In Situ Ti-Embedded SiC as Chemiresistive Nanosensor for Safety Monitoring of CO, CO2, NO, NO2: Molecular Modelling by Conceptual Density Functional Theory

The adsorption of four CO, CO₂, NO, NO₂ gas molecules in the atmosphere on titanium (Ti)‑doped monolayer SiC surface was investigated using the density functional theory (DFT) with equilibrium geometries optimized at the CAM-B3LYP/6-311+G(d, p) level of theory. The thermochemical, electric and magnetic properties data recommend that the adsorption of these gas molecules on Ti-embedded SiC sheet (SiC_sh) monolayer is more energetically desired than that on the pristine ones. Gas molecules of CO, CO₂, NO, NO₂ have been adsorbed on the Ti site of doped SiC monolayer through the formation of covalent bonds. Moreover, after the adsorption, the orientations of the gas molecules exhibited a tendency to orient in the inclined and parallel forms to monolayer SiC_sh. The DFT analysis explored that the monolayer SiC_sh with C and Ti-doped atoms possessing one satisfied valency increased the Van der Waal interactions between the gas molecules and the monolayer SiC_sh. Furthermore, the assumption of chemical adsorptions has been approved by the projected density of states (PDOS) and charge density difference plots. Charge density difference calculations also indicate that the electronic densities were mainly accumulated on the adsorbate of CO, CO₂, NO, NO₂ gas molecules. The results in this investigation can indicate the competence of transition metal doped silicon carbide nanosheet in sensor devices. The overall analysis showed that the adsorption strength of monolayer SiC_sh towards the chosen gas molecules follows the order: NO₂ > CO₂ > NO > CO.