Ab initio study of superoxide dismutase (SOD) and catalase activity of EUK-134.

Dismutation reaction of superoxide radical catalyzed by EUK-134 has lower activation energy than non-catalytic reaction, and therefore, EUK-134 catalyzes dismutation reaction of superoxide radical. For non-catalytic dismutation reaction of hydrogen peroxide, there are three possible reaction paths, among which MEP3 has the lowest activation energy, and therefore, is thought to be the most probable reaction path. Dismutation reaction of hydrogen peroxide catalyzed by EUK-134 occurs in two successive steps and has lower energy barrier than non-catalytic dismutation reaction, and therefore, EUK-134 is thought to catalyze the dismutation reaction of hydrogen peroxide. HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) and ESP-fitted charge analysis of EUK-134 indicate that Mn atom plays an electron acceptor and donor for dismutation reactions of superoxide radical and hydrogen peroxide catalyzed by EUK-134, respectively.

Adsorption characteristics of citric acid on Fe3O4 (001), (011), and (111) surfaces.

Magnetite (001), (011), and (111) surfaces were the focus of our study. Magnetite (001) surface has two different terminations, that is, Fetet and 2Feoct4O. Magnetite (011) surface has two different terminations, that is, 2Feoct4O and 2Fetet2Feoct4O. Magnetite (111) surface has six different terminations, that is, Fetet1, Feoct, Fetet2, 3Feoct, 4O1, and 4O2. Comparing surface energies of (001), (011), and (111) surfaces, (001) has the smallest surface energy, and (111) has the largest surface energy except for Feoct termination, which means that (001) surface is the easiest to be cleaved, followed by (011) and (111) surfaces. Comparing adsorption energies of citric acid onto (001), (011), and (111) surfaces, (111) has the largest adsorption energies except for Fetet2 termination, and (001) has the smallest adsorption energies, which means that (111) surface is the most active for citric acid adsorption, followed by (011) and (001) surfaces. PDOS (partial density of states) of citric acid adsorbed onto (001), (011), and (111) surfaces with different terminations shows that 3d orbital of Fe of magnetite surface does not contribute to the adsorption, and 4s orbital of Fe of magnetite surface and 2s and 2p orbitals of O of citric acid contribute to the adsorption.

Ab initio study of photocatalytic characteristics of graphitic carbon nitride assisted by oxalic acid.

Using density functional theory, structural, electronic, and optical properties of GCN (graphitic carbon nitride) and OAGCN (graphitic carbon nitride combined with oxalic acid) were studied. By comparing HOMOs and LUMOs and excitonic binding energies, OAGCN has lower photoinduced electron-hole recombination rate than GCN. VBM and CBM levels of GCN and OAGCN were calculated, which shows that for GCN, only the electron at CBM contributes to produce radicals for removing pollutants, and for OAGCN, both the electron at CBM and the hole at VBM contribute to produce radicals for removing pollutants. In total, it can be said that OAGCN has higher photocatalytic activity than GCN.