AbstractA simple and effective route to improve the fluorescence of carbon dots is reported. A weak fluorescent solution was obtained by a diminution step to obtain tiny particles from bagasse-based carbonaceous blocks. This solution was subjected to hydrothermal treatment under alkaline conditions to improve its fluorescent performance. The luminescence was found to be improved by more than 20-fold after hydrothermal treatment. The ultraviolet absorption and the surface structure were also significantly changed. The alkaline hydrothermal process was shown to involves hydrolysis, isomerization, dehydration, and polymerization that causes the formation of the C=C double bonds and conjugated structures. The optimum hydrothermal conditions were at 200 °C for 8 h, and the most appropriate ratio of NaOH to the amount of the weak fluorescent solution was 38-40 mg to 1 mL.