Naturally organic functionalized 3D biosilica from diatom microalgae

The diatom biosilica was produced by cultivation of the selected species of diatoms (Pseudostaurosira trainorii) under laboratory conditions. The morphological and structural features, elemental composition, surface area and pore structure, photoluminescence properties, structural bonds and thermal stability of the obtained biosilica were examined using a set of techniques comprising scanning electron microscopy, transmission electron microscopy, UV/vis photoluminescence spectroscopy, IR spectroscopy, X-ray powder diffraction, thermogravimetry, elemental analysis, and porosimetry. The study results demonstrated that diatom frustules possess a three-dimensional structure with silica walls perforated by spatially periodic porous network. Biosilica is composed (98%) of amorphous hydrated silica like opal-A and strong bonded organic residual (about 2%) of biosilica associated proteins and can be considered as naturally organic functionalized 3D silica composite. The diatom biosilica is characterized by three main types of photoluminescence activity: the excitation and emission in the broad mid-ultraviolet range (250-300 nm), the strong photoluminescence in the green region (523 nm) at excitation in mid-ultraviolet region (260 nm), and the excitation-emission in the very narrow blue region (480-493 nm). (C) 2017 Elsevier Ltd. All rights reserved.