2 research outputs found
Magnetic Superbasic Proton Sponges Are Readily Removed and Permit Direct Product Isolation
Workup in organic synthesis can be
very time-consuming, particularly
when using reagents with both a solubility similar to that of the
desired products and a tendency not to crystallize. In this respect,
reactions involving organic bases would strongly benefit from a tremendously
simplified separation process. Therefore, we synthesized a derivative
of the superbasic proton sponge 1,8-bis(dimethylamino)naphthalene
(DMAN) and covalently linked it to the strongest currently available
nanomagnets based on carbon-coated cobalt metal nanoparticles. The
immobilized magnetic superbase reagent was tested in Knoevenagel-
and Claisen–Schmidt-type condensations and showed conversions
of up to 99%. High yields of up to 97% isolated product could be obtained
by simple recrystallization without using column chromatography. Recycling
the catalyst was simple and fast with an insignificant decrease in
catalytic activity
Ultrapure Green Light-Emitting Diodes Using Two-Dimensional Formamidinium Perovskites: Achieving Recommendation 2020 Color Coordinates
Pure
green light-emitting diodes (LEDs) are essential for realizing
an ultrawide color gamut in next-generation displays, as is defined
by the recommendation (Rec.) 2020 standard. However, because the human
eye is more sensitive to the green spectral region, it is not yet
possible to achieve an ultrapure green electroluminescence (EL) with
a sufficiently narrow bandwidth that covers >95% of the Rec. 2020
standard in the CIE 1931 color space. Here, we demonstrate efficient,
ultrapure green EL based on the colloidal two-dimensional (2D) formamidinium
lead bromide (FAPbBr<sub>3</sub>) hybrid perovskites. Through the
dielectric quantum well (DQW) engineering, the quantum-confined 2D
FAPbBr<sub>3</sub> perovskites exhibit a high exciton binding energy
of 162 meV, resulting in a high photoluminescence quantum yield (PLQY)
of ∼92% in the spin-coated films. Our optimized LED devices
show a maximum current efficiency (η<sub>CE</sub>) of 13.02
cd A<sup>–1</sup> and the CIE 1931 color coordinates of (0.168,
0.773). The color gamut covers 97% and 99% of the Rec. 2020 standard
in the CIE 1931 and the CIE 1976 color space, respectively, representing
the “greenest” LEDs ever reported. Moreover, the device
shows only a ∼10% roll-off in η<sub>CE</sub> (11.3 cd
A<sup>–1</sup>) at 1000 cd m<sup>–2</sup>. We further
demonstrate large-area (3 cm<sup>2</sup>) and ultraflexible (bending
radius of 2 mm) LEDs based on 2D perovskites