A novel organometallic synthesis of highly luminescent CdTe nanocrystals

Highly luminescent CdTe nanocrystals were synthesized by reacting dimethylc admium with different tellurium sources in mixtures of dodecylamine and tri octylphosphine as the coordinating and size-regulating solvent. Colloids of crystalline CdTe nanoparticles with zinc blende lattice displaying mean pa rticle sizes between 2.5 and 7 nm were prepared at temperatures from 150 to 220 degreesC and were characterized by powder XRD, HRTEM, absorption, and luminescence spectroscopy. The particles show strong band-edge photolumines cence shifting from green to red with increasing particle size. The photolu minescence quantum yield was found to strongly depend on the tellurium sour ce employed in the synthesis. The highest quantum yields were observed by u sing a suspension of tellurium powder in a mixture of dodecylamine and trio ctylphosphine. These CdTe samples show a photoluminescence quantum yield up to 65% at room temperature without covering the surface of the nanoparticl es with a passivating inorganic shell. If a solution of tellurium in TOP ra ther than tellurium powder is used, higher reaction yields but nanoparticle s with lower quantum yields (about 35-50%) are the result. As-prepared coll oids show rather narrow particle size distributions, although all reactants were mixed at low temperature. The size distributions can be further impro ved by standard size selective precipitation.