Hollow Nanofibres Research Articles

Titanium (IV) oxide composite hollow nanofibres with silver oxide outgrowth by combined sol–gel and electrospinning techniques and their potential applications in energy and environment

A two-dimensional nanostructure composed of Ag2O nanobranches attached to TiO2 hollow nanofibres (denoted as 2D Ag2O/TiO2) was successfully prepared via sol–gel and coaxial electrospinning techniques. The Ag/TiO2 hollow nanofibres were fabricated and calcined in ambient air at 500 °C. By calcination, the removal of organic materials and the formation of anatase TiO2 were achieved with a well-retained hollow structure. The embedded Ag nanoparticles functioned as seeds for the Ag2O outgrowth on the TiO2 surface using a hydrothermal treatment at different times and temperatures, which caused the change in physical appearance, surface area, and electrical conductivity of 2D Ag2O/TiO2. A high quantity of Ag2O nanobranches on TiO2 nanofibres were obtained with increasing the temperature from 110 to 115 °C and the reaction time to 60 min. Consequently, the electrochemical active surface area (EASA) value was maximised to 65.25 cm2 per cm2 with an enhanced electrical conductivity of 91.3 ± 3.9 × 10−2 S cm−1. Further studies on the depth-profiles of Ag, Ti, and O revealed the presence of Ag2O attached to the core structure of TiO2. The photoelectrochemical and photocatalytic tests confirmed the excellent physical and electrochemical properties of 2D Ag2O/TiO2 (@115 °C, 60 min) for use in energy and environmental applications.Graphical

Fabrication Procedure for a 3D Hollow Nanofibrous Bifurcated-Tubular Scaffold by Conformal Electrospinning

Electrospinning has shown great potential for the fabrication of 3D nanofibrous tubular scaffolds for bifurcated vascular grafts. However, fabrication of complex 3D nanofibrous tubular scaffolds with bifurcated or patient-specific shapes remains limited. In this study, a 3D hollow nanofibrous bifurcated-tubular scaffold was fabricated by the uniform and conformal deposition of electrospun nanofibers via conformal electrospinning. By conformal electrospinning, electrospun nanofibers are conformally deposited onto a complex shape, such as the bifurcated region, without large pores or defects. Owing to conformal electrospinning, a corner profile fidelity (FC), a measure of conformal deposition of electrospun nanofibers at the bifurcated region, was increased 4 times at the bifurcation angle (θB) of 60°, and all FC values of the scaffolds reached 100%, regardless of the θB. Furthermore, the thickness of the scaffolds could be controlled by varying the electrospinning time. Leakage-free liquid transfer was successfully achieved owing to the uniform and conformal deposition of electrospun nanofibers. Finally, the cytocompatibility and 3D mesh-based modeling of the scaffolds were demonstrated. Thus, conformal electrospinning can be used to fabricate leakage-free and complex 3D nanofibrous scaffolds for bifurcated vascular grafts.

Design and electrospinning synthesis of SrF2:Er3+/Yb3+ unidimensional nanostructural materials with tunable upconverting fluorescence

In order to develop new morphology and properties of up-converting fluorescent materials, SrF2:Er3+/Yb3+ up-converting fluorescent unidimensional nanostructural materials including nanofibres, nanostrips and hollow nanofibres have been designed and successfully constructed via a uniaxial electrospinning associated with a bi-crucible fluorination technology. Controllable fabrication of unidimensional nanostructural materials is successfully realized via controlling the ingredients and proportions of the spinning solutions and spinning parameters. The influences of roasting temperature, molar proportion of Yb3+ to Er3+ and morphology on the up-converting fluorescence of the samples are studied in detail, and further tunable fluorescence is achieved. Upon the excitation of 980-nm laser, the unidimensional nanostructural materials display excellent up-converting fluorescence. The bright green emissions at 526 and 548 nm are assigned to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 energy levels transition of the Er3+ ions, respectively, and the weaker red characteristic emission peak at 652 nm is attributed to the 4F9/2 → 4I15/2 energy level transition of Er3+. Further, the detailed fluorescent mechanism and the formative mechanism of the unidimensional nanostructural materials are expounded in-depth, and the fabrication techniques are built. Much more importantly, the designing philosophy and fabricating technology can be popularized to manufacture other metal fluoride unidimensional nanostructural materials. The as-synthesized SrF2:Er3+/Yb3+ unidimensional nanostructural materials may find tremendous potential applications in the areas of emitting diodes, displaying devices, optical probes, bioimaging, sensing, drug delivery and lithium-sulfur batteries.

Investigation of slow release of urea from biodegradable single- and double-layered hollow nanofibre yarns

Urea is the most common form of nitrogenous fertiliser. Recently, research has focused on the development of delivery systems to prolong fertiliser release and prevent fertiliser loss through leaching and volatilization. This study investigates and compares single- and double-layered hollow nanofibrous yarns as novel delivery systems to encapsulate and release urea. Single-layered hollow poly l-lactic acid (PLLA) nanofibre yarns loaded with urea fertiliser were fabricated using a customized electrospinning. Double-layered hollow nanofibre yarns were produced by electrospinning polyhydroxybutyrate (PHB) nanofibres as an outer layer, with urea-impregnated PLLA nanofibres as the inner layer. Scanning electron microscopy (SEM) with an energy-dispersive spectroscopy (EDS) was used to characterize the morphology of hollow electrospun nanofibre yarns. A total nitrogen instrument (TNM-1) was used to study the urea release from single- and double-layered hollow nanofibres yarn in water. A Carbon:Nitrogen (CN) elemental analyser determined encapsulated nitrogen in PLLA nanofibres samples. Results indicated that urea-impregnated double-layered hollow nanofibre yarns significantly started nitrogen releasing at much lower amount during first 12 h compared to single-layered hollow nanofibre yarns (P value = 0.000). In conclusion, double-layered hollow nanofibre yarn has potential as an effective alternative to current methods for the slow release of fertilisers and other plant-required chemicals.

Preparation and Characterization of Temperature-responsive Hollow Nanofibrous Membrane

Preparation and Characterization of Temperature-responsive Hollow Nanofibrous Membrane

Fabrication and Characterization of Mg0.6Ni0.4O Hollow Nanofibers by Electrospinning.

Mg0.6Ni0.4O hollow nanofibers with diameter of 300-600 nm were successfully prepared by elecrospinning a precursor mixture of polyacrylonitrile (PAN)/(magnesium nitrate+ nickel nitrate), followed by calcination treatment of the electrospun polymer/inorganic composite fibers. The resulting Mg0.6Ni0.4O hollow nanofibers were characterized with X-ray diffraction, Brunauere-Emmette-Teller, FT-IR spectra and scanning electron microscopy. Mg0.6Ni0.4O hollow nanofibres were obtained after being calcined at 500 degrees C and their surface became coarse with increasing of calcination temperatures. Possible formation mechanism for Mg0.6Ni0.4O hollow nanofibers was preliminarily proposed.

Mesoporous Li1.2Mn0.54Ni0.13Co0.13O2 nanotubes for high-performance cathodes in Li-ion batteries

One-dimensional nanotubes constructed from interconnected Li1.2Mn0.54Ni0.13Co0.13O2 secondary particles of diameters measuring ca. 40 nm, were synthesized by a one-pot electrospinning method. Novel electrodes were constructed from (a) nanoparticles only, and (b) hollow nanofibres, and employed as cathodes in Li-ion batteries. The nanotube cathode exhibited impressive specific charge capacity, good cycling stability, and excellent rate capability. A discharge capacity of 140 mAh g−1 with capacity retention of 89% at 3 C was achieved after 300 cycles. The significant improvement of electrochemical performance is attributed to the high surface area of the nanotubes, well-guided charge transfer kinetics with short ionic diffusion pathways, and large effective contact area with the electrolyte during the cycling process.

A novel anode comprised of C&N co-doped Co3O4 hollow nanofibres with excellent performance for lithium-ion batteries.

C&N co-doped Co3O4 hollow nanofibres are prepared by combining the electrospinning technique and the hydrothermal method, which show a high reversible capacity and excellent cycling stability as anode materials for Li-ion batteries. DFT calculations give a good explanation for the experimentally enhanced conductivity in C&N co-doped Co3O4 hollow nanofibres.

Electrospun manganese-cobalt oxide hollow nanofibres synthesized via combustion reactions and their lithium storage performance.

Mesoporous hollow fibres of MnCo2O4 and CoMn2O4 were synthesized by electrospinning and highly exothermic oxygen-mediated combustion reactions during calcination, in which the heating rate affected the final fibre morphology (e.g., single- or double-shell). The anodes consisting of hollow fibres showed excellent electrochemical properties for lithium-ion batteries.

Morphology control of Nb-doped SnO2 nanofibres formed via electrospinning: From hollow nanofibres to dense nanofibres

Morphology control of Nb-doped SnO2 nanofibres formed via electrospinning: From hollow nanofibres to dense nanofibres

Highly Active TiO2/Polyelectrolytes Hybrid Multilayered Hollow Nanofibrous Photocatalyst Prepared from Electrouspun Fibers Using Electrostatic Layer-by-Layer Technique

Compared to conventional film photocatalysts, fiber photocatalyst has a greater surface-to-volume ratio and a 3-D open structure that allows its surface active sites to be accessible for reactants more easily and effectively. However, TiO 2 powder (Degussa P25), by itself, cannot be prepared in the form of fibers, but with the help of a polymer nanofiber, TiO 2 particles can be immobilized in a fibrous network of polyelectrolyte. Here, hybrid multilayered hollow nanofibers (HMHNFs) composed of TiO 2 /polyelectrolyte (PE) have been prepared by a combination of a electrospinning method and layer-by-layer (LBL) technology. The results show that both the average diameter and the wall thickness of the HMHNFs can be well controlled by the template, as well as the number of coating layers. The dried morphology of the obtained HMHNFs is dependent on the inner deposited numbers of the polyelectrolyte layers. When compared with other nanostructured TiO 2 materials, such as commercial TiO 2 nanoparticles (P25, Degussa) and TiO 2 films, the hollow TiO 2 /PE hybrid nanofibers exhibited higher photocatalytic activities.

Electrospinning of Nanofibres: Towards New Techniques, Functions, and Applications

Nanofibres, core–shell nanofibres, as well as hollow nanofibres and nanotubes based on polymers, serve as a platform for a broad range of applications as filters, textiles, in photonics, sensors, catalysis, or in medicine and pharmacy. Such nanoobjects become available by techniques such as the well-known electrospinning and the more recently developed co-electrospinning of nanofibres. Electrospinning takes place in the latter case by two or more concentrically arranged dies that yield core–shell fibres or fibres with droplet-like inclusions arranged along the centre of the fibres, where the inclusions are composed of polymers, low-molar-mass synthetic functional units, or molecules of biological origins such as proteins. Furthermore, template methods have been developed using electrospun nanofibres or a porous substrate, which yield core–shell fibres of complex architectures, with or without gradient structures or hollow nanofibres and nanotubes. These techniques are not restricted to polymers of synthetic and natural origin, but are able – based on precursor substances – to deliver nanofibres and nanotubes also composed of metals, glasses, and ceramics. Furthermore, these preparation techniques allow the direct introduction into these nanostructures of specific functional compounds such as semiconductor or catalytic nanoparticles and chromophores, in addition to enzymes, proteins, microorganisms, etc. during the preparation process in a very gentle way. Of particular interest are such nanostructures in medicine and pharmacy, for instance, as scaffolds for tissue engineering or as drug-delivery systems for tumour therapy.