Synthesis of quantum-sized cubic ZnS nanorods by the oriented attachment mechanism

Ho Yu Jung, Jin Joo, Min Park Hyun, Sung Il Baik, Woon Kim Young, Chul Kim Sung, Taeghwan Hyeon

Research output: Contribution to journalArticlepeer-review

424 Scopus citations

Abstract

Quantum-sized ZnS nanocrystals with quasi-spherical and rod shapes were synthesized by the aging reaction mixtures containing diethylzinc, sulfur, and amine. Uniform-sized ZnS nanorods with the average dimension of 5 nm x 21 nm, along with a small fraction of 5 nm-sized quasi-spherical nanocrystals, were synthesized by adding diethylzinc to a solution containing sulfur and hexadecylamine at 125°C, followed by aging at 300°C. Subsequent secondary aging of the nanocrystals in oleylamine at 60°C for 24 h produced nearly pure nanorods. Structural characterizations showed that these nanorods had a cubic zinc blende structure, whereas the fabrication of nanorods with this structure has been known to be difficult to achieve via colloidal chemical synthetic routes. High-resolution TEM images and reaction studies demonstrated that these nanorods are formed from the oriented attachment of quasi-spherical nanocrystals. Monodisperse 5 nm-sized quasi-spherical ZnS nanocrystals were separately synthesized by adding diethylzinc to sulfur dissolved in a mixture of hexadecylamine and 1-octadecene at 45°C, followed by aging at 300°C. When oleic acid was substituted for hexadecylamine and all other procedures were unchanged, we obtained 10 nm-sized quasi-spherical ZnS nanocrystals, but with broad particle size distribution. These two different-sized quasi-spherical ZnS nanocrystals showed different proportions of zinc blende and wurtzite crystal structures. The UV absorption spectra and photoluminescence excitation spectra of the 5 nm ZnS quasi-spherical nanocrystals and of the nanorods showed a blue-shift from the bulk band-gap, thus showing a quantum confinement effect. The photoluminescence spectra of the ZnS nanorods and quasi-spherical nanocrystals showed a well-defined excitonic emission feature and size-and shape-dependent quantum confinement effects.

Original languageEnglish
Pages (from-to)5662-5670
Number of pages9
JournalJournal of the American Chemical Society
Volume127
Issue number15
DOIs
StatePublished - 20 Apr 2005

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