The solution is conductive but when i convert it to solid (thin film) by spin coating the film is not continuous and not conductive, there is not any spot in the film on glass substrate conductive, what can I do?
Frankly, I can offer you only general answers without further details about the experimental system:
1) Is it possible that the solvent you are using is conductive and the film-forming substance is not? This would be by far the simplest explanation of your results.
2) Assuming that you are working with conjugated polymers (seeing conductivity, thin films and spin coating), you may want to deposit a film (even an imperfect one) via drop-casting and measure its conductivity. Depending on deposition method, you can get different polymer film morphologies - if the film is highly ordered, its conductivity will be highly anisotropic. It may be so that your measurement setup is sensitive enough to only "see" conductivity in a particular dimension (along the conjugated polymer chain) but not in other directions (e.g. perpendicular to the length of the polymer chain).
3) Was the polymer film subjected to any kind of treatment after spin-coating? I would recommend capturing the UV-Vis-NIR, IR/Raman spectra of both your solution and film. A comparison (particularly IR/Raman) will show whether any changes have taken place in the structure of the film-forming substance during spin-coating. I mention UV-Vis-NIR in the case (once again) that you are working with conducting polymers - it should be enough to detect any changes in the doping state of your polymer.
4) Assuming that you know the conductivity of your film-forming substance, what kind of conductance would you expect from your film (this is a very rough estimate, since the two conductivities cannot be really compared directly) during the measurement? Would your experimental system be able to sense it? Perhaps the issue is film thickness. That is, the film is too thin to be able to show conductance sufficient to be detected by your experimental system (and translating into lack of observable conductivity).
I would recommend
a) increase the concentration of the dispersion
c) coat the surface more than once to ensure the contact of individual conductive counterparts inside the film
c) dry it well
d) measure the conductivity at very low voltage difference, some time the film resistance might be very high.
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