2D Nanomaterial-Directed Molecular Aggregation and Energy Transfer between Edge-Bound Donor–Acceptor Pairs

Förster resonance energy transfer (FRET) is a phenomenon that is observed between an excited energy donor and ground-state acceptor in close proximity. The efficiency of FRET varies with the distance and orientation of the donor–acceptor pair, solvent, and other competing processes. Layered silicates, with their ability to stack in "pillars" with a certain interlayer spacing, present a useful platform to influence the interactions of edge-bound groups. In this study, asymmetric perylene and naphthalene diimides were grafted to the edge of the layered silicate Laponite, and their photophysical properties and aggregation behavior were studied in different compositions of water and dimethylformamide. FRET was observed from naphthalene diimide- to perylene diimide-functionalized Laponite, and pillaring of Laponite with a cationic surfactant led to significantly enhanced FRET, which was attributed to the reorientation of chromophores due to the organized stacking of pillared particles. This study reports how ordering of the discoidal layered silicate nanoparticles into organized stacks can tune the aggregation of edge-bound FRET pairs. This can aid in understanding donor–acceptor interactions at the interface of anisotropic nanomaterials and improve control over the distance and orientation of donor–acceptor pairs and resulting energy transfer processes. Furthermore, this is the first example of the attachment of naphthalene diimides to layered silicate edge sites. This study opens the door to further studies of geometry-dependent energy flows in inorganic–organic hybrid materials and will advance applications in sensing, energy, and molecular electronics.