thermos-physical properties of working fluids in solar thermal application due to their excellent light absorption, thermal stability, and ease of preparation. This research presents the optical absorption of Aluminum oxide ₂ ₃ , Nickel oxide , and Antimony oxide ₂ ₃ nanoparticles each as a single nanofluids. The study was carried out using COMSOL Multiphysics software, where the optical absorption of the single nanofluid having equal mass fraction (100mg) were evaluated. Results revealed that the ₂ ₃ nanofluid exhibited low absorption of 11% due to its wide band gap (5.3eV) and optical transparency in the visible region. and ₂ ₃ oxide nanofluid due to their narrower band gaps (3.4eV to 1.5eV) also enhanced the absorption to 19% and 20% respectively. The study establishes that metal oxides nanoparticles can significantly improve the optical performance of the nanofluid which later influence optical-thermal conversion for photothermal application.