Particle size effect on surface/interfacial tension and Tolman length of nanomaterials: A simple experimental method combining with theoretical

Surface tension and interfacial tension are crucial to the study of nanomaterials. Herein, we report a solubility method using magnesium oxide nanoparticles of different radii (1.8-105.0 nm, MgO NPs) dissolved in pure water as a targeted model; the surface tension and interfacial tension (and their temperature coefficients) were determined by measuring electrical conductivity and combined with the principle of the electrochemical equilibrium method, and the problem of particle size dependence is discussed. Encouragingly, this method can also be used to determine the ionic (atomic or molecular) radius and Tolman length of nanomaterials. This research results disclose that surface/interfacial tension and their temperature coefficients have a significant relationship with particle size. Surface/interfacial tension decreases rapidly with a radius <10 nm (while the temperature coefficients are opposite), while for a radius >10 nm, the effect is minimal. Especially, it is proven that the value of Tolman length is positive, the effect of particle size on Tolman length is consistent with the surface/interfacial tension, and the Tolman length of the bulk does not change much in the temperature range. This work initiates a new era for reliable determination of surface/interfacial tension, their temperature coefficients, ionic radius, and Tolman length of nanomaterials and provides an important theoretical basis for the development and application of various nanomaterials.

Life at the interface: Engineering bio-nanomaterials through interfacial molecular self-assembly

Interfacial self-assembly describes the directed organization of molecules and colloids at phase boundaries. Believed to be fundamental to the inception of primordial life, interfacial assembly is exploited by a myriad of eukaryotic and prokaryotic organisms to execute physiologic activities and maintain homeostasis. Inspired by these natural systems, chemists, engineers, and materials scientists have sought to harness the thermodynamic equilibria at phase boundaries to create multi-dimensional, highly ordered, and functional nanomaterials. Recent advances in our understanding of the biophysical principles guiding molecular assembly at gas-solid, gas-liquid, solid-liquid, and liquid-liquid interphases have enhanced the rational design of functional bio-nanomaterials, particularly in the fields of biosensing, bioimaging and biotherapy. Continued development of non-canonical building blocks, paired with deeper mechanistic insights into interphase self-assembly, holds promise to yield next generation interfacial bio-nanomaterials with unique, and perhaps yet unrealized, properties. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Critical size effect for the surface heat capacities of nano-CdS: theoretical and experimental studies

The unique physical and chemical properties of nanomaterials are closely related to their surface thermodynamic functions, which mainly depend on their sizes. In this study, the thermodynamic properties of nano-cadmium sulphide (nano-CdS) were investigated by solubility technology. The nano-CdS powders with different particle sizes were prepared via a traditional solvothermal method, and the electrical conductivities of nano-CdS aqueous solutions at different temperatures were measured. The standard dissolution equilibrium constants of nano-CdS at different temperatures were calculated using the theory of dissolution thermodynamics. The standard molar dissolution thermodynamic functions, the molar surface thermodynamic functions and the specific surface thermodynamic functions of nano-CdS with different particle sizes were calculated by combining the thermodynamic functions of bulk-CdS, the principle of the thermodynamic cycle and the principle of electrochemical equilibrium. The experimental results show that the critical size values for the molar surface heat capacity and the specific surface heat capacity for approximately spherical nanoparticles are 9.3 nm and 8.7 nm, respectively. Within an acceptable range of error, the thermodynamic functions have linear and curved relationships with particle sizes and temperatures. Based on these results, it is disclosed that the critical size effect on surface heat capacities of nano-CdS is valuable to understand the energy storage processes of nanomaterials.