Lysosome-targeted dual-emissive carbon dots for ratiometric optical dual-readout and smartphone-assisted visual determination of Hg²⁺ and SO₃²

Smartphone-assisted visual assay not only expands quantitative analysis but also enhance real-time on-site sensing capabilities. Herein, lysosome-targeted dual-emissive carbon dots (L-CDs) can not only recognize Hg²⁺ and SO₃^2- by ratiometric fluorescence and ratiometric absorption, but also visually quantify Hg²⁺ and SO₃^2- by smartphone-assisted method. With monitoring of intrinsic ratiometric fluorescent variation (I₅₈₀/I₄₆₈), L-CDs are developed as an effective sensing platform for ratiometric fluorescent successive identification of Hg²⁺ and SO₃^2- accompanying with continuous fluorescence variation of blue, purplish pink, pink, and light yellow. With detecting of inherent ratiometric absorption change (A₅₃₈/A₂₀₆), L-CDs are also constructed as an efficacious sensing terrace for ratiometric absorption consecutive discrimination of Hg²⁺ and SO₃^2-. More crucially, integrating continuous fluorescence color change and color recognizer APP in the smartphone, visual quantification of Hg²⁺ and SO₃^2- can be accomplished on the basis of the ratio of red value and blue value (R/B) with linear ranges of 0-130 and 0-850 µM, respectively, as well as LOD of 8.4 and 12.9 nM, respectively. More interestingly, confocal fluorescent imaging of HeLa cells further verifies that L-CDs can be regarded as favorable biosensors for on-site, real-time differentiation of Hg²⁺ and SO₃^2- in vitro and in vivo with ratiometric manners.