Fe-doped carbon dots as dual-mode <i>T</i> ₁ / <i>T</i> ₂ nano-contrast agents for ultra-high field MRI

@11.7 T = 3.23); notably, the magnetic properties remained almost unaltered for 8 days in water and cellular medium. Our results provide a combined and wide approach for synthesizing artifact-free Fe-doped CDs with potential in advanced UHF-MRI techniques.