LAUSR

Abstract The facile preparation of g-C3N4 QDs with high fluorescent performance has become an important direction in the last decade. Herein, we develop a facile, rapid approach to synthesize highly fluorescent QDs based on recrystallization and ultrasonic exfoliation. Size-controllable graphitic carbon nitride (g-C3N4) QDs can be obtained from the precursor of recrystallized dicyandiamide, only 90 min is needed and the size of QDs is adjusted from 5 nm to 200 nm by controlling the ultrasonic time. Moreover, better fluorescent efficiency is also obtained comparing to traditional g-C3N4 QDs. The obtained g-C3N4 QDs responds to Cu(II) in the 0.5 nmol/L to 30 μmol/L concentration range, with a 0.3 nmol/L detection limit. The method was applied to the determination of Cu(II) in different environmental water samples.