Room-temperature synthesis of carbon nano-onions by B₄C sonication in water

Abstract

Carbon nano-onions (CNOs) are carbon nanomaterials with a wide range of applications. The synthesis of CNOs from carbon and organic sources has been extensively studied, however, only a few studies have reported the synthesis of CNOs from inorganic sources. This study reports a novel process for synthesizing CNOs from B₄C—the only inorganic carbon source—by one-step sonication in water at room temperature. Compared with previous methods, this process is easier and performed under gentler conditions and lower temperatures. Transmission electron microscopy (TEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and scanning transmission electron microscopy–electron energy loss spectroscopy (STEM-EELS) were used to characterize the synthesized samples. TEM revealed CNOs with diameters of approximately 20–30 nm, and FTIR and STEM-EELS indicated the presence of oxygen-containing functional groups on the CNOs. The proposed method of obtaining CNOs from an inorganic carbon source provides novel insights into the mechanism of CNO generation and its functionalization.