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Title: Exploring reactivity pathways at liquid/solid and air/solid interfaces
Other Titles: De studie van chemische reacties in de nabijheid van een vaste stof
Authors: Plas, Jan
Issue Date: 11-Apr-2016
Abstract: The controlled nanoscale functionalization of substrates by means of molecular self-assembly processes has attracted the attention of many people within the surface science community. This has led to great achievements ranging from the fabrication of complex nano-architectures to monolayer transformations through the addition of active reagents. Besides the reduced dimensions of the created structures, a second advantage of working in a 2D confined environment is the applicability of scanning tunneling microscopy (STM) as an analytical tool, which is capable of providing nanometer spatial resolution of the surface assemblies. The downside of 2D self-assembly processes is their limited stability towards external stimuli. In recent years, a significant amount of progress has been made in the synthesis of extended, covalently linked networks on surfaces (2D COFs), which has led to a good understanding of the critical reaction parameters of the studied coupling reactions. However, the applicability of these covalent networks towards the inclusion of functional molecules has only been briefly explored and there is still room for improvement in the type of chemical bonds that are being formed. Moreover, self-assembly on surfaces has great potential towards selective product formation, although only a few studies have addressed this challenge.

Therefore, in the first part of this thesis, we will investigate the possibility to influence chemical equilibrium processes in solution by means of self-assembly on a substrate. Both a deracemization approach and chemoselectivity from a dynamic combinatorial library are explored and it is shown that indeed the surface can steer the reaction equilibrium in favor of the strongest adsorbing product. Furthermore, we discovered that straightforward chemical reactions can be significantly accelerated in presence of high surface area substrates.

The second part of the thesis focusses on the use of a known type of 2D COF as a host network for the functional guest molecule C60, and the further stabilization of 2D COFs with stronger, irreversible chemical bonds. A size match between the porous network and the guest molecule enables the formation of extended host/guest networks and even further functionalization is feasible by means of nanolithography. Due to the covalent nature of the host, we were able to reveal the driving forces behind the incorporation of the guest molecules.

Although irreversible bonds impede the formation of crystalline 2D COFs, we foresee that upon further optimization, this approach will eventually lead to networks with superior stability and great potential in future applications.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Molecular Imaging and Photonics

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