Electric response of nonspherical and spherical silica particle dispersions to ac electric field.

For the purpose of revealing unique aspects of the electrical double layer (EDL) around nonspherical particles, we focus on a silica square platelike particle with well-defined shape, i.e., H-ilerite.

Electrokinetic effect of the bottom surface of a vessel on pearl-chain formation of silica particles.

We have tackled in situ electric conductance measurements under microscopic observations for alignments of silica particles that are induced by ionic polarization of the electrical double layer (EDL) around the particles. Using the in situ conductance measurements, we have presented evidence that electro-osmotic flow at a vessel bottom/water interface would be coupled with the ionic polarization in the EDL of spherical silica particles settling at the bottom (Langmuir 2007, 23, 8797). In this study, we followed this phenomenon further.

Salt-induced formation of uniform fiberlike SBA-15 mesoporous silica particles and application to toluene adsorption.

Long, homogeneous fiberlike SBA-15 mesoporous silica particles are prepared by fine adjustment of three reaction conditions--stirring temperature, stirring time, and amount of inorganic salt added--using Pluronic P123 and TEOS under acidic conditions. The addition of NaCl along with a short stirring time played an important role in controlling the morphology and pore characteristics. Dynamic adsorption performance for gaseous toluene was systematically evaluated using four types of materials with different morphologies and pore characteristics synthesized with the addition of a different amount of NaCl.

Enhanced pearl-chain formation by electrokinetic interaction with the bottom surface of vessel.

Counterions in an electric double layer (EDL) around a colloidal particle accumulate on one side of the EDL and are deficient on the other side under an electric field, resulting in an imbalance of ionic concentration in the EDL, that is to say, the ionic polarization of EDL. It is well known that the ionic polarization of EDL induces electric dipole moments whereby the alignments of colloidal particles (e.g.

In situ conductance measurements for alignments of silica particles under alternating electric fields.

The alignments of silica particles formed in sinusoidal electrical fields of 1 kHz were assessed using an optical microscope with measuring the electric conductance of a silica dispersion between two Pt electrodes in a vitreous silica glass cell. We confirmed that the electric conductance of the silica dispersion between the two electrodes in the cell reflected the surface conductance of the silica particles settling at the bottom of the cell. More interestingly, we observed that the electric conductance of the silica dispersion in the cell increased when pearl chains of the silica particle were formed along the direction of the electric field.

Effect of pore structure in mesoporous silicas on VOC dynamic adsorption/desorption performance.

The dynamic adsorption/desorption behavior of volatile organic compounds (VOCs) such as toluene (C7H8) and benzene (C6H6) was evaluated for three kinds of mesoporous silicas of SBA-15, all having almost the same mesopore size of ca. 5.7 nm, and a MCM-41 silica with a smaller pore size of 2.