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Ashoka S.,Bangalore University | Chithaiah P.,Bangalore University | Thipperudraiah K.V.,Ambedkar First Grade College | Chandrappa G.T.,Bangalore University
Inorganica Chimica Acta | Year: 2010

The development of reproducible procedures for the synthesis and organization of nanostructured metal oxides is important in order to exploit the unique properties of these materials for practical applications. The present work describes the transformation of Zn(NH3)4] 2+ into hollow structured ZnO materials through solvothermal decomposition. An increase in ammonia concentration in the reaction medium, significantly changes the morphology of ZnO from spheres made of nanoparticles (20-30 nm) to hollow spheres composed of nanorods (200-350 nm) or to free microrods as evidenced from scanning and transmission electron micrographs (SEM/TEM). The powder X-ray diffraction (XRD) pattern of ZnO confirms formation of the wurtzite structure. Raman and Energy-dispersive spectroscopic (EDS) studies indicate the presence of oxygen deficiency in ZnO. The investigation on the catalytic behavior of ZnO in the synthesis of (4-methoxyphenyl)(phenyl) methanone (MPPM) by Friedel-Crafts acylation of anisole with benzoyl chloride has also been carried out. The results reveal that the prepared ZnO could produce ∼98% of yield compared to 41% produced by commercial ZnO. © 2010 Elsevier B.V. All rights reserved.

Ashoka S.,Bangalore University | Nagaraju G.,Bangalore University | Thipperudraiah K.V.,Ambedkar First Grade College | Chandrappa G.T.,Bangalore University
Materials Research Bulletin | Year: 2010

Crystalline nanowires, nanoribbons, nanorings and sphere like architectures of cadmium carbonate have been synthesized with the spontaneous self-assembly of nanocrystals in aqueous solution under hydrothermal condition. The powder X-ray diffraction (PXRD) patterns of these materials exhibit phase pure hexagonal structure. The perfect circular nanorings with radius 375-437 nm, as a new member of nanostructured cadmium carbonate family are being reported for the first time. The width of the cadmium carbonate nanowires/nanoribbons and nanorings, respectively are found to be in the range 11-30 and 26-50 nm as observed by transmission electron microscope (TEM). The effect of temperature and concentration of urea on the cadmium carbonate morphology is discussed. The plausible growth mechanism for the formation of nanorings is also proposed. © 2010 Elsevier Ltd. All rights reserved.

Chithaiah P.,Bangalore University | Ashoka S.,Bangalore University | Thipperudraiah K.V.,Ambedkar First Grade College | Chandrappa G.T.,Bangalore University
Crystal Research and Technology | Year: 2012

In this article, we report a novel but simple method for the phase transformation of ZnO 2 to flower-like ZnO microstructures hydrothermally at 90°C with and without the assistance of hexadecylamine as surfactant. The generation of zincate ion Zno 2 2-as a growth unit from the reaction between ZnO 2 and peroxide ion O 2 2-in situ plays a key role in the phase transformation of ZnO 2 to ZnO. The morphology, structure, and composition of the products have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Powder X-ray diffraction (PXRD) and energy dispersive X-ray analysis (EDX). It has been demonstrated that the as-fabricated ZnO flowers are composed of self-assembled brooms and rods in the presence and absence of hexadecylamine respectively. On the basis of experimental results, a possible reaction mechanism and the growth processes involved in the formation of flower-like ZnO microstructures are discussed. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Siddaramanna A.,Bangalore University | Veerappa Thipperudraiah K.,Ambedkar First Grade College | Thimmanna Chandrappa G.,Bangalore University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

Despite considerable efforts undertaken in a rapidly developing area of materials research, controlled synthesis of nanostructured ZnO is still a matter of intensive research. Herein, we report a facile base free approach for the fabrication of nanostructured ZnO hollow spheres. In the synthesis, ethylene glycol has been introduced as solvent and crystal-growth modifier and zinc acetate has been used as zinc precursor and also a source of soft template. ZnO nanoparticles of diameter ∼25 nm are assembled into highly regular hollow spheres. The powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and UV-visible spectroscopy have been used to characterize the crystal structure, morphology, composition and optical properties. Powder XRD pattern of ZnO confirms the formation of the wurtzite structure. Presence of oxygen deficiency in the prepared ZnO product is revealed by Raman and EDS studies. Strong emission at 422 nm with three weak emissions at 400, 484 and 529 nm were observed by PL spectrum. The growth mechanism for the formation of ZnO hollow spheres has been discussed on the basis of the growth model for the polar ZnO crystals. © 2012 Elsevier B.V.

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