Fei quanta 200

The morphological analysis of modified/unmodified carbon electrodes was carried out with scanning electron microscope (SEM) images. The observations of the sensors surfaces were performed with a FEI-QUANTA 200 at the ICECHIM laboratory (Bucharest, Romania). The SEM images were taken at an accelerating voltage of 25–30 kV using a gaseous secondary electron detector (GSED). The micrographs of the samples were investigated at different magnifications to identify changes on the surface between modified and unmodified carbon electrodes. For each sensor, 4–7 micrographs were performed and the relevant images are presented.

The morphology of free DFX, polymers, SDs, and pellet surface was investigated using SEM (model FEI Quanta 200, FEI Company, USA) with a resolution of 3.0 nm. The specimens were primarily coated with a thin gold layer before the investigation to create electrical conductivity (at 30 kV).

Pollen grains at floral stage 13 were harvested for morphological analysis by environmental scanning electron microscopy (FEI Quanta 200; FEI Co., Hillsboro, OR), stained with a DAPI solution (0.1 M sodium phosphate, pH 7, 0.4 µg/mL of DAPI, 1 mM EDTA and 0.1% Triton X-100) for the observation of pollen nuclei by fluorescence microscopy, Alexander staining solution^{38 (link)} or 0.5 µg/µL of fluorescein diacetate and 1 µg/µL of propidium iodide for pollen viability testing and with 0.02% neutral red for vacuole analysis.
Aniline blue staining of germinated pollen grains in pistils was performed as described previously^{39 (link)}. Pollinated pistils were collected 16 h after pollination, fixed in a solution of ethanol:acetic acid (3:1) for 2 h, washed with distilled water three times, further softened with 8 M NaOH overnight and then washed with distilled water three times. The softened pistils were incubated with an aniline blue solution (0.1% aniline blue in 0.1 M K₂HPO₄-KOH buffer, pH 11) for about 3 h in the dark, and then observed with a Zeiss fluorescence microscope (LSM710; Carl Zeiss AG, Oberkochen, Germany).

PNs samples from all experimental groups and control were fixed in 2.5% of glutaraldehyde in 0.05 M cacodylate buffer (pH 7.2) at 4 °C overnight, and then washed, at least three times, in the same buffer at 4 °C. Thereafter, to preserve the myelin, the samples were post-fixed for 1 h with 2% OsO₄. Fixed samples were dehydrated in increasing concentrations of acetone (30%, 50%, 70%, 90%, and 100%), and completely dried by using the critical point drying method [32 (link)]. Dried samples were covered with gold and analyzed under a scanning electron microscope FEI Quanta 200 using the high vacuum mode (FEI Europe, Eindhoven, The Netherlands) from the Department of Histology.

The surface morphology of untreated and heat-treated LDPE (U-LDPE and T-LDPE, respectively) sheets were analyzed using environmental scanning electron microscopy (FEI Quanta 200) (FEI Company, Hillsboro, OR, USA). Dehydrated samples were dried, mounted, and then sputter-coated with gold for ESEM analysis.