▎ 摘　　要

NOVELTY - Composition comprises: a carbon-based substrate; and cerium oxide nanoparticles on the carbon-based substrate, where the carbon-based substrate comprises a conductive or amorphous carbon. USE - The composition is useful for filtering to scavenge radicals (claimed), which is useful for sensing free radicals e.g. hydroxyl radicals, involving cerium oxide nanoparticles on carbon-based substrate. ADVANTAGE - The composition: maintenances their advantages as their overproduction may lead to irreversible cell damage, among all free radicals, the hydroxyl radical is reactive and dangerous, with short lifetime of nanoseconds, hydroxyl radicals can also be generated inside cells, at mitochondria, human blood, and interstitial fluid; utilizes amorphous carbon is generally cheaper than graphene and graphene oxide, and sensing compositions that include amorphous carbon provide cost savings and cerium oxide nanoparticles have average size of less than 5 nm, preferable 4 nm; utilizes amorphous carbon substrate show significantly improved response to hydroxyl radicals, even compared to sensors; and provides improved fuel cells by scavenging free radicals in filter or membrane placed within the fuel cell. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (a) filter for scavenging radicals comprising the composition; (b) sensor comprising an electrode, a carbon-based substrate on the electrode, and cerium oxide nanoparticles directly on the carbon-based substrate, where the cerium oxide nanoparticles comprise a ratio of cerium (III) to cerium (IV) of at least 0.4; (c) scavenging radicals, comprising detecting free radicals with a sensing composition comprising cerium oxide nanoparticles on a carbon-based substrate; and (d) making the composition, comprising acid-treating a conductive, amorphous carbon to create a functionalized surface on acid-treated amorphous carbon, contacting the functionalized surface with a solution comprising a cerium oxide precursor to organ metallically graft the cerium oxide precursor onto the functionalized surface and create a grafted surface, removing solvent from the grafted surface to produce a product, drying the product to produce a free radical sensing composition and conducting a thermal treatment in inert to remove the precursor ligands.