Multifunctional water-soluble luminescent carbon dots for imaging and Hg²⁺ sensing

We propose an ingenious method for large-scale fabrication of water-soluble photoluminescent carbon dots (CDs) by a one-step microwave route in the presence of citric acid and ethylenediamine. In contrast to other CDs-based nanomaterials, the CDs prepared exhibit a highly fluorescent quantum yield (QY) and excellent stability in both organic and inorganic phases. After simple post-treatment, the CDs can be used as a new type of fluorescent ink for information storage and nanofiber electrospinning. It should be noted that the CDs are a superior fluorescent bioimaging agent in cells, plants and animals according to their excellent solubility and ultra-low toxicity. In addition, the CDs could be utilized as a modification-free biosensor reagent capable of detecting Hg²⁺ in complex environments. More significantly, environmental friendly "skillful pens" were fabricated that provided an effective platform for portable qualitative-detection of Hg²⁺.