synthesized carbon dots by simple hydrothermal method, neither get dried by heating at 60 degree. its water dispersion not freezes at -30. how to dry them into powder. it is well dispersed in ethanol and methanol.
Drying in an oven at lower temperature (60 - 80 oC) for longer period of time (more than 24 hours) can also result in powder. However, sometimes this will result in a thick viscous product depending on the hydrophilic nature of your CDs. Especially when you are using ethylenediamine for the synthesis of CDs, you will get this kind of viscous matter.