Tricolor emission carbon dots for label-free ratiometric fluorescent and colorimetric recognition of Al3+ and pyrophosphate ion and cellular imaging

Ratiometric determination endows fluorescence (FL) sensors improving accuracy and sensitivity by measuring intensity ratio of well-resolved emission peaks. Herein, tricolor-emission carbon dots (T-CDs) have been developed for ratiometric recognition of Al3+ and pyrophosphate ion (PPi). T-CDs were fabricated from hematoxylin and Tris by one-pot hydrothermal treatment. As-prepared T-CDs engender amusing triple emission bands, including bright yellow and orange FL, but weak blue FL. Upon introducing Al3+, yellow and orange FL is distinctly quenched while blue one is enhanced. On subsequent addition of PPi, T-CDs’ FL can be partially recovered. The ratiometric fluorescent changes of T-CDs have been utilized to detect Al3+ and PPi in aqueous solution with linear ranges of 5–15 μM and 0.75–10 μM, respectively, as well as limits of detection of 0.8 nM and 2.2 nM, respectively. More importantly, laser scanning confocal microscope imaging of HeLa cells demonstrates that T-CDs could be applied to visually monitor Al3+ and PPi fluctuations in living cells, illustrating that proposed T-CDs have tremendous potential in biological systems.