Daisuke Mizuno

Hierarchical transport of nanoparticles in a lyotropic lamellar phase

The dynamics of nanosized colloidal particles dispersed in a hyper-swollen lyotropic lamellar phase of a nonionic surfactant has been studied by ac electrophoretic light scattering and direct tracking of particles under a microscope. The frequency spectrum of electrophoretic mobility shows two relaxation processes. These are originated from the hindrance of free diffusion of particles by the interaction between membranes and particles. By direct tracking measurement, we find that particles jump from site to site where they stay for a long time. This trap-jump process greatly decreases the mobility at low frequencies.

Hierarchical Dynamics of Nano-Particles in Lyotropic Lamellar Phase

ABSTRACT Dynamics of nano-sized colloidal particles dispersed in a dilute lyotropic lamellar phase of a nonionic surfactant has been studied experimentally by ac electrophoretic light scattering and direct tracking under a microscope. The obtained frequency spectrum of complex electrophoretic mobility shows two relaxation processes at about 1 kHz (HF relaxation) and a few Hz (LF relaxation). These relaxations are due to the hindrance of free diffusion of particles by the hierarchical local static and dynamical structures of lamellar phase. From the direct tracking of fluorescent-labeled particles under a microscope, we find that particles show jump from sites to sites where they stay for a long time. This trap-jump process extremely decreases their mobility at low frequencies.

Dynamics of Nano‐sized Colloidal Particles in a Lyotropic Lamellar Phase

Transport of nano‐sized colloidal particles in a dilute lyotropic lamellar phase of a nonionic surfactant has been studied by AC electrophoretic light scattering. The frequency dispersion of complex electrophoretic mobility shows two relaxation processes at about 1kHz (HF relaxation) and a few Hz (LF relaxation). These relaxations are originated from the hindrance of diffusion of particles in characteristic local structures of lamellar phase. The HF relaxation is found to relate the local deformation of membranes induced by particles. The LF one relates the confinement of a particle within persistence length of lamellar orientation.

New Measurement Method of Complex Electrophoretic Mobility of Charged Colloids by Quasi-Elastic Light Scattering

A new measurement method of complex electrophoretic mobility µ* of colloidal particles in suspension was developed using a heterodyne technique of quasi-elastic light scattering under a sinusoidal electric field. The influence of diffusion was removed by squaring the time-domain signal of scattered light and we succeeded in accurate and highly sensitive measurement of µ* in a wide frequency range for the first time. The frequency dependence of µ* of latex particles was measured up to 50 kHz by this method. The relaxation of mobility due to anomalous double-layer polarization was observed above 1 kHz in the obtained spectrum.