2 research outputs found
Chemoenzymatic Dynamic Kinetic Resolution Protocol with an Immobilized Oxovanadium as a Racemization Catalyst
An excellent compatible and cost-effective dynamic kinetic
resolution
(DKR) protocol has been developed by combining a novel immobilized
oxovanadium racemization catalyst onto cheap diatomite (V-D) with
an immobilized lipase LA resolution catalyst onto a macroporous resin
(LA-MR). V-D was prepared via grinding immobilization, which may become
a promising alternative for the immobilization of metals, especially
precious metals due to its low cost, high efficiency, easy separation,
and large reaction interface. The DKR afforded high yield (96.1%),
e.e. (98.67%), and Sel (98.28%) under optimal conditions established
using response surface methodology as follows: the amount of V-D 10.83
mg, reaction time 51.2 h, and temperature 48.1 °C, respectively,
indicating that all the reactions in the DKR were coordinated very
well. The DKR protocol was also found to have high stability up to
six reuses. V-D exhibited excellent compatibility with LA-MR because
the lipase immobilized onto MR did not physically contact with the
vanadium species immobilized onto diatomite, thus avoiding inactivation.
Considering that lipase, oxovanadium, diatomite, and MR used are relatively
inexpensive, and the adsorption or grinding immobilization is simple,
the LA-V-MD DKR by coupling LA-MR with V-D is a cost-effective and
promising protocol for chiral secondary alcohols
Eliminating Nanocrystal Surface Light Loss and Ion Migration to Achieve Bright Mixed-Halide Blue Perovskite LEDs
Blue light-emittin g diodes (LEDs) are important components
for
perovskite electroluminescence applications, which still suffer from
insufficient luminescence efficiency and poor stability. In Cl/Br
mixed perovskite NCs, surficial defects cause severe light failure
and ion migration, the in-depth mechanism of which is also not clear.
To gain insights into these issues, we employ the ligand post-addition
approach for mixed Cl/Br NCs by using octylammonium hydrobromide (OctBr)
ligands, which effectively decrease surficial light loss and block
ion migration pathways. The passivated CsPbCl1.5Br1.5 NCs exhibit exceptional blue emission with 95% PLQY, and
the electroluminescence spectra of LEDs are located at the initial
positions at the initial states. The treated NC blue devices show
a negligible color shift as the voltage increases, which proves that
electric-field-driven ion migration is drastically suppressed. In
addition, OctBr-treated CsPbCl1.5Br1.5 and CsPbClBr2 NC LEDs show high external quantum efficiencies of 2.42 and
3.05% for emission peaks at 456 and 480 nm, respectively. Our work
identified the nature of NC surface defects and provided a surficial
modification approach to develop high-performance and color-stable
blue mixed-halide perovskite LEDs