*2.3. Morphological Characterization*

Atomic force microscopy (AFM) images were acquired using a Nanotec microscope (Nanotec, Madrid, Spain) in low amplitude dynamic mode. Levers used were Nanosensors PPP-NCH (NanoWorld AG, Neuchâtel, Switzerland) with a tip radius curvature less than 10 nm and a resonance frequency of 295 kHz (29 N/m force constant). Samples were prepared from sonicated diluted dispersions (0.1 mg/30 mL water) by placing a 10 μL drop on a freshly cleaved mica muscovite piece (~1 cm2) and allowing to dry overnight inside a Petri dish. The width and length of the nanofibers were measured with WSxM software [53]. Approximately 100 measurements were taken to obtain each width and length distribution.

High-resolution scanning electron microscopy (SEM) imaging was carried out using a JEOL JSM 7500FA (Jeol, Tokyo, Japan) equipped with a cold field-emission gun (FEG), operating at 15 kV acceleration voltage. The samples were coated with a 10 nm thick film of carbon using an Emitech K950X high-vacuum turbo system (Quorum Technologies Ltd., East Sussex, Lewes, UK). Imaging was performed with the secondary electrons to analyze the morphology of the samples.
