A simple method for the synthesis of water-soluble carbon quantum dots (CQDs) has been developed based on chemical oxidation of starch. The structures and optical properties of the CQDs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence spectroscopy (PL) and transmission electron microscopy. The CQDs were found to emit bright blue fluorescence and disperse uniformly. The effects of ambient temperature, light and pH on the properties of CQDs were studied. The CQDs exhibited good chemical stability, good photostability and pH sensitivity. Furthermore, the interaction between CQDs and bovine serum albumin (BSA) was investigated.
S,N co-doped carbon quantum dots (N,S-CQDs) with super high quantum yield (79%) were prepared by the hydrothermal method and characterized by transmission electron microscopy, photoluminescence, UV-Vis spectroscopy and Fourier transformed infrared spectroscopy. N,S-CQDs can enhance the chemiluminescence intensity of a luminol-H O system. The possible mechanism of the luminol-H O -(N,S-CQDs) was illustrated by using chemiluminescence, photoluminescence and ultraviolet analysis. Ranitidine can quench the chemiluminescence intensity of a luminol-H O -N,S-CQDs system. So, a novel flow-injection chemiluminescence method was designed to determine ranitidine within a linear range of 0.5-50 μg ml and a detection limit of 0.12 μg ml . The method shows promising application prospects.
With the increasing application of semiconductor particles, especially metal-based quantum dots and carbon quantum dots (CQDs), these quantum dots will inevitably be released into the environment, and therefore their effects on biota should be assessed. Few studies on the effects of CQDs on microorganisms and phytoplankton have been performed. In this paper, we put forward more effective and convenient approaches to prepare three kinds of high-quality CQDs. Then we assessed their effects on Staphylococcus aureus and Microcystis aeruginosa, which were representative of microorganisms and phytoplankton, respectively, and compared the effects with the effects of metal-based QDs (CdSeQDs or CdTe-QDs). The results showed that CQDs at low concentrations (<50 mg L À1 ) had insignificant effects on the growth of Staphylococcus aureus and Microcystis aeruginosa, while the influence of the CQDs was observed significantly when the concentration was increased up to 100 mg L À1 . However, the negative impact of metal-based QDs was observed at any given concentration. In conclusion, the results demonstrated that any kind of carbon quantum dot has lower ecological risks than metal-based QDs, which may provide a reference for utilizing carbon quantum dots better and safely.
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