The mobility of the 110 nm-Fe2O3 particles in a viscous sucrose solution depends on the concentration of the nanoparticles. When the average particle–particle nearest neighbor distance <r> is less than 250 nm, the particle interaction slows down their mobility. When <r> is more than 170 nm, the small mobility of nanoparticles does not depend on their concentration. The critical distance is approximately equal to 2Rh = 260 nm, where Rh is the hydrodynamic radius, determined by the dynamic light scattering (DLS) method.
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