An examination has been conducted of the effect of sonication time (25 kHz) at a constant temperature of 25°C on the structure of hydroxyapatite (HAp). Diammonium hydrogen phosphate and calcium nitrate tetrahydrate were used as starting materials. The gel formed by mixing the starting materials solution was subjected to sonication for 0, 5, 10, 20, 30 and 40 min. After sonication, HAp was dried at room temperature and calcined at 600°C for 2 h. The crystallisation, morphology and functional groups of the prepared nanoHAp were inspected by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The XRD results revealed crystalline sizes in the range 50–58 nm and 3–5 of the crystalline fraction. The TEM results proved that the particle size of nano-HAp decreased with increasing sonication time. In addition, the FTIR spectroscopy confirmed that an increase of sonication time led to an increase in the concentration of carbonate groups

Plasmonic nanoantennae are important candidates for metamaterials in the visible range. However, the fabrication of dense nanoantennae with various designs and small dimensions is still very challenging for nanoscale features with high aspect ratios. Demonstrated is a series of geometries of plasmonic nanocrystals with different designs and ultrasmall gaps using a one-step focused ion beam milling process. Optical characterisation of plasmonic nanoantennae has also been carried out to investigate the underlying physics. Theoretical calculations were also performed to verify the experimental results. The high fabrication quality nanostructures demonstrated may enable new applications in nanophotonics, giving rise to new opportunities for nanodevices.

In this reported work Ni-riched NiO-Co₃O₄ sheet-like nanocomposites (SNCs) were obtained through a facile solvothermal method in a mixed solvent and subsequently calcinated in air. Galvanostatic charge-discharge measurement revealed that the Ni-riched NiO-Co₃O₄ SNCs electrode has an impressive specific capacitance as high as 836 F g⁻¹ at 4 A g⁻¹ in 3 M KOH solution. The as-obtained Ni-riched NiO-Co₃O₄ SNCs product showed a weak cycling stability, but the higher capacitance (424 F g⁻¹) was retained after 1000 cycles at 4 A g⁻¹.

Core–shell–shell composite (Fe₃O₄@SiO₂@MnO₂) submicrospheres were successfully synthesised by homogeneous precipitation of MnO₂ on Fe₃O₄@SiO₂ spheres, which were prepared by a modified sol–gel method with the presence of Fe₃O₄ particles. The synthesised multilayer-structured nanocomposites were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and using a vibrating sample magnetometer. The results show that the magnetic Fe₃O₄ cores were well wrapped by the intermediate layer of SiO₂ with a thickness of 40 nm in the amorphous phase, and the MnO₂ nanoparticles with a diameter not exceeding 10 nm were attached on the SiO₂ shell. The magnetic measurements indicated that the Fe₃O₄@SiO₂@MnO₂ submicrospheres were of superparamagnetism with the saturation magnetisation of 29.41 eum/g. At the same time, the submicrospheres demonstrated a high chemical adsorption activity for methyl orange (MO) decolouration with efficiency of up to 93.76% within 1 h. Moreover, the submicrospheres were found to be stable under repeated applications of up to five successive cycles with a near constant adsorption activity after regeneration. It is expected that the adsorbent could be used for trace pollutants (MO) removal from water and recycled owing to its superparamagnetism properties and high adsorption activity.

A two-step microfocal lens design that can achieve high-efficiency optical coupling is reported. Simulation results show that the lens enhances optical coupling efficiency by over one-third compared with its prototype previously reported. It also slightly reduces the focal spot size. A simple top-down fabrication process flow is discussed, which indicates that the proposed two-step lens can be fabricated at low cost using conventional industrial equipment.

Rice kernel (RK)-like bismuth telluride (Bi₂Te₃) crystals were successfully synthesised by microwave-induced plasma heating of Bi and Te powders. Phase and morphology characterisation revealed the presence of the Bi₂Te₃ structure in the shape of RKs. The crystal orientation factor (f value) of RK Bi₂Te₃ powder was larger than that of the RK Bi₂Te₃ hot-pressed disk. A comparison of the f values of both samples suggested that the RK shape has significant influence in reducing the f value after hot processing. The Seebeck coefficient (S), electrical resistivity (ρ) and thermal conductivity (κ) of the RK Bi₂Te₃ disk were determined over the temperature ranging from 323 to 623 K. The S value was negative over the whole temperature range, indicating an n-type thermoelectric RK Bi₂Te₃ disk. The power factor (S ² ρ ⁻¹) was the highest at about 1.07 × 10⁻³ W/m K² at 323 K and decreased with increasing temperature. The maximum dimensionless figure of merit (ZT) of the RK Bi₂Te₃ disk was 0.26 at about 366 K.

Using a simple hydrothermal method without surfactants and templates, different morphologies of titanium dioxide (TiO₂) have been synthesised such as nanocubes, nanosheets and microspheres. The effects of the addition of hydrofluoric acid (HF) and hydrogen peroxide (H₂O₂) in the preparation of TiO₂ were studied. It was found that more H₂O₂ may accelerate the formation of a spherical morphology and that HF has three roles: dissolving Ti powder, retarding the hydrolysis of titanium precursor and reducing surface energy. Reaction time has a significant effect on morphological transformation. The aggregation of microstructures is described, the effects of the addition of HF and H₂O₂ on the condition of aggregation have been studied. Photocatalysis measurements showed that sphere-like TiO₂ consisting of nanocubes exhibited the highest activity for degrading rhodamine B under UV light.

Attaining proper temperature in engines is always a challenge for engine manufacturers primarily because temperature has a significant role in engine performance and emissions. With the development of new technology in the field of nanofluids, it seems very promising to use nanofluids as the coolant in internal combustion engines. In this reported work, Cu and diamond nanoparticles with diameters of 50 nm were dispersed in conventional engine oil to create nanofluids (volume fractions of 1, 2 and 3%) to serve as the cooling medium for a piston-cooling gallery. The piston thermal loading calculations were carried out based on numerical hydrodynamic simulation through a liquid–solid-coupled thermodynamic method. The obtained results indicate that using different volume fractions of nanofluids can effectively reduce the thermal loading of the piston.

Uniform arrays of nanochannels were made using an underexposed nanoimprint method. The nanotrenches were bended uniformly, and the degree of the collapse was controlled by the exposure time. After deposition of the sealing material, nanochannels with a dimension of 100 nm were successfully fabricated. The blocking problem was solved by adjusting the parameters of the gratings. The proposed fabrication technique can be very helpful in micro-/nanoanalysis systems.

A single silicon nanowire core–shell structure has been elaborated. Technological stages of the process are presented. The device results in a P-i-N radial junction: the core is a P-type silicon nanowire encapsulated in an intrinsic thin silicon layer and an N-type doped silicon layer. Scanning electron microscopy observations, as well as the electrical I(V) characterisation on single nanowires, are presented.

A time- and energy-saving microwave (MW)-assisted method was adopted to synthesise yttrium oxide (Y₂O₃):erbium (Er) nanoparticles with upconversion (UC) luminescence properties within a few minutes, followed by a post-calcination treatment. It was demonstrated that calcination of nanoparticles at 800°C fully removed the organic groups from them and consequently produced crystalline Y₂O₃ nanoparticles, which was evident from X-ray diffraction (XRD) and Fourier transform infrared analysis. The energy-dispersive X-ray spectroscopy and XRD analysis confirmed that the Er element was successfully doped in Y₂O₃ nanoparticles. The growth process was monitored by time-dependent experiments, during which ultra-small particles would form first and then gradually dissolved and re-growed on surfaces of big particles. A two-photon process was demonstrated in the fabricated Y₂O₃:Er nanoparticles. As a cost-effective and highly-efficient method, the MW method can facilitate mass production and further application of UC nanomaterials into a variety of fields including solar cells, flat panel displays, sensors and UC lasers.

A simple and mild green route has been developed to synthesise zinc indium sulphide nanopowders with L-cysteine as the sulphur source and complexing agent under hydrothermal conditions at 160 °C for 12 h. The crystal structure, morphologies and chemical composition of the obtained nanopowders are confirmed by X-ray powder diffraction, field-emission scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy and selected area electron diffraction. Results reveal that the synthesised nanopowder is comprised of microspheres with nanosheets and the diameter of the microspheres and the thickness of the nanosheets are 100 nm–2 μm and 10–50 nm, respectively. Moreover, a possible formation mechanism for the zinc indium sulphide product is briefly discussed. The present route would provide an alternative strategy to prepare other II–III–VI ternary metal sulphide nanocrystals.

Polypyrrole/silver chloride (PPy/AgCl) composite nanotubes have been successfully prepared via a reactive self-degrade template. By introducing ammonium peroxysulphate, AgNO₃ and pyrrole monomer into the acidic methyl orange solution in sequence, AgCl nanoparticles could be uniformly distributed into the matrix of PPy nanotubes without aggregation in the one-pot reaction. The formation mechanism, morphology and structure of the nanocomposites were studied by transmission electron microscopy, Fourier transform infrared spectra and X-ray diffraction. The presented results suggest that the one-dimensional hollow PPy/AgCl nanocomposites have significant antibacterial activity. The conducting PPy/AgCl nanotube composites may be used to fabricate the antistatic coatings with an antibacterial property in potential applications.

One-dimensional magnetic iron (Fe) nanowire arrays with tunable diameters have been deposited in the pore channels of the anodised aluminium oxide (AAO) template using the electroless chemical method. The AAO template is processed by a facile and simple approach to etch an insulating alumina barrier layer in the base of the template. The morphologies and crystal structures of Fe nanowires are characterised by field emission scanning electron microscopy, atomic force microscopy and X-ray diffraction. Mössbauer spectroscopy suggests that the nanowires are composed of ferromagnetic particles. The results of magnetic measurements by a superconducting quantum interference device indicate that the nanowire arrays have obvious magnetic anisotropy, and the easy magnetisation direction is oriented along the nanowire axial direction.