Abstract: A nanostructure includes a plurality of substantially spherically curved carbon layers having diameters in a range of 1 nanometer to 1000 nanometers and a plurality of halogen atoms attached to an outer convex side of the carbon layers. A composition of matter includes a liquid fuel and an additive including at least one liquid and a plurality of carbon nano-onions. A method of fabricating an additive for liquid fuel includes creating a carbon-based material using a plasma in an environment including at least one hydrocarbon gas and/or at least one liquid containing hydrocarbons, organometallic metal-complex, and/or element-organic compounds, evaporating organic material from the carbon-based material, halogenating the carbon-based material, and extracting carbon nano-onions from the halogenated carbon-based material.