<p>This study presents the fabrication and optimization of fluorine-free silica-based thin films with tunable wettability for self-cleaning applications. Silica nanoparticles were synthesized via a sol–gel spin-coating process using tetraethyl orthosilicate (TEOS) as the precursor, followed by thermal annealing in an air ambient and surface modification using hexamethyldisilazane (HMDS). The influence of TEOS concentration and annealing temperature on nanoparticle size, surface morphology, and wettability was systematically investigated. Structural study by X-ray diffraction technique for all the samples illustrated an amorphous structure of silica thin films with a broad peak around 24^ο without shifting the peak position. Field emission scanning electron microscopy (FESEM) revealed that increased TEOS concentration led to larger particle sizes and enhanced surface roughness. Fourier-transform infrared spectroscopy (FTIR) confirmed successful salinization, and UV-vis spectroscopy showed moderate optical transparency (45%) in the visible/UV-Vis range. Contact angle measurements demonstrated a transition from hydrophilic to superhydrophobic behaviour (up to ~ 139°), governed by surface roughness and chemical modification. The results indicate that the size of the synthesized nanoparticles is closely linked to the TEOS precursor concentration, while their hydrophobic properties are influenced by the HMDS functionalizing agent. This research work signifies a scalable, cost-effective, and environmentally friendly approach for the fabrication of silica film without using fluorinated compounds.</p>