Optical properties of single diatom frustules revealed by confocal microspectroscopy

Abstract

Received Month X, XXXX; revised Month X, XXXX; accepted Month X, XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX Optical properties of single diatom frustule valves from two different Coscinodiscus species (C. Wailesii and C. Centralis) are studied by transmission confocal hyperspectral imaging and numerical calculations. Light convergence, concentration and trapping effects are observed and depend on both the wavelength and the valve orientation. These effects seem to occur independently of the incident light angle. From our results, a wavelength dependent multifocal lens behavior can be explained by light diffraction related to the radial symmetry of the multi-scaled 3D nanostructure.

Diatom frustules as a biomaterial: effects of chemical treatment on organic material removal and mechanical properties in cleaned frustules from two Coscinodiscus species

“…nano-to micrometer scaled sieves [5] or drug carriers [6] , [7] as well as vectors for drug delivery [8] , protein adsorbents [9] and as photocatalysts [10] . Diatom frustules also show particular optical properties [11] , [12] , [13] , [14] , [15] , [16] , [17] making them interesting for several optical applications [18] . Furthermore, the biosilica can also be used as a powder to reinforce other composites [19] .…”

Towards uniformly oriented diatom frustule monolayers: Experimental and theoretical analyses

“…diatoms, the exoskeleton surfaces include up to three layers of pore structures, with pore sizes ranging from 60 nm to 1 μm. These hierarchical, porous structures give rise to the diatom frustules' extraordinary mechanical strength 4 , enormous surface area 5 , and unique optical properties 6,7 .…”

“…In optical research, it has been demonstrated that diatom frustules behave as optical crystals, focusing light due to their micron and sub-micron scale pore arrays 15,16 . In addition, it has been reported that frustules have the unique ability to trap light due to their hierarchical pore structures 7,17,18 , a property that has been successfully leveraged in enhancing dye-sensitized solar cell performance 17 .…”

“…For example, in the application to biosensors, in which diatom frustules have been employed as bonding sites 19 , the ability to uniformly orient diatom frustules (especially in a 'concave side facing down' manner) may increase the utilization of the micro-nanostructures, thus increasing the bonding area. Moreover, in optical applications 7 , uniformly oriented frustules have the potential to form light focusing/ trapping layers, thereby allowing more than just single diatoms to act as optical components, increasing the potential scale and efficiency of these devices. Importantly, the ability to manipulate the frustules on a large scale, combined with simple arraying techniques 20 , may enable the development of practical, real-world applications using diatoms.…”

“…Importantly, the ability to manipulate the frustules on a large scale, combined with simple arraying techniques 20 , may enable the development of practical, real-world applications using diatoms. However, despite the promise of the use of diatom frustules in a variety of areas, the unique properties of diatoms have typically only been studied on the scale of a single diatom frustule (requiring only individual diatom alignment) [6][7][8][10][11][12][13][14][15][16] or as bulk materials (requiring no significant alignment) 17 .…”