Kinetic behavior analysis of porphyrin Langmuir-Blodgett films for conductive gas sensors

Meso, meso-buta-1,3-diyne-bridged Ni (II) octaethylporphyrin dimer thin films have been deposited by the Langmuir–Blodgett method and, for the first time, have been considered as the active layer in resistive gas sensors. In particular, the electrical conductivities of these films undergo a remarkable variation due to exposure to small concentrations of NO in air at an operating temperature of 50 degrees Celsius. To interpret the behavior of such organic films, a model has been built up and the conductivity variation as a function of test gas concentrations and time has been derived. The fitting of theoretical and experimental behavior allows us to determine the number of adsorbed gas molecules per porphyrin dimer, response and recovery times, adsorption and desorption coefficients. The reliability of the model is proved by obtained results. In particular, the determined adsorption and desorption coefficients depend only on test gas species but are unaffected by other experimental conditions such as gas concentration.