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<p>This study demonstrates the sustainable valorization of human hair bio-waste into graphene oxide (GO) for electrochemical cadmium ion (Cd<sup>2+</sup>) sensing, with a systematic investigation of age-dependent structural and electrochemical properties. Activated carbon derived from hair of distinct age cohorts21–30 (GO-2130), 31–40 (GO-3140), and 41–50 (GO-4150) was synthesized via pyrolysis (600&#xa0;°C, N<sub>2</sub> atmosphere) and subsequently oxidized using modified Hummers’ method. The GO samples were deposited on glassy carbon electrodes (GCEs) through solvent evaporation to fabricate electrochemical sensors. Comprehensive characterization revealed critical structure–property relationships: FTIR identified oxygenated functional groups (C = O, O–H) and nitrogenous moieties (C≡N), while XRD confirmed amorphous carbon conversion to crystalline GO with distinct (002) planes. Raman spectroscopy highlighted defect densities via I<sub>D</sub>/I<sub>G</sub> ratios of 0.72 (GO-2130), 0.77 (GO-3140), and 0.77 (GO-4150). BET analysis demonstrated that GO-3140 exhibited superior specific surface area (43.88 m<sup>2</sup>/g) and pore volume (0.15 cm<sup>3</sup>/g), attributed to age-dependent keratin degradation kinetics. HRTEM analysis revealed few stacked layers of GO-3140 and exhibit significant-exfoliated structure in comparison to GO-2130 and GO-4150 samples which shows reduced electrochemical performance due to their aggregation and increased layer thickness. Semi-crystalline nature GO samples sheet confirmed by SAED patterns with layered arrangement and structural integrity. SEM further revealed interconnected porous networks with edge defects, enhancing hydrophilicity and Cd<sup>2+</sup>adsorption. Electrochemical analysis via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) established GO-3140/GCE as the optimal sensor, achieving a linear detection range of 1–8&#xa0;µM (R<sup>2</sup> = 0.991) and a limit of detection (LOD) of 0.55&#xa0;µM. The enhanced performance correlates with synergistic effects of high surface area, defect-mediated ion transport, and oxygen/nitrogen functional groups enabling chelation. This work establishes human hair as a tunable precursor for functional carbon materials while addressing critical gaps in age-dependent bio-waste valorization for environmental sensing applications.</p>

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Sustainable electrochemical sensors from human hair: age-dependent structural defects in graphene oxide govern cadmium ion detection efficiency

  • 期刊论文

  • 发表日期：

    2025年12月25日

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  • Abhishek Mathur,
  • Suresh Sundaramurthy

摘要

This study demonstrates the sustainable valorization of human hair bio-waste into graphene oxide (GO) for electrochemical cadmium ion (Cd2+) sensing, with a systematic investigation of age-dependent structural and electrochemical properties. Activated carbon derived from hair of distinct age cohorts21–30 (GO-2130), 31–40 (GO-3140), and 41–50 (GO-4150) was synthesized via pyrolysis (600 °C, N2 atmosphere) and subsequently oxidized using modified Hummers’ method. The GO samples were deposited on glassy carbon electrodes (GCEs) through solvent evaporation to fabricate electrochemical sensors. Comprehensive characterization revealed critical structure–property relationships: FTIR identified oxygenated functional groups (C = O, O–H) and nitrogenous moieties (C≡N), while XRD confirmed amorphous carbon conversion to crystalline GO with distinct (002) planes. Raman spectroscopy highlighted defect densities via ID/IG ratios of 0.72 (GO-2130), 0.77 (GO-3140), and 0.77 (GO-4150). BET analysis demonstrated that GO-3140 exhibited superior specific surface area (43.88 m2/g) and pore volume (0.15 cm3/g), attributed to age-dependent keratin degradation kinetics. HRTEM analysis revealed few stacked layers of GO-3140 and exhibit significant-exfoliated structure in comparison to GO-2130 and GO-4150 samples which shows reduced electrochemical performance due to their aggregation and increased layer thickness. Semi-crystalline nature GO samples sheet confirmed by SAED patterns with layered arrangement and structural integrity. SEM further revealed interconnected porous networks with edge defects, enhancing hydrophilicity and Cd2+adsorption. Electrochemical analysis via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) established GO-3140/GCE as the optimal sensor, achieving a linear detection range of 1–8 µM (R2 = 0.991) and a limit of detection (LOD) of 0.55 µM. The enhanced performance correlates with synergistic effects of high surface area, defect-mediated ion transport, and oxygen/nitrogen functional groups enabling chelation. This work establishes human hair as a tunable precursor for functional carbon materials while addressing critical gaps in age-dependent bio-waste valorization for environmental sensing applications.