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A single nanoparticle (NP) mass spectrometry method was used to measure sublimation rates as a function of nanoparticle temperature (TNP) for a number of individual graphite and graphene NPs. Initially, the NP sublimation rates were ~400 times faster than that for bulk graphite, and there were large NP-to-NP variations. Over time, the rate slowed substantially, though remaining well above the bulk rate. The initial activation energies (Eas) were correspondingly low and doubled as a few monolayer's worth of material were sublimed from the surfaces. The high initial rates and low Eas are attributed to large numbers of edge and other low coordination sites on the NP surfaces, and the changes are attributed to atomic-scale "smoothing" of the surface by preferential sublimation of the less stable sites. The emissivity of the NPs also changed after heating, most frequently increasing. The emissivity and sublimation rates were anti-correlated, leading to the conclusion that high densities of low-coordination sites on the NP surfaces enhances sublimation but suppresses emissivity

Results are presented for thermal emission from individual trapped carbon nanoparticles (NPs) in the temperature range from ~1000 to ~2100 K. We explore the effects on the magnitude and wavelength dependence of the emissivity, ϵ(λ), of the NP size and charge, and of the type of carbon material, including graphite, graphene, diamond, carbon black, and carbon dots. In addition, it is found that heating the NPs, particularly to temperatures above ~1900 K, results in significant changes in the emission properties, attributed to changes in the distribution of surface and defect sites caused by annealing and sublimation.

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O2 oxidation and sublimation kinetics for >30 individual nanoparticles (NPs) of five different feedstocks (graphite, graphene oxide, carbon black, diamond, and nano-onion) were measured using single-NP mass spectrometry at temperatures (T NP) in the 1100–2900 K range. It was found that oxidation, studied in the 1200–1600 K range, is highly sensitive to the NP surface structure, with etching efficiencies (EEO2 ) varying by up to 4 orders of magnitude, whereas sublimation rates, significant only for T NP ≥ ∼1700 K, varied by only a factor of ∼3. Its sensitivity to the NP surface structure makes O2 etching a good real-time structure probe, which was used to follow the evolution of the NP surface structures over time as they were either etched or annealed at high T NP. All types of carbon NPs were found to have initial EEO2 values in the range near 10–3 Da/O2 collision, and all eventually evolved to become essentially inert to O2 (EEO2 < 10–6 Da/O2 collision); however, the dependence of EEO2 on time and mass loss was very different for NPs from different feedstocks. For example, diamond NPs evolved rapidly and monotonically toward inertness, and evolution occurred in both oxidizing and inert atmospheres. In contrast, graphite NPs evolved only under oxidizing conditions and were etched with complex time dependence, with multiple waves of fast but non-monotonic etching separated by periods of near-inertness. Possible mechanisms to account for the complex etching behavior are proposed.