Evidence is emerging that silica-containing plant cells (phytoliths) and single cell micro-organisms (diatoms) exhibit
optical properties reminiscent of photonic crystals. In the latter biosilicates, these properties appear to arise from light
interactions with the intricate periodic patterns of micro- and nano-pores called foramina that are distributed over the
frustule (outer silica shell). In this report, we show that Nitzschia Closterium pennate diatom frustules can be used to
template arrays of nanoplasmonic particles to confer more complex physical properties, as shown by simulation and
experiment. Selective templating of silver and gold nanoparticles in and around the array of pores was achieved by
topochemical functionalization with nanoparticles deposited from solution, or by differential wetting/dewetting of
evaporated gold films. The nanoplasmonic diatom frustules exhibit surface enhanced Raman scattering from
chemisorbed 4-aminothiophenol. Thermally induced dewetting of gold films deposited on a frustule produces two
classes of faceted gold nanoparticles. Larger particles of irregular shape are distributed with some degree of uniaxial
anisotropy on the surface of the frustule. Smaller particles of more uniform size are deposited in a periodic manner in the
frustule pores. It is thought that surface curvature and defects drive the hydrodynamic dewetting events that give rise to
the different classes of nanoparticles. Finite difference time domain calculations on an idealized nanoplasmonic frustule
suggest a complex electromagnetic field response due to coupling between localized surface plasmon modes of the
nanoparticles in the foramina and an overlayer gold film.
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