Figure 3.

Correlative Raman/AFM measurements of compressed early wood of cell wall regions show microchemical and nanostructural differences. (a) Correlative approach to acquire different images exactly from the same sample positions of a wood sample compressed in a 3D printed device. The confocal Raman images visualize the chemistry in context with microstructure by acquiring the inelastic backscattering of laser light, whereas the AFM tip reaches the sample from above, providing a three-dimensional topographical view at nano resolution. (b) Raman images based on CH-stretching of all organic components (2774–3033 cm^–1), aromatic components (1557–1696 cm^–1), and components representing lignin and cellulose (342–402 cm^–1) reveal the compactness of the compressed inner cell wall. (c) Different AFM topographical images showing differences between outer (opened) and inner (compact) cell walls. (d) Height profiles of the opened and compressed secondary cell wall with calculated full width at half-maximum (fwhm).