Nearly Monodisperse Copper Selenide Nanoparticles for Recognition, Enrichment, and Sensing of Mercury Ions

In the current work, Cu(I)1.28Cu(II)0.36Se nanoparticles were synthesized via a simple procedure and were applied for the first time for recognition, adsorption, enrichment, and detection of Hg(II) ions. The experimental results show that 99.9% Hg(II) could be adsorbed by Cu(I)1.28Cu(II)0.36Se nanoparticles within just 30 s, and the Hg(II) concentration could be lowered down to a super-low level of 0.01 ppb. Cu(I)1.28Cu(II)0.36Se nanoparticles also demonstrate high selectivity to Hg(II) and Ag(I) among nine representative metal ions. The enrichment experiments show that Hg(II) of ultratrace concentration could be enriched significantly by Cu(I)1.28Cu(II)0.36Se nanoparticles, and thus, the detection limit of Hg(II) based on inductively coupled plasma emission spectroscopy–mass spectrometry would be pushed down by 2 orders of magnitude. These outstanding features of Cu(I)1.28Cu(II)0.36Se nanoparticles could be well accounted for in terms of the solubility product principle and the high affinity between selenium and mercury. Cu(I)1.28Cu(II)0.36Se nanoparticles were also found to have peroxidase-like activity, which could be inhibited by Hg(II) but not by Ag(I). This unique characteristic coupled with the solubility product principle successfully allows recognition and detection of Hg(II) even in the presence of Ag(I), which has a similar pKsp to Hg(II). As a result, the qualitative and quantitative analyses of Hg(II) could be performed by the naked eye and UV–visible spectroscopy, respectively. The current results indicate that Cu(I)1.28Cu(II)0.36Se nanoparticles not only have great potential in various aspects of dealing with Hg(II) pollution but would also shed light on discovering new nanomaterials to address other heavy metal ions.