Light Irradiation In Presence Research Articles

Synthesis of TiO2−x visible-light photocatalyst using N2/Ar/He thermal plasma for low-concentration elemental mercury removal

Oxygen-vacant titanium dioxide (TiO2−x) nanoparticles possessing a narrower band gap were synthesized with a single-step process using N2/Ar/He thermal plasma as a heating source. Sample characterization showed that the formed TiO2−x nanoparticles had a size within 5–40nm and were in a mixing form of anatase and rutile. An evident absorption red shift to 470nm wavelength was observed. The deconvolution results of XPS spectra supported the formation of TiO2−x due to the presence of Ti3+2p peaks. The Hg removal efficiency of TiO2−x nanoparticles increased with increasing O2 concentration and in the presence of light irradiation, suggesting an enhancement in Hg0 oxidation. H2O molecules, however, greatly reduced the Hg removal of TiO2−x under visible-light (VL) irradiation. The photoinduced hydrophilicity of TiO2−x under VL irradiation was suspected to amplify the competitive adsorption of H2O that decreased Hg capture. Hg removal performances at 50°C were better than those at 25 and 100°C, suggesting that both adsorption and catalytic oxidation limit the Hg removal. These observations also implicate that the bonding between TiO2−x and adsorbed Hg was weak and adsorption reaction may be reversible.

Negative photoconductivity induced by surface plasmon polaritons in Ag nanowire macrobundles

We study experimentally and theoretically the transport properties of Ag nanowire macrobundles in the presence of light irradiation. We have observed significant negative photoconductivity induced by the interaction between electrons and the excited surface plasmon polaritons (SPPs). As temperature T increases from 77 K to 304 K, the dark resistivity rhod without light irradiation increases linearly with T, and the resistivity change Deltarho due to light irradiation decreases nonlinearly with increasing T. The current change |DeltaI| due to light irradiation, which is proportional to the laser intensity, also decreases nonlinearly with increasing T. We explain well the experimental results using our proposed model with a new scattering channel due to the interaction between electrons and SPPs. Both our experimental and theoretical results reveal the novel phenomena due to the combination of photonics and electronics properties of Ag nanowires and they will be useful for scientific research, and technical applications.

Photoelectrocatalytic Oxidation of NADH at a Graphite Electrode Modified with a New Polymeric Phenothiazine

AbstractA new approach for photoelectrocatalytic oxidation of NADH is described, based on a graphite electrode (G) modified with a new phenothiazine derivative, polyphenothiazine formaldehyde (PPF). Electrochemical measurements reveal that G/PPF presents a quasireversible voltammetric response, corresponding to a 2e−/2H+ transfer and that G/PPF modified electrodes show electrocatalytic activity for NADH oxidation. When the surface of the G/PPF modified electrode was irradiated with a light source (250 W Halogen lamp), a significant increase in the electrocatalytic current was observed. The second order electrocatalytic rate constant (kobs, [NADH]=0=3.9×103 M−1 s−1, pH 7.0) was calculated from rotating disk electrode experiments, performed at various NADH concentrations. From amperometric measurements, it was noticed that, in the presence of light irradiation, the sensitivity of NADH detection (calculated as Imax/KM ratio) increased ca. 3 times.

Flavor Components in Edible Fats and Oils

Effects of minor components on the oxidative and flavor stabilities of edible fats and oils are discussed. Main components of green pigments in edible vegetable oils are pheophytins a and b. Pheophytins can produce the singlet oxygen to accelerate the oxidative deterioration of oils in the presence of light irradiation as well as chlorophylls. Chlorophylls and their derivatives, however act as a free radical scavenger to inhibit the autoxidation of oils under the dark condition.Carotenoides and tocopherols affect on the photo-and autoxidation of oils, while free fatty acids, mono-, and diglycerides and sterols affect on the flavor stabilities of oils.