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Hydrothermal synthesis, characterization and seed germination effects of green‐emitting graphene oxide‐carbon dot composite using brown macroalgal bio‐oil as precursor

BACKGROUND: Bio‐oils can be effectively used for the preparation of bio‐based materials owing to their chemical compositions. In this study, brown macroalgal‐derived bio‐oil was used for the synthesis of graphene oxide‐carbon dot composite by a simple hydrothermal process. RESULTS: A simple and facile hydrothermal process was explored for the preparation of green‐emitting graphene oxide‐carbon dot (GO‐CD) composite from brown macroalgal biomass‐derived bio‐oil as carbon source in water medium at 170 °C for 4 h. An aqueous solution of the prepared GO‐CD composite exhibited green emission under ultraviolet (UV) radiation exposure. Raman spectroscopy and transmission electron microscopy analyses confirmed the successful formation of GO‐CD composite. Physicochemical characterizations such as phase structure and optical properties of the GO‐CD were investigated by X‐ray diffraction, UV–visible and photoluminescence analyses. The effects of the GO‐CD composite on the seed germination of mung bean were studied. It was found that, compared with the control (100/0 vol% water; total length of plant ∼20 cm), the 75/25 vol% water/GO‐CD ratio treatment resulted in better plant growth (total length of plant ∼25 cm) under the studied conditions. Further increase in GO‐CD concentration above the optimum level resulted in a decrease in plant growth but did not have a significant effect on the mass, root and leaf mass development. CONCLUSION: Brown macroalgal bio‐oil‐derived graphene oxide‐carbon dot composite were explored for the seed germination of mung bean and the results showed that a low concentration enhanced the plant growth. © 2019 Society of Chemical Industry