Abstract
The covalent functionalization of graphene for enhancing their stability, improving their electrical or optical properties, or creating hybrid structures has continued to attract extensive attention; however, a fine control of nanoparticle (NP) size between graphene layers via covalent-bridging chemistry has not yet been explored. Herein, precision covalent chemistry-assisted sandwiching of ultrasmall gold nanoparticles (US-AuNP) between graphene layers is described for the first time. Covalently interconnected graphene (CIG) nanoscaffolds with a preadjusted finely tuned graphene layer-layer distance facilitated the formation of sandwiched US-AuNPs (∼1.94 ± 0.20 nm, 422 AuNPs). The elemental composition analysis by X-ray photoelectron spectroscopy displayed an aniline group addition per ∼55 graphene carbon atoms. It provided information on covalent interconnection via amidic linkages, while Raman spectroscopy offered evidence of covalent surface functionalization and the number of graphene layers (≤2-3 layers). High-resolution transmission electron microscopy images indicated a layer-layer distance of 2.04 nm, and low-angle X-ray diffraction peaks (2θ at 24.8 and 12.5°) supported a layer-layer distance increase compared to the characteristic (002) reflection (2θ at 26.5°). Combining covalent bridging with NP synthesis may provide precise control over the metal/metal oxide NP size and arrangement between 2D layered materials, unlocking new possibilities for advanced applications in energy storage, electrochemical shielding, and membranes.