Abstract
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.
Highlights
Nowadays, most of the current commercially available detectors of volatile organic compounds (VOC) have been fabricated by using metal oxide semiconductors, and they employ detection techniques such as photoionization, electrochemistry and non-dispersive infrared and thermal methods, which require several detection steps, expensive materials and complex signal generators [1]
Previous results suggested that porphyrin films exposed to NO2 can recover over time or by exposing the films to elevated temperatures [10], from microscopy images, we showed important differences in the film integrity after gas exposure
Metal-free and zinc tetraphenyl porphyrin films were employed as gas NO2 gas sensors
Summary
Most of the current commercially available detectors of volatile organic compounds (VOC) have been fabricated by using metal oxide semiconductors, and they employ detection techniques such as photoionization, electrochemistry and non-dispersive infrared and thermal methods, which require several detection steps, expensive materials and complex signal generators [1]. More work has been devoted to investigate the role of organic films as promising detector materials. Changes in the color and the electrical conductivity of these films after specific gas interactions have suggested that these systems represent a reliable and economical method to produce portable gas sensor devices [2]
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