Nano

A novel composite nanostructure which is made up of TiO₂ three dimensionally ordered macroporous (3DOM) nanostructure and TiO₂ nanorods (NRs) has been successfully synthesized through a combination of colloidal crystal template technology and hydrothermal method, then we achieved its combination with Ag nanoparticles (NPs) via a silver mirror reaction. We studied the SERS (Surface-Enhanced Raman Scattering) performance of the obtained structure, the results show that our samples are very sensitive substrates when being used to detect dye R6G molecules, with a low detection concentration of 10${}^{-11}$ M. This proves that it is a promising material in the area of analyzing and molecule-level detecting as a kind of novel and low-cost SERS substrate.

Cr-containing diamond-like carbon (Cr-DLC) nanocomposite coatings were synthesized by ion beam-assisted arc ion plating with varying hollow cathode ion source (HCIS) currents. The morphologies, compositions and microstructures were characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), X-Ray photoelectron spectrometer (XPS), Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD) and high-resolution transmission electron microscopy (HRTEM). Hardness and friction coefficient were investigated by using nanoindentation and ball-on-disc tribometer, respectively. With no HCIS current, the coating exhibits the maximal growth rate and a rough surface, as well as lower hardness and elastic modulus. With the increasing HCIS current from 40A to 80A, the growth rate and the content of chromium carbide decrease obviously, the $s{p}^3$/$s{p}^2$ ratio increases initially to the maximum at the HCIS current of 60A, the highest hardness and elastic modulus are obtained at the HCIS current of 50A. It is also revealed that moderate HCIS current can reduce surface roughness obviously and promote tribological properties. The correlation of the HCIS current with the microstructure and performance of Cr-DLC coating has been established.

Zn${}^{2+}$ and F${}^{-}$ ions are successfully used to modify pure Li₄Ti₅O${}_{12}$ via a co-precipitation method followed by calcination at 400${}^{\circ }$C for 5h in an Ar atmosphere in order to further investigate the reaction mechanism of the fluoride modification process. Zn${}^{2+}$ and F${}^{-}$ co-modified Li₄Ti₅O${}_{12}$ samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. After the modification process, no ZnF₂ coating layer is formed on the surface of Li₄Ti₅O${}_{12}$, instead, F${}^{-}$ ions react with Li₄Ti₅O${}_{12}$ to generate a new phase, composed of a small amount of anatase TiO₂, rutile TiO₂, LiF, and Zn${}^{2+}$ ions are suspected to form a ZnO coating layer on Li₄Ti₅O${}_{12}$ particles. The electrolyte reduction decomposition is suppressed in Zn${}^{2+}$ and F${}^{-}$ co-modified Li₄Ti₅O${}_{12}$ due to the ZnO coating layer. 1wt.% Zn${}^{2+}$ and F${}^{-}$ co-modified Li₄Ti₅O${}_{12}$ exhibits the best rate capability, which leads to a charge capacity of 236.7, 227.8, 222.1, 202.7, 188.9 and 150.7mAh g${}^{-1}$ at 0.2C, 0.5C, 1C, 3C, 5C and 10C, respectively, between 0V and 3V. Furthermore, 1wt.% Zn${}^{2+}$ and F${}^{-}$ co-modified Li₄Ti₅O${}_{12}$ exhibits 96.0% charge capacity retention at 3C rate after 200 cycles, which is significantly higher than that of pure Li₄Ti₅O${}_{12}$ (78.4%).

A functional polyimide (CF3 PI) was used as the active layer in our present work for electrical resistive memory device applications. Current–voltage ($I$–$V$) characteristics analysis on the polyimide memory devices indicates that the polyimide possesses a nonvolatile rewritable flash characteristic with an ON/OFF current ratio of about 10⁴ at the threshold voltage of around $-1.2$V and 3.8V. In addition, the device using the CF3 PI as the active layer reveals excellent long-term operation stability with the endurance of reading cycles up to 10⁸ under a voltage pulse and retention times for at least 10⁶s under constant voltage stress (1V). The conduction mechanisms are elucidated on the basis of the thermionic emission theory and filament conduction.

Graphene-based polyaniline (PANI/RGO), used as conductive filler, was synthesized through a new one-pot emulsion polymerization technology. Graphene dispersion (RGO) was obtained by ultrasonically reducing graphene oxide (GO) in a hot sodium hydroxide solution in the absence of any toxic reductant, such as hydrazine hydrate. Sodium dodecyl benzene sulfonate (SDBS), in which RGO sheets were dispersed, was synthesized using dodecyl benzenesulfonic acid (DBSA) and NaOH. In this RGO/SDBS mixture, polyaniline (PANI), doped with multiple acids (HCl-DBSA), was then uniformly polymerized on the surface of the RGO sheets. The experimental results showed that this reaction improved the dispersion of the RGO in the PANI system, and increased the homogeneous distribution of the formed PANI particles on the RGO surface. The synthesized composite material (PANI/RGO) had good thermal stability, electrical conductivity (about 11.71S$\cdot$cm${}^{-1})$ and water dispersibility. Based on its excellent properties, the PANI/RGO was combined with waterborne epoxy resin to prepare anticorrosion coatings. The corrosion resistance of these coatings was studied using Tafel plots, along with other critical properties tested by the national standards. The results suggested that the surface resistivity of the coatings could be as high as 2.48$\times$10${}^8\mathrm{\Omega }$ with the addition around 3wt.% of the PANI/RGO meeting good antistatic standards. In addition, the antistatic coatings had outstanding corrosion resistance, as well as tremendous physical and chemical properties.

Upconversion nanoparticles (UCNPs) are widely used in the field of biomedicine, such as biosensing, cell labeling and medical multimodal imaging because of their unique optical properties. In this paper, we demonstrated the synthesis of polyethylenimine-modified NaLuF₄:Yb,Er ($\mathrm{\text{RE}}={\mathrm{\text{Lu}}}_{0.78}$, Yb${}_{0.18}$, Er${}_{0.02})$ UCNPs in three different solvents, such as water, ethylene glycol and diethylene glycol. The as-prepared UCNPs were characterized and the experimental results showed that the UCNPs synthesized in ethylene glycol had excellent properties. The obtained UCNPs in ethylene glycol had the smallest particle size and uniform size distribution, and the pure cubic phase of crystallization and Dynamic light scattering and particle dispersion index (DLS/Pdi) were the smallest. What’s more, the upconversion fluorescence intensity was 7 and 52 times greater than that of UCNPs synthesized in diethylene glycol and water, respectively. In addition, the factors of reaction solvent that had an impact on the particle size, morphology, crystalline phase, DLS and upconversion fluorescence intensity of the synthesized UCNPs were discussed. Moreover, in order to obtain the targeted nanoprobe, we used an EDC/NHS covalent coupling method to modify folic acid to the NaLuF₄:Yb,Er/PEI UCNP surface. The NaLuF₄:Yb,Er/PEI–FA upconversion fluorescent nanoprobes had low cytotoxicity and were suitable for the application in HeLa cells targeted fluorescent imaging.

The NiO nanocrystalline/reduced graphene oxide (rGO) composite film was successfully synthesized using a simple hot-injection and dip coating method. The as-prepared samples were characterized using X-ray diffraction (XRD), Raman, scanning electron microscope (SEM), ultraviolet and visible spectrophotometer (UV). Compared to the NiO film, the NiO nanocrystalline/rGO composite film exhibits enhanced electrochromic properties and large $\mathrm{\Delta }T$ (40.7% at 550nm), fast switching speed ($t_c=4$.3s and $t_b=3$.9s), high coloration efficiency (12.85cm² C${}^{-1})$ and better cycling performance (1000 cycles). The improvement of the electrochromic properties was attributed to the large specific surface area and good conductivity of the rGO.

In this work, we developed a simple hydrothermal method toward the fabrication of TiO₂/Bi${}_{3.64}$Mo${}_{0.36}$O${}_{6.55}$ heterostructure, which had superior photocatalytic performance for degrading of RhB under visible light irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), UV-Vis diffuse reflectance spectroscopy (DRS) and photoelectrochemical measurements. The optimal composite with 15wt.% TiO₂/Bi${}_{3.64}$Mo${}_{0.36}$O${}_{6.55}$ (TBMO3) exhibits a much higher photocatalytic activity than that of Bi${}_{3.64}$Mo${}_{0.36}$O${}_{6.55}$ and P25 by degradation of RhB under visible light irradiation within 20min. The enhanced performance of TBMO₃ is predominantly attributed to the synergistic effect both in the higher surface area and the improved separation of photogenerated charge carriers between the two semiconductors. Recycling experiments indicated that TiO₂/Bi${}_{3.64}$Mo${}_{0.36}$O${}_{6.55}$ photocatalysts had excellent cycle performance and stability. The photocatalytic mechanism of nanocomposite photocatalysts was proposed, which is confirmed by the active species trapping experiments and photoluminescence tests.

In this paper, ordered mesoporous SBA-15 silica was synthesized by the hydrothermal method, and then a series of CoFe₂O₄/SBA-15 nanocomposites were synthesized by a facile impregnation method. X-ray diffraction and N₂ adsorption–desorption isotherms were used to characterize the microstructure and morphology of SBA-15 and CoFe₂O₄/SBA-15 nanocomposites. CoFe₂O₄ nanoparticles presented spinel phase structure and existed in the mesopores of SBA-15. The magnetic response of CoFe₂O₄/SBA-15 nanocomposites was characterized with vibrating sample magnetometer (VSM). The adsorption efficiency of CoFe₂O₄/SBA-15 nanocomposites for methylene blue increased firstly with the increasing CoFe₂O₄ content, and then decreased. Sample-2 (SBA-15: CoFe₂O${}_4=1$: 0.1 in the precursor) not only presented the best adsorptive performance, but also could be separated and retrieved effectively by magnetic separation technique.

Electrodes of rationally designed composite nanostructures can offer many opportunities for the enhanced performance in electrochemical energy storage. This paper attempts to illustrate the design and production of NiMoO₄/polypyrrole core–shell nanostructures on nickel foam to be used in supercapacitor via a facile hydrothermal and electrodeposition process. It has been verified that this novel nanoscale morphology has outstanding capacitive performances. While employed as electrodes in supercapacitors, the composite nanostructures showed remarkable electrochemical performances with a great areal capacitance (3.2F/cm² at a current density of 5mA/cm²), and a significant cycle stability (80% capacitance retention after 1000 cycles). The above results reveal that the composite nanostructures may be a likely electrode material for high-performance electrochemical capacitors.

The localized surface plasmon resonance (LSPR) properties of Au/Ag/graphene nanoshells are studied by discrete dipole approximation (DDA). The coupled resonance wavelengths show a remarkable dependence on the graphene thickness as well as refractive index of the surrounding medium. The resonance wavelengths of Au/Ag/graphene nanoshells red-shift as the thickness of the graphene layer is increased, when the radii of the Au core and Ag interlayer are 40nm and 45nm, respectively. Specifically, the longer wavelength red-shifts from 540nm to 740nm when the refractive index varies from 1.25 to 2.05.

Ultraviolet (UV) detection characteristics of Ag Schottky contacts with ZnO nanorods (ZnO-NRs) grown on Indium Tin Oxide (ITO)-coated glass substrates have been investigated. A low-temperature hydrothermal method was used for growing ZnO-NRs. Circular contacts of Ag were deposited above the ZnO-NRs/ITO samples using the shadow mask technique. The structural properties of the ZnO-NRs were characterized by using scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The results revealed a (0002) crystal orientation and a wurtzite hexagonal structure. The electrical characteristics of the Ag/ZnO-NR Schottky contacts were studied at forward applied bias over the range 0V to 1V, under dark and UV illumination. The dark and photocurrents were $1.29\times 10^{-5}$A and $2.16\times 10^{-5}$A, respectively, and the contrast ratio (ratio of photocurrent to dark current) was 1.67 at $+$1.0V for these devices. The results show that these devices could be useful for cost-effective and low-voltage UV detection applications.

S-doped C₃N₄ quantum dots (SCNQDs) were synthesized successfully by a low-temperature solid-phase method. The as-synthesised SCNQDs were decorated on ZnO nanorods by a dipping method. The ZnO nanorod films were prepared through a two-stage method, including pulse electrodeposition for depositing ZnO seed layer on fluorine doping SnO₂ glass (FTO) and chemical bath for growing ZnO nanorods on the ZnO seed layer. The prepared samples were characterized via scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS). The photoelectrochemical performances of the prepared samples were estimated using linear sweep voltammograms, electrochemical impedance spectra (EIS), Mott–Schottky, transient photocurrent and incident photon-to-current conversion efficiency (IPCE). The results show that the light absorption edge of the prepared SCNQDs increases from 326nm (CNQDs) to 349nm after S doping. The CNQD decorated ZnO photoanode film exhibits 1.34 times as high photocurrent as bare ZnO photoanode film. Importantly, the photocurrent increased to 1.79 times than bare ZnO photoanode film by S doping at 1.0V (versus Ag/AgCl), which is attributed to a wider light absorption of SCNQDs and a better efficiency of electron transfer in the interface between SCNQDs and ZnO.