Methylene green voltammetry in aqueous solution: Studies using thermal, microwave, laser, or ultrasonic activation at platinum electrodes

The voltammetry of the aqueous two-electron reduction of the phenothiazine dye methylene green, known to be passivating at platinum electrodes, is rep orted under simultaneous activation with each of the following techniques: thermal activation in the temperature range 15-80 degrees C, pulsed microwa ve activation with a modified 800 W, 2.45 GHz domestic microwave oven, 10 H z pulsed laser activation with a Nd:YAG laser at 532 nm, sonication, or ult rasonic activation where a 20 kHz ultrasonic horn probe is employed to gene rate an aqueous/organic solvent emulsion. The relative merits of the five m ethodologies are compared and discussed in terms of surface activation and cleaning, mass-transport enhancement, and reduction mechanism elucidation. Comparisons are also drawn with the voltammetry of methylene blue, a dye of the same family. This is the first full report of both the effects of micr owave heating on surface redox electrochemistry and of the sonoemulsion tec hnique.