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A new series of hydrotalcite (HT)-like anionic clays containing Zr 4+ in the brucite-like layer has been synthesized by a simple coprecipitation method at constant pH. The incorporation of Zr in the layer has been investigated by various analytical methods, such as powder X-ray diffraction (PXRD), chemical analysis, FT-IR, ultraviolet-visible diffuse reflectance (UV-vis DR) spectra, and thermogravimetric analysis (TGA). The PXRD of assynthesized samples showed that the crystallinity of the material decreased with increasing Zr content due to the distortions introduced by the incorporation of the larger cation, Zr. Thermal calcination at 723 K results in the formation of a poorly crystalline MgO phase in which some of the Zr 4+ cations are dissolved. The crystallinity of the resulting MgO phase decreases with increasing Zr content and forms a ZrO 2 phase, in addition to the MgO phase, at higher Zr content. Calcination at higher temperatures (>1000 K) yields a mixture of MgO, MgAl 2 O 4 spinel, and ZrO 2 phases. The UV-vis DR spectra showed that the Zr 4+ cations are well-dispersed in both uncalcined as well as in calcined samples, similar to that in Zrsilicalites.

Ordered macroporous electrodes (OMEs) formed by template synthesis have physical properties that are determined by the template. For colloidal crystal templates, these structures are inverse replicas of the fcc crystal structure with pore dimensions determined by the particle diameter in the colloidal crystal. The dimensions of the solid phase are determined by the interstitial space between the particles in the crystal.Here we demonstrate finite size effects in ordered macroporous gold electrodes. The adsorption of octadecane thiol is used to demonstrate that for structures fabricated from colloidal crystals with particle sizes less than 500 nm the resistance is dominated by surface scattering.

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