Shrabanee Sen

Self-Poled Transparent and Flexible UV Light-Emitting Cerium Complex–PVDF Composite: A High-Performance Nanogenerator

Cerium(III)-N,N-dimethylformamide-bisulfate [Ce(DMF)(HSO4)3] complex is doped into poly(vinylidene fluoride) (PVDF) to induce a higher yield (99%) of the electroactive phases (β- and γ-phases) of PVDF. A remarkable enhancement of the output voltage (∼32 V) of a nanogenerator (NG) based on a nonelectrically poled cerium(III) complex containing PVDF composite film is achieved by simple repeated human finger imparting, whereas neat PVDF does not show this kind of behavior. This high electrical output resembles the generation of self-poled electroactive β-phase in PVDF due to the electrostatic interactions between the fluoride of PVDF and the surface-active positive charge cloud of the cerium complex via H-bonding and/or bipolar interaction among the opposite poles of cerium complex and PVDF, respectively. The capacitor charging capability of the flexible NG promises its applicability as piezoelectric-based energy harvester. The cerium(III) complex doped PVDF composite film exhibit an intense photoluminescence in the UV region, which might be due to a participation of electron cloud from negative pole of bipolarized PVDF. This fact may open a new area for prospective development of high-performance energy-saving flexible solid-state UV light emitters.

Improved breakdown strength and electrical energy storage performance of γ-poly(vinylidene fluoride)/unmodified montmorillonite clay nano-dielectrics.

A remarkable improvement in the dielectric breakdown strength (Eb) and discharge energy density (U e) of flexible polymer nanocomposites is realized by the incorporation of unmodified smectite montmorillonite (MMT) nanoclay into a poly(vinylidene fluoride) (PVDF) matrix. The resulting PVDF/MMT clay nanocomposite (PCN) films stabilize the γ phase and increase the path tortuosity via strong intercalation of the PVDF matrix into inorganic layered silicates without sacrificing the quality of surface morphology. The PCN films exhibits superior dielectric properties (up to ε r ∼ 28 and tan δ ∼ 0.032 at 1 kHz) than those of pure PVDF. As a result, a large increase in E b of 873 MV m(-1) and U e of 24.9 J cm(-3) is achieved. Subsequently, the PCN films possess more than 60% charge-discharge efficiency even at higher electric field and thus provide a scope to develop high energy density flexible and transparent materials for energy storage technologies.

Improved dielectric constant and breakdown strength of γ-phase dominant super toughened polyvinylidene fluoride/TiO2 nanocomposite film: an excellent material for energy storage applications and piezoelectric throughput.

Titanium dioxide (TiO2) nanoparticles (NPs) embedded γ-phase containing polyvinylidene fluoride (PVDF) nanocomposite (PNC) film turns to an excellent material for energy storage application due to an increased dielectric constant (32 at 1 kHz), enhanced electric breakdown strength (400 MV m-1). It also exhibits a high energy density of 4 J cm-3 which is 25 times higher than that of virgin PVDF. 98% of the electroactive γ-phase has been acheived by the incorporation of TiO2 NPs and the resulting PNC behaves like a super-toughened material due to a dramatic improvement (more than 80%) in the tensile strength. Owing to their electroactive nature and extraordinary mechanical properties, PNC films have a strong ability to fabricate the piezoelectric nanogenerators (PNGs) that have recently been an area of focus regarding mechanical energy harvesting. The feasibility of piezoelectric voltage generation from PNGs is demostrated under the rotating fan that also promises further utility such as rotational speed (RPM) determination.

Enhanced dielectric and energy storage performance of surface treated gallium ferrite/polyvinylidene fluoride nanocomposites

The ceramic–polymer nanocomposites composed of gallium ferrite (GFO) nanoparticles and employing sodium dodecylsulphate (SDS) as surfactant and polyvinylidene fluoride (PVDF) as matrix have been fabricated by solvent casting followed by hot-press technique. It was found that modified GFO nanoparticles favours nucleation and stabilization up to ∼84% electroactive phase (β- and γ-phase) in PVDF. Fourier transform infrared spectroscopy (FTIR) results revealed that the interfacial electrostatic interaction between nanoparticle surface charge and CH2/CF2 – molecular dipole of PVDF favoured nucleation of electroactive phase. Compared to the pristine PVDF, much higher dielectric constant (er ∼ 25 at 10 kHz frequency) with low loss factor (tan δ ∼ 0.02 at 10 kHz) was achieved in the composite film. In addition, the nanocomposite showed higher electrical energy density (Ud ∼ 3.88 mJ cm−3 at an electric field 6 kV mm−1) compared to pristine PVDF which determined their applicability as flexible energy density capacitor.