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.