Nanoparticles (NPs) of a perovskite-slab-type oxide, La2Ti2O7, were synthesized using LF-FSP coupled with subsequent heat treatments, and their photocatalytic activity was evaluated using decolorization of methyl orange solution under Uv irradiation. The LF-FSP process used metallo-organic precursors to produce NPs with very low agglomeration with average particle sizes (APSs) of 26 nm (LF-FSP NP). Optimized heat treatment of these NPs at 1000 degrees C/3 h/air gave small, plate-like NPs with high crystallinity, and BET specific surface areas (SSAs) of 14 m(2)/g, that exhibited the best observed photocatalytic activity. High-angle annular dark-field scanning TEM showed that heat-treating eliminates microstructural defects in these NPs, improving photocatalytic activity by approximate to 30%. The current approach to perovskite-slab-type NPs using LF-FSP provides a simple route to materials with superior photocatalytic activity and offers the advantage of good productivity, 30 g/h.