The effect of synthesis temperature on the size distribution of silver nanoparticles synthesized using Psidium guajava leaf extract and its antibacterial activity Lloyd Allan T. Cabanog, Rey Marc T. Cumba, Melania Enot, Joselito Labis, Aaron Andrew Mutia, Kurt Sterling Ubas, Marjune Bonilla, Archie Ruda, Rey Y. Capangpangan, Arnold C. Alguno
1Department of Physics, Mindanao State University - Iligan Institute of Technology, Iligan City, Philippines
2Caraga State University, Butuan, Philippines
3Natural Products Research and Development Center, Central Mindanao University, Maramag, Bukidnon, Philippines
4Department of Chemistry, Central Mindanao University, Maramag, Bukidnon, Philippines
5King Saud University, Kingdom of Saudi Arabia
6Mindanao State University - Naawan, Naawan, Misamis Oriental, Philippines
7Department of Physics, Central Mindanao University, Maramag, Bukidnon, Philippines
Abstract
Silver nanoparticles have been well known to possess efficient antibacterial properties. In this study, the biological route was utilized using Psidium guajava leaves extract mixed with silver nitrate to synthesize silver nanoparticles. In addition, synthesis was done at varying synthesis temperatures, namely 30, 50, 70, and 90 OC, to investigate its effect in size distribution and the antibacterial properties of the synthesized silver nanoparticles. Results revealed a blue-shift of surface plasmon resonance (SPR) peaks was observed. TEM results showed that particle distribution decreases as synthesis temperature increases, with mean sizes of 48.7, 40.8, 25.6, and 20.1 nm. The DLS hydrodynamic size distribution also revealed the same decreasing pattern with increasing synthesis temperature. The FTIR spectra also showed that the synthesized AgNPs was capped with phenolic compounds from the biomolecules in Psidium guajava leaves. The XRD analysis revealed that the obtained AgNPs had a crystallinity index of 79.3% with an average crystallite size of 10.98 nm. Finally, antibacterial tests via Disc Diffusion Test suggested that the AgNPs synthesized at higher temperatures are more effective bactericides than those synthesized at lower temperatures, as indicated by the measured zones of inhibition. Antibacterial activity was also observed to be more effective on the gram-negative bacteria E. coli than on the gram-positive S. aureus.
Keywords: synthesis temperature, psidium guajava, particle size distribution
