Biosynthesizing Gold Nanoparticles with Parkia biglobosa Leaf Extract for Antibacterial Efficacy In Vitro and Photocatalytic Degradation Activities of Rhodamine B Dye

The toxicity and cost involved in the synthesis of nanoparticles using physical and chemical methods have led to the emergence of biological techniques being employed by scientists. Hence the present study employed an eco-friendly method by using Parkia biglobosa leaves extract as a reducing and stabilizing agent of chloroauric gold (HAuCl4) to gold nanoparticle (AuNPs). Direct Analysis in Real-Time (DART-MS) was employed for phytochemical screening. However, the AuNPs were characterized by Ultraviolet-Visible spectroscopy (UV/Vis), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy, Fourier Transmission Infrared Spectroscopy, and X-ray diffraction spectroscopy, before the antibacterial and photocatalysis study. DART-MS showed more than 20 phytochemicals, including phenolic compounds. The FT-IR revealed the existence of flavonoids that we hypothesized are responsible for gold chloride reduction reactions. The optical properties of the gold nanoparticles by UV/Vis spectra registered plasmon surface resonance at a peak of 530 nm, whiles TEM revealed the AuNPs to be mono-dispersed and shapes were spherical and triangular with sizes ranging from 3.4 nm to 39.7 nm. XRD also recorded face-centered cubic AuNPs with 20.94 nm as the average crystallite size. The synthesized AuNPs were able to elucidate their anti-bacterial efficacy on Gram-positive bacteria Staphylococcus aureus, enterococcus faecalis and Gram-negative bacteria Escherichia coli, pseudomonas aeruginosa. The photocatalytic activities of AuNPs under UV/Vis irradiation exhibited a substantial degradation effect on rhodamine b (RhB) within 75 minutes. Due to their non-toxic nature, plant-mediated biosynthesized AuNPs, would be valuable in enhancing their biomedical applications and in wastewater treatment.