Papers by Keyword: Core-Shell

Abstract: Core-shell nanomaterials have been one of the most attracting research targets in the field of nanoscience and technology due to the multiple functionalities contributed from different components. In this paper, we report a facile solution synthetic method for the preparation of gold-nickel phosphide core-shell nanoparticles that have a near-spherical morphology and a size of ~20 nm. Transmission electron microscopy along with energy dispersive X-ray spectroscopy analyses reveals a core-shell structure consisting of gold core and nickel phosphide shell. The optical absorption data show that the surface plasmon resonance band of gold in the visible range is greatly decreased by coating nickel phosphide shell. The result of magnetic measurement reveals that the as-prepared core-shell nanoparticles basically exhibit paramagnetic characteristics. The obtained gold-nickel phosphide core-shell nanoparticles can be applied in application fields such as catalysis.

Abstract: FeSi/SiO₂ Core-shell nanoparticles were synthesized by DC arc-discharge approach and annealing process. The products were characterized by SEM, TEM, EDX, XRD and VSM. As-prepared FeSi/SiO₂ Core-shell nanoparticles have the diameter of 40-100 nm and the thickness of the SiO₂ shell is about 20 nm. The growth mechanism based on the crystallographic and thermodynamic theory was explained. Magnetic characterization was carried out and the results showed that the FeSi/SiO₂ Core-shell nanoparticles exhibited superparamagnetism characteristic at room temperature.

Abstract: Nanostuctured Tb³⁺-doped Gd₂0₃ particles were synthesized from chloride precursors GdCl₃ and TbCl₃ by NaOH addition in a polyol medium. Then, Gd₂0₃: Tb³⁺ particles were encapsulated in a polysioxane shell by being immersed in a mixed solution of APTES and TEOS. Effect of NaOH quantity on size and luminescent property of obtained core-shell nanoparticles was studied. The result shows that the size of nanoparticles increased with the increase of NaOH quantity from 30% to100% of stoichiometry. The emission intensity of core-shell nanoparticles increased with the size of particles due to the enhancement of energy transfer between core and shell.

Abstract: ZnMoO₄:Tb³⁺ phosphor layers were grown on monodisperse SiO₂ particles through a simple sol-gel method, resulting in the formation of core-shell structured SiO₂@ZnMoO₄:Tb³⁺ sub-microspheres. The resulting SiO₂@ZnMoO₄:Tb³⁺ core-shell particles were characterized by powder X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM) and photoluminescence(PL). SEM and TEM analysis indicates that the obtained sub-microspheres have a uniform size distribution and obvious core-shell structure. SiO₂@ZnMoO₄:Tb³⁺ sub-microspheres show strong green emission under ultraviolet(275nm) illumination and the emission spectra are dominated by a ⁵D₄→⁷F₅ transition of Tb³⁺(543nm,green) from the ZnMoO₄:Tb³⁺ shells. The optimum concentration for Tb³⁺ was determined to be 5 mol% of Zn²⁺ in ZnMoO₄ host shells.

Abstract: Positive temperature coefficients of resistivity (PTCR) have been realized in lead free Na_0.5Bi_0.5TiO₃ (NBT) based ceramics by (LiCe) addition. The modulations on their volumes have been obtained continuously in the wide temperature range of 50-479 °C. X-ray diffraction and scanning electron microcopy results display that second-phase adulterants exit on NBT grain boundaries, and even create core-shell structures around NBT grains with the increment of additions. Impedance analysis reveals that electrically heterogeneous structures of grain and grain boundaries have contributions to the PTCR effects of NBT-based ceramics, especially for core-shell structure. All results indicate NBT-based system can be used for thermistor applications at high temperature.

Abstract: Soft-core/hard-shell polyacrylate latex with different cross-linking degree and shell thickness were prepared by semi-continuous seed emulsion copolymerization .The size, size distribution and morphology of latex particles were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The properties of plastisol were investigated by testing their dynamic viscoelasticity and storage stability as well as the mechanical properties. The results showed that the latex particles always keep regular spherical structure throughout the polymerization process; Dynamic viscoelasticity of plasticized system with different cross-linking degree however had little changed. The mechanical properties of the plastigels could be improved by increasing the thickness of shell.

Abstract: As a new light-emitting material, quantum dot having the advantages of other materials that can not be replaced. It is not only the fluorescence quantum yield, and light stability. Therefore, we use CdSe core-shell structure of the quantum dot LED devices as the electron-hole recombination layer. In this paper, we synthesized emission peak is located at 588nm CdSe core-shell quantum dots, and made array display LED devices with ZnO as the electron transport layer.

Abstract: Latexes with poly(butyl methacrylate-stryrene-acrylonitrile) rich in the shell and PDMS rich in the core were prepared based on microemulsion polymerization. Vinyl monomers were introduced to generate slightly crosslinked particles, then, etamethyltetraeyelosiloxane（D4）was added slowly to form the core. In the process, internal resistance must be overcome when the D4 entered into the polymer to form the core. The compatibility between the two polymer phases was changed by introducing acrylonitrile and the effect of different methods on forming latex particles was discussed.

Abstract: The core-shell polyurethane-acrylate(PUA) emulsion containing fluorine and silicon in the core was synthesized by “one-pot” emulsion polymerization in the presence of castor oil-based polyurethane without traditional emulsifier, using methyl methacrylate (MMA), butyl acrylate (BA) as the main monomers, dodecafluoroheptyl methacrylate (G04), γ-methacryloxy propyl trimethoxyl silane (KH-570) as the functional monomers. The structure and properties of the fluorinated-silicated PUA and their films were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrum (FT-IR) and contact angle testing. The results showed that fluorine and silicon monomers had effectively copolymerized with acrylic monomers and a core-shell structure in the latex was formed. The water contact angle for film-air interface is 92.5^o, and the cetane contact angle for film-air interface is 47.5 ^o.

Abstract: SiO₂-coated Fe nanocomposites (Fe@SiO₂) were prepared without using any of surface-coupling agents. The outer SiO₂ coating offered new possibilities for the control of Fe core agglomeration. In order to investigate Cr (VI) reduction in open systems that simulated subsurface conditions, sand column experiments were conducted. When 10 mg/L of Cr (VI) was injected into the columns, the removal efficiencies of Cr (VI) by the Fe@SiO₂ were 65 mg Cr/g Fe. The transport tests in deionized water-saturated sand columns indicated that 88.03% of Fe@SiO₂ was eluted. Nonetheless, the mobility of Fe@SiO₂ decreased when encountering 10 mmol/L Na⁺ and Ca²⁺. Presumably, 15 mg/L humic acid enhanced the mobility of Fe@SiO₂. Overall, the results of this study indicate that Fe@SiO₂ has the potential to become an effective reactive material for in situ groundwater remediation.