Iron ion sensing and in vitro and in vivo imaging based on bright blue-fluorescent carbon dots

Herein, we propose an eco-friendly synthesis of carbon dots (CDs) and ingeniously design a rapid and label-free "turn-off" sensing platform for ultrasensitive recognition of Fe³⁺ in vitro and in vivo. CDs with extraordinary advantages involving exceptional stability, ultra-low toxicity as well as admirable biocompatibility were simply prepared via one-step hydrothermal strategy of Caulis polygoni multiflora. Result indicated that as-acquired CDs not only exhibit excitation dependency, but also have a high quantum yield of (QY) up to 42%. Miraculously, the fluorescence of CDs can be extinguished sharply by Fe³⁺ because of static quenching effect with linear range of 0-400 µM, yielding a detection limit of 0.025 μM. Benefiting from these characteristics, CDs have been extended for multicolourful imaging and tracking Fe³⁺ fluctuations in living cells. Bioimaging of zebrafish larvae exposed to CDs confirmed that it is smoothly circulated to other tissues and organs owing to their small size. Eventually, as-prepared CDs have been implemented for the real-time detection of Fe³⁺ in nude mice.