Nishat Arshi

RAPID AND COST EFFECTIVE SYNTHESIS OF ZnO NANORODS USING MICROWAVE IRRADIATION TECHNIQUE

ZnO nanorods assembled in flower shaped morphology have been successfully synthesized using low power microwave irradiation in a very short duration. The diameter and length of the rods were within 150–190 nm (tip diameter ~15 nm) and 2 μm, respectively, with an aspect ratio of 20–22. The synthesized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared microscopy (FT-IR), photoluminescence (PL) and magnetization measurements. The XRD and FT-IR results indicate that ZnO nanorods have the pure wurtzite structure with lattice parameters a and c of 3.254 and 5.197 A, respectively. The selected area electron diffraction (SAED) pattern reveals that the ZnO nanorods are single crystal in nature and grow along [001] plane. Room-temperature PL spectrum of the as-grown ZnO nanorods shows a near-band-edge (NBE) emission peak and defect induced emissions. Magnetization measurements indicate that ZnO nanorods exhibit room temperature ferromagnetism with remanent magnetization (Mr) and coercivity (Hc) about 2.92 × 10-4 (emu/g) and 29.75 Oe, respectively, which may be due to the presence of defects in the ZnO nanorods.

Large Magnetic Entropy Change in La 0.55 Ce 0.2 Ca 0.25 MnO 3 Perovskite

In this paper, magnetic property and magnetocaloric effect (MCE) in perovskite manganites of the type La (0.75-X) Ce X Ca 0.25 MnO 3 (x = 0.0, 0.2, 0.3 and 0.5) synthesized by using the standard solid state reaction method have been reported. From the magnetic measurements as a function of temperature and applied magnetic field, we have observed that the Curie temperature (T C ) of the prepared samples strongly dependent on Ce content and was found to be 255, 213 and 150 K for x = 0.0, 0.2 and 0.3, respectively. A large magnetocaloric effect in vicinity of T C has been observed with a maximum magnetic entropy change (|ΔSM| max ) of 3.31 and 6.40 J/kgK at 1.5 and 4 T, respectively, for La 0.55 Ce 0.2 Ca 0.25 MnO 3 . In addition, relative cooling power (RCP) of the sample under the magnetic field variation of 1.5 T reaches 59 J/kg. These results suggest that La 0.55 Ce 0.2 Ca 0.25 MnO 3 compound could be a suitable candidate as working substance in magnetic refrigeration at 213 K.

NOVEL AND COST-EFFECTIVE SYNTHESIS OF SILVER NANOCRYSTALS: A GREEN SYNTHESIS

This paper reports the study on the synthesis and characterization of silver nanocrystals by a two-step synthesis procedure. The first step is the solution-free hand grinding of silver foil and sugar at room temperature for few minutes. The second step is the thermal decomposition of silver/sugar composite to form silver nanocrystals. The as-synthesized silver nanocrystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet visible (UV/Vis) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies. The XRD pattern showed a face-centered cubic structure (single phase) with high crystallinity. The lattice parameters calculated from XRD pattern were found to be a = 4.12 A for silver nanocrystals with average grain size of ~ 19 nm. The energy dispersive analysis of X-rays (EDAX) of silver nanocrystals confirmed the presence of silver and no peak of any secondary phase was detected. FESEM and AFM studies showed that the crystals have cube-like morphology. TEM results showed that the size of silver nanocrystals was found to be ~ 22 nm. This novel synthesis route, not reported earlier, would be a promising candidate for a variety of future applications of silver nanocrystals.

STRUCTURAL AND MAGNETIC STUDY OF Co-DOPED ZnO NANOPARTICLES SYNTHESIZED BY AUTO COMBUSTION METHOD

In the present work, we have synthesized Zn1-xCoxO(x = 0.0 ≤ x ≤ 0.1) nanoparticles by an auto-combustion method using C2H5NO2 (glycine) as a fuel. The prepared nanoparticles were characterized by using X-ray diffraction, transmission electron microscopy, Photo-luminescence (PL) and magnetization measurements. XRD and TEM results demonstrated that Co-doped ZnO have a single phase nature with wurtzite structure and Co2+ ions were successfully incorporated into the lattice position of Zn2+ ions in ZnO matrix. PL spectra show two emission bands in visible region. Magnetic studies showed that Co-doped ZnO nanoparticles exhibit room temperature ferromagnetism.

Relationship Between Structural, Morphological, Optical and Magnetic Properties of Transition Metal (TM)-Doped ZnO Nanostructures Prepared by Microwave-Hydrothermal.

In this work, pure and 3% TM (Co, Ni, and Cu)-doped ZnO nanostructures were prepared by microwave-hydrothermal method. The striking similarities between changes in the lattice volume, bandgap energy, morphology and saturation magnetization indicated a strong correlation between these properties. XRD, SAED and HRTEM analyses revealed that all the TM-doped ZnO nano-structures have wurtzite structure and no secondary phase was detected. FESEM and TEM results confirmed a higher aspect ratio and highly crystalline nature of nanostructures. Raman spectra revealed that no defect related mode was observed which indicated that the nanostructures have high quality and negligible defects. The value of bandgap was found to decrease with the increase in atomic number of TM dopants. RTFM was observed in all the TM-doped ZnO nanostructures and the value of Ms and Mr were decreased with TM dopants.

EFFECT OF SUBSTRATE TEMPERATURE ON MICRO-STRUCTURAL PROPERTIES OF Ti AND TiN FILMS DEPOSITED BY E-BEAM EVAPORATION TECHNIQUE

We report the deposition of Ti and TiN films on Si/SiO2 (100) substrate using e-beam evaporation technique. The influence of substrate temperature on the structural and morphological properties has been studied. The structure and morphology of the deposited films were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) measurements, respectively. XRD patterns reveal the FCC symmetry for both the Ti and TiN films. The grain size of the films was found to increase with the increase in substrate temperature. FESEM micrographs showed a smooth morphology of the film with columnar grain structure.

Structural, magnetic and magnetocaloric properties of La{sub 0.65}Sr{sub 0.35}V{sub 0.1}Mn{sub 0.9}O{sub 3} perovskite

Abstract A new complex magnetic material La 0.65 Sr 0.35 V 0.1 Mn 0.9 O 3 , suitable for the magnetic refrigeration, has been investigated. X-ray diffraction result showed that this compound had rhombohedral structure. The substitution of manganese with V leads to a decrease in the Curie temperature, T C from 378xa0K to 353xa0K. Using Arrott plots; it was found that the phase transition for this compound is of the second-order. The magnetocaloric study exposed a quite large value of the magnetic entropy changexa0∼xa01.56xa0J/kgxa0K and the relative cooling power value of 67xa0J/kg at magnetic field variation of 1xa0T.