Background: Reduced graphene oxide (rGO) is often prepared from graphene oxide (GO) by
using various reducing agents like hydrazine hydrate, dimethylhydrazine, sodium borohydride, hydroquinone
etc. In view of the toxicity of chemical reagents, recent trends are directed towards the use of naturederived
biomolecules as the reducing source. The present study describes a comparative evaluation of
different properties of reduced graphene oxides (rGOs), prepared by using chemical and biological reducing
sources, and investigated their catalytic functions in the reduction of nitrobenzene to aniline.
Methods: GO is prepared from graphite powder following modified Hummers oxidation and subsequent
exfoliation by sonication. In order to obtain rGO, four different plants leaf extracts viz. Adathoda
Vasika (Malabar nut), Azadirachta Indica (Neem), Camellia Sinensis (Tea), Moringa Oleifera (Drumstick),
and a fungi extract of Volvereilla Volvacea (Mushroom) are chosen primarily from the local sub-
Himalayan region, all are edible to human beings as well as have long been used as traditional medicines
to combat with various diseases. The plant leaves are washed carefully with distilled water, kept
in air oven at 80 oC for two days, and then the dry leaves are crushed to fine powder. The plant leafextracts
are obtained by stirring a suspension of each type of finely grinded leaf powder (500 mg in 80
mL of DI water) overnight at room temperature and filtering the extract to remove any dust plant
leaves. Each rGO is denoted as rGO-AV, rGO-AI, rGO-CS, rGO-MO and rGO-VV, based on the
abbreviation of sources. The rGO-HH stands for rGO obtained by using hydrazine hydrate.
Results: Each rGO was characterized by UV-Vis, FT-IR, Raman spectroscopic techniques, and surface
morphological aspects were studied by powder XRD, Scanning and Transmission electron microscopic
images (SEM and TEM). The acidic nature (pH) of each rGO in aqueous suspension as well as cationexchange
capacity was measured by potentiometric titration in the absence and presence of an electrolyte
respectively. Finally, the catalytic ability was evaluated in the reduction of nitrobenzene to aniline
at room temperature monitored by UV-Vis spectrophotometer. While textural aspects of various rGOs
are fairly similar, various physicochemical properties like pH, cation-exchange ability etc are found to
be different for rGOs obtained by using different phyto-extracts. Moreover, there is significant variation
observed in their catalytic activity in the reduction of nitrobenzene.
Conclusion: Present studies establish that the rGO can be efficiently prepared by various naturederived
aqueous extracts. Although the textural aspects of rGOs display marginal changes, their catalytic
activity in the reduction of nitrobenzene to aniline greatly differs, as studied by UV-Vis spectrophotometric
kinetic measurements. By comparison, it is found that rGOs obtained by using plant leaf
extract of Adathoda Vasika, (rGO-AV) and an edible mushroom extract of Volvereilla Volvacea, (rGOVV)
exhibit significantly better catalytic efficiency than others.