Effect of thermal and gold nanoparticles on the optoelectronic properties of graphene oxide.

In this study, the effects of thermal reduction and gold nanoparticles on the optoelectronic properties of thin graphene oxide films was systematically investigated. Thermal annealing partially reduced graphene oxide to reduced graphene oxide, leading to a restoration of the sp2 carbon network and a marked improvement in electrical conductivity. Under 405 nm laser illumination with a power of 50 mW and a bias voltage of 30 V, the reduced graphene oxide photodetector exhibited a high photocurrent of 33.3 µA and a responsivity of 0.67 mA W⁻1, with rise and fall times of approximately 11.12 s and 10.27 s, respectively. Incorporation of Au NPs resulted in the reduced graphene oxide/gold nanocomposite showing a lower photocurrent (12.23 µA) and responsivity (0.25 mA W⁻1); however, it demonstrated improved reversibility and a faster rise time of 9.87 s. The external quantum efficiency was estimated to be ~0.21% for reduced graphene oxide and ~0.08% for reduced graphene oxide/gold. These results indicate that thermal reduction is the dominant factor in enhancing photoresponse, while Au NPs primarily improve response stability and reversibility. The findings highlight the potential of reduced graphene oxide-based structures, with controlled gold nanoparticle incorporation, for developing efficient and stable graphene-based photodetectors.