Photoactive hybrid material based on kaolinite intercalated with a reactive fluorescent silane

Abstract

The main strategies to modify layered silicates with dyes have been based on ion exchange reactions. In this work, the modification was performed via the chemisorption of reactive rhodamine on the surface of kaolinite (Kaol) particles. The reactive dye (RhAptes) was synthesized via the reaction of rhodamine B (RhB) with 3-aminopropyl-triethoxy silane. Efficient modification of the Kaol surface was achieved after the pre-expansion of its structure with dimethyl sulfoxide. RhAptes reacted with the hydroxyl groups of the expanded mineral. The structural characteristics and optical properties of the hybrid material (Kaol-RhAptes) were characterized by X-ray diffraction and spectroscopy in the visible region. Absorption and fluorescence spectra of Kaol-RhAptes were similar to its dye precursors, RhB and RhAptes. Time-resolved fluorescence spectra proved only minor molecular aggregation of bound rhodamine. Partial fluorescence quenching was confirmed by fluorescence quantum yield measurements. We assume that other materials based on Kaol intercalated with various photoactive molecules could be synthesized by the strategy used in this work. Modifications of kaolinite could lead to special materials and might expand their range of applications.