Interfacial Chemistry Control of In Situ Grown Gold Nanoparticles on Functionalized MXene Nanosheets

The nucleation and growth of Au nanoparticles (NPs) on Ti 3 C 2 T x MXene nanosheets via in situ self‐reduction in aqueous media is an accessible route to heterostructures, yet reliable device integration demands precise control over the reduction process. In this study, MXene‐Au hybrids are systematically developed utilizing pristine and chemically functionalized MXene surfaces to direct Au NPs growth at the interface. Surface modifications that suppress hydrolysis while preserving productive Au growth are identified, providing control over nanoparticle size distributions, coverage, and clustering. MXene flakes are functionalized with potassium hydroxide (KOH), cysteamine, dopamine (DOPA), and (3‐aminopropyl)triethoxysilane (APTES) to tune surface oxidation and ligand chemistry, modifying gold growth. Across all chemistries, Au preferentially nucleates at oxidized sites, forming Au─O─Ti bonding. Functionalization is critical to mediate reduction kinetics and to control nanoparticle coarsening and coalescence, behaviors not accessible on pristine MXene. A critical partial‐oxidation window, quantified by the Ti 3 ⁺/TiO 2 X‐ray photoelectron spectroscopy (XPS) descriptor, is introduced, in which MXene is protected from hydrolytic degradation yet enables dense Au nucleation. Hybrids that synergize MXene's conductivity with gold's plasmonic properties may be useful in catalysis and optical sensing, while understanding the interfacial chemistry underlies performance in biosensing, bioimaging, photothermal therapy, and energy storage.