Publications by authors named "Chockalingam Karunakaran"

Sharp narrow nanopetal-like and wrinkled nanoball-like cubic CuZnFeO-implanted orthorhombic BiS-capped anatase TiO heterostructures have been synthesized by a two-step hydrothermal process in acidic and basic environments. They have been characterized by high-resolution scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, selected area electron and powder X-ray diffractometries, vibrating sample magnetometry, UV-visible diffuse reflectance and photoluminescence spectroscopies, and nitrogen adsorption-desorption analysis. Both the nanostructured composites are superparamagnetic.

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Efficient hole transport materials based on novel fused methoxynaphthyl phenanthrimidazole core structure were synthesised and characterized. Their device performances in phosphorescent organic light emitting diodes were investigated. The high thermal stability in combination with the reversible oxidation process made promising candidates as hole-transporting materials for organic light-emitting devices.

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Understanding the interaction between the nanomaterials and bioactive molecules are of current interest due to the potential application of nanomaterial in biomedical field. The structural, electronic and optical properties of newly synthesised fluorophore 2-(4-methoxynaphthalen-1-yl)-1-phenyl-1H-phenanthro[9.10-d]imidazole have been investigated in detail.

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Fe3O4-implanted ZnO and pristine ZnO nanosheets have been synthesized hydrothermally. High-resolution scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, selected area electron diffractometry, powder X-ray diffractometry, Raman spectroscopy, vibrating sample magnetometry, solid state impedance spectroscopy, UV-visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy show implantation of Fe3O4 in ZnO nanosheets. Fe3O4 core with ZnO shell is of type I core/shell heterostructure which is to quench charge carriers and suppress photocatalysis.

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Cocoon-shaped Sn(4+)-doped ZnO nanoparticles have been synthesized by a solvothermal method using carbon microspheres as a template. The optimum doping level for photocatalysis is 3% (g. atom).

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To sense superparamagnetic iron oxides (Fe2O3 and Fe3O4) nanocrystals a sensitive bioactive phenanthroimidazole based fluorescent molecule, 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole has been designed and synthesized. Electronic spectral studies show that phenanthroimidazole is bound to the surface of iron oxide semiconductors. Fluorescent enhancement has been explained on the basis of photo-induced electron transfer (PET) mechanism and apparent binding constants have been deduced.

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A sensitive imidazole based fluorescent sensor like 4, 5-diphenyl-2(E)-styryl-1H-imidazole, for ZnO has been designed and synthesized via simple steps. The absorption, fluorescence, SEM, EDX and IR studies indicate that imidazole derivative is bound on the surface of ZnO semiconductor. Based on photo-induced electron transfer (PET) mechanism, fluorescent enhancement has been explained and apparent binding constant has been calculated.

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The crystal structures of different forms of TiO2 and those of BaTiO3, ZnO, SnO2, WO3, CuO, Fe2O3, Fe3O4, ZrO2 and Al2O3 nanoparticles have been deduced by powder X-ray diffraction. Their optical edges have been obtained by UV-visible diffuse reflectance spectra. The photocatalytic activities of these oxides and also those of SiO2 and SiO2 porous to oxidize iodide ion have been determined and compared.

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1-Naphthol photodegrades on the surfaces of TiO(2), ZnO, CeO(2), CdO, WO(3), Co(3)O(4), Sb(2)O(3), ZrO(2), La(2)O(3), Y(2)O(3), Pr(6)O(11), Sm(2)O(3) and Al(2)O(3), albeit at different efficiencies, and all the oxides show sustainable photocatalytic activity. The degradation conforms to the Langmuir-Hinshelwood kinetic model and enhances with the intensity of illumination. Dissolved oxygen is essential for the degradation.

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Vanadia photocatalyzes the oxidation of aniline to azobenzene in ethanol. The reaction was studied using natural sunlight and UV irradiation (365 nm) as a function of [aniline], catalyst loading, airflow rate, solvent composition, etc. The photocatalyst exhibits sustainable catalytic activity.

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The oxidation of aniline in glacial acetic acid with percarbonate, a dry carrier of hydrogen peroxide, is a second-order reaction conforming to the isokinetic relationship. The hitherto followed method of correlation of the reaction rates in terms of the structure-reactivity relationships is unsatisfactory and erroneous. But the reaction rates of molecular anilines, obtained for the first time, conform to the structure-reactivity relationships.

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