It is a well known fact that AgNPs and their composites show
greater catalytic activity in the area of dye reduction and removal.
Pal et al. studied the reduction of methylene blue by arsine in the
presence of silver nano [33], while Witcomb et al. studied the catalytic
activity of AgNPs on the reduction of phenosaffarin dye [34].
The present study aims at the reduction of methylene blue by the
natural green aqueous extract of myrobalan containing AgNPs. Pure
methylene blue has a max value of 664 nm. Thirty minutes after
the addition of the extract to the dye, the absorbance is gradually
decreased and is shifted to higher wavelength. The decrease
of absorbance is indicative of the ability of phyto extract to degrade
methylene blue. System containing dye, AgNPs and the extract at
the end of 30 min time interval showed a marked decrease in the
absorbance of methylene blue and increase of SPR peak of AgNPs
(Fig. 11). This reveals that AgNPs act as an electron transfer mediator
between the extract and methylene blue by acting as a redox
catalyst, which is often termed as electron relay effect [35] (Fig. 12).