Femto oxygenplasma system

To prepare the lignin coatings,
50 mg/mL lignin solutions in 1,4-dioxane were prepared by stirring
at room temperature for 4 h. After that, the solutions were spin-coated
on silicon wafers (2 cm × 2 cm size, 5 mm thickness). Before
spin-coating, substrates were cleaned via sonication for 10 min in
methanol, deionized water, and acetone and placed in a Femto Oxygen
Plasma system (200 W, Diener Electronic) under 5 mL/min oxygen flow
for 15 min. Then, 120 μL of the solution was deposited on the
wafer, completely covering its surface, and then spin-coating was
performed at 2000 rpm for 80 s using a Convac ST 146 spin coater.
The samples were annealed at 120 °C for 30 min and dried under
vacuum overnight at room temperature. The coatings were then incubated
in water for 24 h to remove the possible unstable parts and finally
dried again at room temperature before characterization.

Samples for AFM were
prepared on silicon wafers (10 mm × 8 mm size) cleaned via sonication
in methanol, deionized water, and acetone for 10 min each. The substrates
were then placed in a Femto Oxygen Plasma system (200 W, Diener Electronic)
under 5 mL/min oxygen flow for 15 min. AFM images were recorded using
an Asylum Research Cypher VRS instrument (Oxford Instruments, United
Kingdom). Measurements were done in tapping mode using a trihedral
aluminum-coated silicon cantilever (HQ:NSC14/Al BS, MikroMasch, Hungary)
with a spring constant of 5 N/m and a resonance frequency of ∼160
kHz. To determine nanoparticle sizes and size distributions, 4 μL
of a nanoparticle dispersion in CHCl₃ (concentration 0.1
mg/mL) was deposited on a silicon wafer. The wafers were dried overnight
at room temperature and then imaged. Images were processed with the
Gwyddion software. The reported particle sizes are the average of
50 nanoparticle heights. To study the morphology of polymer blend
films, 10 μL of polymer solution in CHCl₃ (polymer
concentration 10 wt %) was spin-coated on the surface of a silicon
wafer by a Convac ST 146 spin-coater (2000 rpm, 100 s) and then dried
overnight at room temperature.