We have studied manganese doping of zinc selenide core/zinc sulfide shell nanocrystals (NCs) where the impurity phosphor resides primarily in the shell. We have found that a simple two-step synthesis can be used to create these nontoxic materials that display efficient energy transfer from the core to the Mn doped shell. These core/shell NCs retain ample quantum efficiency (∼25%) when solubilized in water, which opens the possibility of using these materials as bioimaging agents. As recent work has shown that nanocrystals can be functionalized with organic dyes to operate as ratiometric chemical sensing agents, we have conjugated the doped NCs with an organic dye to showcase efficient Förster resonant energy transfer from the shell-doped phosphor to the surface-bound dye. This result indicates that doped NCs can be used to develop nontoxic ratiometric sensing/biological imaging agents.
Abstract The aggregation state and endosomal trapping of engineered nanocarriers once internalized into cells remain poorly characterized. Here, we visualized the membrane penetrating dynamics of semiconductor quantum dots (QDs) into the cytosol of T cells on a single-cell and single-nanoparticle basis. We water solubilized CdSe/CdZnS QDs with polymer encapsulants functionalized with a cell-penetrating peptide composed of an Asp-Ser-Ser (DSS) repeat sequence. T cells tolerated the 24-h incubation with QDs at concentrations of 5 nM or lower. Single-particle imaging demonstrated that the number of internalized nanoparticles was dependent upon the concentration of the probes for both control (peptide-free) and DSS-QDs. DSS-QDs were mostly distributed as monomers, whereas the control QDs were aggregated into clusters. Single-particle tracking using total internal reflection and highly inclined illumination showed that DSS-QDs were stationary near the activating surface and mobile within the cytosol of the T cell. A correlation exhibited between the mobility and aggregation state of individual QD clusters, with monomeric DSS-QDs showing the highest mobility. In addition, monomeric DSS-QDs displayed much faster diffusion than the endosomes. A small-molecule endosome marker confirmed the absence of colocalization between endosomes and DSS-QDs, indicating their endosomal escape. The ability to deliver and track individual QDs in the cytosol of live T cells creates inroads for the optimization of drug delivery and gene therapy through the use of nanoparticles.
Small molecular reagents that can efficiently functionalize water soluble CdSe/ZnS nanocrystals (NCs) are reported. These reagents do not cause quenching or precipitation of NCs as seen with commercially available activators. The results demonstrate that controlling the electrostatic character of the materials is critical in the design of functionalization schemes.
We have developed a strategy for the ratiometric detection of toxic Hg2+ ions using a semiconductor nanocrystal energy-transfer donor coupled to a mercury-sensitive "turn-on" dye acceptor. The results demonstrate a new paradigm of toxic metal sensing that resolves the difficulties with the use of semiconductor nanotechnology for this purpose.
Spherical whispering-gallery-mode lasers employing CdSe/ZnS semiconductor nanocrystals (see Figure, inset scale bar: 15 μm) are assembled on a substrate using a simple, robust spin-coating fabrication method. The flexibility to choose the size of the microsphere template and the emission wavelength allows for the observation of single-mode lasing. At higher excitation intensities, lasing from higher multiexcitonic states is also observed.
Durch und durch grün: Nanokristalle mit einem CdxZn1−xSe-Kern wurden synthetisiert und mit CdyZn1−yS überzogen, um Kern-Schale-Nanokristalle mit der idealen Emissionswellenlänge für Quantenpunkt-LEDs (QD-LEDs) zu erhalten. Diese (CdxZn1−xSe)CdyZn1−yS-Kern-Schale-Nanokristalle wurden zur Herstellung farbgesättigter grün emittierender QD-LEDs genutzt (siehe Bild), die sich für Display-Anwendungen eignen.
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