Impact of Synthesis Technique on Lanthanum Doped Copper Oxide Nanocrystals, an Alternative Counter Electrode for Pt-Free Dye-Sensitized Solar Cells.

The ascendancy of a counter electrode (C.E) in a dye-sensitized solar cell (DSSC) has an unrivaled impact on the performance of the dye-sensitized solar cell, where the Pt-based C.E has set up a phenomenal benchmark against its counterparts. Due to the high cost of such noble metals, an operative and a much cost effective replacement were greatly in demand to gratify this need. To address this issue, monoclinic lanthanum doped copper oxide (CuO) nanoparticles were prepared by solution combustion and co-precipitation techniques respectively as they possess highly superior optoelectronic, catalytic and charge transfer properties. The effect of incorporating lanthanum (La) ions and the variation of synthesis technique on their structural, optical, photo-thermal and morphological properties are empirically investigated by XRD, FTIR, TEM, UV-Vis, Raman and Photoacoustic Spectroscopy (PAS). The X-ray diffraction pattern revealed the formation of La-doped CuO nanoparticles. The finger-print vibrational modes of the as-synthesized samples are confirmed by the FTIR spectra. The required optical properties of the as-synthesized nanocrystals were confirmed using UV-Vis absorption spectra, from which the bandgap was determined by Kubelka-Munk plot. The Raman modes were determined using Raman spectra, further a multi-phonon band was revealed, which was formed due to the plasmon-phonon coupling. The photothermal phenomenon was revealed using the photoacoustic spectra. The morphological investigation by TEM found the change in the morphology of the material as the synthesis route is varied. The power conversion efficiency results unveiled that the combustion-derived C.E posted a promising efficiency (η) of 0.20% and the co-precipitation derived C.E posted an efficiency of 0.02%. Overall results suggest that the combustion derived La doped CuO nanostructures exhibited substantive properties with deeper implication and also stood out to be a viable, cost-effective and self-exemplifying replacement for Pt as C.E in DSSC's.

Investigation on Elastic, Magnetic, Optical and Electrical Impedance Properties of Dysprosium Doped Nickel Ferrite Nanocrystals.

Rare earth dysprosium (Dy) doped nickel ferrite nanoparticles were synthesized via economically viable co-precipitation technique and studied for its elastic, structural, magnetic and electrical properties. X-ray diffraction analysis shows the formation of cubic spinel phase with a slight inclination in the cell parameters with respect to the concentration of dopant convivial. The crystallite size and strain of the nanoparticles were determined using Scherrer formula and the Williamson-Hall (W-H) technique. In addition, the theoretical parameters viz., cation distribution, bond length, oxygen positional parameters, etc., have been embrasured. The strength and types of interionic bonds in the nano ferrites were determined utilizing Fourier Transform Infrared spectral analysis. The magnetic properties were analysed using vibrating sample magnetometer at room temperature, it was found that as the dopant concentration increases, the coercivity and magnetic saturation decreases. This result is partially explained by the bridge networking of Dy3+-Fe3+ ions which is equated by Fe2+- Fe3+ ion interaction. This paper deals with the itinerant electron model to determine the distribution of cations by magnetization analysis. The optical properties of the samples were studied utilizing UV-Vis spectral analysis and the optical band gap was evaluated from Kubelka-Munk plot. Electrical impedance was analysed as a function of frequencies at room temperature. This analysis depicts the dielectric constant and loss factor tends to decline with applied frequency and AC conductivity elicits its semiconducting characteristic by obeying Jonscher's law.

Effect of Lanthanum Substitution on Magnetic and Structural Properties of Nickel Ferrite.

Inverse spinel ferrites have demanded substantial attention in the recent past owing to their diverse technological deeds by conquering admirably with its surface, finite size effects and optical properties which has its proficient applications in photocatalytic degradation, magnetic resonance imaging and sensors etc. The substituted La3+ ions delay the development of grain growth of the materials in a meticulous manner compared with that of the pure Ni ferrites. We tale development of magnetic features in La3+ substituted Ni nano-ferrites synthesized by co-precipitation technique and then analyzed from the structural and magnetic perspectives. A credible and thriftily doable co-precipitation method has been the spotlight of forethought in recent decades to synthesize these ferrite nanoparticles. Enviable inverse spinel phase has been observed, as it is essential to modify and optimise its micro structural and magnetic features. The phase formation and significant properties of Ni1-xLaxFe2O4 ferrites were investigated using XRD, FTIR, TEM, UV-visible, VSM and FT-Raman techniques. The crystallite size of the as-synthesized nanoparticles were observed after the substitution of La3+ content in the range of 8 to 15 nm. As the dopant concentration increases the crytallite size increases and other changes in crystallographic parameters, as well as the cation distribution also observed. The TEM micrograph clearly reveals the cubic and the notable polycrystalline nature. The FTIR measurements carried out in the range of 400-4000 cm-1 elucidates the occurrence of functional groups. The UV-visible spectrum analysis reveals the optical property of as-synthesized nanoparticle and hence their band gap was found using Kubelka-Munk plot. The magnetic parameters were studied by vibrating sample magnetometer and the saturation magnetization of the ferrites at the room temperature decreases with the reduction in size.