A natural source of porous biosilica for nanotech applications: the diatoms microalgae

Abstract

Several biological organisms, from some sea shells to butterflies, exhibit beautiful and sophisticated organs, developed during the evolution of each species, which properties are defined by their nanostructures. The marine diatoms are microscopic algae enclosed between two valves of hydrated amorphous silica. These intricate structures, called frustules, show quite symmetric patterns of micrometric and nanometric pores. Their strong similarity with man‐made materials, such as synthetic zeolites, or porous silicon and alumina, suggests to exploit the physical properties of the frustules in nanotech applications. In this paper, we review the most relevant results achieved in our laboratory, and all over the world, about the discovery of surprising features that can be found in the characterization of these natural porous biosilica materials. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthetic vs Natural: Diatoms Bioderived Porous Materials for the Next Generation of Healthcare Nanodevices

“…Not long ago, diatom frustules have been suggested in nanotechnology as original bioderived nanodevices . Impressive similarities can be found in the morphology of synthetic and natural silica structures.…”

Therapeutic Applications of Phytoplankton, with an Emphasis on Diatoms and Coccolithophores

“…Precise manipulation of diatoms is challenging, but the complexity of the various micro‐ and nanostructuring and their functional roles, along with their surface chemistry makes the diatom an attractive candidate for biosensing and photonic applications . Thalassiosira weissflogii diatom frustules were covalently conjugated for the first time in vitro with a thiophene‐benzothiadiazole‐thiophene (TBT)‐based fluorophore, resulting in a biohybrid luminescent material with high photoluminescence quantum yields which has applications in bioimaging .…”

Diatoms - nature materials with great potential for bioapplications

“…Differences in PL spectra in culture-grown diatoms compared to fieldcollected benthic diatoms are denoted to more heavily silicified frustule and impurities present in field-collected benthic diatoms that grow in water environment polluted with metals that can possibly influence on frustule architecture and consequently on its luminescence properties [21]. Characteristic diatom PL features are likely to originate from bulk and surface non bridging oxygen absorptions and the radiative decay of self-trapped excitons [21,22]. Characteristic diatoms PL spectra are shown in Figure 2.…”

“…Electrophilic substances such as nitrogen dioxide, ethanol and acetone have an ability to attract electrons from silica skeleton and consequently quench photoluminescence (Figure 3a) [23]. Beside the changes in PL intensity, the principle peak position is moved to longer wavelengths, due to capillary condensation of the gases in a liquid phase and absorption of volatile substances into the nanometer pores of the diatom frustule, which both increase its average refractive index [22,23]. Nucleophilic substances like pyridine and xylene give free electrons to silica surface and increase the PL intensity (Figure 3b).…”