From graphene oxide (GO) to reduced graphene oxide (rGO) films: A hybrid approach combining film transfer and vapor reduction for enhanced structural and optical properties

• The GO film was successfully transferred intact onto a glass substrate using a water-based film transfer method. • Hydrazine vapor reduction for 60, 120, and 240 s removed oxygen functional groups as evidenced by FTIR and further confirmed by EDX through an increased C/O ratio in the 240 s sample while measurable sheet resistance was obtained only for the 120 and 240 s samples. • The morphology changed significantly from GO to rGO, showing a reduction in surface roughness (Sa) and an increase in film thickness caused by wrinkling and layer rearrangement during the restoration of the sp² carbon network. • The optical and structural analyses reveal a correlation among the increased extinction coefficient (k), the π–π transition shift in UV–Vis spectra, the higher Raman ID/IG ratio, and the reduced sheet resistance, indicating partial recovery of sp²-bonded carbon domains. Reduced graphene oxide (rGO) films were successfully fabricated via hydrazine vapor reduction with durations of 60, 120, and 240 s using a water-based transfer approach. The transfer process exploits the surface tension of water to release GO films from mixed cellulose ester (MCE) membranes and deposit them smoothly onto glass substrates, producing homogeneous and residue-free layers. This study investigates the influence of reduction time on the morphological, structural, and optical evolution of rGO films. Characterization using TMS, FTIR, UV–Vis, Four-Probe, SEM, Raman, and TEM reveal that longer reduction durations enhance the removal of oxygen functional groups, restore the sp² carbon network. The film surface becomes smoother, with the roughness (Sa) decreasing from 692 to 397 nm, while the thickness increases due to uneven rearrangement and wrinkling of graphene sheets. FTIR and UV–Vis analyses confirm the progressive loss of oxygen functionalities and increased π-electron delocalization, which are consistent with reduced sheet resistance, higher extinction coefficients (k), and a darker film appearance. TEM images and SAED patterns reveal more crumpled graphene sheets and reduced interlayer spacing (d-spacing) in the (002) planes, indicating oxide removal and structural densification. These findings align with SEM observations showing a more porous morphology and an elevated C/O ratio in rGO compared to GO. Raman spectra exhibit an increased ID/IG ratio and a shift in the G band, reflecting enhanced defects and strain within sp² domains. Overall, the hydrazine vapor reduction method proved to be effective in forming uniform and well-printed rGO films with altered electrical and optical characteristics due to the restoration of the sp² carbon network.