Here we designed and synthesized CdSe/CdSe 1−x Te x core/crown nanoplatelets (NPLs) with controlled crown compositions by using the core-seeded-growth approach. We confirmed the uniform growth of the crown regions with well-defined shape and compositions by employing transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. By precisely tuning the composition of the CdSe 1−x Te x crown region from pure CdTe (x = 1.00) to almost pure CdSe doped with several Te atoms (x = 0.02), we achieved tunable excitonic properties without changing the thickness of the NPLs and demonstrated the evolution of type-II electronic structure. Upon increasing the Te concentration in the crown region, we obtained continuously tunable photoluminescence peaks within the range of ∼570 nm (for CdSe 1−x Te x crown with x = 0.02) and ∼660 nm (for CdSe 1−x Te x crown with x = 1.00). Furthermore, with the formation of the CdSe 1−x Te x crown region, we observed substantially improved photoluminescence quantum yields (up to ∼95%) owing to the suppression of nonradiative hole trap sites. Also, we found significantly increased fluorescence lifetimes from ∼49 up to ∼326 ns with increasing Te content in the crown, suggesting the transition from quasi-type-II to type-II electronic structure. With their tunable excitonic properties, this novel material presented here will find ubiquitous use in various efficient light-emitting and-harvesting applications.

Here, we designed and synthesized alloyed heterostructures of CdSe x S1–x nanoplatelets (NPLs) using CdS coating in the lateral and vertical directions for the achievement of highly tunable optical gain performance. By using homogeneously alloyed CdSe x S1–x core NPLs as a seed, we prepared CdSe x S1–x /CdS core/crown NPLs, where CdS crown region is extended only in the lateral direction. With the sidewall passivation around inner CdSe x S1–x cores, we achieved enhanced photoluminescence quantum yield (PL-QY) (reaching 60%), together with increased absorption cross-section and improved stability without changing the emission spectrum of CdSe x S1–x alloyed core NPLs. In addition, we further extended the spectral tunability of these solution-processed NPLs with the synthesis of CdSe x S1–x /CdS core/shell NPLs. Depending on the sulfur composition of the CdSe x S1–x core and thickness of the CdS shell, CdSe x S1–x /CdS core/shell NPLs possessed highly tunable emission characteristics within the spectral range of 560–650 nm. Finally, we studied the optical gain performances of different heterostructures of CdSe x S1–x alloyed NPLs offering great advantages, including reduced reabsorption and spectrally tunable optical gain range. Despite their decreased PL-QY and reduced absorption cross-section upon increasing the sulfur composition, CdSe x S1–x based NPLs exhibit highly tunable amplified spontaneous emission performance together with low gain thresholds down to ∼53 μJ/cm2.

We report early detection of E. coli and total coliform bacteria using an automated, colorimetric and fluorometric fiber optics-based device.

Membrane antigens are phenotypic signatures of cells used for distinguishing various subpopulations and therefore, are of great interest for diagnosis diseases and monitoring of patient in hematology and oncology. Existing...

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