The anaerobic photocatalysed reduction of methylene blue, MB, by glycerol to leuco methylene blue, LMB, is studied using UV-absorbing, P25 TiO₂, and visible-absorbing, CdS, semiconductor powder particles as the photosensitizer. In both cases, the photo-reductive bleaching of the dye to LMB, is very rapid, typically <2 min. The photobleaching of the MB is readily and simply reversed in the dark by allowing air into the system, so as to let the ambient oxygen to oxidise the photogenerated LMB back to its original blue, oxidized form, MB. Action spectra are recorded for both systems and reveal no evidence of dye-sensitisation, nor dye photolysis over the time scale of the reaction (i.e. ca. 2 min). Instead, the action spectra exhibit spectral profiles that match very well that of the diffuse reflectance spectra of the respective semiconductor photocatalysts. The MB/glycerol system appears to offer a simple, quick, unambiguous way to assess the photocatalytic activity of both visible and UV absorbing photocatalyst powders using a dye, such as MB.

研究了使用P25 TiO ₂紫外线吸收剂，厌氧光催化甘油将亚甲基蓝MB还原为无色亚甲基蓝LMB。以及吸收可见光的CdS半导体粉末颗粒作为光敏剂。在这两种情况下，染料到LMB的光还原漂白都非常快，通常小于2分钟。通过允许空气进入系统，MB的光漂白很容易在黑暗中逆转，从而让环境氧将光生LMB氧化回其原始的蓝色氧化形式MB。记录了两个系统的动作光谱，在反应时间范围内（即约2分钟），没有发现染料敏化的迹象，也没有染料光解的迹象。相反，作用光谱表现出与各个半导体光催化剂的漫反射光谱的光谱分布非常匹配的光谱分布。MB /甘油系统似乎提供了一种简单，快速，