Narrow Results

Hybrid magnetic particles of carbonyl iron (CI) /poly(vinyl butyral) (PVB) with core/shell microstructure (CI-PVB) were prepared in order to enhance the dispersion stability of the magnetorheological (MR) fluids. Since the composite particles of CI-PVB have a lower density than that of the pristine CI particles, they are regarded to improve the sedimentation problem of magnetic particles in the MR fluid when the particles are dispersed in a mineral oil and to make easy redispersion after caking. The PVB coating layers were found to play an important role in the steric repulsion between the relatively large CI particles. Morphology and composition of the CI-PVB particles were observed via SEM and TGA, respectively. Flow properties of both CI and CI-PVB based MR fluids were examined via a rotational rheometer in parallel plate geometry equipped with a magnetic field supplier.

Core–shell structure ${\mathrm{\text{Fe@TiO}}}_2$ was synthesized by sol–gel method. The photocatalytic degradation of methylene blue over the ${\mathrm{\text{Fe@TiO}}}_2$ reached 98% under UV light irradiation within 5 h. The band gap of the core–shell ${\mathrm{\text{Fe@TiO}}}_2$ was found to have a redshift through a sintering treatment. The redshifted ${\mathrm{\text{Fe@TiO}}}_2$ had a good performance of methylene-blue degradation (reaching 85%) under visible light irradiation for 5 h.

In this paper, we report the synthesis of Fe₃O₄ nanoparticles which are resistant to surface poisoning, has been adopted. Fe₃O₄ nanoparticles have been successfully coated with Au in the form of a shell with different sizes (Fe₃O₄/Au Core/Shell). Adjustment of the components’ ratio makes the shell thickness of the core/shell particles tunable. Thus, the presented route yields well-defined core/shell structures of different sizes in the range 15–57nm with varying the proportion of Au noble metal to Fe₃O₄ nanoparticles. The UV-Visible absorption spectra, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) were applied for the characterization of the formed core/shell structures. Moreover, magnetic properties of the core/shell nanocomposites were also studied using Vibrating Sample Magnetometry (VSM).

This paper reports the synthesis and analysis of the characterization results of PbS and PbS/ZnO core/shell nanoparticles embedded in Polyvinyl Alcohol (PVA) matrix. The technique adopted in this work is wet chemical synthesis of PVA/PbS and PVA/PbS/ZnO core/shell nanoparticles. In total, two different sets of samples comprising of nine samples have been synthesized by altering parameters like PVA concentration and shell thickness for the PVA/PbS and PVA/PbS/ZnO samples, respectively. Various characterization techniques are used to analyze the influence of alteration of matrix concentration and shell thickness upon the as-synthesized nanoparticles. The techniques include UV-Vis Spectroscopy (UV-vis), Photoluminescence (PL) Spectroscopy, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Analysis of X-Rays (EDAX) and Transmission Electron Microscopy (TEM). Results of the characterization techniques confirm the formation of nanoparticles of PbS and PbS/ZnO, respectively.

The conversion from one assembly structure to other composite assembly structures is valuable to both theoretical research and actual application in the nano/micromaterials science. In this paper, firstly, the flower-like calcium oxalate assembly structure was synthesized using a supramolecule template; then, through a facile process, the calcium oxalate was converted to a sphere-cluster-like core/shell CaC₂O₄/CaWO₄ nanocomposite assembly structure. The converted product remained the basic structure of original product, and possessed some new optical properties such as fluorescence, etc.

Monodispersed 4.1 nm FePt nanoparticles with narrow size distribution were successfully synthesized by the chemical polyol process with co-reduction of Fe(acac)₃ and Pt(acac)₂ in the presence of 1,2-hexadecanediol as a reducing agent. To achieve hard ferromagnetic behavior with L1₀ phase and face center tetragonal (fct) structure, high temperature annealing is performed. Annealing causes the surfactant surrounding particles to decompose and agglomeration of particles occurs. In the present work, chemically synthesized FePt nanoparticles were coated with nonmagnetic ZnO oxide shell to prevent them from sintering. Coercivity of FePt and FePt/ZnO nanoparticles increases from 5 kOe to 10 kOe and 1.8 kOe to 6 kOe respectively, with the increasing annealing temperatures from 650 to 750°C.

The Fe₃O₄@C core/shell microspheres were fabricated via a two-step process. Fe₃O₄ microspheres were firstly prepared, and Fe₃O₄@C core/shell microspheres were subsequently fabricated using glucose as a carbon source by a hydrothermal route, in which the thickness of the carbon coating was about 20 nm. The resulting products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). The Nitrogen adsorption–desorption isotherms reveal their mesoporous structure and larger BET surface area (62.3 m²g^-1). The Fe₃O₄@C core/shell microspheres possess ferromagnetism and high saturation magnetization (39.2 emu ⋅ g^-1). Bovine hemoglobin (BHb) was used as a model protein to test the adsorption and desorption properties of the Fe₃O₄@C core/shell microspheres. The capacity for BHb adsorption was more than 71.3 mg/g. According to the values obtained in the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay the Fe₃O₄@C core/shell microspheres show a low toxicity. Therefore, the prepared Fe₃O₄@C core/shell microspheres are of great significance for guided site-specific drug delivery.

Core/shell microspheres with functional Mn-doped ZnS microspheres (ZnS:Mn) as core and with nanosilica particles as shell were prepared by a combination of sol–gel and self-templating techniques. The characteristic of this novel method was that the whole process required neither additional surfactant nor stabilizer, which exempted from removing the template and reduced reaction steps compared to the conventional process. The morphologies, structure and particle size distribution of the resulting ZnS:Mn/SiO₂ microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. Surface chemical composition and optical properties were determined with X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy, respectively. In addition, the effects of reaction conditions on the structure and morphologies were investigated. Experimental results indicated that the resulting ZnS:Mn/SiO₂ microspheres were perfectly spherical with distinct core/shell structures, and exhibited stronger fluorescence emission.

Core/shell structured Ni/Fe₃O₄ composites with grain sizes of 200–800 nm were synthesized by using a hydrothermal method. The phase structure, morphology, magnetic and electromagnetic absorption properties of the as-prepared samples were characterized by various analysis techniques. Experimental results revealed that spinel Fe₃O₄ was in situ deposition on the surface of Ni spheres through electrostatic interactions. Moreover, the Ni/Fe₃O₄ mass ratios had a significant influence on the electromagnetic absorption performances. When the mass ratio of Ni/Fe₃O₄ was 1:1, the composites reached an outstanding reflection loss (RL) of $-$48.06dB at 12.96GHz with a thin thickness of 1.8mm. Meanwhile, the effective absorption bandwidth was 5.36GHz (10.72–16.08GHz), covering the X and Ku bands. The enhanced electromagnetic absorption performance of core/shell structured Ni/Fe₃O₄ composites as compared to pure Ni, may be attributed to the multiple interfacial polarization, magnetic exchange coupling resonance and optimal impedance matching. Consequently, core/shell structured Ni/Fe₃O₄ composites would be promising candidates for a wider range of electromagnetic absorption applications.

New materials are of great importance for further development of lithium (Li) ion batteries. This paper reviews the latest development on core/shell structured nanocomposites. Due to different roles of the cores and the shells, the nanocomposites can be tailored to improve their electrochemical performance. Finally, further directions are pointed out.

I–III–VI₂ group compounds, such as CuInSe₂ (CISe), and CuInS₂ (CIS) quantum dots (QDs), are promising for photovoltaic applications by virtue of their excellent photoelectric properties and low toxicity. Considering that the surface of QDs with smaller sizes tends to have a larger density of defect states, inorganic shell layer modification is beneficial to passivate the surface defects and enhance the optical properties and quantum efficiency of QDs. In this study, a novel core–shell structure was constructed by growing a CISe shell layer with a narrower band gap on the surface of CIS nanocrystals with a wider band gap through a green and simple method. The components and properties of the core–shell QDs were analyzed by different characterization methods (XRD, TEM, EDS, UV–Vis, Raman, and fluorescence spectroscopy). The prepared CIS/CISe core–shell QDs with increased size and good coating effects exhibited high absorbance and extended carrier lifetime while showing quantum effects associated with the CISe shell layer, as well as a promising application in the field of solar cells.

Core–shell structure Fe@TiO₂ was synthesized by sol–gel method. The photocatalytic degradation of methylene blue over the Fe@TiO₂ reached 98% under UV light irradiation within 5 h. The band gap of the core–shell Fe@TiO₂ was found to have a redshift through a sintering treatment. The redshifted Fe@TiO₂ had a good performance of methylene-blue degradation (reaching 85%) under visible light irradiation for 5 h.