Role of order in the mechanism of charge transport across single-stranded and double-stranded DNA monolayers in tunnel junctions

Nipun Kumar Gupta, Edward A Wilkinson, Senthil Kumar Karuppannan, Lily Bailey, Ayelet Vilan, Ziyu Zhang, Dong-Chen Qi, Anton Tadich, Eimer M Tuite, Andrew R Pike, James H R Tucker, Christian A Nijhuis

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Abstract

Deoxyribonucleic acid (DNA) has been hypothesized to act as a molecular wire due to the presence of an extended π-stack between base pairs, but the factors that are detrimental in the mechanism of charge transport (CT) across tunnel junctions with DNA are still unclear. Here we systematically investigate CT across dense DNA monolayers in large-area biomolecular tunnel junctions to determine when intrachain or interchain CT dominates and under which conditions the mechanism of CT becomes thermally activated. In our junctions, double-stranded DNA (dsDNA) is 30-fold more conductive than single-stranded DNA (ssDNA). The main reason for this large change in conductivity is that dsDNA forms ordered monolayers where intrachain tunneling dominates, resulting in high CT rates. By varying the temperature T and the length of the DNA fragments in the junctions, which determines the tunneling distance, we reveal a complex interplay between T, the length of DNA, and structural order on the mechanism of charge transport. Both the increase in the tunneling distance and the decrease in structural order result in a change in the mechanism of CT from coherent tunneling to incoherent tunneling (hopping). Our results highlight the importance of the interplay between structural order, tunneling distance, and temperature on the CT mechanism across DNA in molecular junctions.

Original languageEnglish
Pages (from-to)20309-20319
Number of pages11
JournalJournal of the American Chemical Society
Volume143
Issue number48
Early online date26 Nov 2021
DOIs
Publication statusPublished - 8 Dec 2021

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