Gadolinium acetate

1-octadecene (ODE, tech. 90%) and oleic acid (tech. 90%) were purchased from Acros. Gadolinium (III) chloride hexahydrate (99.99%) and gadolinium acetate (99.9%) were purchased from Alfa Aesar. Sodium oleate, sodium citrate, iron chlorides and other reagents are purchased from Sinopharm Chemical Reagent Co. Ltd. All chemicals were used as received without further purification. TEM and HRTEM images were recorded on JEM-2100 microscope at an accelerating voltage of 200 kV. X-ray diffraction (XRD) patterns were recorded by Rigaku Ultima IV X-ray diffractometer with Cu Kα radiation. The X-ray photoelectron spectroscopy (XPS) measurements were carried out by a PHI Quantum-2000 photoelectron spectrometer. The hysteresis loops (at 300 K and 5 K) and temperature-dependent magnetization mesurements were recorded on Quantum Design MPMS-XL-7 system. The element analysis of metal ions was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The dynamic light scattering measurements were performed on Malvern Zetasizer nano ZS instrument. The MRI measurements and T₂/T₁ relaxation time testing were performed on 0.5 T NMI20-Analyst NMR Analyzing & Imaging system (Niumag Corporation, Shanghai, China), 3.0 T imaging system (Philips Medical System, ACHIEVA 3.0 T).