Papers by Author: Zhong Zi Xu

Abstract: The novel photocatalyst of α-Fe₂O₃/Sb-doped SnO₂ (ATO) nanocomposites were fabricated by two-step process of hydrothermal and precipitation method. The structure, size, magnetic behavior and absorption property were characterized by XRD, TEM, VSM and UV-Vis absorption spectrum. The composites with low mole ratio of ATO have more pronounced photocatalytic activities. The optimum photocatalytic activity in our experiments appears at the mole ratio of n_Fe:n_Sn=1:0.25. The α-Fe₂O₃/Sb-doped SnO₂ nanocomposites have better photocatalytic activities than α-Fe₂O₃/SnO₂ nanocomposites. The results show that the doping of Sb ions can improve the capture ability of electrons and consequently enhance the photocatalytic activities of the composite system.

Abstract: We reported the preparation of cubic (α-) and hexagonal (β-) NaYF₄ particles in high boiling organic solvents 1-octadecene (ODE) and oleic acid (OA), through a thermal decomposition synthetic route. The as-prepared products were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL) spectra. By tuning the reaction temperature and time, we could manipulate the morphology, size, and crystal phase of the products. It was found that the α→β phase transition was favored by high reaction temperature and long reaction time. Highly uniform β-NaYF₄ hexagonal submicroplates were obtained from α-NaYF4 nanoparticles by prolonging the reaction time. The Yb³⁺-Tm³⁺ co-doped β-NaYF₄ hexagonal submicroplates showed s_{Subscript text}trong blue _{Subscript text}and weak red upconversion luminescence under 980nm laser diode excitation. In addition, the dependence of the UC emission intensities upon pump power was investigated.

Abstract: Layered SmBaCo₂O_5+δ with the cation-ordered double perovskite structure were synthesized by the solid-state reaction route and characterized by thermal analysis, X-ray diffraction, infrared spectrum, electrical conductivity and infrared emissivity. The Sm_1-xBa_xCoO₃ (SBCO) system shows the different crystal structures with the variation of barium content, which results in the different electrical behavior. The electrical conductivity reaches maximum when x is 0.5 with SmBaCo₂O_5.54 phase. The infrared absorption occurs at about 600 cm^-1 for all the samples which were attributed to Co-O stretching modes. The peak shifted to a lower frequency with the increase of doping level. In addition, the comparison of electrical and emissivity measurements suggested that variation of infrared emissivity is in agreement with the electrical properties.

Abstract: Sm₂(WO₄)₃ crystals have been synthesized through liquid-phase reaction. The structure, morphology and optical properties of the products have been investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer, SEM, and spectrofluorometer, respectively. The compound crystallized in the monoclinic hexagonal system, space group C2/c. Heat treat promoted the crystallization and regulated the micro-structure of Sm₂(WO₄)₃. In the Sm₂(WO₄)₃ host, the WO₄^2- group could transfer the energy of near-UV light to Sm³⁺ ions, emitting blue, green and red light at 429 nm (⁶P_5/2→⁶H_5/2), 453 nm (⁴G_9/2→⁶H_5/2), 495, 507 nm (⁴G_7/2→⁶H_5/2), 563 nm (⁴G_5/2→⁶H_5/2), 601 nm ( ^4G_5/2→⁶H_7/2) and 649 nm ( ^4G_5/2→⁶H_9/2), respectively. The ratio of blue, green and red light was appropriate to achieve white light. The Sm₂(WO₄)₃ powders have potential to act as UV absorber for solar cell and may be helpful to the development of white light LED.

Abstract: In this paper, setting 1.06 μm Gaussian modulated pulse electromagnetic wave as irradiation sources, the influences of structural parameters on reflectivity are analyzed by finite different time domain (FDTD) method. The results show that the filled factor and height are key factors for circular tube relief structure with non absorption. The optimal height could be set to 0.2 μm, which is one odd time of the ratio of incident wavelength λ and four equivalent refractive index 4N, then the best filled factor is between 0.7 and 0.9, the ratio of inner and outer diameter could be set between 0.4 and 0.6, and the structure period has little significant influence. Compared with cylinder solid structure, it has been discovered that circular tube hollow structure could weaken the backward energy of electromagnetic wave, and it would be more suitable for antireflection structure than solid cylinder structure. Moreover, we design two another circular tube relief structures simulations with different extinction coefficients, it is found that the reflectivities are lower up to 0.00016% than the non absorption one.

Abstract: For the first time, nano-scale rods of NaLaxYb9-x(SiO4)6O2 (x=1,3,5,7,9) crystals (NLS) activated with Er3+ have been synthesized through a mild hydrothermal conditions with subsequent calcination. The as-obtained products were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results indicate that the compound has an apatite structure and crystallizes in the hexagonal system, space group P63/m. The excitation spectrum and emission spectrum were also emplyed to investigate the optical properties of the nano-rods. The Er3+ doped NLS exhibit green/red up-conversion luminescence under excitation with a diode laser at 980 nm.

Abstract: The amorphous calcium phosphate (ACP)/tricalcium silicate (Ca3SiO5, C3S) composite powders were synthesized in this paper. The exothermal behavior of C3S determined by isothermal conduction calorimetry indicated that the ACP could be synthesis by chemical precipitation method during the induction period (stage II) of C3S. The composite powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicated that nanosized ACP particles deposited on the surface of C3S particles to form core-shell structure at pH=10.5, and the nCa/nP of ACP could be controlled between 1.0 and 1.5. The core-shell structure is stable after sintered at 500 oC for 3 h to remove the β-cyclodextrin (β-CD). As compared with the irregular C3S particles (1~5 μm), the composite powders particles are spherical with a diameter of 40~150 μm. Therefore, to obtain the smaller size of composite powders, it is expected to avoid the aggregate of C3S particles in the aqueous solution by addition of dispersant. As compared with C3S, the composite powders may contribute better injectability, strength and biocompatibility.

Abstract: TiO2, ZrO2 and titanium oxide in deficiency oxygen environment were used to modify the surface of biomedical NiTi stents. The coatings were prepared by vacuum deposition. The surface microstructures and characteristics, blood compatibility of the modified stents in simulated body fluids were assessed using scanning electron microscopy (SEM), hemolysis test, coagulation test and blood platelet adhesion test. The hemocompatiblity of the modified stents were all improved by layer coating. Enhancement of blood compatibility was believed to stem from the improved surface water affinity and hemolysis resistance of the layer, and titanium oxide in deficiency oxygen environment displayed better. This study indicated that layer coating was a promising effective modification method for improving the surface properties of biomedical NiTi alloy intravascular stents. As a coating materials，titanium oxide in deficiency oxygen environment was better than TiO2 and ZrO2.

Abstract: In this article, Sm(Sal)xPhen, SmyY1-y(Sal)3Phen were synthesized and its films were prepared. They were characterized by infrared spectra (IR), ultra-violet visible spectrometer (UV), X-ray diffraction (XRD) and fluorescence spectroscopy. Sm/Y complexes and its mixture doped with the polyvinyl alcohol (PVA) showed photoluminescence at the wavelength of 646 nm. There was an excellent compatibility among Sm/Y complexes, the polyvinyl alcohol (PVA) and dimethyl sulphoxide (DMSO), which were used to prepare the resin film. The results indicated that Sm/Y rare earth light conversion films were better light conversion films with good compatibility in resins, and with emission wavelength suitable for plants’ photosynthesis.

Abstract: The bioactivity of potassium titanate whiskers (PTW) was evaluated by soaking in simulated body fluids (SBF, Kokubo solution). At first, PTW was chemically treated by 1 M HCl and 1 M NaOH solutions at 60 oC for 48 h, respectively. Then PTW before and after treated were soaked in SBF solution and cultured at 37 oC for different times. The apatite deposit on PTW was examined by FTIR and SEM/EDX. The results showed that there was not apatite deposit on the raw PTW even after soaked for 14 days while apatite appeared on the treated PTW after soaked for only 7 days. This implies that treatment by HCl/NaOH solutions can improve the in vitro bioactivity of PTW. The possible mechanism is that more Ti–OH groups occur after treatment and induce Ca2+ and PO4 3- aggregate and accelerate to deposit of apatite. The bioactive PTW with good biocompatibility is a potential candidate as reinforcing agent to improve the mechanical properties of calcium phosphate ceramics or cements.