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.

Development of synthetic strategies that allow the formation of controlled 3-dimensional architectures composed of discrete ensembles of nanoparticles is a challenging goal. We present a synthetic strategy that allows the preparation of a macroscopic 3-D metal−semiconductor assemblage composed of 6.0-nm Au and 6.0-nm CdSe nanoparticles cross-linked by a bifunctional organic spacer. Optical absorption and electron microscopy imaging, coupled to electron diffraction and energy-dispersive X-ray analysis, indicate a 1:6 Au−CdSe composite that appears to be uniform over a micrometer scale. The 1:6 structure is believed to be a close-packed structure which arises from a combination of soft-sphere packing forces due to van der Waals and steric forces, and thermodynamic forces due to an acid/base controlled selective interaction of the organic headgroup moieties with the nanoparticle surfaces.