Adsorption of gas molecules on a manganese phthalocyanine molecular device and its possibility as a gas sensor

A theoretical investigation of the gas detection performance of manganese(ii) phthalocyanine (MnPc) molecular junctions for six different gases (NO, CO, O₂, CO₂, NO₂, and NH₃) is executed through a non-equilibrium Green's function technique in combination with spin density functional theory. Herein, we systematically studied the adsorption structural configurations, the adsorption energy, the charge transfer, and the spin transport properties of the MnPc molecular junctions with these gas adsorbates. Remarkably, NO adsorption can achieve an off-state of the Mn spin; this may be an effective measure to switch the molecular spin. In addition, our results indicate that by measuring spin filter efficiency and the changes in total current through the molecular junctions, the CO, NO, O₂, and NO₂ gas molecules can be detected selectively. However, the CO₂ and NH₃ gas adsorptions are difficult to be detected due to weak van der Waals interaction between these two gases and central Mn atom. Our findings provide important clues to the application of nanosensors for highly sensitive and selective based on MnPc molecular junction systems.