Self-Organized Ultrathin Oxide Nanocrystals

Uniform ultrathin nanorods were grown in a self assembled fashion by the use of surfactants such as oleylamine and oleic acid that acted as nanocrystal capping as well as directing agent. A 1-2 nm nanocrystal was syntheses using 0.5 g of titanium isopropoxide or titanium butoxide dissolved in dry octadecene 18g and oleic acid 16g under 80C for approx 4 hours. After adding 7 g of oleylamin to this mix, it was heated at 260 C under a nitrogen atmosphere and then cooled to room temp and used centrifugation at 2000 rpm for 10 min to separate the ribbon like structures from the bulk. It was shown by EDS analysis that these were ultrathin TiO2 nanorods 2nm x 20 nm growing spantenously along the c axis, and orderly stacked together side by side without the need of any post processing.
Same synthetic method was applied to ZnO quantum rods generated from ordinary acetate precursors – was further developed with cooperative growth/assembly hypothesis to synthesize transition metal oxide nanowires with sub-2-nm dimension. Mesoscopic oxide nanocrystals were spontaneously formed as ribbon like superstructures. The process involved complexion of precursor species with surfactants that would grow metal-surfactant-monomers. After high temperature it turned into metal oxygen network through an ester elimination process. NRs were then evolved from the layered mesostructures, then disrupted , to allow for nanorods to spontaneously self assemble as 1D superstructures.
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