Glutathione-protected fluorescent gold nanoclusters for sensitive and selective detection of Cu~(2+)

摘要

We report a novel and environmentally friendly fluorescent probe for detecting copper ion (Cu~(2+)) using glutathione (GS)-protected Au nanoclusters (GS-Au NCs). The fluorescence-based sensing behavior by GS-Au NCs toward metal ions was investigated in buffered aqueous media. Among the metal ions studied, Cu~(2+), Hg~(2+) and Pb~(2+) were found to efficiently quench the fluorescence emission of GS-Au NCs. In differentiation of Cu~(2+) and Hg~(2+) (or Pb~(2+)), we found that (1) in the presence of Pb~(2+), the GS-Au NCs solution first appeared turbidity, but with ethylenediaminetetraacetate (EDTA) added to the solution, the fluorescence recovered and the turbidity disappeared; (2) in the presence of Hg~(2+), EDTA could not recover the quenched fluorescence of GS-Au CNs by Hg~(2+), which is in contrast with Pb~(2+) and Cu~(2+). The Cu~(2+) detection limit was determined to be approximately 86 nM based on the fluorescence quenching and linear fluorescence response in the Cu~(2+) concentration range 1.00 × 10~(-7) to 6.25 × 10~(-6) mol/L. The high sensitivity of 86 nM Cu~(2+) and selectivity to Cu~(2+) among 17 types of metal cations make GS-Au NCs a good candidate for fluorescent sensors for Cu~(2+).