Reactions of hydrophobic organic nanoparticle mixtures in water: nanoparticle-on-nanoparticle oxidative dye bleaching

The oxidative bleaching between mixed organic nanosuspensions of hydrophobic dyes and oxidising agents has been demonstrated to be faster in water than homogeneous organic solvent reactions conducted at the same temperature. Aqueous nanosuspensions of both Oil Red O and ε-phthalimido-peroxy-hexanoic acid were generated using a nanoprecipitation technique and reacted at various temperatures. At 50 °C, bleaching within the nanosuspension was achieved in approximately 30 minutes; considerably faster than the comparative reaction in acetone or the mixed organic powders in water (>48 hours). Kinetic analyses show dramatic increases in reaction rates and modified rate constants and a 7-fold decrease in apparent activation energy.