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International audience; Short (

Potassium niobate (KNbO3) nanocrystals exhibiting good second harmonic generation properties were coated with dextran derivatives containing primary amine groups. The surface modification results from attractive electrostatic interaction between the aminodextran molecules and the negatively charged surface of bare KNbO3 nanocrystals. To avoid flocculation, a suspension of KNbO3 nanocrystals was firstly prepared and then added drop-wise to an aqueous solution of aminodextran. The as-prepared hybrid (AD-coated KNbO3) nanoparticles were then characterized by using various techniques including transmission electron microscopy (TEM), infrared analysis (FTIR), dynamic light scattering (DLS) and zeta potential measurements as a function of pH of the dispersion medium. Then, the prepared AD- coated KNbO3 nanoparticles were evaluated in vitro diagnostic application as biomarker for non-tumor lung-derived human cells. The obtained results showed that the aminodextran-coated KNbO3 nanoparticles were efficiently bound to the non-tumor lung-derived human cells, which was proved by using a commercial Nikon multi-photon imaging platform. In addition, AD-coated KNbO3 nanoparticles showed good optical contrast for the investigated cells, and consequently they can be efficiently used as contrast agents in the bio-imaging diagnostic domain.

International audience; ABSTRACT: Spherical nanocrystals of iron iodate (Fe(IO3)3) as well as different hierarchically organized hybrid superstructures are synthesized at 80 °C from AOT-based water-in-oil microemulsions. For a fixed reaction time of 2 h, initial addition of PEG molecules and changes in the water/surfactant molar ratio w allow modification of the interactions between surfactant and PEG molecules at the surface of amorphous precursor particles. At low water content (w = 5.8), adsorption of AOT molecules inhibits the formation of crystallized nanoparticles if the amount of added PEG is too low, whereas spherical nanocrystals are obtained otherwise. In contrast, at a high water content (w = 12.2), SEM and TEM imaging reveal that the aggregation-induced crystallization of amorphous precursors induces the formation of higher-order complex forms. Aggregates of elongated cone-shaped bundles of nanofilaments and, subsequently, quasi-spherical urchin-like microstructures as long as the PEG amount is raised are observed. Significantly, lattice parameter refinements originally demonstrate the key role of AOT in the self-assembly and a homogeneous nucleation, leading to the formation of primary bouquet-like structures, is suggested before further self-assembly results in urchinlike structures. In terms of potential applications, spherical nanocrystals are promising exogenous labels for multiphoton microscopy, whereas higher-order architectures give perspectives in the morphogenesis of new functional materials.