Nano Archive

Excitation-Wavelength Dependence of Fluorescence Intermittency in CdSe Nanorods

Knappenberger, Kenneth L. and Wong, Daryl B. and Xu, Wei and Schwartzberg, Adam M. and Wolcott, Abraham and Zhang, Jin Z. and Leone, Stephen R. (2008) Excitation-Wavelength Dependence of Fluorescence Intermittency in CdSe Nanorods. ACS NANO, 2 (10). pp. 2143-2153.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/nn800421g

Abstract

The influence of excitation wavelength and embedding media on fluorescence blinking statistics of 4 nm x 20 nm cadmium selenide(CdSe) nanorods is investigated. Photon antibunching (PAB) experiments confirm nonclassical emission from single CdSe nanorods that exhibit a radiative lifetime of 26 +/- 13 ns. The blinking data show behaviors that can be categorized into two classes: excitation near the energy of the band gap and at energies exceeding 240 meV above the band gap. Excitation at the band gap energy (lambda >= 560 nm) results in more pronounced ``on'' time probabilities in the distribution of ``on'' and ``off'' events, while those resulting from excitation exceeding the band gap by 240 meV or more (lambda <= 560 nm) are 200 times less likely to display continuous ``on'' fluorescence persisting beyond 4 s. The ``off'' time statistics are also sensitive to the excitation wavelength, showing a similar, but inversely correlated, effect. To understand better the excitation-wavelength dependence, fluorescence measurements are obtained for single nanorods deposited both on a bare microscope coverslip and embedded in 1-ethyl-3-methylimidizolium bis(trifluoromethylsulfonyl)imide room-temperature ionic liquid (RTIL). The embedding RTIL medium has a significant influence on the resultant fluorescence statistics only when the excitation energy exceeds the 240 meV threshold. The results are explained by a threshold to access nonemissive trap states, attributed to self-trapping of hot charge carriers at the higher photon excitation energies.

Item Type:Article
Uncontrolled Keywords:fluorescence intermittency; CdSe nanorod; photon antibunching; trap-state quenching; single molecule; ionic liquids
Subjects:Material Science > Nanostructured materials
Physical Science > Photonics
ID Code:1903
Deposited By:Farnush Anwar
Deposited On:16 Dec 2008 11:16
Last Modified:16 Dec 2008 11:16

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