Description of the thesis topic

In addition to their strong potential for applications in the biomedical field, the semi-fluorinated alkanes CnF2n+1CmH2m+1 (denoted FnHm) have specific and surprising two-dimensional self-assembly properties both on the surface of the water and on solid substrate. The association of the two chains, hydrocarbon and fluorocarbon, of very different nature, gives these molecules a pronounced amphiphilic character: one of the chains is lipophilic, the other is lipophobic. Although strictly hydrophobic (no hydrophilic grouping), these molecules form stable two-dimensional monolayers at the water-air interface (Langmuir films). We have shown, by small-angle x-ray surface diffraction measurements (GISAXS), that all the molecules studied (different lengths of the alkyl chain) self-assemble into perfectly monodisperse nanodomains (NDs) forming, under the effect of surface pressure, hexagonal crystal structures. We also deposited the FnHm monolayers on a solid substrate and recover these results (crystal lattice of nanodomains and absence of coalescence) by atomic force microscopy (AFM)
In order to progress in the understanding of the interactions at the origin of these two-dimensional self-assemblies, we propose a study on monolayers of FnHm mixtures by GISAXS (on synchrotron sources) and AFM. In collaboration with the Centre de Biologie Structurale (Montpellier), we developp a Langmuir through equipped with an inverted AFM to probe the monolayer at the air/water interface. Possible segregation or mixing processes in the monolayer could be evidenced from a precise analysis of the observed domain sizes.
A second study will be an attempt in using such hexagonal network to form a large metallic graphene network (by depositing metal in the space between the NDs) or networks of 2D metal pads formed on the domains. Our team has good experience in the formation of hybrid nano-objects (organo-metallic) on the surface of water by photoreduction. The transfer of the films to a solid substrate will allow their characterization by AFM.

L. Bardin, M.-C. Fauré, D. Limagne, C. Chevallard, O. Konovalov, E. J. M. Filipe, G. Waton, M.-P. Krafft, M. Goldmann, P. Fontaine, Long-range organization at the nanoscale of semi-fluorinated alkane monolayers at the air/water interface, Langmuir 27 (22), 13497-13505 (2011)
P. Fontaine, M.-C. Fauré, L. Bardin, E. J. M. Filipe, M. Goldmann, Evidence of interaction with the subphase of water as origin and stabilization of the nanodomain in the semi-fluorinated alkane monolayer at the air/water interface Langmuir 30, 15193-15199 (2014)
L. Bardin, M. C. Fauré, P. Fontaine, E. Filipe, M. Goldmann, "Highly organized crystalline monolayer of a semi-fluorinated alkane on a solid substrate obtained by spin-coating", Thin Solid Films 519, 414-416 (2010)

Work Context

The thesis will be developed within the Institut des NanoSciences de Paris, a joint research unit (MUR 7588) within the framework of the ANR SLAM-AFM. Stays in Montpellier are expected.

Constraints and risks

Experiments on synchrotron sources