Biosynthesis of Dy2O3 nanoparticles using Piper Retrofractum Vahl extract: Optical, structural, morphological, and photocatalytic properties

Phytoassisted synthesis of CuO and Ag-CuO nanocomposite, characterization, chemical sensing of ammonia, degradation of methylene blue

The elimination of hazardous industrial pollutants from aqueous solutions is an emerging area of scientific research and a worldwide problem. An efficient catalyst, Ag-CuO was synthesized for the degradation of methylene blue, the chemical sensing of ammonia. A simple novel synthetic method was reported in which new plant material Capparis decidua was used for the reduction and stabilization of the synthesized nanocatalyst. A Varying amount of Ag was doped into CuO to optimize the best catalyst that met the required objectives. Through this, the Ag-CuO nanocomposite was characterized by XRD, SEM, HR-TEM, EDX, and FTIR techniques. The mechanism of increased catalytic activity with Ag doping involves the formation of charge sink and suppression of drop back probability of charge from conduction to valance band. Herein, 2.7 mol % Ag-CuO exhibited better catalytic activities and it was used through subsequent catalytic experiments. The experimental conditions such as pH, catalyst dose, analyte initial concentration, and contact time were optimized. The as-synthesized nanocomposite demonstrates an excellent degradation efficacy of MB which is 97% at pH 9. More interestingly, the as-synthesized catalyst was successfully applied for the chemical sensing of ammonia even at very low concentrations. The lower limit of detection (LLOD) also called analytic sensitivity was calculated for ammonia sensing and found to be 1.37 ppm.

Facile biosynthesis of Ag-ZnO nanocomposites using Launaea cornuta leaf extract and their antimicrobial activity

The quest to synthesize safe, non-hazardous Ag-ZnO nanoomposites (NCs) with improved physical and chemical properties has necessitated green synthesis approaches. In this research, Launaea cornuta leaf extract was proposed for the green synthesis of Ag-ZnO NCs, wherein the leaf extract was used as a reducing and capping agent. The antibacterial activity of the prepared nanoomposites was investigated against Escherichia coli and Staphylococcus aureus through the disc diffusion method. The influence of the synthesis temperature, pH, and precursor concentration on the synthesis of the Ag-ZnO NCs and antimicrobial efficacy were investigated. The nanoparticles were characterized by ATR-FTIR, XRD, UV-Vis, FESEM, and TEM. The FTIR results indicated the presence of secondary metabolites in Launaea cornuta which assisted the green synthesis of the nanoparticles. The XRD results confirmed the successful synthesis of crystalline Ag-ZnO NCs with an average particle size of 21.51 nm. The SEM and TEM images indicated the synthesized nanoparticles to be spherical in shape. The optimum synthesis conditions for Ag-ZnO NCs were at 70 °C, pH of 7, and 8% silver. Antibacterial activity results show Ag-ZnO NCs to have higher microbial inhibition on E. coli than on S. aureus with the zones of inhibition of 21 ± 1.08 and 19.67 ± 0.47 mm, respectively. Therefore, the results suggest that Launaea cornuta leaf extract can be used for the synthesis of Ag-ZnO NCs.

Green synthesized Ag decorated CeO2 nanoparticles: Efficient photocatalysts and potential antibacterial agents

Implication of natural resources for manufacturing of nanoparticles is sustainable, economical and contaminant free approach towards ecological and medical applications. Herein, CeO₂ and Ag/CeO₂ nanoparticles are green synthesized from Morinda tinctoria plant extract. The phase structure, surface morphology, optical identity, Ce(III) and Ce(IV) valency of the synthesized CeO₂ and Ag/CeO₂ nanoparticles are explored. The X-ray diffraction analysis indicated the formation of cubic phase CeO₂ and cubic silver decorated CeO₂ nanoparticles. Fourier transform infrared (FTIR) spectroscopy revealed the metal decoration of CeO₂ nanoparticles, metal-oxygen stretching, indicating the plant molecules reduction and stabilization. UV-visible spectroscopy shown the decreased band gap owing to silver modification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs displayed spherical morphology of the nanoparticles. Elemental composition and sample purity is assessed by energy dispersive spectroscopy (EDS). Double oxidation of Ce, double splitting energy of Ag and lattice oxygen are observed from X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of Ag/CeO₂ exposed the enhanced photocatalytic activity up to 94% where CeO₂ nanoparticles gave 60% degradation of bromophenol blue (BB). The plasmonic decoration of silver on the ceria surface induced the charge separations and free radical reactions. Moreover, Ag/CeO₂ nanoparticles are seen as superior antibacterial agents than CeO₂ towards both E.coli and S.aureus. Hence, the silver decorated metal oxide photocatalyst successfully degraded the BB dye and inactivated the bacterial strains. This report established a future research in green synthesis of multipurpose metal nanoparticles.

In situ facile green synthesis of Ag-ZnO nanocomposites using Tetradenia riperia leaf extract and its antimicrobial efficacy on water disinfection

In this work, Ag–ZnO nanocomposites were prepared by a green synthesis route using aqueous leaf extract of Tetradenia riperia and investigated for antibacterial activity against Escherichia coli and Staphylococcus aureus. To optimize the synthesis of the Ag–ZnO, the effects of precursor concentrations, pH, and temperatures were studied. The Ag–ZnO nanocomposites were characterized by XRD, ATR-FTIR, FESEM, and TEM. Results show that the concentration of 8% Ag, the temperature of 80 °C, and a pH of 7–8 were optimal for the synthesis of Ag–ZnO nanocomposites. The XRD analysis showed the decrease in particle size of Ag–ZnO from 23.6 to 14.8 nm with an increase in Ag concentrations, which was further supported by FESEM analysis. TEM image of 8% Ag provides more information on the coexistence of Ag on ZnO where an average particle size of 14.8 nm was determined. The ATR-FTIR analysis confirmed the presence of phenolic compounds, which work as reducing and stabilizing agents. The antimicrobial activity results show that Ag–ZnO nanocomposite demonstrated a higher antimicrobial potency on E. coli than on S. aureus. Therefore, Tetradenia riperia leaf extract is a viable route for the synthesis of Ag–ZnO nanocomposites to be used for various applications, including water disinfection.