Xiuzhen Xiao

Controlled synthesis and luminescent properties of assembled spherical YPxV1−xO4:Ln3+ (Ln = Eu, Sm, Dy or Tm) phosphors with high quantum efficiency

YPxV1−xO4 (x = 0.3–0.9) assembled spheres with tetragonal phase were prepared hydrothermally under a simple and mild method with the assistance of EDTA. The structures and shapes of the prepared samples were significantly affected by the reaction conditions (hydrothermal treatment time, organic additive, pH value and the amount of EDTA in the synthesis solution). The characteristic emission of the spherical YPxV1−xO4:Ln3+ (Ln = Eu, Sm, Dy or Tm) phosphors were investigated in detail. The results showed that the light color of the YP0.3V0.7O4 microspheres can be easily adjusted by doping different lanthanide activators; Y0.93Sm0.07P0.3V0.7O4 and Y0.95Eu0.05P0.3V0.7O4 exhibited strong orange-red and red emission, respectively, and Y0.93Sm0.07P0.3V0.7O4 has a higher quantum efficiency of 76.8%. For the Y0.97Dy0.03PxV1−xO4 (x = 0.3–0.9) samples, both emission intensities of Dy3+ and VO43− increase with increasing the P amount, and the quantum efficiency of Y0.97Dy0.03P0.9V0.1O4 can reach 92%. It can also be found that the light color of the Y0.97Dy0.03PxV1−xO4 samples can be tuned by changing the ratio of P/V, and Y0.97Dy0.03P0.5V0.5O4 can emit white light under UV excitation.

Realization of a highly effective Pd–Cu–Clx/Al2O3 catalyst for low temperature CO oxidation by pre-synthesizing the active copper phase of Cu2Cl(OH)3

The Pd–Cu–Clx/Al2O3 catalysts (PCC) were prepared by a two-step impregnation (TI) method in organic solvent, wet impregnation (WI) method and NH3 coordination-impregnation (CI) method. The PCC-TI catalyst prepared by the two-step impregnation method (TI) exhibited much higher activity and stability for CO oxidation than the other catalysts, resulting from the smaller size of Cu2Cl(OH)3 and fewer carbonates deposited on the surface of PCC-TI catalyst. Using the PCC-TI catalyst, the complete conversion temperature of CO was 10 °C in the presence of 3.1% H2O. Among the three catalysts, the activation energy (Ea) of PCC-TI/ethanol was the lowest (27.1 kJ mol−1). The PCC-TI/ethanol prepared in ethanol solvent showed a higher activity compared with PCC-TI/methanol, due to much stronger interactions between the copper and palladium species. High concentrations of moisture and CO had a negative effect on the CO conversion. The former is due to excessive numbers of –OH groups (from H2O dissociation) which occupy the active sites of Pd and Cu, though –OH groups can work as part of the catalytic cycle, and the latter may originate from competitive adsorption and the presence of carbonates on the surface. We used DFT calculations to study the adsorption of H2O and CO on the surface, and the catalytic cycle of CO oxidation on the Pd species, revealing the possible routes for the formation of common species observed in the in situ DRIFTS spectra.

Effects of the preparation method on the performance of the Cu/ZnO/Al2O3 catalyst for the manufacture of L-phenylalaninol with high ee selectivity from L-phenylalanine methyl ester

The effects of the preparation method on the properties of Cu/ZnO/Al2O3 catalysts for L-phenylalanine methyl ester hydrogenation to L-phenylalaninol were investigated in detail, including the precipitation method and conditions (the aging time, calcination temperature and so on), with the help of ICP-OES, N2 and N2O adsorption, XRD, H2-TPR and TEM techniques. The results show that physicochemical properties of the catalysts are greatly affected by the preparation method and conditions. The uniform size distribution of CuO species can be obtained by fractional co-precipitation. The appropriate aging time is 2 h, and the catalyst aged for 2 h has the largest metallic copper surface area (SCu) and surface copper amount and the smallest CuO crystallites. The lower calcination temperature is favorable for increasing the surface area and metallic copper surface area of the catalyst. The spinel structure CuAl2O4 phase can form after calcination at 550 °C. The turnover frequency (TOF) values of L-phenylalaninol formed using different catalysts indicate the structurally sensitive character of the title reaction, and SCu is not the sole cause affecting the catalytic activities of the catalysts. B-TOF on the basis of the active sites (Cu0) in the boundary between CuO and ZnO or Al2O3 was proposed; the relationships of B-TOF with dCuO (particle size of CuO) and SCu were established. Using the Cu/ZnO/Al2O3 catalyst prepared by fractional co-precipitation with aging at 70 °C for 2 h and calcination at 450 °C for 4 h, 83.6% selectivity to L-phenylalaninol without racemization was achieved.

A highly effective and stable CuZn0.3MgxAlOy catalyst for the manufacture of chiral L-phenylalaninol: the role of Mg and its hydrotalcite-like precursor

Highly effective CuZn0.3MgxAlOy (x = 0–0.2) catalysts for the synthesis of chiral L-phenylalaninol derived from Cu-rich hydrotalcite-like precursors were prepared by a co-precipitation method with Na2CO3 as the precipitant, and their physicochemical and catalytic properties were characterized. The results show that the presence of Mg2+ ions can promote the formation of hydrotalcite-like (htl) precursors, and the Mg2+ content would affect the phase purity of the prepared htl precursors. The BET surface area, exposed copper surface area and amount of acid sites of the samples decreased with the increase in the molar ratio of Mg2+/Al3+. Also, the dense layered htl precursors are beneficial to the atomically uniform distribution of the corresponding metal oxides in the prepared catalysts, promoting the stronger interaction between Cu0 and Al2O3 after the catalysts were reduced (SMSI effect). The activity of the CuZn0.3MgxAlOy catalysts is greatly dependent on not only the metallic copper surface area, but also the SMSI effect and the acidity of the catalysts. When Mg2+/Al3+ = 0.1 (mol), a phase-pure htl precursor could be obtained, and after calcination, the prepared CZA-0.1 catalyst exhibited very excellent catalytic performance for the hydrogenation of L-phenylalanine methyl ester to chiral L-phenylalaninol. After 5 h of reaction at 110 °C and 4 MPa H2, 100% conversion of L-phenylalanine methyl ester and 91.1% yield of L-phenylalaninol with an ee value of ~100% were achieved. After recycling 13 times, the L-phenylalaninol selectivity of the CZA-0.1 catalyst only decreased by 7.2%.

The effects of PVP-modified SiO2 on the catalytic performance of CO hydrogenation over Rh–Mn–Li/SiO2 catalysts

Rh–Mn–Li catalysts supported on SiO2 prepared by PVP-modified Stober method were used for the synthesis of C2+ oxygenates from CO hydrogenation. The catalysts were characterized by TG, XRD, N2-adsorption–desorption, TEM, H2-TPR, in situ FT-IR, TPSR, and XPS. Activity testing results showed that the Rh–Mn–Li catalyst supported on the SiO2 modified by 1 g PVP exhibited the highest CO conversion and selectivity of C2+ oxygenates compared with other catalysts. Characterization results indicated that the addition of an appropriate amount of PVP is beneficial to the formation of weakly H-bonded hydroxyl groups on the surface of SiO2, which promotes Rh dispersion and weakens the Rh–Mn interaction. Furthermore, the higher Rh dispersion and the weaker Rh–Mn interaction promote CO absorption, enhance the CO dissociation ability and restrain the hydrogenation activity, which are favorable for the CO insertion into the metal–CHX band, finally resulting in excellent catalytic performance for C2+ oxygenates synthesis.

Synthesis of hydrophobic layered luminescent films: Organic–inorganic hybrid mono-n-dodecyloxy-phosphinyl-cerium (terbium)

With hydrophobic properties and ordered layered structures, mono-n-dodecyloxy-phosphinyl-cerium (terbium) (MDPCT) organic–inorganic hybrid materials were synthesized using cerium nitrate, terbium nitrate and mono-n-dodecyl phosphate (MDP) surfactant with three functions, hydrophobic group and phosphorus precursor, and characterized by XRD, SEM, TEM, FTIR and PLS. The results show that the solvent affects the interlayer spacing, crystallization and luminescent intensity of the prepared MDPCT materials. MDPCT prepared in water exhibits a more ordered layered structure and a higher degree of crystallinity, as well as stronger luminescent intensity than that prepared in ethanol. Based on the excellent solubility in organic solvents, this MDPCT hybrid luminescent material will be a promising candidate for potential biomedical applications in fluorescent imaging and analysis.

Influence of synthesis conditions on the morphologies of ReBO3 microstructures and white light emission of YBO3:Eu3+ phosphors prepared by an oleic acid-assisted hydrothermal method

Uniform ReBO3 (Re = Y, Dy, Ho, Er and Yb) spherical microstructures were successfully prepared by an oleic acid (OA)-assisted hydrothermal method. In the preparation process of YBO3, the solvent (water/ethanol) composition, OA amount, pH value, reaction temperature, the mole ratio of Y3+/BO33− and reaction time would affect the shape, size, crystallinity and structure of the prepared sample. Spherical, porous spherical and 3D hexagonal flowers of YBO3 crystals can be prepared by changing the synthesis factors, and their possible formation mechanisms were presented based on the experiment results. It is very interesting that YBO3:3%Eu3+ and YBO3:5%Eu3+ samples prepared by the OA-assisted method display a white light emission under excitation at 394 nm, and the quantum yield of the YBO3:5%Eu3+ sample can reach 44.59%. However, when the excitation wavelength is 270 nm, YBO3:5%Eu3+ shows orange-red emission and the quantum yield can reach 79.73%.These results may open up a new opportunity for YBO3:Eu3+ phosphors in the application of the white light emitting diodes (WLEDs).