Date Published: February 3, 2017
Publisher: Public Library of Science
Author(s): Adhiraj Dasgupta, Joy Sarkar, Manosij Ghosh, Amartya Bhattacharya, Anita Mukherjee, Dipankar Chattopadhyay, Krishnendu Acharya, Yogendra Kumar Mishra.
Chemical reduction of graphene oxide (GO) to graphene employs the use of toxic and environmentally harmful reducing agents, hindering mass production of graphene which is of tremendous technological importance. In this study we report a green approach to the synthesis of graphene, bio-reduced by crude polysaccharide. The polysaccharide reduces exfoliated GO to graphene at room temperature in an aqueous medium. Transmission electron microscopy image provides clear evidence for the formation of few layer graphene. Characterization of the resulting polysaccharide reduced GO by Raman spectroscopy, Fourier transform infrared spectroscopy and Energy dispersive X-ray analysis confirms reduction of GO to graphene. We also investigated the degree of biosafety of the reduced GO and found it to be safe under 100 μg/ml.
Due to the electronic, mechanical, thermal and optical uniqueness, two-dimensional graphene nanosheets (GNS) have significantly transformed areas of nanoscience [1,2]. Even though recent research has produced some unique and versatile 2-D nanostructures , GNS still holds great promise for potential applications in nanoelectronics , sensors [5,6], nanocomposites  and other technological fields. Harnessing these characteristics, which renders GNS its potential, necessitates a large-scale production of the nanosheets. Micromechanical cleavage , epitaxial growth , solution-based chemical reduction  and a few other methods are mainly applied for production of GNS. Usually, chemical reduction of GO was carried out using hydrazine and its derivatives [10,11], but its high toxicity and instability makes the procedure potentially hazardous and asks for great care. GNS has a tendency of π – π stacking, making the bulk synthesis of it a key challenge. This can be overcome by the attachment of other molecules or polymers on to the nanosheets. Recently, scientists have reported synthesis of GNS under much milder conditions using molecules like ascorbic acid , reducing sugars like glucose and fructose , which are ecofriendly and very effective in reducing GO to GNS.
In conclusion, a green approach to the synthesis of graphene nanosheets is reported using exfoliated graphene oxide as the precursor and a crude fungal polysaccharide as the reducer. The use of an environment-friendly reducing and capping agent is what this method derives its merit from. The method should find practical applications in bulk-synthesis of graphene nanosheets. Also, from all the toxicity endpoints studied in human PBMCs, this newly synthesized nanoparticle could be considered biologically safe at concentrations below 100 μg/ml.