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Nickel ferrite NiFeO nanoparticles (NPs) were successfully synthesized by using nickel nitrate, ferric nitrate, citric acid, and ethyl cellulose as a surfactant by a simple sol-gel-assisted combustion method (SACM) and microwave-assisted combustion method (MACM). Structural, morphological, optical, and magnetic properties of the obtained powder were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). XRD results show that the resultant powder was pure crystalline with cubic structure. The average crystalline size was found to be 18.8 and 10.2 nm synthesized by SACM and MACM, respectively. FT-IR spectra indicate the type of bonds between Ni-O and Fe-O (metal and oxygen). SEM images show that the morphology of the powder consists of well-defined structure. VSM results showed a ferromagnetic behavior of the sample. Antimicrobial activity of NiFeO nanoparticles was performed. Both sample 1 (SACM) and sample 2 (MACM) show good inhibition in the zone 100 μg/ml. While comparing, sample 2 shows high inhibition than sample 1. [ABSTRACT FROM AUTHOR]

Glasses of composition PbO–Nb 2 O 5 –GeO 2 –SiO 2 doped with different concentrations of Cr 2 O 3 (ranging from 0 to 0.5 mol%) were prepared by conventional melt quenching technique. The prepared glasses were characterized by X-ray diffraction (XRD). Spectroscopic studies viz., optical absorption, EPR, FTIR, Raman and photoluminescence were carried out on these glasses. The optical absorption spectra exhibited three bands at about 646, 674 and 711 nm which are the characteristic bands of octahedral Cr 3+ ions. From the analysis of the absorption spectra the crystal field splitting parameters D q , B and nephelauxetic parameters (β and h ) were evaluated. The EPR spectra exhibited two resonance signals at g≈1.97 and g≈4.84. FTIR and Raman spectra have revealed the increasing presence of GeO 6 and NbO 6 structural units in the glass network with increasing the concentration of Cr 2 O 3 in the glass network. Photoluminescence spectra exhibited a broad emission band in the wavelength region 600 to 850 nm with a meta center at about 680 nm which is also a characteristic of Cr 3+ ions. Correlating optical and EPR data the molecular bonding coefficient parameter (α) has been evaluated. The quantitave correlation and analysis of all the results indicated that the glasses doped with higher content of Cr 2 O 3 are efficient luminescence materials. [ABSTRACT FROM AUTHOR]

Abstract: Gallium nitride (GaN) epitaxial layers were grown with different V/III ratios by varying the ammonia (NH3) flow rate, keeping the flow rate of the other precursor, trimethylgallium (TMG), constant, in an MOCVD system. X-ray rocking curve widths of a (102) reflection increase with an increase in V/III ratio while the (002) rocking curve widths decrease. The dislocation density was found to increase with an increase in ammonia flow rate, as determined by hot-wet chemical etching and atomic force microscopy. 77K photoluminescence studies show near band emission at 3.49eV and yellow luminescence peaking at 2.2eV. The yellow luminescence (YL) intensity decreases with an increase in V/III ratio. Positron annihilation spectroscopy studies show that the concentration of Ga-like vacancies increases with an increase in ammonia flow rate. This study confirms that the yellow luminescence in the GaN arises due to deep levels formed by gallium vacancies decorated with oxygen atoms. [ABSTRACT FROM AUTHOR]

Abstract: Gallium nitride (GaN) nanocrystals were synthesized by nitridation of Ga-EDTA (ethylene diamine tetra acetic acid) complexes at different temperatures starting from 600 to 900°C. X-ray diffraction analysis, Fourier transform infrared spectroscopy and Raman studies revealed that the compound synthesized at 900°C consists of single-phase GaN nanocrystals with wurtzite structure. The change in morphology of the GaN crystals at different temperatures was observed using scanning electron microscopy. The transmission electron microscopy showed the average size of the crystalline particles to be ∼20nm. The room temperature photoluminescence exhibits band-edge emission of GaN at 3.46eV for all the samples. The present study demonstrates that the nitridation of Ga-EDTA complex method has significant potential for the synthesis of GaN nanocrystals as a simple and inexpensive method. [Copyright &y& Elsevier]