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Xiaomin (Helen) Tu

Research Interests: 

DNA-Based Carbon Nanotube Purification

DNA-assisted separation of single-walled carbon nanotube via ion-exchange chromatography has demonstrated exceptional recognition capability of this approach. A set of DNA sequences capable of purifying 12 (n, m) single-chirality nanotubes (shown right) has been identified after systematic search of the DNA library. It is shown that the length and the sequence of DNA and the experimental condition can all influence the separation outcome. Therefore, tuning these parameters has the potential of discovering more single-chirality nanotube species and optimizing the resolution and the yield.

DNA-Nanotube Interaction

The mechanism of the DNA-based separation is not entirely clear; however, the ordered structure of DNA wrapping around nanotube is believed to hold the key. Therefore, investigating DNA–nanotube interaction becomes vital to unveil the mechanism of the separation and other interesting properties of DNA and nanotube. 

Carbon Nanotube Environmental and Health Safety (EHS)

The accurate evaluation of the toxicity of carbon nanotube, especially to biological molecule, is a very important field. The oxidative stress experienced by DNA molecules in the presence of carbon nanotube can inform us of the safety of the material in long term and reveal structural information of DNA-nanotube hybrid.

Absorption spectra of 12 semiconducting carbon nanotubes purified by DNA from HiPco starting material


There are many more exciting Nanotube Metrology projects in the Complex Fluids Group of Polymers Division. Please refer to these links for more information.


1) Roxbury, D.; Tu, X.; Zheng, M.; Jagota, A. Recognition ability of DNA for carbon nanotubes correlates with their binding affinity. Langmuir, 2011, DOI: 10.1021/la2007793

2) Duque, J.G.; Chen, H.; Swan, A.K.; Shreve, A.P.; Kilina, S.; Tretiak, S.; Tu, X.; Zheng, M.; Doorn, S.K. Violation of the codon approximation in semiconducting carbon nanotubes. ACS Nano, 2011, DOI: 10.1021/nn201430z

3) Lee, A.J.; Wang, X.; Carlson, L.J.; Smyder, J.A.; Leosch, B.; Tu, X.; Zheng, M.; Krauss, T.D. Bright fluorescence from individual single-walled carbon nanotubes. Nano Letter, 2011, 11, 1636-1640.

 4) Wang, S.; Khafizov, M.; Tu, X.; Zheng, M.; Krauss, T.D. Multiple exciton generation in single-walled carbon nanotubes. Nano Letter 2010, 10, 2381-2386.

5) Vora, P.M.; Tu, X.; Mele, E.J.; Zheng, M.; Kikkawa, J.M. Chiral dependence of the K-Momentum dark excitons in carbon nanotubes. Physical Review B 2010, 81, 155123.

6) Tu, X.; Manohar, S.; Jagota, A.; Zheng, M. DNA sequence motifs for structure-specific recognition and separation of carbon nanotubes. Nature 2009, 460, 250-253.

7) Zhang, L.; Tu, X., Welsher, K.; Wang, X. ; Zheng, M.; Dai, H. Optical characterizations and electronic devices of nearly pure (10, 5) single-walled carbon nanotubes. J. Am. Chem. Soc. 2009, 131, 2454-2455.

8) Tu, X.; Zheng, M. A DNA-based approach to the carbon nanotube sorting problem. Nano Research 2008, 1, 185-194.

9) Zhang, L.; Zaric, S.; Tu, X.; Zhao, W.; Dai, H. Assessment of chemically separated carbon nanotubes for nanoelectronics. J. Am. Chem. Soc. 2008, 130, 2686-2691.

10) Li, X.; Tu, X.; Zaric, S.; Welsher, K.; Seo, W. S.; Zhao, W.; Dai, H. A novel Fe-Ru binary catalyst for selective growth of single-walled carbon nanotubes with narrow (n,m) chirality distributions. J. Am. Chem. Soc. 2007, 129, 15770-15771.

11) Tu, X.; Pehrsson, P. E.; Zhao, W. Redox reaction of DNA-encased HiPco carbon nanotubes with hydrogen peroxide: A near infrared optical sensitivity and kinetic study. J. Phys. Chem. C. 2007, 111, 17227-17231.



Guest Researcher
Complex Fluids

Employment History:

2008-2009: Postdoctoral Associate, DuPont Central Research & Development, Wilmington, DE

2009-present: Guest Researcher, Polymers Division, NIST


Ph.D., Applied Chemistry, University of Arkansas at Little Rock, 2007

B.S., Chemistry, University of Arkansas at Little Rock, 2002


Phone: 301-975-4349
Fax: 301-975-4924