Shape- and size-controlled superparamagnetic iron oxide nanoparticles using various reducing agents and their relaxometric properties by Xigo acorn area

Superparamagnetic iron oxide nanoparticles (SPIONs) were investigated owing to their potential relaxometric properties for magnetic resonance imaging (MRI) applications. For this purpose, shape- and size-controlled SPIONs were prepared using various reducing agents via a facile chemical coprecipitation method. The optimization of reaction parameters such as stirring rate, temperature, reaction time, and pH was carried out to study the particle’s growth, size, and shape of nanoparticles (NPs). Transmission electron microscopy (TEM) images reveal that the spherical (9.1 ± 1.5 nm)- and cubic (11.7 ± 1.8 nm)-shaped NPs were attained using NH₄OH and NaOH as reducing agents, respectively. X-ray diffraction (XRD) analysis of as-synthesized SPIONs shows the formation of magnetite (Fe₃O₄) phase having cubic inverse spinel structure. The various oxidation states of Fe were investigated via X-ray photoelectron spectroscopy (XPS) by analyzing Fe 2p spectra of SPIONs. The magnetic character and chemical stability of SPIONs were monitored in the synthetic seawater (SW) having salinity 36.03 g L⁻¹; which is the critical requirement for oil reservoir applications. Spin–spin (T₂) relaxation signals were attained using miniaturized Acorn Area analyzer to determine the relaxometric properties. The transverse relaxivities (r₂) for MNP–NH₄OH (41.0 mM⁻¹ s⁻¹) and MNP–NaOH (28.5 mM⁻¹ s⁻¹) were 2.11 and 1.47 times higher than MNP–KOH (19.4 mM⁻¹ s⁻¹), respectively. This study affirms that by controlling the reaction parameters, we can selectively design Fe₃O₄ NPs of desired size and shape, which give enhanced T₂-relaxation and excellent relaxivity properties in SW for potential MRI applications associated with oil reservoirs.