Luminescence Enhancement after Adding Organic Salts to Nanohybrid under Aqueous Condition

Lanthanide-based organic–inorganic hybrid materials (LnOIH) are of immense importance for various applications nowadays, while it still remains a significant challenge to achieve high luminescence efficiency in aqueous environment. Herein we present a simple and environmentally friendly two-step strategy to prepare strongly red-light emitting nano-LnOIH by first in situ forming Eu³⁺-β-dikeonate complexes on Laponite platelets and subsequently increasing the coordination number of the complexes via the modification with a silane-functionalized imidazolium salt, which can fully protect Eu³⁺ ions from the water molecule quenching. The mechanism of how the imidazolium salt favors the formation of Eu³⁺-β-dikeonate complex with large coordination number was elucidated. The result is that the removal of the abundant protons on the Laponite platelets through a mechanism of synergic effect of ion exchange and neutralization drives the formation of Eu³⁺-β-diketonate complexes with high coordination number. The high efficiency of the resulting luminescent nano-LnOIH in water endows the nanohybrid with good aqueous solution processability and opens the possibility of using them under complicated aqueous conditions for biorelated applications