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M. Ghobara, N. Mazumder, V. Vinayak, L. Reissig, I. Gebeshuber, M. Tiffany, R. Gordon:
"On Light and Diatoms: A Photonics and Photobiology Review; invited";
in: "Diatoms: Fundamentals and Applications", R. Gordon, J. Seckbach (Hrg.); Wiley Scrivener, Beverly, 2019, (eingeladen), ISBN: 978-1119-3702-15, S. 129 - 190.

Diatoms are microscopic unicellular algae with shells (frustules) made of amorphous hydrated
silica with various architectures. Their repetitive, multiscale features ranging from 0.3 nm to 5
cm, i.e., 8 orders of magnitude, result in a number of interesting optical properties, including
potential light piping and/or optical communication in colonial diatoms. This wide dynamic
range of length scales occurring in a single, nearly chemically pure structure, the diatom frustule,
makes diatoms truly unique. This leads for certain species' frustules to photonic crystal
features, as suggested by recent studies, which may lead to their ability to focus light of specific
wavelengths, and their selective transmittance and reflectance of other wavelengths, besides
their common photoluminescence properties. Such optical properties might help diatoms in
their photoregulation, as well as other photobiological phenomena found in diatoms such as
phototaxis and karyostrophy (i.e., the movement of chloroplasts along cytoplasmic strands
toward the nucleus). Therefore, there are a number of lessons that we can learn from how diatoms
manipulate electromagnetic fields, especially visible light. As a cheap and readily available
material, diatom frustules could lead to more efficient solar energy harvesters, with diatom
solar panels proposed for the production of both electricity and biofuel. Diatom based sensors
and photocatalysts can be fabricated efficiently. The power of diatoms to work with light is
both fascinating in itself and can be regarded as a powerful source for the development of new
nanotechnologies.

Diatom frustule, natural photonic crystals, optical properties, photobiology, lensless light focusing, light piping, diatom nanotechnology