Novel Dispersion of 1D Nanofiber Fillers for Fast Ion-Conducting Nanocomposite Polymer Blend Quasi-Solid Electrolytes for Dye-Sensitized Solar Cells.

Electrospun nanocomposite polymer blend poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(methyl methacrylate) (PMMA) membranes with a novel dispersion of x wt % of one-dimensional (1D) TiO2 nanofiber fillers (x = 0.0-0.8 in steps of 0.2) were developed using the electrospinning technique. The developed nanocomposite polymer membranes were activated using various redox agents such as LiI, NaI, KI, and tetrabutyl ammonium iodide (TBAI). Introduction of the 1D TiO2 nanofiber fillers improves the amorphous nature of the blended polymer membrane, as confirmed through X-ray diffraction (XRD) and Fourier transform infrared (FTIR), and yielded an electrolyte uptake of over 480% for a 6 wt % TiO2 nanofiber filler-dispersed sample. PVDF-HFP/PMMA-1D 6 wt % TiO2 nanofiber fillers with the LiI-based redox electrolyte provided a high conductivity of 2.80 × 10-2 S cm-1 and a power conversion efficiency (PCE) of 8.08% to their fabricated dye-sensitized solar cells (DSSCs). The observed better ionic conductivity and efficiency of the fabricated DSSCs could be due to the faster movement of the smaller-ionic-radius (Li) ions entrapped inside the amorphous polymer. This enhanced mobility of ions in the quasi-solid electrolyte leads to faster regeneration of the depleting electrons in the photoanode, resulting in improved efficiency. Further, the achieved high conductivity was analyzed in terms of the dynamics and relaxation mechanisms involved by the ionic charge carriers with complex impedance spectroscopy using a random barrier model and Havriliak-Negami formulation. It was observed that the high-conducting PVDF-HFP/PMMA-1D 6 wt % TiO2 nanofiber fillers with LiI-based redox electrolyte show better ac conductivity parameters such as a σ of 5.82 × 10-2 S cm-1, ωe (12685 rad s-1), τe (0.909 × 10-4 s), and n (0.578). Also, dielectric studies revealed that the high-conducting sample has a higher dielectric constant and subsequently high loss. The J-V characteristics were studied using the equivalent circuit of a single-diode model, and the parameters influencing the photovoltaic performance were determined by Symbiotic Organisms Search (SOS) algorithm. The results suggest that the high-efficient sample possesses a minimum series resistance of 1.33 Ω and a maximum shunt resistance of 997 Ω. Hence, the highest-conducting electrospun-blended polymeric nanocomposite (PVDF-HFP-PMMA-6 wt % TiO2 nanofiber fillers) with LiI-based redox agent and tert-butyl pyridine (TBP) additive as the polymer quasi-solid electrolyte nanofibrous membrane can be a better electrolyte for high-performance dye-sensitized solar cell applications.

ß-PVDF based electrospun nanofibers - A promising material for developing cardiac patches.

Necrosis in heart muscles can permanently hinder the natural healthy rhythm of heart pumping mechanism. The damaged muscular tissues are replaced by scar tissues and burdens the healthy muscles resulting in further attenuated functioning of heart. Since, human heart muscles cannot regenerate naturally or it has been thought so, pharmacological procedures such as using a heart assist device are followed to restore the lost function of heart. Stem cell engineering and cardiac patches offers promising prospects with their cutting edge research reports. Cardiac patches offers a viable solution as they can also function as an implant to assist in offering the mechanical support the damaged muscles were capable of. Designing cardiac patches to suit multiple functions is not only challenging but also perilous due to the target organ with which it will be interfaced. Sensor based, electrically active, miniaturized circuitry etc., poses a huge threat to the individual in whom the device/patch is implanted. In this paper, we propose a hypothesis on choosing ß-PVDF based nanocomposites as the inimitable material for designing implantable cardiac patches. ß-PVDF based nanocomposite materials is expected to exhibit piezoelectric effect and contribute to the adherence, proliferation and maturation of stem cells. Physico-chemical characterizations followed by in vitro cell line studies were performed in ought to confirm the same. The results revealed that the ß-PVDF based nanocomposite material was mechanically stable and supportive in cardiomyocyte adherence and differentiation when compared to standard non piezoelectric scaffolds (control). Hence, an implantable ß-PVDF based novel electrospun nanocomposite scaffold is hypothesized to be the hour of need in conjugation with stem cell engineering for repairing damaged heart muscles.

Scalable novel PVDF based nanocomposite foam for direct blood contact and cardiac patch applications.

Scalable novel beta phase polyvinylidene fluoride-poly(methyl methacrylate) (PVDF-PMMA) polymer blend based nanocomposite foam with hydroxyapatite (HAp) and titanium dioxide (TiO2) as nanofillers (ß-PVDF-PMMA/HAp/TiO2) (ß-PPHT-f), was prepared by using salt etching assisted solution casting method. The prepared ß-PPHT-f nanocomposite material was characterized using XRD, FT-IR, SEM-EDS. The XRD and FTIR results confirmed the formation of ß phase of ß-PPHT-f. The SEM and EDS results confirmed the formation of high porous structured closed cell type morphology of ß-PPHT-f. It also, confirmed the uniform distribution of Ti, Ca, P, N and O, in ß-PPHT-f. Contact angle measurements performed using sessile drop method with water and EDTA treated blood (EDTA blood) as probe liquids revealed that ß-PPHT-f is hydrophilic with contact angle of 48.2° as well as hemophilic with contact angle of 13.7°. Porosity, fluid absorption and retention investigation by gravimetric analysis revealed that ß-PPHT-f was 89.2% porous and can absorb and retain 139.15% and 87.05% of water and blood, respectively. The hemolysis assay performed as per ASTM F756 procedure revealed that ß-PPHT-f is non hemolytic. Also, the Leishman stained blood smears prepared from whole blood incubated with ß-PPHT-f for 3, 4, 5 and 6 h at 37 °C revealed that the blood cells were not affected by ß-PPHT-f, its surface morphology and elemental composition. H9c2 cell line studies on a transparent film prepared using ß-PPHT-f revealed that the elemental composition of the nanocomposite favored H9c2 cell adhesion and differentiation. All the characterization results indicate that the newly developed scalable novel ß-PPHT-f is hemocompatible and cardiomyocyte compatible, suggesting it as a useful material for direct blood contact and cardiac patch applications.