Electrochemically Triggered Assembly of Films: A One-Pot Morphogen-Driven Buildup

摘要

Self-assembly plays a,central role in biology and modern chemistry. Except for self-assembled monolayers self-organized structures obtained by mixing interacting species are mainly observed in the bulk phase. Self-assembly taking place exclusively on surfaces and leading to films extending over the monolayer represents a real challenge. The main difficulty is the spontaneous and rapid interaction between the molecules as soon as they are mixed in solution. This can be circumvented by using different strategies, such as step-by-step deposition or simultaneously spraying of the interacting species on the substrate. In nature, biomineralization processes overcome the propensity of the different molecules to interact spontaneously by heterogeneous nucleation initiated by specific proteins. At a higher structural level, formation of complex tissue morphologies is driven by morphogenetic fields. These fields arise from the formation of gradients through production and diffusion of morphogens. According to Potter, morphogens are specific molecules to which cells respond in a concentration-dependent manner. This definition can be extended to the formation of films on a substrate; the buildup of the film is triggered by the presence of molecules or ions, the morphogens, generated at or attracted by the substrate. A first example of morphogenetic self-assembly was recently introduced by Melosh and co-workers. They described a dynamic polymerization of actin filaments from an electrode surface through ionic activation. This activation was obtained by diffusion of Mg~(2+) ions towards the electrode under the establishment of an electric double layer.