溶液中の表面ラフネスの付着力・摩擦力への影響

抄録

In this study, we made monolayers of hydrophilic particles at an air/aqueous interface using TiO₂ particles. In order to study the conditions and parameters necessary to obtain a monolayer with a controlled close-packing, we studied the effects of subphase pH, subphase salt concentration, and particle size on the ability to form a monolayer. These factors were chosen as the solution pH controls the charge on the TiO₂ surface, the salt concentration can vary the magnitude of electrostatic repulsion and therefore the attractive forces affecting a TiO₂ particle, and the size of the particle may affect the magnitude of the flotation and gravitational forces. TiO₂ particles with diameters of 300nm , 500nm, 1μm, 5μm, 10μm, and 20μm, solution pH of 2, 6, and 11, and salt concentrations of 0, 100mM, and 500mM have been used in this study.

We saw that hydrophilic particles could be made to form a monolayer at an air/aqueous solution by tuning the physical parameters of the system, e.g. by pH. This was done in our case for TiO₂ particles by spreading them at an air/aqueous interface, when the subphase had a pH ＜ iep of TiO₂. The positive charge of the particle and the negative charge of the interface allow the particle to float, due to a charge-induced capillary force.