Nano

An analytical model describing the conductivity of ZnO nanofibers depending on the grains size is proposed. The research is based on the thermal dc electrical measurements of a single electrospun ZnO nanofiber calcined at different temperatures. In the our previous research, we showed that electrical conduction of ZnO nanofibers is mainly thermally activated. The activation energy of conductivity was strongly dependent on the grain size, which in turn depended on the calcination temperature. This could be due to migration of a point defect in the grain of ZnO and could change the carrier concentration. Our recent studies have shown that ZnO nanofibers behavior is consistent with the Meyer–Neldel rule. This indicates an exponential energy distribution of deep level traps in the material. Based on the theoretical assumptions and experimental data, the improved model of conductivity in a single ZnO nanofiber calcined at different temperatures was proposed.

A layer of flake-like Fe₂O₃ particles doped with rare earth Nd${}^{3+}$ ions is homogeneously coated on the surface of cenosphere by using ferric nitrate as the iron source, tartaric acid as the precipitating agent, hexadecyl trimethyl ammonium bromide as the dispersing agent and neodymium nitrate as the dopant via a facile hydrothermal route. The as-prepared cenosphere is characterized by various analytical techniques such as field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, thermal gravimetric analysis, differential scanning calorimetry, diffuse reflectance spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The performances of photocatalytic degradation of methylene blue dye are also investigated under ultraviolet and visible light irradiations. The experimental results indicate that the doping concentration of Nd${}^{3+}$ ions is optimized as 0.4% with respect to Fe${}^{3+}$ ions, and the rare earth Nd${}^{3+}$ ions are highly dispersed onto Fe₂O₃ particle surface. After being doped with Nd${}^{3+}$ ions, the photoactivity of the 0.4% Nd-doped Fe₂O₃ coated cenosphere is distinctly improved. The magnetic properties are also enhanced to a large extent.

A synchrotron small-angle X-ray scattering (SAXS) study on PVA/Fe₃O₄ magnetic hydrogels has been performed to investigate the effect of clustering on their magnetic properties. The hydrogels were prepared through freezing–thawing (F–T) processes. The structure, morphology and magnetic properties of magnetite (Fe₃O₄) nanoparticles (NPs) were investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and a superconducting quantum interference device (SQUID) magnetometer, respectively. In this study, SAXS data were used to reveal the structural dimensions of the magnetite and its distribution in the polymer-rich PVA and magnetic hydrogels. As calculated using the Beaucage and Teubner–Strey models, the average of the structural dimensions of the PVA hydrogels was 3.9nm (crystallites), while the average distance between crystallites was approximately 18nm. Further analysis by applying a two-lognormal distribution showed that the magnetite NPs comprised secondary particles with a diameter of 9.6nm that were structured by primary particles ($\sim$3.2nm). A two-lognormal distribution function has also been used in describing the size distributions of magnetite NPs in magnetic hydrogels. The clusters of magnetite NPs in the magnetic hydrogels are significantly reduced from 30.4nm to 12.8nm with decreasing concentration of the NPs magnetite from 15wt.% to 1wt.%. The saturation magnetization values of the magnetite NPs, the 15% and 1% magnetic hydrogels were 34.67emu/g, 6.52emu/g and 0.37emu/g, respectively.

H₂O₂ detection plays an important role in electrochemical sensing since H₂O₂ often acts as an intermediate product or regulator in various reactions. Nanoporous carbon (NPC) can be a potential candidate in electrochemical sensing because of its high specific surface area, various pore sizes and structures. In this work, we reported the preparation of N-doped NPC derived from the highly available, accessible and recyclable plant Typha orientalis. The products have high surface area (highest surface areas of 1439.0 m² g${}^{-1})$ and a number of nanopores. Highest content of nitrogen atom in the product is 3.66 at.%). Typical product exhibits high electrocatalytic activity for reduction of hydrogen peroxide. The product may have further use for glucose biosensing. We developed a low-cost, simple and readily scalable approach to prepare the excellent carbon electrocatalyst directly from crude biomass. In addition, because of high surface area and doping of nitrogen element, the product may find broad applications in the fields of supercapacitors, lithium-ion batteries, gas uptake and so on.

The properties of an electron strongly coupled to longitudinal optical (LO) phonon in RbCl parabolic quantum dot (PQD) with a hydrogen-like impurity at the center were investigated at a finite temperature. We have obtained the vibrational frequency of a strong-coupling polaron in RbCl PQD by using linear combination operator method. We then calculate the effects of temperature, the Coulombic impurity potential and the effective confinement strength on the vibrational frequency by using unitary transformation and the quantum statistics theory methods. The influences of the temperature, the Coulombic impurity potential and the effective confinement strength on the ground state energy and the ground state binding energy are also analyzed. The strengths of these quantities increase with raising temperature. The vibrational frequency is an increasing function of the Coulombic impurity potential and the effective confinement strength. The ground state energy is an increasing function of the effective confinement strength, whereas it is a decreasing one of the Coulombic impurity potential. The ground state binding energy is an increasing function of the Coulombic impurity potential, whereas it is a decayed one of the effective confinement strength.

LaCoO₃ (LCO) epitaxial films were grown on (001) LaAlO₃ (LAO) substrates by the simple sol–gel technique. X-ray diffraction (XRD) and the cross-section transmission electron microscope (TEM) measurements indicate that single-phase (001) oriented LCO epitaxial films with biaxial compressive strain and elongated distortion of CoO₆ octahedrons were grown on (001) LAO successfully. The epitaxial relationship between the LCO film and the LAO substrate is confirmed to be (001)${}_{\mathrm{\text{LCO}}}||{(001)}_{\mathrm{\text{LAO}}}$ and [100]${}_{\mathrm{\text{LCO}}}||{[100]}_{\mathrm{\text{LAO}}}$. It is also found that LCO grown on LAO has a larger mean Co–O bond length and unit-cell size, compared with those of polycrystalline film. In addition, the magnetic characterization shows that LCO epitaxial film exhibits an obvious ferromagnetic (FM) transition at $T_C\sim 85$K, which is different from the nonmagnetic ground state of polycrystalline LCO. Combined with the structural analyses, it reveals that the strain-induced ferromagnetism observed in LCO epitaxial film originates from an increase of the mean Co–O bond length and a suppression of the CoO₆ octahedral rotations, which can stabilize higher spin state of Co${}^{3+}$ by a decrease of the $e_g-t_{2g}$ gap energy.

Despite the fact that silicon material can be synthesized from various sources, deriving them from silica resources is of strategic significance for the industrial processing. Here a low-cost nano/micro structure of Si–CNT was derived from nano-SiO₂ and multiwall carbon nanotubes (MWCNTs) with simple methods. By employing table salt (NaCl) as a heat scavenger for the magnesiothermic reduction, the nano/micro structure of the material was remained effective. Comparing to ball milling, a combination of SiO₂, MWCNTs and NaCl by spray drying achieved the long cycle life for Si–CNT composite. This material presented a stable capacity above 968.1mAh g${}^{-1}$ with excellent capacity retention of 85.4% at the 150th cycle versus the 2nd one. The Si nanoparticles, very small particle size in 10–20nm, homogenously dispersed in electronically conductive network of MWCNTS, which accommodate the volume change of Si and reinforce highly conductivity of the Si–CNT composite during repeated cycles. Combined with its low-cost and up-scaling technologies, Si–CNT composite is a promising anode material in rechargeable lithium batteries with high electrochemical performance.

In this work, novel sisal-like hollow CuO micro-flowers were synthesized via a facile solvothermal reaction followed by calcination. The flower-like shells of hollow CuO are constructed by irregular petals interweaving each other, which are composed of aggregated nanoparticles with sizes of ca. 18nm. It was found that the flower-like morphology of the as-synthesized CuO products can be controlled via finely tuning the solvothermal reaction time. When used as catalysts for the synthesis of organosilane, the obtained hollow CuO micro-flowers exhibit better catalytic performances than the commercial CuO powders. Superior catalytic performances are due to the hollow and flower-like structures of the as-synthesized CuO products, which can promote the synthetic reaction for the organosilane, that is, the gas–solid contacting reaction occurred among the reaction gas, solid silicon powders and CuO catalysts. Our work will be helpful to design and develop the novel Cu-based nanocatalysts for the synthesis of organosilane.

The paper was retracted as the authors have submitted the same manuscript to two completely different journals, which is seriously academic fraud and against academic ethics.

High-quality neodymium oxychlorides nanocrystals with cubic shape were synthesized by a nonhydrolytic thermolysis route. The morphology and crystal structure of the neodymium oxychlorides nanocubes were characterized by transmission electron microscopy at the nanoscale. Transmission electron microscope (TEM) image shows that the neodymium oxychlorides nanocrystals are nearly monodispersed with cube-like shape. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns of numerous neodymium oxychlorides nanocubes suggest a pure crystal phase with tetragonal PbFCl matlockite structure. HRTEM image of individual neodymium oxychlorides nanocubes indicate that each nanocubes have a single-crystalline nature with high quality. Unlike the anti-ferromagnetism of the bulk, the neodymium oxychlorides nanocubes show clearly anomalous ferromagnetic characteristic at room temperature. This finding provides a new platform for the exploration of diluted magnetic semiconductors, rare earth-based nanomaterials and so on.

Sulfur-doped SnO₂ nanoparticles with ultrafine sizes have been successfully prepared by a one-pot hydrothermal method. The obtained samples are characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), thermogravimetric (TG), analyzer UV-Vis spectroscopy, photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The experimental results indicate that the doping level of sulfur element as well as the bandgaps of SnO₂ can be controlled to a certain extent by varying the amount of L-cysteine (L-cys). When evaluated as photocatalysts in the degradation of rhodamine B (RhB) and reduction of Cr(VI) under visible light region, the resultant sulfur-doped SnO₂ nanoparticles demonstrate obviously enhanced photocatalytic activities due to the markedly improved visible light response and effective separation of the photo-generated electron–hole pairs.

A novel electrochemical sensing platform was constructed based on a facile self-assembly procedure synthetic laminar molybdenum trioxide dihydrate (MoO${}_3\cdot 2$H₂O)-graphene composite. Field emission scanning electron microscopy (FESEM), X-ray spectroscopy, X-ray diffraction (XRD) and Raman spectroscopy were employed to characterize the morphology and composition of the MoO${}_3\cdot 2$H₂O-graphene composite. As a model molecule, thiourea was utilized to investigate the electrochemical behaviors of the MoO${}_3\cdot 2$H₂O-graphene composite modified glass carbon electrode. The results show that the composite modified electrode has higher electron transfer rate than that of graphene modified electrode and bare glass carbon electrode meanwhile the peak currents of it has a good linear relationship with thiourea concentrations in the range of $2.40\times 10^{-3}-19.3\times 10^{-3}\mathrm{\text{M}}$ ($R=0.998$) with detection limit of 4.99$\mu$M ($\mathrm{\text{S/N}}=3$). This novel electrochemical sensor exhibits a higher absorption capacity ($3.87\times 10^{-8}$mol/cm²), a good reproducibility (1.41% relative standard deviation (RSD)), excellent anti-interference and a high stability. These excellent electrochemical properties of the MoO${}_3\cdot 2$H₂O-graphene composite are attributed to the loose and porous structure and the synergistic effects between graphene and MoO${}_3\cdot 2$H₂O, which make this composite material hold great potential applications for electrochemical sensor.