Sublimation Kinetics for Individual Graphite and Graphene Nanoparticles (NPs): NP-to-NP Variations and Evolving...

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Understanding nanoparticle behavior is crucial for applications in catalysis, energy, and electronics.
• Sublimation rates and surface properties of nanoparticles (NPs) differ significantly from bulk materials.
• The role of surface structure, such as edge and defect sites, on NP sublimation is not fully understood.

Purpose of the Study:

• To quantify sublimation rates of individual graphite and graphene nanoparticles as a function of temperature.
• To investigate the influence of surface structure and changes over time on sublimation kinetics.
• To explore the relationship between sublimation rates and the emissivity of nanoparticles.

Main Methods:

• Employed single nanoparticle mass spectrometry to measure sublimation rates.
• Studied individual graphite and graphene nanoparticles across a range of temperatures.
• Analyzed changes in sublimation rates and activation energies after partial sublimation.

Main Results:

• Initial sublimation rates of NPs were approximately 400 times faster than bulk graphite.
• Sublimation rates decreased over time but remained significantly higher than bulk rates.
• Initial low activation energies doubled after sublimation, correlating with surface 'smoothing' and removal of low-coordination sites.

Conclusions:

• High densities of edge and defect sites on NP surfaces enhance sublimation rates.
• Preferential sublimation of less stable sites leads to atomic-scale surface smoothing.
• Sublimation rates and emissivity are anticorrelated, with high defect densities enhancing sublimation but suppressing emissivity.