Transmission electron microscopy of cellulose. Part 2: technical and practical aspects

Abstract

Transmission electron microscopy (TEM) has played a significant role in the characterization of cellulosic materials, especially the so-called "nanocelluloses" (nanofibers and nanocrystals), from visualizing nanoscale morphologies to identifying crystal structures. With scientific and industrial interest in nanocelluloses rapidly increasing, this technique is more important than ever for scientists, engineers and students. Mastering TEM techniques for cellulosic materials is not trivial for a number of reasons, the main one being the high sensitivity of cellulose crystals to electron beam damage. In this contribution, practical aspects of sample preparation, contrast enhancing protocols as well as specific imaging and diffraction techniques are described to facilitate the morphological and structural characterization of cellulose by TEM in imaging and electron diffraction modes. We especially emphasize the importance of controlling the radiation dose to record well-resolved images of cellulose crystals with meaningful structural detail.

A reproducible method to characterize the bulk morphology of cellulose nanocrystals and nanofibers by transmission electron microscopy

“…Although it was possible to achieve good images of well dispersed sample with this technique, similar to the ones reported before (Brito et al 2012;Hirota et al 2010;Kaushik et al 2015b;Ogawa and Putaux 2019;Saidane et al 2016), this is not the common pattern ( Figure S4), as observed by other authors (Abitbol et al 2013). Observing the texture of the aggregates of CNCs in Fig.…”

Supramolecular Assembly and Chirality of Synthetic Carbohydrate Materials

“…DD is an ideal substrate to develop MicroED, since the benzyl groups present in the molecule render it more resistant to prolonged irradiation. [13] XRD shows the high crystallinity of the assemblies (Supporting Information, Figure S3) and ssNMR indicates the presence of two sets of DD in a single unit cell ( Figure S1). MicroED analysis on DD crystals was performed at cryogenic temperature ( Figure 2).…”

“…DD i) is easy to synthesize, ii) can form tunable supramolecular structures, contains aromatic functionalities that iii) stabilize the self-assembly and iv) make it less susceptible to electron beam irradiation allowing for electron microscopy (EM) analysis. [13] These aspects enabled the development of assays to probe the molecular structures and the chirality of the aggregates. Key interactions that drive the self-assembly were uncovered, suggesting insights into the mechanism of formation.…”

Cellulose nanofibrils prepared by gentle drying methods reveal the limits of helium ion microscopy imaging

“…Cellulose-based materials have been found to be a highly sensitive also to the electron beams and the imaging of the single cellulose nanobril or cellulose nanocrystal is challenging with TEM. 52 More specically, a critical dose where the diffraction from the crystalline part of nanocellulose has been halved as the sign of destruction has been found to be about 6 Â 10 15 electrons per cm 2 . This is about 10-times more than the helium ion dose causing the collapse of the brillar network in our experiment.…”