Abstract Methylene blue (MB) (3,7-bis (dimethylamino)-phenothiazin-5-ium chloride) is a harmful pollutant and has been long been known for its detrimental effects on human health. Over the recent years, many strategies including reduction, oxidation, biological and photochemical degradation have been reported for converting this harmful dye into commercially useful products. Among the aforementioned strategies, the nanocatalytic reduction of MB into its reduced counterpart, i.e. leucomethylene blue, is considered more preferable because it has been reported to have numerous applications in various industrial fields in the academic literature. The reduction of MB is the kinetically unfavorable reaction. Henceforth, various nanocatalytic systems utilizing different kinds of stabilization mediums have reportedly been used for speeding up this particular reaction. This article attempts to not only describe the fundamental properties of the reduction reaction of MB but also present the classification of the recently reported nanocatalytic assemblies on the basis of the utilized supporting medium. Various techniques used for the characterization of nanocatalytic systems reported for the reduction of MB have been summarized in this review. The thermodynamics, kinetics and mechanistic studies of this nanocatalytic reaction have also been narrated here. This critical review has been written comprehensively to abridge the recent research progress in the assemblage of nanocatalytic systems used for the reduction of MB and to propose some new ideas for further development in this area.

中文翻译：

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纳米催化剂存在下亚甲基蓝的化学还原：批判性评论

摘要 亚甲蓝 (MB)（3,7-双（二甲氨基）-吩噻嗪-5-鎓氯化物）是一种有害污染物，长期以来因其对人类健康的不利影响而闻名。近年来，已经报道了许多策略，包括还原、氧化、生物和光化学降解，将这种有害染料转化为商业上有用的产品。在上述策略中，MB 的纳米催化还原为其还原的对应物，即无色亚甲蓝，被认为是更可取的，因为据报道它在学术文献中的各个工业领域有许多应用。MB的减少是动力学上不利的反应。今后，据报道，利用不同种类的稳定介质的各种纳米催化系统已被用于加速这一特定反应。本文不仅试图描述 MB 还原反应的基本性质，而且还根据所使用的支持介质对最近报道的纳米催化组件进行分类。本综述总结了用于表征纳米催化系统的各种技术，用于还原 MB。该纳米催化反应的热力学、动力学和机理研究也已在此叙述。