Dual-Shell-Solidified Gold Nanoclusters-Based Electrochemiluminescence Sensing Platform for Highly Selective and Sensitive Detection of Cu²⁺ and Histidine

Electrochemiluminescence (ECL) is rapidly emerging as an excellent electrochemical analytical technique for the specific and sensitive detection of various biomarkers and hazardous trace metals. Among ECL emitters, gold nanoclusters (AuNCs) have proven to be excellent luminophores due to their remarkable luminescent properties, stability, and biocompatibility. However, the low ECL efficiency of AuNCs precludes their application in ultrasensitive biosensing. One of the key reasons for the low ECL efficiency of AuNCs is the nonradiative energy transitions arising from intramolecular vibrations and rotations of the ligands on the surface of AuNCs. Herein, we explore the ECL of Zn2+/Au22(SG)18/PDA nanoclusters (NCs), where Zn2+ and 2,6-pyridinedicarboxaldehyde (PDA) activate the restriction of intramolecular motion (RIM) through aggregation-induced emission (AIE) to aggregation-induced enhanced emission (AIEE). This effect is achieved via cross-linking of Zn2+ and PDA with glutathione on the surface of Au22(SG)18, resulting in a significant enhancement of ECL emission compared to Au22(SG)18 NCs alone. A sensitive ECL sensing system was devised with Zn2+/Au22(SG)18/PDA as the ECL emitter, with triethylamine (TEA) as the coreactant, for the detection of Cu2+ and histidine in the linear ranges of 0.1 to 40 μM and 1 to 85 μM, respectively, with detection limits of 0.705 and 1.928 μM, respectively.