Mathy, Bertrand
[UCL]
(eng)
The Atomic Force Microscope is a powerful tool for probing the surface of a sample at the nanoscopic scale. Indeed it can give information about the sample topography and map various physical or chemical surface properties. But in parallel to these "classical" applications, there exist other very interesting techniques. They include sensing applications in which the adsorption of molecules on the cantilever is quantitatively monitored and surface engineering applications in which the tip is used as a pen to write chemical features on a substrate.
The aim of this thesis was to develop innovative ways to go further in these two series of applications and to improve their performances. The main strategy was to increase the number of reactive sites on the cantilevers in order to interact faster and with more sensitivity. To reach this objective, AFM cantilevers were functionalized with polymer brushes which provide stable surfaces that can contain a large amount of reactive side groups per unit area.
First, the study of the kinetics of (physico)chemical reactions at the
submicrometric scale was undertaken with cantilevers bearing reactive brushes. Two different methods were investigated: the frequency shift method and the deflection method. The first method was based on the fact that the resonance frequency of a lever is inversely proportional to its mass which was increased upon adsorption of analytes by the reactive brushes while the second one was based on the variation of the surface stress of the cantilever upon adsorption of molecules by the reactive brushes.
Second, a surface-confined "click" reaction was catalyzed at the nanoscopic scale with functionalized polymer brushes bearing ligands for metals that were grafted from an AFM tip. The scan speed was a determining parameter and in every case, the patterns were thicker than a monolayer of the grafted molecules. The proposed mechanism of the lithography involves two steps: the formation of crystal seeds by the catalysis of the reaction and the subsequent pi stacking of aggregates that were absorbed in the brush.


Bibliographic reference |
Mathy, Bertrand. Polymer brushes and AFM cantilevers for nanosensing and nanocatalysis. Prom. : Nysten, Bernard ; Jonas, Alain |
Permanent URL |
http://hdl.handle.net/2078.1/110233 |