Synthesis of novel CoCx@C nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Nanomedicine

Background:

• Developing novel nanomaterials for biomedical applications is crucial.
• Cobalt carbide nanoparticles offer unique magnetic properties but require surface modification for biocompatibility.
• Carbon encapsulation is a promising strategy to enhance nanoparticle stability and reduce toxicity.

Purpose of the Study:

• To synthesize and characterize novel cubic phase cobalt carbide nanoparticles encapsulated in carbon shells (CoC(x)@C).
• To evaluate the physicochemical properties, including magnetic behavior and particle size.
• To assess the cytotoxicity and cobalt ion release profile for potential biomedical applications, particularly targeted drug delivery.

Main Methods:

• Synthesis of CoC(x)@C nanoparticles via pulsed plasma in liquid ethanol.
• Characterization using X-ray diffraction (XRD) for crystal structure and lattice parameter determination.
• X-ray absorption fine structure (XAFS) spectroscopy for electronic structure analysis.
• High-resolution transmission electron microscopy (HRTEM) for morphology and carbon coating visualization.
• Dynamic light scattering (DLS) for aggregate size analysis.
• Measurement of saturation magnetization.
• Cytotoxicity assays (MTT assay and DNA fragmentation) on MCF-7 cells.
• Cobalt ion release study using ethylenediaminetetraacetic acid (EDTA) chelation.

Main Results:

• Successfully synthesized monolithic cubic phase CoC(x) nanoparticles encapsulated in carbon shells.
• XRD refinement confirmed the cubic phase with a larger lattice parameter compared to reference CoC(x) and Co phases.
• XAFS spectra showed distinct features compared to commercial cobalt and cobalt oxide.
• HRTEM confirmed the presence of a ~10 nm crystallite size with a thin carbon coating.
• DLS indicated secondary particle aggregation in water (20-40 nm).
• High saturation magnetization of approximately 120 emu g⁻¹ was observed.
• CoC(x)@C nanoparticles exhibited relatively low cytotoxicity compared to metallic cobalt and iron oxide nanoparticles.
• Minimal cobalt ion release was detected from the CoC(x)@C nanoparticles.

Conclusions:

• The pulsed plasma in liquid method provides a novel route to synthesize cubic phase CoC(x)@C nanoparticles.
• The carbon shell effectively passivates the CoC(x) core, leading to reduced cytotoxicity and ion leaching.
• The magnetic properties and low toxicity suggest CoC(x)@C nanoparticles are suitable for biomedical applications, including targeted drug delivery systems.