This study demonstrates the intricate relationship between ionic strength and the self-assembly of poly(N-isopropyl acrylamide)-capped iron oxide-silica nanoparticles (PSiFe) at the air-water interface. By systematically varying the ionic strength of the subphase, we unveiled a surprising shift in nanoparticle behavior. Contrary to expectations, increasing ionic strength led to an expansion in the inter-particle spacing, a phenomenon not commonly observed in colloidal systems. This shift of the isotherms was linked to the formation of ionic clouds around the nanoparticles.