Influence of Oxidation Time on Defect Density and Crystallinity in Graphene Oxide Synthesized via Modified Hummer’s Method

Oxidation of graphite layers is a crucial intermediate step during the chemical exfoliation of graphene, directly influencing the layer thickness, defect density, and functional group distribution. However, the mechanism governing structural and chemical changes in this stage remains insufficiently understood. In this work, graphene oxide (GO) was synthesized via the modified Hummer's method with controlled oxidation times of 6, 12, and 24 h, labeled as GO-T1, GO-T2, and GO-T3, respectively. XRD results showed nearly constant interlayer spacing but notable variations in crystallite size, indicating a time-dependent structural reorganization. FTIR and XPS analyses revealed that the overall oxygen content (C/O ratio) remained relatively stable, while the functional group distribution varied with oxidation time. Raman spectroscopy demonstrated a steady increase in the defect density over prolonged oxidation. Based on these findings, a time-dependent oxidation mechanism was proposed, offering a pathway to systematically understand and fine-tune GO properties through a controlled reaction time for practical applications.