Biomimetic Synthesis of Metal Oxide Nanoparticles

Abstract

Current approaches to the synthesis of metal oxides generally require harsh conditions. In contrast, many biological processes can produce intricate metal oxide nanostructures under ambient conditions. For example, the diatom Cylindrotheca fusiformis forms reproducible nanostructures from silicic acid using species specific peptides known as silaffins. Herein, we report that the R5 peptide a bioinspired analogue derived from the NatSil protein in C. fusiformis can form titanium dioxide (TiO2) in a concentration dependent manner from the non-natural substrate, titanium bis(ammonium lactato) dihydroxide (TBALDH). Additionally, the polypeptide poly-L-lysine (PLL) acts as a template for the biomimetic synthesis of TiO2. Furthermore, non-peptide based biomimetic templates have been investigated. Amine terminated PAMAM and PPI dendrimers are effective mimics of silaffins and other silica precipitating polyamines. By varying the concentration of cations in solution, the size of the resulting silica nanoparticles can be controlled. Furthermore, the scope of dendrimer mediated metal oxide formation has been expanded to include titanium dioxide (TiO2), a photocatalyst, and crystalline á-germanium dioxide (GeO2), a blue photoluminescent material.