One-Step Assembly of Coordination Complexes for Versatile Film and Particle Engineering

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Science  12 Jul 2013:
Vol. 341, Issue 6142, pp. 154-157
DOI: 10.1126/science.1237265

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One-Step Coverage

Controllable formation of thin films often requires slow deposition conditions or multiple rounds of coating. Ejima et al. (p. 154; see the Perspective by Bentley and Payne) report a simple and versatile method for coating surfaces with thin biocompatible films made from the condensation of Fe3+ ions and a natural polyphenol, tannic acid, from aqueous solutions. Flat surfaces, colloidal particles, and even bacterial cells could be coated, and the coats could subsequently be degraded by changing the pH.


The development of facile and versatile strategies for thin-film and particle engineering is of immense scientific interest. However, few methods can conformally coat substrates of different composition, size, shape, and structure. We report the one-step coating of various interfaces using coordination complexes of natural polyphenols and Fe(III) ions. Film formation is initiated by the adsorption of the polyphenol and directed by pH-dependent, multivalent coordination bonding. Aqueous deposition is performed on a range of planar as well as inorganic, organic, and biological particle templates, demonstrating an extremely rapid technique for producing structurally diverse, thin films and capsules that can disassemble. The ease, low cost, and scalability of the assembly process, combined with pH responsiveness and negligible cytotoxicity, makes these films potential candidates for biomedical and environmental applications.

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