Water-dispersible and stable fluorescent Maya Blue-like pigments

Abstract

Poor water-dispersibility and stability of hydrophobic fluorescent organic pigments (HFOPs) hinder many of their applications. Inspired by the excellent stability of Maya Blue pigments and the water solubility of LAPONITE® RD (LRD), we report the facile synthesis of water-dispersible and stable fluorescent Maya Blue-like pigments via the host–guest interaction between LRD and Pigment Red 31 (PR 31), a representative HFOP. The concentration of LRD and solid-state grinding play important roles in effectively dispersing PR 31 into the aqueous solution. The interactions between PR 31 and LRD involve van der Waals, π–π, electrostatic, hydrogen bonding between phenolic hydroxyl groups of PR 31 and silanols of LRD as well as dye–dye hydrophobic interactions. The interactions between PR 31 and LRD occur on the external surface of LRD and the entrance of the micropores of LRD, however, the PR 31 molecules cannot intercalate into the layers of LRD plates. The so-obtained pigments are highly water-dispersible, and very stable to thermal aging and UV irradiation owing to the interactions between LRD and PR 31, and the shielding effect of LRD.