Recent Advances in Stimuli‐Responsive Luminescent Supramolecular Lanthanide‐Based Metallogels

Abstract

The use of lanthanide‐based metallogels presents a promising approach for the engineering of stimuli‐responsive gel materials. Stimuli‐responsive luminescent materials based on lanthanides have promising applications in bio‐applications and optical encoding. Synthetic supramolecular metallogels typically become kinetically trapped and usually do not exhibit time‐variable changes in their material properties. However, such supramolecular metallogels can switch between gel to sol when subjected to different external physical and chemical stimuli. This is because weak noncovalent interactions hold together the gel structure and are also influenced by the coordination dynamics of the metal‐ligand bond. This review summarizes recent research progress on stimuli‐responsive supramolecular lanthanide‐based luminescent metallogels. Chemical, physical, and multiple stimuli‐responsiveness of the metallogels are discussed elaborately based on the external stimulus sources. Finally, the latest challenges and opportunities for developing novel metallogels that respond to stimuli are discussed.

An acid-chromic luminescent lanthanide metallogel for time-dependent information encryption and anti-counterfeiting

“…H 3 L was chosen as the ligand to form the luminescent H 3 L/Tb 3+ gel due to its self-assembly ability 20,21 and its potential to sensitize Tb 3+ . 8,11 SR101 was selected as the energy acceptor because of its spectral overlap with the energy donor, enabling tuning of the emission color based on FRET platforms by adjusting the SR101 amount in the H 3 L/Tb 3+ gel. Considering that acid can inhibit the coordination of the carboxyl group with Tb 3+ and suppress the “antenna effect,” 8 we anticipated that the SR101-doped H 3 L/Tb 3+ gels would exhibit acid-chromic behavior.…”

“…8,11 SR101 was selected as the energy acceptor because of its spectral overlap with the energy donor, enabling tuning of the emission color based on FRET platforms by adjusting the SR101 amount in the H 3 L/Tb 3+ gel. Considering that acid can inhibit the coordination of the carboxyl group with Tb 3+ and suppress the “antenna effect,” 8 we anticipated that the SR101-doped H 3 L/Tb 3+ gels would exhibit acid-chromic behavior. The fluorescent peaks of Tb 3+ (green fluorescence) disappear after the addition of acid, leaving only the emission peaks of H 3 L (blue fluorescence) and/or partially quenched emission of SR101 (red fluorescence).…”

“…Lanthanide metallogels, driven by dynamic coordination interactions, π–π stacking, hydrogen bonding, van der Waals forces, or other intermolecular non-covalent interactions, offer distinct advantages in the realms of information encryption and anti-counterfeiting. 7–9 These advantages stem not only from their unique optical properties—long luminescence lifetimes, good monochromaticity, and large Stokes shifts—but also from their stimulus-responsive characteristics. 10,11…”