Gas selectivity enhancement by sampling-and-hold method in resistive gas sensors

Commercial resistive gas sensors exhibit various sensitivity to numerous gases when working at different elevated temperatures. That effect is due to a change in velocity of adsorption and desorption processes which can be modulated by temperature. Thus, to reach better selectivity of gas detection, we propose to apply a known method (called the sampling-and-hold method) of cooling down the gas sensor in the presence of the investigated gas, and the fluctuation enhanced sensing. The adsorbed gas molecules were captured in the porous gas sensing layer and then slowly released by heating up. We observed a significant (greater than one order) change of the normalized low-frequency resistance noise during the process of slow heating up. That change was characteristic for different investigated gases. Moreover, the resistance noise reached its minimum at the temperature characteristic for the adsorbed gas. This effect can be explained by differences in the activation energy of the adsorbed gas molecules. The observed results are very promising for improving gas detection by determining the position of minimal noise intensity and can be utilized in practice. (C) 2015 Elsevier B.V. All rights reserved.