifications. Carbon nanowalls (CNWs), based on carbon with vertical porous nanostructure, offer broad sensing surface area. Using carbon nanowalls, we demonstrated it function as gas sensing layer in our work. Carbon nanowalls synthesized via plasma enhanced chemical vapor deposition (PECVD) was in form numerous nanoflakes. In addition, various defect on its surface with high D band and low G band in Raman spectra was observed. When ammonia (NH3) and nitrogen dioxide (NO2) that may cause environmental pollution as an analyte gas were adsorbed on carbon nanowalls during exposing to them, difference in electrical resistance over 300 percentage between ammonia and nitrogen dioxide appeared. In various characteristics such as response time, sensitivity, saturation-recovery and selectivity, carbon nanowalls-based gas sensor exhibited better performance in nitrogen dioxide than ammonia. The reason for these performance is that the charge transfer of nitrogen dioxide greater than that of ammonia. In addition, the electron affinities of ammonia and nitrogen dioxide are 0.55 ± 0.10 and 2.11 ± 0.18 eV, respectively, which may sufficiently affect the each reaction between two analyte gases. Through this work, we offer several results of the proof-of-concept study for the gas sensor application of carbon nanowalls.