Thermodynamic Characterization on Surface of Iron Oxide Nanoparticles Prepared by Co-precipitation: An Inverse Gas Chromatography Application

Abstract

Surface thermodynamics of magnetic particles are crucial for many applications. In this study, a series of magnetic iron oxide nanoparticles were synthesized by co-precipitation at room temperature varying iron salts and base concentrations. The retention times of several organic solvents on these iron oxide nanoparticles were obtained in the temperature range from 323 to 363 K by inverse gas chromatography at infinite dilution. The dispersive component of surface free energy, γS D , thermodynamic parameters of adsorption (free energy, ∆G SP , enthalpy ∆H SP , entropy, ∆S SP) and the acid KA and base KD constants were calculated for iron oxide samples. It was found that γS D values fluctuated between 36 mJ/m 2 and 20 mJ/m 2 for all of the samples and temperatures. It was seen that the values of KD/KA were proportional with base concentration but inversely proportional with iron concentration. Hence it was arisen that the adsorption properties and acidbase contributions to the surface energy of iron oxide nanoparticles prepared by co-precipitation method altered considerably depending on the synthesis conditions. It can be said that the more effective surface modifications can be carried out adjusting synthesis conditions of iron oxide nanoparticles.