A novel kind of yolk–shell microspheres was presented in this Letter. First, 250 nm of magnetic Fe₃O₄ nanoparticles was prepared by solvothermal reaction. Then, the Fe₃O₄ particles were coated with Au nanoparticles (AuNPs), SiO₂, and poly(N-isopropylacrylamide) (PNIPAM). After the removal of the SiO₂ layer by etching with HF solution, the yolk–shell microspheres were prepared. Each yolk–shell microsphere had a movable core (Fe₃O₄ self-assembled AuNPs) and temperature-responsive shell (PNIPAM). The yolk–shell structure of these microspheres was confirmed by transmission electron microscopy and Fourier-transform infrared spectroscopy. The catalytic performances of these yolk–shell microspheres were investigated under different environmental temperatures. The results indicated that the reduction from 4-nitrophenol to 4-aminophenol by NaBH₄ was slowed when the temperature was increased because of the hydrophobic and the shrinking sate of PNIPAM shell and the yolk–shell microspheres had a characteristic of temperature switch on/off when the cross-linking degree was about 20%.

Mono-dispersed ceria (CeO₂) hollow nanospheres about 400 nm have been prepared via a facile one-step hydrothermal method, wherein cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) was used as cerium sources with the assistance of polyvinylpyrrolidone (PVP) in the ethylene glycol aqueous solution. X-ray diffraction, X-ray photoelectron spectra, scanning electron microscope, transmission electron microscope, nitrogen adsorption–desorption and Fourier transform infrared results indicate that PVP can improve the dispersion and control the morphology and sizes of CeO₂ hollow nanospheres as a surfactant, and the internal diameter of CeO₂ hollow nanosphere gradually increases with reaction time. Based on the time-dependent experiment, the formation mechanism was proposed and discussed. These CeO₂ hollow nanospheres show an excellent adsorption rate of heavy metal ions for Cr(VI) and the adsorption rate is about 70%. The CeO₂ hollow nanospheres also had exhibited superior performance in the degradation of methyl orange dye.

Hydroxyapatite filled polyetheretherketone functional gradient biomaterials (HA/PEEK FGBm) were fabricated through layer-stacking method and in combination with hot press moulding technology. The influences of total HA content, HA concentration difference between adjacent layers (HCDBAL) and annealing treatment on the tensile properties of HA/PEEK FGBm were investigated. The results indicated that the tensile strength and tensile fracture strain of HA/PEEK FGBm decreased with the increasing total HA content. Contrarily, the tensile modulus of HA/PEEK FGBm increases with the rise of total HA content. The tensile strength and modulus of the HA/PEEK FGBm first increased and then decreased with the rise of HCDBAL. Such change in behaviour was more obvious for the HA/PEEK FGBm with 30% total HA content. Furthermore, the tensile strength and modulus of the HA/PEEK FGBm were obviously improved after annealing treatment.

Assessment of crystallite size and strain of CaCu₃Ti₄O₁₂ (CCTO) with multimodal crystallite size is relatively a challenging task. Various estimation methods (Debye–Scherrer, Williamson–Hall, Rietveld refinement and Variance) are usually gave variation results due to different parameter selections of peaks broadening, for example, average line and integral breath (average and total). The high accuracy of estimation method is essential in order to obtain the best estimated result as close as possible to the observed crystallite size. Therefore, this Letter presents the comparison of estimation methods in determining the crystalline size and strain of CCTO from XRD peak broadening. The result shows that each method gave a different crystallite size as far as various solutions are concern and also depicts that the strain is same. However, Rietveld refinement, Debye–Scherrer and variance methods showed a highly correlated with domain size as observed from transmission electron microscopy analysis, due to an exclusion of the instrumental errors.

A non-enzymatic glucose sensor was developed by using the hollow Co₃O₄ microspheres assembled with nanocrystals as the sensing materials. The hierarchical structured materials were prepared using carbon spheres as sacrificial templates. X-ray diffraction, scanning electron microscope and transmission electron microscopy were employed to characterise the crystal structure and morphology of the hollow microspheres. The results showed that the as-prepared cubic crystalline Co₃O₄ products have a hollow nature, with the shell thicknesses of about 150 nm. The walls of the hollow microspheres were composed of lots of nanocrystals with diameters about 50 nm. The Co₃O₄ hollow microspheres displayed superior electrochemical activity used as non-enzymatic glucose sensors. The high linearity between catalytic current density and glucose concentration was obtained in the range of 2 μM–1.48 mM with a sensitivity of 68.77 μA mM⁻¹cm⁻². More importantly, the interference from the commonly interfering species such as L-valine, urea, L-proline, NaCl and L-lysine can be effectively avoided. The high sensitivity, low detection limit and good selectivity indicated that the hollow Co₃O₄ microsphere is a promising no-enzymatic glucose sensor material for practical application.

A micropin array heatsink with high heat removal capacity for its optimised pin height and inlet–outlet positions is presented. Computational fluid dynamics simulation indicates pin height has a big impact on the pressure difference and heat removal capacity. A decrease of 2.67°C of the maximum temperature was achieved when pin height increased from 200 to 500 µm. Meanwhile with the proper pin height, the different positions of inlet and outlet that the maximum temperature decreases 13.89°C, the best design compared with the worst design among 63 samples under the same working condition. The two typical samples were fabricated and tested through micromachining technology and an infrared imaging testing system. Experiment result preferably matches with the simulation result of the same variation trend of 5.8°C. The positions of inlet and outlet were proved to play an important role in enhancing the heat removal capacity of the micropin array heatsink.

Cadmium telluride (CdTe) nanowires were grown on silicon substrate (100) by thermal evaporation method. The synthesised CdTe nanowires were characterised by X-ray diffraction, field emission scanning electron microscope, energy-dispersive analysis of X-ray, and photoluminescence techniques. The field emission characteristics have been investigated at room temperature. The J–E and I–t characteristics were measured in a planar diode configuration at the base pressure of 1 × 10⁻⁸ mbar. Turn-on field defined for the emission current density of 0.1 µA/cm² has been found to be 2.2 V/µm and on the application of high applied electric field of 7.8 V/µm maximum current density of 210 µA/cm² has been achieved. The I–t measurement has been studied at the preset of 1 µA emission current for the duration of 3 h. Overall nature of emission current has been seen to stable for duration of the measurement. To the best of the authors’ knowledge, this is a first report on field emission study of CdTe nanowires.

Core–shell nanosized polymer particles with poly(butyl acrylate) (PBA) as core and poly(methyl methacrylate) (PMMA) as shell were synthesised via a semi-continuous two-stage microemulsion polymerisation. A series of experiments were conducted to investigate the maximum solid content of the microemulsion under different surfactant/monomer ratios, and it was found that the maximum solid content could reach around 43.73% with minimum surfactant/monomer at only 5.25 wt%. The particle samples were characterised by proton nuclear magnetic resonance (¹H-NMR), scanning electron microscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. ¹H-NMR and TEM results revealed that PBA/PMMA core/shell composite latexes were synthesised successfully by microemulsion polymerisation. DLS studies indicated that an optimal dosage of surfactant (1.29 wt% of the total amount of monomers) was found to synthesise particles with desired core–shell structure, which was consistent with the theoretical calculation. The size of nanoparticles increased with the increase in the amount of core monomer, showing an inverse relationship with surfactants.

For the first time, an asymmetric lightly doped Schottky barrier carbon nanotube field effect transistor (SB_CNTFETs) is proposed and simulated using quantum simulations. Comparisons are made among four SB_CNTFETs structures for electrical characteristics. One is the conventional SB_CNTFET with an intrinsic channel. The other proposed and studied designations are an asymmetrically doped SB_CNTFET with a doped region near the source only, a symmetrically doped source and drain SB_CNTFETand an asymmetric lightly doped SB_CNTFET which shows the ultimate performance among all. The results show that the new asymmetric lightly doped design decreases significantly the leakage current and thus increases on/off ratio as well as cutoff frequency. It is also demonstrated that this structure possesses two perceivable steps in potential profile of the channel, which lead to another lateral electric field peak inside the channel which leads to the immunity against short-channel effects. The cutoff frequency characteristics of the four structures of SB_CNTFETs have been discussed. Results show that for channel lengths >30 nm cutoff frequency of the asymmetric lightly doped SB_CNTFETis greater than others. The effect of different doped region lengths in a 30 nm SB_CNTFET has been discussed as well. The proposed new design is promising from several points of view discussed in the study.

The effect of sintering in air and oxygen atmospheres on microstructure and microwave dielectric properties of ZnNb₂O₆ ceramics has been investigated and compared. For most cases samples sintered in oxygen atmosphere exhibited higher density than those sintered in air atmosphere. The highest densities obtained for samples sintered in air and oxygen atmospheres were 93.6 and 95.2% of the theoretical value, respectively. The variation of relative permittivity (ε _r) values with temperature for samples sintered in air and oxygen atmospheres followed the variation in the density values. The highest values of ε _r for samples sintered in air and oxygen atmospheres were 22.6 and 23.5, respectively. A considerable improvement in Q × f (Q and f are quality factor and resonant frequency, respectively) was obtained for most sintering temperatures when sintering was performed in oxygen atmosphere. The highest Q × f obtained for samples sintered in air and oxygen atmospheres were 82,688 and 81,204 GHz, respectively. Temperature coefficient of resonant frequency (τ _f) values closer to the ideal value (0 ppm/°C) was exhibited by samples sintered in oxygen atmosphere. The best values of τ _f for air and oxygen sintering atmospheres are −59.4 and −48.6 ppm/°C, respectively.

Herein is investigated the effect of ultrasonic irradiation on the preparation of Ag₃PO₄ particles based on the ion-exchange method. X-ray diffraction, scanning electron microscope, diffuse reflectance spectrum and photoluminescence were used to characterise the products. It is found that the application of ultrasonic irradiation at a frequency of 40 kHz leads to the production of uniform spherical particles with an average size of ∼300 nm. However, at a higher ultrasonic frequency of 60 kHz, the prepared sample presents polyhedron-shaped particles in the size range of 6–8 μm, which are constructed from small grains with a size of several hundred nanometres. Without the aid of ultrasonic irradiation, the samples prepared at room temperature or under 50 °C water-bath condition are composed of spherical particles and large-sized agglomerative particles. The photocatalytic activity of Ag₃PO₄ samples was evaluated by degrading rhodamine B (RhB) under simulated sunlight irradiation. Among these samples, the one prepared at 40 kHz exhibits the highest photocatalytic activity, where the degradation percentage of RhB reaches 96% after irradiation for 60 min.