Precision Ladder-Structured Silver Cluster Assembly Bridged by Tetrazine Linkers for Highly Sensitive and Selective Luminescence Recognition of Amino Acids

Abstract

Silver nanoclusters merge atomically defined structures with intense, environment-responsive photoluminescence, yet their notorious lability in air and water has constrained real-world sensing. Here we convert fragility into a design principle by immobilizing a silver nanocluster motif inside a reticularly reinforced, recognition-active lattice. TUS 9 is a ladder-structured silver cluster-assembled material built from bow-shaped Ag13 units that first organize into one-dimensional chains ("rails") and are then stitched laterally by rigid 3,6-di(4-pyridyl)-1,2,4,5-tetrazine linkers ("rungs"). Single-crystal X-ray diffraction reveals a monoclinic C2/c framework in which argentophilic contacts and a mixed thiolate/trifluoroacetate ligand shell stabilize the cluster scaffold, while directional Ag-N coordination locks interchain registry. Bulk phase fidelity is confirmed by PXRD and XPS, and the ordered packing generates permanent microporosity. In water, TUS 9 retains strong emission with a sensing-ready band at 377 nm (λex = 295 nm), enabling selective luminescence quenching by basic amino acids. L-lysine and L-arginine produce pronounced Stern-Volmer responses (KSV = 891.7 and 540.1 M⁻ 1 ) with detection limits of 407 and 162 μM, respectively, whereas acidic amino acids perturb the emission only weakly. The response is fully recyclable over 10 cycles and post-sensing XPS shows preserved coordination environments. This work demonstrates that electronically active linkers can simultaneously stabilize silver nanocluster frameworks against aqueous degradation and encode molecular selectivity, opening a modular route to robust, programmable luminescent sensors.