Fabrication of gold nanostructures by templating from porous diatom frustules

Diatoms produce diverse three-dimensional regular silica structures with nanometer to micrometer dimensions and hold considerable promise for biological or biomimetic fabrication of nanostructured materials and devices. In this paper, a simple procedure for fabrication of gold nanostructures with complex morphologies using porous diatom frustules as templates is described. The gold nanostructures are formed by means of thermal evaporation of gold onto porous frustules. Nanostructured gold films were obtained upon release from the diatom templates and were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Vis spectrophotometry. Three centric diatom species, Coscinodiscus sp., Thalassiosira eccentrica and one unidentified species cultured in our laboratory, were used as templates. The prepared gold replicas come in a variety of forms and shapes including arrays of nanoscale pillars, dots and more complex three-dimensional structures, depending on which porous surface of the diatom was used for replication. In all cases, gold nanostructures closely follow the organization and distribution of pores of the frustule template. Spectrophotometric characterisation shows that the templated nanostructured gold films exhibit localized surface plasmon resonance (LSPR) effects.