Femtosecond Laser Interaction with Graphene Oxide Aqueous Solution

Abstract

In this study fs pulsed laser of wavelength 800 nm was used to reduce two sets of aqueous graphene oxide solution namely low (0.5 mg/mL) and high concentration (6.2 mg/mL). It was found that after fs laser treatment the surface roughness of the graphene oxide flakes was reduced by 95.6% and 66% for the high and low GO concentration films respectively. It was also found that the resistivity of high concentration (6.2 mg/ml) rGO films was enhanced by 4 orders of magnitude as a result of the laser treatment which could raise the electron mobility of the rGO films close to that of pristine graphene films. The C-O atomic ratio for the high concentration graphene oxide samples was found to increase by 3 times after 6 hrs of laser treatment. A novel technique of graphene oxide sol-gel (GOSG) fabrication was introduced where GOSG was obtained by placing the laser focal point at the solution/air interface. By manipulating the exposure parameters such as the ablated volume, laser energy and focal length, the GOSG was obtained at various times in the range of as 8 min to 7 hrs. The chemical analysis (XPS) revealed the reduction of the COOH molecules as a result of the exposure process, which is due to removing the OH- from the GO sheets and vaporization of the water content within the solution. Surface morphology analysis using AFM and SEM showed that all GOSG thin films except the 7 hrs one depicted a high surface roughness and porous surface area with randomly stacked graphene oxide layers. However, a smooth stacking layered structure and the smallest average surface roughness was observed in the 7 hrs GOSG, which was pertained the behavior of pure graphene as proved by the FTIR analysis.