Research Publications (Applied Sciences)
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Item Biocatalytic and biological activities of cassia occidentalis mediated silver nanoparticles(College of Graduate Studies, Walailak University, 2022-01-01) Singh, Shashika; Mohanlall, VireshSilver nanoparticles (AgNPs) were synthesized using the leaf extracts from Cassia occidentalis. The reactions were marked by a distinct colour change and the formation of AgNPs was monitored by measuring the UV-Vis spectra. The morphology and crystalline phase of the metal nanoparticles were determined using Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray analysis (EDX) and Fourier-Transform-Infrared Spectroscopy (FTIR). The biocatalytic activity of the AgNPs against nitrifying compounds was determined using 4-nitrophenol and 4-nitroalanine. The biological screening involved analyzing the AgNPs effectiveness against gram-negative and gram-positive bacteria (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus cereus and Enterococcus faecalis). The AgNPs displayed minimal inhibition at low concentrations ranging from 25 to 50 μg/mL. The toxicity of the AgNPs was tested using the brine shrimp assay and was observed as non-toxic with a nearly zero mortality rate. The AgNPs exhibited an antioxidant potential of 70.90 % inhibition at 1000 µg/mL. C. occidentalis is noted as a potential bioresource for synthesizing AgNPs with applications as antibacterial, antioxidant and biocatalytic agents. HIGHLIGHTS The addition of Ag nanoparticles to C. occidentalis plant extracts resulted in the formation of AgNPs-C. occidentalis complexes The AgNPs-C. occidentalis complexes were characterized using Transmission Electron Microscopy, Scanning Electron Microscopy with EDX, UV-Vis spectrophotometry and IR spectroscopy These AgNPs-C. occidentalis complexes were very stable and showed antibacterial activity against a range of tested gram-positive and gram-negative bacteria at low doses, thus proving to be good antimicrobial agents The AgNPs-C. occidentalis complexes showed higher scavenging activity than leaf extracts of C. occidentalis. The AgNPs have increased catalytic ability for the reduction of 4-nitrophenol and 4-nitroalanine after a 30 min time interval GRAPHICAL ABSTRACTItem Biocatalytic and biological activities of Kigelia africana mediated silver monometallic and copper-silver bimetallic nanoparticles(NISCAIR, 2022-01-08) Biyela, Buyani; Mohanlall, VireshAqueous extract of Kigelia africana leaves have been utilized for the synthesis of silver (AgNPs) and copper-silver bimetallic nanoparticles (Ag-CuNPs) that were generally found to be spherical and oval in shape. The synthesized nanoparticles were characterized using UV-Vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), and transmission electron microscopy (TEM). The antimicrobial activities were evaluated against both gram-negative and gram-positive strains of bacteria. The UV-Vis and FTIR techniques revealed the formation of nanoparticles and the active components were adsorbed on the surface of the particles thereby stabilizing the nanoparticles. The SEM reveals uniform microspheres of AgNPs and anisotropic particles for Ag-CuNPs. TEM shows the size of synthesized particles. The nanoparticles inhibited the growth of both gram-negative and gram-positive bacteria. The bimetallic nanoparticles synthesized from aqueous extract of K. africana leaves showed greater inhibition against Escherichia coli as compared to the monometallic nanoparticles. The AgNPs was more effective for the reduction of 4-nitrophenol and 4-nitroaniline as compared to Ag-CuNPs. The results of this study confirmed that Kigelia africana leaf and fruit aqueous extract can successfully reduce metallic ions to synthesize metallic nanoparticles that have antimicrobial and biocatalytic properties.