Infrared photo-induced force microscopy unveils nanoscale features of Norway spruce fibre wall

Kavindra Kumar Kesari*, Padraic O’Reilly, Jani Seitsonen, Janne Ruokolainen, Tapani Vuorinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)
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Infrared photo-induced force microscopy (IR PiFM) was applied for imaging ultrathin sections of Norway spruce (Picea abies) at 800–1885 cm−1 with varying scanning steps from 0.6 to 30 nm. Cell wall sublayers were visualized in the low-resolution mode based on differences in their chemical composition. The spectra from the individual sublayers demonstrated differences in the orientation of cellulose elementary fibrils (EFs) and in the content and structure of lignin. The high-resolution images revealed 5–20 nm wide lignin-free areas in the S1 layer. Full spectra collected from a non-lignified spot and at a short distance apart from it verified an abrupt change in the lignin content and the presence of tangentially oriented EFs. Line scans across the lignin-free areas corresponded to a spatial resolution of ≤ 5 nm. The ability of IR PiFM to resolve structures based on their chemical composition differentiates it from transmission electron microscopy that can reach a similar spatial resolution in imaging ultrathin wood sections. In comparison with Raman imaging, IR PiFM can acquire chemical images with ≥ 50 times higher spatial resolution. IR PiFM is also a surface-sensitive technique that is important for reaching the high spatial resolution in anisotropic samples like the cell wall. All these features make IR PiFM a highly promising technique for analyzing the recalcitrant nature of lignocellulosic biomass for its conversion into various materials and chemicals. Graphic abstract: [Figure not available: see fulltext.]

Original languageEnglish
Pages (from-to)7295-7309
Number of pages15
Issue number11
Early online date16 Jun 2021
Publication statusPublished - Jul 2021
MoE publication typeA1 Journal article-refereed


  • Cellulose elementary fibril
  • Chemical imaging
  • Infrared spectroscopy
  • Lignin
  • Photo-induced force microscopy
  • Plant cell wall
  • Spruce wood


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