SiO_2溶胶直接静电纺产物的微观形貌和形成机理

以正硅酸乙酯(TEOS)为原料,采用溶胶凝胶和静电纺联合技术获得了SiO2凝胶纤维膜。研究了SiO2溶胶直接静电纺产物微观形貌与其粘度的相互关系。FESEM观察结果表明,当陈化时间适当时(47 h),SiO2溶胶的粘度为200～350 mPa.s,具有较好的静电纺能力,可获得纤维直径为2.5μm左右的尺寸均匀和无节珠的凝胶纤维膜。     

高速离心纺制备纳米纤维原理研究

提出了一种区别于静电纺丝的新型制备纳米纤维方法的高速离心纺,它具有无高压、产量高、机构简单等优点,目前处于研究起步阶段.采用尼龙6(Nylon 6)溶液,研究高速离心纺制备纳米纤维时工艺参数、转子几何参数与转子转速等因素影响纳米纤维的直径、形貌的作用规律.研究成果能够更好指导高速离心纺制备有序纳米纤维理论研究,随着高速离心纺制备纳米纤维技术研究成熟,它在商业中的应用将逐渐实用化、普及化.     

溶剂挥发对静电纺丝纳米纤维支架直径与沉积的影响

为实现静电纺丝纳米纤维生物支架的可控制备,实验研究了不同溶剂挥发速度对聚己酸内酯(Polycaprolactone,PCL)纳米纤维直径和纤维沉积面积的影响。首先,使用挥发速度不同的溶剂分别配制相同浓度的PCL纺丝溶液,在外加电压为15kV,纤维接收距离为12cm的条件下进行静电纺丝;然后,利用钨灯丝扫描电镜测量所制备的纳米纤维直径和沉积面积,并使用最小二乘法拟合计算实验数据,推导出溶剂挥发速度与纤维直径和纤维沉积面积的比例关系。结果表明,随着溶剂挥发速度的增加,纳米纤维的平均直径从98nm(标准偏差为21.14nm)上升到205nm(标准偏差为38.83nm),溶剂挥发速度与纤维直径的比例关系为:d∝N0.25i;纤维的沉积面积从143cm2下降到35cm2,溶剂挥发速度与纤维沉积面积的比例关系为:S∝N-0.18i。实验结果和建立的比例关系式能够为纳米纤维生物支架的可控制备提供可靠的数据基础和理论指导。     

马赫-曾德尔干涉集成化的全光纤磁场与温度传感器

为了简化光纤磁场与温度传感器的结构并提高传感器灵敏度,设计并制作了马赫-曾德尔干涉集成化的全光纤磁场与温度传感器。将单根光纤的马赫-曾德尔模间干涉结构和双臂马赫-曾德尔干涉结构结合:将总长度为1.2m的单模光纤部分制备成长度为2.7cm、锥腰直径为30.1μm的锥形微纳光纤,并得到了拉锥时间与锥腰直径的关系。将锥形微纳光纤放置尼龙槽内并包覆磁凝胶构成传感头,实现模间干涉的马赫-曾德尔磁场传感器;将磁场传感器通过两耦合比为50%∶50%的耦合器并联带有可调谐光衰减器的单模光纤形成马赫-曾德尔干涉的温度传感器。从理论上分析了光谱漂移对磁场和温度传感的特性关系,实验测得室温下磁场强度在25~50mT时,磁场传感的灵敏度为0.301 14nm/mT;在磁场强度为0,温度由25℃升高到30℃时,温度传感的灵敏度为0.518 86nm/℃。该传感器可广泛应用于电力系统放电检测、材料加工、安全监控等领域。     

基于内壁芯光纤的调制器件

提出一种基于中空内壁悬挂芯光纤构造而成的光纤集成调制器.该光纤具有孔道结构,纤芯悬挂于孔道内壁.合成了含有超顺磁性Fe3O4纳米颗粒的磁流体,通过将空心光纤与多模光纤熔融连接,将磁流体封装在空心光纤内部,作为悬挂纤芯的包层.磁流体通过倏逝场对光产生吸收作用,由外磁场控制吸收强度,实现对纤芯的光调制.波长为632.8 nm的光经过拉锥耦合点耦合进入、传出调制元件.实验结果表明,在不同磁场强度下,仅仅2.0×10-3 μL的磁流体就可以对系统光衰减产生明显影响.当磁场强度为38 914 A/m时,饱和调制深度为43％;系统的响应时间低于120ms.该系统还可用于光开关,光纤滤波器和磁传感器等.     

丙酮对碳纳米管薄膜微纳光纤传输光的能量分布影响

基于薄膜微纳光纤中传播光能量分布的理论,在实验研究基础上,进一步用模场分析仪观察微纳光纤在表面镀有碳纳米管薄膜包层后,与丙酮气体接触时,其传输光的能量分布规律和倏逝场的变化。实验可知,在一定浓度的丙酮环境下,没有碳纳米管薄膜包层时,微纳光纤中传输光能量呈对称分布,当有碳纳米管薄膜包层时,其能量分布不再对称,并且能量分布的直径宽度增加。     

SiO2气凝胶常压合成新工艺

以正硅酸乙酯为硅源,HF为催化剂,采用溶胶-凝胶法常压下制备出了SiO2气凝胶,并研究了水、催化剂、乙醇等制备因素对其溶胶-凝胶过程的影响.用透射电镜(TEM)、比表面(BET)、傅里叶变换红外光谱仪、激光粒度仪等方法对其微结构测试.结果表明所制备的SiO2气凝胶具有大的比表面和纳米多孔结构(骨架颗粒约为10 nm,空洞尺寸为10～30 nm),平均粒径＜20 μm,为介孔结构.     

熔体静电纺丝法制备mLLDPE纤维的研究

茂金属催化剂聚合得到的线性低密度聚（mI。LI）PE）纤维是近年来发展非常迅速的一种塑料品种,正在逐渐地取代传统聚乙烯产品。本文研究了熔体静电纺丝法制备线性低密度聚乙烯纤维,通过添加剂改性,首次成功制备了直径为10～80μm的mLLDPE纤维。对不同纺丝参数,包括纺丝电压、接收距离、纺丝温度及添加剂用量对mLLDPE纤维直径与形貌的影响进行了研究,得到熔体静电纺mLL-DPE的最佳条件为纺丝电压25kV、接收距离2cm、纺丝温度160℃、聚乙烯蜡添加量30％。对mLLDPE纤维的结晶性能与纺丝温度及聚乙烯添加量之间的关系也进行了探讨。     

基于荧光猝灭的锥尖型光纤氧传感探头

利用动态化学腐蚀法制备锥尖型光纤端面,以提拉法镀溶胶凝胶敏感膜,组装了基于荧光猝灭的直径仅1.5 mm的光纤氧传感探头。探头锥面的长径比可通过调控腐蚀参数(温度、腐蚀液面下降速度)调控。构建相移测量系统,优化参数后进行0~21%范围内的氧含量测定,工作曲线呈现良好的线性特征(R2=0.999 6),偏差小于测量值的5%。     

基于韦森堡效应的旋转多针头式静电纺丝

文中研究了用静电纺丝法批量制备纳米纤维的方法.基于韦森堡效应的原理,圆盘的旋转使溶液沿转轴爬升,从而为静电纺丝连续供液,由此设计了一种装置.纺丝头是由固定在圆盘上的针尖阵列组成的.圆盘的旋转使针尖蘸取爬升的溶液,在针尖和收集板间高电压的作用下制备出直径较小(200~800 nm)、比较均一的整齐的纤维.随着针数量和圆盘转速的增加,纤维的产率呈增加的趋势,产率可达3.3 g/h.纤维直径随着溶液浓度的增加而增加,但会随着圆盘转速以及电极至收集板之间的距离的增加而减小.     

基于表面开孔光纤的集成式亚硝酸盐微流荧光传感器

利用中空悬挂芯光纤研制了一种将荧光猝灭反应区建立在空心光纤内部的光纤集成荧光在线微流传感器。利用CO2激光器在光纤表面刻蚀微孔,使得试剂可由微孔注入光纤内部并混合形成稳定的微流。在悬挂芯光纤纤芯倏逝场的激发下,指示剂分子产生荧光,所产生的荧光被耦合到纤芯内部并在出射端被检测。文中利用光纤内部的荧光猝灭反应实验确定了亚硝酸盐溶液的浓度。结果显示:微流可在短时间通过光纤,传感器能以较快的速度检测溶液浓度。另外,当亚硝酸盐溶液的浓度为0.1~2.6mmol/L时,荧光猝灭程度与溶液浓度呈较好的线性关系,结果证明了该集成式光纤内微流控传感器方案用于微量荧光检测的可行性。     

Efficient white organic light-emitting diodes with mixed electron transporting layers

The authors demonstrated phosphorescent white organic light-emitting diodes (PHWOLED) with mixed electron transporting layers (M-ETL) using 4,7-diphenyl-1,10-phenanthroline (BPhen)/4,4′-bis (carbazol-9-yl)biphenyl (CBP). The M-ETL PHWOLED exhibited the optimum balance of holes and electrons, owing to the low electron mobility of the CBP M-ETL. The optimized PHWOLED showed a peak current efficiency of 16.85 cd/A and a peak external quantum efficiency of 7.32%.     

桑色素-Al掺杂的溶胶-凝胶薄膜修饰的MPOF光纤氟离子传感探头

本文通过对微结构聚合物光纤修饰桑色素-铝配合物掺杂的凝胶薄膜,制备了一种氟化物光纤传感探头。这种探头的结构基于微结构聚合物光纤实现,其内部具有贯穿的微孔道结构,这种微孔结构可以作为敏感材料的载体以及微传感池。敏感层的修饰通过溶胶-凝胶过程实现,将掺有桑色素-铝的溶胶直接吸入光纤内部,可以在光纤微孔阵列中形成凝胶敏感膜。微结构光纤内部可以容纳微量液体,传感过程在微孔道内进行。传感原理基于荧光淬灭远离实现,氟离子对凝胶膜中桑色素-铝具有强烈的荧光淬灭作用,因此传感探头对于不同浓度的氟离子溶液表现不同的荧光强度。在pH值为4.6的条件下,探头对于氟离子具有良好的响应,其传感范围为5-50mmol/L。     

Fabrication of near-field optical apertures in aluminium by a highly selective corrosion process in the evanescent field

A simple, one‐step process to fabricate high‐quality apertures for scanning near‐field optical microscope probes based on aluminium‐coated silicon nitride cantilevers is presented. A thin evanescent optical field at a glass–water interface was used to heat the aluminium at the tip apex due to light absorption. The heat induced a breakdown of the passivating oxide layer and local corrosion of the metal, which selectively exposed the front‐most part of the probe tip from the aluminium. Apertures with a protruding silicon nitride tip up to 72 nm in height were fabricated. The height of the protrusion was controlled by the extent of the evanescent field, whereas the diameter depended on the geometry of the probe substrate. The corrosion process proved to be self‐terminating, yielding highly reproducible tip heights. Near‐field optical resolution in a transmission mode of 85 nm was demonstrated.     

电纺直写纳米纤维在图案化基底的定位沉积

为进一步提高单根电纺丝纳米纤维的定位沉积和形貌控制水平,基于近场静电纺丝技术,研究了单根直写纳米纤维在无图案硅基底的沉积行为;仿真分析了图案化硅基底上方的空间电场分布;采用图案化硅基底作为收集板,实验考察了微图案形状、收集运动速度等因素对单根纳米纤维定位沉积的影响规律。实验结果显示,电纺直写技术具有良好的定位精度,可将直径为100～800 nm的纳米纤维精确定位于直径仅为1.6μm的圆形微图案阵列上表面;收集板运动速度较小时,受电场力影响纳米纤维沉积轨迹将朝微图案偏移7μm;收集板运动速度进一步减小时,纳米纤维在基底微图案附近或上表面产生聚集;长条形微图案对纳米纤维沉积过程具有良好的引导与约束作用。得到的结果表明,基于近场静电纺丝的直写技术可较好地实现单根纳米纤维在图案化硅基底的精确定位沉积。     

基于液晶5CB的静电纺丝光控形变器件

光控形变器件以其高响应速度在仿生学领域得到广泛关注。通过静电纺丝的方式,成功制备出了一种在可见光波段可实现形变响应并恢复的器件。通过在聚氨酯(TPU)弹性基底膜上静电纺丝有序排列的液晶小分子4-氰基-4'-戊基联苯(5CB)的聚乙烯醇(PVA)纤维膜,可以使其中的5CB在吸热后发生相转变并产生体积收缩,最终带动基底膜实现弯曲形变。通过静电纺丝或涂覆的方式添加光热转换率高的碳纳米管(CNTs),可以进一步赋予该类器件光控响应能力。结果表明,制备的器件因其良好的光控形变性能和光控响应性能,故可作为执行器用于人体仿生学等领域。     

A ‘pocket guide’ to total internal reflection fluorescence

The phenomenon of total internal reflection fluorescence (TIRF) was placed in the context of optical microscopy by Daniel Axelrod over three decades ago. TIRF microscopy exploits the properties of an evanescent electromagnetic field to optically section sample regions in the close vicinity of the substrate where the field is induced. The first applications in cell biology targeted investigation of phenomena at the basolateral plasma membrane. The most notable application of TIRF is single‐molecule experiments, which can provide information on fluctuation distributions and rare events, yielding novel insights on the mechanisms governing the molecular interactions that underpin many fundamental processes within the cell. This short review intends to provide a ‘one stop shop’ explanation of the electromagnetic theory behind the remarkable properties of the evanescent field, guide the reader through the principles behind building or choosing your own TIRF system and consider how the most popular applications of the method exploit the evanescent field properties.     

Evanescent field excitation and measurement of dye fluorescence in a metallic probe near-field scanning optical microscope

We introduce a method of dye fluorescence excitation and measurement that utilizes a near-field scanning optical microscope (NSOM). This NSOM uses an apertureless metallic probe, and an optical system that contains a high numerical aperture (NA) objective lens (NA= 1.4). When the area which satisfies NA < 1 is masked, the objective lens allows for the rejection of possible transmitted light (NA < 1) through the sample. In such conditions, the focused spot consists of only the evanescent field. We found that this NSOM system strongly reduces the background of the dye fluorescence and allows for the measurement of the fluorescence intensity below the diffraction limit of the excitation source.     

Evanescent field excitation and measurement of dye fluorescence in a metallic probe near-field scanning optical microscope

We introduce a method of dye fluorescence excitation and measurement that utilizes a near-field scanning optical microscope (NSOM). This NSOM uses an apertureless metallic probe, and an optical system that contains a high numerical aperture (NA) objective lens (NA = 1.4). When the area which satisfies NA < 1 is masked, the objective lens allows for the rejection of possible transmitted light (NA < 1) through the sample. In such conditions, the focused spot consists of only the evanescent field. We found that this NSOM system strongly reduces the background of the dye fluorescence and allows for the measurement of the fluorescence intensity below the diffraction limit of the excitation source.     

Application of photon scanning tunneling microscope to measure optical near field for atom manipulation

Photon scanning tunneling microscope has been employed to measure the three-dimensional evanescent optical field of an atom funnel. A 3.8 neV repulsive optical potential has been estimated by a 300 microm long probe with a tip radius of curvature of 21 nm. We have estimated limiting conditions for cold Rb atoms to reflect from the atom funnel. A two-dimensional doughnut-shaped optical near field has also been investigated. An aperture fiber probe is used to profile a focussed TEM(01) beam at the minimum beam waist and measure a dark center of about 10 microm while it is focussed by a converging lens of focal length 8 cm.