6 research outputs found
Supplementary document for Needle of longitudinally polarized light using the circular Airy beam - 6768983.pdf
The difference between inward and outward circular Airy beams, the modulation effect of positive and negative cone angles, the importance of the evanescent waves, the detailed derivation of the angular spectrum using the stationary phase method, an
l‑Proline-Grafted Mesoporous Silica with Alternating Hydrophobic and Hydrophilic Blocks to Promote Direct Asymmetric Aldol and Knoevenagel–Michael Cascade Reactions
Promotion of heterogeneous asymmetric
catalysis is of major interest
in the asymmetric catalysis field. In this work, a novel strategy
for the synthesis of l-proline-grafted mesoporous silica
with alternating hydrophobic and hydrophilic blocks to promote the
heterogeneous asymmetric catalysis was reported. The surface synergies
in the neat environment and the interface acceleration in aqueous
medium thereby fostered high catalytic activities and enantioselectivity
in the direct aldol reaction and the Knoevenagel–Michael cascade
reaction. The l-proline loading could be reduced to as low
as 0.63 mol %, giving 95% ee for <i>anti</i>-isomers and
81% ee for <i>syn</i>-isomers in the catalytic asymmetric
aldol reaction of nitrobenzaldehyde and cyclohexanone, which was hard
to accomplish on the homogeneous counterpart. In the direct asymmetric
aldol reaction of ethyl-2-oxoacetate and cyclohexanone, 82% yield
in 24 h and 90% ee were achieved. More exciting, the catalysts were
applied to more exigent reactions. As an example, in the Knoevenagel–Michael
cascade reaction, 85% yield in 10 h and up to 91% ee was achieved
Lattice-Confined Sn (IV/II) Stabilizing Raft-Like Pt Clusters: High Selectivity and Durability in Propane Dehydrogenation
Catalytic dehydrogenation
of propane (DHP) to propene is highly
endothermic, requiring a high reaction temperature. Under harsh conditions,
it has been a great challenge to maintain excellent propene selectivity
and suppress the irreversible deactivation caused by sintering of
metallic active centers. This work reports a highly selective and
durable Pt–Sn catalyst for DHP, in which metallic Pt centers
are dispersed homogeneously in small raft-like clusters on MgÂ(Sn)Â(Al)ÂO
and form strong interactions with the Sn<sup>IV/II</sup> sites confined
in MgÂ(Al)O lattices. A propene selectivity of >99% at 550 °C
with a conversion close to the equilibrium (specific rate of 0.96
s<sup>–1</sup> for propene formation) and a propene selectivity
of >98% (specific rate of 1.46 s<sup>–1</sup>) even under
600
°C have been produced by highly dispersed Pt sites in Pt/MgÂ(Sn)Â(Al)ÂO.
The Pt–Sn interactions and Sn<sup>IV/II</sup> confinement were
revealed to afford the catalyst with good durability. No visible sintering
of Pt clusters was observed in the long-term DHP reaction
Enhancing Photoelectrochemical Water Oxidation Efficiency of BiVO<sub>4</sub> Photoanodes by a Hybrid Structure of Layered Double Hydroxide and Graphene
Making solar fuels, e.g., hydrogen
from water splitting, is one
of the most critical pathways to developing a clean energy economy.
The overall water splitting includes two half-reactions, i.e., water
reduction and water oxidation, in which the latter is a speed-limiting
step because of its multiproton-coupled four-electron process. It
is highly desirable to improve the efficiency of the prevailing photoelectrochemical
(PEC) anodes. We constructed an integrated BiVO<sub>4</sub> photoanode
modified with a hybrid structure of CoAl-layered double hydroxides
(LDHs) and graphene (G), i.e., G@LDH@BiVO<sub>4</sub>. This triadic
photoanode exhibited a remarkably enhanced performance toward PEC
water oxidation, compared to LDH@BiVO<sub>4</sub> and pristine BiVO<sub>4</sub>. The photocurrent density of G@LDH@BiVO<sub>4</sub> achieved
2.13 mA·cm<sup>–2</sup> (at 1.23 V vs reversible hydrogen
electrode, RHE), 4 times higher than that of pristine BiVO<sub>4</sub>. The oxidation efficiency is as high as 80% even at a low bias (<0.8
V vs RHE). The incident photon-to-current conversion efficiency (IPCE)
of G@LDH@BiVO<sub>4</sub> reaches 52% at 400 nm, 2.5 times higher
than that of BiVO<sub>4</sub>. The photoconversion efficiency peaked
at 0.55% at a bias of 0.72 V, a 25-fold increase over that of BiVO<sub>4</sub>. The findings indicated that the improvement of charge separation
efficiency is mainly ascribed to graphene. The enhanced charge transfer
efficiency is a consequence of the synergy of graphene and an LDH,
where the LDH is capable of expediting water oxidation kinetics and
graphene promotes photogenerated charge transfer
LncRNA H19-elevated LIN28B promotes lung cancer progression through sequestering miR-196b
<p>LncRNA H19 is involved in the development of multiple cancers. Here, we firstly provide new evidence that H19 can induce LIN28B, a conserved RNA binding protein, to accelerate lung cancer growth through sponging miR-196b. Abundance in LIN28B was observed in clinical lung cancer samples. A positive link was observed between H19 and LIN28B in clinical lung cancer samples. In lung cancer cells, H19 was capable of increasing LIN28B expression. Mechanistically, miR-196b directly targeted LIN28B to inhibit LIN28B expression. H19 was capable of promoting LIN28B expression through sequestering miR-196b. Functionally, H19-increased LIN28B conferred the cell proliferation of lung cancer. Our finding indicates that H19 depresses miR-196b to elevate LIN28B, resulting in accelerating cell proliferation in lung cancer.</p
High-Density Dispersion of Atomic Pt (Ru, Rh, Pd, Ir) Induced by Meso-Stable Penta-Coordinated Fe<sup>III</sup> in the Topological Transformation of Layered Double Hydroxides
Atomically dispersed metal sites afford high activity
or selectivity
in many heterogeneous catalytic reactions. It is still an open challenge
to achieve a high-density dispersion of atomic metals. Herein, this
work demonstrates a facile strategy to boost the dispersion density
of atomic metals by the induction of meso-stable lattice distortion
sites in the topological transformation of layered double hydroxides
(LDHs). Meso-stable penta-coordinated FeIII, resulting
from the difference in the thermal stability between Mg–OH
and Fe–OH in a LDH lattice, is utilized from MgFe–LDHs
as anchoring sites for atomic Pt. The dispersion density of atomic
Pt reaches 2.0 Pt1/nm2. This strategy in the
topological transformation of LDHs has been successfully extended
to prepare high-density atomic Ru, Ir, Pd, and Rh. In both catalytic
oxidation of HCHO and hydrogenation of furfuryl alcohol, high-density
atomic Pt affords high turnover frequency (TOF) by the simultaneous
high-efficiency activation of multimolecules on adjacent atomic Pt
sites. In HCHO oxidation, high-density atomic Pt affords high mass
activity under a high concentration, high space velocity, and low
temperature. In furfuryl alcohol hydrogenation, high-density atomic
Pt affords high mass activity while retaining >99% selectivity
of
2-methylfuran