Lanthanide(III)-Based Multicolor Luminescent Hybrid Gel for Amine Sensing

Bridged polysilsesquioxanes (BPs) show great potential in the development of lanthanide-based luminescent materials, owing to their capacity to loading lanthanide complexes with high concentration and their flexible processability. A novel BP precursor, consisting of a C₃ -symmetrical benzene central core moiety, capable of sensitizing the luminescence of Eu³⁺ and Tb³⁺ is reported. Tunable, full-color luminescent gels were facilely prepared by mixing the as-synthesized precursor and Ln³⁺ ions in appropriate solvents. By either changing the Eu³⁺ /Tb³⁺ molar ratio or altering the excitation wavelength, the emission colors of the final gels can be finely tuned. Additionally, the yellow-colored emissive gel with a molar ratio of Eu³⁺ to Tb³⁺ of 0.5 can be used as an effective ratiometric luminescent sensor for distinguishing amines with lower pK_a (<5) from those with higher pK_a (>9).