Blue Luminescence and Superstructures from Magic Size Clusters of CdSe

Abstract

In this letter, we present a low-temperature synthesis route revealing a new type of ultrasmall CdSe nanoparticle family with exceptional narrow blue emissions between 437 and 456 nm and full width at half-maxima below 20 nm. Transmission electron microscopy characterization shows the uniformity of the nanoparticles, which have a diameter of 1.6 nm. After surface modification, the spherical particles assemble into nanowires, demonstrating their potential as building blocks for the generation of highly ordered superstructures. They can also be used as single source precursors for the synthesis of CdSe nanocrystals.

Fabrication and Optical Properties of Water Soluble CdSeS Nanocrystals Using Glycerin as Stabilizing Agent

“…Again the big resolved quantum confinement based on photoluminescence spectra is due to the larger particle size of cubic CdSe 0.2 S 0.8 nanocrystals instead of ultrasmall particle size for pure CdSe nanocrystals. This point differs significantly from the results being observed by Riehle et al [37], who assigned the strong quantum confine effect in PL spectra to ultra small particle size of pure CdSe nanocrystals, which were also fabricated using MPA as the surface activation agent. Actually the S ions inside MPA molecule may release additional S sources, which would combine with Se source to react with Cd precursor together, thus CdSeS instead of pure CdSe nanocrystals could be formed.…”

“…This result is in good agreement with the formula of CdSe 0.2 S 0.8 compound being drawn from XRD pattern. Similar results have been reported by Kasuya et al [43], Chen [44] and Riehle et al [37] who studied the transformation of magic size CdSe clusters into CdSe NCs by UV-vis absorption spectroscopy and photoluminescence spectra. Again the big resolved quantum confinement based on photoluminescence spectra is due to the larger particle size of cubic CdSe 0.2 S 0.8 nanocrystals instead of ultrasmall particle size for pure CdSe nanocrystals.…”

A New Class of Nanostructured Inorganic–Organic Hybrid Semiconductors Based on II–VI Binary Compounds

“…Remarkably, the extent of such band gap increase ($2 eV) is significantly higher than what has been achieved by the smallest colloidal QDs reported to date ($1 eV) (72,(117)(118)(119)(120). Compared with the colloidal II-VI quantum dots, the crystalline nanostructured hybrid semiconductors are free of several crucial issues [e.g., particle size distribution and morphology, postsynthetic purification, stoichiometric lattice (problems with lattices altered by the defects, e.g., excess atoms, alloying additions, or vacancies), local oxygen concentrations, as well as the dispersity of particles].…”

“…As shown in Table VIII, the thickness of the II-VI single layers in hybrid structures is typically $4-5 A , which is much smaller than the average dimensions of colloidal QDs. Thus, the extent of quantum confinement in hybrids (except for Mn based and double-layered structures) is evidently much stronger than that found in the smallest QDs reported to date (72,(117)(118)(119)(120)178). Theoretical calculations using density functional theory (DFT) with local density approximation (LDA) have been carried out on selected hybrid structures to confirm this observation (179,180).…”

Spontaneous Room Temperature Elongation of CdS and Ag2S Nanorods via Oriented Attachment

“…In general, the attaching nanoparticles must be ligand free on the joining facet, for attachment to occur and several reports demonstrate 2 oriented attachment only after selective removal of surfactant capping ligands. [29][30][31] Two distinct types of oriented attachment are reported, perfect and imperfect, depending on whether the area at which the nanocrystals fuse is apparent in the resulting nanorod. 22,32,33 The type of attachment is largely determined by the extent of Ostwald ripening which occurs in solution allowing the formation of a crystallographically smooth interface.…”