Biocompatible Bacterial Cellulose-Poly(2-hydroxyethyl methacrylate) Nanocomposite Films

A series of bacterial cellulose-poly(2-hydroxyethyl methacrylate) nanocomposite films was prepared by in situ radical polymerization of 2-hydroxyethyl methacrylate (HEMA), using variable amounts of poly(ethylene glycol) diacrylate (PEGDA) as crosslinker. Thin films were obtained, and their physical, chemical, thermal, and mechanical properties were evaluated. The films showed improved translucency compared to BC and enhanced thermal stability and mechanical performance when compared to poly(2-hydroxyethyl methacrylate) (PHEMA). Finally, BC/PHEMA nanocomposites proved to be nontoxic to human adipose-derived mesenchymal stem cells (ADSCs) and thus are pointed as potential dry dressings for biomedical applications.

疏水纳米SiO_2对微管道流动特性的影响

通过微管道流动试验,探讨疏水纳米SiO_2的降压增注机理.在微尺度流动中,由于表面积/体积非常大,液固界面性质对流动有很大影响.在不同管壁界面条件下,用超纯水在内径约为25μm的毛细管内进行流动特性试验.结果表明:相同压力下,经过油基疏水纳米SiO_2试剂处理后,水在微管中的流量有了较明显地提高;疏水纳米SiO_2吸附能够使微管管壁具有超疏水性,从而产生水流滑移效应,达到减阻增流效果.

Electrical, electrochemical, and optical characterization of ceria films

Acceptor-doped ceria has been recognized as a promising intermediate temperature solid oxide fuel cell electrode/electrolyte material. For practical implementation of ceria as a fuel cell electrolyte and for designing model experiments for electrochemical activity, it is necessary to fabricate thin films of ceria. Here, metal-organic chemical vapor deposition was carried out in a homemade reactor to grow ceria films for further electrical, electrochemical, and optical characterization. Doped/undoped ceria films are grown on single crystalline oxide wafers with/without Pt line pattern or Pt solid layer. Deposition conditions were varied to see the effect on the resultant film property. Recently, proton conduction in nanograined polycrystalline pellets of ceria drew much interest. Thickness-mode (through-plane, z-direction) electrical measurements were made to confirm the existence of proton conductivity and investigate the nature of the conduction pathway: exposed grain surfaces and parallel grain boundaries. Columnar structure presumably favors proton conduction, and we have found measurable proton conductivity enhancement. Electrochemical property of gas-columnar ceria interface on the hydrogen electrooxidation is studied by AC impedance spectroscopy. Isothermal gas composition dependence of the electrode resistance was studied to elucidate Sm doping level effect and microstructure effect. Significantly, preferred orientation is shown to affect the gas dependence and performance of the fuel cell anode. A hypothesis is proposed to explain the origin of this behavior. Lastly, an optical transmittance based methodology was developed to obtain reference refractive index and microstructural parameters (thickness, roughness, porosity) of ceria films via subsequent fitting procedure.

Ultrafast dynamics in ZnO thin films irradiated by femtosecond lasers

The damage morphologies, threshold fluences in ZnO films were studied with femtosecond laser pulses. Time-resolved reflectivity and transmissivity have been measured by the pump-probe technique at different pump fluences and wavelengths. The results indicate that two-phase transition is the dominant damage mechanism, which is similar to that in narrow band gap semiconductors. The estimated energy loss rate of conduction electrons is 1.5 eV/ps. (c) 2005 Elsevier Ltd. All rights reserved.