Black spots in a surfactant-rich Belousov-Zhabotinsky reaction dispersed in a water-in-oil microemulsion system

The Belousov-Zhabotinsky (BZ) reaction dispersed in water-in-oil aerosol OT (AOT) microemulsion has been studied at small radius R-d of water nanodroplets (R-d (nm)congruent to 0.17 omega,omega=[H2O]/[AOT]=9). Stationary spotlike and labyrinthine Turing patterns are found close to the fully oxidized state. These patterns, islands of high concentration of the reduced state of the Ru(bpy)(3)(2+) catalyst, can coexist either with "black" reduction waves or, under other conditions, with the "white" oxidation waves usually observed in the BZ reaction. The experimental observations are analyzed with the aid of a new Oregonator-like model and qualitatively reproduced in computer simulations. (c) 2005 American Institute of Physics.