Abstract
Self‐assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e‐SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential‐assisted formed SAMs by X‐ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential‐assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate.
Highlights
Introduction qualityself-assembled monolayers (SAMs).[12,13] This argument is supported by the notion that adsorption of thiols progresses through a one electron reaction, in which the sulphur donates an electron to the surface adsorbed gold atom, with a positive potential applied to the gold assisting this process.[13]
An STM study into the adsorption of L-cysteine in acidified aqueous media found that higher quality SAMs were formed at positive potentials, compared to negative potentials,[15] with a different study finding that negative applied potentials of different magnitudes had no effect on the adsorption kinetics of cysteine.[16]
We addressed the question, whether an electrical potential during oligopeptide SAM formation can influence the adsorption properties of this class of novel, charged oligopeptides
Summary
SAM.[12,13] This argument is supported by the notion that adsorption of thiols progresses through a one electron reaction, in which the sulphur donates an electron to the surface adsorbed gold atom, with a positive potential applied to the gold assisting this process.[13] Recent work, has shown that application of either a positive or negative potential did not appear to improve the packing density of a thiol with a terminating ferrocenyl group.[14] Care, must be taken when attempting to draw global conclusions on SAM formation based upon formation studies within different solutions, as the solvent polarity and the organosulphur solubility affect the SAM quality.[14] An STM study into the adsorption of L-cysteine in acidified aqueous media found that higher quality SAMs were formed at positive potentials, compared to negative potentials,[15] with a different study finding that negative applied potentials of different magnitudes had no effect on the adsorption kinetics of cysteine.[16] The differing conclusions show that this reasonably simple interaction is still poorly understood, with better understanding vital to the development of self-assembled chemical sensors
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