In this paper we report on optical absorption measurements performed on several metal oxide nanoparticles (ZnO, CeO 2, Fe 2 O 3) as a function of temperature in the range 25500 C, in order to study the optical properties, and to investigate how several heating cycles could affect nanoparticle structural stability and absorption characteristics. These are quite important issues to be investigated in order to assess the possibility to use such metal-oxide nanoparticles as gas-based high temperature nanofluid in concentrated solar power (CSP).