Adsorption of the NO2, N2O and NH3 molecules over the C20 and MC19 (M = Ru, Ir and Au) clusters: A DFT approach

Abstract In this work, we used the DFT calculations with the B3LYP functional to evaluate the adsorption of the NO2, N2O and NH3 molecules over the surface of the C20 and MC19 (M = Ru, Ir and Au) clusters. The results reveal that the N2O and NH3 molecules are physically adsorbed onto the C20 surface, while the NO2 molecule was strongly chemisorbed with an adsorption energy equal to - 45.0 kcal mol−1. The change in Eg of C20 nanocage after adsorption process is very small, indicating a low sensitivity of C20 to the above molecules. When a carbon atom is replaced by a metal (Ru, Ir or Au) atom, the relative stability of RuC19 and AuC19 clusters was improved, and in turn the stability of the IrC19 cluster was decreased, thereby its activity was sharply enhanced in comparison with that of C20 fullerene. It was found that the interaction of NO2 molecule with the metal-doped C20 clusters is very strong, implying a great chemisorption process. The results show also that the interaction of the N2O molecule over the surface of the IrC19 cluster leads to the dissociation of the N2O molecule into O* and N2 with an adsorption energy of - 49.4 kcal mol−1. This suggests that this cluster could be employed as an active and efficient nanocatalyst for the N2O decomposition reaction. In contrast, the N2O was associatively adsorbed on the AuC19 cluster with Eads less than - 10 kcal mol−1, indicating a physical adsorption. Large variation in Eg was observed for the AuC19 cluster upon their interaction with the NO2, N2O and NH3 molecules, which leads to a significant increase in its electrical conductivity. So, the AuC19 cluster has a great electronic sensitivity toward the above molecules, reflecting that this cluster could be described as a promising nanosensor for the detection of the N2O, NO2 and NH3 molecules. Moreover, in this study, the NLO properties of the clusters and their formed complexes by interaction with the above molecules were calculated and discussed. The solvent effect (water) onto the electronic and adsorption properties of the formed complexes has also been examined in depth.