Abstract
A full 3D analysis of the hierarchical porosity in Coscinodiscus sp. diatom structures was carried out by using a multiscale approach that combines three advanced volumetric imaging techniques with resolutions and fields of view covering all the porous characteristics of such complex architectures: electron tomography, “slice and view” approach that uses a dual-beam microscope (FIB-SEM), and array tomography consisting of serial imaging of ultrathin specimen sections. This multiscale approach allowed the whole porosity network to be quantified and provided an unprecedented structural insight into these natural nanostructured materials with internal organization ranging from micrometer to nanometer. The analysed species is made of several nested layers with different pore sizes, shapes and connectivities and characterized by the presence of interconnected pores structured in various ways. The first evidence of the presence of a nanometric porosity made of ellipsoidal pores in the siliceous diatom frustules is also provided.
Highlights
Porous materials have received increased scienti c interest due to their peculiar properties[1,2,3] and found applications in several elds such as materials engineering, bioengineering, petrochemicals, environmental protection, medicine and thermal insulation engineering[3,4,5,6]
First we studied the microstructure of Coscinodiscus sp. diatoms focusing on the long-range order within the porous structure in order to determine the spatial arrangement of the structural units and the periodical features of these 3D architectures
This statement is supported by the work of Losic et al that observed the degradation of cribellum layers which are only weakly bonded with the underlying silica layer.[30]
Summary
Porous materials have received increased scienti c interest due to their peculiar properties[1,2,3] and found applications in several elds such as materials engineering, bioengineering, petrochemicals, environmental protection, medicine and thermal insulation engineering[3,4,5,6]. Among the multi-scale and hierarchical porous structures found in nature, diatoms exhibit one of the highest long-range periodicities. These so-called living photonic crystals were observed for the rst time under an optical microscope in 1702 by van Leeuwenhoeck.[16] Their structure is made of an external siliceous skeleton with a complex and intriguing architecture called the “frustule”.17. From the point of view of the properties of interest, these self-assembled porous biosilica structures bene t from peculiar and very interesting properties in terms of photonic response, thermal stability and mechanical strength[18,19,20,21]. Several species of diatoms do exist with unit cells of various shapes and a wide range of pore diameters (from micrometer to nanometer) having typical sizes from that of large bacteria (size in the micrometric range), through intermediate ones which correspond to the size of a virus, to smaller sizes such as for instance those of nitrate molecules (in the nanometric range).[22,23,24] They are nowadays deeply investigated due to their potential use as promising natural alternatives to synthetic porous silica for a wide range of applications including waste degradation, biomineralization-based
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
