T. S. Natarajan

Electrospun NiO nanofibers as cathode materials for high performance asymmetric supercapacitors

Asymmetric supercapacitors (ASCs) based on aqueous electrolytes have received widespread attention in energy research in recent years because they provide high energy and power densities in addition to being ‘green electrolyte’. Herein, we report an ASC built with electrospun nanofibers of NiO as battery type cathode material and commercially available high surface area activated carbon as capacitor type anode material with appropriate mass loadings. We synthesized high aspect ratio nanofibers of NiO by simple and cost effective sol–gel based electrospinning followed by annealing. In the end, these nanofibers were composed of densely packed hexagonal nanoparticles of polycrystalline NiO having diameters of ∼15 nm. The ASC was capable of operating in the potential window of 1.5 V in 6 M KOH solution with a gravimetric capacitance of 141 F g−1 and energy density of 43.75 W h kg−1. The ASC showed high retention of the specific capacitance for 5000 galvanostatic charge–discharge cycles with improved coulombic efficiency.

Fabrication and characterization of a collagen coated electrospun poly(3-hydroxybutyric acid)–gelatin nanofibrous scaffold as a soft bio-mimetic material for skin tissue engineering applications

Wound healing is a global health care problem. The use of a suitable dressing material by means of a nanofibrous scaffold with traditionally important medicine can help to repair the damaged skin tissue. An ideal wound dressing material should mimic the function of an extracellular matrix with its improved physiochemical, biological and antimicrobial properties. In this study, the significance features of a collagen coated electrospun poly(3-hydroxybutyric acid)–gelatin nanofibrous scaffold with a bioactive Coccinia grandis extract (CPE) meets the requirements for a wound dressing material. The nanofibrous scaffold with collagen has an attraction for fibroblast, which increases cell adhesion and proliferation. The fabricated nanofibrous scaffold with collagen was characterized physio-chemically using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and it showed acceptable antibacterial property with both Gram positive and Gram negative bacteria. The thermal and in vitro stability of the nanofibrous scaffold was studied and it was found to have stability more than that required for a wound dressing material. The nanofibrous scaffold supports good swelling property with better porosity for oxygen permeability. The mechanical property of the nanofibrous scaffold showed a Youngs modulus of 2.99 ± 0.16 MPa. The biocompatibility of the nanofibrous scaffold exhibits increased cell adhesion and proliferation of both NIH 3T3 fibroblast and human keratinocytes (HaCaT) cell line. The in vitro fluorescence staining of the nanofibrous matrix using Calcein AM and DAPI exhibits the cell material interaction of the collagen coated nanofibrous scaffold corresponding to increased cell adhesion and proliferation. This approach with a nanofibrous scaffold coated with collagen can be a promising tool in skin tissue engineering and can be useful as a wound dressing material in skin tissue engineering applications.

Beaded manganese oxide (Mn2O3) nanofibers: preparation and application for capacitive energy storage

Here, we report a surfactant-free electrospinning based method for the synthesis of beaded manganese oxide (Mn2O3) nanofibers and their application as supercapacitor electrodes. The beaded morphology of the fibers was confirmed through electron microscopic analysis. The highly crystalline nature and lattice strain of the fibers were verified by X-ray diffraction analysis while the chemical composition of the fibers was studied by using X-ray photoelectron and Raman spectroscopy. The electrochemical properties of the Mn2O3 nanofiber electrode were investigated using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in a 0.5 M Na2SO4 aqueous electrolyte. The specific capacitance of the Mn2O3 beaded nanofibers was found to be 358 F g−1 at a current density of 0.5 A g−1. Lattice strain-induced ionic and electronic defects enhanced the surface properties of the Mn2O3 nanofibers, thereby improving their electrochemical properties.

Microwave Hall mobility and electrical properties of electrospun polymer nanofibers

Composite nanofibers from poly(methylmethacrylate)- (PMMA-) conducting polyaniline [PANI(HCl)] were prepared by using the electrospinning technique. The morphology and structural details of the fibers were characterized by SEM and the ac conductivity of the composite fibers found was measured to be ∼ 2.17×10−4 S/cm which is very good enhancement compared to that of pure PMMA and conductivity of PANI-PMMA thin films as well. The conductivity is found to increase with increase in the polyaniline content in the composite. Microwave Hall mobility measurements on electrospun nanofibers showed 17 cm2/V s for the lower loadings. With further increase in the polyaniline content in the composite, the mobility value decreases which is attributed to the increase in carrier-carrier scatterings.

Durable keratin-based bilayered electrospun mats for wound closure

A bilayered nanofibrous scaffold with rapid wound healing properties is found to be suitable for tissue regeneration applications. The objective of this study is to reveal the fabrication of a poly(3-hydroxybutyric acid) (P)-gelatin (G) nanofibrous mat through electrospinning, with a horn keratin-chitosan-based biosheet (KC) as a bilayered nanofibrous scaffold. The mupirocin (D)-loaded horn KC biosheet (KCD) acts as the primary layer over which PG nanofibers were electrospun to act as the secondary layer. It is shown that this engineered bilayered nanofibrous scaffold material (KC-PG) should fulfill the functions of the extracellular matrix (ECM) by elucidating its function in vitro and in vivo. The bilayered nanofibrous scaffold was designed to exhibit improved physiochemical, biological and mechanical properties, with better swelling and porosity for enhanced oxygen permeability, and it also exhibits an acceptable antibacterial property to prevent infection at the wound site. The bilayered nanofibrous scaffold assists in better biocompatibility towards fibroblast and keratinocyte cell lines. The morphology of the nanofibrous scaffold aids increased cell adhesion and proliferation with cell material interactions. This was elucidated with the help of in vitro fluorescence staining against both cell lines. The bilayered KCD-PG nanofibrous scaffold material gives accelerated wound healing efficiency during in vivo wound healing. The results showed the regulation of growth factors with enhanced collagen synthesis, thereby helping in faster wound healing.

Giant magnetoresistance of Fe3O4-polymethylmethacrylate nanocomposite aligned fibers via electrospinning

This paper describes the results of investigations on giant negative magnetoresistance (GMR) in nanocomposite aligned fibers prepared using electrospinning. The nanocomposite contains polymethylmethacrylate (PMMA) matrix and the nanoparticles of polymer (PMMA) grafted magnetite, Fe3O4 (PGM). Even for the low magnetic field (1T) a GMR of about 50% was observed for low loading (5wt%) of PGM at room temperature. The fibers were characterized using scanning electron microscope and high resolution transmission electron microscope. X-ray diffraction (XRD) patterns were recorded for clean PMMA fibers, PMMA granules, and PGM nanoparticles. The dc conductivity was calculated from the I-V characteristics for the fibers at room temperature.