A study on temperature dependency and in situ observation of domain structure in Langmuir layers of stearic acid/γ-Fe2O3 nanoparticle complex at the air/water interface

The Langmuir monolayer behavior of a stearic acid/γ-Fe2O3 nanoparticle complex at the air/water interface have studied at different subphase temperature. The subphase was pure water and an aqueous colloidal solution of γ-Fe2O3 nanoparticles with an average diameter of 81±12 Å. The formation and stability of Langmuir monolayer at different subphase temperatures were measured with pressure–area isotherm curve of stearic acid on a subphase of pure water and γ-Fe2O3 nanoparticle hydrosol. In situ domain structure and molecular orientation of stearic acid/γ-Fe2O3 nanoparticle complex at the air/water interface were measured with Brewster angle microscopic (BAM) image and surface potential at different subphase temperatures.