Zheng Zhai

EDTA-mediated hydrothermal synthesis of NaEu(MoO4)2 microrugbies with tunable size and enhanced luminescence properties

Tetragonal NaEu(MoO4)2 with rugby-like microstructures were successfully synthesized by a hydrothermal method in an EDTA-mediated process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) techniques were employed to characterize the products in detail. It was found that the amount of EDTA, reaction temperature and pH value are important parameters affecting the morphology, crystallinity and size of the final product, respectively. The possible formation mechanism for the microrugbies was proposed on the basis of a series of time-dependent experiments. This facile method was also successfully applied in the synthesis of NaSm(MoO4)2 and NaGd(MoO4)2 microrugbies. The photoluminescence (PL) properties of NaEu(MoO4)2 microrugbies were strongly dependent on the size and crystallinity. The calcined products displayed excellent luminescence behaviors with a high color purity and have the potential to be applied in LED devices. The possible reasons for the difference in the relative intensities of luminescence are also discussed in detail.

EDTA-mediated shape-selective synthesis of Bi2WO6 hierarchical self-assemblies with high visible-light-driven photocatalytic activities

Bi2WO6 with multilayered disc-like and 3D hierarchical nest-like architectures self-assembled from 2D nanosheets were successfully synthesized by a hydrothermal method in EDTA-mediated processes. It was found that the morphology modulation of the as-obtained products could be easily realized simply by changing the amount of EDTA introduced into the reaction system. The stepwise self-assembly formation mechanisms for two different hierarchical architectures were proposed on the basis of a series of time-dependent experiments. The photocatalytic activities of the different Bi2WO6 samples for the degradation of Rhodamine B (RhB) were also evaluated. Due to the unique morphology, porous structure and large surface area, Bi2WO6 nest-like architectures exhibited better activity performance than Bi2WO6 multilayered microdiscs. The present work not only presents an efficient way for the selectively controllable preparation of Bi2WO6 hierarchical structures viaself-assembly from 2D nanosheets, but also provides a step forward in the design of photocatalysts with controllable morphology and enhanced photocatalytic activities.

Nitrogen-doped mesoporous nanohybrids of TiO2 nanoparticles and HTiNbO5 nanosheets with a high visible-light photocatalytic activity and a good biocompatibility

Nitrogen-doped mesoporous nanohybrids of TiO2 nanoparticles and HTiNbO5 nanosheets have been successfully synthesized by first exfoliating layered HTiNbO5 in tetrabutylammonium hydroxide (TBAOH) to obtain HTiNbO5 nanosheets, then reassembling with TiO2 colloids and finally heating with urea in air at 450 °C. The resulting samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, laser Raman spectroscopy (LRS) and N2 adsorption–desorption measurements. It was found that the TiO2 nanoparticles existed in the anatase phase and the titanoniobate nanosheets were still maintained after nitrogen doping. The obtained nitrogen-doped nanohybrids showed a greatly expanded surface area with a mesoporous structure and the doped nitrogen atoms were located in the interstitial sites of TiO2, giving rise to the visible light response. The catalytic activities of the obtained samples were evaluated by the photodegradation of rhodamine B (RhB) solution under visible light irradiation. The obtained N-doped nanohybrid had a higher activity than N-doped HTiNbO5 nanosheets and N-doped TiO2, indicating the synergetic effect of TiO2 nanoparticles and HTiNbO5 nanosheets. The dye molecules were mainly degraded to aliphatic organic compounds and mostly further mineralized to CO2 and/or CO, rather than being simply decolorized. In addition, the cell viability results of the HepG2 cells showed that the as-prepared sample had a good biocompatibility.

Self-assembled 3D architectures of NaCe(MoO4)2 and their application as absorbents

In this paper, various NaCe(MoO4)2 3D hierarchical architectures self-assembled from different building blocks were successfully synthesized by a facile EDTA-mediated hydrothermal method for the first time. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and N2 adsorption were employed to characterize the as-obtained products. Three important parameters, the amount of EDTA, pH value of the precursor solution and the molybdate resource were found to be important in determining the building blocks and their spacial arrangement in the final products. A plausible formation mechanism for the NaCe(MoO4)2 microflowers was proposed based on time-dependent experiments. As enlightened by the intrinsic property and fascinating hierarchical structures of NaCe(MoO4)2, a potential application of NaCe(MoO4)2 as an adsorbent in water treatment was also investigated for the first time. NaCe(MoO4)2 microflowers with bimodal pores exhibited a favorable adsorption performance for the removal of Rhodamine B (RhB), displaying a potential application in environmental remediation.

LaCO3OH microstructures with tunable morphologies: EDTA-assisted hydrothermal synthesis, formation mechanism and adsorption properties

Spiky ball- and triangular heart-like LaCO3OH microstructures were successfully prepared via a facile and mild hydrothermal route with the assistance of EDTA. The effect of reaction parameters such as chelators, reaction temperature and time on the product morphology was systematically investigated. It was found that the morphological modulation of the as-obtained products could be realized simply by changing reaction time. The possible formation mechanism for the stepwise self-assembly of spiky balls and triangular hearts was proposed on the basis of a series of time-dependent experiments. The adsorption properties of LaCO3OH spiky balls and triangular hearts for the removal of Rhodamine B (RhB) were evaluated. Due to the high specific surface area and complicated internal microstructure, the spiky balls exhibited a much higher adsorption rate and mass-specific adsorption capacity than bulk-shaped triangular hearts. However, a relatively higher area-specific adsorption capacity was found with bulk-shaped triangular hearts with a higher crystallinity. In addition, the adsorption kinetics of RhB by spiky balls follows the first-order reaction while that by triangular hearts zeroth-order, demonstrating the different adsorption behaviors of different microstructures.