No abstract

Hollow mesoporous one dimensional (1D) TiO(2) nanofibers are successfully prepared by co-axial electrospinning of a titanium tetraisopropoxide (TTIP) solution with two immiscible polymers; polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) using a core-shell spinneret, followed by annealing at 450 °C. The annealed mesoporous TiO(2) nanofibers are found to having a hollow structure with an average diameter of 130 nm. Measurements using the Brunauer-Emmett-Teller (BET) method reveal that hollow mesoporous TiO(2) nanofibers possess a high surface area of 118 m(2) g(-1) with two types of mesopores; 3.2 nm and 5.4 nm that resulted from gaseous removal of PEO and PVP respectively during annealing. With hollow mesoporous TiO(2) nanofibers as the photoelectrode in dye sensitized solar cells (DSSC), the solar-to-current conversion efficiency (η) and short circuit current (J(sc)) are measured as 5.6% and 10.38 mA cm(-2) respectively, which are higher than those of DSSC made using regular TiO(2) nanofibers under identical conditions (η = 4.2%, J(sc) = 8.99 mA cm(-2)). The improvement in the conversion efficiency is mainly attributed to the higher surface area and mesoporous TiO(2) nanostructure. It facilitates the adsorption of more dye molecules and also promotes the incident photon to electron conversion. Hollow mesoporous TiO(2) nanofibers with close packing of grains and crystals intergrown with each other demonstrate faster electron diffusion, and longer electron recombination time than regular TiO(2) nanofibers as well as P25 nanoparticles. The surface effect of hollow mesoporous TiO(2) nanofibers as a photocatalyst for the degradation of rhodamine dye was also investigated. The kinetic study shows that the hollow mesoporous surface of the TiO(2) nanofibers influenced its interactions with the dye, and resulted in an increased catalytic activity over P25 TiO(2) nanocatalysts.

We report the synthesis and electrochemical performance of one-dimensional TiO 2 −graphene composite nanofibers (TiO 2 −G nanofibers) by a simple electrospinning technique for the first time. Structural and morphological properties were characterized by various techniques, such as Xray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and BET surface area analysis. Lithium insertion properties were evaluated by both galvanostatic and potentiostatic modes in half-cell configurations. Cyclic voltammetric study reveals the Li-insertion/extraction by a two-phase reaction mechanism that is supported by galvanostatic charge−discharge profiles. Li/TiO 2 −G half-cells showed an initial discharge capacity of 260 mA h g −1 at current density of 33 mA g −1 . Further, Li/TiO 2 −G cell retained 84% of reversible capacity after 300 cycles at a current density of 150 mA g −1 , which is 25% higher than bare TiO 2 nanofibers under the same test conditions. The cell also exhibits promising high rate behavior with a discharge capacity of 71 mA h g −1 at a current density of 1.8 A g −1 .

No abstract

A simple, eco-friendly, and biomimetic approach using Thymus vulgaris ( T . vulgaris ) leaf extract was developed for the formation of ZnO-Ag nanocomposites (NCs) without employing any stabilizer and a chemical surfactant. T . vulgaris leaf extract was used for the first time, in a novel approach, for green fabrication of ZnO-Ag NCs as a size based reducing agent via the hydrothermal method in a single step. Presence of phenols in T . vulgaris leaf extract has served as both reducing and capping agents that play a critical role in the production of ZnO-Ag NCs. The effect of silver nitrate concentration in the formation of ZnO-Ag NCs was studied. The in-vitro Antimicrobial activity of NCs displayed high antimicrobial potency on selective gram negative and positive foodborne pathogens. Antioxidant activity of ZnO-Ag NCs was evaluated via (2,2-diphenyl-1-picrylhydrazyl) DPPH method. Photocatalytic performance of ZnO-Ag NCs was appraised by degradation of phenol under natural sunlight, which exhibited efficient photocatalytic activity on phenol. Cytotoxicity of the NCs was evaluated using the haemolysis assay. Results of this study reveal that T . vulgaris leaf extract, containing phytochemicals, possess reducing property for ZnO-Ag NCs fabrication and the obtained ZnO-Ag NCs could be employed effectively for biological applications in food science. Therefore, the present study offers a promising way to achieve high-efficiency photocatalysis based on the hybrid structure of semiconductor/metal.

We report the formation and extraordinary Li-storage properties of TiO2 hollow nanofibers by co-axial electrospinning in both the half-cell and full-cell configurations. Li-insertion properties are first evaluated as anodes in the half-cell configuration (Li/TiO2 hollow nanofibers) and we found that reversible insertion of ~0.45 moles is feasible at a current density of 100 mA g(-1). The half-cell displayed a good cyclability and retained 84% of its initial reversible capacity after 300 galvanostatic cycles. The full-cell is fabricated with a commercially available olivine phase LiFePO4 cathode under optimized mass loading. The LiFePO4/TiO2 hollow nanofiber cell delivered a reversible capacity of 103 mA h g(-1) at a current density of 100 mA g(-1) with an operating potential of ~1.4 V. Excellent cyclability is noted for the full-cell configuration, irrespective of the applied current densities, and it retained 88% of reversible capacity after 300 cycles in ambient conditions at a current density of 100 mA g(-1).

Combination of metal oxides and carbon has been a favourable practice for their application in high-rate energy storage mesoscopic electrodes. We report quasi 1D Fe 2 O 3 carbon composite nanofibers obtained by the electrospinning method, and evaluate them as the anode for Li ion storage. In the half-cell configuration, the anode exhibits a reversible capacity of 820 mA h g -1 at a current rate of 0.2C up to 100 cycles. At a higher current density of 5C, the cells still exhibit a specific capacity of 262 mAh g -1 . Compared to pure electrospun Fe 2 O 3 nanofibers, the capacity retention of Fe 2 O 3 C composite nanofiber electrode is drastically improved. The good electrochemical performance is associated with the homogenous dispersed Fe 2 O 3 nanocrystals on the carbon nanofiber support. Such structure prevents the aggregation of active materials, maintains the structure integrity and thus enhances the electronic conductivity during lithium insertion and extraction.

No abstract