LETTER pubs.acs.org/NanoLett
Bright Fluorescence from Individual Single-Walled Carbon Nanotubes Andrea J. Lee,||,† Xiaoyong Wang,||,† Lisa J. Carlson,† Julie A. Smyder,† Bradford Loesch,† Xiaomin Tu,‡ Ming Zheng,‡ and Todd D. Krauss*,‡,§ †
Department of Chemistry, University of Rochester, Rochester, New York 14627, United States DuPont Central Research and Development, Wilmington, Delaware 19880, United States § Institute of Optics, University of Rochester, Rochester, New York 14627, United States ‡
bS Supporting Information ABSTRACT: Single-walled carbon nanotubes (SWNTs) have unique photophysical properties but low fluorescence efficiency. We have found significant increases in the fluorescence efficiency of individual DNA-wrapped SWNTs upon addition of reducing agents, including dithiothreitol, Trolox, and β-mercaptoethanol. Brightening was reversible upon removal of the reducing molecules, suggesting that a transient reduction of defect sites on the SWNT sidewall causes the effect. These results imply that SWNTs are intrinsically bright emitters and that their poor emission arises from defective nanotubes. KEYWORDS: Single-walled carbon nanotubes, fluorescence, epifluorescence microscopy, near-infrared fluorescence
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ingle-walled carbon nanotubes (SWNTs) display remarkably stable and size-tunable fluorescence at near-infrared (NIR) wavelengths.1,2 Fluorescence from SWNTs was first discovered upon exfoliation of nanotube bundles using an ultrasonic technique that wrapped individual nanotubes with surfactant molecules.3 Surfactant wrapping is necessary because neat SWNTs aggregate into bundles, and metallic SWNTs in bundles quench the fluorescence from semiconducting species. Single molecule fluorescence studies of isolated SWNTs have revealed striking photophysical features, including stable and uninterrupted (or nonblinking) fluorescence,2 narrow homogeneous line widths,4 and emission of single photons at low temperatures.5 In addition, the robust fluorescence observed from individual semiconducting SWNTs makes these materials exceptional candidates for several applications, including fluorescence tracking of single molecules in vivo,6 NIR sources of single photons for quantum optics,5 and nanometer-scale optoelectronic components.7 However, macroscopic samples of SWNTs have extremely low fluorescence efficiencies (
