Arpan Kool

The role of cerium(III)/yttrium(III) nitrate hexahydrate salts on electroactive β phase nucleation and dielectric properties of poly(vinylidene fluoride) thin films

Electroactive poly(vinylidene fluoride) (PVDF) thin films modified with Ce(NO3)3·6H2O and Y(NO3)3·6H2O (1–30 mass%) have been prepared via a simple solution casting method. The thermal stability and microstructures of the films were investigated using thermal gravimetric analysis techniques and field emission electron microscopy respectively. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry confirmed the nucleation of the electroactive β phase in the composite films. Strong interfacial interaction i.e. ion dipole interaction via formation of hydrogen bonds between the water molecules of the salts and the polar –CF2 dipoles of the polymer chains resulted in improved electroactive β phase nucleation and a large dielectric constant in PVDF films.

Improvement of electroactive β phase nucleation and dielectric properties of WO3·H2O nanoparticle loaded poly(vinylidene fluoride) thin films

Tungsten oxide hydrate (WO3·H2O) nanoparticles (NPs) have been prepared by simple hydrazine hydrate reduction. X-ray diffraction, UV-Visible spectroscopy and field emission electron scanning microscopy confirm the formation of phase pure orthorhombic WO3·H2O NPs. Thereafter, poly(vinylidene fluoride) (PVDF) thin films doped with different amounts of WO3·H2O NPs (1–15 mass%) have been prepared via a simple solution-casting method to verify the role of the NPs on the enhancement of electroactive β phase crystallization and dielectric properties of WO3·H2O NP–PVDF thin films. The interface between the NPs and the polymer matrix takes a vital role in improving β phase nucleation and dielectric properties of the WO3·H2O NP modified PVDF thin films. Strong electrostatic or ion–dipole interaction between the negatively charged NP surfaces and –CH2 dipoles of the polymer matrix at the interface effectively improves the electroactive β phase nucleation and dielectric properties of the nanocomposite thin films.

Sol–gel synthesis of transition-metal ion conjugated alumina-rich mullite nanocomposites with potential mechanical, dielectric and photoluminescence properties

Nanocrystalline mullite have been synthesized from non-stoichiometric alkoxide precursors via sol–gel route with Co2+, Ni2+ and Cu2+ as dopant metal ions. Transition-metal aluminate spinel phases, formed from the reaction between dopant metal ions and dissolved alumina species, introduced prominent colors to the composites after sintering. Interesting colors combined with suitable densification lead these composites to have potential use as ceramic pigments. A comparative Vickers and Knoop hardness have been evaluated in terms of dislocation movement along grain boundaries with highest hardness and Young’s modulus values of ∼8.7 GPa and ∼207 GPa for copper and cobalt incorporated mullite, respectively. Greater porosity of pure mullite results in an unconventionally high dielectric constant of ∼91 whereas larger interfacial polarization is responsible for the varying dielectric response of transition-metal incorporated mullite composites. Formation of oxygen like defects in the composites cause prominent PL bands with highest PL intensity for dopant cobalt ions in mullite matrix.

Er3+/Fe3+ Stimulated Electroactive, Visible Light Emitting, and High Dielectric Flexible PVDF Film Based Piezoelectric Nanogenerators: A Simple and Superior Self-Powered Energy Harvester with Remarkable Power Density

The design of an energy-harvesting unit with superior output characteristics, i.e., high power density, is a great technological challenge in the present time. Here, simple, lightweight, flexible, and cost-effective piezoelectric nanogenerators (PENGs) have been fabricated by integrating the aluminum electrodes onto Er3+/Fe3+ stimulated electroactive, visible-light-emitting, and large dielectric PVDF films in which ErCl3·6H2O and Fe(NO3)3·9H2O act as the catalytic agents for electroactive β polymorph nucleation and the enhancement of dielectric properties. The developed PENGs exhibit excellent energy-harvesting performance with very high power density and very fast charging ability compared with the previously reported PVDF-assisted prototype nanogenerators. The PENGs lead to very large power density (∼160 and ∼55.34 mW cm-3) under periodic finger imparting for Er3+- and Fe3+-stimulated PVDF-film-based energy-harvester units, respectively. The fabricated self-powered PENG is also able to light up 54 commercially available light-emitting diodes.

Improving the thermal stability, electroactive β phase crystallization and dielectric constant of NiO nanoparticle/C–NiO nanocomposite embedded flexible poly(vinylidene fluoride) thin films

Using a simple chemical precipitation process followed by sintering at 400 °C, NiO nanoparticles (NPs) and C–NiO nanocomposites (NCs) have been synthesized and characterized by X-ray diffraction, UV-visible spectroscopy, zeta potential measurement, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Then, NiO NP or C–NiO NC loaded PVDF thin films were fabricated via a simple solvent casting or solution casting method. Thermogravimetric analysis confirmed good thermal stability of the nanocomposite films. Strong ion–dipole interaction between the negative surfaces of NiO NPs or C–NiO NCs and –CH2 dipoles of polymer chains leads to the formation of a long stabilized TTTT conformation, i.e. formation of large number of electroactive β polymorphs in the modified PVDF thin films. Detailed study of the dependency of the dielectric properties on filler content (NiO NPs/C–NiO NCs) and frequency illustrates significant increase in the dielectric constant in the three phase C–NiO NCs–PVDF system than in the two phase NiO NPs–PVDF system. The dielectric constant is found to be as large as 317.4 at 20 Hz with a relatively low tangent loss value, and good flexibility when 20 mass% C–NiO NCs is incorporated in the PVDF matrix. These results have been explained in terms of Maxwell–Wagner–Sillars interfacial polarization at the NiO NPs/C–NiO NCs and insulating polymer matrix interface, evolution of a conductive network and formation of a microcapacitive structure in the NiO NPs or C–NiO NCs modified PVDF thin films.

Tunable photoluminescence emissions and large dielectric constant of the electroactive poly(vinylidene fluoride–hexafluoropropylene) thin films modified with SnO2 nanoparticles

In the present study, SnO2 nanoparticles (NPs) have been synthesized hydrothermally at 100 °C and 150 °C. The NPs have been characterized by X-ray diffraction (XRD), UV-visible spectroscopy and field emission scanning electron microscopy (FESEM). Thereafter, poly(vinylidene fluoride–hexafluoropropylene) (PVDF–HFP) with different contents (1–15 wt%) of SnO2 NPs has been synthesized by a simple solution-casting method. An electroactive β-phase formation mechanism in the NP-incorporated PVDF–HFP thin films is confirmed by XRD, Fourier transform infrared spectroscopy and differential scanning calorimetry. FESEM images show interfacial interaction in the thin films between the polymer matrix and the NPs. Maximum β-phase nucleation of ∼74% has been reached by 10 wt% addition of SnO2 NPs synthesized hydrothermally at 100 °C. The photoluminescence emission spectra show two UV and visible emissions at two excitation wavelengths. Uniform distribution of the NPs in the polymer matrix leads to large dielectric constant ∼2578.44 at 20 Hz due to addition of 10 wt% SnO2 NPs (100SO) in PVDF–HFP matrix. The large increase in dielectric constant has been successfully explained in terms of MWS polarization effect and percolation theory.

Electroactive and High Dielectric Folic Acid/PVDF Composite Film Rooted Simplistic Organic Photovoltaic Self-Charging Energy Storage Cell with Superior Energy Density and Storage Capability

Herein we report a simplistic prototype approach to develop an organic photovoltaic self-charging energy storage cell (OPSESC) rooted with biopolymer folic acid (FA) modified high dielectric and electroactive β crystal enriched poly(vinylidene fluoride) (PVDF) composite (PFA) thin film. Comprehensive and exhaustive characterizations of the synthesized PFA composite films validate the proper formation of β-polymorphs in PVDF. Significant improvements of both β-phase crystallization (F(β) ≈ 71.4%) and dielectric constant (ε ≈ 218 at 20 Hz for PFA of 7.5 mass %) are the twosome realizations of our current study. Enhancement of β-phase nucleation in the composites can be thought as a contribution of the strong interaction of the FA particles with the PVDF chains. Maxwell-Wagner-Sillars (MWS) interfacial polarization approves the establishment of thermally stable high dielectric values measured over a wide temperature spectrum. The optimized high dielectric and electroactive films are further employed as an active energy storage material in designing our device named as OPSESC. Self-charging under visible light irradiation without an external biasing electrical field and simultaneous remarkable self-storage of photogenerated electrical energy are the two foremost aptitudes and the spotlight of our present investigation. Our as fabricated device delivers an impressively high energy density of 7.84 mWh/g and an excellent specific capacitance of 61 F/g which is superior relative to the other photon induced two electrode organic self-charging energy storage devices reported so far. Our device also proves the realistic utility with good recycling capability by facilitating commercially available light emitting diode.

In situ synthesis of environmentally benign montmorillonite supported composites of Au/Ag nanoparticles and their catalytic activity in the reduction of p -nitrophenol

In the present work, composites of montmorillonite clay supported silver and gold nanoparticles were synthesized by in situ chemical reduction method and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), UV-vis spectroscopy and Transmission Electron Microscopy (TEM). The clay–nanoparticle composites were synthesized at two different temperatures (25 °C and 75 °C) where nanoparticle size was found to depend on synthesis temperature. The distribution of the catalytic nanoparticles was uniform in the clay matrix with sizes in the range of 20–45 nm (at 25 °C) and 5–15 nm (at 75 °C), respectively. Catalytic activity of the clay–nanoparticle composites were monitored by UV-visible spectroscopy using p-nitrophenol and NaBH4 as model reactants. The best catalytic efficiency was observed in the case of silver–clay nanocomposites with a rate constant of 5.6 × 10−3 s−1.

Effect of vanadic anhydride and copper oxide on the development of hard porcelain composite and its antibacterial activity

Abstract A mullite-reinforced porcelain composite with antibacterial properties has been developed using transition metal oxides by solid state sintering. The composite has been characterized in terms of mullite content, hardness, color and antibacterial properties. The physico-chemical properties of the porcelain were substantially increased in the presence of V2O5 and CuO. Well-crystallized needle shaped mullite of average length ∼ 3 μm was observed in the porcelain body at 1300 °C and 1500 °C after the addition of V2O5 and CuO. Vickers hardness of the composite increased 4.2 times for 2% V2O5 at 1500 °C. The porcelain composites showed satisfactory antibacterial activity on gram negative bacteria Escherichia coli with mortality rates of 45% and 22% for V2O5 and CuO doped porcelain respectively.

An efficient three-component synthesis of coumarin-3-carbamides by use of Ni–NiO nanoparticles as magnetically separable catalyst

An efficient and ecofriendly synthesis of coumarin-3-carbamides, a class of compounds known for their remarkable biological activities and fluorescent properties, has been developed by a three-component reaction of 2-hydroxybenzaldehydes, aliphatic primary/secondary amines and diethyl malonate using Ni–NiO nanoparticles as catalyst in the green solvent ethanol. The method is compatible with various functional groups and moieties.