Browsing by Subject "Spectrally tunable"

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    Alloyed heterostructures of CdSexS1-x nanoplatelets with highly tunable optical gain performance
    (American Chemical Society, 2017) Kelestemur Y.; Dede, D.; Gungor K.; Usanmaz, C. F.; Erdem, O.; Demir, Hilmi Volkan
    Here, we designed and synthesized alloyed heterostructures of CdSexS1-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 CdSexS1-x core NPLs as a seed, we prepared CdSexS1-x/CdS core/crown NPLs, where CdS crown region is extended only in the lateral direction. With the sidewall passivation around inner CdSexS1-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 CdSexS1-x alloyed core NPLs. In addition, we further extended the spectral tunability of these solution-processed NPLs with the synthesis of CdSexS1-x/CdS core/shell NPLs. Depending on the sulfur composition of the CdSexS1-x core and thickness of the CdS shell, CdSexS1-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 CdSexS1-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, CdSexS1-x based NPLs exhibit highly tunable amplified spontaneous emission performance together with low gain thresholds down to ∼53 μJ/cm2.
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    Colloidal nanocrystals embedded in macrocrystals: methods and applications
    (American Chemical Society, 2016) Adam, M.; Gaponik N.; Eychmüller A.; Erdem, T.; Soran-Erdem, Z.; Demir, Hilmi Volkan
    Colloidal semiconductor nanocrystals have gained substantial interest as spectrally tunable and bright fluorophores for color conversion and enrichment solids. However, they suffer from limitations in processing their solutions as well as efficiency degradation in solid films. As a remedy, embedding them into crystalline host matrixes has stepped forward for superior photostability, thermal stability, and chemical durability while simultaneously sustaining high quantum yields. Here, we review three basic methods for loading the macrocrystals with nanocrystals, namely relatively slow direct embedding, as well as accelerated methods of vacuum-assisted and liquid-liquid diffusion-assisted crystallization. We discuss photophysical properties of the resulting composites and present their application in light-emitting diodes as well as their utilization for plasmonics and excitonics. Finally, we present a future outlook for the science and technology of these materials.