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In this study, ultrasonically driven biosynthesis of zinc oxide nanoparticles (ZnO NPs) using Swietenia macrophylla seed ethyl acetate fraction (SMEAF) has been reported. X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed the presence of a pure hexagonal wurtzite structure of ZnO. Field emission scanning electron microscope images revealed the formation of uniquely identifiable uniform rice-shaped biologically synthesized ZnOSMEAF particles. The particle sizes of the biosynthesized NPs ranged from 262 to 311 nm. The underlying mechanisms for the biosynthesis of ZnOSMEAF under ultrasound have been proposed based on FTIR and XRD results. The anticancer activity of the as-prepared ZnOSMEAF was investigated against HCT-116 human colon cancer cell lines via methyl thiazolyl tetrazolium assay. ZnOSMEAF exhibited significant anticancer activity against colon cancer cells with higher potency than ZnO particles prepared using the chemical method and SMEAF alone. Exposure of HCT-116 colon cancer cells to ZnOSMEAF promoted a remarkable reduction in cell viability in all the tested concentrations. This study suggests that green sonochemically induced ZnO NPs using medicinal plant extract could be a potential anticancer agent for biomedical applications.

Graphene is an advanced carbon functional material with inherent unique properties that make it suitable for a wide range of applications. It can be synthesized through either the top–down approach involving delamination of graphitic materials or the bottom–up approach involving graphene assembly from smaller building units. Common top–down approaches are exfoliation and reduction while bottom–up approaches include chemical vapour deposition, epitaxial growth, and pyrolysis. A range of materials have been successfully used as precursors in various synthesis methods to derive graphene. This review analyses and discusses the suitability of conventional, plant- and animal-derived, chemical, and fossil precursors for graphene synthesis. Together with its associated technical feasibility and economic and environmental impacts, the quality of resultant graphene is critically assessed and discussed. After evaluating the parameters mentioned above, the most appropriate synthesis method for each precursor is identified. While graphite is currently the most common precursor for graphene synthesis, several other precursors have the potential to synthesize graphene of comparable, if not better, quality and yield. Thus, this review provides an overview and insights into identifying the potential of various carbon precursors for large-scale and commercial production of fit-for-purpose graphene for specific applications.