Aqueous dispersions of graphene-derived monolayers form liquid crystal at rather low concentrations due to the high aspect ratio of these flakes [1,2]. If graphene oxide dispersions are easily obtained in water, reduced graphene oxide necessitates the use of surfactants [3]. Preparing organized materials and thin films from these dispersions then requires a good control of the liquid crystal ordering during the deposition and the drying of the films.The flakes easily align at high shear [4,5], which has allowed us to complete previous optical characterizations of the various graphene layers (birefringence and linear dichroism). However at low shear or under small dispalcements, thin films often show peculiar patterns (such as the periodic textures shown in Fig.1). We have shown how to create and stabilize large-sized periodic textures. The patterns have been characterized under optical and electronic microscopies. Their stability can be explained by the competition between the anchoring field of the substrate and the presence of a yield stress resulting from the peculiar elastic and rheological properties of the graphene oxide liquid crystals. Our results also clarify why long-standing hypotheses on the presence of exotic phases [1] at large concentrations are present in the literature.References[1] Z. Xu, C. Gao Nat Commun., 2, 571 (2011).[2] C. Zakri et al., Phil. Trans. A, 371, 20120499 (2013).[3] C. Zamora et al, J. Phys. Chem. Lett. 3, 2425 (2012).[4] P. Poulin et al, Proc Natl Acad Sci USA, 113, 11088 (2016).[5] S-H Honga, T.Z. Shena and J. K. Songa, Liquid Crystals, 42, 261 (2015)

Thin and ultrathin metal coatings are increasingly required by the electronics and optics industries onall types of substrates. However, the adhesion of noble metals is very poor on non-metallic substrates like glass,other oxide materials and polymers. By contrast, CVD graphene has a strong adhesion energy (~0.31-0.45 J.m-2depending on the number of layers) on glass [1]. On the other hand, graphene oxide (GO) was recently shown topromote adhesion of ZnO nanoparticles and subsequent ZnO films on glass or silicon substrates [2].In this work we use GO/Au nanoparticles (NP) composite thin films as bifunctional materials to bothpromote adhesion on glass and assist the deposition of copper in electroless wet industrial coating processes. Wediscuss the influence of the NP density, surface treatment and deposition parameters on the homogeneity andadhesion of the GO/Au NP and copper layers.[1] S. P. Koenig, N. G. Boddeti, M. L. Dunn, and J. S. Bunch, 2011, Nat. Nano. 6, 543‑546[2] Q. Ma, X. Zhu, D. Zhang, and S. Liu, 2014, J. Mater. Chem. C 22, 8956‑8961

In this work, we explore the preparation and deposition of graphene oxide (GO)-metal (gold and palladium) nanoparticles (NPs) composites as thin films via wet routes. The properties of such films are examined, in view of Surface Enhanced Raman Spectroscopy (SERS) applications and as adhesion promoter thin films. It has been indeed shown that the encapsulation of metal NP within a few layers of graphene greatly improves the stability, reproducibility and sensitivity of SERS effect [1]. On the other hand, graphene oxide films decorated with metal nanoparticles are good non-etching adhesion promotors candidates for electroless deposition of metal thin films on non-metal substrates like glass or polymers [2, 3]. We discuss the preparation of the suspensions and the parameters (GO dispersion concentration, withdrawal speed and immersion time, functionalization of the substrates) which permit a good control of the deposition by dip-coating. The structure of the resulting thin films is characterized by Atomic Force Microscopy (AFM), Phase Shifting Interferometry (PSI) and Raman spectroscopy to determine the topography, thickness and homogeneity of the deposited layers. Their SERS and adhesion properties are then discussed.References[1] Y. Liu, Y. Hu, and J. Zhang, J. Phys. Chem. C, 2014, 1187, p. 8993‑ 8998.[2] S. P. Koenig, N. G. Boddeti, M. L. Dunn, and J. S. Bunch,2011, Nat. Nanotechnol.,6, p. 543‑ 546.[3] Q. Ma, X. Zhu, D. Zhang, and S. Liu, 2014, J. Mater. Chem. C,22, p. 8956‑ 8961.

We explore the preparation and use of graphene dispersions and graphene-nanoparticles composites viawet routes in order to create organized thin films (for passivation, adhesion and design of SERS substrates, seeFig.) At large concentrations, the liquid crystal ordering is an opportunity to spontaneously organize the materials.At lower concentrations, a special care has to be taken during the deposition of the thinnest films.In this work, we have focused on the design and the characterization of thin layers made of graphene oxide andgold nanoparticles (GO/AuNps) for their Surface Enhanced Raman Spectroscopy (SERS) properties. The objectivehere is to establish the main rules that control (during the deposition) the structure of the films and their resultingSERS properties. We have used various techniques such as dip-coating, spin coating with varying parameters, aswell as surface functionalization before deposition. The thin films have been characterized by AFM and theirperformance have been tested with Raman spectroscopy.

Graphene oxide dispersions are easily obtained in water. Due to the high aspect ratio of the flakes, liquid crystalsthen forms a nematic phase at moderate concentrations [1,2], which allows to design various composites withnanoparticles. Preparing organized materials and thin films from these dispersions however requires a good controlof the liquid crystal ordering during the deposition and the drying of the films.Here we have focused on mechanical instabilities that are frequently observed in thin graphene liquid crystallayers, when they are submitted to weak constraints. We have shown how to create and stabilize large-sizedperiodic textures (millimeter scale, see fig.1). The patterns have been characterized under optical and electronicmicroscopies. They result from the peculiar elastic and rheological properties of the graphene oxide liquid crystals.Our results also clarify why long-standing hypotheses on the presence of exotic phases [1] at large concentrationsare present in the literature.

Dynamics in stretched nanocomposites

As an opening lecture to the French-Swedish neutron scattering school held in Uppsala (6th to 9th of December 2016), the basic concepts ofboth soft matter science and neutron scattering are introduced. Typical soft matter systems like self-assembled surfactants in water, microemulsions, (co-)polymers, and colloids are presented. It will be shown that widely different systems have a common underlying physics dominated by the thermal energy, with astonishing consequences on their statistical thermodynamics, and ultimately rheological properties – namely softness. In the second part, the fundamentals of neutron scattering techniques and in particular small-angle neutron scattering as a powerful method to characterize soft matter systems will be outlined.