Nanostructured CaCO3 Thin Films Formed on the Urease Multilayers Prepared by the Layer-by-Layer Deposition

Nanostructured CaCO3(NCC) thin films wit h honeycomb-shaped nanopores were obtained at the surface of urease-embedded multilayers prepared by the layer-by-layer deposition. Amorphous CaCO3 (ACC) droplets were initially nucleated from the multilayer surface, because of the enzymatic reaction of ureases to produce CO2, particularly when the saturation index Of CaCO3 in the crystal-forming solution is above 1.89 based on the calcite saturation. Once ACC droplets successfully covered the entire surface of the Urease in multilayers, the ACC layers underwent the transformation into the crystalline {104}-faceted nanostructured calcite thin films with square pores, similar to 30 nm on each side, in a humidity-controlled chamber. Furthermore, such NCC thin films were realized on various substrates (two-dimensional patterns, PS microspheres, and sawtooth-shaped three-dimensional patterns) taking full advantage of the conformal multilayer coating capability of the layer-by-layer deposition.