A TiO2@SiO2 hybrid support was prepared by the sol-precipitation method using n-octylamine as a template.The photocatalyst manganese phthalocyanine tetrasulfonic acid (MnPcS) was immobilized on the support to form MnPcS-TiO2@SiO2.X-ray diffraction (XRD) and UV-Visible diffuse reflectance spectra (UV-Vis DRS) were employed to characterize the catalyst.The photocatalytic degradation of rhodamine B (RhB) and the catalytic oxidation of o-phenylenediamine (OPDA) under visible light irradiation were used as probe reactions.The mineralization efficiency and the degradation mechanism were evaluated using chemical oxygen demand (COD Cr) assays and electron spin resonance (ESR),respectively.RhB was efficiently degraded by immobilized MnPcS-TiO2@SiO2 under visible light irradiation.Complete decolorization of RhB occurred after 240 min of irradiation and 64.02% COD Cr removal occurred after 24 h of irradiation.ESR results indicated that the oxidation process was dominated by the hydroxyl radical (·OH) and superoxide radical (O-·2) generated in the system.
WANG ShuLianFANG YanFenYANG YongLIU JunZiDENG AnPingZHAO XiaoRongHUANG YingPing
The mechanism of oxidative damage to deoxyribonucleic acid (DNA) by iron-containing mesoporous molecular sieves (MCM-41) irradiated with visible light was elucidated. Fe-loaded MCM-41 (Fe/MCM-41) was used as a photocatalyst and the damage to calf thymus DNA caused by hydrogen peroxide (H2O2) was studied. The damage and extent of oxidation of DNA were measured by high-performance liquid chromatography (HPLC) and intermediate products were detected by HPLC/electrospray ionization tandem mass spectrometry. Electron spin resonance was used to detect changes in reactive oxygen species and peroxidase catalytic spectrophotometry was used to determine the concentration of H2O2. The results indicated that Fe/MCM-41 efficiently activated H2O2 in solution at pH 4.0-8.0 under irradiation with visible light. The photocatalytic system degraded DNA most effectively at pH 5.0-6.0 but also operated at pH 8.0. At pH 4.2, the degree of DNA damage reached 25.65% after 5 h and the kinetic constant was 5.89×10 2 min 1. Damage to DNA was predominantly caused by hydroxyl radicals generated in the system. The mechanism of DNA damage is of potential concern to human health because it can occur in neutral solutions irradiated by visible light.
