Photoinitiated quenching reactions of excited triplet duroquinone by vitamin C in homogeneous and AOT (SDS) micelle solutions

Time-resolved EPR has been used to study the photoinitiated reactions of the excited triplet of duroquinone (³DQ^*) quenched by the antioxidant vitamin C (VC) in homogeneous solutions of ethylene glycol/water (EG/H₂O) and micelle solutions of aerosol OT (AOT) and sodium dodecyl sulphate (SDS). During the photolysis reactions of DQ and VC in homogeneous solutions of EG/H₂O, ³DQ^* abstracts hydrogen atoms from the solvent EG and the antioxidant VC. The rate constant for the quenching of ³DQ^* by VC is 4.90 × 10⁷ L mol^?1 s^?1, close to being diffusion-controlled. In AOT and SDS micelle solutions, rate constants for the quenching of ³DQ^* by VC are 3.28 × 10⁷ and 3.15 × 10⁷ L mol^?1 s^?1, respectively. Lipid-soluble ³DQ* and water-soluble VC need to diffuse to the w/o interface to react, which reduces the reaction rate between ³DQ* and VC. The charge repulsion interaction between the anionic shell of AOT (SDS) micelles and the VC monoanions AsH^? also slows the reaction.