Spore-derived color-tunable multi-doped carbon nanodots as sensitive nanosensors and intracellular imaging agents

Fluorescent carbon dots hold great promise in biomedical real-time tracking due to their outstanding optical properties and biocompatibility. Here, we report a one-pot synthetic strategy to produce multi-doped carbon dots (MCDs) with bright and color-tunable emission. The resultant MCDs are doped by abundant biogenic elements (O, N, P), so that they contain a variety of surface functional groups. Such hetero-doping and functionalization make MCDs display strong fluorescent emission and excitation-wavelength-dependent characteristic, good aqueous solubility as well as high photo-stability and ion-stability. Moreover, the as-prepared MCDs response to the change of pH values and exhibit high selective and sensitive detection of Fe 3+ ions under blue light illumination with the limit of detection (LOD) of 15.9 nM. Such a Fe 3+ sensing ability is further demonstrated in real water samples and extended to intracellular multi-color monitoring of Fe 3+ . More interestingly, the MCDs can also sense the gastrointestinal bacteria Escherichia coli , exhibiting linear sensing dependent behavior. With low cytotoxicity and tunable emission, such MCDs hold great potential as efficient multi-color probes and imaging agents for clinical diagnosis.