Issue Date: January 16, 2012
All-Inorganic Nanocrystals Boost Infrared Emission
A simple, low-temperature method can be used to prepare thin films of highly luminescent, infrared-emitting nanocrystals in an IR-transparent solution-cast matrix (J. Am. Chem. Soc., DOI: 10.1021/ja2087689). The study, led by Maksym V. Kovalenko and Dmitri V. Talapin at the University of Chicago, may lead to methods for making low-cost waveguides and other devices that are central to telecommunications technology. Conventional methods for synthesizing nanocrystals call for capping the particles with long-chain organic molecules to control particle size, morphology, and stability. But molecular vibrations associated with those ligands tend to sap the particles’ excitation energies, which reduces their IR emission efficiency and stability. To sidestep those problems, the researchers devised a solution-phase method for making PbS/CdS core/shell nanocrystals in which oleate groups that are key to forming intermediate particles are replaced with AsS33– groups. The all-inorganic particles are then treated at 130 °C in a step that converts AsS33– to an IR-transparent As2S3 matrix. Thin films of the matrix-encapsulated particles exhibit stable IR luminescence in the telecommunications wavelength region, the group reports.
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