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We have studied adsorption and electrochemical electron transfer of several 13- and 15-base DNA and UNA (unlocked nucleic acids) oligonucleotides (ONs) linked to Au(111)-electrode surfaces via a 50-C6-SH group using cyclic voltammetry (CV) and scanning tunnelling microscopy in aqueous buffer under electrochemical potential control (in situ STM). 2,20,60,200-Terpyridine (terpy) onto which the transition metal ions Fe2+/3+, Os2+/3+ and Ru2+/3+ could be coordinated after UNA monolayer formation was attached to UNA via a flexible linker. The metal centres offer CV probes and in situ STM contrast markers, and the flexible UNA/linker a potential binder for intercalation. CV of pure and mercaptohexanol diluted ON monolayers displayed reductive desorption signals but also, presumably capacitive, signals at higher potentials. Distinct voltammetric signals arise on metal binding. Those from Ru-binding are by far the
strongest and in accord with multiple site Ru-attachment. In situ STM disclosed molecular scale features in varying coverage on addition of the metal ions. The Ru-derivatives showed a bias voltage dependent broad maximum in the tunnelling current–overpotential correlation which could be correlated with theoretical frames for condensed matter conductivity of redox molecules. Together the data suggest that Ru-units are bound to both terpy and the UNA–DNA backbone.
Original languageEnglish
JournalPhysical Chemistry Chemical Physics
Issue number3
Pages (from-to)776-786
StatePublished - 2013

Bibliographical note

Electronic supplementary information (ESI) available: Details of the synthesis and purification of the ONs; MALDI-MS spectra of the oligonucleotides; tunnelling STS of the Ru-derivative of terpy 15-base ss DNA; formalism of STS bandwidth dependence of the ionic strength. See DOI: 10.1039/c2cp42351k

CitationsWeb of Science® Times Cited: 8
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ID: 15650432