Active oxygen species (AOS) generated in the atmosphere can be applied in various industrial processes owing to their extremely strong oxidative ability. Methylene blue (MB) decolors upon exposure to AOS owing to dye degradation; this property can be used to detect the AOS. To detect AOS with higher oxidative ability, it is necessary to stabilize MB by mixing it with sodium alginate. In our previous work, we showed that the OH* concentration in the AOS increased under the high-humidity condition. Herein, the decolorization mechanism of MB-dyed sodium alginate thin films upon exposure to AOS was elucidated under low- and high-humidity conditions; decolorization was observed only under the latter. We analyzed an MB-dyed sodium alginate thin film indicator to elucidate the chemical reactions occurring as well as the decolorization mechanism generated under the high-humidity condition. We found that the decolorization of the film was caused by MB decomposition upon exposure to the AOS generated under the high-humidity condition.

Polyether ether ketone (PEEK) is a substrate for metal plating to overcome insulation defects and satisfy the increased demands of mechanically robust electronic circuit boards. However, pristine PEEK is hydrophobic; hence, the adhesion between the metal film and PEEK substrate is poor. Therefore, the PEEK surface should be modified to improve hydrophobicity. We have proposed the active oxygen (AOS) treatment under ultraviolet (UV) light as an alternative to a conventional plasma treatment method. Characteristics of the PEEK surfaces obtained by these methods are compared. We explore the effects of reactive‐oxygen and UV light exposure time on the PEEK surface modification. The contact angle of water drop on PEEK after the AOS treatment is lower than that of untreated PEEK. Furthermore, COO groups are observed on the PEEK surface after the treatment. Although plasma treatment has the effect of roughening the surface, it is desirable not to roughen the surface for use in electronic circuit boards. Moreover, we have reported the adhesion strength between PEEK and copper plating without surface roughening.

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