High-Quality ZnS Shells for CdSe Nanoparticles:  Rapid Microwave Synthesis

Abstract

Using a domestic microwave oven and new, inexpensive precursors, a rapid and reliable synthesis of highly luminescent CdSe/ZnS NPs was developed. To evaluate the quality of our core/shell particles for varying shell thickness in comparison to that of CdSe/ZnS nanoparticles obtained commercially, the parameter fluorescence quantum yield is been used as well as a new, straightforward, thiophenol-based shell-quality test as a tool to ensure a dense ZnS shell without holes and cracks, which is a prerequisite for high luminescence and stability.

Silica‐Coated InP/ZnS Nanocrystals as Converter Material in White LEDs

“…We assumed that the resulting InP nanocrystals had zinc-precursor material bound to the surface, which could be then used in the one-pot shelling procedure. As previously reported, [12] Several two-component silicones were investigated for the composite synthesis, where component A contained silicone monomers and component B a platinum catalyst that induced polymerization. The nanocrystals were added in solution to component A, and the solvent was removed after homogenization (120 8C, 1 mbar, 100 Pa).…”

Nanocrystals and Nanoparticles Versus Molecular Fluorescent Labels as Reporters for Bioanalysis and the Life Sciences: A Critical Comparison

“…From the range of these nanocrystals, QDs are the ones most sensitive to photooxidation and photobleaching, but even these effects can be almost completely suppressed by epitaxical growth of a protective shell to shield the core material for relevant time intervals [80]. Moreover, the inorganic nature of the QDs makes them typically resistant to metabolic degradation in live cells and organism which is beneficial, e.g., for long-term imaging.…”

“…The size of this phenomenon, that often reveals a dependence on excitation wavelength and is typically most pronounced for UV excitation [136], is expected to depend on the quality of the initial QD surface passivation (i.e., the saturation of surface defects by ligands or a passivating shell), and also on shell quality, thereby principally reflecting the accessibility of the QD core. This can be thus exploited as a screening test for QD quality [80]. In addition, the luminescence quantum yield of QDs can be concentration-dependent [5], thereby yielding concentration-dependent signal fluctuations, that hamper quantification.…”

“…This involves the control of nanoparticle surface chemistry, and the establishment of functionalization protocols. A first useful step in this direction would be the design of a reliable and reproducible test for the quality of surface coatings, i.e., the degree of perfection of the surface ligand shell, as this is the most crucial parameter affecting the spectroscopic and toxicity properties of nanoparticles [80]. Eventually, the cytotoxicity of differently functionalized nanoparticles (including typical ligands) should be systematically assessed using previously standardized procedures.…”

Facile and green route to highly luminescent ZnS-shelled CdSe nanocrystals

“…Recently, layer-by-layer routes to passivate CdSe successively with CdS and ZnS were independently published by Xie et al [27] and Talapin et al [28]. More recently, Ziegler et al dedicated to establishing methods and tools for quality control of the passivating shell [29].…”