Summary Solution casting and ultrasonic‐assisted solution‐cast methods were used to create polymer nanocomposites films based on polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) filled with varying concentrations of BaTiO3 nanoparticles. The X‐ray diffraction (XRD), Fourier‐transform infrared (FT‐IR), transmission electron microscope, and differential scanning calorimetry (DSC) were used to study the properties of the produced polymer nanocomposite samples. The properties of PVA/PVP‐BaTiO3 nanocomposites, such as ac conductivity, dielectric constant, and dielectric loss, were investigated as a function of BaTiO3 concentration. XRD measurements demonstrate that the pure polymer blend is semi‐crystalline and that the crystallinity degree (Xc) of the doped PVA/PVP mix films is lower than that of the pure blend. Significant variations in the FT‐IR spectra demonstrate the interaction between the BaTiO3 ions and the PVA/PVP matrix. The DSC analysis demonstrates that the PVA/PVP has a single glass transition temperature (Tg), showing that the two polymers are miscible. In addition, when the amount of BaTiO3 NP's increased, the Tg of the nanocomposite films decreased. The AC conductivity spectra of all samples obey Jonscher's power law. For a better understanding of charge storage characteristics and conductivity relaxation, dielectric constant and loss investigations have been carried out. The PVA/PVP mixed with 1.5 wt% BaTiO3 nanofiller achieves a maximum ionic conductivity of ~8.57 × 10−5 S/cm. In this investigation, which introduced a novel approach, the complex permittivity revealed that the real part value of the dielectric constant (ε′) for all samples was much bigger than the imaginary part (ε″) value. These results are predicted to have a significant influence on a variety of applications, including polymer organic semiconductors, energy storage, polymer solar cells, and nanoelectronics.

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Electrocatalytic water splitting is a promising solution to resolve the global energy crisis. Tuning the morphology and particle size is a crucial aspect in designing a highly efficient nanomaterials-based electrocatalyst for water splitting. Herein, green synthesis of nickel oxide nanoparticles using phytochemicals from three different sources was employed to synthesize nickel oxide nanoparticles (NiOx NPs). Nickel (II) acetate tetrahydrate was reacted in presence of aloe vera leaves extract, papaya peel extract and dragon fruit peel extract, respectively, and the physicochemical properties of the biosynthesized NPs were compared to sodium hydroxide (NaOH)-mediated NiOx. Based on the average particle size calculation from Scherrer’s equation, using X-ray diffractograms and field-emission scanning electron microscope analysis revealed that all three biosynthesized NiOx NPs have smaller particle size than that synthesized using the base. Aloe-vera-mediated NiOx NPs exhibited the best electrocatalytic performance with an overpotential of 413 mV at 10 mA cm−2 and a Tafel slope of 95 mV dec−1. Electrochemical surface area (ECSA) measurement and electrochemical impedance spectroscopic analysis verified that the high surface area, efficient charge-transfer kinetics and higher conductivity of aloe-vera-mediated NiOx NPs contribute to its low overpotential values.

Half-metallic (HM) ferromagnets (HM-FMs) with large HM gap and high Curie temperature (TC) have a great importance in the field of spintronics. In this study, the geometric features, electronic structure and magnetism of two new double perovskites (DPs) represented by Rb2XMoO6 (X=Cr, Sc) were explored in bulk phase and (001) surface using quantum mechanical total energy calculations based on density functional theory (DFT). The results showed that Rb2CrMoO6 (RCMO) and Rb2ScMoO6 (RSMO) has an optimized lattice constant of 7.96Å and 8.26 Å, respectively, in the cubic phase (Fm-3m, #225). The cohesive energy Ecoh, formation energy Efor and elastic constants (mechanical) calculations proved that materials are stable. The magnetic properties explored in terms of ground state magnetic coupling, total magnetic moment (M) and atomic magnetic moment (m), exchange energy (J), and Curie temperature. It was found that both materials have ferromagnetic coupling in the ground state, with M of integer value of 8.0 µB (4.0 µB), J value of 47 meV(72 meV) and TC of 365 K (557 K) in Rb2CrMoO6 (Rb2ScMoO6). The electronic properties computed with electronic band structure and density of states demonstrated both DPs to be half-metal with HM gap of 1.61 eV (2.1 eV) in Rb2Cr-based (Rb2Sc-based) system. Finally the electronic and magnetic properties of (001) surfaces were investigated and compared with that of bulk phase. Interestingly, bulk HM property was retained in RSMO, but disappeared in RCMO due the emergence of defect states at Fermi level (EF). The reported results suggest that Rb-based DPs carry some fascinating properties for spin-based devices.

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In this article, the adsorption of NO x (x = 1, 2) gas molecules on the (001) surface of CoFeMnSi quaternary Heusler alloys has been investigated theoretically with density functional theory (DFT) calculations. The adsorption strength was estimated with adsorption energy (E a), magnitude of charge transfer (ΔQ), charge density difference (CDD), minimum distance between molecule and surface (d), and adsorption mechanism was analyzed with density of states. The results showed that unlike half-metallic nature of the bulk phase, the pristine CoFeMnSi(001) surface exhibited metallic character caused by the emergence of electronic states of the atoms in the top-most layer of the surface. It was found that both NO and NO2 molecules undergo chemical adsorption and strongly interact with the surface evidenced by the large value of E a and ΔQ. In particular, the NO x molecule dissociates into N and O atoms for some adsorption configurations. Bader charge analysis reveals that NO x molecules act as charge acceptors by drawing charge from the surface atoms through p–d hybridization. Such findings might be useful in the development of Heusler alloys based gas sensors.