BZ boot camp1 BZ History and Overview of Chemical Oscillators at Brandeis Irv Epstein

BZ boot camp2 What is the BZ? Named for discoverer (Boris Belousov) and developer (Anatol Zhabotinsky) Bromination and oxidation of an organic substrate (e.g., citric acid, malonic acid) by bromate in acidic (usually sulfuric acid) solution in the presence of a metal ion catalyst (e.g., cerium, ferroin, Ru(bipy) 3 )

BZ boot camp3

4 (as of 1991)

BZ boot camp5 The Lotka (-Volterra) model A + X  2X X + Y  2Y Y  P A = food, X = prey, Y = predator, P = dead With A fixed, gives periodic, antiphase oscillations of predator and prey for any set of rate constants Can be solved analytically Attractor is not a limit cycle, but a continuous set of orbits around a neutrally stable center (bad)

BZ boot camp6 Do chemical oscillators violate thermodynamics? A serious question until the 1970’s A chemical oscillator is not a pendulum – it doesn’t pass through equilibrium Prigogine – irreversible thermodynamics – must be far from equilibrium In a closed system (beaker), oscillations must necessarily be transient Can maintain oscillations indefinitely in an open system (flow reactor, organism)

BZ boot camp7 BZ history Discovered by Belousov in the Soviet Union in 1951 accidentally while searching for a model of the Krebs cycle Unable to publish in refereed journals, B publishes 1-page abstract in 1958 conference proceedings, circulates recipe and manuscript to colleagues in Moscow In 1961, Zhabotinsky repeats experiments, goes on to develop mechanism, find chemical waves

BZ boot camp8 BZ history (cont’d) Zhabotinsky publishes papers in 1960’s in Russian journals, but largely ignored In 1968, Zhabotinsky demonstrates reaction at Prague conference on biological and biochemical oscillators, catching the attention of Western scientists In 1971, Field, Koros and Noyes develop the FKN mechanism and F&N simplify it to the Oregonator model

BZ boot camp9 What’s so special about the BZ? Can run for many (hundreds) of cycles in a closed system Reactants are cheap, easily obtainable (but not biocompatible) Convenient time scale (minutes) Oscillations easily monitored visually, spectrophotometrically, potentiometrically Can be controlled photochemically Rich variety of spatial and temporal phenomena Good mechanism/model (FKN/Oregonator)

BZ boot camp10 Chemical Oscillators at Brandeis 1970’s – experiments with undergrads on perturbed and modified BZ reactions (Jacobs, Kaner, Heilweil) 1980’s – first systematically designed chemical oscillators (Kustin, De Kepper, Orban), mechanistic studies 1990’s – increasing focus on spatiotemporal behavior (Lengyel), interaction with neuroscientists (Marder), Zhabotinsky arrives 2000’s – patterns in microemulsions (Vanag), coupled oscillators via microfluidics (Fraden)

BZ boot camp11

BZ boot camp12 Coupled BZ Oscillators M. F. Crowley and I. R. Epstein, "Experimental and Theoretical Studies of a Coupled Chemical Oscillator: Phase Death, Multistability and In- and Out-of-Phase Entrainment," J. Phys. Chem. 93, (1989)

BZ boot camp II. I. time X time in sec Hexagonal closed packing 2D arrays

BZ boot camp14 BZ double emulsion 100  m time 70 min dimer tetrahedron

BZ boot camp15 Beyond the BZ – the CSTR

BZ boot camp16 Beyond the BZ – Taxonomy of chemical oscillators

BZ boot camp17 Another system – CIMA/CDIMA Chlorite-iodide-malonic acid (chlorine dioxide- iodine-malonic acid) Batch oscillator, discovered at Brandeis (IRE, De Kepper, Orban) in 1982 Used in first successful experiments on Turing patterns (Castets, De Kepper, 1990) Key is use of gel, starch indicator to get separation of effective diffusion coefficients

BZ boot camp18 Structured media – the future Limitations of aqueous solution – convection, no chemo-mechanics, all D’s nearly equal, can’t make a flow reactor Instead use surfaces, membranes, beads, microemulsions, droplet arrays, gels