Self-Healable Lanthanoid-Based Metallogels: Dye Removal and Crystallization in the Confined Gel State

Abstract

The self-healing property of metallogels resembles the innate self-healing of plant and animal biomaterials, making metallogels potential candidates for detailed studies. Tetrazoles with diverse coordination abilities and extensive H-bond formation capabilities may be able to be used as ligands to generate metallogels. In this report, four metallogels (M1G6Cl, M2G6Cl, M1G6NO3, and M3G6NO3) based on different lanthanoids and functionalized with di(1H-tetrazole-5-yl)methane (H2G6) are designed and fabricated. All the metallogels are well characterized by different spectroscopic methods. The mechanical strengths of the metallogels are determined by rheology, and FE-SEM images reveal diverse needle-like morphologies of the metallogels after the formation of ordered self-assembled networks. All the metallogels are found to be photoluminescent in nature, with quantum yields falling in the range 0.75-0.12. The emissive nature of the gels is utilized to perform invisible photopatterning experiments, which show the potential of these metallogels to be used in confidential image or writing applications. Furthermore, the crystallization of the M3G6NO3 metallogel in a confined gel space provides a pathway of elucidating its structure, which can be used to help predict the kinds of noncovalent interactions involved in the ordered self-assembly process. The self-healing nature of the M1G6Cl metallogels makes them the most interesting among all the gels and is further explored by the rhodamine dye-doped approach. Moreover, the low molecular weight, self-healable M1G6Cl metallogels act as unique soft materials for water purification by absorbing 98% Rhodamine B dye from water in 24 h. Copyright © 2019 American Chemical Society.