Graphene oxide (GO) flakes dissolved in water can spontaneously form liquid crystals. Liquid crystallinity presents an opportunity to process graphene materials into macroscopic assemblies with long-range ordering, but most graphene electronic functionalities are lost in oxidation treatments. Reduction of GO allows recovering functionalities and makes reduced graphene oxide (RGO) of greater interest. Unfortunately, chemical reduction of GO generally results in the aggregation of the flakes, with no liquid crystallinity observed. We report in the present work liquid crystals made of RGO. The addition of surfactants in appropriate conditions is used to stabilize the RGO flakes against aggregation maintaining their ability to form water-based liquid crystals. Structural and thermodynamical studies allow the dimensions of the flakes to be deduced. It is found that the thickness and diameter of RGO flakes are close to that of neat GO flakes.

We introduce the idea of transformation trajectories to describe the evolution of nematic shells in terms of defect locations and director field when the elastic anisotropy and the shell thickness heterogeneity vary. Experiments are compared to numerical results to clarify the exact role played by these two parameters. We demonstrate that heterogeneity in thickness is a result of a symmetry breaking initiated by buoyancy and enhanced by liquid crystal elasticity, and is irrespective of the elastic anisotropy. In contrast, elastic anisotropy--in particular, disfavored bend distortion--drives an asymmetric defect reorganization. These shell states can be both stable or metastable.

The plasma membrane-cytoskeleton interface is a dynamic structure participating in a variety of cellular events. Moesin and ezrin, proteins from the ezrin/radixin/moesin (ERM) family, provide a direct linkage between the cytoskeleton and the membrane via their interaction with phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 binding is considered as a prerequisite step in ERM activation. The main objective of this work was to compare moesin and ezrin interaction with PIP2-containing membranes in terms of affinity and to analyze secondary structure modifications leading eventually to ERM activation. For this purpose, we used two types of biomimetic model membranes, large and giant unilamellar vesicles. The dissociation constant between moesin and PIP2-containing large unilamellar vesicles or PIP2-containing giant unilamellar vesicles was found to be very similar to that between ezrin and PIP2-containing large unilamellar vesicles or PIP2- containing giant unilamellar vesicles. In addition, both proteins were found to undergo conformational changes after binding to PIP2-containing large unilamellar vesicles. Changes were evidenced by an increased sensitivity to proteolysis, modifications in the fluorescence intensity of the probe attached to the C-terminus and in the proportion of secondary structure elements.

We describe a light scattering apparatus based on a novel optical scheme covering the scattering angle range $0.5\dg \le \theta \le 25\dg$, an intermediate regime at the frontier between wide angle and small angle setups that is difficult to access by existing instruments. Our apparatus uses standard, readily available optomechanical components. Thanks to the use of a charge-coupled device detector, both static and dynamic light scattering can be performed simultaneously at several scattering angles. We demonstrate the capabilities of our apparatus by measuring the scattering profile of a variety of samples and the Brownian dynamics of a dilute colloidal suspension.

Confining a smectic liquid crystal between two spherical surfaces results in the formation of a complex defect structure characterized by a set of curvature walls that divide the sphere into crescent domains, causing the undulation of the smectic layers. In this paper, we examine in detail these smectic textures and discuss the various possible origins of the observed patterns.

We show that single-wall carbon nanotubes (SWCNT) can be dispersed as individuals in poly(vinyl alcohol) matrix composites up to concentrations of 1 wt %, as indicated by their strong photoluminescence (PL) signal in the near-infrared all along the processing steps. The alignment of the SWCNT is controlled by hot-stretching of the composite films. We show that orientational order can be described accurately from polarized Raman and PL spectroscopies, in good agreement with a simple affine model, providing their anisotropic absorption is properly taken into account. Similar results are obtained from different excitation laser lines (in the visible and near-infrared), confirming that all nanotubes orient the same way.

In order to investigate the coupling between the degrees of alignment of elongated particles in binary nematic dispersions, surfactant stabilized single-wall carbon nanotubes (CNTs) have been added to nematic suspensions of colloidal rodlike viruses in aqueous solution.We have independently measured the orientational order parameter of both components of the guest-host system by means of polarized Raman spectroscopy and by optical birefringence, respectively. Our system allows us therefore to probe the regime where the guest particles (CNTs) are shorter and thinner than the fd virus host particles. We show that the degree of order of the CNTs is systematically smaller than that of the fd virus particles for the whole nematic range. These measurements are in good agreement with predictions of an Onsager-type second-viral theory, which explicitly includes the flexibility of the virus particles, and the polydispersity of the CNTs.