Samiran Garain

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.

DNA-Assisted β-phase Nucleation and Alignment of Molecular Dipoles in PVDF Film: A Realization of Self-Poled Bioinspired Flexible Polymer Nanogenerator for Portable Electronic Devices.

A flexible nanogenerator (NG) is fabricated with a poly(vinylidene fluoride) (PVDF) film, where deoxyribonucleic acid (DNA) is the agent for the electroactive β-phase nucleation. Denatured DNA is co-operating to align the molecular -CH2/-CF2 dipoles of PVDF causing piezoelectricity without electrical poling. The NG is capable of harvesting energy from a variety of easily accessible mechanical stress such as human touch, machine vibration, football juggling, and walking. The NG exhibits high piezoelectric energy conversion efficiency facilitating the instant turn-on of several green or blue light-emitting diodes. The generated energy can be used to charge capacitors providing a wide scope for the design of self-powered portable devices.

Design of In Situ Poled Ce3+-Doped Electrospun PVDF/Graphene Composite Nanofibers for Fabrication of Nanopressure Sensor and Ultrasensitive Acoustic Nanogenerator

We report an efficient, low-cost in situ poled fabrication strategy to construct a large area, highly sensitive, flexible pressure sensor by electrospun Ce(3+) doped PVDF/graphene composite nanofibers. The entire device fabrication process is scalable and enabling to large-area integration. It can able to detect imparting pressure as low as 2 Pa with high level of sensitivity. Furthermore, Ce(3+)-doped PVDF/graphene nanofiber based ultrasensitive pressure sensors can also be used as an effective nanogenerator as it generating an output voltage of 11 V with a current density ∼6 nA/cm(2) upon repetitive application of mechanical stress that could lit up 10 blue light emitting diodes (LEDs) instantaneously. Furthermore, to use it in environmental random vibrations (such as wind flow, water fall, transportation of vehicles, etc.), nanogenerator is integrated with musical vibration that exhibits to power up three blue LEDs instantly that promises as an ultrasensitive acoustic nanogenerator (ANG). The superior sensing properties in conjunction with mechanical flexibility, integrability, and robustness of nanofibers enabled real-time monitoring of sound waves as well as detection of different type of musical vibrations. Thus, ANG promises to use as an ultrasensitive pressure sensor, mechanical energy harvester, and effective power source for portable electronic and wearable devices.

An Effective Electrical Throughput from PANI Supplement ZnS Nanorods and PDMS-Based Flexible Piezoelectric Nanogenerator for Power up Portable Electronic Devices: An Alternative of MWCNT Filler.

We demonstrate the requirement of electrical poling can be avoided in flexible piezoelectric nanogenerators (FPNGs) made of low-temperature hydrothermally grown wurtzite zinc sulfide nanorods (ZnS-NRs) blended with polydimethylsiloxane (PDMS). It has been found that conductive fillers, such as polyaniline (PANI) and multiwall carbon nanotubes (MWCNTs), can subsequently improve the overall performance of FPNG. A large electrical throughput (open circuit voltage ∼35 V with power density ∼2.43 μW/cm(3)) from PANI supplement added nanogenerator (PZP-FPNG) indicates that it is an effective means to replace the MWCNTs filler. The time constant (τ) estimated from the transient response of the capacitor charging curves signifying that the FPNGs are very much capable to charge the capacitors in very short time span (e.g., 3 V is accomplished in 50 s) and thus expected to be perfectly suitable in portable, wearable and flexible electronics devices. We demonstrate that FPNG can instantly lit up several commercial Light Emitting Diodes (LEDs) (15 red, 25 green, and 55 blue, individually) and power up several portable electronic gadgets, for example, wrist watch, calculator, and LCD screen. Thus, a realization of potential use of PANI in low-temperature-synthesized ZnS-NRs comprising piezoelectric based nanogenerator fabrication is experimentally verified so as to acquire a potential impact in sustainable energy applications. Beside this, wireless piezoelectric signal detection possibility is also worked out where a concept of self-powered smart sensor is introduced.

Electro-active phase formation in PVDF–BiVO4 flexible nanocomposite films for high energy density storage application

In this work we report on the preparation of polymer nanocomposite (PNC) films, consisting of poly(vinylidene fluoride) and bismuth vanadium oxide nanoparticles (BiVO4-NPs), and its electroactive phase (β- and γ-phase) formation. It was found that BiVO4-NPs can yield up to 98% of the electroactive phases in PVDF. Fourier transform infrared spectroscopy (FTIR) results reveal that electrostatic interactions are present at the interface between surface charges of BiVO4-NPs and –CH2/CF2– molecular dipoles of PVDF favoring and stabilizing the electroactive phases. The electrostatic interaction is further confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Compared to the neat PVDF film, a significantly increased dielectric constant (e ∼ 44) and a low loss factor (tan δ ∼ 0.02) were observed in the PNC films. In addition, PNC films exhibit a high electrical energy density up to 11 J cm−3 with a breakdown electric field higher than 400 MV m−1. Furthermore, a dramatic improvement of the toughness (460%) was also noticed for the PNC films. These results underline the high potential of such films for their use as flexible high energy density capacitors and flexible piezoelectric based power sources as well.

Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction

Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce(III)(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d → 4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [Ce(III)(DMF) (HSO4)3] complex. A stacking electrode was designed where self-assembled l-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The resulting electrode, i.e., [Ce(III)(DMF) (HSO4)3]-l-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈ 0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light.

P(VDF-HFP)/Cerium composite films with improved dielectric properties for energy storage applications

In this work we report on the preparation of polymer composite films based on P(VDF-HFP) Ce-salt and its electroactive phase (β-and γ-phase) phase formation. It is found that a desirable amount of Ce-salt can yield more than 99 % of the electroactive phases in co-polymer matrix. FTIR results reveal that electrostatic interaction is present at the interface between surface charges of Ce-salt filler and –CH2/CF2-molecular dipoles of P(VDF-HFP) and the presence of H-bonding interaction helps to stabilize the electroactive phases and enhance the dielectric properties which is very promising for developing energy storage technologies flexible piezoelectric based power source as well.

In situ synthesis of bismuth oxide nanorods and fabrication of self-poled PVDF nanogenerator for mechanical energy harvesting application

A self-poled piezoelectric nanogenarator (NGs) based on Bismuth Oxide (Bi2O3) nanorod (Bi-NR) doped PVDF is demonstrated. The effect of in-situ prepared Bi-NRs incorporation in PVDF matrix is discussed. The yield of electroactive β phase nucleation in the Bi-NR doped films was calculated by deconvolution of XRD and FTIR results. The Bi-NR films were found to be B dominated. Without any electrical poling treatment, the nanogenerators constructed out of the films showed an output voltage of 3V and short circuit current of 2 µA under repeated human finger impact. The NGs are able to charge capacitor, which can be utilized for powering various portable devices.A self-poled piezoelectric nanogenarator (NGs) based on Bismuth Oxide (Bi2O3) nanorod (Bi-NR) doped PVDF is demonstrated. The effect of in-situ prepared Bi-NRs incorporation in PVDF matrix is discussed. The yield of electroactive β phase nucleation in the Bi-NR doped films was calculated by deconvolution of XRD and FTIR results. The Bi-NR films were found to be B dominated. Without any electrical poling treatment, the nanogenerators constructed out of the films showed an output voltage of 3V and short circuit current of 2 µA under repeated human finger impact. The NGs are able to charge capacitor, which can be utilized for powering various portable devices.