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Published online by Cambridge University Press: 31 January 2011
A novel synthesis route to organic-capped and colloidal ZnO quantum dots (QDs) has been developed. Specifically, zinc-di-butoxide was hydrolyzed with very dilute water (100˜600 mass ppm) dissolved in hydrophilic benzylamine and polymerized to ZnO by dehydration condensation. After formation of ZnO QDs with 2˜3 nm in diameter, growth of the QDs and exchange the surface capping ligand from hydroxyl groups and/or benzylamine to oleylamine were developed by heating the colloidal solution with oleylamine. The size of the ZnO QDs finally obtained was in the range 3˜5 nm in diameter. The QDs show high dispersibility in various organic solvents. Clear UV emission due to exciton recombination was observed; and its energy was varied according to the quantum size effect from 3.39 to 3.54 eV. By using lithium-free zinc-di-butoxide as a starting material, the defect-related VIS emission was successfully decreased and the UV emission becomes dominant. The influence of water concentration in benzylamine and oleylamine on UV emission intensity was also investigated.