Selective Detection of NO and NO₂ with CNTs-Based Ionization Sensor Array

The accurate detection of NO_x is an important issue, because nitrogen oxides are not only environmental pollutants, but also harm to human health. An array composed of two carbon nanotubes (CNTs)-based ionization sensors with different separations is proposed for NO and NO₂ selective detection. The experimental results indicate that the CNTs-based ionization sensor has an intrinsic, monotonically decreasing response to NO or NO₂. The sensor with 80 µm separations and 100 µm separations exhibited the highest sensitivity of -0.11 nA/ppm to 300 ppm NO and -0.49 nA /ppm to 70 ppm NO₂, respectively. Although the effect of the NO₂ concentration on the NO response is much stronger than that of NO on NO₂, the array of these two sensors still exhibits the ability to simultaneously detect the concentrations of NO and NO₂ in a gas mixture without component separation.