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Gold Nanoparticle-Decorated Diatom Biosilica: A Favorable Catalyst for the Oxidation of dāGlucose
Diatoms are unicellular
algae of enormous biodiversity that occur in all water habitats on
earth. Their cell walls are composed of amorphous biosilica and exhibit
species-specific nanoporous to microporous and macroporous patterning.
Therefore, diatom biosilica is a promising renewable material for
various applications, such as in catalysis, drug-delivery systems,
and biophotonics. In this study, diatom biosilica of three different
species (Stephanopyxis turris, Eucampia zodiacus, and Thalassiosira
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. Because of its high specific surface area, well-established
transport pores, and the presence of small, homogeneously distributed
gold nanoparticles on the surface, diatom biosilica provides a highly
catalytically active surface and advanced accessibility to the active
sites. In comparison to those of the used reference supports, higher
catalytic activities (up to 3.28 Ć 10<sup>ā4</sup> mmol<sub>Glc</sub> s<sup>ā1</sup> mg<sub>Au</sub><sup>ā1</sup> for T. pseudonana biosilica) and
slower deactivation were observed for two of the diatom biosilica
materials. In addition, diatom biosilica showed very high gold-loading
capacities (up to 45 wt %), with a homogeneous nanoparticle distribution