A novel bilayer drug-loaded wound dressing of PVDF and PHB/Chitosan nanofibers applicable for post-surgical ulcers

A novel bilayer nanofibrous wound dressing, with enhanced mechanical properties is successfully fabricated. This membrane, consisted of polyvinylidenefluoride (PVDF) nanofibers for providing tensile strength and polyhydroxybutyrate/chitosan (PHB/CTS) nanofibers loaded with gentamicin with ability of controlled drug delivery, is a great choice for post-surgical ulcers. Mechanical properties showed dramatically improvement of tensile strength by addition of PVDF layer. Gentamycin release represented both an immediate and a sustained release of about 24?h and 1 week, respectively and release increment with increase of CTS ratio. Results also revealed that drug release in structures follow first order kinetic and Fickian release mechanism.     

Thiol-modified cellulose nanofibrous composite membranes for chromium (VI) and lead (II) adsorption

Oxidized cellulose nanofibers (CNF), embedded in an electrospun polyacrylonitrile (PAN) nanofibrous scaffold, were grafted with cysteine to increase the adsorption capability for chromium (VI) and lead (II). Thiol-modified cellulose nanofibers (m-CNF) were characterized by titration, FT-IR, energy dispersive spectroscopy (EDS) and SEM techniques. Static and dynamic Cr(VI) and Pb(II) adsorption studies of m-CNF nanofibrous composite membranes were carried out as a function of pH and of contact time. The results indicated these membranes exhibited high adsorption capacities for both Cr(VI) (87.5 mg/g) and Pb(II) (137.7 mg/g) due to the large surface area and high concentration of thiol groups (0.9 mmol of –SH/gram m-CNF). The morphology and property of m-CNF nanofibrous composite membranes was found to be stable, and they could be used and regenerated multiple times with high recovery efficiency.     

纳米碳纤维/碳毡负载碳化钨和碳氮化钨的肼分解性能

以纳米碳纤维/碳毡(CFF)为载体,分别采用碳热氢气还原法和碳热氨气还原法制备了负载型碳化钨、碳氮化钨整体催化剂,XRD结果表明催化剂的活性相分别为W₂C和WC_xN_y, TEM表征发现其粒子尺寸分别为2～40 nm和2～20 nm。采用1 N肼分解推力器评价了上述催化剂的反应性能,W₂C/CFF和WC_xN_y/CFF表现出了相比于Ir/CFF更好的肼分解综合性能:除了初活性略低以外,启动加速性、稳态燃压以及比活性均高于贵金属Ir催化剂。此外,W₂C/CFF和WC_xN_y/CFF催化剂的稳定性明显优于Ir/CFF,这主要是由于CFF载体在贵金属Ir的作用下发生了更显著的甲烷化反应。     

Controlling the initial phase of PECVD growth of vertically aligned carbon nanofibers on TiN

We explore the growth of vertically aligned carbon nanofibers by plasma enhanced chemical vapor deposition, using lithographically defined Ni catalyst seeds on TiN. TiN is selected for being an electrically conducting diffusion barrier suitable for the realization of electronic devices. We show that the rate of Ni diffusion correlates to both the level of oxygen content in the TiN film and to the film resistivity. The synthesis of the nanofibers was characterized using electron microscopy with an emphasis on three growth parameters: substrate temperature, plasma power, and chamber pressure. We propose that a catalyst surface free from carbon deposits throughout the process will induce diffusion-limited growth. The growth will shift towards a supply-limited process when the balance between acetylene, as the effective carbon bearing gas, and atomic hydrogen, as the main etching agent, is skewed in favor of acetylene. This determines whether the dominating growth mode will be vertically aligned ‘tip-type’ or disordered ‘base-type’, by affecting the competition between the formation of the first graphitic sheets on the catalyst surface and at the catalyst-substrate interface.     

Modification of the oxygen diffusivity in limiting current oxygen sensors

Effect of sacrificial carbon on microstructure of protective layer and sensing properties of limiting current oxygen sensors were studied. Graphite and carbon nanofiber with different concentrations were examined as sacrificial layer. Therefore, several YSZ-based electrochemical gas sensors were fabricated with dissimilarity in the diffusivity of the layer covering their measuring electrodes.Gas sensors were tested as potentiometric and amperometric devices under O₂-N₂ mixtures, and synthetic gases similar to the exhaust gas mixtures from combustion engines. Sensors with low diffusivity (low concentration of sacrificial material) exhibit more abrupt and O₂-sensitive potentiometric responses. Indeed, less O₂-linear amperometric responses and higher response times are their characteristics. Sensors with high diffusion in their layers (high concentration of sacrificial material) show a less abrupt step-drop potentiometric response but a more linear O₂ dependence for the amperometric response and, in general, lower response times.Results suggest that the configuration of the diffusive layer shall be controlled in terms of the expected performance of the sensor, as an amperometric or potentiometric device. The controlling parameters are discussed and given in this study.     

高效X光背光源靶材料的研究进展

靶材料的成分、微结构和密度是决定激光驱动X光背光源光子能量和强度的关键参数。基于此,介绍了背光源靶的分类、靶材料的制备及其与强激光的作用机制。背光源靶有着由稠密靶向欠稠密靶发展的趋势,其中,泡沫疏松靶以其操作安全和可选成分广泛等优点成为高效欠稠密靶。泡沫疏松靶材料又包含纳米纤维和气凝胶：纳米纤维是由静电纺丝结合热处理工艺制备的,具有成型性好、发光原子含量高等特点;而气凝胶靶则通过溶胶-凝胶技术结合超临界流体干燥工艺制备,其微结构均匀、理论转换效率高,但目前合成条件复杂、发光原子含量较低。结合多种溶胶-凝胶技术合成密度低、发光原子含量高的块体气凝胶将成为背光源制靶重要的研究方向。     

电纺PANI/PEO纳米纤维传感器制备与应用

采用静电纺丝法制备了聚苯胺/聚环氧乙烷（ PANI/PEO）纳米纤维,研究了电压、接收距离对电纺PANI/PEO纳米纤维直径的影响,对电纺参数进行了优化。通过对电纺接收端的控制,制备了平行纳米纤维阵列,实现了纳米纤维的定向排布;通过对电纺射流沉积次数的控制,制备了PANI/PEO纳米单纤维传感器,并对NH3进行了气敏性测试。结果表明：当电纺电压为20 kV且接收距离为20 cm时,获得的PA-NI/PEO纳米纤维直径为105 nm,且形貌较佳,在此优化参数条件下制备的单纤维PANI/PEO纳米传感器在常温下对低浓度的NH3有良好的线性响应输出。     

Characterizing Molecular Structure of Water Adsorbed by Cellulose Nanofiber Film Using in situ Micro-FTIR Spectroscopy

In situ micro-Fourier transform infrared (FTIR) spectra of a typical cellulose nanofiber (CNF) film (i.e., CNF with cellulose I structure) were collected within the full relative humidity (RH) range from 0% to 90%. Red shifts of two peaks at 1036 and 1204 cm^?1 and the variation of different spectra indicated the chemical adsorption sites for adsorbed water. From component band analysis of the spectral range of 2900–3700 cm^?1, three component peaks at 3293, 3397, and 3543 cm^?1 were due to strongly, moderately, and weakly hydrogen-bonded water. The signatures of these three types of hydrogen-bonded water were then observed to rise with an increase in RH. Based on growth regularities of these three types of hydrogen-bonded water, the water adsorption process of CNF film was divided into three stages; most of the water absorbed in these three stages was demonstrated to be CNF???HOH???CNF, WATER????HOH????WATER, and five-molecule tetrahedral structure, respectively.     

Alkali induced morphology and property improvements of TiO<Subscript>2</Subscript> by hydrothermal treatment

Alkali induced morphology and property improvements of TiO2 by hydrothermal reaction were investigated. The products were characterized by SEM, TEM, XRD, TG, EDX, FT-IR and DRS. The results indicate that, with the phase transformation from anatase to rutile, the morphologies changed from high aggregated particles to nanofibers with the diameter of about 100 nm and the length up to several tens of micrometers, meanwhile the process is controllable by manipulating the nature of the alkali, alkalinity and hydrothermal temperature. DRS analysis shows the property improvement of the nanofibers in the UV-Vis light absorption compared with the raw materials, implying the products have potential application in photocatalysis.