Radical Species Production and Color Change Behavior of Wood Surfaces Treated with Suppressed Photoactivity and Photoactive TiO2 Nanoparticles

The use of TiO2 nanoparticles for photoprotection comprise a side effect due to the photocatalysis of the nanoparticles under UV radiation. In this work we studied how the suppression of TiO2 photocatalytic activity may affect the production of phenoxy radicals and the color of wood surfaces exposed to UV radiation. The experimental work considered the modification of TiO2 nanoparticles to reduce its photoactivity and the use electron paramagnetic resonance to test free radical production. Wood samples were treated with the different TiO2 nanoparticles and the radical production and color changes were evaluated after UV exposure. Experimental results showed that in wood samples exposed to UV radiation the use of TiO2 with suppressed photoactivity yielded increased amounts of phenoxy radicals, in comparison to samples treated with photoactive TiO2. Similar results were obtained in terms of color change, where samples treated with suppressed photoactivity TiO2 showed significantly higher color changes values, after 2000 h of UV exposure, than samples treated with photoactive TiO2. These results suggest that in wood surfaces, the photocatalytic effect of TiO2 may be crucial on the performance of the nanoparticles as photoprotective treatment.

Iron-mediated site-selective oxidative C–H/C–H cross-coupling of aryl radicals with quinones: synthesis of β-secretase-1 inhibitor B and related arylated quinones

Phenoxy radicals were converted into para site selective C-aryl radicals and coupled with quinones, using an inexpensive FeCl3–K2S2O8 system, to obtain several arylated quinones, in good to moderate yields.

Effect of phenolic radicals on the geometry and electronic structure of DNA base pairs: computational study

In this paper, we show the reaction of a hydroxyl, phenyl and phenoxy radicals with DNA base pairs by the density functional theory (DFT) calculations. The influence of solvation on the mechanism is also presented by the same DFT calculations under the continuum solvation model. The results showed that hydroxyl, phenyl and phenoxy radicals increase the length of the nearest hydrogen bond of adjacent DNA base pair which is accompanied by decrease in the length of furthest hydrogen bond of DNA base pair. Also, hydroxyl, phenyl and phenoxy radicals influenced the dihedral angle between DNA base pairs. According to the results, hydrogen bond lengths between AT and GC base pairs in water solvent are longer than vacuum. All of presented radicals influenced the structure and geometry of AT and GC base pairs, but phenoxy radical showed more influence on geometry and electronic properties of DNA base pairs compared with the phenyl and hydroxyl radicals.

Photoionization access to cyclodextrin-encapsulated resveratrol phenoxy radicals and their repair by ascorbate across the phase boundary

Photoionization with UV-A generates phenoxy radical ResO˙ of the famous red-wine antioxidant resveratrol inside cyclodextrin cavities without the participation of auxiliary reactants. This permits the isolated exploration of the ResO˙ repair by ascorbate at the water–cyclodextrin interface.