We report the synthesis of colloidal EuS, La 2 S 3 , and LaS 2 nanocrystals between 150 and 255 °C using rare-earth iodides in oleylamine. The sulfur source dictates phase selection between La 2 S 3 and LaS 2 , which are stabilized for the first time as colloidal nanocrystals. The indirect bandgap absorption of LaS 2 shifts from 635 nm for nanoellipsoids to 365 nm for square-based nanoplates. Er 3+ photoluminescence in La 2 S 3 :Er 3+ (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.
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