Obtenção de óxido de grafeno reduzido a partir de redutores verdes a base de compostos fenólicos de folhas de jambolão (Syzygium cumini)

Abstract

The search for environmentally friendly production of reduced graphene oxide is continuous. Several works suggest the use of green reducers as a substitute for usual reducers such as hydrazine and sodium borohydride. Usually, green reducing agents are plant extracts that have phenolic compounds in its composition. Thus, the present work has as the main goal to synthesize and characterize reduced graphene oxide (RGO) by green reducing using phenolic compounds extracted from leaves jambolana (Syzygium cumini), likewise them characterization. Was verified the influence of the percentage of the phenolic compound present in different solvents extracts of the species Syzygium cumini, typical plant found in the Rio Grande do Sul, the potential reduction of graphene oxide (GO) when compared to usual reductant agent used, the borohydride Sodium. The extracts were assessed for the amount of phenolic composition (tannins, phenolic acids, and flavonoids) by high-performance liquid chromatography (HPLC). To evaluate the structures obtained, all the samples of GO and RGO were characterized by X-ray diffraction (XRD), Raman spectroscopy and the infrared region with Fourier transform (FTIR), scanning electron microscopy (SEM). Also, the thermal stability of the best samples was evaluated by thermogravimetric analysis (TGA). The mixture of water, alcohol, and acetone was proved that the most promising solvent for the removal of phenolic compounds from jambolana's leafs. The characterization of the extracts by HPLC determined that these have in their composition at least gallic acid (hydrolyzable tannin), catechin (condensed tannins) mircetina and quercetin (flavonoids) and p-coumaric (phenolic acid), the first two being the most important in the role of reducing agent. Were identified by FTIR technique hydroxyl, carbonyl, carboxyl, epoxy functional groups and aromatic carbon to GO. After green reducing, it was possible to verify the reduction of these functional groups in the obtained materials. The structural change to the GO to RGO was confirmed by XRD and Raman spectroscopy. It was identified that the obtained RGO by a mix of water, alcohol, and acetone showed similar results to RGO obtained by sodium borohydride. Thus, this work presented an alternative to the use of harmful compounds in the GO reduction process in RGO. Besides, the methodology suggested here generated an environmentally friendly route to RGO synthesis.