Exploring morphological diversity of Q-carbon structures through laser energy density variation

This article presents a study on preparing and characterising Q-carbon structures through ultrafast cooling of annealed amorphous carbon using a nanosecond KrF excimer laser. The experiments were conducted under high vacuum conditions. Different Q-carbon structures resembling fibers, clusters, microdots, and combinations of clusters with nanodots were successfully prepared by varying the beam energy density (ranging from 0.6 to 1.8 J cm−2) during the pulsed laser annealing process. The resulting changes in surface morphology were analysed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Additionally, the modified forms of carbon were investigated through energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The findings reveal that increasing the beam energy density during the pulsed laser annealing process led to a corresponding increase in the percentage of sp3 hybridisation in the samples. The highest sp3 content, reaching 83 %, was observed in the sample with the highest energy value of 1.8 J cm−2, where the fastest undercooling occurred. In addition, we evaluated the antibacterial potential of the prepared sample (1.0 J) using two bacterial strains, one gram-positive of S. aureus and one gram-negative of E. coli.