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In this study, pure ZnO and iron (Fe) and cobalt (Co) co-doped ZnO nanoparticles were synthesized by varying Fe and Co concentrations using the co-precipitation method. The physical properties of as-prepared samples were investigated through XRD, FTIR, SEM, and UV–vis spectroscopy. X-ray diffraction confirmed the strong influence of Fe and Co ions on structural parameters without disturbing the basic ZnO hexagonal structure. The microstructural study was executed by using the Scherrer, W–H, and SSP methods. FTIR confirmed the presence of Zn–O, and Zn–M–O (M = Fe, Co) vibrational modes, which further confirmed the successful incorporation of dopants ions. The energy bandgap (E g) extracted from UV–vis spectra has shown red-shift (3.37–2.7 eV) for decreasing Fe contents, whereas blue-shift (3.37–3.39 eV) for increasing Co concentration. SEM was used to investigate surface morphology, which represents the high rate of agglomeration. The photocatalytic test was performed on grown samples against various dyes and also observed the effects of varying concentrations of Fe and Co ions. The maximum degradation efficiency (98.8%) at 6%Fe and 4%Co under direct sunlight in 60 min against methylene blue (MB) was achieved. The photocatalytic activity of optimized concentration (6%Fe and 4%Co) was further tested against cresol red (CR), methyl orange (MO), safranin-O (SO), rhodamine-B (RhB), and methyl red (MR) dyes. The maximum degradation efficiency against MR dye (96.0%) was observed. The antibacterial test against Staphylococcus aureus and Klebsiella pneumoniae bacterial strains have shown that co-doped ZnO nanoparticles have a higher activity as compared to pristine ZnO, and furthermore, the sample with 6%Fe and 4%Co concentration exposed the highest antibacterial actively for both bacterial strains. [ABSTRACT FROM AUTHOR]

Bi–Cr-substituted Y-type hexa-ferrites were prepared via a micro-emulsion method. Formation of the hexagonal phase was confirmed by X-ray diffraction (XRD) analysis. The size of the crystallites of all the samples was in the range 31.58–37.67 nm and their Fourier transform infrared (FTIR) spectroscopy bands were observed in the range ~ 450–650 cm-1. These bands indicated successful incorporation of Bi–Cr in the Y-type hexagonal ferrites. The existence of metal-oxygen bands at the tetrahedral and octahedral sites confirmed that all the prepared samples exhibit Y-type hexagonal ferrites structures. The magnetic parameters such as saturation magnetization, retentivity and coercivity revealed significant variations with the increase of Bi–Cr contents. Frequency and composition dependent variations in the dielectric constant (ε′), dielectric loss (ε"), tan loss, and other parameters were observed, for example the value of ε′ decreased as the Bi–Cr content increased. These optimised results are highly desirable for the application of these nanosized hard ferrites in various microwave devices [ABSTRACT FROM AUTHOR]

Due to energy crises and environmental pollution worldwide, researchers have sought efficient electrocatalysts for oxygen evolution reaction (OER) and photocatalysts to eliminate organic pollutants. In the present work, we have synthesized a fullerene-C 60 -based CeO 2 @C 60 core-shell hybrid and characterized it with various state-of-art techniques to explore its OER performance and photocatalytic properties under natural sunlight. TEM nano-graphs and EDX color mapping exhibited the uniform covering of C 60 over CeO 2 forming a core-shell structure with a particle size of 54 nm. The XPS results demonstrate the coexistence of Ce3+ and Ce4+ oxidation states, resulting in the formation of rich oxygen vacancy defects, which induced the efficient charge transformation from CeO 2 to C 60 , enhancing the photocatalytic activity and promoting the OER reaction. The electrochemical measurements revealed a lower overpotential (312 mV) and small Tafel slope (54 mV/dec) at 10 mA/cm2 current density of CeO 2 @C 60 core-shell hybrid than pure CeO 2. Further, the hybrid is stable up to 2000th cycles, and the chronoamperometry test showed that it remains stable for 45 hr without degrading in 1 M KOH solution. The photocatalytic activity under natural sunlight irradiations showed that the CeO 2 @C 60 core-shell hybrid completely degraded P-nitroaniline (P-Nitro) organic pollutant after 75 min, with outstanding recyclability up to the 7th cycle of use. Furthermore, the present work explores the tremendous potential of C 60 and rare earth metal oxide-based hybrid catalysts having exceptional stability toward photocatalysis and electrochemical water splitting. [Display omitted] [ABSTRACT FROM AUTHOR]

Dual metal doping is a state-of-the-art technique for improving the electrocatalytic characteristics for oxygen evolution reaction (OER) and enhancement of the antibacterial activity of the material. Series of rare earth dual metal-doped Pr 2 O 3 electrocatalysts (Pr 2 CeMO 3 , M = Sm, Yb, Er) were successfully fabricated by employing sol-gel treatment. The antimicrobial and electrochemical applications of grown products were studied along with physical properties using advanced techniques such as FESEM, EDX, XRD, FTIR, IV, CV, LSV, EIS, and ECSA. The prepared products retain the monoclinic Pr 2 O 3 structure with the successful doping of rare-earth elements. From the FESEM analysis, grown products have the grainy conglomerate shape, icy monoclinic boxes, irregular lamellar shaped, and well-crystallized grains with the plate-like morphology. EDX has confirmed the presence of metal elements Pr, Ce, Sm, Yb, and Er in grown samples. The electrochemical measurements exhibited the enhancement by dual-doping, and Pr 2 CeSmO 3 has an extraordinarily low overpotential of 189 mV to reach 10 mAcm−2 density and lower Tafel slope (75 mV/dec) for oxygen evolution reaction (OER) in 1.0 M KOH electrolyte. Furthermore, the electrocatalytic efficiency of Pr 2 CeSmO 3 electrocatalyst for OER is extremely long-lasting for (>16 h). The antibacterial test showed that all grown single and dual-doped nanostructures have good antibacterial performance, but Pr 2 CeSmO 3 exhibits strong inhibition activity towards E. coli , K. pneumoniae , S. aureus , and P. vulgaris bacterial strains with maximum inhibition zone diameter 30, 32, 35, and 31 mm, respectively. This low-cost method for the production of rare earth dual metal-doped materials holds a lot of potential for making efficient catalysts, electrochemical energy-conversion devices, and economical antibacterial agents. [ABSTRACT FROM AUTHOR]

Metal oxide nanoparticles and their composites with conducting polymers, specifically Polyaniline (PANI) were utilized for fabricating nanoscale supercapacitor (SC) electrode materials. In the present study, we have synthesized pristine Pr 2 O 3 , NiO, Co 3 O 4 nanoparticles, binary PANI-Pr 2 O 3 , PANI-NiO, PANI-Co 3 O 4 , ternary Pr 2 O 3 –NiO–Co 3 O 4 , and quaternary PANI-Pr 2 O 3 –NiO–Co 3 O 4 spherical core-shell nanocomposite using co-precipitation and ultra-sonication methods. The grown samples were characterized with different analytical techniques. The XRD pattern revealed that the as-synthesized products were crystalline with Pr 2 O 3 hexagonal phase, NiO cubic phase, and Co 3 O 4 cubic phase in pure and nanocomposites. The Williamson-Hall, Scherrer, and size-strain plot methods were employed to study the crystalline development and contribution of micro-strain. FTIR pattern exhibited the metal-oxygen and PANI bond vibrations. FE-SEM images shown the spherical core-shell shape morphology of quaternary nanocomposite. EDX evident the presence of praseodymium, cobalt, and nickel in synthesized samples. UV–vis spectroscopy confirmed the absorption in the visible region. The IV graphs showed a higher conductivity of quaternary nanocomposite. The cyclic voltammetry results revealed that the quaternary nanocomposite has a higher specific capacitance 500 Fg-1 as compared to binary nanocomposites 134 F g−1 (PANI-Pr 2 O 3), 143 F g−1 (PANI-Co 3 O 4), 256 F g−1 (PANI-NiO), and PANI (90.8 F g−1) at a scan rate of 5 m Vs−1. The GCD results also showed that the quaternary nanocomposite has a higher specific capacitance of 905 F g−1 at current density 1 A g−1 with maximum energy density and power density of 87.99 kWhkg-1 and 2.6 k W kg−1 , respectively. The EIS curve also confirmed that the quaternary nanocomposite has a lower polarization resistance (R p) and solution resistance (R s). The higher capacitance of quaternary nanocomposite can facilitate ion transfer, and the formation of its core-shell structure flourish to enhance surface-dependent electrochemical properties. Furthermore, this study gives a novel research idea to manufacture electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Novel Zn 0 · 95 Mn 0 · 05 O and Zn 0 · 9 Mn 0.05 M 0.05 O (M = Al, Bi, Sr, Ag) nanocrystals were prepared via the co-precipitation technique. The X-ray diffraction pattern confirmed the substitution of Mn, Al, Bi, Sr, and Ag dopants without altering the basic ZnO structure. The microstructural study was performed by employing the Scherrer plot, Williamson-Hall, and SSP methods. The energy bandgap calculated from UV–vis spectra using different methods observed red-shifted by co-doping. The other optical parameters were also studied and discussed in detail. The FTIR spectra confirmed the presence of Zn–O, and Zn-M–O vibrational modes. Raman spectra demonstrated the presence of ZnO phonon modes, and the Raman shift exhibited the structural defects induced by dopants. The PL spectra showed strong NBE and DLE in the UV and visible region due to extrinsic defects. The IV measurements exhibited the enhancement in the electrical conductivity of ZnO by co-doping. The photocatalytic activity was performed under direct sunlight for methyl orange and methylene blue dyes, and the enhanced degradation efficiency was achieved by co-doping. Furthermore, this article enhances the understanding of tuning the physical properties of ZnO by co-doping and introduces a new class of sunlight-driven photocatalysts. [ABSTRACT FROM AUTHOR]

Erbium oxide due to its large polarizability and wide bandgap possesses superior dielectric properties and low leakage current. To study the effect of annealing environments on dielectric properties of erbium oxide, it was annealed under argon and air environments. Complex impedance analysis was performed to investigate dielectric properties, relaxation and conduction processes of the annealed samples. The decrease in grain size and increase in surface area, due to annealing in argon environment, resulted in over 2-fold increase in dielectric constant as compared to conventionally used SiO 2 (Effendy et al., 2017) [1]. The annealing in reducing environment also happened to widen the bandgap energy of erbium oxide. Annealing of erbium oxide in inert environment was proved to be better for the enhancement of dielectric properties, owing to creation of smaller grains with larger grain boundaries. [ABSTRACT FROM AUTHOR]

In this study, the micro-emulsion approach was adopted to fabricate rare earth (Nd) and transition metal (Cu) co-doped barium hexaferrite (Ba 1-x Nd x Fe 12-y Cu y O 19) nanoparticles (NPs). The fabricated co-doped and undoped materials were characterized by FTIR, XRD, and SEM techniques for structural and morphological investigation. Structural studies such as XRD and FTIR confirmed Nd and Cu doping at the tetrahedral and octahedral sites of barium hexaferrite, respectively. The SEM analysis made sure that the materials were successfully produced at the nanoscale. Dielectric measurements revealed that the dielectric constant and AC conductivity values of the co-doped sample were higher than those of the undoped sample. The VSM study confirms the improved magnetic properties of the sample after co-doping that facilitates its separation and reuse after photocatalytic experiments. The co-doped and undoped sample's photocatalytic activities (PCA) were explored by comparing their Methyl Green (MG) dye degradation efficiencies. The results revealed that the co-doped barium hexaferrite sample degraded almost 92.6% of the MG dye, while the undoped sample degraded just 37.4%. The higher PCA of the co-doped sample is credited to its structural defects, which adjust the band interval to increase electrical conductivity. In addition, the co-doped sample lost only 2% photocatalytic efficiency after five successive cycles, demonstrating its potential for reuse. Application studies have clearly shown that our Nd-Cu co-doped barium hexaferrite sample has a great potential for practical application to remove toxic dyes from the environment. [Display omitted] [ABSTRACT FROM AUTHOR]

Novel photocatalytic and antibacterial material Zn 0.9 Ce 0.05 M 0.05 O (M = Er, Y, V) nanocrystals were synthesized via a facile co-precipitation technique and characterized by different analytical techniques. XRD confirmed the incorporation of Ce, Er, Y, and V, that without modifying the basic ZnO hexagonal wurtzite structure affects strongly structural properties. The Scherrer, W–H, and SSP methods were used to calculate different microstructural parameters using XRD data. The optical energy bandgap was found to be decreased in all co-doped samples (3.14–2.82 eV) calculated from UV–vis spectra by employing different methods. The effect of dopants ions on the optical properties of ZnO was also studied in detail. The FTIR spectrum inveterate the existence of Zn–O, and Zn-M–O (M = Ce, Er, Y, V) vibrational mode that further confirmed the incorporation of dopants ions. The photocatalytic performance of the grown products was evaluated under sunlight illumination against methylene blue (MB) dye. The antibacterial activity was performed against gram- positive Staphylococcus aureus and gram- negative Pseudomonas aeruginosa bacteria. The co-doped nanocrystals have shown enhanced photocatalytic and antibacterial activity as compared to Ce-doped ZnO but the Ce–V co-doped ZnO shown the highest activity. The influence of different operational parameters such as the amount of catalyst, the concentration of dye, and pH of the solution on photocatalytic activity of Ce–V co-doped ZnO nanocrystal was also studied and discussed in detail. The radical trapping experiments were also performed to identify the active species involved in photodegradation reaction. The recyclability test exhibited that Ce–V co-doped ZnO catalyst has high stability and can be reused up to the 6th cycles. Furthermore, a possible photocatalytic mechanism was also proposed for the photodegradation of MB dye. [ABSTRACT FROM AUTHOR]