Pressure compression of CdSe nanoparticles into luminescent nanowires

Oriented attachment (OA) of synthetic nanocrystals is emerging as an effective means of fabricating low-dimensional nanoscale materials. However, OA relies on energetically favorable nanocrystal facets to grow nanostructured materials. Consequently, nanostructures synthesized through OA are generally limited to a specific crystal facet in their final morphology. We report our discovery that high-pressure compression can induce consolidation of spherical CdSe nanocrystal arrays, leading to unexpected one-dimensional semiconductor nanowires that do not exhibit the typical crystal facet. In particular, in situ high-pressure synchrotron x-ray scattering, optical spectroscopy, and high-resolution transmission electron microscopy characterizations indicate that by manipulating the coupling between nanocrystals through external pressure, a reversible change in nanocrystal assemblies and properties can be achieved at modest pressure. When pressure is increased above a threshold, these nanocrystals begin to contact one another and consolidate, irreversibly forming one-dimensional luminescent nanowires. High-fidelity molecular dynamics (MD) methods were used to calculate surface energies ...

2016 AGTA Spectrum and Cutting Edge Award Winners Announced

The American Gem Trade Association announced the winners of its annual Spectrum and Cutting Edge awards on Oct. 26. This year marks the 32nd annual contest. Judging occurred on Oct. 24 and 25 in New York City, and adjudicators included Ronald W. Arends of Aires Jewelers; Stephen M. Avery of Stephen M. Avery; Deirdre Featherstone of Featherstone Design; Lauren Kulchinsky-Levison of Mayfair Rocks; and Aron Suna of Suna Bros. AGTA CEO Douglas K. Hucker told JCK that he was pleased to see a number of new names enter pieces into the competition. A new category sponsorship courtesy of the Silver Promotion Service also helped to spike silver entries. “We never used to get more than a dozen, but this year we had 40 silver entries,” Hucker explained, and at least 50 percent of those were combined with gold. Other competition trends included fewer rough-cut stones and increased combinations of colors thanks to industry’s close watch of fashion color news (think Pantone’s Color of the Year). “Designers are not haphazardly putting colors together,” he added. “They are creating complementary and analogous combinations and pieces of jewelry that reflect what’s coming off the racks in clothing...