“Clickable” Metal-Oxide Nanomaterials Surface-Engineered by Gas-Phase Covalent Functionalization with Prop-2-ynoic Acid

Abstract

The surface properties of metal-oxide nanomaterials (MONMs) can be tuned by reacting them with a variety of organic compounds. Reactions of the oxides with functionalized carboxylic (R–COOH) or phosphonic acids (R–PO(OH)2) and various approaches utilizing silylation (such as with R–Si(X)3, where the X could be Cl or −OCH3) are often used to deliver the target modifier R to the oxide surface. However, the liquid-phase reactions between metal oxides and these agents often cause agglomeration or multilayer growth, morphology change, or surface etching. In this paper, we report a novel approach that circumvents all of these problems. The proposed two-step functionalization approach utilizes exposure of the oxide materials to prop-2-ynoic acid (HC≡C–COOH, propiolic acid) in the gas phase as a first step. The second step can then utilize the created C≡C for post-modification that introduces any predesigned functionality to the surface via “click” chemistry with azides (R–N3). Gas-phase exposure of prop-2-ynoic ...