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Methylene blue based on the nafion film was prepared and chemical reactions in contact with active oxygen species were estimated. In addition, decolorization mechanism of the film due to exposure of the active oxygen species is discussed. The active oxygen species was exposed to the methylene blue based on the nafion film in low and high humidity conditions. Although decolorization of the film was hardly observed when it was exposed in the ozone and the active oxygen species in low humidity condition, the decolorization was observed when it was exposed in the high humidity condition. It is considered that the decolorization of the film due the active oxygen species exposure relates to the degradation reaction of the methylene blue molecule due to hydroxyl radicals.

A B S T R A C TFor efficient industrial application, it is necessary to understand the formation mechanisms of active oxygen species under ultraviolet (UV) light irradiation. In this study, active oxygen was generated by UV lamps (providing wavelengths of 185 and 254 nm) at two different humidity levels. The generation of excited singlet oxygen [O( 1 D)] and hydroxyl radicals (OH*) in the atmosphere were detected using the electron spin resonance (ESR) method, while ozone (O 3 ) was detected using a gas tube. The concentrations of O( 1 D) and O 3 generated under low humidity conditions were much higher than those generated at high humidity. On the other hand, the concentration of OH* generated under high humidity condition were much higher than that generated at low humidity. The amount of O( 1 D) increased linearly with irradiation time, while the increase of O 3 concentration was observed to be suppressed after 5 min. Fluorocarbon thin films r.f.-sputtered onto quartz crystal oscillators were used to investigate the etching behavior of generated active oxygen species. The etching rates were found to be higher at high humidity, which is believed to be due to the contribution of OH* whose concentration was higher in the presence of larger amounts of water in the atmosphere.

The roughness and cleanness of a titanium surface must be controlled in order to investigate the expression mechanism of hard tissue compatibility on titanium. In this study, osteogenic MC3T3-E1 cells were cultured and differentiation-induced on bulk and sputter-deposited titanium specimens, and the osteogenesis were investigated. For the preparation of bulk specimens, titanium discs were mirror-polished. On the other hand, titanium was sputter-deposited on smooth and clean cover glasses as sputter-deposited specimens. As a result, no significant difference was observed in the cell morphology and attached number. On the other hand, the time showing maximum activity in the alkaline phosphatase and gene expressions, which are related to bone differentiation on the bulk titanium, were superior to those on the sputter-deposited titanium. From the surface observation of the specimens with a scanning electron microscope and a scanning probe microscope, the surface on the sputter-deposited titanium was more uniform and cleaner than that on the bulk titanium. According to X-ray photoelectron spectroscopy, the thickness of surface oxide film on the sputter-deposited titanium was smaller than that on the bulk titanium. In addition, the proportions of TiO and Ti(2)O(3) in the surface oxide film on the sputter-deposited titanium were larger than those on the bulk titanium. These differences might influence the differentiation of osteoblastic cells.