Adsorption-desorption characteristics of explosive vapors investigated with microcantilevers

Understanding the kinetics of adsorption and desorption of explosive vapors such as TNT from surfaces is important in the design of sensors. We report for the first time, the adsorption-desorption characteristics of TNT from a Si-microcantilever exposed to vapors of TNT. It was observed that TNT readily sticks to the exposed Si surface with the adsorption kinetics showing an initial exponential behavior followed by roughly linear kinetics. It was also observed that for cantilever temperatures close to room temperature, TNT desorbs spontaneously from the surface with decaying exponential kinetics. Based on the known equilibrium partial vapor pressures of TNT, the "effective" sticking coefficient for the silicon oxide surface at room temperature under the experimental conditions was calculated to be about 0.02. This information can be very useful in the design of sensors and that of vapor-delivery systems.