Photothermal reduction of thick graphene oxide multilayer films via direct laser writing: Morphology, structural and chemical properties

Thick graphene oxide (GO) multilayer films were deposited on polyethylene terephthalate substrates. Photothermal reduction of thick GO multi layer films was performed via direct laser writing using a continuous wave 405 nm semiconductor laser. Direct laser writing speed and power density was varied in the range of 0.94-1.24 s/line and 1.69-2.71 x 10(5) W/cm(2), respectively. A systematic analysis employing scanning electron microscopy, Raman scattering, X-ray photoelectron spectroscopy and X-ray diffraction analytical techniques was performed in order to characterize morphological, structural and chemical changes of thick GO multilayers upon reduction to reduced GO (rGO). It was demonstrated that by adjusting laser direct writing parameters it is possible to finely tune the GO photothermal reduction process and to produce rGO morphologies with different porosity, I-D/I-G1 and I-G2/I-G1 ratios, avoiding the use of toxic and harmful reducing agents.