Carbon dots with red emission for bioimaging of fungal cells and detecting Hg and ziram in aqueous solution.

It is of importance for bioimaging of fungal cells using biocompatible and low toxic carbon dots (CDs) as labels in plant protection field because a clearer understanding on the infection mechanism of fungi on plant can be achieved. Meanwhile, long wavelength, especially, red/near-infrared (NIR) emissive CDs are more biocompatible than short wavelength emissive ones. In this work, CDs with red emission were synthesized by solvothermal pyrolysis of citric acid, acrylamide dissolved in formamide. Fungal cells stained by the CDs with red emission were brightly illuminated when imaged on a fluorescent microscope with excitation by a green laser pulse, suggesting the CDs are of an excellent label for bioimaging of fungal cell in red color region. Moreover, the CDs show a selective response to Hg in the NaAc-HAc buffer solution, while ziram can form a more stable complex with Hg, leading to a recovery of the quenched fluorescence of the CDs. Therefore, methods for the detections of Hg and ziram based on the "off-on" fluorescence of the CDs were established with limits of detection as low as 0.19 μM and 0.55 μg/mL.