The surface reaction and diffusion of NO2 in lead phthalocyanine thin film

The responses of lead phthalocyanine thin films upon encountering of NO2 ga s were studied both experimentally and theoretically. A surface adsorption/ desorption and bulk diffusion mechanism was proposed to describe the respon se. Laplace transform was employed to solve the resulting diffusion equatio n and an analytical solution was obtained. The analytical results show that the steady state current depends on parameters such as film thickness, gas diffusivity, adsorption and desorption rate constants, etc. Diffusivity, a dsorption and desorption rate constants can be extracted from the nonlinear least square fitting of experimental data with analytical results. The obt ained gas diffusivity, which depends on film morphology, remains fairly con stant as film thickness changes. From the results of this study, it was con cluded that the adsorption of NO2 by lead phthalocyanine is controlled by t he surface adsorption and desorption with negligible diffusion resistance. (C) 1999 Elsevier Science S.A. All rights reserved.