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Synthetic amorphous aluminum silicates-coated titanium dioxides (AS–T nanocomposites) were synthesized by a hydrothermal reaction of aluminum silicate precursors with various chemical compositions and titanium dioxide suspensions. AS–T nanocomposites showed narrow particle size distributions centered between 1.0 and 2.0 μm and their specific surface areas were ranging from 138 to 209 m2/g. Water vapor adsorption isotherms revealed that AS–T nanocomposites with higher Si/Al ratios exhibited high hydrophilicity, as the maximum water adsorption rate reached almost 40 wt%. In methylene blue photocatalytic degradation tests, AS–T nanocomposites with higher Si/Al ratios showed much higher photodegradability than a commercial titanium dioxide, degrading up to 92.7% of methylene blue after 30 min of UV irradiation. A possible mechanism is that a distribution state of Si(Al)–OH and/or Si–OH–Al exposed on the aluminum silicate surface influenced the methylene blue adsorption to the surface, which significantly improved the photodegradation performance. The results of this study indicate that AS–T nanocomposites have the potential to be used as fillers in paints. [ABSTRACT FROM AUTHOR]

A non-crystalline aluminum silicate related to allophane (i.e., clay mineral) was synthesized by a hydrothermal reaction after which the synthetic mineral was mixed with clear or multicolored aqueous emulsion paint as a nanofiller. The nanofiller was revealed by X-ray diffraction to have an amorphous morphology, showed a narrow particle size distribution with a volume mean diameter of 1.2 µm and indicated a specific surface area of 228 m2/g. Clear films prepared with the nanofiller had significantly improved wettability compared to a blank film. The results of outdoor exposure tests exhibited that multicolored films with the nanofiller showed higher antifouling ability than films with a commercially available silica filler. A proposed antifouling mechanism is that the proportion of Si-OH and Al-OH active sites exposed on the nanofiller surface had a significant effect on the surface wettability of the films and exquisitely controlled the sliding of rain droplets. [ABSTRACT FROM AUTHOR]