doi:10.1038/nindia.2015.134 Published online 7 October 2015
Using grape extract, researchers have converted graphene oxide into reduced graphene oxide, which can remove a harmful dye known as malachite green from solutions1. The reduced graphene oxide is potentially useful for treating environmental samples contaminated with the dye.
Most techniques for making graphene employ harmful chemicals such as hydrazine. To devise an ecofriendly way to make graphene, the researchers investigated the use of grape extract, as it had previously been shown to reduce gold and silver salts to their metallic forms. They added graphene oxide to grape extract and then added ammonia solution to the mixture. On adding ammonia solution, the colour of the solution changed from red to dark green, indicating the synthesis of reduced graphene oxide.
The researchers made three reduced graphene oxide samples by heating the mixture for 1, 3 and 6 hours and then filtering, washing and drying the samples. Using spectroscopic analysis, they explored the efficacies of the different reduced graphene oxide samples and a graphene oxide sample to remove malachite green from solutions through adsorption.
The absorbance decreased sharply in the first 5 minutes for the sample heated for 3 hours, indicating that the sample removed most of the dye from the solution in this time. For all three samples, most of the dye was removed in first 10 minutes. The reduced graphene oxide samples exhibited a higher dye-removing capacity than the graphene oxide samples.
As grapes are easily available, this method could be adopted for large-scale production of reduced graphene oxide, the researchers say.