Rare-Earth Sulfide Nanocrystals from Wet Colloidal Synthesis: Tunable Compositions, Size-Dependent Light Absorption, and Sensitized Rare-Earth Luminescence.

We report the synthesis of colloidal EuS, La2S3, and LaS2 nanocrystals between 150 and 255 °C using rare-earth iodides in oleylamine. The sulfur source dictates phase selection between La2S3 and LaS2, which are stabilized for the first time as colloidal nanocrystals. The indirect bandgap absorption of LaS2 shifts from 635 nm for nanoellipsoids to 365 nm for square-based nanoplates. Er3+ photoluminescence in La2S3:Er3+ (10%) is sensitized by the semiconducting host in the 390-450 nm range. The synthetic route yields tunable compositions of rare-earth sulfide nanocrystals. Interaction of light with these novel semiconducting nanostructures hosting rare-earth emitters should be attractive for applications that require broadband sensitization of RE emitters.

Efficient photoluminescence of isotropic rare-earth oxychloride nanocrystals from a solvothermal route.

Eu3+-doped sub-10 nm LaOCl nanocrystals with 43% photoluminescence quantum yield were prepared by solvothermal synthesis from hydrated rare-earth chlorides. As-obtained nanocrystals are nearly spherical, monodisperse and stable as colloidal dispersions. These combined features should intensify the interest for nanocrystalline rare-earth oxyhalides and their optical properties.