Papers by Keyword: Core-Shell

Abstract: In this study, α-Al₂O₃-CeO₂ core-shell nanoparticles were synthesized from the cerium acetate and the commercial α-Al₂O₃ nanoparticles as the starting materials via a wet chemical method. Poly (acrylic acid) (PAA) as an additive compound was used for the surface modification of alumina nanoparticles. Also, the effects of PAA content, pH value and calcination temperature on the synthesis behavior of α-Al₂O₃-CeO₂ nanoparticles were investigated. The formation of core-shell structure was investigated using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The results indicated that at the PAA=1.5 wt. %, pH=6 and calcination temperature=1150°C (as optimal conditions), the core-shell nanoparticles with alumina core and ceria shell and homogeneous size distribution were synthesized successfully.

Abstract: Hydrogel fiber with spatiotemporal properties such as great aspect ratio, large surface area/volume ratio, orientation and knittability, has been considered as the potential application materials in the field of biomedicine area. On the basis of dynamic-crosslinking-spinning we reported before, a novel GO/PEG-PEGDA core-sheath hydrogel fiber was fabricated continuously. Moreover, uniform rGO-PEGDA hollow fiber was obtain after reduction process. The diameter of core and sheath can be controlled separately by adjusting extrusion rate of core solution and sheath solution, respectively. This novel series GO hybrid hydrogel fibers with core-shell or hollow structure have potential application on nerve and muscle tissue engineering.

Abstract: The NiAl/Cu feedstock powder was prepared by Cu coating on NiAl powder using electroplating technique. The NiAl (NS450, Metco Sulzer) powder was deposited Cu⁺ from CuSO₄ solution at cathode with vary time process (60, 80 and 100 min). The microstructure and element of NiAl/Cu powders were investigated by scanning electron microscope (SEM) and energy dispersion of X-ray (EDX). The morphology of powder were appeared the Cu element holding all of surface NiAl particles. The chemical composition in powder using X-ray diffraction were presented the Cu phase with time process. The phase compounds were presented the Ni, Al and Cu phases. Then, it was appeared the new phase of Cu₂O at 100 min time deposited. Therefore, it was low contentThe EDX analysis was supported the Cu cover on the surface NiAl powder. In SEM micrograph of NiAl/Cu cross-section coating were presented the completed structure coating of thermal spray technicque. In addition, the Cu content was improved melted particles by investigated increased lamellar of materials. The Cu lamella was distributed between Ni layers. It was confirmed that NiAl/Cu feedstock powder was fabricated by simple technique.

Abstract: In this article, the relations between extinction cross section and Gold nanoparticle's parameters such as dimensions have been investigated. In this work, the extinction cross section of the core-shell nanoparticles is analyzed by changing the shell material and its thickness. By this, the interesting results such as shifting resonant peak in optical response are obtained. Moreover, a new model of nanostructure is proposed in which the resonant peak of extinction cross section can be controlled by adding silicon nanoparticles and impurity in the shell. This method can be used for tuning of the scattering properties of the core-shell nanoparticle. In the following, we demonstrate that the effective epsilon properties can be used for tuning of the desired optical response in the combinational structure of the spherical nanoparticles. At the end, the effective relative epsilon is also calculated for the selected structures. The operational frequency band is selected from 300 (THz) to 900 (THz).

Abstract: In this paper carboxylated carbon nanotubes/polypyrrole composite (CNTs/PPy) was synthesized in different surfactants aqueous under sonication. Carboxylated CNTs was synthesized in hydrogen nitrate by ultrasonic method and coated by PPy. The synthesized CNTs/PPy in different surfactants was evaluated by Fourier transform infrared spectrometer (FT-IR) and transmission electron microscope. The FT-IR patterns illustrate that CNTs were successfully doped by PPy. The morphology of CNTs/PPy synthesized showed on the transmission electron microscope images. The composite materials sythesized without surfactant are easy reunited. It is also found the surface of CNTs/PPy synthesized in cetyl trimethyl ammonium bromide (CTAB) is smoother than that in other surfactants. The coating effect is better with thicker coating layer. The higher magnification of HRTEM images show the PPy was deposited directly on the surface of carbon nanotubes. The final products are the ordered coaxial composite with well-defined core-shell structure.

Abstract: Amorphous core-shell Fe-B@SiO₂ submicrospheres with the SiO₂ shell layer of about 18 nm were fabricated via a two-step process. Fe-B submicrospheres were first obtained, and core-shell Fe-B@SiO₂ submicrospheres were subsequently fabricated using TEOs as a Si source through a modified Stöber method. The measurements of the magnetic properties demonstrated that the amorphous core-shell Fe-B@SiO₂ submicrospheres exhibit ferromagnetic behavior at room temperature. The maximum reflection loss reaches −24.8 dB at 11.76 GHz for the absorber with thickness of 2.2 mm. The absorption bandwidth with the reflection loss below −10 dB is up to 14.76 GHz for the absorber with a thickness of 1.5-6 mm and the absorption bandwidth with the reflection loss below −20 dB is up to 6.6 GHz for the absorber with a thickness of 1.8-3.1 mm. Our results demonstrates that the amorphous core-shell Fe-B@SiO₂ submicrospheres obtained in this work are attractive candidate materials for the magnetic and EM wave absorption applications.

Abstract: Controlling the morphology of platinum (Pt)-based nanomaterials is an effective strategy to enhance their catalytic performance for a given reaction. Here we report the syntheses of bimetallic Au-Pt nanomaterials with spherical or dendritic morphologies by a seed-mediated growth method. In this route, the gold (Au) nanoparticles are firstly prepared as seeds in oleylamine, which are subsequently seeded the growth of regular or dendritic Pt shells at different Au/Pt molar ratios. The electrochemical measurements show that the core-shell Au-Pt nanodendrites have better catalytic activity than that of core-shell Au-Pt nanoparticles for methanol oxidation reaction due to their abundant atomic steps, edges, and corner atoms in the branched Pt shells.

Abstract: Indium phosphide (InP) quantum dots (QDs) with luminescence tunable over the entire visible spectrum were prepared by the conventional hot injection method. InP QDs are considered alternatives to Cadmium containing QDs for application in light-emitting devices because of showing similar optical properties to those containing toxic heavy metals. The multishell coating was shown to improve the photoluminescence quantum yield (QY) of InP QDs more strongly than the conventional ZnS shell coating. QY values were more than 60% along with FWHM of 41-73 nm can be routinely achieved, making the optical performance of InP/ZnS/ZnS or InP/ZnS/SiO₂ QDs comparable to that of InP/ZnS QDs. These QDs and the polymer dissolved in the appropriate solvent and deposited by casting to give homogeneous films and showed a good level of dispersion of the QDs within the polymer.

Abstract: Phosphorus-doped p-type ZnS NWs were synthesized by chemical deposition method. The as-synthesized NWs shows obvious p-type conduction with a hole concentration of 8.35 × 10¹⁷ cm^-3. ZnS-Si core-shell nanoheterojunction was fabricated by depositing Si thin film on the surface of ZnS NWs through a sputtering method. The core-shell nanostructure exhibited excellent photoresponse to white light and UV light. Under UV light illumination, a high performance with a responsibility of ~ 0.14 × 10³ AW^-1, a gain of ~ 0.69 × 10³ and a detectivity of ~ 1.2 × 10¹⁰ cmHz^1/2W^-1 were obtained based on the ZnS-Si core-shell nanoheterojunction. This new nanostructure is expected to play an important role in the next-generation optoelectronic devices.

Abstract: W@SiO₂ shielding composite microspheres were prepared by Sol-gel method for the first time. The component and morphology were investigated by Fourier transform infrared (FT-IR) spectra, Transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDX). The results reveal that polyvinylpyrrolidone (PVP) was introduced to the surface of tungsten nanoparticle successfully, and tungsten nanoparticle had been coated with silica. The appropriate hydrolysis reaction time is 3h, core-shell structure W@SiO₂ shielding composite microsphere can be synthesized and free silica decrease sharply. Core element and shell element of W@SiO₂ shielding composite microspheres were proved to be tungsten and silica respectively.