Cobalt oxide nanoparticle

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The cathodes of lithium-ion batteries are often made of lithiated oxides of cobalt, nickel, or manganese, that can readily and reversibly incorporate lithium ions in their molecular structure. Cobalt oxide nanomaterials, such as nanotubes,^[1] offer high surface-to-volume ratio and short path lengths for lithium cation transport, leading to fast charging capabilities. However, capacity, coulombic efficiency, and cycle life may suffer due to excessive formation of SEI. The nanowires may incorporate other substances, for example, diphenylalanine.^[5]

Cobalt oxide particles may be anchored on substrates such as graphene to improve the dimensional stability of the anode and to prevent particle aggregation during lithium charge and discharge processes.^[2]

Gas Sensor

Hollow nanospheres of cobalt oxide have been investigated as materials for

Cobalt oxide nanoparticles have been observed to readily enter cells, a property that conceivably could lead to applications in hyperthermic treatment, gene therapy and drug delivery. However, their toxicity is an obstacle that would have to be overcome.^[6]

Synthesis

Hydrothermal

Cobalt oxide is often obtained by hydrothermal synthesis in an autoclave.^[7]

One-pot hydrothermal synthesis of metal oxide hollow spheres starts with carbohydrates and metal salts dissolved in water at 100-200 °C. The reaction produces carbon spheres, with metal ions integrated into the hydrophobic shell. The carbon cores are removed by calcination, leaving hollow metal oxide spheres. Surface area and thickness of the shell can be manipulated by varying the carbohydrate to metal salt concentration, as well as the temperature, pressure, and pH of the reaction medium, and the cations of the starting salts.^[8] The completion time for the procedure varies from hours to days.^[9]

A drawback of this approach is its smaller yield compared to other methods.

Thermal decomposition

Another route to the synthesis of cobalt oxide nanoparticles is the thermal decomposition of organometallic compounds. For example, heating the metal salen complex bis(salicylaldehyde)ethylenediiminecobalt(II) ("Co-salen") in air to 500 °C.^[10][11] The precursor Co-salen can be obtained by reacting cobalt(II) acetate tetrahydrate in propanol at 50 °C under nitrogen atmosphere with the salen ligand (bis(salicylaldehyde)ethylenediimine).^[11]

From anchored precursors

Cobalt oxide/graphene composite are synthesized by first forming

Safety

Like most cobalt compounds, cobalt oxide nanoparticles are toxic to humans and also aquatic life.^[12][13]

References