Green and cost-effective synthesis of 2D and 3D graphene-based nanomaterials from Drepanostachyum falcatum for bio-imaging and water purification applications

Herewith, we demonstrate a novel top-down approach for the cost-effective consecutive synthesis of 2D/3D graphene-based materials (GBM) from the extract and fibrous parts of the Drepanostachyum falcatum plant, using a two-stage thermal approach. At low temperature (150 degrees C), the extract of the D. falcatum showed the formation of a fluorescent 2D skeleton of the GBM i.e., metal-doped graphene oxide sheets (MDGOs) in presence of ethanol. On the other hand, the pyrolysis (similar to 300 degrees C) of the fibrous part showed the formation of a 3D skeleton of the graphene nanoribbons (GNR) in the N-2 atmosphere. The presence of extensive pi-pi conjugated interactions with oxidative functional moieties in 2D-MDGOs is responsible for their blue fluorescent nature under UV irradiation at 365 nm. Meanwhile, 2D-MDGOs show excellent potential as a bio-imaging probe for non-tumorigenic prostate epithelial RWPE-1 cells. However, the very low cytotoxicity of 2D-MDGOs played a crucial role in upholding their bio-imaging potential. Simultaneously, the hydrophobic nature of 3D-GNR showed better adsorption towards the organic pollutants (dye) from the aqueous phase. The adsorption phenomenon of 3D-GNR was very fast and effective towards the removal of methylene blue (MB). Moreover, the Langmuir adsorption capacity for MB dye was found to be 31.94 mg/gm. This is the first time we are reporting the dual synthesis of 2D and 3D GBMs simultaneously, with different applicative potentials. Further, noticeable and in-depth observations were made for studying the reaction kinetics of the reaction to find a formal analytical connection between productivity, adsorptive, and applicability of 3D-GNR. Moreover, the market-based-cost analysis showed the huge industrial potential of these materials, which also make them inevitable and promising candidates for futuristic growth in their respective application in water purification.