Multiresponsive Supramolecular Luminescent Hydrogels Based on a Nucleoside/Lanthanide Complex

Supramolecular luminescent hydrogels based on natural molecules have shown high potential for a variety of applications because of unique optical properties and biocompatibility, particularly serving as advanced biomaterials for bioimaging, biosensing, cell engineering, and so forth. A lanthanide complex-based system provides a promising way to prepare supramolecular luminescent hydrogels. Herein, we realize the creation of a luminescent hydrogel assembled from lanthanides and nucleosides. Nucleosides, the essential components of nucleic acids, functioning as the ligands, successfully chelate with lanthanides and form complexes in water. The complexes subsequently serve as building-blocks to form supramolecular hydrogels, which exhibit characteristic luminescent emission of lanthanides. The coordination modes and forming mechanism are studied by electrospray ionization time-of-flight mass spectrometry, matrix-assisted laser desorption/ionization time of flight mass spectrometry, 1H NMR spectroscopy, and Fourier transform infrared spectroscopy; the corresponding molecular simulations are presented, and macro-/micro-morphologies, mechanical properties, and luminescent performances of hydrogels are systemically studied. Remarkably, these luminescent hydrogels show fluorochromic properties in response to external stimuli, including pH, temperature, anions, and cations, which are thus adopted to design smart luminescent switches and detect specific species such as Cu2+. Our work provides a feasible strategy to prepare stimuli-responsive luminescent hydrogels, reveals the diverse potential of nucleoside-based hydrogels, and exhibits a novel pathway for the preparation of smart optical materials.