Han Seul Kim, Yong-Hoon Kim
Carbon nanomaterials represent promising nanoelectrode candidates in the emerging electron tunneling based DNA sequencing approach. Carrying out extensive first-principles calculations, we here show that two distinct DNA sequencing mechanisms can be achieved with different configurations of a single-type N-doped capped carbon nanotube (CNT) electrode that has significantly enhanced current magnitude and chemical sensitivity over its pristine counterpart. With a small CNT-CNT gap size that induces face-on nucleobase configurations, we obtain a typical conductance ordering where the largest signal is produced by guanine according to its highest occupied molecular orbital (HOMO) higher in energy than other bases. On the other hand, for a large CNT-CNT gap size that accommodates edge-on nucleobase configurations, we extract a completely different conductance ordering in which thymine provides the largest signal in spite of its small size and low HOMO level. We show that the latter novel nucleobase sensing mechanism reflects the chemical connectivity between N-doped CNT caps and nucleobase functional groups that include the hyperconjugated thymine methyl group. We thus demonstrate the feasibility of a tunneling-based dual-mode approach toward whole genome sequencing applications, detection of DNA base modifications, and single-molecule sensing in general.
View original:
http://arxiv.org/abs/1212.3148
No comments:
Post a Comment