Assembling metal nanoclusters with high luminescence performance and anti-interference ability for sensing p-nitrophenol

Background

The fluorescence quantum yield (QY) of water-soluble gold nanoclusters (AuNCs) can be prominently improved by adding L-arginine (Arg) owing to rigidifying ligands. However, these fluorescence systems exhibit poor anti-interference ability in sensing application due to exposure guanidine, amino, and carboxyl groups of Arg.

Results

We have developed the encapsulation of AuNCs into zeolitic imidazolate framework-8 (ZIF-8) to improve the anti-interference property due to the protection of Arg functional groups. The ligand of 6-aza-2-thiothymine (ATT)-decorated AuNCs (ATT-AuNCs) is rigidified after introducing Arg (referred as Arg/ATT-AuNCs), yielding higher QY of 59.31% compared to ATT-AuNCs with QY of 1.18%. Subsequently, the shell of Arg/ATT-AuNCs encapsulated into ZIF-8 (Arg/ATT-AuNCs@ZIF-8) does not only tremendously increase green fluorescence emission, but also enhance the anti-interference capability (high salt concentration, pH change, metal ions coordination, and solution dilution) due to the structural confinement effect and protection of ligand functional groups. Interestingly, Arg/ATT-AuNCs@ZIF-8 fluorescence can be quenched by p-nitrophenol (PNP) through an internal filtration effect (IFE). Thus, a fluorescence method is established for PNP analysis. The linear detection range for PNP is 0.1 to 80 μM with limit of detection (LOD) at 0.033 μM, which is much lower than the maximum allowable value (0.43 μM) in drinking water by EPA. This approach has been successfully applied to the detection of PNP spiked into the real samples with excellent recovery rates. This platform opens a broad avenue for metal nanocluster-based materials in the sensing application.