Controlling the Ru-catalyzed Belousov-Zhabotinsky reaction by addition of hydroquinone

Oscillation patterns in the photosensitive Belousov-Zhabotinsky reaction composed of malonicacid/BrO3-/Ru(bpy)32+/H+ were modulated by addition of less than 100 mM of hydroquinone. In dark, the limit cycle oscillations bifurcated into mixed-mode oscillations of 11 and 12 with hydroquinone concentration, where the superscripts indicate the number of small-amplitude oscillations. Under illumination, three types of pattern change were observed depending on the initial composition of the reaction mixture. A probable mechanism to explain the role of hydroquinone is proposed on the basis of the Field-Körös-Noyes mechanism and the photocycle of the Ru-catalyst.