Electron Transfer Processes in Ferrocene-Modified Poly(ethylene glycol) Monolayers on Electrodes.

Electrochemistry is a powerful tool to study self-assembled monolayers. Here, we modified cystamine-functionalized electrodes with different lengths of linear poly(ethylene glycol) (PEG) polymers end-functionalized with a redox-active ferrocene (Fc) group. The electron transport properties of the Fc probes were studied using cyclic voltammetry.

Electron-Transfer Rates in Host-Guest Assemblies at β-Cyclodextrin Monolayers.

The effect of the distance between a β-cyclodextrin (βCD) host core and a conductive substrate on the electron-transfer rate of complexed guests as well as of free-diffusing electrochemically active probes has been studied. First we have evaluated a set of short-tethered βCD adsorbates bearing different anchoring groups in order to get a reliable platform for the study of short-distance electron transfer. An electrochemically active trivalent guest was immobilized on these host monolayers in a selective and reversible manner, providing information about the packing density.

Electron Transfer Mediated by Surface-Tethered Redox Groups in Nanofluidic Devices.

Electrochemistry provides a powerful sensor transduction and amplification mechanism that is highly suited for use in integrated, massively parallelized assays. Here, the cyclic voltammetric detection of flexible, linear poly(ethylene glycol) polymers is demonstrated, which have been functionalized with redox-active ferrocene (Fc) moieties and surface-tethered inside a nanofluidic device consisting of two microscale electrodes separated by a gap of <100 nm. Diffusion of the surface-bound polymer chains in the aqueous electrolyte allows the redox groups to repeatedly shuttle electrons from one electrode to the other, resulting in a greatly amplified steady-state electrical current.

Self-assembled monolayers on gold of β-cyclodextrin adsorbates with different anchoring groups.

We designed multivalent β-cyclodextrin-based adsorbates bearing different anchoring groups aiming to yield stable monolayers with improved packing and close contact of the cavity to the gold surface. Toward this end the primary rim of the β-cyclodextrin was decorated with several functional groups, namely iodide, nitrile, amine, isothiocyanate, methyl sulfide, and isocyanide. Monolayers formed by these adsorbates were characterized by contact angle measurements, surface plasmon resonance spectroscopy, polarization modulation infrared reflection adsorption spectroscopy, X-ray photoelectron spectroscopy, and electrochemistry.