Carbon Nanofibers Prepared via Electrospinning

Carbon nanofibers prepared via electrospinning and following carbonization are summarized by focusing on the structure and properties in relation to their applications, after a brief review of electrospinning of some polymers. Carbon precursors, pore structure control, improvement in electrical conductivity,and metal loading into carbon nanofibers via electrospinning are discussed from the viewpoint of structure and texture control of carbon.     

基于电纺技术构筑多孔SnO2纳米纤维膜的研究

以聚乙烯吡咯烷酮(PVP)作为纺丝助剂,五水合四氯化锡(SnCl4·5H2O)作为前驱体,采用静电纺丝技术结合高温煅烧法成功制备了直径为(363±28)nm的多孔氧化锡纳米纤维膜.使用SEM表征了纤维膜的微观形貌和尺寸,利用X射线衍射仪(XRD)研究了焙烧温度对晶粒尺寸的影响,利用傅里叶变换红外光谱仪(FTIR)、热重和差热同步仪(TGA-DTA)及拉曼光谱仪(Raman)等研究了纤维膜的分子结构变化、热稳定性和物相结构.研究结果表明,固定两喷丝头间距15.0 cm、流速0.5 mL/h、电场强度1.1～1.4 kV/cm时,可以电纺出表面光滑、直径均一的纳米纤维膜;经900℃焙烧制备得到晶粒尺寸约12.27 nm的四方相金红石型晶体结构的氧化锡纤维膜.     

Layered Perovskite Nanofibers via Electrospinning for Overall Water Splitting

The (111)‐layered perovskite materials Ba₅Ta₄O₁₅, Ba₅Ta₂Nb₂O₁₅ and Ba₅Nb₄O₁₅ are prepared with nanofiber morphology via electrospinning for the first time. The nanofibers are built up from small single crystals, with up to several micrometers length even after calcination. The formation mechanism is investigated in detail, revealing an intermediate formation of amorphous barium carbonate strengthening the nanofiber morphology for high temperature treatment. All nanofiber compounds are able to generate hydrogen without any co‐catalyst in photocatalytic reformation of methanol. After photodeposition of Rh‐Cr₂O₃ co‐catalysts, the nanofibers show better activity in overall water splitting compared to sol–gel‐derived powders.     

Block‐Copolymer Vesicles as Nanoreactors for Enzymatic Reactions

The impact of the spatial confinement of polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA) block copolymer (BCP) vesicles on the reactivity of encapsulated bovine pancreas trypsin is studied. Enzymes, as well as small molecules, are encapsulated with loading efficiencies up to 30% in BCP vesicles with variable internal volumes between 0.014 aL (internal vesicle diameter, d_in = 30 nm) and 8 aL (d_in = 250 nm), obtained by manipulating the vesicle preparation conditions. The kinetics of the trypsin‐catalyzed reaction of a fluorogenic substrate inside and outside the vesicles is quantitatively estimated using fluorescence spectroscopic analyses in conjunction with the use of NaNO₂ as selective quencher for non‐encapsulated fluorophores. The values of the catalytic turnover number obtained for reactions in differently sized nanoscale reactors show a significant increase (up to ≈5×) with decreasing BCP vesicle volume, while the values of the Michaelis–Menten constant decrease. The observed increase in enzyme efficiency by two orders of magnitude compared to bulk solution is attributed to an enhanced rate of enzyme–substrate and molecule–wall collisions inside the nanosized reactors, as predicted in the literature on the basis of Monte Carlo simulations.     

Mesoporous Block‐Copolymer Nanospheres Prepared by Selective Swelling

Block‐copolymer (BCP) nanospheres with hierarchical inner structure are of great interest and importance due to their possible applications in nanotechnology and biomedical engineering. Mesoporous BCP nanospheres with multilayered inner channels are considered as potential drug‐delivery systems and templates for multifunctional nanomaterials. Selective swelling is a facile pore‐making strategy for BCP materials. Herein, the selective swelling‐induced reconstruction of BCP nanospheres is reported. Two poly(styrene‐block‐2‐vinylpyridine) (PS‐b‐P2VP) samples with different compositions (PS₂₃₆₀₀‐b‐P2VP₁₀₄₀₀ and PS₂₇₇₀₀‐b‐P2VP₄₃₀₀) are used as model systems. The swelling reconstruction of PS‐b‐P2VP in ethanol, 1‐pyrenebutyric acid (PBA)/ethanol, or HCl/ethanol (pH = 2.61) is characterized by scanning electron microscopy and transmission electron microscopy. It is observed that the length of the swellable block in BCP is a critical factor in determining the behavior and nanostructures of mesoporous BCP nanospheres in selective swelling. Moreover, it is demonstrated that the addition of PBA modifies the swelling structure of PS₂₃₆₀₀‐b‐P2VP₁₀₄₀₀ through the interaction between PBA and P2VP blocks, which results in BCP nanospheres with patterned pores of controllable size. The patterned pores can be reversibly closed by annealing the mesoporous BCP nanospheres in different selective solvents. The controllable and reversible open/closed reconstruction of BCP nanospheres can be used to enclose functional nanoparticles or drugs inside the nanospheres. These mesoporous BCP nanospheres are further decorated with gold nanoparticles by UV photoreduction. The enlarged decoration area in mesoporous BCP nanospheres will enhance their activity and sensitivity as a catalyst and electrochemical sensor.     

电纺丝制备纳米纤维的研究进展

文中扼要回顾近年来电纺丝技术研究进展,包括:电纺丝工作原理和部分关键设备;控制尺寸、结构、取向及复合材料制备等;探讨连续化生产和组装纳米纤维;典型应用领域及电纺丝技术展望。     

木质素磺酸盐-丙烯腈共聚物及其碳纳米纤维的制备

通过酯化反应和自由基共聚反应制得木质素磺酸盐-丙烯腈共聚物(P(LS-AN)),采用静电纺丝技术将其制成纳米纤维,再经预氧化和碳化处理,制得碳纳米纤维。采用红外光谱仪(FTIR)、差示扫描量热/热重同步分析仪(DSC/TG)、扫描电子显微镜(SEM)和拉曼光谱仪(Raman)对P(LS-AN)、电纺纤维及其碳纳米纤维的结构进行表征。结果表明,P(LS-AN)纳米纤维具有良好的热稳定性,在较高升温速率(10℃/min)下对其进行预氧化和碳化处理,所制得的碳纳米纤维单丝间未产生粘连。在碳化过程中,LS的苯酚结构有利于促进有序碳结构的形成,使得碳纳米纤维的结构更为完善。     

复合纳米纤维静电纺丝法的制备及其磁性

以聚乙烯吡咯烷酮（PVP）和金属盐为原料,利用静电纺丝法成功制备出了摩尔比为1：1的SrTiO3-SrFe12O19磁电复合纳米纤维。并通过FT-IR,XRD,SEM和VSM等技术对纤维前驱体及其产物的结构、热处理产物的物相、形貌及磁性能进行了表征。结果表明,样品经900℃焙烧2h后,即可得到纯的SrTiO3和SrFe...     

Influence of Chain Architecture on Nanopore Accessibility in Polyelectrolyte Block‐Co‐Oligomer Functionalized Mesopores

Functionalized ordered mesoporous silica materials are commonly investigated for applications such as drug release, sensing, and separation processes. Although, various homopolymer functionalized responsive mesopores are reported, little focus has been put on copolymers in mesopores. Mesoporous silica films are functionalized with responsive and orthogonally charged block‐co‐oligomers. Responsive 2‐dimethylamino)ethyl methacrylate)‐block‐2‐(methacryloyloxy)ethyl phosphate (DMAEMA‐b‐MEP) block‐co‐oligomers are introduced into mesoporous films using controlled photoiniferter initiated polymerization. This approach allows a very flexible charge composition design. The obtained block‐co‐oligomer functionalized mesopores show a complex gating behavior indicating a strong interplay between the different blocks emphasizing the strong influence of charge distribution inside mesopores on ionic pore accessibility. For example, in contrast to mesopores functionalized with zwitterionic polymers, DMAEMA‐b‐MEP block‐co‐oligomer functionalized mesopores, containing two oppositely charged blocks, do not show bipolar ion exclusion, demonstrating the influence of the chain architecture on mesopore accessibility. Furthermore, ligand binding–based selective gating is strongly influenced by this chain architecture as demonstrated by an expansion of pore accessibility states for block‐co‐oligomer functionalized mesopores as compared to the individual polyelectrolyte functionalization for calcium induced gating.