Jem 2100f field emission tem

Fe₃O₄ nanoparticles were synthesized using the polyol method previously described by Ammar et al. [19 ,20 (link)]. Briefly, 1,2-propanediol solution containing 8 mM iron (III) chloride, 24 mM sodium acetate, and 2 mL water was refluxed for 15 h. The nanoparticles were extracted from solution with a neodymium magnet, washed with water and dispersed for 24 h in a solution of 20 mM Al(NO₃)₃ and 100 mM KNO₃, adjusted to pH 7. The Al₂O₃ coated Fe₃O₄ nanoparticles were rinsed and briefly stored in PBMCA buffer (pH 7.4) until cell coating experiments were performed. Characterization of the particles was achieved with a JEOL JEM-2100F Field Emission TEM (JEOL USA, Inc., Peabody, MA) with scanning TEM and Oxford energy dispersive x-ray spectrometry capabilities, and a Zetasizer Nano ZS90 particle analyzer (Malvern Instruments Ltd, Worcestershire WR14 1XZ, UK). Analysis of the particle size showed an average diameter of 17 ± 6 nm. The surface charge was determined as a positive potential of 64 ± 3 mV. To further confirm the presence of the Al₂O₃ functional group, an elemental analysis was performed using an EDX measurement (Supporting Information Fig. 1).