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TECHNOLOGY 45
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is a regularity resulting from the more significant share of The depth of the crater (damaged wood surface) created
lignocellulose in the cell walls. In the case of wood impregnated due to the impact of 20 laser beam pulses locally located on
with graphene oxide using the vacuum method, the amount the surface of the samples was more significant in the early
of the elements tested in the near-surface layers, primarily wood zone than in the latewood zone.

carbon, was dominant early, which indicates that large and This means thinner layers of the wood cell wall in the
empty spaces of the cells that make up the wood were filled early wood zone are more susceptible to damage than the
with GO flakes. cell walls in the latewood zone. Having in mind that crater
The carbon, magnesium, and oxygen content in the near- diameters were typically approximately 100 µm for latewood
surface layers of wood impregnated with graphene oxide samples and approximately 300 µm for early ones, we can
using the ultrasonic method is lower than that of vacuum- find that after 20 laser shots the averaged total (effective)
impregnated wood. ablation volumes were 0.4 mm3 for a late pine wood and
Results of the LIBS spectra factorial analysis (FA) are approximately 8.8 mm3 for early one (we assumed a cylinder-
presented. It is seen that there are small differences between shape crater in calculations).

spectra taken in bright and dark wood grains which show The FTIR spectra obtained as a result of the measurement
similar chemical composition. were compared to show the changes that occurred due to
The location of the spectra from GOb, GOc, GOUb, GOUc, the in laying of wood with GO.
as well as from control not impregnated samples (cb and Due to the high cellulose content in wood, the analysis of
cc) also demonstrate certain differences in chemical content. structural changes in wood after impregnation with graphene
Structural studies conducted using a scanning electron oxide was related to cellulose parameters. The areas (peaks)
microscope of impregnated wood and pressureless ultrasound associated with the crystalline and amorphous structure were

indicate the presence of graphene oxide flakes on the wood compared; on this basis, the influence of the applied GO on
surface. the wood structure was determined.
Graphene oxide flakes form clusters and surface undulations. The presence of the amorphous form of cellulose is
Single GO flakes are visible in the microscopic image. The determined based on the 2900 cm−1 peak (C-H stretching
surface of untreated wood is flat without artifacts. bonds), its size, and position after the modification was
The presence of graphene oxide flakes on the surface of introduced.
impregnated wood was also visualised using a stereoscopic An increase in amorphousness was observed when the
microscope. The early and late wood zones became darker. peak intensity decreased and its maximum shifted towards
Graphene oxide changes the natural colour of the wood longer wavelengths. The second amorphous band is the 898

surface, causing it to turn grey. Small clusters of deposited
GO are visible on the surface of impregnated wood, shown
as dark dots (marked with a black arrow). www.pristuv.com
As indicated by the research conducted by López et al.,
LIBS can be used to clean the wood surface from layers of
applied coatings.
The wood structure imaged with a confocal microscope

indicates changes occurring on the wood surface due to
laser ablation.