Synthesis and Characterization of Highly Luminescent CdSe−Core CdS/Zn_0.5Cd_0.5S/ZnS Multishell Nanocrystals

Abstract

We report on the preparation and structural characterization of CdSe nanocrystals, which are covered by a multishell structure from CdS and ZnS. By using the newly developed successive ion layer adhesion and reaction (SILAR) technique, we could gradually change the shell composition from CdS to ZnS in the radial direction. Because of the stepwise adjustment of the lattice parameters in the radial direction, the resulting nanocrystals show a high crystallinity and are almost perfectly spherical, as was investigated by X-ray diffraction and electron microscopy. Also, due to the radial increase of the respective valence- and conduction-band offsets, the nanocrystals are well electronically passivated. This leads to a high fluorescence quantum yield of 70-85% for the amine terminated multishell particles in organic solvents and a quantum yield of up to 50% for mercapto propionic acid-covered particles in water. Finally, we present experimental results that substantiate the superior photochemical and colloidal stability of the multishell particles.

Improved Biocompatibility and Pharmacokinetics of Silica Nanoparticles by Means of a Lipid Coating: A Multimodality Investigation

“…53 The QDs were incorporated in the center of highly monodisperse silica particles with a mean size of 34.3 ( 4.6 nm. These silica particles were made hydrophobic by a condensation reaction of octadecanol (ODOH) on their surfaces.…”

Interfacial engineering of core/shell heterostructured nanocrystal quantum dots for light-emitting applications

“…The critical shell thickness and the slope for k nr_def over the shell thickness depend on the structural difference, such as the crystal structures and lattice parameters, between the core and the shell. For example, the QYs of CdSe/ZnS NQDs (lattice mismatch = 12%) [19,35] start to drop at a much thinner shell with a much faster rate than the QYs of CdSe/CdS NQDs (lattice mismatch = 3.9%) (Figure 1(d)) [27,28].…”

“…The use of NQDs in light-emitting applications requires not only high luminescence efficiency for such NQDs but also prolonged stability against electrical, optical, and/or chemical stresses [27]. For NQDs populated with single excitons (electron-hole pairs), the quantum yield (QY) of NQDs is given by…”

“…In the last two decades, the structures of NQDs evolved into sophisticated heterostructures, boosting their optical performances and photophysical stabilities [19][20][21][22][23][24][25][26][27]. As a result of the multilateral efforts, core/shell heterostructured NQDs displaying almost 100% efficiency upon the excitation of both optical [24] or electrical pumping have been successfully realized.…”

“…Specifically, the structural formulation at the core-shell interface affects the formation of misfit defects that are efficient non-radiative recombination centers [21][22][23][24]27,30]. In addition, the potential profiles across the interfaces influence the Auger recombination (AR) rates [28,29,31,32].…”