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.

ATRC is a new ligth scattering technique that measures by holography the field amplitude scattered by a sample, and analyze its spatial correlations. ATRC outperforms other light scattering techniques like DLS, DWS and TRC. Dynamic light scattering (DLS) [1], diffusing wave spectroscopy (DWS) [2] and time resolved correlation (TRC) [3] are well-established techniques for investigating the dynamics of a wide variety of systems in physics, chemistry, biology , and medicine. DLS and DWS consider the intensity time fluctuations of the scattered light, and study samples, whose dynamics are homogeneous in time. TRC considers the spatial fluctuations, and is able to study slow or temporally heterogeneous dynamics. We propose, in this work, to replace the TRC multi pixel detector by an holographic one, and to consider the spatial fluctuations of the field complex amplitude E as a new quantity of interest. We introduce thus a new tool called ATRC for Amplitude Time Resolved Correlation, which outperforms TRC and open new perspectives. Fig. 1. (a) TRCA typical setup. (b) Reconstructed image of a nanocomposite sample. Fig.1 (a) shows a simplified diagram of the TRCA setup. The sample S is illuminated by the laser beam L1. The light scattered by the sample is split by the beam splitter BS into two imaging paths, corresponding to cameras C1 and C2. Lens L made the image of the sample S on C1, which records the light intensity image I of S. On the other hand, the camera C2 records the interference pattern (i.e. the hologram) of the scattered light with the reference laser light L2, and the complex amplitude image E of S is calculated by holographic reconstruction. The optimize the detection sensitivity [4], holography is heterodyne [5] and off-axis. Fig.1 (b) shows the intensity reconstructed image (I = |E| 2) of a 30 × 10 mm 2 Styrene-Butadiene/Silica nanocom-posite sample, which is observed in reflection. Because 2 phase detection is used, both the +1 and-1 image of the sample are seen (right and left hand side images of Fig.1 (b)). To analyze the dynamic of the sample, TRC considers

A microscopic technique based on digital holography is proposed to investigate blood microcirculation and vascular development in model organisms such as zebrafish larvae. Recent achievements in 3D imaging of blood flow in vessels are presented.

Gliadins are edible wheat storage proteins well known for their surface active properties. In this paper, we present experimental results on the interfacial properties of acidic solutions of gliadin studied over 5 decades of concentrations, from 0.001 to 110 g/L. Dynamic pendant drop tensiometry reveals that the surface pressure  of gliadin solutions builds up in a multistep process. The series of curves of the time evolution of collected at different bulk protein concentrations C can be merged onto a single master curve when  is plotted as a function of t where t is the time elapsed since the formation of the air/water interface and  is a shift parameter that varies with C as a power law with an exponent 2. The existence of such time-concentration superposition, which we evidence for the first time, indicates that the same mechanisms govern the surface tension evolution at all concentrations and are accelerated by an increase of the bulk concentration. The scaling of  with C is consistent with a kinetic of adsorption controlled by the diffusion of the proteins in the bulk. Moreover, we show that the proteins adsorption at the air/water interface is kinetically irreversible. Correlated evolutions of the optical and elastic properties of the interfaces, as probed by ellipsometry and surface dilatational rheology respectively, provide a consistent physical picture of the building up of the protein interfacial layer. A progressive coverage of the interface by the proteins occurs at low . This stage is followed, at higher , by conformational rearrangements of the protein film, which are identified by a strong increase of the dissipative viscoelastic properties of the film concomitantly with a peculiar evolution of its optical profile that we have rationalized. In the last stage, at even higher surface pressure, the adsorption is arrested; the optical profile is not modified while the elasticity of the interfacial layer dramatically increases with the surface pressure, presumably due to the film ageing.