Effect of Shell Thickness on the Optical Properties in CdSe/CdS/Zn_0.5Cd_0.5S/ZnS and CdSe/CdS/Zn_xCd_1–xS/ZnS Core/Multishell Nanocrystals

Abstract

The evolution of optical properties of two types of core/multishell nanocrystals (NCs)–type A (CdSe/CdS/Zn0.5Cd0.5S/ZnS) and type B (CdSe/CdS/Zn x Cd1–x S/ZnS)with an increase of shell thickness from 3.5 to 15.5 monolayers (MLs) has been studied. When the shell thickness was 9.5 MLs and more, the stability would be greatly improved and the quantum yields (QYs) almost did not change during the process of purification. Even after phase transfer experiment, the QYs of the water-soluble NCs were still kept 70–99% of their initial level. The as-prepared water-soluble NCs with 9.5 MLs and more also exhibited high stability in varying physiological conditions under PBS buffer and continuous UV radiation. For type B core/multishell NCs, due to a consecutive change of lattice parameters from core to shells, there were almost no defects induced between the CdSe core and ZnS shell. As a result, they had higher QYs and stability than type A core/multishell NCs at the same test condition.

Color tuning of indium phosphide quantum dots for cadmium‐free quantum dot light‐emitting devices with high efficiency and color saturation

“…The electron and hole wavefunctions can extend further into a ZnSe shell than into a ZnS shell, which increases the exciton radius and therefore results in a red shifted emission wavelength. Similar behavior can be observed for the CdSe/CdS system, where the hole is only poorly confined and the emission wavelength can be tuned via the shell thickness over a broad range …”

“…Similar behavior can be observed for the CdSe/CdS system, where the hole is only poorly confined and the emission wavelength can be tuned via the shell thickness over a broad range. 32 Concluding from this behavior, we introduce the ZnSe shell thickness as a tool to tune the emission wavelength of (a) (b) InP/ZnSe/ZnS QDs. Figure 3 shows the evolution of emission wavelength and PLQY when the ZnSe shell thickness on an InP core sample is increased by sequential Zn and Se precursor additions followed by heating to induce the shell synthesis.…”

Full‐visible spectrum emitting Zn–In–S:Cu/ZnS nanocrystals based on varying Cu concentrations and its application in white LEDs

“…It can be clearly noticed that PL intensity d‐NCs/silicone resin composite only declines by about 10% after it was continuously irradiated for 4 hours under ultraviolet light (Figure A), while a slight enhancement is observed for Zn–In–S:Cu/ZnS d‐NCs (Figure B). This slight enhancement should be ascribed to the NCs surface oxidation caused by UV irradiation, which is known for the NCs surface passivation . It simultaneously indicates an excellent photostability of as‐prepared core/shell d‐NCs.…”

“…This slight enhancement should be ascribed to the NCs surface oxidation caused by UV irradiation, which is known for the NCs surface passivation. 29,46 It simultaneously indicates an excellent photostability of as-prepared core/shell d-NCs. Increasing temperature, both PL intensities of d-NCs/silicone resin composite and d-NCs decrease slowly, and at 80°C, their emission intensities preserve above 78% of the initial ones ( Figure 6,D).…”

Synthesis of Reabsorption-Suppressed Type-II/Type-I ZnSe/CdS/ZnS Core/Shell Quantum Dots and Their Application for Immunosorbent Assay

“…These advantages open up opportunities for revolutionary advances in fluorescent labels for biomedical diagnostics, molecular imaging, and photoelectric field [1–7]. According to the band alignment between core and shell materials, the core/shell QDs can be classified as type-I, reverse type-I, and type-II structures.…”