Ultrasonic Duration Dependent Defect Engineering and Morphological Evolution in Graphene Oxide

Abstract

Abstract This work thoroughly investigates how different durations of ultrasonic treatment affect the structural, chemical, and morphological features of graphene oxide (GO) obtained from graphite through the Staudenmaier method. To ensure efficient exfoliation, a dual-source ultrasonic configuration (40 KHz, 100 W bottom transducer combined with a 100 W submerged probe) was utilized in pulse mode. We elucidate the structural evolution throughout the sonication duration (3, 5, 7, and 12 min) using Raman spectroscopy, x-ray diffraction (XRD), and scanning electron microscopy (SEM) under controlled thermal conditions. The initial GO, which underwent 3 min of sonication, had thick, stacked flakes bearing the markings of an XRD peak at 10.46° (0.845 nm d-spacing), suggesting the presence of highly oxidized and expanded layers evident from the peak intensity ratio ( I D / I G ) of 1.11. The structural evolution of GO during sonication resulted in significant reduction and rearrangement toward an optimum at 7 min, marked by a single dominant remaining reduced graphene oxide (rGO) XRD peak at 26.17° (0.340 nm d-spacing) and a decrease in I D / I G to 0.59, indicating substantial sp 2 lattice restoration and deoxygenation. This was accompanied by substantial structural restoration and deoxygenation. The 5-min mark provided morphological insight into the initial stage of exfoliation of GO, marked by thin, wrinkled sheets. However, prolonged treatment of 12 min led to an energy saturation effect, causing the I D / I G to increase to 0.72 and the dominant XRD peak to shift back toward larger d-spacing at 20.19° (0.439 nm). This suggests a reversal of structural benefits due to mechanical fragmentation and disordered restacking induced by excessive acoustic cavitation.