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Single-phase nanoparticles of brookite, a less common polymorph of TiO2 than rutile and anatase, were successfully synthesized using a water-soluble titanium–glycolate complex as the precursor and nanoparticle growth by an oleate-modified hydrothermal growth method. The synthesized particles were approximately 30 nm in size, had high crystallinity, and were highly dispersible in water. The morphology of the synthesized particles was a pseudocube surrounded mainly with four {210} and two {001} faces, accompanying truncation with small {111} facets. It is considered that the preferential absorption of oleate molecules on {210} and {001} faces resulted in the pseudocubic crystal shape.

We control two growth modes, Ostwald ripening (OR) and oriented attachment (OA), to yield ceria nanocubes by a simple hydrothermal method, using an oleate modified precursor. Using a Ce(III) salt as an initial material, the OA mode is highly activated to form ceria nanocubes with well-developed (002) facets (ca. 8 nm), while OA growth is not allowed so that smaller nanocubes (ca. 5 nm) were formed if Ce(IV) salt is used for the synthesis. A combination analysis by X-ray photoelectron spectroscopy and Fourier transform IR indicates that the surface of ceria nanocubes synthesized with Ce(III) precursor have surface valence (Ce3+) sites coordinating with oleate through bidentate bonding. We propose that the difference in Ce3+ from the grain interior (Ce4+) provides the high surface energy needed to activate the OA growth mode. The luminescence spectra of ceria nanocubes grown by OA rather resemble those of a microcrystalline sample, suggesting the presence of a nonstoichiometric ceria phase, such as Ce2O3, a...

ZnO films on nonseeded substrates with controllable microstructures and crystal orientations were fabricated with a spin-spray method employing trisodium citrate as an additive. The microstructure of the films was made to change from a rod array to a dense film by increasing the trisodium citrate concentration in the solution. This change in structure was accompanied by a weakening of the 002 peak in the XRD pattern. After postdeposition heating, the ZnO rod arrays showed a decrease in visible luminescence, whereas dense ZnO films showed sharp UV luminescence and a weak broad visible luminescence, thus demonstrating a difference in the defect structure of the samples. We tuned the microstructures of ZnO films on nonseeded substrates by using the spin-spray method and analyzed the formation mechanism.

A zinc oxide (ZnO) rod array was deposited on a nonseeded glass substrate at 90 °C by using a spin-spray technique. This technique is a solution process using selective heterogeneous nucleation of ZnO crystals on the substrate, and it eliminates homogeneously nucleated particles that degrade film quality. These features are an obvious progress for solution routes which essentially involves heterogeneous nucleation on seed layer and homogeneous nucleation in solution. In this study, we prepared a ZnO rod array by spin-spray on a nonseeded glass substrate and analyzed the formation mechanism.