Controlling anatase coating of diatom frustules by varying the binding layer

Diatoms have ordered three dimensional porous exoskeletons (frustules) comprised primarily of amorphous silica which can be used as templates for materials applications. Hydrolysis of titanium(IV) isopropoxide (TIP) in the presence of surface bound poly(4-vinyl pyridine) or citric acid results in the formation of anatase on the surface after calcining at 450 °C, however as shown with atomic force microscopy (AFM), different morphologies are formed. Citric acid preferentially resulted in a thin film of anatase over the surface of the frustule whereas poly(4-vinyl pyridine) resulted in the formation of nano-particles of anatase (90–100 nm) on the surface.