Alcor Damien, Allemand Jean-François, Cogné-Laage Emmanuelle, Croquette Vincent, Ferrage Fabien, Jullien Ludovic, Kononov Alexeï, Lemarchand Annie
Ecole Normale Supérieure, Département de Chimie, C.N.R.S. U.M.R. 8640, 24, rue Lhomond, 75231 Paris Cedex 05, France.
J Phys Chem B. 2005 Jan 27;109(3):1318-28. doi: 10.1021/jp0468307.
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.
本文报道了一种在周期性外部场存在的情况下调节场敏感反应物有效扩散系数的新方法。我们研究了在周期性方波电场作用下，两种带负电荷的偶氮染料与α-环糊精（α-CD）相互作用的运动。我们表明，染料表现出的有效扩散系数D（eff）取决于染料在α-CD内络合的速率常数、场的周期和振幅。通过紫外-可见吸收光谱、梯度场（1）H核磁共振以及双光子激发后的荧光相关光谱（FCS）来证明，当满足被解释为随机共振的特定关系时，D（eff）可能会大幅增加，远超其固有值。目前的结果可能在化学动力学以及分子分选方面找到有用的应用。
