Shirley Shen

Design and construction of polymerized-chitosan coated Fe3O4 magnetic nanoparticles and its application for hydrophobic drug delivery

In this study, a novel hydrogel, chitosan (CS) crosslinked carboxymethyl-β-cyclodextrin (CM-β-CD) polymer modified Fe3O4 magnetic nanoparticles was synthesized for delivering hydrophobic anticancer drug 5-fluorouracil (CS-CDpoly-MNPs). Carboxymethyl-β-cyclodextrin being grafted on the Fe3O4 nanoparticles (CDpoly-MNPs) contributed to an enhancement of adsorption capacities because of the inclusion abilities of its hydrophobic cavity with insoluble anticancer drugs through host-guest interactions. Experimental results indicated that the amounts of crosslinking agent and bonding times played a crucial role in determining morphology features of the hybrid nanocarriers. The nanocarriers exhibited a high loading efficiency (44.7±1.8%) with a high saturation magnetization of 43.8emu/g. UV-Vis spectroscopy results showed that anticancer drug 5-fluorouracil (5-Fu) could be successfully included into the cavities of the covalently linked CDpoly-MNPs. Moreover, the free carboxymethyl groups could enhance the bonding interactions between the covalently linked CDpoly-MNPs and anticancer drugs. In vitro release studies revealed that the release behaviors of CS-CDpoly-MNPs carriers were pH dependent and demonstrated a swelling and diffusion controlled release. A lower pH value led to swelling effect and electrostatic repulsion contributing to the protonation amine impact of NH3(+), and thus resulted in a higher release rate of 5-Fu. The mechanism of 5-Fu encapsulated into the magnetic chitosan nanoparticles was tentatively proposed.

Preparation of TiO2 loaded with crystalline nano Ag by a one-step low-temperature hydrothermal method

TiO2 loaded with crystalline nano silver (c-Ag/TiO2) was successfully synthesized by a one-step low-temperature hydrothermal method in aqueous solution using tetra-n-butyl titanate and AgNO3 as precursors. The structure and morphology were characterized by Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis absorption spectra (UV-Vis) and fluorescence spectra (FS). The photocatalytic activity was tested with photocatalytic degradation of hydrogen sulfide (H2S) gas. The results show that the nano silver particles of Ag/TiO2 prepared by the one-step low-temperature hydrothermal method are crystalline, while they are amorphous when prepared by the conventional UV reduction deposition method (a-Ag/TiO2). The photocatalytic activity of the c-Ag/TiO2 prepared by the hydrothermal method was found to have a significant improvement for H2S degradation, being more than 2 times over that of the a-Ag/TiO2 prepared by the conventional method.

Research and industrialization progress of recovering alumina from fly ash: A concise review

Fly ash, a by-product of high temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amount of industrial solid wastes generated in China. Its improper disposal has become an environmental problem. Now it is widely realized that fly ash should be considered as a useful and potential mineral resource. Fly ash is rich in alumina, making it a potential substitute for bauxite. With the diminishing reserves of bauxite resources, as well as the increasing demand for alumina, recovery of alumina from fly ash has attracted extensive attention world-wide. The present review describes, firstly, the generation and physicochemical properties of high alumina fly ash found in northern China and then focuses on the various alumina recovery technologies, the advantages and disadvantages of these processes, and in particular, the latest industrial developments. Finally, the directions for future research are also considered.

High electrical conductivity and elastic modulus composites comprising glass fiber-reinforced carbon-filled high-density polyethylene

Electrically conductive composites with very low percolation threshold values and high elastic modulus have been developed using single-screw extruder from short E-glass fiber (GF) reinforced carbon black (CB) filled high-density polyethylene (HDPE). The percolation threshold values of composites decreased with increased content of GF. The elastic modulus, tensile strength, and impact strength of composites were improved after addition of GF into CB/PE (PE, polyethylene). Three coupling agents, namely glycidyl methacrylate-grafted ethylene copolymer, maleic anhydride-grafted PE, and maleic anhydride-grafted polypropylene were used to study the effect on the conductivity and mechanical properties of GF/CB/PE composites. The tensile strength and modulus of composites increased after addition of coupling agent, meanwhile the conductivity of composites were decreased. The interface strength between GF and PE was improved after addition of coupling agent. The images of scanning electronic microscope showed that coupling agent improved the bonding between GF and matrix in an effective manner.

FACILE PREPARATION AND CHARACTERIZATION OF GRAPHENE NANOSHEET/POLYANILINE NANOFIBER THERMOELECTRIC COMPOSITES

Graphene nanosheet (GNs)/polyaniline (PANI) nanofiber composites were prepared by oxidative polymerization of aniline in a GNs dispersed 1 mol/L HCl solution. The phase composition of the composites was analyzed by Fourier Transform Infrared Spectroscopy and X-ray Diffraction. The thermoelectric properties of the composite powders, after cold pressing into pellets, were measured at room temperature. As the content of GNs increased from 0 to 40 wt.%, the electrical conductivity and Seebeck coefficient of the composite pellets increased simultaneously; especially the electrical conductivity increased dramatically from 15.4 to 120.1 S/cm. The highest power factor (~ 394.4 × 10-8 Wm-1K-2) was obtained from the 40 wt.% GNs/PANI composite sample, which is ~200 times as high as that of HCl-doped PANI.

Chitosan-based magnetic/fluorescent nanocomposites for cell labelling and controlled drug release

A chitosan-based drug delivery system, composed of Fe3O4 magnetic nanoparticles (MNPs), CdTe@ZnS quantum dots (QDs) and the anti-cancer drug doxorubicin (DOX), was designed and fabricated. The surfaces of MNPs were modified with carboxymethyl chitosan (CMCS) to minimise the possible fluorescence quenching triggered by magnetic cores. Glutaraldehyde was used as a crosslinking agent to create chemical covalent conjunction between different components, thus enhancing the stability of the obtained nanocomposites. The resulting nanocomposites retain favourable magnetic and fluorescence properties and can be used for bimodal cellular imaging. A sustained pH dependent DOX release with more release at pH = 5.3 was observed. The nanocomposites exhibited low cytotoxicity and CLSM images confirmed the cell fluorescence labelling properties and time-dependent cellular uptake. In summary, the chitosan-based nanocomposites developed in this work provided highly integrated functionalities and are promising for controlled drug delivery and also suitable for in situ cellular imaging.

Surface Wettability and Chemistry of Ozone Perfusion Processed Porous Collagen Scaffold

Crosslinking treatment of collagen has often been used to improve the biological stability and mechanical properties of 3D porous collagen scaffolds. However, accompanying these improvements, the collagen fibril surface becomes hydrophobic nature resulting in a reduced surface wettability. The wetting of the collagen fibril by culture medium is reduced and it is difficult for the medium to diffuse into the 3D structure of a porous collagen scaffold. This paper reports a ‘perfusion processing’ strategy using ozone to improve the surface wettability of chemical crosslinked collagen scaffolds. Surface wettability, surface composition and biological stability were analyzed to evaluate the effectiveness of this surface processing strategy. It was observed that ozone perfusion processing improved surface wettability for both exterior and interior surfaces of the porous 3D collagen scaffold. The improvement in wettability is attributed to the incorporation of oxygen-containing functional groups onto the surface of the collagen fibrils, as confirmed by X-ray Photoelectron Spectroscopy (XPS) analysis. This leads to a significant improvement in water taking capability without compromising the bulk biological stability and mechanical properties, and confirms that ozone perfusion processing is an effective tool to modify the wettability both for interior and exterior surfaces throughout the scaffold.

Thermoelectric Properties of Flexible PEDOT:PSS/Polypyrrole/Paper Nanocomposite Films

Flexible poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polypyrrole/paper (PEDOT:PSS/PPy/paper) thermoelectric (TE) nanocomposite films were prepared by a two-step method: first, PPy/paper nanocomposite films were prepared by an in situ chemical polymerization process, and second, PEDOT:PSS/PPy/paper TE composite films were fabricated by coating the as-prepared PPy/paper nanocomposite films using a dimethyl sulfoxide-doped PEDOT:PSS solution. Both the electrical conductivity and the Seebeck coefficient of the PEDOT:PSS/PPy/paper TE nanocomposite films were greatly enhanced from 0.06 S/cm to ~0.365 S/cm, and from 5.44 μV/K to ~16.0 μV/K at ~300 K, respectively, when compared to the PPy/paper TE nanocomposite films. The thermal conductivity of the PEDOT:PSS/PPy/paper composite film (0.1522 Wm−1K−1 at ~300 K) was, however, only slightly higher than that of the PPy/paper composite film (0.1142 Wm−1K−1 at ~300 K). As a result, the ZT value of the PEDOT:PSS/PPy/paper composite film (~1.85 × 10−5 at ~300 K) was significantly enhanced when compared to that of the PPy/paper composite film (~4.73 × 10−7 at ~300 K). The as-prepared nanocomposite films have great potential for application in flexible TE devices.

The Relationship Between the TiO2 Photocatalyst Deactivation, Regeneration and the Concentration of the Surface Adsorbed SO42-

The photolysis ability and adsorption ability of TiO2 was detected and measured using acetaldehyde as a probe. The quantitative relationship between the TiO2 deactivation and the concentration of the surface adsorbed SO42- was obtained by intentional controls of the concentrations of the surface adsorbed SO42-. When the concentration of the surface adsorbed SO42- reached 2.0 wt%, the photolysis ability of the TiO2 photocatalyst decreased by 50%, and when the concentration was 2.9 wt%, the TiO2 adsorption ability decreased by 50%. 90% of the absorbed SO42- can be removed after the samples have been washed by overflowing water for 2 hours at a rate of 2 L.min-1 and the photocatalytic activity can be regenerated. This work will help to predict the lifetime of TiO2 photocatalyst in actual applications as well as to understand its regenerations of the photocatalytic capability.

Preparation and Characterization of Innate Super-Hydrophilic TiO2/SiO2 Thin Films

Unlike photo-induced super-hydrophilic inorganic thin films, non-photoinduced innate super-hydrophilic TiO2/SiO2 thin films have been successfully prepared in this work. SiO2/TiO2 thin films were prepared by solgel method via adding hydrophilic fumed silica to TiO2 sol and characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle meter. The results show that the super-hydrophilicity of the as-prepared thin films can maintain for one month without light irradiation, and the thin films have excellent antifogging property as well.