On-surface fabrication of covalently bounded nanostructures monitored by HR-AFM at ambient conditions
Résumé
The fabrication of extended and compact nanostructures based on on-surface polymerisation has emerged a widespread research objective because these nanostructures can be integrated as nanocomponents in functional devices due to their electronic and photo physical proprieties. Most of onsurface reactions require catalytic role of the metal surface, which prevent the formation of extended nanostructures due to the presence of organo-metallic intermediate or on surface-defects which strongly hinder the formation of compact and well-ordered nanostructures. Here, we propose to use reactions promoted by thermal or light stimuli without any role of metal atom as “catalyst”. Herein we present onsurface [4 + 2] cycloaddition of 1,4-bis-(4’-vinyl)-2,5-bis(decyloxy)benzene (VINYL) molecules initiated by thermal polymerization and light-induced homo-polymerisation of 4-[(S,S)-2,3- Epoxyhexyloxy]phenyl-4-decyloxy)benzoate (EPOXY) molecules deposited on HOPG surface and monitored by high-resolution AFM at ambient conditions. After deposition of the two type of molecules on HOPG, we observed the formation of periodic, compact and large extended 2D supramolecular networks (see Fig.1a and 1.d). After UV-light exposure of the network constituted by EPOXY molecules or thermal annealing of those constituted by VINYL molecules, we observed a modification of the periodicity of the nanostructures. The difference in periodicity might be contribute to the formation of ether bridge between two adjacent molecules. We shall propose molecular adsorption models corresponding to network before and after polymerization. The chemical nature of resulting polymers is currently investigated.