Thermodynamics at the nanoscale: A new approach to the investigation of unique physicochemical properties of nanomaterials

An extension of the classic thermodynamics theory to nanometer scale has generated a new interdisciplinary theory - nanothermodynamics. It serves as a bridge between macroscopic and nanoscopic systems. Over the past decade, nanothermodynamics theories have developed rapidly owing to their critical role in investigating the size-dependent physicochemical properties of nanomaterials. This review examines up-to-date research results on this cutting-edge topic. The focus and emphasis are on the utilization of nanothermodynamics models to investigate the size-dependent thermal stability, magnetic properties, photoelectric behaviors, thermoelectric phenomena, mechanical properties, electrical properties, etc. of nanomaterials. A range of properties have been studied with respect to the effects of size, dimensionality and composition through a quantitative nanothermodynamics model. It is found that (a) the size dependence of these properties can be universally reconciled to the effect of severe bond dangling; (b) for the same material size, the sequence of size effects on the properties, from strong to weak, is nanoparticles, nanowires and thin films; and (c) the composition effects on the properties of nanoalloys are substantial, having a nonlinear relationship. It also reveals that vacancy formation determined by the cohesive energy variation is one of the intrinsic factors which dominate the size-dependent physicochemical properties of nanomaterials.