Curcumin is a molecular dye, see  (http://en.wikipedia.org/wiki/Curcumin).

Depositing it would yield an unstable coating which would go off with exposure to solvents. 

Alternatively you may need either:

- encapsulating the dye inside a polymer layer

or

- chemisorption of the molecules with the surface of the electrode (using a condensation reaction with surface OH groups).

Try dip coating method with good polymer adhesive / resin