Atomic pair distribution function (PDF) study of iron oxide nanoparticles in aqueous suspension

Size is the key regulating the crystalline structure of iron oxide nanoparticles. The effect of the crystal size on the microstructure of these nanoparticles was investigated in an aqueous dilute suspension by energy dispersive X-ray diffraction (EDXD) and in an aqueous concentrated suspension by X-ray powder diffraction (XRD), at 293 K. Nanoparticle structure was also investigated by HRTEM. Structural results were interpreted in terms of theoretical models built using structural parameters obtained by the Rietveld method on XRD. The ability of the pair distribution function (PDF) to measure medium-range correlation lengths and size in nanoscale crystalline materials was also investigated and discussed. The sensitivity of the PDF technique allowed modelling of sample polydispersity.