Self-Assembly of Gold Nanoclusters into a Metal–Organic Framework with Efficient Electrochemiluminescence and Their Application for Sensitive Detection of Rutin

Abstract

Ligand-protected gold nanoclusters (Au NCs) are promising electrochemiluminescence (ECL) emitters because of their striking optical properties and excellent biocompatibility, but free vibration and rotation of their ligand result in low ECL efficiency, dramatically limiting their applications. Herein, using the ligand of Au NCs as one of the building units, a Au NC-based metal–organic framework (Au NC-based MOF) was constructed by the coordination-assisted self-assembly strategy, which not only impedes the ligand rotation-induced energy dissipation but also diminishes the self-quenching effect due to the spatial distribution of Au NCs. As a proof of concept, the prepared GSH-Au NCs@ZIF-8 gives rise to a 10-fold enhanced anodic ECL efficiency compared to that of densely aggregated GSH-Au NCs with triethylamine as the coreactant. Based on high ECL efficiency of GSH-Au NCs@ZIF-8, a “signal off” sensing platform was proposed with rutin as a model analyte, achieving a low detection limit of 10 nM. Therefore, the strategy paves an effective and alternative methodology to enhance ECL efficiency of metal NCs, considerably broadening their potential applications in sensing analysis, clinical diagnosis, and light-emitting devices.

Metal–Organic Frameworks-Mediated Assembly of Gold Nanoclusters for Sensing Applications

“…Upon coordination-assisted self-assembly, the porous structure of MOFs can not only enhance the electrochemical excitation and reduce the self-quenching effect of AuNCs, but also restrain the energy dissipation triggered by rotation and vibration of ligand to impede nonradiative transition of AuNCs as well. These features endow MOF/AuNCs assemblies with enhanced ECL efficiency which is favorable for ECL sensing [ 72 , 73 ].…”

“…Yuan et al [ 72 ] first reported the outstanding anodic ECL performance of GSH–AuNCs@ZIF-8 in the presence of coreactant (triethylamine, TEA), where the ECL intensity of GSH–AuNCs@ZIF-8 was increased to nearly ten times that of AuNCs (Fig. 9 ).…”

“…The remarkable performance of MOFs inspired their integration with AuNCs, which endowed the MOFs-mediated AuNCs assemblies (MOF/AuNCs assemblies) with enhanced selectivity, sensitivity, regenerability, and recyclability for sensing. MOF/AuNCs assemblies, possessing distinct advantages compared to other reported AuNCs-based nanocomposites due to the unique performance of MOFs [ 12 , 77 ], have been proved to be a powerful analytical platform for luminescence sensing [ 65 – 69 ], colorimetric sensing [ 70 , 71 ], electrochemiluminescence sensing [ 72 , 73 ], and (photo)electrochemical sensing [ 74 – 76 ] (Fig. 1 ).…”

Atomically precise metal nanoclusters meet metal-organic frameworks

“…This method is adaptable for other NCs with different ligands such as Au 38 (PET) 24 and Au 44 (2,4-DMBT) 26 . In another study, Yuan and co-workers used the ligand of NCs as one of the building units of MOFs to impede the ligand swinging of NCs ( Nie et al., 2021 ). Glutathione (GSH) protected Au NCs (GS-Au NCs) were encapsulated into ZIF-8 to construct the GS-Au NCs@ZIF-8 composite, where Zn 2+ coordinates with both the carboxyl group in the GSH ligand and the nitrogen atom of 2-methylimidazole linkers ( Figure 6 D).…”

“… (F) Corresponding calibration curve for the rutin determination. Reproduced with permission from Nie et al. (2021) .…”