Guijuan Ji

Facile synthesis of Ag/ZnO micro-flowers and their improved ultraviolet and visible light photocatalytic activity

Three-dimensional (3D) flower-like Ag/ZnO heterostructures with different Ag content were prepared using a facile two-step method. The samples structure, morphology and optical properties were well-characterized using XRD, SEM, EDS, XPS, DRS, PL and ICP-AES techniques. The results demonstrated the successful deposition of Ag nanoparticles on a flower-like ZnO surface. The photocatalytic performance was evaluated by the photocatalytic degradation of rhodamine B (RhB) under ultraviolet and visible light. The results showed that the Ag/ZnO heterostructures had superior photocatalytic activity compared to the pure ZnO samples and the commercial photocatalyst TiO2 (Degussa, P25). The enhanced photocatalytic activity was attributed to the effective separation of electron/hole pairs on flower-like ZnO by employing Ag nanoparticles as a conductor. Furthermore, 3D flower-like Ag/ZnO microspheres exhibited good recycling stabilities over several separation cycles photodegradation.

Preparation of porous 3D Ce-doped ZnO microflowers with enhanced photocatalytic performance

Porous 3D Ce-doped ZnO microflowers were prepared by a hydrothermal method followed by a low temperature annealing process. The effects of Ce doping on the structural and photocatalytic properties of porous ZnO microflowers were investigated in detail. The samples were characterized using XRD, SEM, EDS, XPS, DRS, PL spectra and BET surface area measurements. According to the XRD analysis, both of the crystalline structures of the synthesized pure ZnO and Ce-doped ZnO samples are hexagonal wurtzite. The XPS results demonstrated the successful synthesis of Ce4+ doped ZnO. In addition, the SEM morphologies showed the unique porous 3D flower-like structure of the Ce-doped ZnO. Compared with the porous ZnO microflowers, the Ce-doped ZnO samples exhibit improved photocatalytic performance in the decomposition of Rhodamine B (RhB). It is proposed that the special structural feature with a porous 3D structured and Ce modification lead to the rapid photocatalytic activity of the Ce-doped ZnO microflowers.

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.

Self-assembled 3D sphere-like SrMoO4 and SrMoO4:Ln3+ (Ln = Eu, Sm, Tb, Dy) microarchitectures: Facile sonochemical synthesis and optical properties

Three-dimensional (3D) well-defined SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures of obvious sphere-like shape have been successfully synthesized using a large-scale and facile sonochemical route without using any catalysts or templates. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of SrMoO4 and external factor, namely the ultrasonic time and the pH value, are responsible for the ultimate shape evolutions of the product. The possible formation mechanism for the product is presented. Additionally, the PL properties of SrMoO4 and SrMoO4:Ln(3+) (Ln=Eu, Sm, Tb, Dy) hierarchical structures were investigated in detail. The Ln(3+) ions doped SrMoO4 samples exhibit respective bright red-orange, yellow, green and white light of Eu(3+), Sm(3+), Tb(3+) and Dy(3+) under ultraviolet excitation, and have potential application in the field of color display. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating about the properties of molybdate materials.

Fabrication of CeO 2 nanoparticles decorated three-dimensional flower-like BiOI composites to build p-n heterojunction with highly enhanced visible-light photocatalytic performance

Three-dimensional (3D) flower-like CeO2/BiOI heterostructures with different Ce/Bi molar ratio were successfully synthesized via a hydrothermal method using polyvinylpyrrolidone (PVP) as surfactant. The X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) results indicate that the CeO2 nanoparticles were successfully loaded on the surface of the flower-like BiOI. The photodegradation experiment demonstrated that the photocatalytic efficiency of CeO2/BiOI samples were higher than that of pure BiOI and CeO2, and CeO2/BiOI heterostructure showed the best photocatalytic performance when the amount of CeO2 located at BiOI up to 15%. The result also exhibits that CeO2/BiOI catalysts possess higher photocatalytic efficiency for Rhodamine B (RhB) and methylene orange (MO) degradation, while it has a slight influence for phenol elimination. Meanwhile, the repeated photocatalytic degradation of RhB experiment reveals excellent photostability. A possible mechanism of photocatalysis was also explored and proposed. Furthermore, loading CeO2 on the surface of BiOI can accelerate the separation rate of photogenerated electron-hole pairs, which is analyzed by photoluminescence (PL) spectroscopy, photocurrent experiments (PC) and electrochemical impedance spectroscopy (EIS). These results exhibit that BiOI can be modified by CeO2 and there exists synergistic effect between CeO2 and BiOI. The present work provides a new means to synthesize heterostructured photocatalyst for environmental remediation.

Size‐tailored synthesis and luminescent properties of three‐dimensional BaMoO4, BaMoO4:Eu3+ micron‐octahedrons and micron‐flowers via sonochemical route

Almost monodisperse three-dimensional (3D) BaMoO4, BaMoO4 :Eu(3+) micron-octahedrons and micron-flowers were successfully prepared via a large-scale and facile sonochemical route without using any catalysts or templates. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersion X-ray (EDS), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy were employed to characterize the as-obtained products. It was found that size modulation could be easily realized by changing the concentrations of reactants and the pH value of precursors. The formation mechanism for micron-octahedrons and micron-flowers was proposed on the basis of time-dependent experiments. Using excitation wavelengths of 396 or 466 nm for BaMoO4 :Eu(3+) phosphors, an intense emission line at 614 nm was observed. These phosphors might be promising components with possible application in the fields of near UV- and blue-excited white light-emitting diodes. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating the properties of molybdate materials.

Hydrothermal preparation of 3D flower-like BiPO 4 /Bi 2 WO 6 microsphere with enhanced visible-light photocatalytic activity

A novel 3D flower-like BiPO4/Bi2WO6 photocatalyst was prepared using hydrothermal method. The crystal structure, surface morphologies and optical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and Ultraviolet-visible diffuse reflectance spectrum (UV-vis DRS). The photocatalytic activity of the BiPO4/Bi2WO6 composites was evaluated by using rhodamine B (RhB) as a target organic pollutant under visible light irradiation. The composite with the content of 15% BiPO4 exhibited the highest photocatalytic property with the 92% removal rate of RhB within 100 min under visible light irradiation, which ascribed to the fast separation efficiency of photo-induced charge carriers, according with the results of photoluminescence (PL), photocurrent (PC) and electrochemical impedance spectroscopy (EIS). Also, it showed superior stability after three times of recycling. Eventually, the possible photocatalytic mechanism of BiPO4/Bi2WO6 composite was proposed according to the energy band structure and the radical-trapping experiment.