Reversible fluorescence quenching in carbon nanotubes for biomolecular sensing

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Biosensing applications of single-walled carbon nanotubes have been demonstrated in solid-state device structures1,2,3. Bioanalyte sensing schemes based on coupling of reversible nanotube fluorescence quenching to redox reactions paired to enzymatic peroxide generation have also been pursued4,5. Here we show a new approach to highly sensitive nanotube-based optical sensing. Single-walled carbon nanotubes interacting with dye–ligand conjugates—a redox-active dye molecule that is covalently bound to a biological receptor ligand (such as biotin in this case)—showed fluorescence quenching. Further interaction between the receptor ligand on the conjugates and target analytes (avidin in this case) induced the recovery of the quenched fluorescence, forming the basis of the sensing scheme. Nanomolar sensitivity was attained with high specificity for the target analyte. This is a versatile approach because a wide range of conjugation possibilities exists between the potential receptors and redox quenchers.

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Figure 1: Structures of the dye–ligand conjugates and their doping effects on nanotube emission spectra.
Figure 2: Photo-induced charge-transfer quenching mechanism.
Figure 3: Spectra of fluorescence recovery in doped nanotubes.
Figure 4: Fluorescence recovery through non-specific protein interactions.
Figure 5: Sensitivity and selectivity of DLC-based nanotube sensing.


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This work was carried out under the auspices of the National Nuclear Security Administration for the US Department of Energy at Los Alamos National Laboratory (LANL). Partial support was provided by the LANL Laboratory Directed Research and Development program.

Author information

S.B.C., H.-L.W. and S.K.D. conceived and designed the experiments performed by S.B.C., L.O.B. and Y.G. designed and performed the DLC synthesis. C.-C.W. performed DLC synthesis and electrochemical measurements. All authors took part in co-writing the paper.

Correspondence to Stephen K. Doorn.

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The authors declare no competing financial interests.

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Satishkumar, B., Brown, L., Gao, Y. et al. Reversible fluorescence quenching in carbon nanotubes for biomolecular sensing. Nature Nanotech 2, 560–564 (2007) doi:10.1038/nnano.2007.261

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