Ziyong Cheng

Patterning and luminescent properties of nanocrystalline Y2O3:Eu3+ phosphor films by sol–gel soft lithography

Nanocrystalline Y2O3:Eu3+ phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu3+ showed its characteristic emission in crystalline Y2O3 phosphor films due to an efficient energy transfer from Y2O3 host to them. Both the lifetimes and PL intensity of the Eu3+ increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+ were determined to be 5 mol%.

Fabrication of self-assembled palladium nanosheets using layered organic/inorganic hybrid as the template

In this paper, a simple route to the fabrication of palladium nanosheets is described. The interaction of palladium chloride (PdCl2) and n-octylamine salt resulted in the formation of a quasi-perovskite-type composite with a layered structure on a molecular scale. This composite can be employed as a template for preparing ultrathin Pd nanosheets when a {PdCl4}2− network is reduced in situ by hydrogen in toluene. The x-ray diffraction results indicate that the resulting Pd nanosheets are highly ordered, and they are confined inside the organic matrix as evidenced by high resolution transmission electron microscopy. These Pd nanosheets can be reorganized into layered structures in non-polarized organic solvent when the ordered structure is destroyed. This method of preparing Pd nanosheets is expected to be applicable to other layered organic/inorganic perovskite systems for obtaining the corresponding metal nanosheets.

Dewetting behavior of polystyrene film filled with (C6H5C2H4NH3)2PbI4.

The dewetting behavior of thin (about 30 nm) polystyrene (PS) films filled with different amount of (C(6)H(5)C(2)H(4)NH(3))(2)PbI(4) (PhE-PbI(4)) on the silicon substrate with a native oxide layer was investigated. For different additive concentrations, PhE-PbI(4) showed different spatial distributions in the PS films, which had a strong influence on the film wettability, dewetting dynamics, and mechanism. With 0.5 wt % additive, PhE-PbI(4) formed a noncontinuous diffusion layer, which caused a continuous hole nucleation in the film. With about 1 wt % additive, a continuous gradient distribution layer of PhE-PbI(4) formed in the film, which inhibited the dewetting. When the concentration is higher (2 wt %), large PhE-PbI(4) aggregates, in addition to the PhE-PbI(4) continuous layer, formed in the film. These large aggregates (larger than radius of gyration of PS) migrated to the interface, resulting in the hole nucleation and eventually the complete dewetting of the film.

Patterning organic luminescent materials by solvent-assisted dewetting and polymer-bonding lithography

A combined approach of solvent-assisted dewetting and polymer-bonding lithography was employed to pattern the luminescent materials on the polymer-coated substrate. In saturated solvent vapor atmosphere, light-emitting material films (e.g., Alq3∕PVK,PhE-PdI4∕PS) on the polydimethylsiloxane mold could dewet and form isolated micropatterns directed by the mold. Then, the microstructures were transferred to the polymer-coated substrates based on the surface adhesion to generate the useful isolated and well-defined light-emitting patterns. The optical property of Alq3∕PVK remains almost unaffected in the patterning process. The combined approach is applicable to other organic functional materials and polymer-coated surfaces with different physical and chemical properties and has potential applications in organic microelectronics fabrication.