Lanthanide-based metallogels with tunable luminescence: Nanomolar detection of a nerve agent simulant and anticounterfeiting applications

Abstract

This work presents two lanthanide-based metallogels, L1-Eu and L1-Tb, fabricated by coordination-driven self-assembly of an amide-based ligand containing a long alkyl chain (L1). The self-assembly of metallogels was investigated with the help of FTIR and NMR spectral, crystallographic, rheological, morphological, and molecular docking studies. These studies reveal a collective role of M-L coordination, π−π stacking, hydrogen bonding, and critical hydrophobic interactions amongst the alkyl chains in forming lanthanide-based metallogels. To evaluate the role of long alkyl chains in metallogel formation, several control molecules (L2 – L4) were synthesized by varying the length of the attached alkyl chain. Notably, the alkyl chain length significantly impacted not only the metallogel formation but also their mechanical strength. Both L1-Eu and L1-Tb unveiled distinct and strong luminescent characteristics ascribed to lanthanide ions. The luminescence properties of metallogels were tuned by modulating the stoichiometry of lanthanide ions, and red, green, and near-white light-emitting metallogels were developed. Both metallogels were utilized for the selective and nanomolar detection of dimethyl methyl phosphonate (DMMP), a nerve agent simulant, and noteworthy anticounterfeiting applications.