Corinne Chanéac

Communications: Short-range dynamics of a nematic liquid-crystalline phase

Using x-ray photon correlation spectroscopy, we studied the dynamics in the nematic phase of a nanorod suspension. The collective diffusion coefficient in the plane perpendicular to the director varies sharply with the wave vector. Combining the structure factor and the diffusion coefficient, we find that the hydrodynamic function of the phase decreases by more than a factor of 10 when going from length scales comparable to the interparticle distance toward larger values. Thus, the collective dynamics of the nematic phase experiences strong and scale-dependent slowing down, in contrast with isotropic suspensions of slender rods or of spherical particles.

Temperature sensing using a Cr:ZnGa2O4 new phosphor

The luminescence emission of a thermographic phosphor based on trivalent chromium doped ZGO (ZnGa2O4) bulk as well as nanoparticles is here reported. This material has a strong temperature dependence on the optical features such as ratio of their emission bands, bandwidths, bands position as well as the lifetime decay of the Cr3+. This makes this material well suitable as temperature sensor. ZnGa2O4 (ZGO), a normal spinel, exhibits a high brightness persistent luminescence, when doped with Cr3+ ions and shows an emission spectrum centered at 695 nm. At the nanometric scale, ZGO is used for in vivo imaging with a better signal to background ratio than classical fluorescent NIR probes. In this work we investigate the ability of the host to be a new thermographic phosphor. Several optical features are investigated in a broad temperature range (10 K-700 K). A comparison between bulk material and nanoparticles is introduced. The obtained results could be used to determine the optimal design parameters for sensor development.

Persistent luminescence in ZnGa2O4:Cr3+ transparent glass-ceramics

Given the increasing demand for optical in vivo bioimaging materials, persistent luminescence in the red/near infrared range is receiving particular attention. Within this work, several elaboration ways of ZnGa2O4:Cr3+, respectively by solid state, by microwave assisted hydrothermal synthesis and by glass crystallization have been carried out. Structural analysis shows that all methods lead to pure spinel structure. Powder micrometric material is obtained by solid state reaction while nanoparticles are obtained by the two other methods. In the case of the glass-ceramics process, the nanocrystals obtained are trapped in a glassy matrix. This kind of elaboration leads to nanoparticles with lower amount of defects, no surface contact with air and an increase signal of the persistent luminescence compared to disperse nanoparticles. These good persistent luminescence properties are well correlated to thermoluminescence glow curves analysis. Moreover, such glass ceramics can be used as a good tool to study more deeply the persistent luminescence process of nanoparticles in a transparent environment and samples are easier to characterize.

Study on the persistent luminescence of diopside nanotracers CaMgSi2O6: Eu2+ , Mn2+, Pr3+

We present a study on diopside nanotracers with persistent luminescence properties in the red-near IR range for small animal imaging. In this paper we have focused our attention on improving the persistent luminescence of diopside nanoparticles doped with transition metal and lanthanide ions. Earlier study showed that Pr3+ is the most suitable Ln3+ electron trap in Eu2+, Mn 2+ doped diopside lattice. Here, we report an optimization of both chemical composition of CaMgSi2O6 matrix and Eu, Mn, Pr doping elements to improve persistent luminescence. These new inorganic persistent luminescent nanoparticles (i-PLNPs) emit in the red-near infrared range for several hours and can master the difficulties due to the biological environment.

Optical filter based on Fabry-Perot structure using a colloidal suspension of goethite ([alpha]-FeOOH) nanorods as electro-optic material

We have investigated the feasibility of optical tunable filters based on a Fabry-Perot etalon that uses a suspension of goethite (α-FeOOH) nanorods as electro-optic material for application in optical telecommunications in the near IR range. These synthetic nanoparticles have a high optical anisotropy that give rise to a very strong Kerr effect in their colloidal suspensions. Currently, these particles are dispersed in aqueous solvent, with pH2 to ensure the colloidal electrostatic stability. However, the high conductivity of these suspensions requires using high-frequency electric fields (f > 1 MHz), which brings about a high power consumption of the driver. To decrease the field frequency, we have changed the solvent to ethylene glycol which has a lower electrical conductivity than the aqueous solvent. We have built a Fabry-Perot cell, filled with this colloidal suspension in the isotropic phase, and showed that a phase shift of 14 nm can be obtained in a field of 3V/μm. Therefore, the device can operate as a tunable filter. A key advantage of this filter is that it is, by principle, completely insensitive to the polarization of the input light. However, several technological issues still need to be solved, such as ionic contamination of the suspension from the blocking layers, and dielectrophoretic and thermal effects.

Interaction of TiO2 nanoparticles with proteins from aquatic organisms: the case of gill mucus from blue mussel

AbstractTo better understand the mechanisms of TiO2 nanoparticle (NP) uptake and toxicity in aquatic organisms, we investigated the interaction of NPs with the proteins found in gill mucus from blue mussels. Mucus is secreted by many aquatic organisms and is often their first line of defense against pathogens, xenobiotics, and other sources of environmental stress. Here, five TiO2 NPs and one SiO2 NP were incubated with gill mucus and run out on a one-dimensional polyacrylamide gel for a comparative qualitative analysis of the free proteins in the mucosal solution and the proteins bound to NPs. We then used nanoscale liquid chromatography coupled with tandem mass spectrometry to identify proteins of interest. Our data demonstrated dissimilar protein profiles between the crude mucosal solution and proteins adsorbed on NPs. In particular, extrapallial protein (EP), one of the most abundant mucus proteins, was absent from the adsorbed proteins. After thermal denaturation experiments, this absence was attributed to the EP content in aromatic amino acids that prevents protein unfolding and thus adsorption on the NP. Moreover, although the majority of the protein corona was qualitatively similar across the NPs tested here (SiO2 and TiO2), a few proteins in the corona showed a specific recruitment pattern according to the NP oxide (TiO2 vs SiO2) or crystal structure (anatase TiO2 vs rutile TiO2). Therefore, protein adsorption may vary with the type of NP.n Graphical abstractProteins with adsorption selectivity as identified from isolated bands