Different Interaction Mechanisms of Evaporated Porphyrin Films Exposed to NO 2
In this work, metal free and zinc tetraphenylporphyrin films were 
employed as nitrogen dioxide (NO2) gas 
sensors. The films were vacuum evaporated and the sensor response was evaluated 
as changes in the optical absorption spectra, hydrophobic properties and 
conductivity at different gas concentrations. From UV-Vis results, 
important changes in the absorption peaks were observed after gas exposure. The 
morphology of the films before and after gas interaction was obtained by using 
scanning electron and atomic force microscopy. The films morphology showed a 
degradation after gas adsorption for the metal free system but gas entrapment 
for the zinc porphyrin film. In order to elucidate the gas adsorption 
phenomena, density functional theory calculations were also performed. Here, it 
was observed that the porphyrin chemical structure not only affects the gas coordination 
sites which affect the porphyrin electronic distribution and packing 
arrangement, but also, determines the gas detection mechanism for sensing 
applications.