Multicolorful fluorescent-nanoprobe composed of Au nanocluster and carbon dots for colorimetric and fluorescent sensing Hg2+ and Cr6+

In this article, we reported a dual emissive multicolorful fluorescent-nanoprobe which was composed of gold nanocluster (BSA-Au NCs) and carbon dots (CDs) with a certain proportion, i.e. Au NCs-CDs. The dual emissive Au NCs-CDs showed pink fluorescence under UV light, and the dual emission peaks at 625 nm and 444 nm were corresponded to the existence of Hg2+ and Cr6+ respectively. The fluorescence color transformed from pink to blue when in presence of Hg2+. The blue fluorescence emission of CDs selectively quenched by Cr6+, whereas the red fluorescence of BSA-Au NCs was stable against Cr6+, which can be treated as internal reference. The difference response of the two emissions to Hg2+ and Cr6+ resulted in a distinguished fluorescent color change, which can be noticed by the naked eyes clearly. When the Hg2+ and Cr6+ were exposed to the Au NCs-CDs simultaneously, the dual-emission of the Au NCs-CDs were all reduced and exhibited the complete quenching of the pink emission. The detection limits for Hg2+ and Cr6+ were 1.85 nM and 5.34 nM, respectively. Significantly, it was successfully applied to determine the existence of Hg2+ and Cr6+ in real samples, which offered the advantages of simplicity, environmentally friendly and cost saving efficiency.