Colloidal crystals of various thicknesses were obtained using silica particles as basic units and the Langmuir-Blodgett technique as a tool for controlling the thickness. Submicronic silica particles are first synthesized via a sol-gel process and then functionalized with an appropriate coupling agent. After compression at the surface of a Langmuir trough to form a well-organized two-dimensional array, silica particles are transferred onto solid substrates. While repeating the transfer several times, we formed colloidal crystals that were characterized by scanning electron microscopy and UV-visible-NIR spectroscopies. Both techniques show that the sample thickness can be controlled at the layer level whereas the overall crystal quality should be good enough for use in several applications.
Porous golden interiors: Highly organized macroporous metal structures can be synthesized by the preparation of ordered colloidal crystals by the Langmuir–Blodgett technique and subsequent precision electrodeposition controlled by current oscillations. After the assembly of a bioelectrocatalytic chain in the pores, these tailored surfaces can be used as transducers with currents increased by more than one order of magnitude (see diagram).
Raspberrylike hybrid organic-inorganic materials consisting of spherical silica beads supporting smaller polystyrene particles were prepared through a heterophase polymerization process. In a first step, micrometer-sized silica particles were synthesized according to procedures inspired from the literature. In a second step, a poly(ethylene glycol) macromonomer was adsorbed on the surface of the silica beads. Finally, polymerization of styrene was achieved in water with a nonionic surfactant as an emulsifying agent and sodium persulfate as an initiator. Scanning and transmission electron microscopies show that the presence of the macromonomer on the surface of the silica particles is a determining parameter in order to get the raspberrylike morphology.
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