Green and Solvent-Free Supercritical CO₂‑Assisted Production of Superparamagnetic Graphene Oxide Aerogels: Application as a Superior Contrast Agent in MRI

Extraordinary properties are often described for 2D nanocomposites involving graphene flakes and a second component selected from particles or fibers. From this family of hybrid materials, this study is centered on composites based on graphene oxide (GO), a multifunctional oxygenated version of graphene, and superparamagnetic iron oxide nanoparticles (SPIONs), with applications as contrast agents in magnetic resonance imaging (MRI). The research focuses on the loading of SPIONs onto a GO surface via a simple one-pot supercritical CO₂ technique. The developed all-green synthesis approach allows the preparation of hybrid materials shaped into aerogels with large mesoporosity. The use of coated and uncoated components in the aerogel composites is analyzed with emphasis in the significance of the arrangement of the NPs into clusters on the GO surface and related with the magnetic properties. The development of composites involving organic coating has been widely studied to pursue the double objective of increasing NP/GO conjugation and improving the system biocompatibility. Extensive structural and functional characterization is carried out to understand the behavior of composites toward their performance as contrast agents in MRI.