Browsing by Author "Liyanage, J. P."

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    Antibacterial fabrics: ZnO nanoparticles infused polymer nanofiber membrane
    (Faculty of Science, University of Kelaniya Sri Lanka, 2024) Yapa, Y. M. C. P. C. B.; Sivakumar, V.; Liyanage, J. P.
    Bacterial infections are a leading global health crisis, ranking as the second largest cause of death worldwide. This study explores the innovative potential of using polyvinyl alcohol (PVA) nanofiber membranes infused with ZnO nanoparticles to create antibacterial clothing. ZnO, is a n-type semiconductor with a band gap of approximately 3.37 eV, is renowned for its biosafety and biocompatibility. It exists in various forms such as nanowires, nanorings, nanospheres, and nanohelices, showcasing its versatility. Additionally, ZnO nanoparticles exhibit significant antibacterial properties against a wide range of bacterial species due to their photocatalytic activity, making them a promising solution in the fight against transmission of bacterial infections. Electrospinning has been employed to fabricate PVA nanofiber membranes, with PVA emerging as the predominant polymer of choice due to its non-toxicity, biocompatibility, and superior electrospinning-ability compared to other polymers. The agar disc diffusion method was carried out to observe antibacterial activity of ZnO nanoparticles and PVA-ZnO nanofiber membranes against Escherichia coli DH-5α (E-coli) strain. A distinct inhibition, zone with an average width of approximately 0.5 cm, was clearly observable using commercially available ZnO nanoparticles. PVA-ZnO nanofiber membranes with different ZnO concentrations were fabricated starting from 0.5 wt% to 6.0 wt%, in steps of 0.5 wt%, on a gauze as a substrate, by electrospinning PVA-ZnO polymer solutions. The antibacterial activity of the PVA-ZnO nanofiber membranes started to appear when the ZnO concentration was 5.0 wt%. These membranes exhibited an average inhibition zone width of approximately 0.1 cm. Also, PVA nanofiber membrane alone did not show an inhibition zone. Surface morphology of each nanofiber was analyzed using scanning electron microscope (SEM). X-ray Fluorescence (XRF) analysis for the commercially available ZnO nanoparticles was performed to determine the chemical purity of the ZnO. Fourier Transform Infrared spectroscopy (FTIR) analysis was performed to determine the structural change due to the interaction between PVA and ZnO nanoparticles. Based on the findings, a minimum ZnO concentration of 5.0 wt% is necessary to achieve antibacterial activity against E-coli using PVA-ZnO nanofiber membranes. This concentration threshold underscores the critical role of ZnO in enhancing the membranes' effectiveness in fighting against bacterial pathogens.
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    Optimizing concentration of titanium dioxide nano-fillers in PEO gel-polymer electrolytes for enhanced performance of dye-sensitized solar cells
    (Faculty of Science, University of Kelaniya Sri Lanka, 2024) Chandrika, R. P.; Liyanage, J. P.; Wijayaratne, W. M. K. B. N.; Bandara, T. M. W. J.
    The influence of nano-composite gel-polymer electrolytes on the performance of dye-sensitized solar cells (DSSCs) has attracted significant attention recently. In this study, titanium dioxide nanoparticles (TiO2) with varying percentages were incorporated into a gel-polymer electrolyte in order to determine the optimal nanofiller (NF) concentration as well as to study the effect of NFs composition on conductivity in the polymer electrolyte and light to current conversion efficiency of DSSCs. For these purposes, TiO2 NFs with an average particle size of 13 nm were incorporated into polyethylene oxide (PEO) based gel-polymer electrolyte. The TiO2 nano-composite electrolyte series were prepared by varying the TiO2 NF composition from 0.0 to 25.0 wt.% relative to the PEO weight. The DSSCs were assembled by sandwiching NF incorporated polymer electrolyte between a multilayer photoanode sensitized with N719 dye and platinum electrode. The conductivity and light to current conversion efficiency depend on the NF composition in the polymer electrolyte. The electrical conductivity of the electrolyte and efficiency of DSSCs containing nano-composite electrolytes increases with the increase in TiO2 content up to 17.5 wt.% and then decreases with any further increase in TiO2 percentage. Temperature-dependent electrical conductivity of the prepared nanocomposite gel-polymer electrolytes was investigated by gradually increasing the temperature from 20 °C to 80 °C increments of 10 °C. The conductivity increased with rising temperature within this range, and the temperature dependence exhibited VTF (non-Arrhenius) behavior. The optimum TiO2 composition was found to be 17.5 wt.%, with a conductivity of 5.18 mS cm-1 at 20 °C, which increased to 10.43 mS cm-1 when the temperature was raised to 80 °C. Thus the highest recorded conductivity was observed at the temperature of 80 °C, testing temperature was not raised further as higher temperatures cause the release of I2 from the electrolyte. The conductivity enhancement with added TiO2 can be attributed to the change in the morphology of the polymer network. TiO2 NFs contribute to this process by inducing electrostatic interactions/Lewis acid-base interactions between O atoms of the PEO and hydroxyl group of the TiO2 particles. DSSC assembled with the polymer electrolyte containing 17.5 wt.% of TiO2 NFs (the highest conducting electrolyte) exhibited the highest photoelectric conversion efficiency of 7.30%, representing a 28.1% enhancement compared to the reference DSSCs assembled with a filler-free gel-polymer electrolyte, which had an efficiency of (5.70%).