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DNA autoionization is a fundamental process wherein ultraviolet (UV)-photoexcited nucleobases dissipate energy by charge transfer to the environment without undergoing chemical damage. Here, single-wall carbon nanotubes (SWNT) are explored as a photoluminescent reporter for the study of the mechanism and rates of DNA autoionization. Two-color photoluminescence spectroscopy allows separate photoexcitation of the DNA and the SWNTs in the UV and visible range, respectively. A strong SWNT photoluminescence quenching is observed when the UV pump is resonant with the DNA absorption, consistent with charge transfer from the excited states of the DNA to the SWNT. Semiempirical calculations of the DNA-SWNT electronic structure, combined with a Green's function theory for charge transfer, show a 20 fs autoionization rate, dominated by hole transfer. Rate-equation analysis of the spectroscopy data confirms that the quenching rate is limited by thermalization of the free charge carriers transferred to the nanotube reservoir. This approach has great potential for monitoring DNA excitation, autoionization, and chemical damage, both in vivo and in vitro .

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Publication history

Received: 03 September 2015
Accepted: 04 November 2015
Published: 13 January 2016
Issue date: February 2016

Copyright

© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2015

Acknowledgements

Acknowledgements

T. I. and S. V. R. acknowledge support by National Science Foundation (Nos. ECCS-1202398 and ECCS-1509786); P. S. acknowledges REU NSF (No. PHY-1359195). A. B. acknowledges the startup fund support from the University of Central Florida. The authors gratefully acknowledge access to facilities at the National Institute of Standards and Technology for PL measurements and the computational time support from the UCF Advanced Research Computing Center STOKES. We are thankful to Dr. J. Fagan as the host at NIST, Dr. J. Reimers for providing us with the CNDO code, and Dr. D. Roxbury for providing the MD trajectory.

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Reprints and Permission requests may be sought directly from editorial office.
Email: nanores@tup.tsinghua.edu.cn

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