Electrodes are ideal substrates for surface localized self-assembly processes. Spatiotemporal control over such processes is generally directed through the release of ions generated by redox reactions occurring specifically at the electrode. The so-used gradients of ions proved their effectiveness over the last decade but are in essence limited to material-based electrodes, considerably reducing the scope of applications. Herein is described a strategy to enzymatically generate proton gradients from non-conductive surfaces. In the presence of oxygen, immobilization of glucose oxidase (GOx) on a multilayer film provides a flow of protons through enzymatic oxidation of glucose by GOx. The confined acidic environment located at the solid-liquid interface allows the self-assembly of Fmoc-AA-OH (Fmoc=fluorenylmethyloxycarbonyl and A=alanine) dipeptides into β-sheet nanofibers exclusively from and near the surface. In the absence of oxygen, a multilayer nanoreactor containing GOx and horseradish peroxidase (HRP) similarly induces Fmoc-AA-OH self-assembly.

Surface functionalization is an interesting way to elaborate new smart materials. In this work, a two-step surface modification, based on pulsed plasma polymerization, was used to design functional surfaces able to react by Diels−Alder reaction (a diene−dienophile cycloaddition). The reactivity of furan-functionalized (diene) surfaces with a maleimide-derivative (dienophile) was studied. The determination of the rate constants led to the determination of the activation energy, the enthalpy of activation, and the entropy of activation. These results were then compared to those obtained in solution. For the first time, it was possible to understand the role played by molecule confinement (close to the surface) on the Diels−Alder reactivity.

No abstract