To demonstrate the fabrication of inorganic electroluminescent (EL) devices using perovskite-type oxide phosphors by electrophoretic deposition (EPD), AZrO3:RE (A = Ca, Sr, Ba; RE = Eu, Tb) were synthesized by the polymerized complex method. AZrO3:Eu showed orange or red emissions and AZrO3:Tb showed blue-green or green emissions depending on their crystal structures. The emission intensity was found to be enhanced by introducing strains to the host matrices by Mg codoping or alloying. Inorganic EL devices prepared by EPD using BaZrO3:Eu and SrZrO3:Eu as the phosphor layers showed orange and blue emissions that were observable under room light, respectively, which is the first observation of EL emission from the devices prepared by EPD to the best of our knowledge. The combination of perovskite-type oxide phosphors and EPD was found to be a promising way to fabricate inorganic EL devices.
We investigated the individual properties of various polyion-coated bubbles with a mean diameter ranging from 300 to 500 nm. Dark field microscopy allows one to track the individual particles of the submicron bubbles (SBs) encapsulated by the layer-by-layer (LbL) deposition of cationic and anionic polyelectrolytes (PEs). Our focus is on the two-step charge reversals of PE-SB complexes: the first is a reversal from negatively charged bare SBs with no PEs added to positive SBs encapsulated by polycations (monolayer deposition), and the second is overcharging into negatively charged PE-SB complexes due to the subsequent addition of polyanions (double-layer deposition). The details of these phenomena have been clarified through the analysis of a number of trajectories of various PE-SB complexes that experience either Brownian motion or electrophoresis. The contrasted results obtained from the analysis were as follows: an amount in excess of the stoichiometric ratio of the cationic polymers was required for the first charge-reversal, whereas the stoichiometric addition of the polyanions lead to the electrical neutralization of the PE-SB complex particles. The recovery of the stoichiometry in the double-layer deposition paves the way for fabricating multi-layered SBs encapsulated solely with anionic and cationic PEs, which provides a simple protocol to create smart agents for either drug delivery or ultrasound contrast imaging.
We study the early stage behaviour of nucleus growth in a vacuum-deposited thin film. Solving a stationary diffusion equation with boundary conditions on each nuclei periphery, we derive for the first time the multi-nuclei growth equation. This equation is found to express the cooperative interactions among nuclei via the diffusion field. We also examine a linear stability of a growing nucleus €or many nuclei systems.
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