Unconventional application of gold nanoclusters/Zn-MOF composite for fluorescence turn-on sensitive detection of zinc ion.

Contrary to organic solvent-induced aggregation of Au nanoclusters (AuNCs), herein, we reported aggregation induced emission enhancement (AIEE) of AuNCs in an aqueous media through confinement of AuNCs by in situ formed Zn-MOF for detecting Zn2+. Glutathione capped AuNCs (GSH-AuNCs) was synthesized through reduction of Au3+ by glutathione. Zn2+ could significantly enhance the fluorescence of GSH-AuNCs upon addition of 2-methylimidazole, which was attributed to the formation of Zn-MOF. XRD and TEM were used to characterize the in situ formed Zn-MOF. Zn2+ induced aggregation was demonstrated by dynamic light scattering and TEM. The quantum yields (QYs) of AuNCs after aggregation induced by in situ formed Zn-MOF attained to 36.6%, which was nearly 9 times that of the sole AuNCs. On this basis, a fluorogenic sensor was reported for Zn2+ detection with a linear range from 12.3 nM to 24.6 μM and a detection limit of 6 nM (S/N = 3). The proposed sensor was successfully applied to assay the content of zinc in human serum, milk, water, and zinc sulfate syrup oral solution samples. The novel strategy proposed in this work may open a new window of interest in an unconventional application of gold nanoclusters/MOF nanoscale platform for metal ion detection and nutritional assessment of food.