Nano Archive

Noncovalent functionalization of carbon nanotubes by fluorescein-polyethylene glycol: Supramolecular conjugates with pH-dependent absorbance and fluorescence

Nakayama-Ratchford, Nozomi and Bangsaruntip, Sarunya and Sun, Xiaoming and Welsher, Kevin and Dai, Hongjie (2007) Noncovalent functionalization of carbon nanotubes by fluorescein-polyethylene glycol: Supramolecular conjugates with pH-dependent absorbance and fluorescence. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 129 (9). 2448+.

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Official URL: http://dx.doi.org/10.1021/ja068684j

Abstract

We report the use of fluorescein-polyethylene glycol (Fluor-PEG) to noncovalently functionalize single-walled carbon nanotubes (SWNTs) for obtaining water-soluble nanotube conjugates (Fluor-PEG/SWNT) and simultaneously affording fluorescence labels to nanotubes. We find serendipitously that fluorescein, a widely used fluorophore, can strongly adsorb onto the sidewall of the SWNTs, likely via pi-stacking, and the hydrophilic PEG chain imparts high aqueous solubility. Interaction between fluorescein and SWNT is pH dependent; it weakens as the pH is increased, causing the Fluor-PEG/SWNT conjugate to be less stable at high pHs. Fluorescein molecules bound to SWNTs exhibit interesting pH-dependent optical absorbance and fluorescence properties that are distinct from free molecules, as a result of pH-dependent interactions with SWNT sidewalls. Fluorescence emission from fluorescein adsorbed on SWNT is quenched by similar to 67%, but remains sufficient and useful as a fluorescent label. The utility of Fluor-PEG/SWNT as a simultaneous fluorescent marker and an intracellular transporter is demonstrated by uptake of Fluor-PEG/SWNT by mammalian cells and detection of fluorescence inside the cells. Raman detection of SWNTs in the cells is also carried out and used to prove the co-localization of fluorescein and SWNT.

Item Type:Article
Subjects:Physical Science > Nano objects
Biomedical Science > Nanobiotechnology
Material Science > Nanostructured materials
Material Science > Nanochemistry
ID Code:3223
Deposited By:Anuj Seth
Deposited On:14 Jan 2009 14:42
Last Modified:20 Jan 2009 16:01

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