Grafting Behavior of Amine Ligands for Surface Modification of MXene

Surface modification to improve the oxidation stability and dispersibility of MXene in diverse organic media is a facile strategy for broadening its application. Among the various ligands that can be grafted on the MXene surface, oleylamine (OAm), with amine functionalities, is an advantageous candidate owing to its strong interactions and commercial viability. OAms are grafted onto MXene through covalent bonds induced by nucleophilic reactions and H bonds in liquid interface reactions at room temperature. In addition, this grafting behavior of the ligand was characterized by a reduction in the slope with an increase in the ligand concentration (C_l), confirming that the OAms were grafted via Langmuir-like behavior, and the monolayer of OAms was developed via two distinct steps (I: lying-down phase; II: ordered monolayer). MXene nanosheets modified by OAm (OAm-MX) are highly dispersible in a wide range of organic solvents owing to the alkyl chain of the OAms, which induces hydrophobic properties on the surface of MXene. The OAm-MX dispersion exhibits outstanding oxidation and dispersion stability and remarkable coating performance on a wide range of substrates owing to their excellent solution processability. Therefore, this study provides fundamental insights into the adsorption behavior and interaction between amine ligands and MXene nanosheets for the surface chemistry of MXene.