Fabrication of New Belousov-Zhabotinsky Micro-Oscillators on the Basis of Silica Gel Beads.

We have fabricated and examined silica gel beads loaded with a catalyst of the Belousov-Zhabotinsky (BZ) reaction, tris(2,2'-bipyridyl)ruthenium(II) chloride, Ru(bpy)3Cl2, the BZ beads. The abilities of silica gel and the widely used ion-exchange resin (Dowex 50WX2) BZ beads to oscillate in a catalyst-free BZ solution are compared. The period of the BZ oscillations increases with an increase in the diameter (40-250 μm) of both types of the BZ beads. The ability of the ion-exchange resin beads to hold catalyst molecules significantly decreases with a decrease in pH, while this value is less dependent on pH for the silica gel BZ beads. The diffusive coupling of two BZ beads separated by either aqueous or oil gaps is studied as well. For the aqueous gap less than 100 μm, the BZ beads of both types demonstrate in-phase synchronization. For the oil phase, the Dowex BZ beads are unable to oscillate for a long enough time and therefore cannot be synchronized, while the silica gel BZ beads are able to oscillate for several hours and demonstrate anti-phase synchronization for gaps less than 40 μm.