Sakshi Saini

Zeta potential occurs in dispersed systems.

If you disperse your film into small colloidal particles, you can measure the zeta potential, but it will no longer be a film, but a dispersed system.

You can measure the electrode potential of the film relative to a standard hydrogen electrode.

Yes, you can do approximation if your film is from 1 layer only. We did such experiment for evaluation of zeta potential of cryogels. The concept is the same. Film should be grounded to fine powder and then make suspension in water and it is ready for measurement. Article Cryogel-based Ag°/Ag2O nanocomposites for iodide removal from water