Yeast driven self exfoliation and functionalisation of graphene

We report an eco-friendly, economical and green approach to synthesize few-layers of functionalised graphene from large graphite flakes and chunks without the aid of any external mechanical forces. Here, we demonstrate a fermentation process aided by friendly microbes like yeast to effortlessly exfoliate graphite to graphene with a high yield. The evident flaking and delamination of graphene layers, characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy, confirmed the successful exfoliation of graphite to few-layer graphene (~10 nm in thickness). The gate-to-gate life cycle assessment of the developed method identified the environmental hotspots of the process. The biofunctionalized graphene (as suggested by Fourier transform infrared (FTIR) spectroscopy) was explored for its application in NH4+ sensing, where it exhibited the limit of detection to be ~20 ppm. The detection mechanism was explained based on Raman and FTIR spectroscopy which revealed the functional state and lattice changes introduced in the graphene layers by NH4+ ions. Our study demonstrates a novel, cost-effective exfoliation of graphite using off-the-shelf materials in laboratories or kitchens and has the potential to be scaled up to industry levels. The yeast cells also exhibited their potential in flaking off the bulk MoS2 structure into few-layer MoS2 sheets.