Green Synthesis of Silver Nanoparticles Using Coffee Waste Extract and Its Antibacterial Activity

Tan, Zhan Ber (2018) Green Synthesis of Silver Nanoparticles Using Coffee Waste Extract and Its Antibacterial Activity. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Green synthesis is a method that addresses reactions which are able to maximise desired products and minimise the usage of other chemicals as well as by-products. The aim of this study was to synthesise silver nanoparticles biologically using coffee waste extract and to evaluate the efficacy of its antibacterial activity against K. pneumoniae, P. aeruginosa, E. coli, S. aureus and S. epidermidis. The natural reduction process occurs when the hydro-ethanolic coffee extract was mixed with three different concentrations of silver nitrate, AgNO3 solution, 0.02M, 0.05M and 0.1M. The changes in colour from light brown to dark brown indicated that the process has taken place. The silver nanoparticles produced were characterised using instruments like Malvern Zetasizer analyser and Scanning Electron Microscope. The zetasizer analysis shows the size of nanoparticles within 32nm to 531nm when extract is mixed with 0.02M AgNO3, whereas the size of nanoparticles produced for subsequent concentration 0.05M and 0.1M are 19nm to 396nm and 59nm to 712nm, respectively. This demonstrates that the smallest nanoparticles produced were from the mixture of 0.05M AgNO3 and coffee waste extract. Hence, it was used in the subsequent evaluation of antibacterial activity. The result shows a clear zone of inhibition of growth on Gram-negative bacteria, Klebsiella pneumoniae as well as E. coli. This research shows that silver nanoparticles have the potential to be an effective antibacterial agent and further studies can be done to further substantiate the claims.