Keyan Zheng

Adsorption of heavy metal ions from aqueous solutions by zeolite based on oil shale ash: Kinetic and equilibrium studies

Na-A zeolite was successfully synthesized via the alkaline fusion method with oil shale ash as the raw material. The adsorption capacity of it was tested by removing Cu2+, Ni2+, Pb2+ and Cd2+ from aqueous solutions. The results reveal the maximum adsorption capacity of adsorbent for Pb2+, Cu2+, Cd2+ and Ni2+ were 224.72, 156.74, 118.34 and 53.02 mg/g, respectively. The effects of contact time and pH value of solutions on the adsorption efficiency of the zeolite were evaluated. Besides, The equilibrium adsorption data and the batch kinetic data were correlated with Langmuir and Freundlich models and the pseudo-first-order and pseudo-second-order models separately. The results show that the Langmuir isotherm and the pseudo-second-order equation were more suitable for the adsorption of Na-A zeolite for the metal ions. In addition, Thermodynamic parameters of the adsorption(the Gibbs free energy, entropy, and enthalpy) were also evaluated and discussed. The results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions and the synthesized zeolite was an effective adsorbent for the removal of metal ions from aqueous solution.

Controlled synthesis and morphology dependent luminescence of Lu2O2S:Eu3+ phosphors

Lu2O2S:Eu3+ phosphors were successfully prepared with controllable morphology, including 3D sphere-like, cloud-like, nested tetrahedron, flower-like and 1D rod-like architectures. It is indicated that the pH value of the system plays an important role in the morphology and the degree of crystallinity of the product. Interestingly, with morphological changes, the band gap energy of the Lu2O2S crystal changed, followed by a variation of the crystal field symmetry and furthermore the luminescence performance. Therefore, such a morphology-sensitive luminescence property was first interpreted in terms of degree of crystallinity, band gap energy, and the crystal field symmetry around Eu3+.

Luminescence properties, energy transfer and multisite luminescence of Bi3+/Sm3+/Eu3+-coactivated Ca20Al26Mg3Si3O68 as a potential phosphor for white-light LEDs

A series of blue-to-red emitting Ca20Al26Mg3Si3O68:Bi3+/Sm3+/Eu3+ phosphors were synthesized via a high temperature solid-state reaction method. The crystal structure, luminescence properties, energy transfer and multisite luminescence were investigated in detail. Under ultraviolet (UV) light excitation of 343 nm, Bi3+-doped Ca20Al26Mg3Si3O68 phosphors exhibit a broad blue emission band from 370 to 600 nm which is derived from the allowed transition 3P1 → 1S0 of Bi3+ ions. The Ca20Al26Mg3Si3O68:Sm3+ samples show orange-reddish emission bands at 561, 598, 649 and 708 nm under the excitation of 401 nm. The red emission of Ca20Al26Mg3Si3O68:Eu3+ samples at 587, 616, 654 and 700 nm were detected under the excitation of 392 nm, due to 5D0 → 7FK (K = 1, 2, 3, and 4) transitions. In addition, two kinds of sites for cations (Ca2+) in the host were considered from the high resolution site-selective spectroscopy of Ca20Al26Mg3Si3O68:Eu3+ at low temperature, which matches with the crystal structure of Ca20Al26Mg3Si3O68. Meanwhile, in the Bi3+, Sm3+ co-doped Ca20Al26Mg3Si3O68 samples, the energy transfer from Bi3+ to Sm3+ can be found from the photoluminescence spectra and the fluorescence decay curves. The emission hue can be tuned from cool white (0.270, 0.267) to white (0.334, 0.293), and finally to warm white light (0.405, 0.317) by suitably varying the ratio of Bi3+/Sm3+, indicating that the developed phosphor may be potentially used as a single-component white-emitting phosphor for UV light-emitting diodes. The phosphors CAMSO:Bi3+,Eu3+ develop excellent red-emission properties, so that the Eu3+ doped samples have potential application in WLED.

Fabrication and photoluminescence properties of TiO2:Eu3+ microspheres with tunable structure from solid to core–shell

Monodisperse solid and core–shell structured TiO2:Eu3+ microspheres have been successfully prepared by a facile one-step hydrothermal method using polyethylene glycol (PEG, MW 20000) as the soft template, titanium tetrabutoxide (TBOT) as the titanium source, and ethanol as the solvent. The XRD patterns show that the direct hydrothermal synthesized products are anatase titanium dioxides. TEM and SEM observations indicate that the amount of ethanol plays an important role in the formation of TiO2:Eu3+ microspheres. Solid TiO2:Eu3+ microspheres are formed by using small amounts of ethanol, while core–shell structured ones are formed by using large amounts of ethanol. Possible growth mechanisms of both the solid and the core–shell structured TiO2:Eu3+ microspheres are also proposed in this paper. In addition, without any further calcination, the direct hydrothermal synthesized solid and core–shell structured TiO2:Eu3+ microspheres show strong red emission corresponding to the 5D0 → 7F2 transition of the Eu3+ ions under ultraviolet excitation. However, the luminescence intensity of the solid microspheres is much higher than that of the core–shell structured TiO2:Eu3+ microspheres, which might be due to the fewer defects and much more effective doping of Eu3+ ions into the solid microspheres.

Luminescence properties and Judd–Ofelt analysis of TiO2:Eu3+ nanofibers via polymer-based electrospinning method

One-dimensional TiO2:xEu3+ nanofibers were fabricated via electrospinning and subsequent calcination. The as-spun nanofibers were calcined at 600, 700, 800 and 900 °C for 5 h at a heating rate of 1 °C min−1 and the concentrations of Eu3+ dopants were varied from 17 mol% to 20 mol%. The TiO2:19 mol% Eu3+ nanofibers which calcined at 700 °C (optimum condition) were investigated by thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), X-ray photo-electronic spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) excitation and emission spectra. In this article, we have discussed the effect of different calcination temperature on fiber diameter and photoluminescence properties of europium doped titania (TiO2:xEu3+) nanofibers. The possible formation mechanism of TiO2:x mol% Eu3+ nanofibers was also discussed. The spectral characteristics and Eu–O ligand behavior were discussed through Judd–Ofelt parameters such as radiative transition probability (ARAD), radiative lifetime (τrad), branching ratio (β0J) and intensity parameters (Ω2, Ω4). Furthermore, the TiO2:19 mol% Eu3+ nanofibers exhibit strong red luminescence that corresponds to the 5D0–7F2 transition (612 nm) of the Eu3+ ions under the excitation of ultraviolet light.

White light-emitting, tunable color luminescence, energy transfer and paramagnetic properties of terbium and samarium doped BaGdF5 multifunctional nanomaterials

A series of BaGdF5:x% Tb3+,y% Sm3+ phosphors are synthesized by a hydrothermal method, taking the form of irregular nanospheres with average sizes of about 20 nm. An energy transfer from Tb3+ to Sm3+ is observed in the BaGdF5:Tb3+,Sm3+ system, which is justified by the luminescence spectra. Simultaneously, a resonance-type energy transfer from Tb3+ to Sm3+ is demonstrated to occur via the dipole–dipole interaction, for which the critical distance (RTb–Sm) is calculated to be 13.49 A. Furthermore, based on the rare earth concentrations and excitation wavelengths, multiple (white, orange red, green and green yellow) emissions are obtained by Sm3+ ion co-activated BaGdF5:Tb3+ phosphors, which could make them good candidates to be used as full-color phosphors for nUV-LED. More importantly, the obtained samples also exhibit paramagnetic properties at room temperature and low temperature.

Hydrothermal assisted sol–gel synthesis and multisite luminescent properties of anatase TiO2:Eu3+ nanorods

Uniform TiO2:Eu3+ spindlelike nanorods have been successfully prepared by a hydrothermal assisted sol–gel process with ethanediamine (ED) as the shape controller. A possible formation mechanism and luminescent properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and kinetic decays. Site-selective spectroscopy was used to research into sites of Eu3+ in TiO2 lattice at 10 K, which identifies two kinds of sites of Eu3+ in TiO2 nanocrystals. One is located in the distorted lattice sites near the surface, and the other is situated in lattice sites with ordered crystalline environment. Moreover, the luminescence decay curve of products further proved the existence of multiple sites of Eu3+ ions in TiO2 nanocrystals.

Facile synthesis and color-tunable properties of BaLuF5:Ce,Tb,Eu(Sm) submicrospheres via a facile ionic liquid/EG two-phase system.

BaLuF5:Ce,Tb,Eu(Sm) submicrospheres were synthesized via an ILs/ethylene glycol(EG) two-phase system. The crystalline phase, size, morphology, and luminescence properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra. The results show that 1-methyl-3-octylimidazolium hexafluorophosphate ([Omim]PF6) was used as fluoride source and capping agent to tune morphology and size of the crystals. The formation mechanism has been supposed. Under the excitation of ultraviolet, the BaLuF5:5%Ce3+,5%Tb3+, BaLuF5:Eu3+, and BaLuF5:5%Ce3+,5%Sm3+ exhibit green and red emission, which was derived from Tb3+, Eu3+, and Sm3+ emission. When codoping Ce3+, Tb3+, Sm3+ or Eu3+ together, multi-color emission can be realized. Furthermore, this synthetic route may have potential applications for fabricating other lanthanide fluorides.

Apoptotic Effects of Hypocrellin A on HeLa Cells

Abstract Hypocrellin A(HA), a photosensitive perylenequinone compound of Hypocrella bambusae , inhibited the proliferation of several tumor cell lines. Human cervical cancer cells, HeLa cells, were used as a model to elucidate the molecular mechanisms of HA-induced tumor cell death. The results show that HA can induce the oligonucleosomal fragmentation of DNA in HeLa cells and also can increase the expression of apoptosis inducer Bax mRNA and that it decreases the expression of apoptosis suppressor, Bcl-2 mRNA, in mitochondria. It can be concluded from the data that HA-induced apoptosis is related to the balance between Bcl-2 and Bax gene expressions.

Morphology control and tunable color of LuVO4:Ln3+ (Ln = Tm, Er, Sm, Eu) nano/micro-structures

LuVO4:Eu3+ nano/microcrystals with different morphologies/sizes including nanoparticles, nanosheets, nanodisks, nanoquadrangles, sub-microflakes, microspheres, and bulks were successfully synthesized by a mild solvothermal process using tartaric acid (TA) as the template. The amount of tartaric acid (TA) and the initial pH value play vital roles in controlling the morphologies of LuVO4 products. Besides, the reaction temperature was responsible for the generation of pure LuVO4 crystals in the presence of TA. Based on this, the possible formation mechanism of multi-morphologies was proposed. Furthermore, the dependence of luminescence performance on morphology has been discussed in detail. The LuVO4:Ln3+ (Ln = Tm3+, Er3+, Sm3+, Eu3+) nanoparticles show the characterized transition of Ln3+ and give bright blue, green, orange-red and red emission. Moreover, blue-green, green-yellow, pink, yellow-pink and white light can be obtained by adjusting the amount of doped Ln3+ ions and the corresponding concentrations of the LuVO4 host. This general and simple method may be of much significance in the synthesis of many other rare earth inorganic materials.