Green synthesis of copper and silver nanoparticles and their antimicrobial activity

dc.contributor.authorNate, Zondi, Dr. Precious, Dr. Pierre Kalenga
dc.contributor.supervisorMoloto, Prof. Makwena Justice
dc.descriptionM. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technologyen_US
dc.description.abstractThe present study includes the use of a green synthetic method to prepare copper and silver nanoparticles using chitosan, aqueous extracts of Camellia sinensis, Combretum molle and Melia azedarach linn leaves. This study aims to investigate the influence of capping and precursor concentration on the properties of silver nanoparticles with emphasis on the medicinal plants chosen. The effect of capping agent on the properties of copper nanoparticles is also investigated. The phytochemical properties of plant extracts and the antimicrobial activity of the synthesized particles were also studied; this was achieved by using microdilution bioassay. Decoction method was used to extract secondary metabolites from plant leaves. Preliminary phytochemical screening carried out on the aqueous extracts of the plant leaves showed the presence of tannins, proteins, flavonoids, phenols, and carbohydrates. The total phenolic and flavonoids content of the aqueous extract was determined using spectroscopic methods. The highest phenolic content was found in the aqueous extract of Combretum molle (135 mg/g), and the highest flavonoid content was found in the aqueous extract of Camellia sinensis (0.4 mg/g). Characterization was done by a combination of spectroscopic, microscopy and XRD techniques. Both the size and shape of the synthesized silver nanoparticles were dependent on the identity of the capping molecule, precursor and capping agent concentration as depicted from their TEM and XRD results. Silver nanoparticles were found to be predominantly spherical. The capping agent concentration was also found to influence the degree of agglomeration, with an increase in capping agent concentration giving lesser agglomeration. FTIR spectral analysis showed that silver nanoparticles interact with bioactive compounds found in the plants through the hydroxyl functional group. Other shapes including diamond were observed for the effect of precursor concentration. The XRD micrographs revealed a face-centered cubic geometry and the phase remained the same with an increase in precursor concentration. The synthesized silver nanoparticles were all blue shifted compared to the bulk material. The TEM results revealed that copper nanoparticles with different sizes and shapes were successfully synthesized. All the prepared copper and silver nanoparticles showed satisfactory antifungal and antibacterial activity against Candida albicans, Cryptococcus neoformans, Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumonia and Pseudomonas aeruginosa. The capping molecules used in this study also showed some antibacterial and antifungal activity against the selected strains. However nanoparticles performed better than these capping molecules. Both silver and copper nanoparticles were found to be more active against gram-negative bacteria compared to gram-positive bacteria. Amongst all the prepared silver nanoparticles Combretum molle capped nanoparticles were found to be the most active nanoparticles. Also with copper nanoparticles, it was found that Combretum molle capped nanoparticles were the most active nanoparticles. Between the two metal nanoparticles, silver nanoparticles showed high antibacterial and antifungal activity compared to copper nanoparticles. The antioxidant activity of silver nanoparticles was assessed using 2.2-diphenyl-1-picrylhydrazyl. Silver nanoparticles were found to have some antioxidant activity. However, the capping molecules were found to be more active than the synthesized nanoparticles. This observation is attributed to the presence of some bioactive compounds in the plant extracts.en_US
dc.publisherVaal University of Technologyen_US
dc.subjectAqueous extractsen_US
dc.subjectMicrodilution bioassayen_US
dc.subjectCombretum molleen_US
dc.subjectCamellia sinensisen_US
dc.subjectGreen synthetic methoden_US
dc.subject.lcshDissertations, Academic -- South Africaen_US
dc.subject.lcshPlants -- Effect of trace elements onen_US
dc.subject.lcshCandida albicansen_US
dc.subject.lcshCryptococcus neoformansen_US
dc.subject.lcshStaphylococcus aureusen_US
dc.subject.lcshEnterococcus faecalisen_US
dc.subject.lcshPseudomonas aeruginosaen_US
dc.subject.lcshAntifungal agentsen_US
dc.subject.lcshAntibacterial agentsen_US
dc.subject.lcshBioactive compoundsen_US
dc.titleGreen synthesis of copper and silver nanoparticles and their antimicrobial activityen_US
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