Vertically aligned ZnO nanotubes were prepared by etching ZnO rod arrays in aqueous solution, which were previously developed by chemical bath deposition method. The morphological, structural, photoluminescence, as well as photocatalytic properties of the ZnO nanotubes were examined with respect to the pH values of chemical bath solution. The morphology of the products was found to be sensitive to the pH values and chemical bath temperatures. The nanotubes synthesized at a low pH value (5.82) exhibited a strong UV emission and a weak defect-related visible emission. The highest photocatalytic efficiency was also observed at pH = 5.82. The possible mechanism for the difference of photocatalytic efficiency was discussed.

Ordered aggregated BaTiO(3) nanocubes with a narrow size distribution were obtained in an aqueous process by using bis(ammonium lactate) titanium dihydroxide (TALH) as Ti source in the presence of oleic acid and tert-butylamine. Kinetics of the formation of BaTiO(3) nanocubes indicated that an in situ growth mechanism was dominant and the superlattice of nanocubes formed in situ through the growth of BaTiO(3) nanoparticles in Ti-based hydrous gel. The size and morphology of nanocubes were controlled by tuning the concentration and molar ratio of surfactants. A novel growth model dependant on the structure of Ti precursor for the formation and morphology control of BaTiO(3) nanocubes and their superlattice was demonstrated.

The dynamic equilibrium model for a bulk nanobubble partly covered with hydrophobic material in water is theoretically and numerically studied. The gas diffusion into a bubble near the peripheral edge of the hydrophobic material on the bubble surface balances that out of the bubble from the other part of the uncovered bubble surface. In the present model, gas diffusion in quiescent liquid is assumed and there is no liquid flow. The total changes of energy and entropy are both zero as it is a kind of equilibrium state. The main origin of the dynamic equilibrium state is the gradient of chemical potential of gas near the peripheral edge of the hydrophobic material. It is caused by the permanent attractive potential of a hydrophobic material to gas molecules dissolved in liquid water as there is permanent repulsion of a hydrophobic material against liquid water. Thus, the gas supply will not terminate. It is numerically shown that stable nanobubble could be present when the fraction of surface coverage by hydrophobic material is from about 0.5 to 1. The stable size of a nanobubble changes with the liquid temperature as well as the degree of gas saturation of water. In slightly degassed water, not only a nanobubble but also a microbubble could be stable in mass balance when the fraction of surface coverage for a microbubble is on the order of 10 or less. For hydrophilic materials, however, a bubble could not be stable unless the fraction of the surface coverage is exactly 1. It is suggested that in many experiments of bulk nanobubbles there could be aggregates of nanobubbles.

In this study, a BaTiO3 (BT) nanocube assembly with metal–insulator–metal capacitor structure was fabricated by a dip-coating process. The BT nanocube assembly had relatively ordered structure after sintering. A high dielectric constant of approximately 3000 was achieved, with relatively low loss tangent. The enhanced dielectric properties of the nanocube assembled film were robust against thickness variation. We conjecture that the mechanism that enhanced the dielectric constant of the BT nanocube assembly is also contributed to by the effect of interfacial lattice strain between neighboring nanocubes.

Monodispersed CeO2 nanocubes were prepared by using a liquid−liquid interface. The morphology of CeO2 nanocrystals from the aqueous phase changed from truncated octahedron to nanocube in the toluene phase at the water−toluene interface. The CeO2 nanocubes oriented to form large cubic particles at a low molar ratio of oleic acid (OLA)/Ce. The red-shift of the absorption edge and the high concentration of Ce3+ in the CeO2 structure was identified for the CeO2 nanocrystals. The high concentration of Ce3+ in the CeO2 structure was identified as one of the main reasons for the red-shift of the absorption edge of CeO2 nanocrystals.

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