A liquid-phase method for preparing uniform-sized silica nanospheres (SNSs) 12 nm in size and their three-dimensionally ordered arrangement upon solvent evaporation have recently been pioneered by us. The SNSs are formed in the emulsion system containing Si(OEt) 4 (TEOS), water, and basic amino acids under weakly basic conditions (pH 9-10). Here, we report the formation mechanism of the SNSs; the reasons for the uniform size and the ordered arrangement are described in detail. The formation process is monitored by FE-SEM, SAXS, and liquid-state NMR. The FE-SEM observations reveal that silica nanoparticles ca. 4 nm in size are formed in the water phase at the early stage (∼0.5 h) of the reaction. The SAXS measurements suggest that the number density of the particles remains unchanged when they are gradually grown. Liquid-state 1 H NMR analyses suggest that TEOS are slowly hydrolyzed at the oil-water interface to continuously supply silicate species into the water phase. The silicate species are immediately consumed for the growth of the parent particles without forming new particles. The size of the SNSs can be tuned from 8 to 35 nm by varying the synthesis conditions and/or the amount of TEOS. The zeta potential and pH of the dispersion of SNSs throughout the solvent evaporation process are almost constant approximately at -40 mV and 9-10, respectively; the SNSs have been well-dispersed until the final stage of the evaporation process. The critical roles of basic amino acids in the formation and regular arrangement of SNSs are discussed based on the experimental results.

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To verify pore blocking controlled desorption in ink-bottle pores, we measured the temperature dependence of the adsorption-desorption isotherms of nitrogen on four kinds of KIT-5 samples with expanded cavities hydrothermally treated for different periods of time at 393 K. In the samples, almost spherical cavities are arranged in a face-centered cubic array and the cavities are connected through small channels. The pore size of the channels increased with an increase in the hydrothermal treatment time. At lower temperatures a steep desorption branch changed to a gradual one as the hydrothermal treatment was prolonged. For the sample hydrothermally treated only for 1 day, the rectangular hysteresis loop shrank gradually with increasing temperature while keeping its shape. The temperature dependence of the evaporation pressure observed was identical with that expected for cavitation-controlled desorption. On the other hand, for the samples hydrothermally treated for long times, the gradual desorption branch became a sharp one with increasing temperature. This strongly suggests that the desorption mechanism is altered from pore blocking to cavitation with temperature. Application of percolation theory to the pore blocking controlled desorption observed here is discussed.

We investigated the effect of water-soluble alcohols (glycerol, propylene glycol, and 1-propanol) on the surfactant aggregation and its structure by phase study, surface tension measurement, small-angle X-ray scattering (SAXS) measurement, and pulsed field gradient NMR self-diffusion measurement. The phase behavior in the (water + glycerol)/C12EO8 system as a function of the glycerol content in water at constant temperature is similar to that in the water/C12EO8 system as a function of temperature, and a phase separation (clouding phenomenon) takes place at a high glycerol content. The phase separation was not observed in the other alcohol systems. However, a hexagonal liquid crystal (H1) changes to an isotropic solution (Wm) in all the systems with increasing the alcohol content. The SAXS measurement for the H1 and the Wm phases, and the self-diffusion measurement for the Wm phase suggest that the dehydration of the ethylene oxide chain takes place and the aggregates tend to grow with increasing glycerol content. On the other hand, propylene glycol or 1-propanol molecules tend to penetrate into the palisade layer of the aggregates and the micelles are downsized, and eventually they are broken into monomers with increasing the alcohol content. The critical micelle concentration measurement also supports the difference in the alcohol effects on the phase behavior in the aqueous nonionic surfactant system.