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 ≤ 3.8 μM), 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.

A new green and effective sonochemical liquid-phase exfoliation (LPE) is proposed wherein a flavonoid compound, catechin (CT), promotes the formation of conductive, redox-active, water-phase stable graphene nanoflakes (GF). To maximize the GF-CT redox activity, the CT concentration and sonication time have been studied, and the best performing nanomaterialfraction selected. Physicochemical and electrochemical methods have been employed to characterize the morphological, structural, and electrochemical features of the GF-CT nanoflakes. The obtained GF intercalated with CT exhibits fully reversible electrochemistry (ΔE p = 28 mV, ipa/ipc = ⁓1) because of the catecholic adducts. GF-CT-integrated electrochemistry was generated directly during LPE of graphite, with no need of graphene oxide production, nor activation steps, electropolymerization, or ex-post functionalization. The GF-CT electro-mediator ability has been proven towards hydrazine (HY) and β-nicotinamide adenine dinucleotide (NADH) by simply drop-casting the redox-material onto screen-printed electrodes. GF-CT-based electrodes by using amperometry exhibited high sensitivity and extended linear ranges (HY: LOD = 0.1 µM, L.R. 0.5-150 µM; NADH: LOD = 0.6 µM, L.R. 2.5-200 µM) at low overpotential (+ 0.15 V) with no electrode fouling. The GF-CT electrodes are performing significantly better than commercial graphite electrodes and graphene nanoflakes exfoliated with a conventional surfactant, such as sodium cholate. Recoveries of 94-107% with RSD ≤ 8% (n = 3) for determination of HY and NADH in environmental and biological samples were achieved, proving the material functionality also in challenging analytical media. The presented GF-CT is a new functional redox-active material obtainable with a single-pot sustainable strategy, exhibiting standout properties particularly prone to (bio)sensors and cutting-edge device development.

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The production of 2D/2D heterostructures (HTs) with favorable electrochemical features is challenging, particularly for semiconductor transition metal dichalcogenides (TMDs). In this work, we introduce a CO2 laser plotter-based technology for...