Agarose Template for the Fabrication of Macroporous Metal Oxide Structures

Agarose gels have been applied as templates for the formation of macroporous metal oxide structures. The preparation of the agarose template is extremely simple, and with variation of the agarose content, control over morphology is demonstrated: The average pore size decreases from 180 to 55 nm and the surface area increases from 238 to 271 m2 g-1 with increasing agarose content in the gel. The gelling temperature was also found to influence the final template morphology. Conducting sol−gel chemistry within the template structure followed by removal of the template by heating to 450 °C gives porous inorganic oxides. The technique has been demonstrated for the oxides of titanium, zirconium, niobium, and tin. The final morphology of the metal oxide is homogeneous and results from a coating of the agarose structure. The pore diameter decreased and the specific surface area of the titanium dioxide materials increased from 28 to 66 m2 g-1 as the agarose content in the template is increased from 0.5 to 5.0 wt%. The overall pore size and surface area are lower than the original gel due to shrinkage occurring with the sol−gel process, as well as crystallization and a loss of microporosity in the final material.