Zn-Porphyrin Nanoring as a CO Gas Sensor: A Fast Response and Short Recovery Time Sensor

The butadiyne-linked four-metalloporphyrin nanoring (Zn4P4) is a promising candidate in future nanoelectronic applications such as nanosensors for small gas molecules. The aim of this work is to analyze the CO gas sensing capacity of Zn4P4 using Density Functional Theory (DFT) calculations at CAM-B3LYP/6-31G (d,p) level of theory. To predict the gas adsorption properties of the Zn4P4 system the geometrical structures, binding energies, band gaps, the Density of States (DOS), adsorption energies (𝐸𝑎𝑑𝑠𝐵𝑆𝑆𝐸), HOMO and LUMO energies, Fermi level energies (EFL), Natural Bond Orbital (NBO), and Frontier Molecular Orbital (FMO) were calculated. Here it should be remarked that the adsorption of CO gas molecule on Zn4P4 nanoring from the outer side is higher than the inner side. Moreover, the adsorption from the Carbon site of the CO gas molecule is stronger than from the Oxygen site. Also, the closest distance of CO with the Zn4P4 molecule is in the range of 2.505-2.706A˚. Moreover, the range of 𝐸𝑎𝑑𝑠𝐵𝑆𝑆𝐸 values was from -6.50 to -9.40 kCal/mol. The results revealed that during the adsorption of CO gas molecule on Zn4P4 the amounts of Eg and consequently, σ have been considerably changed. Based on the calculated 𝐸𝑎𝑑𝑠𝐵𝑆𝑆𝐸and a notable decrease in the Eg, it is expected that the Zn4P4 is sensitive to CO molecules. Amazingly, the Zn4P4-CO records favorable values of recovery times for different attempt frequencies. Therefore, the results open a way for the development of a new and selective CO nanosensor.