Issue 27, 2019

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

Abstract

TEMPO-oxidized cellulose nanofibrils (TCNFs) have unique properties, which can be utilised in many application fields from printed electronics to packaging. Visual characterisation of TCNFs has been commonly performed using Scanning Electron Microscopy (SEM). However, a novel imaging technique, Helium Ion Microscopy (HIM), offers benefits over SEM, including higher resolution and the possibility of imaging non-conductive samples uncoated. HIM has not been widely utilized so far, and in this study the capability of HIM for imaging of TCNFs was evaluated. Freeze drying and critical point drying (CPD) techniques were applied to preserve the open fibril structure of the gel-like TCNFs. Both drying methods worked well, but CPD performed better resulting in the specific surface area of 386 m2 g−1 when compared to 172 m2 g−1 and 42 m2 g−1 of freeze dried samples frozen in propane and nitrogen, respectively. HIM imaging of TCNFs was successful but high magnification imaging was challenging because the ion beam tended to degrade the TCNFs. The effect of the imaging parameters on the degradation was studied and an ion dose as low as 0.9 ion per nm2 was required to prevent the damage. This study points out the differences between the gentle drying methods of TCNFs and demonstrates beam damage during imaging like none previously reported with HIM. The results can be utilized in future studies of cellulose or other biological materials as there is a growing interest for both the HIM technique and bio-based materials.

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

Article information

Article type
Paper
Submitted
26 Feb 2019
Accepted
13 May 2019
First published
20 May 2019
This article is Open Access
Creative Commons BY license

RSC Adv., 2019,9, 15668-15677

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

A. E. Ketola, M. Leppänen, T. Turpeinen, P. Papponen, A. Strand, A. Sundberg, K. Arstila and E. Retulainen, RSC Adv., 2019, 9, 15668 DOI: 10.1039/C9RA01447K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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