Xianghui Wang

Synthesis of alginate derivative via the Ugi reaction and its characterization

In this research, the systematic evaluation of fundamental properties of the alginate derivative (Ugi-Alg) synthesized by the Ugi reaction is presented. The structure of Ugi-Alg with the degree of substitution of 23.24% was confirmed by FT-IR and (1)H NMR spectrometers. The X-ray diffraction (XRD) results indicate the amorphous structure and the crystal structure change of Ugi-Alg, which is possibly ascribed to the destruction of inter- and intra-molecular hydrogen bonding interactions during the Ugi reaction. From thermal gravimetric analysis (TGA) and fluorescence spectrophotometer, Ugi-Alg shows high thermal stability and good amphiphilic functionality with the critical aggregation concentration of 0.07 g/L in 0.15 mol/L aqueous NaCl solution. Transmission electron microscope (TEM) image and dynamic light scattering (DLS) reveal that stable Ugi-Alg self-aggregated micelle with the average size of 162.3 nm and ζ potential at about -31.7 mV could form in the aqueous media, which presents tremendous potential in pharmacology and tissue engineering.

Modification of montmorillonite by ball-milling method for immobilization and delivery of acetamiprid based on alginate/exfoliated montmorillonite nanocomposite

The objective of this study was to develop a sustained drug release system based on alginate/exfoliated montmorillonite nanocomposite for acetamiprid, a neonicotinoid insecticide, to improve its sustained release performance. Montmorillonite (MMT) was modified with cetyl trimethyl ammonium bromide (CTAB) using a ball-milling method. Then, acetamiprid was immobilized into the modified MMT layers through freeze-drying technology. Subsequently, the drug-loaded alginate-exfoliated MMT composite beads were prepared by dropwise addition of the mixture of the drug-loaded modified MMT and the alginate solution into the calcium chloride and chitosan blended solutions. The structure and surface morphology of the modified MMT and composite materials were determined by the means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), BET-specific surface area measurements, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analysis. The experiments on immobilization and release of acetamiprid were performed to examine the effect of the modified MMT on the properties of the composite beads. Experimental results showed the intercalation of CTAB into MMT has been successfully achieved during the ball-milling process, which was beneficial to the formation of exfoliated MMT nanocomposites in alginate matrix. The intensive force supplied during the superfine pulverization of the ball-milling process was effective to increase the modified MMT’s specific surface areas and decrease its particle size, consequently improving the drug-loading rate (DL) and encapsulation efficiency (EE) of the composite beads. The alginate/exfoliated MMT nanocomposite formulation exhibited a slow and sustained release property, which was demonstrated as a promising carrier material to promote the efficient use of organic pesticide, and thereby reduce environmental pollution.

Fabrication and evaluation of chitosan/NaYF4:Yb3+/Tm3+ upconversion nanoparticles composite beads based on the gelling of Pickering emulsion droplets

The rare earth ion doped upconversion nanoparticles (UCNPs) synthesized by hydrophobic organic ligands possess poor solubility and low fluorescence quantum yield in aqueous media. To conquer this issue, NaYF4:Yb3+/Tm3+ UCNPs, synthesized by a hydrothermal method, were coated with F127 and then assembled with chitosan to fabricate the chitosan/NaYF4:Yb3+/Tm3+ composite beads (CS/NaYF4:Yb3+/Tm3+ CBs) by Pickering emulsion system. The characterization results revealed that the as-synthesized NaYF4:Yb3+/Tm3+ UCNPs with an average size of 20nm exhibited spherical morphology, high crystallinity and characteristic emission upconversion fluorescence with an overall blue color output. The NaYF4:Yb3+/Tm3+ UCNPs were successfully conjugated on the surface of chitosan beads by the gelling of emulsion droplets. The resultant CS/NaYF4:Yb3+/Tm3+ CBs showed good upconversion luminescent property, drug-loading capacity, release performance and excellent biocompatibility, exhibiting great potentials in targeted drug delivery and tissue engineering with potential tracking capability and lasting release performance.

Removal of methylene blue using photocatalytic slurry reactor coupled with ceramic membrane cross-flow filtration process

Abstract By combining ceramic membrane cross-flow filtration process with photocatalytic reaction, a photocatalytic membrane reactor was designed. The reactor was simulated, and it was confirmed that it was a continuous stirred tank reactor. Experiment results indicated that, using a ceramic membrane with mean pore size of 0·1 µm, slurry TiO2 particles with mean size of 0·27 µm could be perfectly separated and recycled in the system, and the stable removal rate of methylene blue was more than 95% with TiO2 loading of 0·5 g L−1, reaction temperature of 45°C, filtration pressure of 0·5 kg cm−2 and cross-flow velocity of 3·3 m s−1.

Synthesis of Zn–Fe double metal cyanide complexes with imidazolium-based ionic liquid cocatalysts via ball milling for copolymerization of CO2 and propylene oxide

In this work, Zn–Fe double metal cyanide (DMC) catalysts were successfully synthesized via clean and efficient ball milling. Imidazolium-based ionic liquids as cocatalysts were incorporated into the structure of the DMC catalysts during the grinding process. The modified Zn–Fe DMC catalysts were effective for the alternating copolymerization of carbon dioxide and propylene oxide under controlled reaction conditions. The properties and structures of the Zn–Fe DMC catalysts and the resulting polymers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, elemental analysis, 1H and 13C NMR spectroscopy, gel permeation chromatography, and thermogravimetric analysis. The results indicate that the Zn–Fe DMC catalysts exhibit higher thermal stability compared to the DMC catalysts without imidazolium-based ionic liquids (DMC-Blank). We determined that the introduction of a small amount of imidazolium-based ionic liquids can increase the carbonate content of the poly(propylene carbonate) (PPC) copolymer in the range of 18.48–29.00%. The turnover numbers of PPC were ∼4.40. In addition, the measured number-average relative molecular mass was in the range of 2.96 × 103–4.98 × 103 with a narrow polydispersity index of 1.00–1.08.