Facile green synthesis of novel hierarchical Ag doped MnO2 (Ag@MnO2) nanoparticle embedded rGO nanohybrid: Photophysical, catalytic and antibacterial activity

A facile green, convenient, environmentally benign strategy has been devised to synthesize Ag doped MnO2 binary nanohybrid (Ag@MnO2) and Ag@MnO2 incorporated reduced graphene oxide (rGO) hierarchical nano hybrid (rGO-Ag@MnO2) using an aqueous extract of lichen Acroscyphus sphaerophoroides. The phytochemicals present in the lichen extract have served as both reducing and stabilizing agent for rGO, Ag@MnO2 and rGOAg@MnO2 nanohyrid. The nanohybrids prepared have been characterized using different techniques. The UV-Visible absorption spectra indicated the formation of GO, rGO and hybrid nanoparticle. The FT-IR spectra attested the involvement of phytomolecules in rGO and hybrid nanoparticle. The XRD study confirmed the presence of beta polymorph of MnO2 (beta-MnO2) in the nanohybrid. Morphological features of GO, rGO and the as prepared nanohybrids have been investigated using TEM and FE-SEM which revealed a predominantly spherical morphology of Ag@MnO2 with size 4-24 nm uniformly distributed over rGO sheet in the rGO-Ag@MnO2 nanohybrid. The oxidation states of metals were confirmed from XPS study. Studies on catalytic and antibacterial activity of the nanohybrids revealed that rGO served as a good matrix for nanoparticle incorporation and its interface with metallic nanohybrid enhanced the catalytic and bactericidal performance. A putative mechanism suggesting the role of rGO and Ag@MnO2 in the ternary nanohybrid acting as nanocatalyst and antibacterial agent is advanced. The role of active reactive oxygen species (ROS) in photocatalytic degradation was determined to be in the order h(+)< circle OH < O-2(.-).

Automated summary

A facile green synthesis method was used to prepare Ag doped MnO2 binary nanohybrid and Ag doped MnO2 incorporated reduced graphene oxide (rGO) hierarchical nanohybrid, using an aqueous extract of lichen Acroscyphus sphaerophoroides. The nanohybrids showed excellent catalytic and antibacterial activities, and the presence of reactive oxygen species played a critical role in the photocatalytic degradation process.