Xuetao Luo

Methotrexate-Loaded PEGylated Chitosan Nanoparticles: Synthesis, Characterization, and in Vitro and in Vivo Antitumoral Activity

Cancer nanotherapeutics are rapidly progressing and being implemented to solve several limitations of conventional drug delivery systems. In this paper, we report a novel strategy of preparing methotrexate (MTX) nanoparticles based on chitosan (CS) and methoxypoly(ethylene glycol) (mPEG) used as nanocarriers to enhance their targeting and prolong blood circulation. MTX and mPEG-conjugated CS nanoparticles (NPs) were prepared and evaluated for their targeting efficiency and toxicity in vitro and in vivo. The MTX-mPEG-CS NP size determined by dynamic light scattering was 213 ± 2.0 nm with a narrow particle size distribution, and its loading content (LC %) and encapsulation efficiency (EE) were 44.19 ± 0.64% and 87.65 ± 0.79%, respectively. In vitro release behavior of MTX was investigated. In vivo optical imaging in mice proved that MTX was released from particles subsequently and targeted to tumor tissue, showing significantly prolonged retention and specific selectivity. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay obviously indicated that the higher inhibition efficiency of MTX-mPEG-CS NPs meant that much more MTX was transferred into the tumor cells. A significant right-shift in the flow cytometry (FCM) assay demonstrated that MTX-loaded nanoparticles were far superior to a pure drug in the inhibition of growth and proliferation of Hela cells. These results suggest that MTX-mPEG-CS NPs could be a promising targeting anticancer chemotherapeutic agent, especially for cervical carcinoma.

Boron removal from metallurgical silicon using CaO-SiO2-CaF2 slags

Natural Science Foundation of Fujian Province, China [2007J0012]; Key Technological Program of Fujian Province, China [2007HZ0005-2]

Sonocrystallization of ZIF-8 on Electrostatic Spinning TiO2 Nanofibers Surface with Enhanced Photocatalysis Property through Synergistic Effect

Semiconductor-metal-organic framework (MOF) hybrid photocatalysts have attracted increasing attention because of their enhanced photocatalytic activity. However, the effect of the interface reaction between semiconductor and MOFs is rarely studied. In this work, we studied the synthesis and photocatalytic activity of zeolitic imidazolate framework-8 (ZIF-8) decorated electrostatic spinning TiO2 nanofibers (TiO2 ESNFs). TiO2/ZIF-8 hybrid photocatalysts were prepared via a facile sonochemical route. It was crucial that the ZIF-8 was assembled homogeneously on the surface of TiO2 ESNFs and formed a N-Ti-O bond under sonochemical treatment, which may result in reducing recombination of the electron-hole pairs. The chemically bonded TiO2/ZIF-8 nanocomposites displayed excellent performance of thermal stability, controllable crystallinity, and great enhancement of photocatalytic activity in Rhodamine B (Rh B) photodegradation. Furthermore, the UV-vis light adsorption spectra of TiO2/ZIF-8 nanocomposites showed that the ZIF-8 photosensitizer extended the spectral response of TiO2 to the visible region. The new strategy reported here can enrich the method for designing new semiconductor-MOF hybrid photocatalysts.

Preparation and properties of polymer matrix piezoelectric composites containing aligned BaTiO3 whiskers

A piezoelectric composite has been prepared with highly aligned BaTiO3 whiskers as the active phase and polyvinylidene fluoride (PVDF) as the matrix. Its dielectric and electromechanical properties are characterized. It is found that the dielectric constant (ε), piezoelectric constant (d33) and remnant polarization (Pr) are considerably higher in the whisker composite than in the corresponding composite containing BaTiO3 powders as the active phase, while the loss factors follow the opposite trend. For the whisker composite, ε, d33 and Pr along the direction of the whisker orientation are much higher than the values normal to the whisker orientation. The reasons for the observed differences are discussed.

Preparation of YAG : Ce3+ phosphor by sol-gel low temperature combustion method and its luminescent properties

Abstract YAG:Ce 3+ phosphor was prepared by sol-gel low-temperature combustion method. The effects of the precursor properties and calcining temperature on the crystallization process, microscopic morphology and luminescent properties of phosphor were studied. The results indicate that the pure phase of YAG can be obtained at 800 °C by sol-gel low temperature combustion method, using citric acid as complexing agent. When the molar ratio of metal ion to citric acid is 2.0 and pH value is 2, the crystallinity increases and the phosphor particle size grows up gradually with the increase of the calcining temperature. The powders were characterized through thermal analysis, X-ray diffraction analysis and scanning electron microscope analysis. The excitation spectra of YAG:Ce 3+ phosphor take on a double peak structure, and the peak value of the main excitation spectra occurs at 460 nm and that of the emission spectra is near 530 nm. With the gradual increase of the calcining temperature, the peak position of excitation and emission spectra remains basically unchanged, but its relative intensity increases gradually.

Crystallization, morphology and luminescent properties of YAG : Ce3+ phosphor powder prepared by polyacrylamide gel method

Abstract A novel synthesis process, based on the polyacrylamide gel method, was used to prepare Ce-doped YAG phosphor powders. Effects of heat treatment parameters, temperature and holding time, the fluxes, and atmosphere on microstructure and particle morphology as well as luminescent properties of YAG:Ce3+ phosphor powders were studied by X-ray powder diffractomctry, scanning electron microscopy, and fluorescence spectrophotometry. The results show that the formation temperature (1000 °C) of pure YAG phase is significant low when being synthesized by the polyacrylamide gel method, compared with solid-state reaction. For luminescent properties, the intensity of emission of YAG: Ce3+ phosphor increases steadily with increasing temperature from 900 °C to 1300 °C and prolonging holding time from 100 min to 400 min. But blue shift phenomenon is observed for 400 min calcination. Fluxes as BaF2 and H3BO3 can enhance the intensity of emission of phosphor due to the improvement of crystallization of YAG and the stabilization of trivalence cerium ion in YAG host lattice at high temperature. Weak reduction atmosphere can contribute to improvement of the emission intensity of YAG: Ce3+ phosphor powders.

Elimination of phosphorus vaporizing from molten silicon at finite reduced pressure

Natural Science Foundation of Fujian Province, China [2007J0012]; Key Technological Program of Fujian Province, China [2007HZ0005-2]; Norwegian Research Council [BASIC-10341702]

Fabrication of SiO2@silicalite-1 and its use as a catalyst support

SiO2@silicalite-1, using silica sol (pH = 9.47, SiO2 ≈ 30 wt%) as the silica source, was directly synthesized in a eutectic mixture where silicalite-1 grains were formed in the three-dimensional net structure of silica gel, grown in situ by transforming amorphous SiO2 into an MFI-type structure and coated with amorphous SiO2. The alkalinity, template agent, and crystallization time strongly affect the physicochemical properties of SiO2@silicalite-1. The physicochemical properties of these samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra and nitrogen adsorption. The results show that the SiO2@silicalite-1 is synthesized in a eutectic mixture and its physicochemical properties can be tuned by controlling the content of sodium hydroxide and tetrapropyl ammonium bromide (TPABr). A time-dependent study reveals that the formation process obeys an in situ epitaxial growth and phase transformation mechanism. Finally, SiO2@silicalite-1 was used as the support to prepare TiO2-loaded SiO2@silicalite-1 (TiO2@SiO2@silicalite-1). After five loading procedures, it could load 0.44% TiO2 nanoparticles, which is higher than the TiO2 nanoparticle loading in traditional silicalite-1 (0.13%). When the catalysts were used as a catalyst for the degradation of rhodamine B (RhB) aqueous solution under UV light, the photocatalytic efficiency of TiO2@SiO2@silicalite-1 (89.2%) is higher than TiO2@silicalite-1 (only 34.6%). The rate of degradation using TiO2@SiO2@silicalite-1 is 4.3 times faster than that using TiO2@silicalite-1. Furthermore, SiO2@TiO2@silicalite-1 exhibits high stability of photocatalytic performance. After five repeated cycles, the photocatalytic efficiency of TiO2@SiO2@silicalite-1 is 88.09%, which reduces only by 1.1%.

Effects of Slag Refining on Boron Removal from Metallurgical-Grade Silicon Using Recycled Slag with Active Component

A new slag refining method to remove boron from metallurgical silicon (MG-Si) by mixed reused slag and active component was proposed. The silicon was refined with CaCl2-CaO-SiO2 slag system in this work. The boron removal efficiency under different temperature and holding time was investigated, particularly for the recycle of the used slag mixed with different amount of CaCl2 in the 2nd and the 3rd run. The multiple slag refining was adopted to test the effect of reused slag; the boron removal ratio was 96% and 94% at 1923 K and 1873 K, respectively. These methods could significantly reduce the slag amount in refining. The total transfer coefficient of boron was also derived by the boron content. The overall boron removal mechanism and effect of slag recycle on boron removal was also discussed.

Fabrication and characterization of SiO2@TiO2@silicalite-1 catalyst and its application for degradation of rhodamine B

SiO2@TiO2@silicalite-1 catalyst, with TiO2 (Degussa P25) nanoparticles encapsulated by SiO2 and adhered on the surface of silicalite-1 zeolite, was successfully fabricated by combining pressing, sintering and infiltration methods. The samples were characterized by XRD, SEM, FT-IR, TEM, nitrogen sorption, and UV-vis diffuse reflectance spectra. The photocatalytic properties were investigated by degradation of rhodamine B (RhB) aqueous solution under UV light. The results show that TiO2 nanoparticles are coated with a SiO2 shell and bonded together. The core/shell structure of TiO2@SiO2 is attached to the surface of silicalite-1 particles. The photocatalytic efficiency of TiO2@silicalite-1 is 97.4%. When the catalyst is coated with SiO2, its photocatalytic efficiency is significantly improved to 99.7%. Furthermore, the rate of degradation using SiO2@TiO2@silicalite-1 is 1.54 times faster than that using TiO2@silicalite-1.