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Issue 32, 2010
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Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals

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Blinking of zinc blende CdSe-based core/shell nanocrystals is studied as a function of shell materials and surface ligands. CdSe/ZnS, CdSe/ZnSe/ZnS and CdSe/CdS/ZnS core/shell nanocrystals are prepared by colloidal synthesis and six monolayers of larger bandgap shell materials are grown over the CdSe core. Organic-soluble nanocrystals covered with stearate are made water-soluble by ligand exchange with 3-mercaptopropionic acid. The light-emitting states of nanocrystals are characterized by absorption and emission spectroscopy as well as photoluminescence lifetime measurements in solution. The blinking time trace is recorded for single nanocrystals on a glass coverslip. Both on- and off-time distributions are fitted to the power law. The power-law exponents vary, depending on shell materials and surface ligands. The off-time exponents for organic and water-soluble nanocrystals are measured in the range of 1.36–1.55 and 1.25–1.37, respectively, while their on-time exponents are spread in the range of 1.53–1.86 and 1.85–2.17, respectively. Water-soluble surface passivation with thiolate prolongs the dark period regardless of shell materials and core/shell structures. Of the core/shell structures, CdSe/CdS/ZnS exhibits the longest bright state. The on/off-time exponents are inversely correlated, although the successive on/off events are not individually correlated. A two competing charge-tunneling model is presented to describe the variation of on- and off-time exponents with shell materials and surface ligands.

Graphical abstract: Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals

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Publication details

The article was received on 26 Nov 2009, accepted on 06 May 2010 and first published on 07 Jul 2010

Article type: Paper
DOI: 10.1039/B924917F
Citation: Phys. Chem. Chem. Phys., 2010,12, 9312-9319
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    Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals

    B. Chon, S. J. Lim, W. Kim, J. Seo, H. Kang, T. Joo, J. Hwang and S. K. Shin, Phys. Chem. Chem. Phys., 2010, 12, 9312
    DOI: 10.1039/B924917F

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