The field of electrochemical synthesis has developed rapidly over the last decade and has provided alternative synthetic methods with the absence of stoichiometric amounts of chemical oxidants or ...reductants. Although sustainable electrosynthetic procedures have been developed, relatively few examples of highly enantioselective catalytic electrosynthesis have been reported to date. The development of general strategies for electrochemical enantiocontrol has thus proven to be a considerable challenge. This Minireview highlights the current knowledge and recent advances in the synthetic utility of electrochemical transformations for asymmetric synthesis. Specifically, three major types of catalytic enantioselective strategy in electrosynthesis are outlined, including electrochemical activation of chiral catalyst‐bound substrates, asymmetric cascade electrochemical processes, and chemically modified chiral electrodes.
The synthetic utility of electrochemical transformations in asymmetric synthesis is described in this Minireview. Three major types of catalytic enantioselective strategies in electrosynthesis, including electrochemical activation of chiral catalyst‐bound substrates, asymmetric cascade electrochemical processes, and chemically modified chiral electrodes, are discussed.
Lewis‐acid catalysis and electrochemistry represent two powerful fields that have found widespread application in organic chemistry. Reported herein is an asymmetric electrosynthesis in combination ...with a chiral Ni catalyst leading to an intermolecular alkylation reaction in good yields with excellent enantioselectivities (up to 97 % ee). Mechanistic studies suggest that the Lewis‐acid‐bound radical intermediate from a single‐electron anodic oxidation selectively reacts with the benzylic radical species to generate the desired adducts.
Electrifying: An efficient asymmetric electrosynthesis was developed with high yields and excellent enantioselectivities by using a chiral Ni catalyst. Mechanistic studies suggest that the Lewis‐acid‐bound radical intermediate, from a single‐electron anodic oxidation, selectively reacts with a benzylic radical species to generate the desired adducts.
An enantioselective bifunctional squaramide‐catalyzed detrifluoroacetylative alkylation reaction has been developed under electrochemical conditions. The unified strategy based on this key tandem ...methodology has been divergently explored for the asymmetric synthesis of fluorine‐containing target molecules with good stereocontrol (up to 95 % ee). Furthermore, this asymmetric catalytic reaction combines the benefits of electrosynthesis and organocatalysis for the preparation of biologically relevant products containing C‐F tertiary stereogenic centers.
An efficient asymmetric electrosynthesis was developed with high yields and excellent enantioselectivities. This efficient process is mediated by a bifunctional squaramide catalyst, and it provides an innovative approach to asymmetric synthesis of highly valuable products bearing a fluorine‐containing stereocenter with excellent enantioselectivity (up to 95 % ee).
Black phosphorus (BP) is a promising two-dimensional layered semiconductor material for next-generation electronics and optoelectronics, with a thickness-dependent tunable direct bandgap and high ...carrier mobility. Though great research advantages have been achieved on BP, lateral synthesis of high quality BP films still remains a great challenge. Here, we report the direct growth of large-scale crystalline BP films on insulating silicon substrates by a gas-phase growth strategy with an epitaxial nucleation design and a further lateral growth control. The optimized lateral size of the achieved BP films can reach up to millimeters, with the ability to modulate thickness from a few to hundreds of nanometers. The as-grown BP films exhibit excellent electrical properties, with a field-effect and Hall mobility of over 1200 cm
V
s
and 1400 cm
V
s
at room temperature, respectively, comparable to those exfoliated from BP bulk crystals. Our work opens the door for broad applications with BP in scalable electronic and optoelectronic devices.
Two Cenozoic prominent features are spatio-temporally associated in central Mongolia, i.e., the continental basalts and regional uplift, but their genesis and relationship remain unclear. This study ...presents major- and trace-element compositions for olivine phenocrysts and xenocrysts, as well as data of bulk-rock geochemistry and Sr-Nd-Hf isotopes for the host basalts. The studied basalts mostly have trachybasalt compositions with high total alkali (Na2O+K2O=5.1-8.2 wt%) contents and all display OIB-like trace element patterns (e.g., spikes of Ba, Nb, and Ta and troughs of Th and U) and EM1-like Sr-Nd-Hf isotopic compositions. Compared to the partial melting products of mantle peridotite, these basaltic samples have higher FeO/MnO, Zn/Mn, and Zn/Fe ratios. Meanwhile, phenocrystic olivines are characterized by lower Ca, Mn, Mn/Zn, and Mn/Fe but higher Ni than their counterparts in the peridotitic melts, indicating a pyroxenite-rich mantle source. The above geochemical data suggest that the source of the studied basalts was mainly made up of secondary pyroxenite produced by the reaction of recycled oceanic crust with its ambient mantle peridotite. The calculated magma oxygen fugacities (ΔFMQ-0.26 to +0.42) and mantle melting temperatures (1343-1430°C) do not support a genetic link with the stagnant Pacific slab or with a deep mantle plume. Instead, the far-field effect of India-Eurasia convergence possibly tapped the upper asthenospheric mantle, subsequent melting of which gave rise to the dispersive Cenozoic basalts. On the other hand, the xenocrystic olivines exhibit zoned textures with high-Fo (up to 92) cores and low-Fo (down to 76) rims, reflecting the melt-rock interaction. Preservation of zoned olivine xenocrysts indicates rapid magma ascent and widespread melt-rock reaction in the mantle lithosphere, which may modify the rheology and accelerate the mechanical erosion of mantle lithosphere. Consequently, mass deficit in the lithosphere could have caused isostatic uplift of central Mongolia in the Cenozoic.
Directional growth of ultralong nanowires (NWs) is significant for practical application of large-scale optoelectronic integration. Here, we demonstrate the controlled growth of in-plane directional ...perovskite CsPbBr3 NWs, induced by graphoepitaxial effect on annealed M-plane sapphire substrates. The wires have a diameter of several hundred nanometers, with lengths up to several millimeters. Microstructure characterization shows that CsPbBr3 NWs are high-quality single crystals, with smooth surfaces and well-defined cross section. The NWs have very strong band-edge photoluminescence (PL) with a long PL lifetime of ∼25 ns and can realize high-quality optical waveguides. Photodetectors constructed on these individual NWs exhibit excellent photoresponse with an ultrahigh responsivity of 4400 A/W and a very fast response speed of 252 μs. This work presents an important step toward scalable growth of high-quality perovskite NWs, which will provide promising opportunities in constructing integrated nanophotonic and optoelectronic systems.
The stereocontrolled allylic alkylation of carbonyl compounds with the goal of producing the full range of stereoisomers presents an effective approach for increasing the productivity of collective ...natural product synthesis and the creation of chiral molecule libraries for drug exploration. The simultaneous control of regio-, diastereo-, and enantioselectivity poses a significant synthetic challenge in contemporary organic synthesis. Herein, we describe a catalytic stereodivergent α-allylation protocol applicable to both aliphatic and aromatic 2-acylimidazoles, thereby providing a practical blueprint for the divergent synthesis of important chiral building blocks. Each of the six isomeric α-allylated compounds can be readily obtained with remarkable yields and exceptional stereoselectivities, by judiciously selecting the appropriate leaving group and permutations of enantiomers adapted from nickel and iridium catalysts. The versatility of this asymmetric allylic alkylation has been successfully utilized in the enantioselective synthesis of (R)-arundic acid and (S,S)-cinamomumolide, as well as in the stereodivergent total synthesis of tapentadol.
1D semiconductor core–shell wire heterostructures are crucial for high‐performance optical and optoelectronic device applications, but they are limited to the traditional semiconductor families. ...Here, the conformal epitaxy of CsPbBr3 shell on PbSe wire core is realized to form the core–shell PbSe@CsPbBr3 wire heterostructures via a chemical vapor deposition route. The Pb‐particle catalysts at the tips of the PbSe wires grown by vapor–liquid–solid provide the nucleation sites for the in situ rapid growth of CsPbBr3 cube crystals, which serve as the adatom collector for the following shell growth due to the faster adsorption of the evaporated source atoms on them than on the sidewalls of PbSe wires. This determines the directional growth of the shell along the PbSe wires from the tip to bottom. The spectral and transient photoluminescence reveals the efficient photogenerated carrier transfer from the shell to the core. Importantly, the photodetectors (PDs) based on the heterostructures show responsivity up to 4.7 × 104 A W−1 under 405 nm light illumination, and a wavelength‐dependent photocurrent polarity with the excitation of the light from near‐ to mid‐infrared (IR), which indicates potential applications in IR PDs and novel optoelectronic logical circuits.
The controllable growth of core–shell PbSe@CsPbBr3 wire heterostructures is demonstrated. The carrier transfer from the CsPbBr3 shell to the PbSe core is revealed by spectral and transient photoluminescence. Photodetectors based on this heterostructure show high performance under 405 nm light excitation and a wavelength‐dependent photocurrent polarity with the illumination of the light from near‐ to mid‐IR light.
Van der Waals (vdW) heterostructures are the fundamental blocks for two-dimensional (2D) electronic and optoelectronic devices. In this work, a high-quality 2D metal–semiconductor NiTe2/MoS2 ...heterostructure is prepared by a two-step chemical vapor deposition (CVD) growth. The back-gated field-effect transistors (FETs) and photodetectors based on the heterostructure show enhanced electronic and optoelectronic performance than that of a pristine MoS2 monolayer, owing to the better heterointerface in the former device. Especially, this photodetector based on the metal–semiconductor heterostructure shows 3 orders faster rise time and decay time than that of the pristine MoS2 under the same fabrication procedure. The enhancement of electronic behavior and optoelectronic response by the epitaxial growth of metallic vdW layered materials can provide a new method to improve the performance of optoelectronic devices.
Even though the nonlinear optical effects of solution processed organic–inorganic perovskite films have been studied, the nonlinear optical properties in two-dimensional (2D) perovskites, especially ...their applications for ultrafast photonics, are largely unexplored. In comparison to bulk perovskite films, 2D perovskite nanosheets with small thicknesses of a few unit cells are more suitable for investigating the intrinsic nonlinear optical properties because bulk recombination of photocarriers and the nonlinear scattering are relatively small. In this research, we systematically investigated the nonlinear optical properties of 2D perovskite nanosheets derived from a combined solution process and vapor phase conversion method. It was found that 2D perovskite nanosheets have stronger saturable absorption properties with large modulation depth and very low saturation intensity compared with those of bulk perovskite films. Using an all dry transfer method, we constructed a new type of saturable absorber device based on single piece 2D perovskite nanosheet. Stable soliton state mode-locking was achieved, and ultrafast picosecond pulses were generated at 1064 nm. This work is likely to pave the way for ultrafast photonic and optoelectronic applications based on 2D perovskites.
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