Abstract
Highly porous particles with internal triply periodic minimal surfaces were investigated for sorption of proteins. The visualization of the complex ordered morphology requires complementary advanced methods of electron microscopy for 3D imaging, instead of a simple 2D projection: transmission electron microscopy (TEM) tomography, slice-and-view focused ion beam (FIB) and serial block face (SBF) scanning electron microscopy (SEM). The capability of each method of 3D image reconstruction was demonstrated and their potential of application to other synthetic polymeric systems was discussed. TEM has high resolution for details even smaller than 1 nm, but the imaged volume is relatively restricted (2.5 μm)3. The samples are pre-sliced in an ultramicrotome. FIB and SBF are coupled to a SEM. The sample sectioning is done in situ, respectively by an ion beam or an ultramicrotome, SBF, a method so far mostly applied only to biological systems, was particularly highly informative to reproduce the ordered morphology of block copolymer particles with 32–54 nm nanopores and sampling volume (20 μm)3.
Highlights
A periodic ordered morphology is seen, which resemble in part a Schoen gyroid (Fig. 1d) or a Schwarz P structure (Fig. 1e)
We have previously demonstrated the advantages of 3D image reconstruction by slice-and-view focused ion beam (FIB)/SEM29,30 and serial block face (SBF)/SEM30 to fully characterize the morphology of polymeric membranes, obtaining information on their asymmetric porosity, as well as to reveal details of hierarchical porous isotropic films[13,14]
SBF has been used even less for polymer systems than FIB and we demonstrate here the great potential of this methodology
Summary
We applied and compared for the first time a series of advanced and complementary methods of 3D imaging of highly ordered nanoporous particles with triply periodic minimal surfaces: transmission electron microscopy (TEM) tomography, slice-and-view focused ion-beam (FIB) and serial block face (SBF) scanning electron microscopy (SEM). The high-resolution microscopy images shown in Fig. 1 represent only part of the complex morphology of the obtained particles.
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