Exploration of the specific structural characteristics of thiol-modified single-stranded DNA self-assembled monolayers on gold by a simple model

Abstract

This paper proposed a simple hexagonal model to explore the specific structural characteristics of thiol-modified single-stranded DNA (ss-DNA) self-assembled monolayers (SAMs) on gold substrate. The calibrated gyration diameter d ′ g ( d ′ g = r d g ) was used to quantify the size of ss-DNA molecules on gold by introducing a calibrating factor r, where d g was ss-DNA gyration diameter in solution. Based on the model, the interfacial parameters of ss-DNA-SAMs on gold assembled under different ionic strength were obtained theoretically. The ss-DNA-SAMs were assembled on gold under different concentrations of C NaCl and six important electrochemical parameters were used to validate the model experimentally, which include surface coverage ( Γ m), interfacial capacitance ( C), phase angle ( Ф 1 Hz ), ions transfer resistance ( R it * ), current density difference (Δ j) and charge transfer resistance ( R ct) from chronocoulometry ( CC), cyclic voltammetry ( CV) and electrochemical impedance spectroscopy ( EIS). Three main aspects were included in this paper: (1) construction of a simple hexagonal model to describe the specific structural characteristics of ss-DNA-SAMs on gold; (2) calculation of the calibrating factor r by CC experiments and several important conclusions from the simple model; and (3) confirmation of the simple model by our experimental results and literature reports. The simple model may provide an important reference for optimizing the design of DNA sensor.