Carbon nano-onions (CNOs) or multilayered fullerenes have received
considerable attention in diversified research areas such as supercapacitors, fuel cells,
batteries, photovoltaics, and biosensors due to their unique physicochemical, optical,
catalytic, and electronic properties. These structures were first observed in 1992, and
ever since, a considerable amount of research on their physical properties and
development of CNOs based supercapacitors and sensors has been successfully
witnessed. CNOs are prepared via different experimental techniques, and their
structural and physical properties often rely upon the fabrication process or parameters.
This chapter presents an overview of different methods that have been adapted to
prepare CNOs and their novel properties with a focus on the fundamental curvature
morphology effects. A comprehensive discussion on the potential applications, citing
recent research, is provided. The challenges and the potential directions of CNOs-based
materials with an eye to develop highly efficient and long-term stable CNOs-based
energy storage devices and sensors are also addressed.
Keywords: Anode materials, Carbon nano-onions, Carbon nanomaterials, Fullerenes, Flame-assisted synthesis, Glucose sensors, Immunosensors, Lithiumion batteries, Raman spectra of CNOs, Supercapacitor electrodes