Yanbo Wu

Preparation of aligned Eu(DBM)3phen/PS fibers by electrospinning and their luminescence properties

Electrospinning is a technique employed to prepare nanofibers of polymer, ceramics, and composite that are used in the high electrostatic field. Alignment is an important step toward the exploitation and applications of these fibers. In the present report, super-long aligned luminescent composite Eu(DBM)3phen/PS fibers (DBM=dibenzoylmethane, phen=1,10-phenanthroline, PS=polystyrene) were prepared via an electrospinning method. The key to the success of this method was the usage of high molecular weight PS (Mw=4.4×10(5)) in the electrospinning solution and the low speed (>0.5 m/s) collecting drum. Luminescent properties of the composite fibers were systemically studied in comparison with that of the corresponding pure europium complex Eu(DBM)3phen. The results showed that the fluorescence lifetime of (5)D0 state and the luminescent intensity of Eu(3+) in Eu(DBM)3phen/PS composite fibers increased gradually with the fiber diameter. The composite fibers with smaller diameter exhibited better photoluminescence stability than that of the pure complex Eu(DBM)3phen.

Ultralong well-aligned TiO 2 :Ln 3+ (Ln = Eu, Sm, or Er) fibres prepared by modified electrospinning and their temperature-dependent luminescence

Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibres in micro-/nano-scale fineness: however, it remains a significant technological challenge to assemble aligned fibre arrays via an conventional electrospinning method due to the inherent whipping instability of the polymeric jet. We herein have first developed a simple modified electrospinning method with which to prepare ultralong (>300 mm) well-aligned inorganic fibre arrays, i.e., using an ultrahigh molecular weight polymer to suppress or eliminate the whipping motion of the electrospun jet, has emerged as a facile approach for the continuous fabrication of well-aligned, ultralong fibres through simply using a rotating cylinder as the collector (it was not found necessary to use a very high rotating speed, extra magnetic, electrical field) in the electrospinning process. As result, the ultralong well-aligned TiO2:Ln3+ (Ln = Eu, Sm, or Er) fibre arrays can be obtained from ultrahigh molecular weight poly(ethylene oxide), tetra-n-butyl titanate (Ti(OC4H9)4) and lanthanide nitrate in the modified electrospinning approach. The grow mechanism and luminescent properties of these ultralong well-aligned TiO2:Ln3+ fibre arrays were also investigated.

Preparation of a novel PAN/cellulose acetate-Ag based activated carbon nanofiber and its adsorption performance for low-concentration SO2

Polyacrylonitrile (PAN), PAN/cellulose acetate (CA), and PAN/CA-Ag based activated carbon nanofiber (ACNF) were prepared using electrostatic spinning and further heat treatment. Thermogravimetry-differential scanning calorimetry (TG-DSC) analysis indicated that the addition of CA or Ag did not have a significant impact on the thermal decomposition of PAN materials but the yields of fibers could be improved. Scanning electron microscopy (SEM) analysis showed that the micromorphologies of produced fibers were greatly influenced by the viscosity and conductivity of precursor solutions. Fourier transform infrared spectroscopy (FT-IR) analysis proved that a cyclized or trapezoidal structure could form and the carbon scaffold composed of C=C bonds appeared in the PAN-based ACNFs. The characteristic diffraction peaks in X-ray diffraction (XRD) spectra were the evidence of a turbostratic structure and silver existed in the PAN/CA-Ag based ACNF. Brunner-Emmett-Teller (BET) analysis showed that the doping of CA and Ag increased surface area and micropore volume of fibers; particularly, PAN/CA-Ag based ACNF exhibited the best porosity feature. Furthermore, SO2 adsorption experiments indicated that all the three fibers had good adsorption effects on lower concentrations of SO2 at room temperature; especially, the PAN/CA-Ag based ACNF showed the best adsorption performance, and it may be one of the most promising adsorbents used in the fields of chemical industry and environment protection.

Preparation and electrochemical properties of carbon-coated LiFePO4 hollow nanofibers

Carbon-coated LiFePO4 hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO4 hollow nanofibers have good long-term cycling performance and good rate capability: at a current density of 0.2C (1.0C = 170 mA·g−1) in the voltage range of 2.5–4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mAh·g−1 with a first charge–discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mAh·g−1, even at 2C.

Preparation of metal oxide doped ACNFs and their adsorption performance for low concentration SO2

Metal oxide (TiO2 or Co3O4) doped activated carbon nanofibers (ACNFs) were prepared by electrospinning. These nanofibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunner-Emmett-Teller method (BET). The results show that the average diameters of ACNFs were within the range of 200–500 nm, and the lengths were several tens of micrometers. The specific surface areas were 1146.7 m2/g for TiO2-doped ACNFs and 1238.5 m2/g for Co3O4-doped ACNFs, respectively. The electrospun nanofibers were used for adsorption of low concentration sulfur dioxide (SO2). The results showed that the adsorption rates of these ACNFs increased with an increase in SO2 concentration. When the SO2 concentration was 1.0 μg/mL, the adsorption rates of TiO2-doped ACNFs and Co3O4-doped ACNFs were 66.2% and 67.1%, respectively. The adsorption rate also increased as the adsorption time increased. When the adsorption time was 40 min, the adsorption rates were 67.6% and 69.0% for TiO2-doped ACNFs and Co3O4-doped ACNFs, respectively. The adsorption rate decreased as the adsorption temperature increased below 60°C, while it increased as the adsorption temperature increased to more than 60°C.

Luminescent properties of Eu3+ ions depend on temperature in electrospun Gd2O3:Eu3+ nanofibres

Gd2O3:Eu3+ nanofibres of different diameters were prepared by an electrospinning technique, and were characterised by XRD, SEM, and TEM. The temperature-dependence of their luminescent properties was investigated. The Eu3+ concentration exerted a significant effect on the thermal quenching rate of the Gd2O3:Eu3+ nanofibres, but the thermal quenching rate of the Gd2O3:Eu3+ nanofibres was independent of their diameters.

Fabrication of aligned Eu(TTA)3phen/PS fiber bundles from high molecular weight polymer solution by electrospinning

Super-long aligned luminescent Eu(TTA)3phen/PS composite fibers (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline, PS = polystyrene) with diameter in the range of 1–10 μm were prepared via an electrospinning method. The key to the success of alignment of these fibers was the usage of high molecular weight PS in the electrospinning solution and the low speed collecting drum. Luminescent properties of the composite fibers were systemically studied in comparison with that of the corresponding pure europium complex Eu(TTA)3phen. The results showed that the fluorescence lifetime for the 5D0 state in the composite fibers became shorter compared to that in the pure europium complex and decreases gradually with the concentration of Eu(DBM)3phen complex.

Synthesis and luminescent properties of LaPO4:Eu3+ nanocrystal with ultrasonic method

It is well know that nanoscale rare earth compounds can increase luminescent quantum efficiency and display resolution. To improve luminescent properties of nanocrystalline phosphors and obtain the nanocrystals with different morphology, many preparation methods have been used, such as hydrothermal approach, sol-gel technique and ultrasonic method, etc. In this paper, the LaPO4: Eu3+ nanocrystals were prepared via the ultrasonic method. There were two series prepared, by changing ultrasonic time, using polyvinglpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) as template, respectively. The morphology, structure and spectra properties of the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and fluorescence spectrum (FS). The results show that all the LaPO4 nanocrystals have a hexagonal structure, and without other impurity phase appearance. All the samples obtained are nanoparticles in the range of 50-120 nm, which indicates that there are almost no effectives on the morphology of the nanocrystals with the change of template kinds and ultrasonic time. But their luminescent properties depend on the kinds of template. When the ultrasonic time is 1h, the luminescent intensity of the obtained sample using PVP as template is much stronger than that using CTAB, but the 5D0 energy level fluorescence lifetime of the Eu3+ in the sample using PVP template is shorter than that using CTAB. In addition, in the two series, luminescent intensity increases at first, then decreases with the growth of ultrasonic time, but the 5D0 energy level lifetime of Eu3+ shows no regulation.