NMR analysis of surfaces and interfaces in 2-nm CdSe

Solid-state NMR analysis on wurtzite 2-nm hexadecylamine-capped CdSe nanocrystals (CdSe-HDA) provides evidence of discrete nanoparticle reconstruction within the Se sublattice of the nanomaterial. The cadmium and selenium atoms are probed with (1)H-(113)Cd and (1)H-(77)Se cross-polarization magic angle spinning (MAS) experiments, which demonstrate five ordered selenium sites in the nanoparticle that can be assigned to contributions arising from different surface sites and a selenium site one layer down from the surface. Intriguingly, in these materials both HDA and thiophenol are observed to selectively bind to specific sites on the nanoparticle surface. 2D heteronuclear chemical shift correlation (HETCOR) experiments provide evidence for thiophenol selectively binding at surface vacancies. Analysis of the NMR provides a model of a 2-nm CdSe-HDA molecular surface.