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Self-assembled monolayers

Self-assembled monolayers
This is an image of a self-assembled monolayer

Organic self-assembled monolayers are a widely used method for surface modification of metals and metal oxides in fundamental investigations of interfacial phenomena and design of molecular-scale devices. Centre members are designing new functionalized monolayers for applications in catalysis by incorporation of organometallic groups, in optoelectronics by creating films with extended conjugation, and for model biological surfaces and biosensors through the addition of molecular recognition groups.

Molecular-level characterization of these films is critical to their envisioned applications. Novel characterization techniques employed by the Centre members include electrochemical-atomic force microscopy (EC-AFM), surface plasmon resonance spectroscopy (SPR), microcantilever sensors, high resolution solid-state NMR spectroscopy, and a spectroscopic method that probes the chemical and physical modifications induced in thin organic films by very low energy electron impact.

Projects

Patterned self-assembled films

Phase-separation in mixed monolayers of phospholipids, alkylthiols, and alkylsilanes is being exploited to create self-patterned monolayer assemblies that are chemically or physically differentiated. These thin films are used to template the selective deposition of macromolecules, nanoparticles, and the crystallization of organic molecules on the submicron scale, thereby creating new surface structures and materials.

Organometallic thin films

Metal ions can organize organic fragments (ligands) in a predetermined manner to dictate the form and function of the final assembled structure. The design and self-assembly of discrete multi-component structures rely on recognition between the constituent building blocks. The supramolecular chemistry and self-assembly of these molecules at surfaces are being investigated with atomic force microscopy (AFM), scanning tunneling microscopy (STM) and transmission electron microscopy (TEM).

Synthesis, characterization and self-assembly of photon and electron-sensitive molecules

The target species being synthesized consist of hydrophilic polymer backbones supporting high-density azobenzene side-groups and termination motifs including -NO2 and -CN. These materials are deposited as oriented monolayers on Au/mica supports using the existing KSV-3000 LB instrumentation in Sherbrooke, and characterized using AFM and grazing incidence infrared spectroscopy; trans/cis isomerisations are induced by optical irradiation in the UV/vis regions.

Organic layers

Despite the wide use of graphite electrodes in electrochemistry, there have been few investigations of their surface and electrochemical properties. The objective of this research project is therefore to determine the factors which influence the efficiency, stability, and selectivity of graphite electrodes modified with aryl layers in certain electrochemical processes.