Electrospun Cellulose Nanocrystals/Polycaprolactone Nanocomposite Fiber Mats

Cellulose nanocrystals (CNCs), a kind of biocompatible and biodegradable nanofiller, were prepared by sulfuric-acid hydrolysis of commercial α-cellulose. CNC/ polycaprolactone (PCL) nanocomposite fiber mats were produced via electrospinning and characterized by scanning electron microscopy, differential scanning calorimetry (DSC) analysis, thermogravimetric analysis (TGA), uniaxial tensile tests, and static water-contact-angle analysis. The results showed the mechanical properties and thermal stability of the nanocomposite fiber mats were improved and the surface hydrophilicity was increased in comparison with neat PCL fiber mats.     

Visible Light Photocatalytic Functional TiO2/PVDF Nanofibers for Dye Pollutant Degradation

The photodegradation of poly(vinylidene fluoride) (PVDF)/titanium oxide (TiO₂) nanofibers under visible light is described, something that has not been previously reported in the literature. Visible light photocatalytic electrospun PVDF/TiO₂ nanofiber webs with anatase TiO₂ concentration varying from 0% to 20% (0%, 1%, 3%, 5%, 10%, and 20%) are produced, and their ability to degrade a toxic pollutant, Rhodamine B (RhB), is studied. Photodegradation study using UV–vis spectroscopy on PVDF/TiO₂ nanofiber webs (with TiO₂ concentration of 20%) shows that 80% of RhB is degraded within 6 h at the wavelength of 546 nm, which clearly falls within the visible spectra. The color of RhB solvent catalyzed by PVDF/TiO₂ nanofiber webs gradually changes from red to orange, then to yellow, further to light yellow till colorless, which suggests the complete photodegradation of RhB under visible light. To estimate the rate of photodegradation, the reaction constant k is calculated. Based on the k value, PVDF/TiO₂ nanofiber webs with 20% TiO₂ concentration show the highest degradation rate compared to other PVDF/TiO₂ nanofiber webs and pure TiO₂ nanoparticles. This study proves the viability of TiO₂‐based nanofibers to have catalytic capabilities under low‐energy visible light.     

Computational-Based Approach for Predicting Porosity of Electrospun Nanofiber Mats Using Response Surface Methodology and Artificial Neural Network Methods

Comparative studies between response surface methodology (RSM) and artificial neural network (ANN) methods to find the effects of electrospinning parameters on the porosity of nanofiber mats is described. The four important electrospinning parameters studied included solution concentration (wt.%), applied voltage (kV), spinning distance (cm) and volume flow rate (mL/h). It was found that the applied voltage and solution concentration are the two critical parameters affecting the porosity of the nanofiber mats. The two approaches were compared for their modeling and optimization capabilities with the modeling capability of RSM showing superiority over ANN, having comparatively lower values of errors. The mean relative error for the RSM and ANN models were 1.97% and 2.62% and the root mean square errors (RMSE) were 1.50 and 1.95, respectively. The superiority of the RSM-based approach is due to its high prediction accuracy and the ability to compute the combined effects of the electrospinning factors on the porosity of the nanofiber mats.     

聚丙烯腈纳米纤维毡上生长ZnSe纳米晶的结构及发光特性

通过静电纺丝制备聚丙烯腈(PAN)纳米纤维毡,采用水热法在二乙烯三胺和去离子水的混合溶剂中于180℃下制备ZnSe/聚丙烯腈纤维纳米毡复合材料。使用扫描电镜(SEM)、X射线衍射(XRD)、荧光光谱等分析方法对ZnSe/聚丙烯腈复合材料进行表征。结果表明,ZnSe/聚丙烯腈复合材料的形貌较复杂,既有直径10～100 nm,长度50～500 nm的纳米捧,也存在4～10μm左右的ZnSe微米花。260 nm波长光激发下ZnSe/聚丙烯腈复合材料的发射光谱包括位于351 nm(3.55 eV)的弱近紫外激子峰和位于427 nm(2.91 eV)的宽谱带缺陷发光峰,二者相对于ZnSe晶体的本征发射带468 nm均有明显的蓝移效应。     

Production and Characterization of Zirconia (ZrO2) Ceramic Nanofibers by Using Electrospun Poly(Vinyl Alcohol)/Zirconium Acetate Nanofibers as a Precursor

Zirconia (ZrO₂) inorganic ceramic nanofibers were produced using electrospinning of the poly(vinyl alcohol)/zirconium acetate as a precursor followed by calcinating and sintering to decompose the polymer and turn the metal salt (zirconium acetate) into the metal oxide. Characterization of the nanofibers, including polymer thermal decomposition, chemical and crystal structure, phase transformations, and fiber morphology were investigated by simultaneous thermal analysis (STA), thermomechanical analysis (TMA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The results showed that the polymer decomposition started at 250°C and zirconia nanofibers with different phases (tetragonal and monoclinic) were obtained by the calcination of the precursor nanofibers at various temperatures between 500°C and 1100°C. The initially crystallized zirconia phase, which formed at 500°C, was tetragonal and with increasing calcination temperature, zirconia nanofibers with increasing amount of monoclinic phase were formed. Consequently, at 1100°C, the tetragonal phase disappeared and was transformed to the monoclinic phase of the zirconia completely. Increasing the calcination temperature caused the fiber average diameter decrease and grain growth took place due to the removal of the polymer and organic groups; neighboring grains sintered to each other and formed fibers with a high aspect ratio. At 1100°C the grains size was about the same as the fiber diameter.     

Sustained Release of Protein Particle Encapsulated in Bead-on-String Electrospun Nanofibers

The feasibility of alleviating burst release of electrospun bead-on-string nanofiber scaffolds loaded with protein particles was evaluated, including an investigation of the influence of the beads number on the release profile. Bovine serum albumin–loaded dextran particles were used as the model drug and poly(lactic-co-glycolic acid) as the polymer to fabricate the bead-on-string nanofiber scaffolds by electrospinning. Both the bead structure and the distribution of the particles in the beads were examined by scanning electron, transmission electron, and fluorescence microscopy. The results of fluorescence microscopy suggested that the particles were well encapsulated by the beads of the fibers. In vitro release tests showed that a more sustainable release profile with less initial burst release could be obtained from the bead-on-string fibers than from smooth fibers with uniform diameter. In addition, when the number of the forming beads was not numerous enough to encapsulate all the particles in the suspensions, the release performance worsened because the surplus particles were not properly encapsulated.     

聚合物前驱体制备氮化硅纳米纤维及其发光

由聚硼硅氮烷前驱体在高温常压下热裂解得到氮化硅纳米纤维,确定了样品结构为α相,讨论了纳米纤维的生长模式属于气-液-固生长机制。在室温下用488nm激光对样品激发,观察到样品有很宽的强光致发光带,并有两个发光中心,这种强的可见光致发光主要来自氮化硅的内禀Si和N的悬键。测量了纳米纤维的室温吸收光谱,得到氮化硅纳米纤维的光学带隙为4．80eV。     

Facile Synthesis via Electrospinning of a Tetraethoxysilane/Polyvinylpyrrolidone Sol and Characterization of Ultrafine Crystalline SiO2 Nanofibers

Silica nanofibers were developed by a combination of an electrospinning technique and the sol–gel method. In the process, tetraethoxysilane (TEOS), polyvinylpyrrolidone (PVP) and N, N-Dimethylformamide (DMF) were the components of the sol for the production of silica/PVP composite nanofibers by electrospinning. During a thermal treatment, PVP in the hybrid fibers was removed; in this way, we produced ultrafine crystalline silica nanofibers. Scanning electron microscopy, energy dispersive X-ray analyzer, X-ray diffraction, and Fourier transform infrared spectroscopy were used to characterize the nanofibers. These silica nanofibers should be potentially useful in catalyst support, adsorbent, energy storage, and gas storage applications.     

键合型PU/Eu(Cit)Phen荧光纳米纤维制备与表征

合成了含-OH(羟基)的Eu(Cit)Phen(铕-柠檬酸-邻菲咯啉)三元配合物与端-NCO(异氰酸酯)基PU(聚氨酯)预聚物,通过一OH与一NCO间加成反应及l,3.丙二醇扩链反应制备键合型PU/Complex稀土高分子材料,将其溶液经静电纺丝制得具有荧光性能的纳米纤维.采用FT-IR、SEM、XRD、DSC和PL对...     

Electrospun fluorescein/polymer composite nanofibers and their photoluminescent properties

Fluorescein/polyvinyl pyrrolidone (PVP) composite nanofibers with different fluorescein loadings (with a weight concentration of 0-5.0%) are fabricated via electrospinning. Morphologies, structures and photoluminescent (PL) properties of these straight, helical or wavelike fibers are characterized by scanning electron microscopy (SEM), fluorescence microscopy and a spectrophotometer. It is found that the maximum emission of the as-spun fluorescein/PVP fibers occurs at 510 nm. The PL intensity of the composite fiber increases with fluorescein concentration, then fluorescence quenching appears when the concentration reaches 1.67%. The mechanism of fluorescence quenching of fluorescein is discussed. In addition, the composite fibers exhibit a much stronger PL intensity than fluorescein/PVP bulk film owing to larger specific surface area, which makes them promising materials for biomedical applications such as probes and sensors.     

Fabrication and Optimization of Poly(vinyl alcohol)/Zirconium Acetate Electrospun Nanofibers Using Taguchi Experimental Design

This paper presents an investigation regarding poly(vinyl alcohol)/zirconium acetate (organic–inorganic) (PVA/Zrace) nanofibers prepared by electrospinning which could be used as a precursor for fabricating ceramic metal oxide nanofibers. The effect of some processing variables, including polymer solution concentration, tip to collector distance and applied voltage of electrospinning, and the amount of Zrace and their interactions, on the diameter of the nanofibers were studied. Taguchi experimental design and a statistical analysis (ANOVA) were employed and the relationship between experimental conditions and yield levels determined. It was concluded that to obtain a narrow diameter distribution as well as maximum fiber fineness, a polymer concentration of 10 wt%, tip to collector distance of 18 cm and applied voltage of 20 kV variables were the optimum. Furthermore, it was also concluded that the ratio of Zrace (6 g) to PVA solution (10% wt) played an important role for achieving the minimum fiber diameter. Under these optimum conditions, the diameters of the electrospun composite fibers ranged from 86 nm to 381 nm with a diameter average of 193 nm. The experiments were done with Qualitek-4 software with “smaller is better” as the quality characteristics. The optimized conditions showed an improvement in the fibers diameter distribution and the average fibers diameter showed good resemblance with the result predicted using the Taguchi method and the Qualitek-4 software. The ANOVA results showed that all factors had significant effects on the fibers diameter and distribution, but the effect of PVA concentration and zirconium acetate were more significant than the other factors.     

Manufacture and Characterization of Poly (butylene terephthalate) Nanofibers by Electrospinning

Poly (butylene terephthalate) (PBT) nanofiber mats were prepared by electrospinning, being directly deposited in the form of a random fibers web. The effect of changing processing parameters such as solution concentration and electrospinning voltage on the morphology of the electrospun PBT nanofibers was investigated with scanning electron microscopy (SEM). The electrospun fibers diameter increased with rising concentration and decreased by increasing the electrospinning voltage, thermal and mechanical properties of electrospun fibers were characterized by DSC and tensile testing, respectively.     

The Controllable Surface Morphology of Polyimide (PI) Electrospun Fibers

Electrospun materials have been proposed for application for gas filtration, drug carriers, and tissue engineering. The surface morphology of electrospun fibers is the key for consideration for the above applications, such as pore size on the fiber surface, surface area, and roughness. In this work, we investigated the influence of polymer/solvent properties on soluble polyimide (PI) fibers. The studied PIs included three fluorinated aromatic polyimides containing naphthalene pendant groups. By using various solvents we adjusted the size, shape, and structure of the fibers. As a result, PI electrospun fibers could be achieved with width around 10 μm. The rough and smooth surface morphologies were studied by scanning electron microscopy (SEM). Surface wettability of the electrospun fiber membranes were characterized by contact angle measurement. The contact angles on the electrospun PI fiber mats for water and glycerol were in the range of 137.6°–144.5° and 139.1°–143.6°, respectively. Moreover, the rough fiber surface could make the electrospun fiber membrane possess good adhesive force for liquids. The results suggest that we could widen the application of electrospun membranes through controlling the fiber morphology.     

Optimization of Electrospun Polyacrylonitrile/Poly(Vinylidene Fluoride) Nanofiber Diameter Using the Response Surface Method

Electrospinning of polyacrylonitrile/poly(vinylidene fluoride) (PAN/PVdF) was applied using Box–Benkhen experimental design to obtain a quantitative relationship between selected electrospinning parameters (namely applied voltage, solution concentration, and PVdF composition) and nanofiber diameter and standard deviation of nanofiber diameter. Important parameters in the model were determined by analysis of variance (ANOVA). The model was consequently used to find the optimal conditions that yield the minimum PAN/PVdF nanofiber diameter. The morphology and nanofiber diameter were investigated by field emission scanning electron microscopy (FESM). The range of produced nanofiber diameters was from 116 to 379 nm. It was concluded that the nanofiber diameter tended to increase with solution concentration and decrease with PVdF composition. The applied voltage had no significant effect on the nanofiber diameters. Nanofibers with smaller standard deviation in diameter could be obtained at lower solution concentrations and higher PVdF composition. The model predicted the minimum nanofiber diameter of 114 nm when the applied voltage was set at 19.7 kV, solution concentration set at 14.07 wt%, and the PVdF composition set at 58.78 wt%.     

Electrospun cerium nitrate/polymer composite fibres: synthesis, characterization and fibre-division model

Cerium (Ⅲ) nitrate/poly(vinylpyrrolidone) (Ce(NO3)3/PVP) composite fibres have been prepared by electrospinning. After calcining the composite fibres in air at 500℃,CeO2 nanowires were obtained. The characterizations of the as-spun composite fibres and resultant nanowires have been carried out by a scanning electron microscope (SEM),an infrared spectrometer,an x-ray diffractometer and a fluorescence spectrophotometer. Interestingly,some unusual ribbon-like or twin fibres were observed besides the common fibres with circular or elliptic cross sections. We developed a fibre-division model resulting from Coulomb repulsion and solvent vaporization to interpret the formation of the ribbons or twin fibres,which has been confirmed by the SEM studies. Our results also indicate that the formation of the ribbons or twin fibres is less dependent on operation voltage and work distance.     

微环芯腔与锥形纳米光纤耦合过程的实验研究

在实验上研究了共振于铯原子跃迁线附近的微环芯腔与锥形纳米光纤的耦合特性。通过精密控制微环芯腔与锥形纳米光纤的相对位置,实现了两者的欠耦合、临界耦合和过耦合的精确控制。当微环芯腔与锥形纳米光纤间距为0.6μm时,系统达到临界耦合,透射率为0.3%±0.3%,耦合效率为99.7%±0.3%。由微环芯腔透射光谱得到微环芯腔的自由光谱区为1067±5GHz,等效腔长为223±1μm,线宽为2.9±0.1GHz,本征品质因数为(6.2±0.6)×10~4。随着微环芯腔与锥形纳米光纤间距的减小,微环芯腔的线宽逐渐增大,共振频率发生红移,频率移动为19.2±0.1GHz。该研究找到了有效控制微环芯腔与锥形纳米光纤耦合状态的方法,为下一步实现微环芯腔与原子间强耦合奠定了实验基础。同时该研究加深了人们对微环芯腔不同耦合状态的认识,为研究欠耦合和过耦合状态提供了实验基础。     

Investigation of Effect of Electrospinning Parameters on the Morphology of Polyacrylonitrile/Polymethylmethacrylate Nanofibers: A Box–Behnken-Based Study

Polyacrylonitrile (PAN)- and polymethylmethacrylate (PMMA)-blended nanofibers produced using electrospinning and mat morphology were studied. The response surface method was exploited to optimize the diameter and its standard deviation of electrospun PAN/PMMA non-woven membranes. The diameter and its standard deviation were related to the solution concentration, applied voltage, and PMMA composition. The morphology of nanofibers was studied by means of field emission scanning electron microscopy. The importance of parameters and their interactions was investigated through the analysis of variance. The nanofibers' diameter increased with solution concentration and decreased with applied voltage. The data showed that the diameter of nanofibers decreased up to 50% with PMMA composition, and then increased with further increase of PMMA composition. Some important interactions between the parameters were detected.     

酞菁镍复合凝胶材料的制备及谱学研究

采用Sol gel湿化学工艺将水溶性的四磺化酞菁镍 (NiTSPc)均匀掺入SiO2 凝胶基质。考察SiO2 凝胶基质在溶胶 凝胶的转化过程中组织结构和粘度变化的相关规律及最终所获干凝胶孔结构的特征。对NiT SPc在此过程中电子吸收光谱的变化进行了系统的跟踪研究以考察其在溶胶 凝胶体系中的二聚行为 ,并结合复合体系微化学环境的改变对其进行了自洽解释。     

斜入射时波片相位延迟和偏振像差的精确公式

在激光技术和偏光显微镜中常常在斜入射状态下使用波片，本文提出了一个波片相位延迟和偏振像差的精确公式。这一公式对于精确计算波片的调谐曲线和偏光显微镜的偏振像差十分重要。计算表明只要适当选择晶体的方位角，波片的相位延迟和偏振光的椭圆率随入射角的改变能减少到最小。