Electrotriggered Confined Self-assembly of Metal-Polyphenol Nanocoatings Using a Morphogenic Approach

Supramolecular metal-phenolic thin films attract an increasing interest since they allow the design of new types of self-assembling materials, such as tunable electronics or biomaterials. In this study, a new electrotriggered self-assembly of tannic acid-Fe(III) (TA-Fe(III)) nanocoatings was developed using the morphogenic approach with Fe(III) ions as a morphogen. Morphogens are molecules or ions produced locally that diffuse into the solution and induce a chemical reaction or interaction in a confined space near a surface. Using a mixture of TA and Fe(II) ions in contact with an electrode, a confined electrogenerated gradient of Fe(III) was obtained by application of an anodic current to locally form TA-Fe(III) coordination complexes. TA-Fe(III) nanocoatings, based on di- and tricoordinated complexes, were thus obtained. Both the film thickness and its self-assembly kinetics were tuned by controlling the Fe(II)/TA molar ratio of the building solution, the intensity, and the duration of the applied current. We showed that this strategy can be applied to two other polyphenols (gallic acid and rosmarinic acid). This new electrotriggered confined selfassembly of metal−polyphenol gives new perspectives in applications such as antioxidant coating.