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B. Basnar, M. Litschauer, M.-A. Néouze:
"Imidazolium units to form ionic nanoparticle networks";
Poster: ILMAT 2011 - Ionic Liquids derived Materials, Institut Français Vienna, Austria; 05.12.2011 - 06.12.2011; in: "ILMAT 2011 - Ionic Liquids derived Materials", (2011).

New hybrid inorganic-organic materials were recently reported based on the covalent linking of metal oxide nanoparticles, silica or titania, by means of imidazolium bridging units. These hybrid materials are referred as INN, which stands for ionic nanoparticle networks.
For many applications, such as gas separation membranes, the processing of the material into thin films is necessary. To this end, we recently successfully developed a layer-by-layer deposition method for INN. The deposition of the film started with the immobilization of a nanoparticle monolayer on a silicon substrate.
A silicon surface is modified with a trimethoxysilylpropyl imidazole monolayer and titanium dioxide nanoparticles are functionalised with chloropropyl phosphonic acid molecules. These two groups can react in a nucleophilic substitution reaction.
This chemical reaction results in the formation of an aromatic imidazolium moiety as the covalent binding group between the surface and the nanoparticles. The networking reaction can be considered as a green, "click-chemistry-like" reaction. Indeed, the reaction occurs in alcohol or water at room temperature; moreover no side products are formed during the reaction.
In order to investigate the formation of a nanoparticle monolayer based on the above described material system, we have employed several different techniques. The first characterisation was performed using spectroscopic ellipsometry. In this way we were able to determine the average layer thickness. In addition to ellipsometry, atomic force microscope (AFM) measurements were performed. These two methods allowed investigating the surface coverage which showed, indeed, the formation of a relatively closely packed monolayer. The AFM also provided a means to investigate the mechanical stability of the surface by performing lateral force microscopy measurements. Investigation of the chemical nature of the bond was attempted by x-ray photoelectron spectroscopy. Both the imidazole- and chlorogroups were easily distinguishable.
With this layer-by-layer deposition method, nanolithography was performed and thin films with up to 6 layers were fabricated

Projektleitung Marie-Alexandra Néouze:
Ionische Verknüpfung von Nanopartikeln