Water-Phase Exfoliated Biochar Nanofibers from Eucalyptus Scraps for Electrode Modification and Conductive Film Fabrication

A solvent-free strategy to produce water-dispersed biochar-nanofibers (BH-CNF) is reported, demonstrating the potential of this cost-effective and sustainable material in electrochemical sensing and fabrication of conductive films. Water-phase BH-CNF from eucalyptus scraps were achieved using a Kraft process followed by liquid-phase exfoliation assisted by the biological stabilizing agent sodium cholate. BH-CNF-based sensors were constructed following two strategies: surface modification of screen-printed electrodes and fabrication of exclusively nanofiber-based flexible sensors. The latter were fabricated through a procedure that is cost-effective and within everyone’s reach. The potentiality of the BH-CNF-based sensors has been challenged toward a wide range of analytes containing phenol moieties and applied for detection of o-diphenols and m-phenols in olive oil samples. The BH-CNF-based sensors exhibited repeatable (RSD ≤ 7%, n= 5) and reproducible (RSD ≤ 10%; n = 3) results, proving their applicability in electroanalytical applications and the robustness of the exfoliation and fabrication strategy. For sample analysis, LODs for hydroxytyrosol (LOD ≤ 0.6 μM) and tyrosol (LOD ≤ 3.8μM), intersensor precision (RSD calibration slope < 7%, n = 3), and recoveries obtained in real sample analysis (91−111%, RSD ≤ 6%; n = 3) endorse the material exploitability in real analytical applications.