Molecularly Smooth and Conformal Nanocoating by Amine-Mediated Redox Modulation of Catechol

Abstract

Conformal nanocoatings to nanostructured materials are key to the utilization of unique nanomaterial properties. Although catechol-based nanocoatings on flat substrates have been extensively reported, research on conformal coatings to nanomaterials with high curvature has rarely been conducted because cohesion is caused by the catechol oxidation. In the literature, amine-mediated redox control of a catechol system by separating catechol and amine is employed and an optimized nanocoating can be achieved by suppressed cohesion and enhanced adhesion. The amine-assisted catechol nanocoating exhibits roughness of <0.358 nm and thickness of 1.69 nm on flat substrates; the hydrodynamic diameter of coated iron oxide nanoparticles is less than 20 nm. Density functional theory calculations were performed to elucidate the coating mechanism, and three key roles of amine in the catechol-based nanocoating were discovered: adhesion promotion, suppression of polymerization, and additional stabilization through an in situ generated, newly designed catechol-amine adduct. The strategy provides insights into catechol-based nanocoating, and it has broad applications in fields that require nanoscale coating layers.