This proposal aims to further investigate the short range structure and morphology of FePt NPs, of average diameter ~ 2 nm, and their surrounding surfactant layer (oleic acid and hexadecyl-amine) through Nimrod. FePt NPs are a diverse class of magnetic NPs which exhibit attractive properties for potential applications, from high density data storage devices to biomedical applications. We intend to take further measurements of selected isotopic substitutions of NP colloidal solutions,with D/H-variants of the amine surfactant and solvent. We will define the structural properties through 2nd order difference measurements and Pair Distribution Functions analysis. These final measurements are necessary for the completion of the experiments described in round 1 in order to provide a complete depiction of the NP morphology and the NP-surfactant system.