I synthesize ZnO quantum dots (QDs) as an electron transport layer in this method: 10 mL ethanol containing 5.5 mmol TMAH was dropped into 30 mL DMSO containing 3 mmol zinc acetate hydrate within 5 min, and then stirred for 1 h under ambient conditions. Finally, the obtained ZnO QDs were washed twice with acetone and ethanol. But the final aggregates cannot well dispersed in ethanol, does anyone how to solve this? There were indeed so many publications using this method to synthesize ZnO, which can be well dispersed in ethanol at a concentration of 45 mg/mL. For my case, I cannot get it with several mg/mL solution. Why？how to solve this ？