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Theoretical calculations based on the Density Functional Theory (DFT) have been performed to investigate the interaction of H 2 S as well SO 2 gaseous molecules at the surfaces of Be 12 O 12 and Mg 12 O 12 nano-cages. The results show that a Mg 12 O 12 nano-cage is a better sorbent than a Be 12 O 12 nano-cage for the considered gases. Moreover, the ability of SO 2 gas to be adsorbed is higher than that of H 2 S gas. The HOMO-LUMO gap (E g ) of Be 12 O 12 nano-cage is more sensitive to SO 2 than H 2 S adsorption, while the E g value of Mg 12 O 12 nano-cage reveals higher sensitivity to H 2 S than SO 2 adsorption. The molecular dynamic calculations show that the H 2 S molecule cannot be retained at the surface of a Be 12 O 12 nano-cage within 300-700 K and cannot be retained on a Mg 12 O 12 nano-cage at 700 K, while the SO 2 molecule can be retained at the surfaces of Be 12 O 12 and Mg 12 O 12 nano-cages up to 700 K. Moreover, the thermodynamic calculations indicate that the reactions between H 2 S as well SO 2 with Be 12 O 12 and Mg 12 O 12 nano-cages are exothermic. Our results suggest that we can use Be 12 O 12 and Mg 12 O 12 nano-cages as sorbents as well as sensors for H 2 S and SO 2 gases.

The structural, electronic and optical properties of transition metal doped porphyrin (TM@P; TM = Mn, Co, Fe, Cu, Ni, Zn) as well as the effect of CO adsorption on TM@P properties have been investigated using the density functional theory (DFT). The presented results include adsorption energies, bond lengths, electronic configurations, magnetic moments, density of states, frontier molecular orbitals, and UV-Vis. spectra. Our calculation results show that, the CO molecule favors to be adsorbed on TM-doped Porphyrin with its carbon head. The most energetically stable adsorption of CO is reported for Fe doped Porphyrin. The interaction between CO molecules with TM@P is attributed to donation-back donation as well as charge transfer mechanisms. Mn, Co and Fe-doped porphyrins have visible active nature which may be affected by CO adsorption, whereas, Ni, Cu and Zn-doped porphyrins have UV active nature which not affected by CO adsorption. These results may be meaningful for CO removal and detection., (© 2019 Published by Elsevier Ltd.)

The interactions of nitrogen dioxide molecule (NO2) on Au atom adsorbed on the surfaces of metal oxide MgO (100) on both anionic (O2-) and defect (F(s) and F(s)(+)-centers) sites have been studied using the Density Functional Theory (DFT) in combination with embedded cluster model. The adsorption energies of NO2 molecule (N-down as well as O-down) on O(-2), F(s) and F(s)(+)-sites were considered. Full optimization for the additive materials and partial optimization for MgO substrate surfaces have been done. The formation energies were evaluated for F(s) and F(s)(+) of MgO substrate surfaces. Some parameters, the Ionization Potential (IP) and electron Affinity (eA), for defect free and defect containing surfaces have been calculated. The interaction properties of NO2 have been analyzed in terms of the adsorption energy, the electron donation (basicity), the elongation of N-O bond length and the charge distribution by using Natural Bond Orbital (NBO) analysis. The adsorption properties were examined by calculation of the Density of State (DOS). The presence of the Au atom increases the surface chemistry of the anionic O(2-)-site of MgO substrate surfaces. On the other hand, the presence of the Au atom decreases the surface chemistry of the F(s) and F(s)(+)-sites of MgO substrate surfaces. Generally, the NO2 molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F(s) and F(s)(+)-centers.