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Maphoru M.V.,Tshwane University of Technology | Heveling J.,Tshwane University of Technology | Pillai S.K.,National Center for Nano structured Materials
ChemPlusChem | Year: 2014

Bismuth-promoted platinum catalysts were tested for the oxidative coupling of 2- and 4-substituted 1-naphthols at different temperatures and ambient pressure. The principal final products are the 3,3'-substituted 1,1'-binaphthalenylidene-4,4'- diones and the 4,4'-substituted 2,2'-binaphthalenylidene-1,1'- diones, respectively. Hydrogen peroxide was used as the oxidant. Only naphthols with electron-donating substituents reacted. The corresponding binaphthalenyl diols can be considered as reaction intermediates. Yields of up to 99% were obtained from 2-methyl-1-naphthol as the starting material within 20 minutes. Probably for steric reasons, the diol is the final product obtained from 2-ethyl-1-naphthol. For 4-methoxy- 1-naphthol the outcome is determined by the reaction temperature. At 25 8C the expected 1,1'-dione is the major product, whereas at 60 8C 1'-hydroxy-4'-methoxy-2,2'-binaphthalenyl- 1,4-dione is formed; the loss of one methoxy unit and the preservation of the hydroxy group can be explained by the competitive cleavage of one of the two O-Me bonds at higher temperature. Unpromoted platinum and a range of other metallic catalysts, including gold and Raney nickel, were also found to be active. The products obtained are brightly colored solids that could be used as dyes. The method described is truly catalytic and environmentally benign. The potential of the technique justifies further research to expand on the applicability of this novel method. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Folarin O.M.,Tshwane University of Technology | Sadiku E.R.,Tshwane University of Technology | Maity A.,National Center for Nano structured Materials
International Journal of Physical Sciences | Year: 2011

Polymer-noble metal nanocomposites have been extensively investigated due to their potential ability to provide materials with novel mechanical, electronic or chemical behaviour for technological applications. Many preparative procedures have been proposed and detailed characterizations have been carried out on conducting polymer-noble metal nanocomposites; thanks to the rapid improvement in analytical techniques on surface and nanoscale materials. This review focuses on the preparation, characterization of polymer-noble metal nanocomposites and some potential areas for applications such as sensors, batteries (fuel cells) and capacitors. © 2011 Academic Journals. Source

Moodley M.K.,National Center for Nano structured Materials | Moodley M.K.,University of Witwatersrand | Coville N.J.,University of Witwatersrand
Chemical Physics Letters | Year: 2010

In situ optical emission spectroscopy (OES) was used to investigate the spatial and temporal evolution of C2, the electron density (Ne) and the electron temperature (Te) of laser induced plasmas in the laser-furnace method of synthesizing single-walled carbon nanotubes (SWCNTs). The intensities of the spectral maps of C2,Ne and Te showed a strong temperature dependence. The frequency of sharp fluctuations which appear as hot spots in the spectral maps of Ne and Te increased as the furnace temperature was increased from 1073 to 1273 K. We suggest that the appearance of hot spots is a result of the heat of formation of SWCNTs. © 2010 Elsevier B.V. All rights reserved. Source

Rajendran R.,SRM University | Muralidharan R.,Indira Gandhi Center for Atomic Research | Santhana Gopalakrishnan R.,Indira Gandhi Center for Atomic Research | Chellamuthu M.,SRM University | And 2 more authors.
European Journal of Inorganic Chemistry | Year: 2011

Single-crystalline Fe3O4 nanorice has been prepared by a simple one-pot, surfactant-assisted hydrothermal method using dodecyltrimethylammonium bromide (DTAB) as a surfactant. X-ray powder diffraction, field emission scanning electron microscopy (FESEM), TEM, high-resolution (HR)TEM, micro-Raman spectroscopy and magnetic measurements have been employed to study the properties of the product. The importance of NaAc and ethylene glycol in the formation of the pure magnetite phase has been established. The as-synthesized products have a regular rice-like shape with an average diameter of 150 nm and length of 500 nm and are monodisperse. Shape evolution from cauliflower- to rice-like morphology has been achieved by controlling the DTAB concentration. A possible formation mechanism for the Fe3O4 nanorice is explored. Furthermore, the product showed ferromagnetic properties at room temperature. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Debnath S.,University of Johannesburg | Ballav N.,University of Johannesburg | Nyoni H.,University of Johannesburg | Maity A.,National Center for Nano structured Materials | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2015

A polyaniline-coated titanium oxide nanocomposite (PTO) was synthesized, characterized and used in the catalytic photo-degradation of the anionic dyes Eosin Yellow (EY) and Naphthol blue black (NBB). An emphasis was placed on the key parameters governing the degradation process. It was noted that the extent of degradation was higher at lower pH for both dyes. The rate of degradation of both dyes also increased with increasing catalyst dosage, Langmuir-Hinselwood models and other second-order kinetic models verified that heterogeneous photocatalysis occurred. The rate of degradation increased with increasing initial dye concentrations and only increased gradually with an increase in UV light intensity in the absence of the catalyst. The optimum operating conditions for the degradation was also predicted using response surface methodology (RSM) analysis as a statistical tool. This analysis revealed that the initial dye concentration, pH and dosage of the catalyst are all significant parameters in the degradation process. The combined effect of pH and initial concentration was antagonistic whilst the combined effect of initial concentration and catalyst dosage and the combined effect of catalyst dosage and pH were both synergistic. The optimum degradation percentages were found to be 99.85 and 99.74 for EY and NBB respectively. These optimum percentage degradations were observed at pH 3.0, initial dye concentration 15mgL-1 and a catalyst dosage of 1.0gL-1. LC-MS data was also used to identify the photodegradation products and to propose a mechanism of photodegradation. © 2014 Elsevier B.V. Source

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