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