Supercritical‐Fluid‐Assisted One‐Pot Synthesis of Biocompatible Core( γ ‐Fe 2 O 3 )/Shell(SiO 2 ) Nanoparticles as High Relaxivity T 2 ‐Contrast Agents for Magnetic Resonance Imaging

Monodisperse iron oxide/microporous silica core/shell composite nanoparticles, core( γ ‐Fe 2 O 3 )/shell(SiO 2 ), with a diameter of approximately 100 nm and a high magnetization are synthesized by combining sol–gel chemistry and supercritical fluid technology. This one‐step processing method, which is easily scalable, allows quick fabrication of materials with controlled properties and in high yield. The particles have a specific magnetic moment (per kg of iron) comparable to that of the bulk maghemite and show superparamagnetic behavior at room temperature. The nanocomposites are proven to be useful as T 2 MRI imaging agent. They also have potential to be used in NMR proximity sensing, theranostic drug delivery, and bioseparation.