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Cr3+-doped ZnO (CZ) nanoparticles are prepared using hydrothermal and co-precipitation techniques. The desired crystallographic phase of the nanoparticles is confirmed using X-ray diffraction study. Rod-shaped and spherical morphologies of CZ nanoparticles prepared using hydrothermal and co-precipitation techniques were confirmed through FESEM observation. Each type of nanoparticle was taken separately in PVDF to understand the characteristic properties, such as dielectric, piezoelectric, and ferroelectric properties of the resultant CZ-PVDF nanocomposite films. All the nanocomposite films comprising rod-shaped or spherical CZ nanoparticles show butterfly loops with a low leakage current density of 10−5 A m−2 at a maximum electric field of 100 kV m−2 under J–E measurement. These findings suggest that the polarization property of CZ-PVDF nanocomposite films can be obtained at a high external electric field without causing electric breakdown in the samples. Dielectric permittivity as a function of temperature increases with an increase in the loading percentage of both rod-shaped or spherical CZ nanofillers in PVDF. Polarization response also improves with an increase in the loading percentage of CZ nanofillers in PVDF. In particular, the rod-shaped CZ nanofillers in PVDF with a higher loading percentage (CZHP2) result in a maximum polarization of (10 ± 0.29) × 10−4 μC cm−2, remanent polarization of (2 ± 0.04) × 10−4 μC cm−2, and coercive field of (10 ± 0.1) kV cm−1 at a maximum electric field of 50 kV cm−1. The CZHP2 nanocomposite film has a piezoelectric coefficient (d33) of (25 ± 0.24) pC N−1 and a power density of 1278.90 W m−3. These results indicate that the nanocomposite films have potential application in piezoelectric energy harvesters, offering a possible solution to the energy issue faced by modern society. [ABSTRACT FROM AUTHOR]

The present study covers the fabrication of flexible piezoelectric nanogenerators and their application towards sustainable power generation. The rod-like structure of erbium-doped ZnO (EZ) nanoparticles prepared by the hydrothermal synthesis route was successfully incorporated inside the polyvinylidene fluoride (PVDF) matrix using the solution casting method. Solution casting is an easy and cost-effective method for fabricating laminated, thin, flexible and lightweight EZ-PVDF nanocomposite films. The formation of the desired crystallographic phase of EZ-PVDF nanocomposite films and the presence of rod-like EZ nanoparticles inside the PVDF matrix were confirmed using X-ray diffraction and FESEM. The enhancement of the β-phase fraction of the EZ-PVDF nanocomposite films as compared to bare PVDF was estimated using FTIR spectroscopy. The presence of a ferroelectric phase in the EZ-PVDF nanocomposite films was found due to the formation of a large area of interfaces between the EZ nanoparticles and the PVDF matrix. The maximum polarizations of 0.00696 μC cm-2 and 0.00683 μC cm-2 for two samples (EZP1 and EZP2, respectively) were observed at an electric field of 1.25 kV cm-1. The piezoelectric voltages were observed at relatively low frequencies for both nanocomposite films. The maximum piezoelectric voltages of 18.9 V and 15.5 V were observed at a 1 Hz frequency for EZP1 and EZP2, respectively. The output piezoelectric current of 16.88 mA and the maximum power density of 7773.68 W m-3 for EZP1 ensure its potential as an efficient piezoelectric nanogenerator with greater efficiency than those reported previously in published articles. The change in the piezoelectric voltage response of the nanocomposite films as a function of mechanical movement of human external body parts renders them the most suitable candidate for human--machine interfacing (HMI) applications, such as bending sensors and human motion sensors. [ABSTRACT FROM AUTHOR]

In this report, for the first time, Co2U-type hexaferrite (Ba4Co2Fe36O60) nanomaterials have been considered along with their conjugation with a poly(vinylidene fluoride) (PVDF) matrix for the fabrication of heterostructure composite materials with superior electromagnetic interference shielding effectiveness (SE) that can produce better attenuation of microwave radiation. The high value of magnetizations of ∼7.21 and 10.63 emu/g is significant for the improvement of the shielding effectiveness due to absorption (SEA) of the composite materials. The unique combination of magnetic and dielectric responses of these Co2U-type hexaferrite nanomaterials helps to get significantly high total shielding effectiveness (SET) in their PVDF composite states within the frequency range of 8–18 GHz. A very high value of SET of approximately −83 dB at 14.2 GHz with >99.999 999% of attenuation of incident radiation has been observed for the Co2U-type hexaferrite–PVDF composite materials. The β-phase modified PVDF structure also plays the most important role to generate induced polarization inside the structure of composite materials. Also, this PVDF matrix provides the application friendly laminated structure of Co2U-type hexaferrite–PVDF composite materials. Structural, morphological, and chemical studies reveal the presence of the polycrystalline phase of Co2U-type hexaferrite and β-phase crystallization of polar PVDF in the multi-phase Co2U-type hexaferrite–PVDF composite materials. This study has helped us to understand the importance of magnetic Co2U-type hexaferrite nanomaterials for the fabrication of lightweight, large area, flexible, and thickness-controlled radar absorbing materials to combat against electromagnetic pollution. [ABSTRACT FROM AUTHOR]

The menace posed by antibiotic contamination to humanity has increased due to the absence of efficient antibiotic removal processes in the conventional waste water treatment methods from the hospitals, households, animal husbandry, and pharma industry. Importantly, only a few commercially available adsorbents are magnetic, porous, and have the ability to selectively bind and separate various classes of antibiotics from the slurries. Herein, we report the synthesis of a coral-like Co@Co3O4/C nanohybrid for the remediation of three different classes of antibiotics — quinolone, tetracycline, and sulphonamide. The coral like Co@Co3O4/C materials are synthesized via a facile room temperature wet chemical method followed by annealing in a controlled atmosphere. The materials demonstrate an attractive porous structure with an excellent surface-to-mass ratio of 554.8 m2 g−1 alongside superior magnetic responses. A time-varying adsorption study of aqueous nalidixic acid solution on Co@Co3O4/C nanohybrids indicates that these coral-like Co@Co3O4/C nanohybrids could achieve a high removal efficiency of 99.98% at pH 6 in 120 min. The adsorption kinetics data of Co@Co3O4/C nanohybrids follow a pseudo-second-order reaction kinetics suggesting a chemisorption effect. The adsorbent has also shown its merit in reusability for four adsorption-desorption cycles without showing significant change in the removal efficiency. More in-depth studies validate that the excellent adsorption capability of Co@Co3O4/C adsorbent attributing to the electrostatic and π–π interaction between adsorbent and various antibiotics. Concisely, the adsorbent manifests the potential for the removal of a wide range of antibiotics from the water alongside showing their utility in the hassle-free magnetic separation. [ABSTRACT FROM AUTHOR]

In search of a new radar absorbing material for microwave applications, the nanoparticles of Ni0.40Zn0.40Cu0.20Fe2O4 (NZCF) are successfully incorporated in the matrix of poly(vinylidene fluoride) (PVDF), and this NZCF-PVDF nanocomposite system has evolved as the potential one for absorbing radiations in the microwave/GHz frequency range. The enhancement of electroactive β-phase of PVDF has been observed in the NZCF-PVDF nanocomposite system due to the formation of NZCF-PVDF interfaces. Also, the magnetic dipoles of ferrite nanoparticles are present in the same resultant nanocomposite system. Both these factors play a significant role in the interaction of microwave radiation with the medium of the nanocomposite system. The optimization of wave matter interaction leads to the superior reflection loss property of the NZCF-PVDF nanocomposite system. The mutual contributions of both magnetic nano-fillers and electroactive PVDF polymers make this NZCF-PVDF nanocomposite system a unique metamaterial for enhanced microwave absorption. Many articles have been published on polymer-ferrite systems but in true sense the involvement of NZCF-PVDF interfaces as active centres during wave matter interactions has not been considered by anyone else. Reflection loss property of all the NZCF-PVDF nanocomposite films has been observed, and a maximum of −49.7 dB at 13.2 GHz is obtained for 10 wt. % of NZCF loaded PVDF nanocomposite films. This is the highest reflection loss ever found in these types of polymer based metamaterials. Also, the high reflection loss in NZCF-PVDF nanocomposite films (X and Ku bands) makes it the most suitable one for the applications in the area of microwave devices. [ABSTRACT FROM AUTHOR]

The influence of the hydrothermal synthesis route on the grain morphology and thereby the modulation of dielectric response of undoped and Cr3+ ion doped semiconducting ZnO nanoparticles is investigated in this report. The X-ray diffraction study reveals that all the samples are in a polycrystalline single phase of a hexagonal wurtzite structure of ZnO. The field emission scanning electron microscopy study reveals the rod like structure of all the samples. The formation of synthesis route dependent morphology and the morphology dependent physical property of all the samples are the characteristic features of the present work and to date it has not been considered as the specific tool of dielectric property modulation by anyone else. The ultraviolet-visible measurement signifies the superior control over the charge density of the host semiconducting material due to the presence of Cr3+ ions in the structure of ZnO. In the photoluminescence measurement, no significant peak has been observed in the visible region. The frequency and temperature dependent dielectric constants of all the samples were investigated. The consequences of the dielectric measurement suggest that the hydrothermal synthesis route influences the growth mechanism of the semiconducting nanoparticles mostly towards the rod like structure and the doping element influences the charge density, nature of defects, and the defect densities inside the structure of ZnO nanomaterials. All these factors together make the semiconducting ZnO nanomaterials more effective for tailor made applications in magneto-dielectric devices. [ABSTRACT FROM AUTHOR]

The investigations of the structural, optical, dielectric and ac electrical properties of Gd 0.05 Mn x Zn 0.95-x O (weight percentage x = 0.03, 0.05 and 0.07 respectively) nanoparticles have been done in this report. The nanoparticles were synthesized by hydrothermal method. The X-ray diffraction analysis reveals the presence of hexagonal wurtzite crystalline structure for all the undoped and doped samples. Photoluminescence emission spectra for the entire samples confirm the presence of various defect centers inside the doped ZnO wurtzite nanostructure. Dielectric measurements show dispersion behavior for all the samples and it was found to increase with the doping concentration. The dielectric behavior has been explained on the basis of Maxwell-Wagner-Sillars polarization phenomenon. High value of dielectric constant (1.2 × 10 6 ) was observed due to the presence of grain boundary defects and oxygen vacancies. Incorporation of Gd and Mn inside the ZnO wurtzite structure can causes more grain boundary defects which can enhance polarization. The ac conductivity of entire samples was temperature and frequency dependent. The ac conductivity was governed by universal ac power law σ ac = Bω n according to the Jonscher model. Variation of frequency exponent “n” from 0.2841 to 0.0484 suggests that diffusion controlled charge carrier hopping mechanism is also involves in the conduction phenomenon. [ABSTRACT FROM AUTHOR]