The best conditions for the nucleation of carbon nanoparticles in laser-induced plasma

Abstract

Despite the existence of many more efficient methods of producing carbon nanoparticles, ablation of a carbon target by a laser pulse remains important. It enables studying the bare properties of nanoparticles, not contaminated with reagents or reaction products. The present work analyses the mechanisms of nucleation and growth of nanoparticles in carbon vapours generated during ablation of graphite with a nanosecond laser pulse. The role of both the homogeneous and the heterogeneous (ions) nucleation was investigated, defining the areas of their occurrence. It has been shown that the most favourable conditions are high pressure of the order 1 GPa and relatively low temperature of about 15,000 K. Such conditions are obtainable when ablation occurs in a liquid and the fluence of the laser pulse is low, exceeding the ablation threshold about 2.7 times only. The resulting nanoparticles are relatively homogeneous and have a diameter of approximately 2.5-5 nm.

The Luminescence of Laser-Produced Carbon Nanodots: The Effect of Aggregation in PEI Solution

“…Aqueous carbon nanodots solutions were obtained via pulsed laser ablation in water using the procedure described in [29].…”

“…The concentration of carbon nanodots in all CND/PEI systems was kept constant (0.5 mg/mL). This value was obtained based on the ablation yield calculations presented in [29]. Table 1 summarizes sample names, the procedure of mixing and respective concentration of PEI in mixture.…”

“…In comparison to CNDs(aq) (Figure 1b), all samples exhibited an increase in their dimensions after the addition of polymer to the carbon-dot colloid. The agglomeration of CND/PEI systems can be attributed to electrostatic interactions between cationic PEI and anionic CNDs, leading to the compensation of net surface charge [22,29].…”