CeO2/TiO2复合纳米纤维的制备及光催化性能研究

采用静电纺丝技术和水热合成法制备了CeO₂/TiO₂复合纳米纤维. 利用X射线衍射(XRD)、拉曼光谱(Raman)、扫描电镜(SEM)、透射电镜(TEM)和比表面积测定(BET)等分析测试手段对样品的形貌及结构进行了表征, 并以罗丹明B的脱色降解为模式反应, 考察了样品的光催化性能. 结果表明: CeO₂纳米粒子均匀地生长在TiO₂纳米纤维表面, 形成了异质结构的CeO₂/TiO₂复合纳米纤维光催化材料. 通过改变碱源, 可以得到不同形貌的CeO₂. CeO₂的存在增加了TiO₂纳米纤维的比表面积, 有效地实现TiO₂光生电子和空穴的分离, 增强了体系的量子效率, 与纯TiO₂纳米纤维相比光催化活性明显提高. 初步探讨了异质结的形成机理.     

三维网状Dy3+:YVO4/TiO2复合纤维的制备及光催化产氢性能

以电纺TiO₂纳米纤维为基质, 柠檬酸为软模板, 采用一步水热法制备了具有三维立体网状结构的稀土Dy ³⁺掺杂YVO₄/TiO₂复合纤维. 通过X射线衍射、 扫描电子显微镜、 X射线光电子能谱、 N₂吸附-脱附、 紫外-可见漫反射光谱及荧光光谱等手段对材料的组成、 表面形貌和性能进行表征, 以光分解水产氢实验考察其光催化活性. 结果表明, Dy ³⁺∶YVO₄纳米枝与TiO₂纳米纤维相互交联构筑的纳米纤维网具有大比表面积, 可提供更多活性位点, 改善了多相光催化反应的传递过程; 稀土Dy ³⁺掺杂的YVO₄与TiO₂复合形成异质结相互促进, 在拓宽光谱响应范围、 提高太阳光利用率的同时使光生电子-空穴对得到较好分离, 从而提高了样品的光催化活性. 模拟太阳光照射下, Dy ³⁺∶YVO₄/TiO₂复合纤维光催化产氢速率达到8.63 mmol· h ^-1·g ^-1, 是纯TiO₂纳米纤维的10倍.     

Bi2Ti2O7/TiO2/Bi4Ti3O12多异质结的构筑及其增强的可见光催化性能

以静电纺丝技术制备的TiO₂纳米纤维为基质,硝酸铋为铋源,KOH为矿化剂,成功制备了多异质结Bi₂Ti₂O₇/TiO₂/Bi₄Ti₃O₁₂复合纳米纤维光催化剂。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis DRS)等一系列表征,对其物相组成、微观形貌和光学性质等进行分析。结果表明：TiO₂纳米纤维的介入,将Ⅰ型异质结Bi₂Ti₂O₇/Bi₄Ti₃O₁₂分离为2个Ⅱ型异质结Bi₂Ti₂O₇/TiO₂和Bi₄Ti₃O₁₂/TiO₂。Bi₂     

Pt/TiO2纳米纤维的制备及其对甲醇的电催化氧化活性

采用静电纺丝技术结合还原浸渍法制备了Pt/TiO₂纳米纤维电催化剂, 通过X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)和X射线能谱(EDS)等测试手段对样品的晶相、形貌、微结构和化学组成进行了表征. 测试结果表明, TiO₂纳米纤维为锐钛矿和金红石组成的混晶, Pt 纳米颗粒均匀地分布于TiO₂纳米纤维的表面, 且Pt 颗粒大小较均一, 平均粒径为4.0 nm, Pt/TiO₂纳米纤维中Pt 的质量分数约为20%. 采用三电极体系的循环伏安和计时电流电化学分析方法研究了样品在酸性溶液中对甲醇的电催化氧化活性, 结果表明, 与负载相同质量分数Pt 的Pt/P25 和商业Pt/C 催化剂相比较, Pt/TiO₂纳米纤维催化剂对甲醇呈现出较高的电催化氧化活性和更好的稳定性.     

3D ZnIn2S4微球/1D TiO2纳米带异质结构的光催化降解和还原性能

首先采用溶剂热法和高温煅烧法制备1D TiO₂纳米带,其次利用溶剂热法将1D TiO₂纳米带均匀地穿插到片层结构组装而成的3D ZnIn₂S₄微球中,所形成的异质结构能有效抑制光生电子-空穴的复合。二元ZnIn₂S₄微球/TiO₂纳米带复合光催化剂在高浓度染料罗丹明B(RhB)的光降解和Cr(VI)的光还原实验中表现出优异的性能。在模拟太阳光照射下,ZnIn₂S₄/TiO₂纳米带光催化降解RhB和还原Cr(VI)的效率相较于纯TiO₂颗粒(10%,22%)、TiO₂纳米带(45%,40%)、ZnIn₂S₄(62%,65%)、ZnIn₂S₄/TiO₂颗粒(90%,91%)分别提高至100%和100%。最后,通过紫外-可见...     

TiO2纳米微粒对PPV发光性能的影响

采用溶胶凝胶法制备了一系列PPV/TiO₂纳米复合膜,探讨了TiO₂纳米微粒对PPV发光性能的影响.研究发现,这些复合膜的发光性质依赖于TiO₂/PPV的质量比,.在TiO₂/PPV的质量比为1/9时,复合膜中的TiO₂微粒对PPV的荧光具有猝灭作用;当TiO₂/PPV的质量比为1/1时,复合膜中的TiO₂对PPV的荧光具有增强作用.通过FT-IR,UV-Vis,FL光谱和TEM探讨了复合膜微结构与其发光性质的关系.     

CdS超薄片层包覆TiO2中空结构复合材料的形成和应用

本实验以钛酸四丁酯为钛源,醋酸镉为镉源,利用静电纺丝的方法制备了直径~250 nm的电纺丝纳米纤维。通过高温煅烧和硫化钠溶液进行水热处理,得到CdS超薄片层包覆TiO₂中空结构的纳米纤维。推测该复合结构形貌的形成过程为:在Ti/Cd(摩尔比)为1:1和2:1时,由于CdO的含量较高,反应过程中CdO溶解,并与反应溶液中的S^2-形成CdS超薄片层生长在纤维的外表面,剩余的TiO₂纳米粒子聚集形成中空的纳米管状结构;而Ti/Cd(摩尔比)为4:1和8:1时,由于溶解的CdO较少不足以形成TiO₂纳米管,同时,生成的CdS也不足以完全包覆TiO₂纳米纤维形成非管状结构。当Ti/Cd为1:1时,TiO₂@CdS复合材料具有最好的产氢活性。在300 W氙灯光照条件下和加UVCUT-420 nm滤光片下,50 mg催化剂产氢速率分别为19.7 μmol/h和3.4 μmol/h,这主要是由于所得到的复合结构中TiO₂为非晶材料。进一步在惰性气氛下煅烧,也很难将TiO₂晶化。     

在一种新的溶剂体系中通过静电纺丝制备TiO2纳米纤维

以钛酸四丁酯为前驱体, 醋酸纤维素为模板纤维, 丙酮/N,N-二甲基乙酰胺为溶剂, 通过静电纺丝, 水解和450 ℃煅烧制备了直径约为80 nm的锐钛矿型TiO₂纳米纤维. 通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和N₂吸脱附法表征了TiO₂纳米纤维的形貌、直径大小、晶态、比表面积、孔结构及分布. 研究表明该纳米纤维由大小为9.2 nm的颗粒组成, 纤维内含有大量直径为1.7～21 nm的介孔. 它具有与直径为25 nm的商业化Degussa P25相似的高比表面积, 约为50 m²/g. 研究了TiO₂纳米纤维对有机小分子化合物罗丹明B (RhB)和苯酚的光催化降解. 结果表明: 以6 mg/L的RhB和10 mg/L的苯酚水溶液为母液, 以质量分数为0.05%的TiO₂纳米纤维膜为催化剂, 在500 W的紫外灯照射下, 2 h内约90%的RhB和75%的苯酚能被光催化降解.     

掺杂改性纳米TiO2降解挥发性污染物及产物研究

本文系统研究了水热法制备的铁掺杂纳米TiO₂和氮掺杂纳米TiO₂在可见光照射下对挥发性有机物(volatile organic compounds,VOCs)的降解能力和降解产物.铁掺杂纳米TiO₂和氮掺杂TiO₂对光的吸收边分别红移到540 nm和580 nm;在可见光下具有良好的催化活性,24 h内对挥发性有机物的降解率达20%—50%,降解后的最终产物可能主要为CO₂.     

Ag纳米粒子在TiO2四棱柱阵列上的可控生长及其SERS效应

采用水热法在导电玻璃FTO导电面上沉积TiO₂四棱柱阵列; 并以其为基体, 分别采用聚乙烯基吡咯 烷酮(PVP)还原Tollens试剂以及柠檬酸三钠(TSC)还原硝酸银溶液, 将Ag纳米粒子(AgNPs)沉积在TiO₂四棱柱阵列上形成TiO₂@AgNPs-PVP和TiO₂@AgNPs-TSC微纳结构作为表面增强拉曼散射(SERS)基底. 实验结果表明, Ag纳米粒子在TiO₂四棱柱阵列上的尺寸和分布可通过改变Tollens试剂的浓度和TSC还原硝酸银溶液的反应时间来调控, 进而优化基底的SERS灵敏度. TiO₂@AgNPs-PVP微纳结构对罗丹明6G(R6G)的检出限为10^-12 mol/L, 对低活性小分子三聚氰胺的检出限为0.01 mg/mL; TiO₂@AgNPs-TSC微纳结构对R6G的检出限为10^-10 mol/L, 对三聚氰胺的检出限为0.01 mg/mL. TiO₂@AgNPs-PVP和TiO₂@AgNPs-TSC微纳结构基底的SERS活性、 循环可回收性与还原剂种类紧密相关: 包覆在Ag纳米粒子上的PVP可以作为隔离层避免Ag纳米粒子直接接触, 防止电磁场耦合作用减弱, 增强基底的SERS活性; 同时, PVP是一种水性聚合物, 有较强的亲水性, 作为循环可回收SERS基底使用时, 吸附小分子物质清洗难度较大.     

Electrospun Nanofibers Modified with Phospholipid Moieties for Enzyme Immobilization

Summary: PANCMPCs containing phospholipid side moieties were electrospun into nanofibers with a mean diameter of 90 nm. Field emission SEM was used to characterize the morphologies of the nanofibers. These phospholipid‐modified nanofibers were explored as supports for enzyme immobilization due to the characteristics of excellent biocompatibility, high surface/volume ratio, and porosity, which were beneficial to the catalytic efficiency and activity of immobilized enzymes. Lipase from Candida rugosa was immobilized on these nanofibers by adsorption. Preliminary results indicated that the properties of the immobilized lipase on these phospholipid‐modified nanofibers were greatly promising.

Schematic representation of the structure and electrostatic properties of phospholipid‐modified nanofibers.     

An effective continuum approach for modeling non-equilibrium structural evolution of protein nanofiber networks

We quantify the formation and evolution of protein nanofibers using a new phase field modeling framework and compare the results to transmission electron microscopy measurements (TEM) and time-dependent growth measurements given in the literature. The modeling framework employs a set of effective continuum equations combined with underlying nanoscale forces and chemical potential relations governing protein nanofiber formation in solution. Calculations based on the theoretical framework are implemented numerically using a nonlinear finite element phase field modeling approach that couples homogenized protein molecular structure via a vector order parameter with chemical potential relations that describe interactions between the nanofibers and the surrounding solution. Homogenized, anisotropic molecular and chemical flux relations are found to be critical in obtaining nanofiber growth from seed particles or a random monomer bath. In addition, the model predicts both sigmoidal and first-order growth kinetics for protein nanofibers for unseeded and seeded models, respectively. These simulations include quantitative predictions on time scales of typical protein self-assembly behavior which qualitatively match TEM measurements of the RADA16-I protein and growth rate measurements for amyloid nanofibers from the literature. For comparisons with experiments, the numerical model performs multiple nanofiber protein evolution simulations with a characteristic length scale of ～2.4 nm and characteristic time scale of ～9.1 h. These results provide a new modeling tool that couples underlying monomer structure with self-assembling nanofiber behavior that is compatible with various external loadings and chemical environments.     

Chemistry on Electrospun Polymeric Nanofibers: Merely Routine Chemistry or a Real Challenge?

Nanofiber‐based non‐wovens can be prepared by electrospinning. The chemical modification of such nanofibers or chemistry using nanofibers opens a multitude of application areas and challenges. A wealth of chemistry has been elaborated in recent years on and with electrospun nanofibers. Known methods as well as new methods have been applied to modify the electrospun nanofibers and thereby generate new materials and new functionalities. This Review summarizes and sorts the chemistry that has been reported in conjunction with electrospun nanofibers. The major focus is on catalysis and nanofibers, enzymes and nanofibers, surface modification for biomedical and specialty applications, coatings of fibers, crosslinking, and bulk modifications. A critical focus is on the question: what could make chemistry on or with nanofibers different from bulk chemistry?

     

Dissolution and gelation of α-chitin nanofibers using a simple NaOH treatment at low temperatures

In this study, both α-chitin powders and nanofibers were successfully dissolved in 20 wt% NaOH solutions at low temperatures. Elemental analysis confirmed that this NaOH-freezing treatment did not cause deacetylation of chitin. After heating and neutralizing with water, chitin hydrogels could be prepared. X-ray diffraction and field emission scanning electron microscope data demonstrated that these two hydrogels formed typical regenerated microporous structures with low crystallinity, which was caused by the dissolution process. Based on this result, cold ethanol was used for α-chitin nanofibers during the initial stages of neutralization, which effectively prevented the dissolution and decrease in crystallinity and was even able to preserve the continuous network structure of original nanofiber. This gelation behavior seems to be attributed to interdigitation and aggregation between neighboring nanofibers in cold alkali solution leading to the shrinkage of the hydrogel. In general, by avoiding the dissolution process, highly crystalline hydrogel based on α-chitin nanofibers was prepared by a simple NaOH treatment without use of any other chemical solvents or cross-linking agents. We expect this new type of hydrogel could be promoted to wide applications and research studies as novel green nanomaterials.     

Structural characterization and electrical conductivity studies of BaMoO4 nanofibers prepared by sol–gel and electrospinning techniques

Scheelite type BaMoO₄ nanofibers were prepared by using acrylamide assisted sol–gel process and electrospinning technique. The prepared Scheelite BaMoO₄ nanofibers were characterized by using TG/DTA, XRD, FTIR, FT-Raman and SEM–EDX techniques. Thermal behavior, crystalline phase and structure of the prepared BaMoO₄ nanofibers samples were confirmed from the analysis of the obtained results of TG/DTA, XRD, FTIR and FT-Raman respectively. SEM micrographs along with EDX showed the formation of one dimensional (1D) nanofibers 100–350 nm diameters and existence of Ba, Mo and O elements in the BaMoO₄ nanofibers sample. The electrical conductivity of BaMoO₄ nanofibers as a function of temperature 200–400 °C under air was evaluated by analyzing the measured impedance data using the winfit software. The newly prepared Scheelite type BaMoO₄ nanofibers showed electrical conductivity of 0.92 × 10^?3 S/cm at 400 °C.     

Fabrication and characterization of polycrystalline WO3 nanofibers and their application for ammonia sensing

We describe the fabrication and characterization of tungsten oxide nanofibers using the electrospinning technique and sol-gel chemistry. Tungsten isopropoxide sol-gel precursor was incorporated into poly(vinyl acetate)(PVAc)/DMF solutions and electrospun to form composite nanofibers. The as-spun composite nanofibers were subsequently calcinated to obtain pure tungsten oxide nanofibers with controllable diameters of around 100 nm. SEM and TEM were utilized to investigate the structure and morphology of tungsten oxide nanofibers before and after calcination. The relationship between solution concentration and ceramic nanofiber morphology has been studied. A synchrotron-based in situ XRD method was employed to study the dynamic structure evolution of the tungsten oxide nanofibers during the calcination process. It has been shown that the as-prepared tungsten oxide ceramic nanofibers have a quick response to ammonia with various concentrations, suggesting potential applications of the electrospun tungsten oxide nanofibers as a sensor material for gas detection.     

一步法溶剂热催化合成纳米碳纤维

利用四氢呋喃为溶剂和碳源,通过溶剂热催化方法在500 ℃一步合成了纳米碳纤维,X-射线衍射（XRD）分析显示此法合成的碳纤维晶型为碳的六方石墨相,场发射电镜(FESEM)和透射电镜(TEM)照片进一步表明碳纤维平均直径为100 nm,长度达几百纳米至几微米,高分辨电镜照片揭示产品中碳的晶间距为0.34 nm;产品纯度通过热重法（TGA）分析;同时,拉曼光谱图显示在1 347和1 584 cm^-1处有2个强峰,这与石墨相碳的典型拉曼光谱图是一致的。     

Spectroscopic investigations on polypropylene‐carbon nanofiber composites. I. Raman and electron spin resonance spectroscopy

Isotactic polypropylene‐vapor grown carbon nanofiber composites containing various fractions of carbon nanofibers, ranging from 0 to 20 wt %, have been prepared. Raman spectroscopy was used to analyze the effect of the dispersion of carbon nanofibers within polypropylene and the interactions between carbon nanofibers and macromolecular chains. The as‐recorded Raman spectra have been successfully fitted by a linear convolution of Lorentzian lines. Changes of the Raman lines parameters (position, intensity, width, and area) of polypropylene and carbon nanofibers were analyzed in detail. The Raman spectra of the polymeric matrix—at low concentrations of nanofibers—show important modifications that indicate strong interactions between carbon nanofibers and the polymeric matrix reflecting by vibrational dephasing of macromolecular chains. The Raman spectrum of carbon nanofibers is sensitive to the loading with carbon nanofibers, showing changes of the resonance frequencies, amplitudes, and width for both D‐ and G‐bands. Raman data reveals the increase of the disorder, as the concentration of carbon nanofibers is increased. The presence of the typical ESR line assigned to conducting electrons delocalized over carbon nanofibers is confirmed and the presence of a spurious magnetic line due to catalyst's residues is reported. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1644–1652, 2009     

Angiotensin II-induced aortic ring constriction is mediated by phosphatidylinositol 3-kinase/L-type calcium channel signaling pathway

Angiotensin II (AngII) is a crucial hormone that affects vasoconstriction and exerts hypertrophic effects on vascular smooth muscle cells. Here, we showed that phosphatidylinositol 3-kinase-dependent calcium mobilization plays pivotal roles in AngII-induced vascular constriction. Stimulation of rat aortic vascular smooth muscle cell (RASMC)-embedded collagen gel with AngII rapidly induced contraction. AngII-induced collagen gel contraction was blocked by pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor ({"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002) whereas ERK inhibitor (PD98059) was not effective. AngII-induced collagen gel contraction was significantly blocked by extracellular calcium depletion by EGTA or by nifedipine which is an L-type calcium channel blocker. In addition, AngII-induced calcium mobilization was also blocked by nifedipine and EGTA, whereas intracellular calcium store-depletion by thapsigargin was not effective. Finally, pretreatment of rat aortic ring with {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 and nifedipine significantly reduced AngII-induced constriction. Given these results, we suggest that PI3K-dependent activation of L-type calcium channels might be involved in AngII-induced vascular constriction.     

Pluronic‐Induced Surface Etching of Biodegradable Nanofibers for Enhanced Adsorption of Serum Protein

Manipulated roughness has been etched on nanofibers to modulate adsorption of serum proteins for serum‐free cells cultivation. Mixtures of Polycaprolactone and Pluronic with various blending ratios are electrospun to nanofibers and Pluronic is subsequently leached out by methanol. Electron microscopy reveals that surface roughness of the nanofibers is changed according to the contents of Pluronic. Both weight loss monitoring and NMR spectroscopy confirm that all Pluronic is leached out after methanol treatment. Water swelling ratio and protein adsorption of rougher nanofibers are higher than those of smoother ones. Also, when serum incorporation on the nanofibers is estimated in 0.01–10% serum solution, rougher nanofibers show higher serum incorporation and those soaked in 10% serum solution are employed for serum‐free cell cultivation. Viability of the cells cultivated on rougher nanofibers is much higher after 24 h. Thus, Pluronic‐induced leaching‐out strategy can be potentially employed for fabricating roughness on nanofibers for enhancing protein adsorption for serum‐free cell cultivation.