Optical properties of graphene oxide thin film reduced by low-cost diode laser

A non-toxic, fast, low-cost, single step and highly efficient reduction method is proposed in this research for the development of high-quality multilayer graphene film using laser diode. Graphene oxide film is irradiated with a diode laser (808 nm, 6 W) for different exposure times (1, 1.5, 2, 2.5, and 3 min.) to reduce it. Surface damage was observed on the graphene oxide (GO) film for exposure time greater than 3 min and at power 6 W. Different measurement techniques (Raman spectroscopy, Uv-visible absorption, photoluminescence and FTIR) are used to study the optical properties of rGO films. After laser irradiation, the Raman spectra of rGO films showed peaks for the D, G, and 2D bands centered at 1335, 1581, and 2710 cm(-1), respectively. A small increase in the (I-D/I-G) ratio was observed and showed that greater reduction occurred after the graphene oxide film exposure time of 3 min. The as-prepared film of graphene oxide that showed absorption peak at 235 nm was red-shifted to 270 nm after 3 min of laser diode irradiation for reduction. The PL measurements were performed, where the sample was excited by Ar-ion laser (488 nm) and the PL signal was amplified using lock in techniques. The photoluminescence emission spectrum was measured at different positions on the graphene oxide film reduced for 3 min to show the effect of the energy spatial distribution of the laser diode beam on the rGO film. The maximum PL peaks gradually blue shifted and the peak intensities decreased as the measurements go toward the center of the reduced film. The FT-IR spectrum revealed that there are no hydroxyl, carboxyl, and epoxy groups and new peaks were found assigned to functional groups such as CH2, C-H by reducing the graphene oxide with laser diode for 3 min.