Functionalization of electrospun TiO2 nanofibers with Pt nanoparticles and nanowires for catalytic applications

This paper reports a simple procedure for derivatizing the surface of anatase TiO2 nanofibers with Pt nanoparticles and then Pt nanowires. The nanofibers were prepared in the form of a nonwoven mat by electrospinning with a solution containing both poly(vinyl pyrrolidone) and titanium tetraisopropoxide, followed by calcination in air at 510 degrees C. The fiber mat was then immersed in a polyol reduction bath to coat the surface of anatase fibers with Pt nanoparticles of 2-5 nm in size with controllable density of coverage. Furthermore, the coated fibers could serve as a three-dimensional scaffold upon which Pt nanowires of roughly 7 nm in diameter could be grown at a high density and with a length up to 125 nm. The fiber membranes functionalized with Pt nanoparticles and nanowires are interesting for a number of catalytic applications. It was found to show excellent catalytic activity for the hydrogenation of azo bonds in methyl red, which could be operated in a continuous mode by passing the dye solution through the membrane at a flow rate of 0.5 mL/s.     

Photocatalytic degradation of Rhodamine B using electrospun TiO2 and ZnO nanofibers: a comparative study

TiO₂ and ZnO nanofibers were fabricated through a facile electrospinning method. The obtained nanofibers were characterized by a variety of analytical means including FESEM, TEM, SAED, XRD, UV–Vis, and PL. Compared with nanoparticles, nanofibers can be recycled more easily when they are used as photocatalysts. The photocatalytic activities of these two nanofibers were investigated and compared by evaluating the photodegradation of hazardous dye Rhodamine B. Although, ZnO nanofibrous photocatalyst exhibits better initial activity than TiO₂ nanofibrous counterpart, its photocatalytic performance is inferior to that of the latter on the whole. The photo-instability arising from photocorrosion may be responsible for its rapid deterioration in activity. The difference in the photocatalytic properties between TiO₂ and ZnO nanofibers was discussed, and a possible photodegradation mechanism of organic dyes in the presence of the nanofibrous photocatalyst was proposed. This work offers a direct insight into the comparison of photocatalysis of electrospun TiO₂ and ZnO nanofibers.     

Preparation and characterization of electrospun SiO2 nanofibers

The objective of this study was to prepare and characterize electrospun SiO2 nanofibers for composite (particularly dental composite) applications. We investigated (1) tetraethyl orthosilicate (TEOS) as the alkoxide precursor, (2) polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP) as the carrying polymers, (3) several solvents for making the spin dopes, and (4) the morphological and structural properties of the electrospun SiO2 nanofibers and their relationship with the pyrolysis temperatures. We also investigated the morphology durability of the prepared SiO2 nanofibers by subjecting them to vigorous ultrasonic vibrations. The results indicated that the uniform (beads-free) amorphous SiO2 nanofibers with an average diameter of approximately 500 nm were successfully prepared. These SiO2 nanofibers also retained their overall fiber morphology when subjected to vigorous ultrasonic vibrations. The electrospun SiO2 nanofibers were, therefore, nano-scaled glass (amorphous SiO2) fibers, and could be used for reinforcement of dental composites.     

Preparation and characterization of electrospun nanofibers based on silk sericin powders

The present contribution reports the fabrication and characterization of silk sericin (SS) nanofibers via electrospinning. The function of solution concentration on morphological appearance and average diameter of the electrospun SS membranes was investigated by scanning electron microscopy. The structure and physical properties were observed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). All beads were acquired in lower concentration of SS solution, 1.3–8.5 wt% of SS solutions, and beaded fibers were produced from 9.6, 11.7, 14.2, and 16.5 wt% of SS solution. The perfect nanofibers acquiring average diameters of 145 and 184 nm were fabricated from 20.9 to 22.9 wt% of SS solution, respectively. Results from FT-IR showed that in the as-spun fibers, SS was present in a random coil conformation, while after heat treatment, the molecular structure of SS was transformed into a β-sheet containing structure. DSC and TG analysis illustrated that trifluoroacetic acid can be eliminated by heating. The availability of SS nanofibers introduces a new set of possible uses of these amazing fibers at a scale not explored before. New uses include small diameter fibers for cell proliferation purposes, nanocomposite reinforcing fibers for nanotechnology, wound dressing, scaffolds for tissue engineering, and other biomedical applications.     

静电纺淀粉纳米纤维的交联改性研究

通过静电纺丝技术制备纯淀粉纳米纤维膜,并在密闭容器中和戊二醛蒸汽进行交联。利用环境扫描电子显微镜(ESEM)、傅里叶变换红外光谱(FT-IR)对纤维交联前后的表面形貌和结构进行观察和分析,通过电子万能材料拉伸试验机、接触角测试仪等考察了交联反应对纤维膜性能的影响。结果表明,戊二醛与淀粉分子之间发生了缩醛化交联反应,淀粉纳米纤维膜经戊二醛蒸汽交联后仍能较好的保留原纤维的形态,并且拉伸性能和耐水性能均得到一定程度的提高。     

Electrical properties of electrospun carbon nanofibers

Electrospun carbon nanofibers (ECNs) were prepared through stabilization and carbonization of electrospun polyacrylonitrile nanofibers as the precursor, and their morphological, structural, and electrical properties were evaluated. Temperature dependencies of resistivity of ECNs carbonized at several temperatures were investigated. The character of the temperature dependencies of resistivity was typical for semiconducting materials. The values of corresponding activation energies were obtained for ECN samples carbonized at different temperatures, and the results showed that the activation energy of ECNs decreased with the increase of carbonization temperature.     

Collecting electrospun nanofibers with patterned electrodes

Electrospinning is a simple, versatile, and useful technique for fabricating nanofibers from a rich variety of functional materials. The nanofibers are usually collected as nonwoven mats, in which the fibers are randomly oriented. We have recently demonstrated that the nanofibers can be uniaxially aligned by introducing an insulating gap into the conductive collector. To elucidate the mechanism of alignment, we have systematically studied the effect of the area and geometric shape of the insulating gap on the deposition of fibers. By modeling the electrostatic forces acting on the fiber, it was established that the fibers tended to be oriented along a direction such that the net torque of electrostatic forces applied to the two ends of a discrete segment of the fiber were minimized. By varying the design of electrode pattern, it was possible to control both alignment and assembly of the electrospun nanofibers.     

A novel non-enzymatic glucose sensor based on nickel (II) oxide electrospun nanofibers

A new enzymeless glucose sensor has been fabricated via electrospinning technology and subsequent calcination. The morphology and structure of the as-prepared nanofibers have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The electrocatalytic oxidation of glucose in alkaline medium at nickel oxide modified glassy carbon electrodes has been investigated. The modified electrodes offer excellent electrocatalytic activity toward the glucose oxidation at low positive potential (0.3 V). Glucose has been determined chronoamperometrically at the surface of NiO nanofibers modified electrode in 0.5 mM NaOH. Under the optimized condition, the calibration curve is linear in the concentration range of 2 x 10(-3) mM - 1 mM, and 1 mM - 9.5 mM. The detection limit (signal-to-noise 3) and response time are 3.394 x 10(-6) M and 2 s, respectively. The NiO electrospun nanofibers is easy to prepare and feasible in economy. The modified electrode is steady and can be used repeatedly, so it is reasonable to expect its broad use in non-enzymatic glucose sensor.     

Photoluminescent properties of Eu3+ doped electrospun CeO2 nanofibers

In this study, CeO₂ nanofibers and that doped with Eu³⁺ were prepared via a facile electrospinning route and annealed at different temperatures ranging from 500 to 900 °C. Their structures were investigated using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Photoluminescence properties of the nanofibers were studied in detail. It was found that the nanofibers with Eu% concentration of 0.67 mol.% and annealed at 700 °C exhibited the highest intensities of the luminescence peaks between 550 and 650 nm.     

Hierarchical nanostructures of copper(II) phthalocyanine on electrospun TiO(2) nanofibers: controllable solvothermal-fabrication and enhanced visible photocatalytic properties

In the present work, 2,9,16,23-tetranitrophthalocyanine copper(II) (TNCuPc)/TiO(2) hierarchical nanostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), UV-vis diffuse reflectance (DR), Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric and differential thermal analysis (TG-DTA) were used to characterize the as-synthesized TNCuPc/TiO(2) hierarchical nanostructures. The results showed that the secondary TNCuPc nanostructures were not only successfully grown on the primary TiO(2) nanofibers substrates but also uniformly distributed without aggregation. By adjusting the solvothermal fabrication parameters, the TNCuPc nanowires or nanoflowers were facilely fabricated, and also the loading amounts of TNCuPc could be controlled on the TNCuPc/TiO(2) hierarchical nanostructural nanofibers. And, there might exist the interaction between TNCuPc and TiO(2). A possible mechanism for the formation of TNCuPc/TiO(2) hierarchical nanostructures was suggested. The photocatalytic studies revealed that the TNCuPc/TiO(2) hierarchical nanostructures exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TNCuPc or TiO(2) nanofibers under visible-light irradiation.     

Role of jet path on uniformity of electrospun nanofibers

This paper reports on the role of jet path in obtaining uniform and bead free nanofibers during electrospinning process. Polyethylene oxide (PEO) nanofibers were electrospun by varying the molecular weight of PEO and concentration of poly allylamine hydrochloride (PAH) in the spinning solution. Different modes of fiber formation were captured by a camera and analyzed further by image processing technique in order to assess their influence in the formation of uniform and bead free nanofibers. Two different jet paths during fiber formation, namely straight and whipping were assessed. The length of the straight jet path during the fiber formation played a major role in the formation of uniform nanofibers in comparison to the length of the whipping path. The diameter and surface morphology of the nanofibers were characterized by SEM. Nanofibers spun using higher concentration of PAH exhibited longer straight jet path and therefore more uniform nanofibers in comparison to that spun at lower concentration of PAH. Flow simulations of the electrically charged polymer solutions were carried out to observe the changes in the solution flow rate and Taylor cone shape. Increased flow rate and changes in the Taylor cone shape with the increasing PAH concentration in low molecular weight polymer were observed.     

Fabrication and characterization of electrospun titania nanofibers

Titania (TiO₂) nanofibers were fabricated by electrospinning three representative spin dopes made of titanium (IV) n-butoxide (TNBT) and polyvinylpyrrolidone (PVP) with the TNBT/PVP mass ratio being 1/2 in three solvent systems including N,N-dimethylformamide (DMF), isopropanol, and DMF/isopropanol (1/1 mass ratio) mixture, followed by pyrolysis at 500 °C. The detailed morphological and structural properties of both the as-electrospun precursor nanofibers and the resulting final TiO₂ nanofibers were characterized by SEM, TEM, and XRD. The results indicated that the precursor nanofibers and the final TiO₂ nanofibers made from the spin dopes containing DMF alone or DMF/isopropanol mixture as the solvent had the common cylindrical morphology with diameters ranging from tens to hundreds of nanometers, while those made from the spin dope containing isopropanol alone as the solvent had an abnormal concave morphology with sizes/widths ranging from sub-microns to microns. Despite the morphological discrepancies, all precursor nanofibers were structurally amorphous without distinguishable phase separation, while all final TiO₂ nanofibers consisted of anatase-phased TiO₂ single-crystalline grains with sizes of approximately 10 nm. The electrospun TiO₂ nanofiber mat is expected to significantly outperform other forms (such as powder and film) of TiO₂ for the solar cell (particularly dye-sensitized solar cell) and photo-catalysis applications.     

Glassy carbon nanofibers from electrospun cellulose nanofiber

Journal of Materials Science - Glassy carbon nanofibers (g-CNFs) with diameter of ca. 45 nm were prepared from electrospun cellulose nanofibers (CelluNFs) by two sequential steps:...     

Fabrication and characterization of electrospun mullite nanofibers

Continuous mullite (3Al₂O₃·2SiO₂) nanofibers were fabricated by a sol-gel electrospinning technique. The detailed crystallization development and micromorphological evolution of both the as-electrospun nanofibers and the sintered mullite nanofibers were investigated. Results indicated that the spinnability and micromorphological evolution of mullite nanofibers are largely dependent on the viscosity η of the mullite sol, which can be adjusted by polyvinylprrolidone (PVP) content. Mullite nanofibers with common cylindrical morphology and diameters ranging from 400 nm to 800 nm could be obtained easily and rapidly when PVP content is ranged from 5 wt.% to 8 wt.%. High purity polycrystalline mullite nanofibers with diameters of about 200 nm were obtained after sintering at 1200 °C for 2 h. All sintered nanofibers consisted of single crystalline grains with size of approximately 100 nm.     

TiO2纳米纤维的制备及其对染料的光催化降解性能

采用溶胶-凝胶与静电纺丝技术相结合的方法,将聚乙烯吡咯烷酮(PVP)和钛酸四正丁酯混合制得前驱体溶液,纺丝得PVP/TiO2复合纳米纤维,然后经500℃高温煅烧制备了TiO2纳米纤维光催化剂,通过其对阳离子艳红5GN、弱酸性黄GN、雷马素蓝RR等染料的降解研究了TiO2纳米纤维的光催化性能。利用扫描电子显微镜(SEM)观察了PVP/TiO2和TiO2纳米纤维的形貌结构;傅里叶变换红外光谱(FT-IR)证实了TiO2纳米纤维的形成;通过X射线衍射仪(XRD)对TiO2纳米纤维的晶型及晶粒大小进行了分析。结果表明制备出的TiO2纳米纤维形貌稳定,具有锐钛矿型TiO2结晶形态并对染料具有很好的光催化降解效果。     

Analysis of optical properties of TiO2 nanoparticles and PAN/TiO2 composite nanofibers

The aim of the study was the production of thin composite nanofibrous mats PAN/TiO₂ nanoparticles using the electrospinning method from solution of PAN/TiO2/DMF. TiO₂ nanoparticles were obtained using sol-gel method. To prepare sol mixture, organic alkoxides precursor of titanium isopropoxide and water solution were used. Calcination of TiO-gel and following milling were carried out to obtain nanoparticles of TiO₂ rutile phase. In order to analyze the structure of the obtained particles, we used X-ray diffraction analysis (XRD) and energy dispersive spectrometer (EDS). Analysis of the morphology and chemical composition of the resulting composite nanofibers were carried out using a scanning electron microscope (SEM) with EDS. The analysis of the optical properties and the energy band structure prepared nanoparticles and thin composite nanofibrous mats were determined by spectral analysis of the absorbance as a function of the energy of radiation obtained using a UV–Vis spectrophotometer.     

Preparation of rutile TiO2 nanofibers by TiO2 sol intercalation of ultrafine layered titanate

To prepare TiO₂ intercalated tetratitanate, TiO₂ solution and ultrafine layered titanate K₂Ti₄O₉ obtained via solid-state reaction by using nanometer-sized TiO₂ as raw material were used as guest and host materials respectively. The structure and morphology of the resulting samples were characterized by XRD and TEM experiments. It was found that during the intercalation process, the interlayer distance was expanded step-by-step and the interlayer structure of titanate might be destroyed and degraded to slits by prolonging the solution intercalation time. Rutile TiO₂ nanofibers with the average size of 5 × 50 nm were obtained at room temperature while the duration time was prolonged to 72 h.     

Deposition of gold nanoparticles on electrospun MgTiO3 ceramic nanofibers

A simple method to deposit spherical gold nanoparticles on the surface of MgTiO3 ceramic nanofibers is presented. Electrospun MgTiO3/poly(vinyl acetate) (PVAc) hybrid nanofibers were calcined at 650 degrees C to obtain phase pure ceramic MgTiO3 nanofibers with 100-150 nm diameters. These ceramic nanofibers were immersed in an aqueous solution of HAuCl4 containing poly(vinyl alcohol) (PVA) as capping agent followed by photoreduction at 365 nm to get a novel Au-MgTiO3 nanocomposite. The formation of gold nanoparticles upon irradiation was confirmed by the appearance of a surface plasmon band (SPB) at 590 nm in the UV-visible absorption spectra. The surface morphology and elemental compositions were analyzed by the scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX), and transmission electron microscope (TEM). X-ray diffraction (XRD) and selected area diffraction (SAED) pattern in TEM revealed the crystallization of gold by exhibiting strong diffractions correspond to Au(111) and Au(200) crystalline planes in addition to the MgTiO3 diffraction.