Luminescent carbon dots (L-CDs) with high quantum yield value (44.7%) and controllable emission wavelengths were prepared via a facile hydrothermal method. Importantly, the surface states of the materials could be engineered so that their photoluminescence was either excitation-dependent or distinctly independent. This was achieved by changing the density of amino-groups on the L-CD surface. The above materials were successfully used to prepare multicolor L-CDs/polymer composites, which exhibited blue, green, and even white luminescence. In addition, the excellent excitation-independent luminescence of L-CDs prepared at low temperature was tested for detecting various metal ions. As an example, the detection limit of toxic Be2+ ions, tested for the first time, was as low as μM.
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Funding: National Basic Research Program of China (2014CB931700), NSFC (61222403, 11274173), the Doctoral Program Foundation of China (20123218110030), and the Opened Fund of the State Key Laboratory on Integrated Optoelectronics (IOSKL2012KF06).
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