Origins of Efficient Multi-Emission Luminescence in Carbon Dots

Although several groups have synthesized dual-emission carbon dots (D-CDs) and paid more attention to their emission centers in recent years, the luminescence mechanism of D-CDs is still unclear. Here, we synthesized multi-emission CDs via one-pot hydrothermal method. The prepared CDs exhibit three fluorescence emissions (370, 425, 505 nm) under one-wavelength excitation of 320 nm. What is more, various emission origins dominate the unique multi-emission property, which is illuminated by means of radiation decay process, CD internal graphite domains and abundant functional groups characterization. The characterization results fully indicate that there are three energy states: band-gap state (carbon-core state), surface-defect state and molecular state. And the peculiar concentration-dependent and polarity-modulated properties further support the explanation of CD multi-energy states. Strikingly, the CD fluorescence quantum yield is up to 50.68%. Since CDs can show bright green fluorescence excited over 40...