Efficient photothermal annealing of carbon quantum dots

To synthesize highly crystalline carbon quantum dots (CQDs), we established a two-step process that integrates hydrothermal reactions and photothermal annealing with a xenon flash lamp. A xenon flash lamp enabled rapid and uniform heating, effectively enhancing crystallinity in a way that contrasts with conventional furnace annealing, which requires extended processing times. Transmission electron microscopy (TEM) analysis revealed that the high-temperature environment with a xenon flash lamp facilitated the conversion of the amorphous carbon structure into a more ordered crystalline form of CQDs. A comparison of Raman spectra and photoluminescence (PL) of amorphous CQDs and crystalline CQDs revealed significant differences between the two states. PL intensity of the crystalline CQDs was approximately ten times higher than that of amorphous CQDs, and this notable difference highlights an advantage of crystallizing CQDs: their optical performance is significantly enhanced.