So I've told to try this method recently, I am not sure what is it called so if you know please tell me.

So these the steps that I've done:

1. Dissolve ligand Schiff base in MeOH-DMF solution

2. Adding it with water, and then added by NH4OH until it's mixed well

3. Add Cu(NO3)2.3H2O solution (in MeOH)

From these solutions, it becomes three layered solution in tube. And slowly will appear needle crystal in the mid layer.

My assumption, this process was diffusion layer technique, however I am not really sure how the work of this method (it will be very helpful if you also give me the reference for this method).

Thank you.