Carbon dots/Ruthenium(III) nanocomposites for FRET fluorescence detection and removal of mercury (II) via assembling into nanofibers

The determination and removal of mercury(II) (Hg2+) are essential for human health and environmental ecosystems. Herein, an ingenious carbon dots (CDs)-based Förster resonance energy transfer (FRET) system (N, S-CDs/Ru) was fabricated employing CDs and Ru3+ units as energy-transfer doner/acceptor pairs for visual detection and efficient removal of Hg2+. The treatment of Hg2+ induced a remarkable linear enhancement of the ratiometric fluorescence (F613 nm/F478 nm) with a detection limit (LOD) of 95 nM, along with continuous fluorescence color variations from blue to red. Given that the fluorescence color recognition and processing realized the real-time and rapid quantitation of Hg2+ by paper-based smartphone sensing platform. The mechanistic study revealed that the N/S/O-rich surface of the system enabled the Hg2+-triggered self-assembly from dots to nanofibers, combing with the active FRET process. Also, the efficient removal of Hg2+ with a removal efficiency of ∼98 % and an adsorption capacity of ∼372 mg/g was obtained. Furthermore, it was found that N, S-CDs/Ru loaded commercialized SiO2 or SBA-15 could facilitate the removal of Hg2+ with a removal efficiency over 99 % and an adsorption capacity up to ∼562 mg/g. This study provides a potential strategy for environmental monitoring and remediation.