Journal
NANOSCALE
Volume 10, Issue 39, Pages 18586-18596Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c8nr06150e
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Funding
- National Natural Science Foundation of China [21525418, 21474041, 91127031]
- National Basic Research Program [2013CB834503]
- Program for New Century Excellent Talents in University [NCET-11-0205]
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Complexation of single-stranded DNA (ssDNA) with a chiral single-walled carbon nanotube (SWCNT) exhibits surprising efficacy in CNT dispersion and sorting, optical sensing, and nanoelectronic device design. Studying the wrapping/unwrapping mechanism is challenging because an in situ method at the single-molecule level is required. Here, we developed a method based on single-molecule force spectroscopy to monitor the unwrapping/wrapping of ssDNA from/around a SWCNT. Our results reveal that the wrapping/unwrapping processes are reversible in water, and these processes occur in an equilibrium manner driven mainly by pi-pi interactions between DNA bases and CNTs. In phosphate buffered saline, the unwrapping process is loading rate-dependent, and ssDNA wrapping around a CNT undergoes two distinct stages dominated by both pi-pi interactions and hydrogen bonding. In addition, our results show that salts could further stabilize ssDNA/CNT complexes by blocking the electrostatic interactions between adjacent DNA segments and by catalyzing the formation of hydrogen bonds between DNA bases. The stability of ssDNA/CNT is dependent on the DNA sequence and CNT chirality. These results deepen our understanding of ssDNA-CNT interactions and provide effective means to tune the binding mode and strength.
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