Environmentally Sustainable Fabrication of Ag@<i>g‑</i>C₃N₄ Nanostructures and Their Multifunctional Efficacy as Antibacterial Agents and Photocatalysts

Noble-metal silver (Ag) nanoparticles (NPs) anchored/decorated onto polymeric graphitic carbon nitride (<i>g</i>-C₃N₄) as nanostructures (NSs) were prepared using modest and environment-friendly synthesis method with a developed-single-strain biofilm as a reducing implement. The as-fabricated NSs were characterized using standard characterization techniques. The nanosized and uniform AgNPs were well deposited onto the sheet-like matrix of <i>g</i>-C₃N₄ and exhibited good antimicrobial activity and superior photodegradation of dyes methylene blue (MB) and rhodamine B (RhB) dyes under visible-light illumination. The Ag@<i>g</i>-C₃N₄ NSs exhibited active and effective bactericidal performance and a survival test in counter to <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, and <i>Pseudomonas aeruginosa.</i> The as-fabricated NSs also exhibited superior visible-light photodegradation of MB and RhB in much less time as compared to other reports. Ag@<i>g</i>-C₃N₄ NSs (3 mM) showed superior photocatalytic measurements under visible-light irradiation: ∼100% MB degradation and ∼89% of RhB degradation in 210 and 250 min, respectively. The obtained results indicate that the AgNPs were well deposited onto the <i>g</i>-C₃N₄ structure, which decreases the charge recombination rate of photogenerated electrons and holes and extends the performance of pure <i>g</i>-C₃N₄ under visible light. In conclusion, the as-fabricated Ag@<i>g</i>-C₃N₄ NSs are keen nanostructured materials that can be applied as antimicrobial materials and visible-light-induced photocatalysts

Cobalt-Doped Ceria/Reduced Graphene Oxide Nanocomposite as an Efficient Oxygen Reduction Reaction Catalyst and Supercapacitor Material

Design and development of highly active and durable oxygen reduction reaction (ORR) catalyst to replace Pt- and Pt-based materials are present challenges in fuel cell research including direct methanol fuel cells (DMFC). The methanol crossover and its subsequent oxidation at the cathode is another unwanted issue that reduces the efficiency of DMFC. Herein we report cobalt-doped ceria (Co-CeO₂) as a promising electrocatalyst with competent ORR kinetics mainly through a four-electron reduction pathway, and it surpasses Pt/C by a great margin in terms of stability and methanol tolerance. The Co-CeO₂ nanoparticles of diameter 4–7 nm were uniformly grown on reduced graphene oxide (rGO) by a facile single-step hydrothermal process. The as-synthesized Co-CeO₂ nanoparticles/rGO nanocomposites are further demonstrated as active energy storage materials in supercapacitors, underscoring the importance of the studied materials in renewable energy industries

Biogenic Synthesis, Photocatalytic, and Photoelectrochemical Performance of Ag–ZnO Nanocomposite

The development of coupled photoactive materials (metal/semiconductor) has resulted in significant advancements in heterogeneous visible light photocatalysis. This work reports the novel biogenic synthesis of visible light active <i>Ag</i>–ZnO nanocomposite for photocatalysis and photoelectrode using an electrochemically active biofilm (EAB). The results showed that the EAB functioned as a biogenic reducing tool for the reduction of Ag⁺, thereby eliminating the need for conventional reducing agents. The as-prepared <i>Ag</i>–ZnO nanocomposite was characterized by X-ray diffraction, transmission electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic experiments showed that the <i>Ag</i>–ZnO nanocomposite possessed excellent visible light photocatalytic activity for the degradation of methyl orange, methylene blue, and 4-nitrophenol. Electrochemical impedance spectroscopy and linear scan voltammetry under dark and visible light irradiation confirmed the enhanced visible light activity of the <i>Ag</i>–ZnO as photocatalyst and photoelectrode. These results suggest that Ag nanoparticles induced visible light photocatalytic degradation and enhanced the visible light activity of the photoelectrodes by minimizing the recombination of photogenerated electrons and holes, thereby extending the response of pure ZnO to visible light

Biogenic Fabrication of Au@CeO₂ Nanocomposite with Enhanced Visible Light Activity

This study reports a biogenic approach to the synthesis of Au@CeO₂ nanocomposite using electrochemically active biofilms (EABs) in water under normal pressure and 30 °C. This work presents the results of extensive morphological, structural, optical, visible light photoelectrochemical and photocatalytic studies of Au@CeO₂ nanocomposite. The presence of a large number of interfaces between Au nanoparticles and CeO₂ for charge transfer is believed to play a key role in enhancing the optical and visible light photoelectrochemical and photocatalytic performance of Au@CeO₂ nanocomposite. The enhanced visible light degradation of methyl orange and methylene blue by Au@CeO₂ nanocomposite was much higher than that by pure CeO₂. The reusability, stability, and other results suggests that the Au@CeO₂ nanocomposite could be exploited as potential candidates for visible light photocatalysis, photovoltaic, and photoelectrochemical devices