Advanced Materials Research Vol. 938

Abstract: In this work, synthesis strategy of Cu₂O nanosphere and cube was elucidated and the structural, optical and magnetic properties were studied. Cu₂O nanospheres and cubes were synthesized by wet chemical method through selecting the appropriate amount of isopropyl alcohol (IPA) with distilled water as solvent. 5% of IPA yielded cubic shape Cu₂O and 30% of IPA yielded spherical Cu₂O. The phase purity was confirmed with powder XRD. The FTIR result exhibit Cu (I)-O vibrational band around 628 cm^-1 supports the XRD results. In Raman spectra weak band at 508 cm^-1 corresponds to Raman allowed mode. The IR active bands at 110 and 150 cm^-1 are observed because of the violation of selection rules which demonstrates the defects present in synthesized Cu₂O. Raman peaks at 218 and 415 cm^-1 are assigned to multiphonon Raman scattering. The UV-Vis diffuse reflectance spectrum was recorded to calculate the band gap value. The band gap value calculated using Kubelka-Munk equation was 2.015 eV and 2.025 eV, respectively, for Cu₂O cube and nanosphere.

Abstract: Near-field scanning optical microscopy (NSOM) is known to be a technique of choice to investigate nanometric materials and their properties beyond far-field diffraction limit resulting high spatial, spectral and temporal resolution. Here in this report, a state of art facility, aperture-NSOM was used to probe single nanoparticle, dimer, trimer and small nanoaggregate of gold nanoparticles. Shear force topography and two photon induced photoluminescence (TPI-PL) images captured simultaneously by the system facilitated to clarify the correlation between the local geometry and the emitted photon of TPI-PL. Small gold aggregates including trimer showed strong optical confinement of TPI-PL with reference to that of single gold nanoparticles. It was also evident that the interparticle gap does have a great influence in localized electromagnetic (EM) field mediated optical confinement of TPI-PL. Such observations were also supported by finite different time domain (FDTD) analysis keeping the simulation parameter nearly identical to that of experiment. FDTD simulation demonstrated that incident excitation parallel to the interparticle axis induces strong near-field distribution at the interstitials whereas out of plane excitation modifies such confinement depending on the nanometric geometry of the nanoaggregates. Such an observation is indispensable to understand the localized EM field-mediated optical confinement in surface-enhanced spectroscopy.

Abstract: ZnO nanocomposites such as (ZnO) _0.8(MnO₂)_0.2, (ZnO) _0.8(TiO₂)_0.2and (ZnO) _0.8 (MnO₂)_0.1(TiO₂)_0.1 were prepared by solid state reaction method at room temperature. The structural analysis was carried out with help of powder XRD to confirm the formation of the composites. The morphological properties and presence of elemental compositions were analyzed with scanning electron microscope and energy dispersive analysis spectroscopy respectively. Optical properties were studied with UV visible spectrophotometer. From the transmittance spectrum, it is concluded that the synthesized composite materials have the transmittance in the range of 80 to 95% in the visible region. The calculated optical band gap values for pure ZnO is 3.16 eV and the values are 3.7eV, 5.27eV and 4.46eV for the composites ZnO/MnO₂, ZnO/TiO₂ and ZnO/MnO₂/TiO₂, respectively. The study has found that the ZnO/MnO₂, ZnO/TiO₂ and ZnO/MnO₂/TiO₂ composites have very large energy gap as that of insulator.

Abstract: Nanoparticles of MgFe₂O₄ with average crystallite size of ~ 8 nm have been synthesized employing non-aqueous combustion method. Structural properties of the nanoparticles are analyzed with the help of X-Ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), Energy dispersive X-Ray analysis (EDX), Fourier Transform Infra-Red spectroscopy (FT-IR). X-Ray Diffraction pattern and FT-IR spectra reveal the formation of spinel structure of MgFe₂O₄ nanoparticles. The SEM micrographs of the sample show the formation of clusters of spherical particles with pores revealing the history of synthesis as combustion process. The constituent elements and chemical composition are analyzed using EDX spectrum. Magnetic study done using Vibrating Sample Magnetometer (VSM) reveals that the prepared nanoparticles remain unsaturated within the field of 15 kOe and have a very low coercivity of 20 Oe.

Abstract: Pure and Fe-doped CuO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Fe) were prepared by a facile and fast microwave combustion method. The structure and morphology of the samples were investigated by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). The XRD patterns refined by the Rietveld method indicated the formation of single-phase monoclinic structure and also confirm that the Fe ions are successfully incorporated into the CuO crystal lattice by occupying Cu ionic sites. Interestingly, the morphology was found to change considerably from nanoflowers to nanorod and disk-shaped then to nanoparticles with the variation of Fe content. The optical band gap calculated using DRS was found to be 2.8 eV for pure CuO and increases up to 3.4 eV with increasing Fe content. Photoluminescence measurements also confirm these results. The magnetic measurements indicated that the obtained nanostructures are found to show a room temperature ferromagnetism (RTF) with an optimum value of saturation magnetization at 2.0 wt.% of Fe-doped CuO, i.e.1.2960 x 10 ^-3 emu/g.

Abstract: Multiferroics have been known as materials exhibiting both ferroelectric and ferromagnetic properties in same phase, they have interesting physical properties as well as possibility of practical application in some new memories, spintronics and sensor devices. The present work reports the fabrication of pure and Nickel substituted Bismuth Ferrite by simple hydrothermal method at 180 ^o C for 11 hours. The structural study was carried out using X-ray powder diffraction (XRD), and the Dielectric properties were investigated over a wide range of frequency and temperature. The image of SEM is in good agreement with the XRD analysis. The synthesis method is simple and cost effective. KEYWORDS: Multiferroics; Dielectric loss; Hydrothermal method; XRD.

Abstract: In this paper, the novel ZnO nanophosphors is synthesized by solgel method. The study exposed ZnO nanophosphors samples in Gamma (y) radiation to investigate their thermo-luminescence (TL) intensity as a function of temperature. The thermo-luminescence response has been studied in the dose range 0.291.16 kGy and it is observed that the thermo-luminescence response increases with increase in the dose. Moreover, the TL intensity increases with temperature and attains its maximum value near 200 Cand decreases after this temperature. Keywords: Dosimetry; Thermo-luminescence; Zinc oxide; Nanophosphors.

Abstract: A highly porous polythiophene (PTh) nanofibers were synthesized by surfactant assisted dilute polymerization method using FeCl₃ as oxidant. They were confirmed by XRD and FTIR analysis. The surface morphology of PTh was done by scanning electron microscopy (SEM). The prepared polythiophene nanofibers were subjected to calcination under inert gas atmosphere at 1400oC for 2 hrs to get carbonaceous PTh nanofibers. The asymmetric supercapacitor was assembled using PTh nanofibers as the cathode and carbonaceous PTh nanofibers as the anode in 6M KOH electrolyte. The electrochemical supercapacitor performances were carried out to find out the specific capacitance, energy density and power density of the cell. The above results confirmed that the prepared PTh nanofibers and carbonaceous PTh nanofibers could be used as electrode materials for asymmetric supercapacitor applications. Keywords: Polythiophene, Dilute polymerization method, Carbonaceous material, Asymmetric supercapacitor, Specific capacitances

Abstract: The conducting polymers are vital sources for fabrication of micro electronics chips, GMR sensors, membranes and flexible electrodes. Polyaniline is widely chosen for such products because of its conductivity range. This paper focuses on the studies of dual phase properties of Polyaniline (PANI) - Magnetic Iron Oxide (MIO) composites wherein MIO micro and nanoparticles were incorporated in polyaniline. This type of MIO-Polyaniline composites can enhance both conductive and magnetic property. Polyaniline was synthesized by redox polymerization technique with MIO both in micro and nanosize by in-situ polymerization. The MIO content was maintained at 0.2 to 0.6 gm with respect to 4.6 gm of aniline in polymerization reaction. The composites were characterized by FTIR, UV, XRD, SEM and VSM and conductivity unit. The saturation magnetization of composites was 0.0057 emu/g for 0.6 MIO micro spheres and 1.5507 emu/g for 0.6 MIO nanospheres. The DC conductivity values for pure PANI are 2.06x10^-2 S/cm , 5.13x10^-3 S/cm for PANI-0.6 micro MIO and 1.13x10^-3 S/cm for PANI-0.6 nanoMIO. Micro tubular structure was observed for PANI composite in SEM . It is evident that the electrical properties are altered significantly on tailoring MIO in microtubes and the magnetic property is altered by tuning the composition of MIO from micro to nanorange. These composites will satisfy the properties for applications such as actuators, supercapacitors, EMI shielding, Fuel cells and Sensors. Key words: Polyaniline, Microtubes, Magnetic iron oxide, DC conductivity

Abstract: 1,4-Bis (dimethyl) benzyl octyl ethylene diammonium bromide chloride has been synthesized, characterized and applied as new phase transfer catalyst in the alkaline hydrolysis of PET leading to depolymerisation. The new phase transfer catalyst has been compared with the alkaline hydrolysis of PET using zinc sulfate as catalyst in the depolymerization. It was found that the newly synthesized phase transfer catalyst exhibited excellent conversion than the alkaline hydrolysis of PET using zinc sulfate as catalyst.