Charge transport in l-DNA probed by conducting-AFM, and relationship with its structure

TL;DR

This study investigates the electrical conductivity of l-DNA using conducting-AFM, revealing how the insulating gap varies with DNA bundle size and linking resistivity to DNA conformation on surfaces.

Contribution

It provides new insights into charge transport mechanisms in l-DNA and correlates structural conformation with electrical properties at the single-molecule level.

Findings

Insulating gap increases with fewer DNA molecules.

Hopping distance of ~3 nm consistent across samples.

Flattened DNA conformation correlates with high resistance.

Abstract

We studied the electrical conductivity of DNA samples as function of the number of DNA molecules. We showed that the insulating gap (no current at low voltage) increases from ~1-2 V for bundles and large ropes to ~4-7 V for few DNA molecules. From the distance dependent variation of the current, a unique hopping distance of ~3 nm is calculated (polaron-hopping model) independently of the number of DNA in the sample. The highly resistive behavior of the single DNA is correlated with its flattened conformation on the surface (reduced thickness, ~0.5-1.5 nm, compared to its nominal value, ~2 nm).