Ligand-Driven Supramolecular Assembly of Gold Nanoclusters with Ultralong Lifetime and Large Stokes Shift for High-Efficiency Electrochemiluminescence.

Abstract

Achieving high-efficiency electrochemiluminescence (ECL) with an ultralong lifetime and a large Stokes shift in a single emitter is highly desirable yet challenging. Herein, we report the supramolecular assembly of gold nanoclusters (Au NCs) protected by a custom-designed ligand, 1-(4-carboxyphenyl)-5-mercapto-1H-tetrazole (CPMT), which achieved the aforementioned outstanding performance. The CPMT ligand not only stabilized the Au NCs through bidentate Au-S/Au-N coordination, but also induced supramolecular assembly via intermolecular π-π interactions and hydrogen bonding. The obtained self-assembled CPMT-Au NCs exhibited an exceptionally long ECL lifetime of 60.48 μs, since their rigid spherical superstructure effectively minimized interfacial nonradiative decay, leading to an intrinsically prolonged excited-state lifetime, and passivated the emissive cores against oxygen quenching, preserving the long-lived emission under ambient conditions. Concurrently, the assembly showcased a remarkably large Stokes shift of 490 nm, which virtually eliminated self-absorption even in the solid state. The assembled CPMT-Au NCs displayed dramatically enhanced ECL efficiency of 353.37%, a 15-fold enhancement over their nonassembled counterparts, attributable to the synergistic suppression of interfacial energy dissipation and self-absorption as well as the improved electrochemical excitation. Additionally, a sensitive sensing platform for carboxylesterase (CE) activity related to early hepatocellular carcinoma was developed with a detection limit of 1.98 × 10-7 U/L. Therefore, this work establishes supramolecular assembly driven by ligand engineering as a rational platform for regulating the excited-state properties of metal nanoclusters, opening new avenues for high-performance ECL emitters in lifetime-based sensing, high-brightness devices, and multiplexed bioassays.