Carbon quantum dots(CQDs)is prepaerd by a facile ultrasonic dispersion method.First,with improved Hummers′method,graphite is used as carbon source to prepare graphene oxide,and then ultrasonic separation method is used to get a 10~20nm carbon quantum dots.Next the relationship between CQDs and ultrasonic intensity is investigated.Transmission electron microscopy(TEM),Raman,infrared spectrometer,dynamic light scattering instrument,fluorescence spectrometer are used to determine the functional group,morpholog...