Organized Media as Redox Catalysts

Micellar catalysis for a methylene blue (MB)−ascorbate ion (AA - ) redox reaction (activation energy 114 kJ mol - 1 ) has been observed to occur because of the binding of the substrates onto the micellar surface by hydrophobic and electrostatic interaction. This increases the encounter probability, leading to a substantially accelerated reaction. The reported study indicates that the most likely substrate solubilization sites in micelles and reverse micelles are the interfacial and Stern regions. Studies on the effect of various salting-in and salting-out agents, an increase in the hydrophobicity of the dye, and the size of the reverse micellar water pool provide no evidence of deeper penetration into the micellar core. In addition, a fascile reversible electron-transfer reaction for the MB−AA - and MB−BH 4 - systems has been observed with coinage metal sol particles. Metal sol-induced catalysis occurs due to the availability of a suitable substrate which acts as a mediator for the electron-transfer reaction between MB and the reductant.