Fabrication of Ag-Decorated CaTiO3 Nanoparticles and Their Enhanced Photocatalytic Activity for Dye Degradation.

CaTiO3nanoparticles of 30-40 nm in size were synthesized via a polyacrylamide gel route. Ag nanoparticles with size of 8-16 nm were deposited onto CaTiO3particles by a photochemical reduction method to yield CaTiO3@Ag composites. The photocatalytic activity of prepared samples was evaluated by degrading methyl orange under ultraviolet irradiation. It is demonstrated that Ag-decorated CaTiO3 particles exhibit an enhanced photocatalytic activity compared to bare CaTiO3 particles. After 60 min of photocatalysis, the degradation percentage of MO increases from 54% for bare CaTiO3particles to 72% for CaTiO3@Ag composites. This can be explained by the fact that photogenerated electrons are captured by Ag nanoparticles and photogenerated holes are therefore increasingly available to react with OH⁻/H2O to generate hydroxyl (·OH) radicals. ·OH radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing an enhanced yield on the irradiated CaTiO3@Ag composites. In addition, it is found that the addition of ethanol, which acts as an ·OH scavenger, leads to a quenching of ·OH radicals and simultaneous decrease in the photocatalytic efficiency. This suggests that ·OH radicals are the dominant active species responsible for the dye degradation.

N1-acetyl-N2-formyl-5-methoxykynuramine, a biogenic amine and melatonin metabolite, functions as a potent antioxidant.

The biogenic amine The biogenic amine N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) was investigated for its potential antioxidative capacity. AFMK is a metabolite generated through either an enzymatic or a chemical reaction pathway from melatonin. The physiological function of AFMK remains unknown. To our knowledge, this report is the first to document the potent antioxidant action of this biogenic amine. Cyclic voltammetry (CV) shows that AFMK donates two electrons at potentials of 456 mV and 668 mV, and therefore it functions as a reductive force. This function contrasts with all other physiological antioxidants that donate a single electron only when they neutralize free radicals. AFMK reduced 8-hydroxydeoxyguanosine formation induced by the incubation of DNA with oxidants significantly. Lipid peroxidation resulting from free radical damage to rat liver homogenates was also prevented by the addition of AFMK. The inhibitory effects of AFMK on both DNA and lipid damage appear to be dose-response related. In cell culture, AFMK efficiently reduced hippocampal neuronal death induced by either hydrogen peroxide, glutamate, or amyloid b25-35 peptide. AFMK is a naturally occurring molecule with potent free radical scavenging capacity (donating two electrons/molecule) and thus may be a valuable new antioxidant for preventing and treating free radical-related disorders.