Ph Dependent Effect on Size and Shape of Biosynthesized Silver Nanoparticles from Terminalia Pennyana

ABSTRACT The synthesis of nanoparticles has evolved through various methods, with increasing focus on eco-friendly approaches. Among these, plant-mediated synthesis has emerged as a viable alternative, utilizing phytochemicals from plant extracts to reduce and stabilize metal ions, resulting in nanoparticles with unique properties and potential applications. Terminalia pennyana, a member of the Combretaceae family, is a significant plant rich in phytochemicals. These compounds serve as capping, reducing, and stabilizing agents in the synthesis of nanoparticles. This study investigated how pH influences the size and shape of silver nanoparticles biosynthesized using the stem bark of Terminalia pennyana, which was sourced from the Department of Plant Science and Biotechnology at the University of Nigeria, Nsukka, Enugu State. The stem bark extract was used to synthesize silver nanoparticles, with the pH of the solutions adjusted to acidic, basic, and unadjusted (serving as a control), resulting in pH ranges of approximately 3.08 for acidic, 8.12 for basic, and 4.97 for the unadjusted control solution. Characterization of silver nanoparticles (AgNPs) synthesized using Terminalia pennyana was conducted using standard methods such as UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR), while phytochemical analysis was performed using the Harborne method. The UV-Vis spectroscopy results showed absorption peaks at 434 nm for the acidic sample, 350 nm for the basic sample, and 306 nm for the control sample, with only the acidic sample falling within the typical wavelength range for AgNPs. XRD analysis indicated that the control AgNPs had a crystalline nature with a peak at the (400) plane and a crystalline size of 18.502 nm. SEM revealed that the AgNPs had irregular, granular, rough, angular, sharp edge, and amorphous shapes. The FTIR spectra of the AgNPs and Terminalia pennyana stem bark extracts showed peaks consistent with hydroxyl groups, amines, carboxylic acids, alkanes, alkynes, and alkenes, indicating the presence of various phytochemicals. EDX findings showed presence of carbon and oxygen, with no presence of silver. The qualitative and quantitative analysis of Terminalia pennyana stem bark extract revealed the presence of alkaloids, flavonoids, terpenoids, phenolics, tannins, saponins, and soluble carbohydrates in varying concentrations, specifically containing 22.17% alkaloids, 3.25% flavonoids, 0.55% terpenoids, 37.13% phenolics, 9.38% tannins, 54.82% saponins, and 19.30% soluble carbohydrates. This study demonstrates the successful biosynthesis of silver nanoparticles using Terminalia pennyana stem bark extract, emphasizing the significant influence of pH on the size, shape, and crystallinity of the synthesized nanoparticles. The results contribute to the expanding knowledge base on plant-mediated synthesis methods for producing nanoparticles, which have potential applications in medicine, catalysis, and other fields. Further investigation is necessary to fully explore Terminalia pennyana as a sustainable and eco-friendly source of phytochemicals for nanoparticle synthesis.