Synthesis of dual-emissive ratiometric probe of BSA-Au NCs and BSA-Cu NCs and their sensitive and selective detection of copper and mercury ions

Herein, we synthesized bovine serum albumin-functionalized gold nanoclusters (BSA-Au NCs) and BSA-Cu nanoclusters (Cu NCs) by a facile and environmentally-friendly method, and simply mixed them to develop a ratiometric fluorescent sensor for mercury (Hg2+) and copper (Cu2+) ions detection, respectively. The as prepared BSA-Au NCs were known to emit pink color fluorescence (peaking at 616 nm) and BSA-Cu NCs were blue-emitting (peaking at 398 nm) upon the exposure of ultraviolet light (365 nm). Among them, BSA-Au NCS was used as the response signal and BSA-Cu NCs was the reference signal. Interestingly, when the easily prepared ratiometric probe were employed to detect 15 kinds of common metal ions, only Hg2+ and Cu2+ ions could significantly quench the pink fluorescence of BSA-Au NCs. We found that the fluorescence intensity ratio (I-616/I-398) of the nanohybrid system was efficiently reduced by the addition of Hg2+ and Cu2+ ions compared to a series of metal ions. The response of the nanohybrid probe to Cu2+ showed an excellence linear relationships in the concentration range of 0.1 similar to 1 mu M and 1 similar to 5 mu M respectively, and its detection limit was 23.4 nM. Moreover, the fluorescence quenching caused by Hg2+ ions exhibited excellent and wide linear relationships from 0.06 to 1 mu M and 1-4 mu M respectively, with detection limits as low as 19.4 nM. With the increase of Cu2+/Hg2+ concentration, this nanohybrid probe also showed obvious fluorescence color changes that could be directly observed by the naked eye.

Automated summary

In this study, BSA-Au NCs and BSA-Cu NCs were synthesized and mixed to develop a ratiometric fluorescent sensor for Hg2+ and Cu2+ ions detection. The fluorescence of BSA-Au NCs was quenched significantly by only Hg2+ and Cu2+ ions among 15 common metal ions tested. The nanohybrid probe showed excellent linear relationships and low detection limits for both Cu2+ and Hg2+ ions, with visible fluorescence color changes at higher concentrations.