A Multifunctional Acylhydrazone Dendrimer: Efficient Light-Harvesting and Selective Cascade Detection of Zn2+ and Cysteine.

The construction of multifunctional luminescent platforms that seamlessly integrate efficient light harvesting, selective ion recognition, and biomolecule detection within a single molecular scaffold represents a compelling yet challenging frontier in materials science. To address this challenge, we have designed and synthesized a multifunctional fluorescent dendrimer, DAH-D1, based on a biphenyl-acylhydrazone core, which exhibits pronounced excited-state intramolecular proton transfer and aggregation-induced emission characteristics, along with a large Stokes shift. DAH-D1 spontaneously self-assembles into orange-emitting nanoparticles in aqueous media. These aggregates serve as efficient energy donors for constructing an artificial light-harvesting system through Förster resonance energy transfer upon co-assembly with the NDI-Bu acceptor, achieving a maximum energy transfer efficiency of up to 70% and thus demonstrating the excellent light-harvesting capability of this dendritic platform. Beyond photophysical functions, DAH-D1 serves as a highly selective fluorescent probe for Zn2+, showing a distinct "turn-on" response with a 38-fold fluorescence enhancement even in the presence of competing metal ions including Cd2+. Moreover, the in situ-generated DAH-D1-Zn complex enables the cascade detection of cysteine via a competitive demetallation mechanism, accompanied by a fluorescence "turn-off" response. Collectively, this work establishes a versatile dendritic platform that synergistically combines light harvesting, metal-ion sensing, and amino acid detection, offering a promising strategy for the construction of integrated luminescent materials with broad applicability in optoelectronics, environmental monitoring, and biochemical analysis.