Fungus-derived photoluminescent carbon nanodots for ultrasensitive detection of Hg²⁺ ions and photoinduced bactericidal activity

Herein, we present a sustainable solvent-free synthetic procedure to produce carbon nanodots from common edible mushrooms (Pleurotus spp.). The resulting mushroom carbon nanodots (MCDs) exhibit stable blue fluorescence with high quantum yield (25%). The MCDs are highly dispersible in water because of the enormous number of oxygen- and nitrogen-containing functional groups on the surface. The MCDs can be used as an effective fluorescent probe for label-free detection of Hg²⁺ ions (detection limit: 4.13 nM). To improve the sensitivity, dihydrolipoic acid was attached to the surface of MCDs, resulting in ultra-sensitivity in Hg²⁺ ion sensing, with a detection limit as low as 17.4 pM. In addition, the MCDs can be used for the labeling of bacteria and as a photoinduced bactericidal agent. Light irradiation of E. coli treated with MCDs showed excellent bactericidal activity relative to the control. These sustainable and affordable carbon materials are potentially compatible for monitoring toxic metals and as a potent visible-light-responsive bactericidal probe.