Thin films consisting of a sol-gel Nb₂O₅ matrix doped with zeolite Na-X synthesized from fly ash through ultrasonic-assisted double stage fusion-hydrothermal alkaline activation were deposited by the spin-coating method. In order to improve the optical quality and sensing properties of the thin films zeolites were wet-milled for 60, 120 and 540 seconds prior to incorporation in the film. The liquid adsorption ability of thin films were tested by measuring the reflectance spectra prior to and after exposure to liquid acetone and the change in the reflection coefficient ∆R of the films was calculated. The influence of milling time of zeolites on the sensing and optical properties of the films was studied.