Healable, Phase-Selective, and White-Light-Emitting Titania Based Hybrid Lanthanide-Doped Metallogels

Self-healing and tough gels with intriguing white-light emission, prepared by lanthanide metal ions, are highly desirable and remain a challenging topic. In this study, we present the preparation of a hybrid gel that contains poly(methyl methacrylate)/polyacrylic acid (PMMA/PAA) as the organic network and titania as the inorganic network, which are interpenetrating and linked by lanthanide metal ions. Interestingly, the gelation process for the organic phase allows for the efficient phase separation of the water-THF mixture (separation efficiency: >88%), either by the heating-cooling process or by the room temperature gelation that originated from xerogels. The as-prepared gels are self-healing and robust, based on the hybrid networks and dynamic coordination interactions. Specifically, the hybrid gels exhibit various colors of luminescence, depending on either the stoichiometric ratio of Eu³⁺ and Tb³⁺ or the excitation wavelengths. Upon excitation by the 365 nm light, the hybrid gel with Eu³⁺/Tb³⁺ ions (molar ratio 1:30) demonstrates a white-light emission color. The results also show that the gels prepared by only Eu³⁺ and Tb³⁺ possess different morphologies, surface areas, and contact angles. This work presents, for the first time, the crucial role of lanthanide ions for preparing a robust, self-healing hybrid gel with interpenetrating networks in the polymerization process, and the resulting hydrophobic surfaces are related to the phase-selective ability of the gels.