Mercury （II） detection by water-soluble photoluminescent ultra-small carbon dots synthesized from cherry tomatoes

Mercury ions have been considered highly toxic to human health. What would be great is to develop the ionic probes without any toxicities themselves. Here, we report a friendly, highly sensitive mercury (II) ionic probe, water-soluble photoluminescence carbon dots which were synthesized by simply hydrothermal treatment of fresh cherry tomatoes without adding any other reagents. The ultra-small (<1 nm) carbon dots show robust excitation-depended photoluminescence under a wide pH range (4–10) or a strong ionic strength of up to 1 M, and the detection limit of mercury (II) has been determined as low as 18 nM. We envision such water-soluble, biocompatible carbon dots that could be applied to biolabeling, bio-imaging, and biosensing fields.