Microwave-Assisted Synthesis, Characterization, and Application of Superparamagnetic S/Fe3O4 Nanocomposite: Case Studies of Ag Nanoparticles, Hg Metal and Its Effect on S. Aureus

Shiow, Yong Hong (2024) Microwave-Assisted Synthesis, Characterization, and Application of Superparamagnetic S/Fe3O4 Nanocomposite: Case Studies of Ag Nanoparticles, Hg Metal and Its Effect on S. Aureus. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

This thesis discusses the synthesis and characterization of S/Fe3O4 nanocomposite and its applications in the field of magnetically recoverable heavy metal capture and as a potential antibacterial agent. The first step was to synthesize superparamagnetic Fe3O4 nanoparticles (IONPs) using a green approach, where the chemical reduction of iron chloride (FeCl3) by sodium borohydride (NaBH4) in water at room temperature in the presence of FDA approved polyvinylpyrrolidone (PVP) surfactant was carried out. S/Fe3O4 nanocomposite was then synthesized by microwave-assisted melting of bulk sulfur in an aqueous dispersion of IONPs at 180 ℃ within 2 minutes. Solid bulk sulfur rapidly became a molten liquid which heterogeneously deposited on the surface of solid IONPs to afford S/Fe3O4 nanocomposite upon cooling to 25 ℃. The S/Fe3O4 nanocomposite was structurally characterized using a combination of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and powder x-ray diffractometry (PXRD), and was found to contain uniform spheroids with an average size of 68±10 nm. Its magnetic and optical properties were studied employing state-of-the-art vibrating sample magnetometer (VSM) and UV-Visible spectroscopy. The presence of PVP surfactant in S/Fe3O4 nanocomposite was confirmed by Fourier-Transformed Infra-red spectroscopy (FTIR) analysis. The synthesized S/Fe3O4 nanocomposite was tested for different applications: (1) heavy metals capture in aqueous system (where hydrophobic bulk sulfur has little or no application) and (2) as a potential antimicrobial agent. The S/Fe3O4 nanocomposite was found capable of capturing Ag NPs and Hg metal >3-4 times its own weight and the capture of Ag NPs was concluded to follow a pseudo-second-order adsorption model. The S/Fe3O4 nanocomposite demonstrated a resistance toward Gram-positive S. aureus at a minimum dose of circa 20,000 ppm, albeit no effect was observed on Gram-negative E. coli.