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

Published

Author(s)

Bonghwan Chon, Sung Jun Lim, Wonjung Kim, Hyeong G. Kang, Taiha Joo, Jeeseong C. Hwang, Seung Koo Shin

Abstract

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.
Citation
Physical Chemistry and Chemical Physics
Volume
12

Keywords

blinking, fluorescence, nanocrystal, quantum dot, single crystal

Citation

Chon, B. , Lim, S. , Kim, W. , Kang, H. , Joo, T. , Hwang, J. and Shin, S. (2010), Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals, Physical Chemistry and Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=903812 (Accessed February 22, 2024)
Created July 6, 2010, Updated October 12, 2021