11-Mercaptoundecanoic acid capped gold nanoclusters with unusual aggregation-enhanced emission for selective fluorometric hydrogen sulfide determination

In present study, we discovered unusual solvent-mediated aggregation-enhanced emission (AEE) character of 11-mercaptoundecanoic acid capped gold nanoclusters (MUA-Au NCs). When aggregated in aqueous media, the MUA-Au NCs showed strong emission, which was weakened by adding ethanol. Interestingly, the suppressed emission was selectively enhanced in the presence of hydrogen sulfide (H₂S) because H₂S was absorbed onto Au NCs through the strong sulfur-gold bonding affinity. The hydrolyzed H₂S, namely, HS⁻, made the Au NCs negatively charged, which aggregated again due to decreased solubility. The H₂S-mediated fluorescence enhancement can be further amplified by introducing a hydrophilic thiolate (glutathione, GSH) onto the surface of Au NCs (GSH/MUA-Au NCs), which enabled sensitive determination of H₂S. Under the optimized condition, a detection limit of 35 nM was achieved. The determination was not interfered by other anions such as F⁻, Cl⁻, Br⁻, I⁻, OAc⁻, N₃ ⁻, NO₃ ⁻, HCO₃ ⁻, SCN⁻, SO₃ ²⁻, and SO₄ ²⁻. This excellent sensing performance allowed practical application of the GSH/MUA-Au NC-based sensing platform to accurate determination of H₂S in human serum samples. [Figure not available: see fulltext.].