Regulation of fluorescence emission of carbon dots via hydrogen bonding assembly

Carbon dots (CDs) can be wildly used as fluorescence (FL) sensing, bioimaging, drug delivery and optoelectronic devices because of their distinguished photo-stability against photobleaching, low toxicity and easy surface functionalization toward different applications. However, solid fluorescent CDs are rarely reported due to the notorious aggregation caused quenching (ACQ) effects. Here, we proposed a simple synthesis strategy to prepare CDs via hydrogen bonding self-assembly (HB-CDs). Most important of all, the FL emission of HB-CDs can be easily regulated based on hydrogen bond dynamic adjustability. When hydrogen-bonding break reagents were introduced, the emission shifted from yellow to blue. Hence, we put forward a novel solid-state photoluminescence mechanism, namely, the yellow emission can be excited by the formation of J-aggregates and the blue emission can be excited by dispersion. Based on this phenomenon, we developed a new CDs composites with dual modes FL emissions. These findings may provide a novel strategy to easily prepare CDs with solid-state fluorescence and tunable fluorescence.