▎ 摘　　要

The development of an approach for producing a very low defect graphene with simple and green technique is essential for highly conductive graphene thin film preparation. This paper describes the preparation of graphene thin film from aqueous processed graphene dispersion using alkaline lignin (AL) as surfactant, a low cost route to produce high yield (0.72 +/- 0.05 mg/mL) with free structural defect of graphene sheets. In this work, the cationic properties of AL adsorbed on the exfoliated graphene sheet surfaces are easily removed via centrifugation, thermal and annealing treatments so that prepared graphene thin films exhibit good electrical conductivity and defect ratio reduction. Using optimum AL solution with concentration of 0.5 mg/mL, the precursor graphite is successfully being exfoliated into few layer graphene sheets (<4 layers) without significant basal plane defects as verified by XRD and Raman spectroscopy with the ratio of D band and G band intensities (I-D/I-G) value as low as 0.17. The mechanism of graphene dispersion formation are elucidated and thin layer of conductive graphene films are deposited onto cleaned substrates via dip coating technique. Untreated graphene thin film exhibited an electrical conductivity around 615.8 S/m at room temperature, surprisingly, the improvement of electrical conductivity as high as 53763 S/m is obtain after thermal and annealing treatments. The prepared graphene thin film also demonstrated a very high transparency in visible region at 550 nm (>= 90%). (C) 2017 Elsevier B.V. All rights reserved.