Diatoms are unicellular algae that exist in all water habitats and have an enormous biodiversity. Their cell walls of amorphous biosilica exhibit a species-specific nano- to micro patterning. Diatom biosilica offers interesting perspectives for technological applications due to its outstanding properties. It is highly porous, biocompatible, thermally stable and chemically inert. The potential of diatom biosilica for different applications, e.g. in catalysis, for drug-delivery-systems, and biophotonics is a subject of ongoing research.
In this study, diatom biosilica of three different species (S. turris, E. zodiacus, and T. pseudonana) was used as support material for gold nanoparticles using a covalent coupling method. The resulting catalysts were applied for the oxidation of D-glucose to D-gluconic acid. Due to high specific surface area, well established transport pores, and small, homogenously distributed gold nanoparticles on the surface, the diatom biosilica provides a high catalytically active surface and an advanced accessibility of the active sites. In comparison with used reference supports higher catalytic activity (up to 3.28 · 10 -4 mmolGlc s-1 mgAu-1 for T. pseudonana biosilica) and slower deactivation was achieved by two of the diatom biosilica materials. In addition, diatom biosilica showed very high gold loading capacities (up to 45 wt%) keeping a homogenous nanoparticle distribution. Another application is the conversion of diatom biosilica into highly porous carbon materials. Biosilica of the diatom species T. pseudonana was used as hard template for the synthesis of silicon carbide-derived carbons. The typical species-specific macroporous structure is retained during the nanocasting-chlorine treatment process and the resulting materials exhibit very high specific surface areas up to 2300 m2 g -1. Bioinspried carbons show very high capacities in mercury adsorption from aqueous solution of more than 1000 mg g -1
In conclusion, diatom biosilica is a promising alternative to synthetic silica materials for catalytic and adsorptive applications due to its favorable properties and natural origin.