RESUMEN
Although cyclo[18]carbon has been isolated experimentally from two precursors, C18Br6 and C18(CO)6, no reaction mechanisms have yet been explored. Herein, we provide insight into the mechanism behind debromination and decarbonylation. Both neutral precursors demonstrate high activation barriers of â¼2.3 eV, while the application of an electric field can lower the barriers by 0.1-0.2 eV. The barrier energy of the anion-radicals is found to be significantly lower for C18Br6 compared to C18(CO)6, confirming a considerably higher yield of cylco[18]carbon when the C18Br6 precursor is used. Elongation of the C-Br bond in the anion-radical confirms its predissociation condition. Natural bonding orbital analysis shows that the stability of C-Br and C-CO bonds in the anion-radicals is lower compared to their neutral species, indicating a possible higher yield. The applied analysis provides crucial details regarding the reaction yield of cyclo[18]carbon and can serve as a general scheme for tuning reaction conditions for other organic precursors.
RESUMEN
A new patented method for the synthesis of nanosized powders of indium(III) hydroxide and oxide using the strong base anion exchange resin AV-17-8 as a precipitate agent was proposed. The effect of anions of the initial indium salt and the influence of the process duration, temperature, and counterions of resin such as hydroxide or carbonate on the yield of indium(III) hydroxide during the anion resin exchange precipitation were investigated by scanning electron microscopy, electrical conductivity measurement method, and atomic absorption analysis. Based on the obtained data, the mechanism of the anion resin exchange precipitation of indium(III) hydroxide was suggested. The products were characterized by X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, elemental analysis, Brunauer-Emmett-Teller, and transmission electron microscopy. It was found that impurity-free monophasic In2O3 powders with an average particle size of 10-15 nm and specific surface area of 62-73 m2/g were formed after heat treatment of as-prepared products at 400 °C.
RESUMEN
Although nanoparticles of heavy metal xanthates and their hydrosols can play important roles in froth flotation, environmental issues, analytics, and manufacturing of metal sulfide nanocomposites, they have received little attention. We studied colloidal solutions and immobilized particles prepared via interaction of aqueous lead nitrate with alkyl xanthates applying UV-vis absorption spectroscopy, dynamic light scattering, zeta potential measurement, thermogravimetry analysis, Fourier transform infrared spectroscopy, Raman scattering, X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy. The hydrodynamic diameter of colloidal particles of Pb(SSCOR)2 decreased from 500 to 50 nm with an increase in the alkyl radical length and the initial xanthate to lead ratio (X/Pb); the zeta potential magnitude varied similarly, although it remained negative. The effect of pH in the range of 4.5-11 was minor, but the colloids produced using excess of Pb2+ in alkaline media were close to PbX and decomposed much easier than PbX2. The uptake of lead xanthates on supports was generally low because of negative charges of the colloids; however, 50-100 nm thick PbX2 films were deposited on PbS and SiO2 from the media of X/Pb < 2 and pH < 9 because of preadsorption of Pb2+, while nanorods formed on highly oriented pyrolytic graphite.