Photodimerization and Micropatterning of Anthracene-Appended Receptors Covalently Bound to Silicon Surfaces: En Route to Write–Read–Erase Molecular Print Board
Résumé
Anthracene-appended receptor monolayers covalently bound to hydrogen-terminated Si(111) surfaces have been prepared from attachment of an aminoalkane-substituted receptor to a preassembled acid-terminated alkyl monolayer using carbodiimide coupling. Subsequent irradiation at 350 nm of the receptor-modified surface yielded the open → closed conversion of the grafted anthracene-appended receptor, as clearly supported by IR spectroscopy data. Grafting of the open receptor and its subsequent closing did not change significantly the surface topography, and atomic force microscopy (AFM) images showed formation of perfectly dense and homogeneous molecular films without adventitious contamination or aggregated islands. Scanning electrochemical microscopy (SECM) measurements in feedback mode using an appropriate redox mediator (i.e., 9,10-diethoxyanthracene DEA) provided clear evidence for an efficient charge transport process between grafted receptors. However, the kinetics of the mediator regeneration was faster when the receptors were under their closed form. Interestingly, light-activated switching of the anthracene-appended receptor offered the unique opportunity to pattern the surface using UV photolithography through an optical mask. After the lithographic step, the SECM image clearly showed the expected current regeneration contrast between the open and produced closed receptor micropatterns.