Chemically prepared colloidal semiconductor quantum dots have long been proposed as scalable and color-tunable single emitters in quantum optics, but they have typically suffered from prohibitively incoherent emission. We now demonstrate that individual colloidal lead halide perovskite quantum dots (PQDs) display highly efficient single photon emission with optical coherence times as long as 80 ps, an appreciable fraction of their 210 ps radiative lifetimes. These measurements suggest that PQDs should be explored as building blocks in sources of indistinguishable single photons and entangled photon pairs.Our results present a starting point for the rational design of lead halide perovskite-based quantum emitters with fast emission, wide spectral-tunability, scalable production, and which benefit from the hybrid-integration with nano-photonic components that has been demonstrated for colloidal materials. Tisdale.
Next-generation optoelectronic applications
centered in the near-infrared
(NIR) and short-wave infrared (SWIR) wavelength regimes require high-quality
materials. Among these materials, colloidal InAs quantum dots (QDs)
stand out as an infrared-active candidate material for biological
imaging, lighting, and sensing applications. Despite significant development
of their optical properties, the synthesis of InAs QDs still routinely
relies on hazardous, commercially unavailable precursors. Herein,
we describe a straightforward single hot injection procedure revolving
around In(I)Cl as the key precursor. Acting as a simultaneous reducing
agent and In source, In(I)Cl smoothly reacts with a tris(amino)arsenic
precursor to yield colloidal InAs quantitatively and at gram scale.
Tuning the reaction temperature produces InAs cores with a first excitonic
absorption feature in the range of 700–1400 nm. A dynamic disproportionation
equilibrium between In(I), In metal, and In(III) opens up additional
flexibility in precursor selection. CdSe shell growth on the produced
cores enhances their optical properties, furnishing particles with
center emission wavelengths between 1000 and 1500 nm and narrow photoluminescence
full-width at half-maximum (FWHM) of about 120 meV throughout. The
simplicity, scalability, and tunability of the disclosed precursor
platform are anticipated to inspire further research on In-based colloidal
QDs.
The multistep and continuous production of core-shell III-V semiconductor nanocrystals remains a technological challenge. We present a newly designed high-temperature and miniature continuous stirred-tank reactor cascade, for the continuous and...
Herein, the first total synthesis and stereochemical assignment of (+)-broussonetine H are reported. The ambiguous stereocenters within different fragments were independently installed through asymmetric methods, namely a diastereo- and enantioselective, iridium-catalyzed spiroketalization and Brown allylation. Finally, convergent merging of the fragments enabled the synthesis of all potential diastereomers, allowing stereochemical assignment of (+)-broussonetine H.
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