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Kinetic and mechanistic studies on the oxidation of d-glucose by MnO2 nanoparticles. Effect of microheterogeneous environments of CTAB, Triton X-100 and Tween 20
Molecular Catalysis ( IF 4.6 ) Pub Date : 2017-08-05 , DOI: 10.1016/j.mcat.2017.07.009
Pratik K. Sen , Jayanta K. Midya , Sandip Bysakh , Biswajit Pal

The kinetics of electron transfer reaction between D-glucose and MnO2 nanoparticles has been studied in weakly acid medium. In the colloidal solution of MnO2, ultrafine nanoparticles of MnO2 remain supported on two-dimentional gum acacia sheets in the form of crumbled paper ball assuming the form of spherical particulates of size 60–200 nm as detected by TEM. The nanoparticles are found to be amorphous. Apart from the inhibition, due to adsorption of reaction products on the surface of the nanoparticles, the reaction is first order with respect to MnO2, but complex order with respect to glucose as well as H+. Glucose is oxidized to δ-lactone through a one-step two-electron transfer process and the latter is rapidly hydrolyzed to gluconic acid. The oxidation of glucose in absence of surfactant is entropy-controlled. In the presence of surfactants of cetyl trimethyl ammonium bromide (CTAB), Triton X-100 (TX-100) and Tween 20, the reaction rate passes through a maximum around the CMC. Both the reactants are distributed between the aqueous and the micellar pseudophases and then react, following Berezin’s model. Ion-dipole interaction and H-bonding appear to play an important role in the binding between glucose and the surfactant molecules while protonated MnO2 remains at the periphery of the Stern layer within the micelle. The binding of glucose with the surfactants is controlled by the entropy changes associated with the glucose-water interaction, micelle-water interaction and glucose-micelle interaction.



中文翻译:

MnO 2纳米粒子氧化d-葡萄糖的动力学和机理研究。CTAB,Triton X-100和Tween 20微异质环境的影响

在弱酸性介质中研究了D-葡萄糖与MnO 2纳米粒子之间电子转移反应的动力学。以MnO的胶体溶液2,的MnO纳米颗粒超细2通过TEM所检测假设尺寸60-200纳米的球形颗粒形式保持支撑在粉碎纸球的形式二维阿拉伯胶片。发现纳米颗粒是无定形的。除了抑制作用之外,由于反应产物在纳米颗粒表面的吸附,相对于MnO 2来说,反应是一阶反应,而对于葡萄糖以及H +而言,反应是复数阶反应。。葡萄糖通过一步两电子转移过程被氧化为δ-内酯,然后后者迅速水解为葡萄糖酸。在不存在表面活性剂的情况下,葡萄糖的氧化是受熵控制的。在十六烷基三甲基溴化铵(CTAB),Triton X-100(TX-100)和Tween 20表面活性剂的存在下,反应速率在CMC附近通过最大值。两种反应物都分布在水相和胶束假相之间,然后按照Berezin模型进行反应。质子化MnO 2时,离子-偶极相互作用和H键似乎在葡萄糖和表面活性剂分子之间的结合中起重要作用保留在胶束内斯特恩层的外围。葡萄糖与表面活性剂的结合由与葡萄糖-水相互作用,胶束-水相互作用和葡萄糖-胶束相互作用相关的熵变化控制。

更新日期:2017-08-05
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