Determination of surface tension and surface thermodynamic properties of nano-ceria by low temperature heat capacity

Abstract The surface tension and surface thermodynamic properties play a decisive role in research and applications of nano materials, but they are difficult to be determined, as there is no precise method to measure these properties of nano materials. Herein, we derived the relations between the molar surface thermodynamic functions, surface heat capacity, and particle size. On this basis, a new low-temperature heat capacity method for determining the surface tension and the surface thermodynamic functions of nano materials was proposed. We measured the low temperature heat capacities of nano-CeO2 and bulk CeO2 in temperature range from 1.9 K to 300 K at constant pressure by the Physical Property Measurement System (PPMS). The surface tensions and corresponding temperature coefficients of nano-CeO2 were calculated at different temperatures, and then the surface thermodynamic functions were obtained. The results show that the molar heat capacities of nano-CeO2 are greater than that of the corresponding bulk CeO2 in temperature range from 1.9 K to 300 K. The molar surface enthalpy and molar surface entropy of nano-CeO2 increase with the increase of temperature, while surface tension, temperature coefficient, and molar surface Gibbs energy decrease with the increase of temperature. The proposed low temperature heat capacity method can not only accurately measure surface tension, temperature coefficient, and surface thermodynamic functions of nanoparticles at different temperatures, it also provides a reliable and an accurate experimental method for solving the thermodynamic problems of nanoparticles.