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42 TECHNOLOGY JAN/FEB 2025 FDM ASIA | www.fdmasia.com

Baskin Creative Co. 1.6×/0.1 FWD 36 mm objective lens with LED illumination
was used with a magnification of 35×.
• A LSM 800 Zeiss confocal laser scanning microscope.
Analysis parameters: Laser 405 nm, pinhole 0.3 AU, gain

478.
• A scanning electron microscopy (SEM). Images were
acquired using an ETD-BSE backscatter detector. The
studies were performed at an accelerating voltage of 10
kV. Before imaging, the wood samples were coated with
a 6.16 nm thick gold layer. For this purpose, a sputtering
device model EM ACE 600 was used. During the sputtering
wood samples were provided with codes that also enabled process, the table on which the samples were placed was
distinguishing the early and late wood zones: rotated and tilted at an angle of 120 degrees.

• cb—Control, earlywood zone,
• cc—Control, latewood zone, FTIR spectra were recorded using the total internal
• GOb, GOUb—Impregnated wood, earlywood zone, and reflection (ATR) technique in the range of 400–4000 cm−1, at
• GOc, GOUc—Impregnated wood, latewood zone. a resolution of 4 cm−1 and a scan count of 64 on a Thermo
Scientific spectrometer. The spectra were baseline corrected
LIBS spectra were treated using multivariate factorial using Omnic 9 Software.
analysis (FA). LIBS uses an orthogonal, linear conversion of The absorbances of the peaks taken for calculating the

the input data (the set of LIBS spectra) in the new variables crystallinity indices (TCI, LOI, and HBI) were determined using
set called factors. a local baseline connecting the minima of the corresponding
A Statistica v.10 PL software package was used to process curves from the ATR spectra. The crystallinity index (CI) was
the spectra. The method enabled showing similarities and determined using three parameters:
differences in spectra recorded in different depths of wood • The Lateral Order Index (LOI) from the ratios of the
samples. absorbance values at 1430 and 894 cm−1
This can be presented in a simple 2D graphical form. • The Hydrogen Bond Intensity (HBI) was determined for
In general, the interpretation is the following: the closer the the ratio of peaks at 3350 and 1337 cm−1
points representing individual LIBS spectra in the graph are, • The Total Crystallinity Index (TCI) for 1373 and 2900 cm−1

the stronger the similarity of the chemical content in the point
from which the LIBS spectrum was created. In contrast, if Analysis of the Statistical Results of LIBS & FTIR
the spectra are far from each other, they exhibit very differing Example LIBS spectra of the entire recorded spectral range
chemical content. are presented. Selected stratigraphic spectra (pulse numbers
The sample surfaces were imaged using three microscopic 1 and 20) of carbon originating from wood structures and
techniques. graphene oxide delivered in the surface layers of wood are
Structural studies of the surface of wood impregnated also presented. These spectra were related to the stratigraphic

with graphene oxide were performed using: spectra of the non-impregnated wood surface.
• A Zeiss Smart-Zoom 5 stereomicroscope. A PalnApo D The intensity of 247 nm changes with the pulse number,