Possibility of Gas Sensor Using Electronic Transport Properties of Iron−Porphyrin Molecular Junction System

The possibility of sensing gases by making use of the transport properties of the junction system composed of the thiolated iron−porphyrin molecule has been theoretically investigated. It is found that the molecular orbitals which are derived from the Fe-3d3z2−r2 orbital are the most relevant to the transmission around the Fermi energy. The adsorption of diatomic ligand gases significantly modifies these conductive molecular orbitals, leading to noticeable changes in the transmission spectra of the junction system. We suggest that the adsorption of diatomic ligand gases such as CO, NO, and O2 may be detected selectively by measuring the changes in electric current through the molecular junction system.