PROCEEDINGS ARTICLE | May 18, 2009
Proc. SPIE. 7356, Optical Sensors 2009
KEYWORDS: Biosensing, Silica, Optical properties, Luminescence, Silicon, Gases, Organisms, Biological research, Electromagnetism, Atmospheric optics
Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica.
Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. Frustules
from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as
photoluminescence, lens-like behavior and, in general, photonic-crystal-like behavior as long as confinement of
electromagnetic field is concerned. In particular, intrinsic photoluminescence from frustules is strongly influenced by
the surrounding atmosphere: on exposure to gases, the induced luminescence changes both in the optical intensity and
peaks positions. To give specificity against a target analyte, a key feature for an optical sensor, a biomolecular probe,
which naturally recognizes its ligand, can be covalently linked to the diatom surface.
We explored the photoluminescence emission properties of frustules of Coscinodiscus wailesii centric species,
characterized by a diameter of about 100-200 μm, on exposure to different vapours and in presence of specific bioprobes
interacting with target analytes. Very high sensitivities have been observed due to the characteristic morphology of
diatoms shells. Particular attention has been devoted to the emission properties of single frustules.
