Ferrocene heteroconjugation enables charge transport in DNA monolayers

DNA has emerged as a promising self-assembling material for molecular electronics. Here, we investigate the electrical response of double-stranded DNA (dsDNA) modified with a ferrocene-functionalised psoralen that forms a covalent cross-link at TA–AT sites. A thiol-modified 10-mer DNA conjugate self-assembles on Au substrates, enabling simultaneous mapping of surface topography and current distribution by conductive atomic force microscopy. Under the present experimental conditions, native dsDNA remained close to the current detection limit, whereas incorporation of ferrocene resulted in a measurable increase. Analysis of the current–voltage characteristics did not reveal a clear signature of a single dominant transport mechanism. At higher fields, the response was consistent with field-assisted charge injection across the molecular junction. These results indicate that ferrocene incorporation modifies the electronic response of the DNA assembly and influences charge transport across the molecular layer. This approach requires no pre-derivatisation of the DNA backbone and provides a versatile strategy for post-synthetic functionalisation. DNA is a promising self-assembling material for molecular electronics, but efficient charge injection remains challenging because of its deep HOMO energy level. Here, the authors develop a chemically defined DNA–ferrocene conjugate through covalent modification of a DNA duplex and demonstrate an enhanced electrical response. The resulting metal–DNA molecular junctions show how electronic functionality can be programmed by molecular design, providing a platform for quantitative comparison with theoretical models.