Characterization of CdSe nanocrystallite dispersions by small angle x-ray scattering

We use x-ray scattering at small angles (SAXS) to study interparticle interactions in dilute dispersions of CdSe nanocrystallite particles. In particular, we probe the dependence of these interactions on a few key parameters, including the nature of the cap molecules attached to the surface of the particles and the solvent. Alkyl capped nanocrystallites with relatively long hydrocarbon chains are stable in a range of solvents. Nanocrystallites capped with smaller molecules show attractive interparticle interactions. Existence of association (e.g., dimers and trimers) in dispersions characterized by attractive interactions is observed in the scattering data for pyridine capped particles.