This article reports on optical properties of SrHfO3 and CaHfO3 nanoparticles with sizes as small as 1.6 nm, synthesized via non aqueous solgel routs for the first time. An unexpectedly strong luminescence from the undoped nanoparticles was observed in the visible spectrum over a wide temperature range, also exhibiting sensitivity to temperature variation and surrounding ambient (vacuum/air) and exposure time to UV light. A tentative model is proposed to explain these phenomena in terms of luminescent centers located at the surface of the nanoparticles.