KINETIC-BEHAVIOR ANALYSIS OF PORPHYRIN LANGMUIR-BLODGETT-FILMS FOR CONDUCTIVE GAS SENSORS

Meso, meso'-buta-1,3-diyne-bridged Ni (LI) octaethylporphyrin dimer th in 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 fil ms undergo a remarkable variation due to exposure to small concentrati ons of NO in air at an operating temperature of 50 degrees C. To inter pret the behavior of such organic films, a model has been built up and the conductivity variation as a function of test gas concentrations a nd time has been derived. The fitting of theoretical and experimental behavior allows us to determine the number of adsorbed gas molecules p er porphyrin dimer, response and recovery,times, adsorption and desorp tion coefficients. The reliability of the model is proved by obtained results. In particular, the determined adsorption and desorption coeff icients depend only on test gas species but are unaffected by other ex perimental conditions such as gas concentration.