The UV filtering potential of drop-casted layers of frustules of three diatom species

Abstract

Diatoms are in focus as biological materials for a range of photonic applications. Many of these applications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms frustules (silica walls) have been carried out on single cells. In this study, for the first time, we test the spectral properties of layers of frustules of three diatom species (Coscinodiscus granii, Thalassiosira punctifera and Thalassiosira pseudonana), with special focus on transmission and reflectance in the UV range. The transmittance efficiency in the UV A and B range was: T. pseudonana (56–59%) >C. granii (53–54%) >T. punctifera (18–21%) for the rinsed frustules. To investigate the underlying cause of these differences, we performed X-ray scattering analysis, measurement of layer thickness and microscopic determination of frustule nanostructures. We further tested dried intact cells in the same experimental setup. Based on these data we discuss the relative importance of crystal structure properties, nanostructure and quantity of material on the spectral properties of diatom layers. Characterization of the UV protection performance of layers of diatom frustules is of central relevance for their potential use as innovative bio-based UV filters.

Marine-Derived Polymeric Materials and Biomimetics: An Overview

“…Physical scattering of electromagnetic radiation also exists at sub-visible wavelengths: the silica-based external membranes, or frustules of diatoms have been shown to transform electromagnetic frequencies into the ultraviolet range [256][257][258]. Nanoscale features of frustules (holes, slits and ribs) are very reminiscent of photonic bandgap structures.…”

“…These features may focus light at wavelengths close to photosynthetic optima [259], but also refract more potentially dangerous UVR wavelengths and convert them to blue light [258]. Layers of diatoms also present different transmission and reflectance of UVR, depending on characteristics of species-specific frustules [257].…”

Underwater Light Manipulation by the Benthic Diatom Ctenophora pulchella: From PAR Efficient Collection to UVR Screening

“…In recent years, the possible role of diatom frustule in screening from detrimental ultraviolet radiation (UVR) has been scrutinized [33][34][35][36], even though this property has never been studied in conjunction with experiments conducted on living cells in their aquatic environment, but only by characterizing the optical properties of the bare shells in air. For wavelengths below 200 nm, UVR is strongly absorbed by atmospheric nitrogen and oxygen.…”

Photonic Crystal Enhanced SERS Detection of Analytes Separated by Ultrathin Layer Chromatography Using a Diatom Frustule Monolayer

“…The ordered pore arrays of diatom frustule biosilica resemble a 2D photonic crystal and possess photonic properties [ 7 ] that enable their future use as optical waveguides, optical transducers, [ 8 ] and ultraviolet filters. [ 9 ] The addition of optically active materials to the diatom frustule imparts optoelectronic properties to the diatom photonic crystal. For example, the pennate diatom Pinnularia possesses a rectangular array of 200 nm diameter pores on 300 nm pitch.…”