Mangifera indica, Ficus religiosa and Polyalthia longifolia leaf extract-assisted green synthesis of graphene for transparent highly conductive film

Abstract

A green approach to synthesize graphene nanosheets (Gns) by reduction of graphene oxide (GO) using Mangifera indica, Ficus religiosa or Polyalthia longifolia leaf extract as reducing agent has been demonstrated. Further, transparent conducting films (TCFs) have been fabricated by spray coating of the synthesized Gns and the optoelectrical properties of the TCFs have been investigated. Of the three leaf extracts, Mangifera indica offers the best alternative reducing agent for the green synthesis of Gns at large scale. Raman spectroscopy reveals that GO has been deoxygenated significantly, with a Raman D to G band intensity ratio of ∼1.21, while the attainment of a C/O ratio of ∼4.58 in the synthesized Gns has been confirmed by elemental analysis. The TCF fabricated after thermal graphitization (900 °C for 1 h) of the spray coated Gns film shows a sheet resistance of ∼2.08 kΩ □⁻¹ and transmittance of ∼57.31% at 550 nm. The study suggests significant potential for the application of plant leaf extracts as non-toxic reducing agents in large-scale production of Gns. Apart from providing an alternative to hazardous reducing agents, this approach opens the possibility of preparation of Gns at large scale by using more accessible natural resources with mild synthesis conditions.