Stochastic resonance to control diffusive motion in chemistry.
This paper reports on a novel procedure to tune the effective diffusion coefficient of a field-sensitive reactant in the presence of a periodic external field. We investigate the motion of two negatively charged azo dyes interacting with alpha-cyclodextrin (alpha-CD) upon action of a periodic square wave electrical field. We show that the dyes exhibit an effective diffusion coefficient D(eff) that depends on the rate constants for dye complexation within alpha-CD, the period and the amplitude of the field. UV-vis absorption, gradient field (1)H NMR, and fluorescence correlation spectroscopy (FCS) after two photon excitation are used to evidence that D(eff) may be increased far beyond its intrinsic value when specific relations interpreted as a stochastic resonance are fulfilled. The present results may find useful applications in chemical kinetics as well as for molecular sorting.
Alcor
Damien
D
Ecole Normale Supérieure, Département de Chimie, C.N.R.S. U.M.R. 8640, 24, rue Lhomond, 75231 Paris Cedex 05, France.
Allemand
Jean-François
JF
Cogné-Laage
Emmanuelle
E
Croquette
Vincent
V
Ferrage
Fabien
F
Jullien
Ludovic
L
Kononov
Alexeï
A
Lemarchand
Annie
A