CdTe nanocrystal

Rockenberger J ef al 1998 The contribution of particle core and surface to strain, disorder and vibrations In thiolcapped CdTe nanocrystals J. Chem. Phys. 108 7807... 

CdTe nanocrystals of various sizes were synthesized according to the procedure in the report of Weller et al. [25] The sizes of the CdTe nanocrystals were estimated from... 

Rogach, A.L., Katsikas, L., Kornowski, A., Su, D., Eychmuller, A., and Weller, H. (1996) Synthesis and characterization of thiol-stabilized CdTe nanocrystals. Ber. Bunsenges. Phys. Chem. 100, 1772-1778. 

Rakovich, Y.P. Yang, L., McCabe, E.M., Donegan, J.F., Perova, T., Moore, A., Gaponik, N., and Rogach, A., 2003, Whispering gallery mode emission from a composite system of CdTe nanocrystals and a spherical microcavity, Sci. Technol. 18 914-918. 

Tsuruoka, T., Takahashi, R., Nakamura, T., Fuji, M., Akamatsu, K., Nawafune, H., Highly luminescent mono- and multilayers of immobilized CdTe nanocrystals controlling optical properties through post chemical surface modification. Chem. Commun. 2008, 1641-1643. 

The coupling chemistries that have been widely used in organic chemistry for producing chemical bonds have been applied to form irreversible and stable nanoparticle arrays on surfaces. Eychmriller et al. used the carbodiimide coupling chemistry to covalently assemble carboxylate-functionalized CdTe nanocrystals (NCs) onto amino-terminated glass surfaces, which resulted in densely covered nanoparticle films.14 The same principle was also applied to coat Si02 microparticles by CdTe NCs. 

CdSe and CdTe nanocrystals can be prepared without precursor injection.71 The method involves refluxing the cadmium precursor with Se or Te in octadecene. CdSe nanocrystals have also been synthesized using elemental selenium dispersed in octadecene... 

Tekin E, Smith PJ, Hoeppener S, van den Berg AMJ, Susha AS, Feldman J, Rogach AL, Schubert US. (2007) Inkjet printing of luminescent CdTe nanocrystal/polymer composites. Adv Fund Mater 17 23-28. 

Determination of surface atom density on nanocrystals can be difficult, and imprecise, especially for very small particles that cannot be easily characterized microscopically. Nevertheless, reasonable accuracy can be obtained by using theoretical calculations informed by empirical data. In this work, the CdTe nanocrystals that were prepared (2.5-6 nm diameter) were found to be in the zinc blende crystal structure, allowing the use of the bulk density and interplanar distances of zinc blende CdTe in these calculations. It is likely that a variety of crystalline facets are exposed on individual nanocrystals, each with a range of planar densities of atoms. It is also likely that there is a distribution of different facets exposed across an assembly of nanocrystals. Therefore, one may obtain an effective average number of surface atoms per nanocrystal by averaging the surface densities of commonly exposed facets in zinc blende nanocrystals over the calculated surface area of the nanocrystal. In this work we chose to use the commonly observed (Iff), (100), and (110) zinc blende planes, which are representative of the lattice structure, with both polar and nonpolar surfaces. For this calculation, we defined a surface atom as an atom (either Cd or Te ) located on a nanocrystal facet with one or more unpassivated orbitals. Some facets, such as Cd -terminated 111 faces, have closely underlying Te atoms that are less than 1 A beneath the surface plane. These atoms reside in the voids between Cd atoms, and thus are likely to be sterically accessible from the surface, but because they are completely passivated, they were not included in this definition. 

The CdTe nanocrystals were synthesized by using aqueous solution of cadmium perchlorate and electrochemically produced hydrogen telluride with mercaptopropionic acid (MPA) as a stabilizer. The pH of the synthesis solution was maintained at 12, the precursors molar ratio was Cd Te MPA 2 1 2.6. The size of NCs depends on the refluxing time of the reaction mixture and may be tuned from ca. 2 up to ca. 6 nm. 

Tang ZY et al (2006) Self-assembly of CdTe nanocrystals into free-floating sheets. Science 314(5797) 274-278... 

WHISPERING GALLERY MODE EMISSION FROM A CORE-SHELL SYSTEM OF CdTe NANOCRYSTALS ON A SPHERICAL MICROCAVITY... 

We have studied the optical properties of a novel microcavity - quantum dot system consisting of a melamine formaldehyde latex microsphere coated by a thin shell of CdTe nanocrystals. The coupling between the emission from nanocrystals and spherical cavity modes was realized. Periodic narrow peaks of the emission spectra corresponding to the whispering gallery modes were detected and a threshold behavior of the emission intensity on excitation power was observed. 

In conclusion, we have demonstrated the resonance modes in a system consisting of a spherical microcavity coated by a thin CdTe NCs shell. Our results show that lasing in MF/CdTe NCs system is possible even if the quality factor of the microcavity is not very high. Microspheres coated by CdTe nanocrystals may therefore be useful for a variety of photonic applications. 

We report on the efficient photoluminescence up-conversion in colloidally synthesized CdTe nanocrystals. We demonstrate that the efficiency of photon energy up-conversion and the magnitude of the spectral shift can be controlled by (i) the size of the nanocrystals (ii) the temperature dependence of the excited state absorption coefficient (iii) the excitation intensity. We suggest that intrinsic gap states are involved as intermediate states in the up-conversion rather than nonlinear two-photon absorption or Auger processes,... 

Anti-Stokes photoluminescence (ASPL) or photon energy up-conversion (UC), in semiconductor quantum dots has attracted much attention recently [1-5]. In general, the energy up-conversion is usually achieved by Auger process [5], a nonlinear mechanism such as two-photon absorption [5] or by thermal activation. [4,6]. In this work we report on the ASPL at room temperature and very low excitation intensity in colloidal CdTe nanocrystals (NCs). 

Thiol-capped CdTe nanocrystals used for encapsulation are stable against photobleaching and have narrow and symmetric emission peaks tunable with a particle size (2.0-6.0 nm) from green (510 nm) to the near IR (730 nm) with... 

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