Characterization of NPS.

A) Raman spectra of bare iron oxide NPS using an excitation laser at 632 nm. Magnetite and maghemite peaks are identified by full diamond and open triangle symbols, respectively. Raman intensity is measured in counts per second (cps). B) Dynamic light scattering measurements performed in water for bare iron oxide NPS (open circle, black line) and silanized NPS (open triangle, red line). The mean HD and the PDI are also shown. C) FTIR spectra of KBr pellets of bare iron oxide NPS (top, black line) and silanized iron oxide NPS (bottom, red line). D) Magnetic hysteresis curve of the iron oxide NPS measured at room temperature. Increased magnetic field scan is represented by red triangles pointing up and decreasing magnetic field scan by black triangles pointing down. The inset is a zoom of the figure showing near-zero magnetic coercivity.

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