Fundamental Study of the Dispersion of Carbon Nano-Onions

Abstract

Since the discovery of the fullerene C60 in 1985 by Curl, Kroto and Smalley, carbon nanomaterials have been the focus of interdisciplinary chemical research. Multi-shell fullerenes, known as carbon nano-onions (CNOs) discovered by Ugarte in 1992, are structured by concentric shells of carbon atoms. Different methods for their synthesis have been developed and their properties have been widely studied. In addition, the chemical functionalization of CNOs has been investigated and several synthetic pathways were found to be applicable for the introduction of a variety of functional groups. The purpose of this project is to make the oxidized CNOs bear a relative centrifugal force at different time durations to analyzed how well the material disperses. This in turn, will provide a fundamental concept for the synthesis efficiency. According to preliminary results, there is a tendency on which the concentrated CNOs difference in weight gets narrow, as duration of the centrifugal force increases. Chemically modified CNOs were probed in different fields of application and have revealed to be a promising nanomaterial that attracts a growing interest among researchers and opens new avenues for investigation. Its development starts using nano-diamonds; a carbon nanomaterial of strong structure which undergoes through a temperature of approximately 1650°C inside a furnace to obtain the CNOs structure. The CNOs are then oxidize through synthesis that requires a constant temperature and stirring to attain oxygen based functional groups. Another way to obtain the oxygen based functional groups is through heating the sample at 400°C for two hours; these procedures are then analyzed to determine the efficiency of functionalization. The preliminary elemental detection of oxygen atoms was gathered by Energy-Dispersive Spectroscopy. To detect states in the CNO’s molecular system, Raman Spectroscopy was utilized to confirm the carbon structure of CNOs by the identification of the peaks D and G characteristic of this carbon material. An in-depth characterization analysis was done using X-Ray Diffraction, providing detailed information about chemical composition, and crystalline structure. The morphology and microstructure of CNOs were studied using a Transmission Electron Microscope and Scanning Electron Microscopy. Through Cyclic Voltammetry, CNO’s ink was prepared to characterize electrochemically comparing both functionalization processes. To study its catalytic properties, Oxygen Reduction Reaction (ORR) experiments was conducted utilizing Rotating Ring-Disk Electrode (RRDE). The ORR experiments were carried out by varying the rotation rates of the RRDE at 100, 400, 900, 1600 and 2500 rpm.