In this work we present the preparation of highly luminescent anisotropic CdTe/CdSe colloidal heteronanocrystals. The reaction conditions used (low temperature, slow precursor addition, and surfactant composition) resulted in a tunable shape from prolate to branched CdTe/CdSe nanocrystals. Upon CdSe shell growth the heteronanocrystals show a gradual evolution from type-I to type-II optical behavior. These heteronanocrystals show a remarkably high photoluminescence quantum yield (up to 82%) and negligible thermally induced quenching up to temperatures as high as 373 K.

Hybrid materials of polymers and cadmium selenide nanocrystals (CdSe-NCs) were produced through a layer-by-layer deposition technique. Polymer series comprises sulfonic, phosphonic, and carboxylic acids; pyridine- and amine-based polymers; and some related bipolar amphiphiles, including a dithiol. Nonaqueous dispersions of amine- and oleate-capped CdSe-NCs with 3, 4, and 5 nm diameters were used. Polymers and CdSe-NCs are alternately deposited on indium-tin-oxide/glass surfaces. CdSe-NCs layers undergo a sharp and irreversible electroxidation process in acetonitrile corresponding to the passage of two electrons per CdSe unit. The multilayer build-up, monitored by UV−vis spectroscopy and cyclic voltammetry, shows an increase in the film absorbance and oxidation stripping charge proportional with the number of adsorbed CdSe layers and with the particle diameter. Layer formation rate by acids follows their acidity, with thiols being much slower than sulfonic, phosphonic, or carboxylic acids. The semiconductor properties of the multilayers were evidenced by photoluminescence (PL), photoelectrolchemical, and photoconduction analysis. Good PL was recorded in pyridine-, amine-, and carboxylate-based multilayers, PL quenching in sulfonate-, phosphonate-, and thiolate-based multilayers. PL quenching is accompanied by higher photoelectrochemical and photoconductivity responses.

Colloidal Mn-doped ZnSe nanowires with diameters of 1-3 nm and lengths up to 200 nm were prepared from Li(4)[Zn(10)Se(4)(SPh)(16)] clusters and manganese stearate. The nanowires exhibit optical properties that depend on size, shape, and doping level. The manganese photoluminescence is slightly polarized perpendicular to the long axis and reaches a quantum yield of 40% after passivating the crystals with a CdSe shell.

Highly luminescent cadmium telluride (CdTe) nanocrystals were synthesized using Li(2)[Cd(4)(SPh)(10)] as a reactive Cd cluster compound at relatively low temperature, making it a safe precursor for the large scale synthesis of CdTe nanocrystals. Transmission electron microscopy (TEM) showed that the shape of the CdTe nanocrystals changes from nanorods to branched structures with increasing reaction time. The nanocrystals show high luminescent quantum yields up to 37% for CdTe branched nanostructures, and as high as 52% for CdTe/CdS core-shell heterostructures. CdTe/CdS nanocrystals were used to make light-emitting diodes in combination with organic layers for electron and hole injection. The devices show a maximum luminance efficiency of 0.35 cd A(-1).