Selective modification of layered silicate nanoparticle edges with fluorophores

The modification of two synthetic layered silicates, fluorohectorite (Corning) and laponite (Laporte), with two reactive silanes functionalized with fluorescent rhodamine or naphthalimide led to the grafting of the silicate particles selectively at the particle edges. The small amounts of grafted silanes were neither detected by infrared spectra nor X-ray diffraction (XRD) patterns. The larger extent of modification with cationic rhodamine-based silane was detected by XRD. The absorption and fluorescence spectra of the colloids of grafted silicates were similar to those of silane-dye precursors. Confocal fluorescence microscopy and fluorescence lifetime imaging detected the fluorohectorite-naphthalimide monolayer films to be optically heterogeneous, which was attributed to the selective location of the bound naphthalimide moieties at the particle edges.