Enhanced catalytic activity of silver nanoparticles loaded into Fe₃O₄ nanoparticles towards reduction of 4-nitrophenol, degradation of organic dyes and oxidation of o-phenylenediamine

In this study, ultrasonication method was used to load silver nanoparticles (AgNPs) on the pre-synthesized magnetic nanoparticles (Fe₃O₄). A mixture of silver nitrate solution and pre-synthesized Fe₃O₄ was sonicated for designated period of time and resulted in silver nanoparticles doped Fe₃O₄. The formation of AgNPs was directly confirmed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Furthermore, surface-enhanced infrared absorption spectroscopy (SEIRA) was used to confirm the formation of AgNPs indirectly. The relatively enhanced IR spectrum for the probe molecule, p-nitrothiophenol (p-NTP) that has been incubated with silver doped magnetic nanoparticles (AgNPs/Fe₃O₄) rather than Fe₃O₄ alone ascertains the formation of AgNPs. The catalytic activites of the particles were investigated using 4-nitrophenol and o-phenylene diamine (OPD) as reductant and peroxidase substrates respectively. The results show that AgNPs/Fe₃O₄ exhibited enhanced catalytic activities than Fe₃O₄ alone. The rate constants of AgNPs/Fe3O4 showing effect of sonication time for preparation of the catalyst using 15 mM of AgNO₃ solution were investigated and a rate constant of 2.1 × 10⁻² s⁻¹ was achieved for 60 min sonication time. The potential of the substrate in detection of ascorbic acid was demonstrated via inhibiting the peroxidase-like activity in the presence of ascorbic acid.