Electron - Phonon interaction to tune pseudocapacitive properties of NiO

Electrochemical properties of two protype NiO nanostructures (coral and flake) were investigated at room temperature. Coral - like nanostructure possesses higher specific capacitance instead of having less surface area. In addition, significant differences have been noticed in the shape of the CV curves. Here, a mechanism of electron transfer across electrode - electrolyte has been proposed to understand these phenomenon on the basis of electron - phonon interaction, analysed by Raman and photoluminescence spectroscopies. Difference in electron - phonon interaction for the two synthesized structures is found to originate from morphological anisotropy that has been illustrated using fractional dimensional space approach

Hedgehog ZnO/Ag heterostructure: an environment-friendly rare earth free potential material for cold-white light emission with high quantum yield

Solid-state white light emission from environment-friendly, highly stable hedgehog ZnO/Ag heterostructure has been observed for first time from a combined effect of tunability of emission centers and charge transfer. The heterostructure has been synthesized via a facile low-temperature hydrothermal route and characterized using X-ray diffractometer, scanning electron microscope and transmission electron microscope. The interaction between ZnO and Ag can be confirmed from the appearance of few new multi-phonon Raman peaks. Steady-state photoluminescence spectrum reveals multiple emissions (413, 453, 546, 605 and 667 nm) from virgin hedgehog ZnO at an excitation wavelength of 325 nm. Tuneability of radiative and non-radiative emission of ZnO which is the primary mechanism for white light emission (CIE coordinate: 0.35, 0.32) has been briefly investigated by time-correlated single-photon spectroscopy. Biocompatible as well cost-effectivity depicts that the as-prepared heterostructure would be a promising solid-state white light-emitting phosphor material for long-term use

Non-inversion anisotropy energy in NiO coral structure: Asymmetric hysteresis loop at room temperature

Coral-like microstructure of NiO has been synthesized via a facile template free hydrothermal technique followed by calcination. Structure and morphology of the synthesized samples have been examined by x-ray diffractometer, field emission scanning electron microscope and transmission electron microscope. Positron annihilation spectroscopy reveals high porosity (37%) and cationic vacancies within the microstructures. Magnetic study illustrates spin-glass like behaviour and asymmetric hysteresis loop at room temperature. Later one is attributed to non-inversion symmetry of the anisotropic energy barrier, introduces by defect induced ferromagnetic domain within antiferromagnetic matrix of NiO. Numerical values of the anisotropy parameters have also been evaluated using law of approach method. The present study evidences that the microstructure could be helpful for developing magnetization based memory devices due to its high barrier height similar to 2.50 x 10(6) erg/cm(3). (c) 2018 Published by Elsevier B.V

Nonmonotonic magnetic field dependence of remanent ferroelectric polarization in reduced-graphene-oxide-BiFeO3_3 nanocomposite

In a nanocomposite of reduced graphene oxide (RGO) and BiFeO$_3$ (BFO), the remanent ferroelectric polarization is found to follow nonmonotonic magnetic field dependence at room temperature as the applied magnetic field is swept across 0-20 kOe on a pristine sample. The remanent ferroelectric polarization is determined both from direct electrical measurements on an assembly of nanoparticles and powder neutron diffraction patterns recorded under 0-20 kOe field. The nanosized ($\sim$20 nm) particles of BFO are anchored onto the graphene sheets of RGO via Fe-C bonds with concomitant rise in covalency in the Fe-O bonds. The field-dependent competition between the positive and negative magnetoelectric coupling arising from magnetostriction due to, respectively, interface and bulk magnetization appears to be giving rise to the observed nonmonotonic field dependence of polarization. The emergence of Fe-C bonds and consequent change in the magnetic and electronic structure of the interface region has influenced the coupling between ferroelectric and magnetic properties remarkably and thus creates a new way of tuning the magnetoelectric properties via reconstruction of interfaces in nanocomposites or heterostructures of graphene/single-phase-multiferroic systems.Comment: 10 pages, 12 figures, comments are welcom

Au nanoparticle-decorated aragonite microdumbbells for enhanced antibacterial and anticancer activities

The present work reports the very first hydrothermal synthesis of 100% triclinic phase pure aragonite (A1) with microdumbbell microstructural architecture and Au Nanoparticle-decorated (AuNP-decorated) aragonites (A2, A3 and A4) with spherical, pentagonal/hexagonal and agglomerated AuNP-decorated microdumbbells having triclinic aragonite phase as the major and cubic AuNPs as the minor phase. Even in dark the AuNP-decorated aragonites (especially A2) show efficacies as high 90% against gram-negative e.g., Pseudomonas putida (P. putida) bacteria. Further the AuNP-decorated aragonites (A3) show anti-biofilm capability of as high as about 20% against P. putida. Most importantly the AuNP-decorated aragonites (A3) offer anti-cancer efficacy of as high as 53% while those of A1, A2, and A4 are e.g., 26%, 46% and 37%, respectively. For the very first time, based on detailed investigations, the mechanisms behind such advance antibiofilm and anticancer activities are linked to the generation of excess labile toxic reactive oxygen species (ROS). Thus, these materials show enormous potential as futuristic, multi-functional biomaterials for anti-bacterial, anti-biofilm and anti-cancer applications

Nonmonotonic Magnetic Field Dependence of Remnant Ferroelectric Polarization in Reduced Graphene Oxide-BiFeO3 Nanocomposite

The thin-film heterostructures or nanocomposites exhibit vastly different properties from those observed in bulk systems. Herein, in a nanocomposite of reduced graphene oxide (RGO) and BiFeO3 (BFO), the remnant ferroelectric polarization is found to follow nonmonotonic magnetic field dependence at room temperature as the applied magnetic field is swept across 0-20 kOe on a pristine sample. Bulk BiFeO3, in contrast, exhibits monotonic suppression of polarization under magnetic field. The remanent ferroelectric polarization, in the present case, is determined, primarily, from powder neutron diffraction patterns recorded under 0-20 kOe field. The nanosized (approximate to 20 nm) particles of BFO are anchored onto the graphene sheets of RGO via Fe-C bonds with concomitant rise in covalency in the Fe-O bonds. Field-dependent competition between positive and negative magnetoelectric coupling arising from magnetostriction due to, respectively, interface and bulk magnetization appears to have given rise to the observed nonmonotonic field dependence of polarization. The emergence of Fe-C bonds and consequent change in the magnetic and electronic structure of the interface region have influenced coupling between ferroelectric and magnetic properties remarkably and thus creates a new way of tuning the magnetoelectric properties via reconstruction of interfaces in nanocomposites or heterostructures of graphene/single-phase-multiferroic systems