A smartphone-assisted ratiometric fluorescence sensor based on dual-emission copper nanoclusters for visual detection lead ion

Quantification of fluorescent assays with smartphones has great promise in environmental monitoring for providing on-site visual detection. However, the analytical performance of these fluorescence sensors based on single-color channels is usually unable to satisfy the detection accuracy. Here, we propose a smartphone-assisted ratiometric fluorescence-sensing platform based on dual-emission copper nanoclusters ( Cu NCs ) for precisely determining Pb 2+ concentrations. The Cu NCs were prepared by using dithiothreitol ( DTT ) as reducing and stabilizing agents, which possess two intrinsic emission centers located at 450 nm and 620 nm, respectively. In presence of Pb 2+ , the red fluorescence at 620 nm of the Cu NCs were quenched via photoinduced electron transfer process, meanwhile the blue fluorescence at 450 nm could be maintained unchanged. Thus, a ratiometric fluorescence sensing of Pb 2+ was facilely fabricated based on the Cu NCs without introducing other fluorescent materials as the reference, allowing sensitive and selective determination of Pb 2+ with a limit of detection (LOD) of 2 nM. Moreover, extracting the fluorescence color changes of this sensor under the supporting of a smartphone app, a portable sensing platform was constructed for visual detecting Pb 2+ with LOD of 0.05 μM, showing great potential for on-site monitoring of Pb 2+ .