Adsorption of TiO₂ Nanoparticles at the Surface of Micron-Sized Latex Particles. pH and Concentration Effects on Suspension Stability

摘要

It is shown that although nanoparticles are now finding wide application in a variety of fields, a detailed understanding of their mode of action is important and has to be made on a detailed analysis of their physicochemical properties in solution. In this study, the interaction between micron-sized latex particles and TiO2 manufactured nanoparticles are reported and the importance of the electrostatic interactions is discussed. The surface charge variations of micron-sized latex particles and TiO2 nanoparticles are considered by adjusting the solution pH and three electrostatic scenarios are experimentally determined by performing electrophoretic measurements. In the first scenario,positively charged isolated TiO2 nanoparticles are rapidly adsorbed at the negative latex surfaces and the latex surface charge, latex aggregation and aggregation kinetic rates are found to be controlled by the TiO2 nanoparticle concentration. Fractal aggregates are obtained when latex surface charge is compensated by adsorption of the oppositely charged nanoparticles. Analysis of the variation of the kinetic rate with nanoparticle concentrations indicates an uneven distribution of the TiO2 nanoparticles at the latex surface leading to an extra attractive contribution to the interaction energy between the latex particles. In the second scenario, at the point of zero charge of the TiO2 nanoparticles,and in presence of negatively charged latex particles, the suspension behavior is mainly controlled by the aggregation of the TiO2 nanoparticles. The last scenario which is representative of the presence of negatively charged species is leading to stable suspensions.