Bias-switchable photoconductance in surface-modified graphene oxide by green synthesized ZnO nanoparticles

This study provides an environmentally friendly method for synthesizing Zinc oxide (ZnO) nanoparticles through Adhatoda vasica extracts as plant-mediated reducing agents. ZnO-GO nanostructures are prepared using microwave irradiation, while a modified Hummer`s method was employed for graphene oxide (GO) synthesis. The thorough characterization establishes the purity, phase and structural conformation of the synthesized ZnO-GO NCs. The observation of ZnO nanoparticles accumulating over the GO surface through High-Resolution Transmission Electron Microscopy and Scanning Electron Microscopy validates the formation of nanocomposites. The resulting ZnO-GO nanocomposites displayed remarkable and broad photoresponsivity across various wavelengths. Notably, at 480 nm, photoresponsivity is found to be a maximum of 0.47 mA/W, whereas it is 0.29 mA/W and 0.21 mA/W at 520 nm and 670 nm respectively. We have achieved responsiveness of 0.48 µA/W and detectivity of 13.9 × 10 <sup>6</sup> Jones at 480 nm with biasing voltage of 1 nV which reflects their potential for self-biased optoelectronic devices. Thus, the photodetector demonstrates a positive photoresponse within the voltage range of 5–30 volts while exhibiting a negative photoresponse in the range of 1–100 nanovolts. This aspect introduces a novel and unprecedented characteristic to the device`s behavior. Overall, the integration of eco-friendly synthesis methods, comprehensive characterization, and device performance puts this work with promising implications for sustainable and advanced technology development.