Pulsed laser irradiation for environment friendly reduction of graphene oxide suspensions

Graphene oxide (GO) sheets were synthesized through a modified Hummers' method. Using high resolution transmission electron microscopy the thickness of the GO sheets in a multilayer structure of stacked GO sheets was found ∼0.8 nm. A nanosecond pulsed laser (with wavelength of 532 nm and average power of 0.3 W) was applied for effective and environment friendly reduction of the GO sheets in an ammonia solution (pH ∼9) at room temperature conditions. The deoxygenation of the GO sheets by the pulsed laser reduction method was confirmed by using UV-visible, Fourier transform infrared, X-ray photoelectron spectroscopy (XPS) and thermo gravimetric analysis. Based on XPS analysis, the O/C ratio of the GO sheets decreased from 49% to 21% after 10 min laser irradiation. This reduction efficiency was comparable with the efficiency achieved by hydrazine which yielded the O/C ratio of 15% at 80 °C after 10 min. Using Raman spectroscopy it was found that the pulsed laser reduction method resulted in nearly no aggregation of the reduced GO sheets in the ammonia solution. These results can help to further promotion and application of pulsed lasers in environment friendly reduction of GO.