Investigating the Effects of Different Liquid Environments on the Characteristics of Multilayer Graphene and Graphene Oxide Nanosheets Synthesized by Green Laser Ablation Method

The present study is dedicated to investigate the effects of ablation environment on the characteristics of carbon nanostructures synthesized by pulsed laser ablation method; particularly for graphene and Graphene Oxide (GO) nanosheets. The beam of a Q-switched Nd:YAG laser of 532 nm wavelength at 7 ns pulse width and 0.5 J/cm(2) fluence is employed to irradiate the similar graphite targets as the constant experimental conditions while liquid nitrogen and 0.04 M Cetyltrimethylammonium bromide (CTAB) solution are applied as the variable liquid environments. Also, characteristics of the final ablation products are investigated in detail via UV-Vis-NIR spectroscopy, X-ray diffraction pattern, Raman scattering spectrum, and Transmission electron microscopy (TEM). XRD and UV-Vis-NIR analysis exhibit the oxidation of graphene nanosheets in CTAB solution owing to the presence of oxygen molecules in ablation environment. Raman results indicate that the produced graphene nanosheets in liquid nitrogen medium have represented many layers, low level of defects and large SP2 domains size, while the GO nanosheets which are produced in CTAB solution have represented higher level of defects and smaller SP2 domains size. Furthermore, the characteristic features in Raman spectra also propose that there are two different graphene materials: AB stacked multilayer graphene and disoriented or randomly stacked multi layer GO nanosheets. The experimental results suggest that the characteristics of liquid environment such as nonpolar or cationic properties are the most effective parameters in the mass rate of carbon nanoparticles production. Our results provide useful guidance towards the production of carbon nanostructures with the desired attributes.