Synthesis of Silver Nanoparticles by Plant-Mediated Green Method: Optical and Biological Properties

In this study, silver nanoparticles (Ag NPs) were successfully synthesized by plant-mediated green route. The leaf extracts of locally sourced Canna indica and Senna occidentalis acted as the reducing agents/capping agents instead of toxic chemicals leading to unprecedented bioreduction which promoted nucleation and particle growth within 2 minutes of reaction. Optical measurements were characterized by high intensities of absorption revealed by narrow absorption peaks indicating confinement of excitons, with surface Plasmon resonance (SPR) bands of silver nanoparticles at 340–380 nm (S. occidentalis-stabilized Ag NPs) and 400–430 nm (C. indica-stabilized Ag NPs). Morphological characterization with scanning electron microscope coupled with energy dispersed spectrometer (SEM-EDS) and transmission electron microscope (TEM) revealed quasi-spherical, cubic and truncated edge Ag NPs with mean sizes of 9.10 ± 1.12 nm and 9.4 ± 1.95 nm. Formation of crystalline Ag NPs was also supported by X-ray diffraction (XRD) pattern and selected area electron diffraction (SAED) showing peak broadening. FTIR analysis revealed some characteristic vibrational bands of O–H, C=O, C=N functional groups at 3306, 1647 and 1246 cm–1 respectively in the organically capped silver nanoparticles. The mechanism of reaction in both syntheses was considered to be diffusion controlled Ostwald ripening process. The antimicrobial activity of the synthesized nanoparticles was tested against clinically isolated Gram positive bacteria: Staphylococcus aureus , Streptococcus pyogenes and clinically isolated fungus-Candida albicans. Significant growth inhibitions were found using analysis of variance (ANOVA), SPSS statistical tool at P < 0.05. The highest activity of C. indica-synthesized Ag NPs was against C. albicans, while S. occidentalis-derived Ag nanoparticles were most active against S. aureus and S. pyogenes. Hence, the findings of this research suggest potential applications of the bionanoparticles as optical materials, electronically conductive adhesives (ECA), and as a candidate for therapeutic drugs because of their biogenic nature

Synthesis, Characterization and Photocatalytic activity of silver and zinc codoped TiO2 nanoparticle for photodegradation of methyl orange dye in aqueous solution

In this study, TiO2 nanocrystals, 1 mol% Ag doped and 1 mol% Ag and 0.6 mol% Zn codoped TiO2 powders were synthesized by sol-gel route. Their photocatalytic activities on methyl orange dye under visible irradiation were investigated. The powders were characterized by X-Ray Diffraction (XRD), UV–Visible spectroscopy (UV-Vis), Brunauer–Emmett–Teller (BET) and Fourier Transform Infrared Spectroscopy (FT-IR). The XRD results revealed presence of rutile phase with average crystallite size between 9 and 11 nm. The UV-Vis spectra showed red-shift towards longer wavelength with corresponding decrease in band gap from 2.9 to 2.5 eV. The BET surface areas of the nanoparticles ranged from 4.7 to 11.8 m2g-1 with average pore size between 18.9 and 56.6 nm. The Ag doped TiO2 has the largest surface area of 11.8 m2g-1, while Ag-Zn co-doped TiO2 was found to have the highest pore size and volume. The absorption bands at 750-500 cm-1 were attributed to -O-Ti-O- bond in the TiO2 lattice. The photocatalytic efficiency was highest at optimum pH 4.1 for Ag-Zn codoped TiO2. The results confirmed that Ag doped and Ag-Zn co-doped TiO2 were more effective than pure TiO2. The kinetic data were fitted into pseudo-first-order equation using Langmuir-Hinshelwood kinetic modelThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author