Layer-by-layer assembly of TiO₂ colloids onto diatomite to build hierarchical porous materials

TiO₂ colloids with the most probably particle size of 10 nm were deposited on the surface of macroporous diatomite by a layer-by-layer (LBL) assembly method with using phytic acid as molecular binder. For preparation of colloidal TiO₂, titanium(IV) isopropoxide (Ti(C₃H₇O)₄) was used as titanium precursor, nitric acid (HNO₃) as peptizing agent and deionized water and isopropanol (C₃H₇OH) as solvent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption-desorption, and UV-vis spectra are used to assess the morphology and physical chemistry properties of the resulting TiO₂ coated diatomite. It was shown that the mesoporosity has been introduced into macroporous diatomite by LBL deposition. The mesoporosity was originated from close-packing of the uniform TiO₂ nanoparticles. More TiO₂ could be coated on the surface of diatomite by increasing the deposition cycles. This hierarchical porous material has potential for applications in catalytic reactions involved diffusion limit, especially in photocatalytic reactions.