Charging and stability of needle-like TiO\(_{2}\) nanoparticles were studied. Measured isoelectric point (IEP) was pH~4 and lower than that of spherical ones pH~6. Heat treatment at 400\(\text{\r{}}\)C changed the IEP from 4 to 6. The shift is probably due to shape controller (ethylenediamine). The particles aggregate around IEP and thus are charge-stabilized. Experimental hydrodynamic diameters of needle-like particles showed a reasonably good agreement with the theoretical diameter. That is, the particles can be dispersed to primary particles. 1pK Stern and standard electrokinetic models describe electrophoretic mobility of needle-like TiO\(_{2}\), indicating that double layer relaxation is significant for needle-like TiO\(_{2}\).

IntroductionEmulsification is a technology that mixes water and oil, which are normally immiscible, and stabilizes them to a level where there are no practical problems. It is an important technology in various industrial fields such as cosmetics, household products, pharmaceuticals, food, and paint, where it is necessary to control the state of an oil and water mixture 1−13) .Since emulsions are thermodynamically nonequilibrium systems, even under constant temperature and pressure conditions, the state of the emulsion changes over time, eventually leading to a two-phase separation. Additionally,