^aDepartment of Physics, GSS, GITAM (Deemed to be University), Visakhapatnam, 530045, India

^bPhysics Department, University of Turin, Via. P. Giuria 1- 710125 Turin, Italy.

^cSchool Of Physics, University of Hyderabad, Hyderabad 500046, India.

Graphene oxide and its nanocomposites play a crucial role in various applications. Laser irradiation is a low-cost technique to tune the graphene oxide material, and a detailed study of the vibrational modes and structural changes during the laser–graphene oxide interaction is required. The evolution of defect modes and reduction process in graphene oxide at varying laser power and different exposure time duration, respectively, via Raman spectroscopy, is of interest in the present study. Graphene oxide (GO) is synthesized via Improved Hummer's method and characterized by X-Ray Diffraction (XRD), Thermogravimetric analysis (TGA), Field Emission Scanning Electron Microscopy (FE- SEM), Energy Dispersive X-ray analysis (EDX), UV-Vis-NIR and Raman spectroscopy.

The first-order Raman spectrum of GO consists of broad D and G peaks around 1350 and 1584 cm- 1, respectively, and the broad second-order band around 2700 cm- 1. Using the Lorentzian function, the first-order band is deconvoluted into five modes and the second- order into four modes. The peak positions and FWHM of these modes undergo indicative changes. The variations in the intensity ratios of the defect modes and the (Di,nf – Gapp) with laser power at different exposure time durations indicates the predominance of edge defects and reduction of graphene oxide, respectively. These results broaden the understanding of the effect of laser power over different time durations on the graphene oxide features. Our study provides quantitative information on the laser-GO interaction.