Nano

In this work, highly uniform single crystal Fe₂O₃ nanorods have been synthesized by a facile hydrothermal method in the presence of dihydrogen phosphate ions. Phosphate ions were speculated capping to the sidewalls of Fe₂O₃ nanocrystals, and resulted in the anisotropic growth of hematite crystals along their [006] zone axis. Fe₂O₃ nanorods with various aspect ratios have been realized by applying different phosphate concentration of 0.1–0.4mM. The electrochemical properties of Fe₂O₃ nanorods showed that the samples with the smallest aspect ratio possessed superior specific capacitance and stability. It was speculated that the larger specific area of the Fe₂O₃ nanorods with the shortest axial length facilitated the efficient access of electrolyte ions to the electrode surface, and thus would aid in delivering the high pseudocapacitance. These results provide a promising route to obtain the desired hematite-based energy storage materials.

The bactericidal magnetic nanoparticles were prepared by modifying magnetic nanoparticles (MNPs) with $N$-halamine polymer coating and quaternary ammonium polymer coating via a two-step soap-free emulsion polymerization method. The success of the surface functionalization was confirmed by Fourier transform infrared (FT-IR), X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and zeta-potential measurement. The results of antibacterial tests showed that the functional MNPs exhibited excellent antibacterial efficiency against both Gram negative bacteria E. coli and Gram positive bacteria S. aureus. Meanwhile the nanoparticles could be removed easily from water by an external magnetic field after antibacterial tests.

A novel nanomaterial composed of copper and carbon nanofibers (CuCNFs) decorated with Ag-doped TiO₂ (Ag–TiO${}_2)$ nanoparticles was prepared through electrospinning, carbonization and solvothermal treatment. The composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The obtained composites were mixed with laccase and Nafion to construct novel hydroquinone biosensor. The electrochemical behavior of the novel biosensor was studied using cyclic voltammetry (CV) and chronoamperometry. The results demonstrated that the biosensor possessed a wide detection linear range (1.20–176.50$\mu$M), a good selectivity, repeatability, reproducibility and storage stability. This work provides a new material to design more efficient laccase (Lac) based biosensor for hydroquinone detection.

Porous NiCo₂S₄ networks have been successfully synthesized by a facile one-pot solvothermal method without the use of any surfactant or template. Crystal structure, morphology, composition and surface area of the as-synthesized samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer–Emmet–Teller techniques. Owing to their porous nature and small crystalline size, the as-prepared NiCo₂S₄ networks based supercapacitor electrodes showed a high specific capacitance of 1250F$\cdot$g${}^{-1}$ at 1A$\cdot$g${}^{-1}$, and excellent cycling stability with the retention capacity of 70.3% after 5000 cycles in the KOH aqueous solution electrolyte.

Ruthenium (II) polypyridyl complexes modified titanium dioxide materials with anatase phase, the length of 10–100nm, were synthesized by a hydrothermal method. Photocatalytic CO₂ reduction experiments were performed in sensitized TiO₂ aqueous suspensions under UV–Vis light in closed systems. And only methanol was detected in the liquid phase under the experiment condition. The effect of different photosensitizers content on the photoactivity of TiO₂ was also studied, showing that Ru(BiDiPy)₂(NCS)₂ sensitized TiO₂ was the optimal photocatalyst in transformation of CO₂ to methanol. A possible mechanism for the photocatalytic reduction was also proposed in this paper.

Three-dimensionally hierarchical Bi₂WO₆ architectures have been produced via a facile and economical hydrothermal method without any template or surfactant. This architecture with flower-like morphology is assembled by numbers of intercrossed nanosheets. Moreover, different Bi₂WO₆ nanostructures including multilayered disks and irregular nanoplates can also be produced by simply adjusting the pH value of the precursor solution. Importantly, this kind of hierarchically structured Bi₂WO₆ architecture exhibits a much better photocatalytic activity in the photodegradation of rhodamine B than that of conventional Bi₂WO₆ multilayered disks and nanoplates. This enhanced photocatalytic performance is mainly attributed to the large specific surface areas, special structural features and high capability of absorbed oxygen species. The present work offers an effective approach for the further improvement of photocatalytic activity by designing a desirable micro/nanoarchitecture.

In this work, the Fe-doped ZnO powders have been synthesized by a facile chemical coprecipitation method. The structure, morphology and magnetic properties of the as-prepared powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The results showed that the Fe ions were well incorporated into the crystal lattice of ZnO and had a valence state of $+3$. The magnetization curves indicated the Fe-doped ZnO presented the ferromagnetic behavior at room temperature. Moreover, the electromagnetic (EM) parameters and microwave absorption properties of Fe-doped ZnO/paraffin wax in the frequency range of 2–18GHz were explored. The minimum reflection loss reached $-38.4$ dB at 6.6 GHz, and the reflection loss less than $-10.0$ dB was 4.0 GHz (from 11.0GHz to 15.0GHz) with a thickness of only 2.5 mm. Significantly, the enhanced microwave absorption of the as-prepared powders could be achieved by doping with Fe${}^{3+}$ ions or varying the thickness of the absorbers. The mechanism of microwave absorption were attributed to the good impedance matching, the dielectric loss resulted from the crystal lattice defects and the magnetic loss originated from the natural resonance. It is believed that the Fe-doped ZnO powders could be used as potential microwave absorbers.

Fluorine doped graphitic carbon nitride (g-C₃N₄) was successfully synthesized by a convenient co-polycondensation of urea and ammonium fluoride (NH₄F) mixtures, and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), UV-Vis diffuse reflectance absorption spectra (UV-DRS), nitrogen adsorption–desorption, photoelectrochemical measurement and photoluminescence (PL) spectra. The photocatalytic activities of fluorine doped g-C₃N₄ samples were evaluated by the degradation of Rhodamine B (RhB) solution under visible light irradiation. The results showed that the fluorine doped g-C₃N₄ had a better photocatalytic activity than that of undoped g-C₃N₄, which was attributed to the favorable textural, optical and electronic properties derived from the fluorine atoms substituting nitrogen atoms of g-C₃N₄ frameworks. The photoelectrochemical measurements confirmed that the charges separation efficiency was improved by fluorine doping g-C₃N₄. Moreover, the tests of radical scavengers demonstrated that the holes (h${}^{+}$) and superoxide radicals ($\cdot$O${}_2^{-}$) were the main active species for the degradation of RhB.

The unique properties of graphene quantum dots (GQDs) make them interesting candidate materials for innovative applications. Herein, we report a facile method to synthesize amino-functionalized graphene quantum dots (AF-GQDs) by a hydrothermal reaction. Graphene oxide (GO) was synthesized by Hummer’s method where ultra-small GO sheets were obtained by a prolonged oxidation process followed by sonication using an ultrasonic probe. Subsequently, graphene hydrogel (GH) was also obtained by a hydrothermal synthesis method. Proper care was taken during synthesis to avoid contamination from water soluble impurities, which are present in the precursor, GO solution. Following the treatment of GH in ammonia, ultra-small amino-functionalized graphene fragments (AF-GQDs) were formed, which detached from the GH to eventually disperse evenly in the water without agglomerating. This modified synthesis process enables the formation of high-purity AF-GQDs (99.14%) while avoiding time-consuming synthesis procedures. Our finding shows that AF-GQDs with sizes less than 5nm were well dispersed. A strong photoluminescence (PL) emission at $\sim$410nm with 10% PL quantum yield was also observed. These AF-GQDs can be used in many bio applications in view of their low cytotoxicity and strong fluorescence that can be applied to cell imaging.

ZnO nanocrystals were introduced into Fe₃O₄/MWCNTs composites to improve the impedance matching and electromagnetic (EM) wave attenuation of the system. The as-synthesized ZnO/Fe₃O₄/MWCNTs composites were characterized by X-ray diffraction, vibrating sample magnetometer, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy. SEM and TEM images showed that Fe₃O₄ microspheres 100–200nm in size connected MWCNTs. Analysis of EM parameters revealed that the impedance matching of the ZnO/Fe₃O₄/MWCNTs composites was considerably improved after ZnO nanocrystals were introduced. The ZnO/Fe₃O₄/MWCNTs composites exhibited a highly efficient microwave absorption (MA) capacity within the tested frequency range of 2–18GHz. The optimal reflection loss of EM waves was $-38.2$dB at 6.08GHz with an absorber thickness of 3.5mm. The excellent MA properties of the composites could be attributed to the improved impedance matching, interfacial polarization, and combined effects of dielectric and magnetic losses.

As a IV–VI semiconductor, GeS is winning wide attention for its excellent properties. However, few examples of GeS nanostructures, especially those with photoluminescence (PL) properties, have been reported. After the optimization of reaction conditions, including time and temperature, the GeS nanowires with PL properties are synthesized a green, facile hydrothermal route without using any toxic reagent. These materials are characterized by transmission and scanning electron microscopy (TEM and SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), etc. With the average diameter of $\sim$200nm and the length ranging from 1–25$\mu$m, the resulting GeS nanowires have relatively smooth surface and round top, and are oriented along [100] facet. The growth mechanism of GeS nanowires is investigated, and the understanding of their growth mechanism could provide helpful guidance for designing experimental conditions rationally to synthesize nanowires. Due to their special nanostructure, these nanowires possess very good fluorescent properties, which indicates that these nanowires have potential to apply in future optical nanodevices.

In this paper, we systematically investigated the influence of adhesive residue existing in deterministic transfer process upon graphene, and put forward a rapid and effective way named ultraviolet-ozone (UVO) treatment to reduce this negative effect. Results indicate that this adhesive residue may cause poor contact between metal and graphene, thus greatly degrading the performance of the device. However, this unpleasant influence could be reduced effectively by adopting UVO treatment. This work may be helpful to fabricate higher performance functional devices based on two-dimensional materials by removal of the adhesive residue.