Visualizing Degradation of Cellulose Nanofibers by Acid Hydrolysis

Panagiotis Spiliopoulos, Stefan Spirk, Timo Pääkkönen, Mira Viljanen, Kirsi Svedström, Leena Pitkänen, Muhammad Awais, Eero Kontturi*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

25 Citations (Scopus)
143 Downloads (Pure)


Cellulose hydrolysis is an extensively studied process due to its relevance in the fields of biofuels, chemicals production, and renewable nanomaterials. However, the direct visualization of the process accompanied with detailed scaling has not been reported because of the vast morphological alterations occurring in cellulosic fibers in typical heterogeneous (solid/liquid) hydrolytic systems. Here, we overcome this distraction by exposing hardwood cellulose nanofibers (CNFs) deposited on silica substrates to pressurized HCl gas in a solid/gas system and examine the changes in individual CNFs by atomic force microscopy (AFM). The results revealed that hydrolysis proceeds via an intermediate semi-fibrous stage before objects reminiscent of cellulose nanocrystals were formed. The length of the nanocrystal-like objects correlated well with molar mass, as analyzed by gel permeation chromatography, performed on CNF aerogels hydrolyzed under identical conditions. Meanwhile, X-ray diffraction showed a slight increase in crystallinity index as the hydrolysis proceeded. The results provide a modern visual complement to >100 years of research in cellulose degradation.

Original languageEnglish
Pages (from-to)1399-1405
Number of pages7
Issue number4
Early online date1 Feb 2021
Publication statusPublished - 12 Apr 2021
MoE publication typeA1 Journal article-refereed


  • atomic force microscopy
  • cellulose degradation
  • nanocellulose
  • order/disorder transitions


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