Nonlinear Optical Absorption of Carbon Nanostructures Synthesized by Laser Ablation of Highly Oriented Pyrolytic Graphite in Organic Solvents

In this study, Highly Oriented Pyrolytic Graphite was ablated in various polar and nonpolar solvents by Q-switched neodymium: yttrium-aluminum-garnet laser (wavelength=1064 nm, frequency=2 kHz, pulse duration=240 ns). Then, the products were examined using Scanning Electron Microscopy and UV-Vis spectroscopy. The images showed that different carbon structures such as cauliflower-like structures in benzene, spiral integrated forms in toluene, organic integrated networks in hexane, and nanoparticles in ethanol were formed. In n-methyl-2-pyrrolidone (NMP), sheets and bulk deformed structures were seen. Also, in Dimethylacetamide, particles in different stages of growth could be detected. The nonlinear optical absorption (NLA) behaviors of the products were investigated by exposing them to a 532 nm nanosecond laser using the Z-scan technique. The saturated NLA coefficient, obtained from structures of NMP and hexane-based synthesized samples, are 1.1×[(10)]^(-8) and -2.4×[(10)]^(-8) cm w^(-1), respectively. The saturable absorption responses of these samples were switched to the reverse saturable absorption responses in the other synthesis mediums. The maximum nonlinear absorption coefficient of 10.2×[(10)]^(-8) cm w^(-1) was measured for spiral integrated superstructures, produced in the toluene medium.