Selective Homoepitaxial Growth of ZnO Layers on c(+)-Surface by Solvothermal Reaction in Water-Ethylene Glycol Solvent.

Solvothermal deposition of ZnO layers on the c(±)-surfaces of ZnO single crystal substrates in a water-ethylene glycol solvent was investigated. Homoepitaxial growth of nanoparticulate layers was observed on the c(+)-surface. The manner of nanoparticle deposition on the c(+)-surface was similar to that of spherical particles precipitated in the solution, in that both grew through the oriented attachment of small particles during the early growth stage. The growth of the nanoparticulate film on the c(-)-surface was much slower than that on the c(+)-surface. After aging, the top surface of the film on the c(+)-surface transformed into a layer of pyramid-like particles so that the base of the pyramids was directed toward the surface. In contrast, randomly oriented pyramidal particles covered the c(-)-surface. Ostwald ripening through dissolution-recrystallization transformed the nanoparticles into pyramid-shaped particles in the latter stage when they were in contact with the solution. The faster growth on the c(+)-surface than on the c(-)-surface and the pyramidal shape of the particles with c(+)-basal plane deposited on the c(±)-surfaces after aging confirmed that the growth of the c(+)-plane was promoted, whereas the growth of {101̅0} and c(-)-planes was inhibited in this solution.

Time-gated luminescence bioimaging with new luminescent nanocolloids based on [Mo6I8(C2F5COO)6]2- metal atom clusters.

Bioimaging and cell labeling using red or near infrared phosphors emitting in the "therapeutic window" of biological tissues have recently become some of the most active research fields in modern medical diagnostics. However, because organic and inorganic autofluorophores are omnipresent in nature, very often the background signal from fluorochromes other than targeted probes has to be eliminated. This discrimination could be available using a time-gated luminescence microscopy (TGLM) technique associated with long lifetime phosphorescent nanocomposites. Here, we report new SiO2 nanostructured particle (50 nm in diameter) embedded luminescent nanosized [Mo6I8(C2F5COO)6]2- metal atom clusters (1 nm in diameter), successfully prepared by the microemulsion technique. This combination provides new physical insight and displays red emission in biological based solution under UV-Vis excitation with long lifetimes of around 17 and 84 µs. Moreover, the nanoparticles can be internalized by cancer cells after surface functionalization by transferrin protein and clearly imaged by TGLM under excitation at 365 nm. The nanocomposites have been mainly characterized by scanning and transmission electron microscopies (SEM and HAADF-STEM), UV-Vis and photoluminescence (PL) spectroscopies.

Functional silica nanoparticles synthesized by water-in-oil microemulsion processes.

Water-in-oil (W/O) microemulsion is a well-suitable confined reacting medium for the synthesis of structured functional nanoparticles of controlled size and shape. During the last decade, it allowed the synthesis of multi-functional silica nanoparticles with morphologies as various as core-shell, homogenous dispersion or both together. The morphology and properties of the different intermediates and final materials obtained through this route are discussed in the light of UV-Vis-NIR spectroscopy, dynamic light scattering (DLS) and X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and magnetometer SQUID analysis.