He investigates the kinetics of multivalent binding on surfaces, to understand and control multivalency at liquid-solid interfaces. The kinetic stability of patterned mono- and multivalent SAMs on the surface of a β-cyclodextrin based molecular printboard is studied by means of fluorescence microscopy, when the samples are immersed in a controlled volume of β-cyclodextrin solution. Lissamine rhodamine B labeled water-soluble molecules equipped with one, two or three adamantane moieties linked through flexible tetraethylane glycol spacers are used as mono- and multivalent guests. The evolution of the fluorescent pattern in time is in situ monitored at various β-cyclodextrin concentrations. In this competitive environment, two main spreading mechanisms can be envisaged: (a) spreading by desorption / re-adsorption mechanism, when after the complete desorption the diffusion in the solution of the guest molecules is governed by Fick’s laws, followed by the re-adsorption on the molecular printboard; or/and (b) spreading by a ‘walking’ mechanism, when the adamantyl “legs” are desorbed and adsorbed from and to the β-cyclodextrin printboard separately, one after the other (Scheme 1).
Scheme 1. Proposed spreading mechanism of the divalent fluorescent guest on the molecular printboard: a - spreading by desorption / re-adsorption mechanism, b- spreading by a ‘walking’ mechanism.