Nanoparticles synthesis is an evergreen research field of 21st century in which the connotation of the biomediated experimental process is highly imperative. Biomediated silver nanoparticles were synthesized with the aid of an eco-friendly biomaterial, namely, aqueous Azadirachta indica extract. The effect of pH and temperature on the formation of silver nanoparticles was analyzed. Formation of the silver nanoparticles was verified by surface plasmon spectra using a UV−vis spectrophotometer. Morphology and crystalline structure of the prepared silver nanoparticles were characterized by TEM and XRD techniques, respectively. Furthermore, the biomediated silver nanoparticles without any surface modification were used for the heavy metal ion sensors in aqueous media. The prepared silver nanoparticles were successful in detecting even the minimal amount of heavy metal copper(II) ion and exhibited excellent specific metal ion selectivity.

The conductive polypyrrole (PPy)/reduced graphene oxide (rGO) composites were synthesized through simple, environmentally benign, time and cost efficient, in situ polymerization and bioreduction techniques. The pyrrole monomer effectively adsorbed over the negatively charged GO sheets through electrostatic and π−π interactions was polymerized into polypyrrole in its adsorbed state. The obtained morphological images of the rGO/PPy composite ensured that the entire surface of the active carbon support was covered by PPy. The removal of oxygen functionalities from GO with the aid of Ocimum tenuiflorum extract was ascertained through FT-IR and UV−vis absorption spectroscopic studies. The rGO/PPy composite exhibited higher electrocatalytic oxidation current as evidenced from the cyclic voltammetric analysis. The number of actives sites and continuous carrier channels of the rGO/ PPy composite exhibited a maximum MFC power density of 1068 mW/m 2 , which is almost two-fold higher than that of bare PPy. The strong active carbon support prohibited the swelling and shrinkage of the conductive polymer PPy and provided the strong physico and electrochemical robustness of the rGO/PPy composite, which increased the MFC durability performances up to 300 h. These findings have not only provided fundamental knowledge on the preparation rGO-based composites through a green approach but also have found possible applications in large-scale green energy devices.

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Platinum (Pt) nanoparticles anchored over reduced graphene oxide (rGO) and rGO/conductive polyaniline (PANI) composites were synthesized and exploited as anode catalysts in microbial fuel cells (MFC). PANI bridges rGO and Pt nanoparticles through the electrostatic interaction/π–π stacking force/hydrogen bonding and Pt–N bond, respectively, and increased the intrinsic stability of rGO/PANI/Pt composite. The electrocatalytic performances of rGO/PANI/Pt exhibited the better oxidation current and lower internal resistance over the prepared rGO/PANI and rGO/Pt composites as evidenced from the cyclic voltammetric and electrochemical impedance techniques, respectively. By the combined efforts of active support, high electrical conductivity, and number of catalytic active sites, the prepared rGO/PANI/Pt nanocomposite exhibited a maximum MFC power density of 2059 mW/m2 with the concrete life durability. Thus, the proposed approach has paved new dimensions in not only the preparation of rGO-supported conductive polymer nanocomposites but also its applications as effective anode catalysts in MFCs.

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