Combined determination of surface properties of nano-colloidal particles through ion selective electrodes with potentiometer

Five parameters, including specific surface area, surface potential, charge density, electrostatic field strength and charge number on the solid–liquid interface, are important surface properties of charged nano-colloidal particles. Currently, although the specific surface area (outer surface area) can be instrumentally determined through inert gas adsorption, there is no instrument that can determine the other four surface properties, let alone give a combined measurement. A new method for the combined measurement of five surface properties by Na+- and Ca2+-selective electrodes with a potentiometer was developed, which can give precise results with good repeatability from the measurements. Besides, this new method bears three other significant advantages: (1) for the first time, the surface potential and total surface area (both inner and outer surface areas) of particles can be easily determined with a potentiometer, (2) the enhanced dispersion forces of counterions in the surface electrostatic field from charged particles were considered and (3) a combined measurement of the five surface properties can be done with a potentiometer. The combined measurement means that the five surface properties of particles can be determined under identical conditions, which is very important for the study of interface reactions in aqueous solutions. Based on the method, a new apparatus for the combined measurement of the five surface properties of nano-colloidal particles can be developed.