Raman-directed optimisation of ultrasonication induced structural evolution in graphene oxide colloidal dispersions

Graphene oxide (GO) colloidal dispersions are increasingly utilised as nano-reinforcements in cementitious systems; however, their effectiveness depends on achieving stable exfoliation without excessive ultrasonication-induced structural damage. This study develops a Raman-guided optimisation framework to evaluate the combined influence of GO concentration and sonication duration on nanosheet integrity and dispersion stability. GO suspensions with concentrations of 0.01–0.125 mg/mL were sonicated for 5–20 minutes at 60% amplitude and analysed primarily using Raman spectroscopy, supported by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), optical microscopy, zeta potential, and dynamic light scattering (DLS) measurements. The results show that lower GO concentrations were more susceptible to cavitation-induced defect formation and fragmentation, whereas higher concentrations reduced localised acoustic damage by dissipating ultrasonic energy across a higher nanosheet loading. The optimal dispersion condition was identified at 0.125 mg/mL with 10-minutes sonication, yielding the lowest defect ratio ( D R ≈ 0.51), preserved nanosheet integrity, and effective exfoliation. Prolonged sonication for 20-minutes increased defect formation, indicating a transition from exfoliation-dominant to fragmentation-dominant behaviour. Multi-scale characterisation confirmed wrinkled few-layer GO nanosheets with retained oxygen-bearing functionalities, limited agglomeration, and a stable aqueous colloidal dispersion, supported by ζ ≈ –36 mV and D hyd ≈ 635 nm. These findings establish a Raman-guided approach for tailoring structurally coherent and colloidally stable GO dispersions, providing practical insight into improving dispersion efficiency and reinforcing performance in cementitious composites.