Synthesis, physicochemical and electrochemical characterization of graphene oxide nanosheets obtained through improved and modified Hummers methods

• Synthesis and characterization of graphene oxide nanosheets using various methods. • Ultrasound enabled GO dispersion for carbon paste electrode preparation. • GO-graphite materials showed excellent electrochemical performance . • Caffeic acid was used as a model molecule for detection evaluation. Graphene oxide (GO), with its large specific surface area, oxygenated functional groups, and conductive properties, is an efficient and versatile material for enhancing the sensitivity and selectivity of electrochemical devices. This study examines the electrocatalytic activity of two types of GO synthesized via an improved method (IGO) and a modified Hummers method (HGO + ), aimed at optimizing devices for voltammetric quantification. Characterizations showed particle sizes of 342.0 ± 24.3 nm (IGO) and 615.1 ± 81.5 nm (HGO + ), with zeta potentials of –33.5 ± 0.557 mV and −34.667 ± 0.635 mV. UV–visible spectra showed bands at 228 nm (IGO) and 231.5 nm (HGO + ). XRD analysis revealed characteristic peaks at 10.40° (IGO) and 11.25° (HGO + ), corresponding to interlayer spacings of 0.860 nm and 0.786 nm, while FTIR confirmed functional groups (C=O, C=C, C-O-C, CH 2 -OH). SEM revealed nanosheet morphology. GO-modified CPEs were synthesized using high-power ultrasound (60 s, 20 % amplitude) producing IGO/CPE and HGO + /CPE. EIS showed GO reduced charge transfer resistance from 847.6 Ω for CPE to 130.1 Ω (IGO/CPE) and 106.6 Ω (HGO + /CPE). Cyclic voltammograms showed peak separations of 60 mV (IGO/CPE) and 45 mV (HGO + /CPE), compared to 120 mV for CPE. Surface coverages were 7.3 × 10 −6 mol/cm 2 (IGO/CPE) and 1.3 × 10 −5 mol/cm 2 (HGO + /CPE). Electrocatalytic performance was tested with caffeic acid. Charge transfer coefficients increased from 0.418 ± 0.06 (CPE) to 0.731 ± 0.03 (IGO + /CPE) and 0.736 ± 0.04 (HGO + /CPE), improving oxidation rates. GO-modified CPEs exhibited superior electrocatalytic performance, demonstrating their potential as sensitive electrochemical sensors.