Molecular modeling of Si60 fullerene and Nb-doped Si60 fullerene nanomaterials for SO2, NO2 and CO2 gas sensing

Abstract

CO2, NO2 and SO2 are by-products from the petrochemical industries that have been associated with both global warming and several respiratory dysfunctions. Hence, several efforts are being put forth to detect their excesses at minimal concentrations. In this regard, this study presents a theoretical analysis based on quantum and molecular mechanical calculations of the sensing efficacy of silicon nanostructures towards the effective detection of these gases at low concentrations. To enhance the attributes of the nanomaterial, transition metal (Nb) was endohedrally doped on the silicon Si60 nanomaterial to enhance the surface conductivity and sensitivity. The results indicate that the metal-doped nanostructures have improved sensitivity towards the studied gases. The adsorption of NO2, SO2 and CO2 followed a declining trend; NO2@NbdopSi59 > SO2@NbdopSi59 > CO2@NbdopSi59 > NO2@Si60 > SO2@Si60 > CO2@Si60 respectively. The computed adsorption enthalpies were found to be −25.36, −136.26 and −183.67 kcal/mol respectively for CO2@NbdopSi59, NO2@NbdopSi59 and SO2@NbdopSi59 systems. Comparatively, SO2 and NO2 preferred to be adsorbed on Si60 than CO2. The results of other electronic properties such as energy gap and conductivity were also found to be in tandem with the adsorption and stability studies. The sensing mechanism and computed desorption times were also found to be within 1.02 s to 2.72 s, clearly indicating a quick desorption from the metal-doped surface. Contrary, desorption from the pristine nanocluster was found to be slower due to strong chemisorption bonds between the gases and surface. While the electronic properties affirmed the conducting and stable nature of the surfaces, molecular dynamics simulation was further employed for stability evaluation. These results also unveiled the stable nature of the nanocluster and confirmed that the studied metal-doped nanoclusters possess the ideal properties to be employed as sensors for SO2 NO2 and CO2 gases.