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BZ History and Overview of Chemical Oscillators at Brandeis

BZ History and Overview of Chemical Oscillators at Brandeis. Irv Epstein. What is the BZ?. Named for discoverer (Boris Belousov) and developer (Anatol Zhabotinsky)

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BZ History and Overview of Chemical Oscillators at Brandeis

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  1. BZ History and Overview of Chemical Oscillators at Brandeis Irv Epstein BZ boot camp

  2. 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 camp

  3. BZ boot camp

  4. (as of 1991) BZ boot camp

  5. 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 camp

  6. 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 camp

  7. 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 camp

  8. 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 camp

  9. 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 camp

  10. 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 camp

  11. BZ boot camp

  12. 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, 2496-2502 (1989) BZ boot camp

  13. Hexagonal closed packing 2D arrays I. X II. 0 80 240 165 80 85 75 time in sec BZ boot camp time

  14. BZ double emulsion dimer tetrahedron 100 mm time 70 min BZ boot camp

  15. Beyond the BZ – the CSTR BZ boot camp

  16. Beyond the BZ – Taxonomy of chemical oscillators BZ boot camp

  17. 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 camp

  18. 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 BZ boot camp

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