Abstract
In the past decade, polymer based nanochannel structures have been deeply and extensively explored due to their fast and strong sensitivity in testing ability. Recently, polymers have ...attracted much attention as the substrate materials of nano channels due to their excellent biocompatibility, low material cost and ease of manufacture. The development of nanochannels capable of detecting ions, small biomolecules and biomacromolecules meet the conditions of combination of multiple surface modification strategies and reliable nano manufacturing technologies. In this paper, the research progress of polymer based nanochannels is reviewed. The topic covered in this work includes the structure, manufacturing technology and functional strategy of nano channels. This review emphasizes various of promising research directions, and discusses the mechanism and principle of different applications such as biosensors and drug delivery. The shortcomings and limitations of some polymer based nano channels in the development and application are also discussed. Finally, views on the future prospects of this research field are presented.
A facile and efficient method is presented for the synthesis of 6‐alkylated phenanthridine, possessing hindered quaternary carbon centers, by Zn‐mediated reductive trapping of tertiary alkyl radicals ...with both electron‐rich and electron‐deficient aryl isocyanides using nickel as a promoter. Bench‐stable and operation‐friendly tertiary alkyl oxalates derived from abundant tertiary alkyl alcohols were first used as radical precursors for the alkylation of isocyanobiphenyl species. This reaction displays excellent functional group tolerance and broad substrate scope, allowing access to desired products in good to excellent yields.
The efficient radical cascade cyclization protocol for the reductive cleavage of C−O bonds followed by phenanthridine formation is reported. The method involves generating tertiary alkyl radical intermediates that are invoked by single‐electron reduction by Zn, wherein MgCl2 serves as the indispensable additive and nickel as the promoter. The reaction displays excellent functional group tolerance and broad substrate scope.
Alkenes represent one of the most useful building blocks for organic synthesis, owing to their abundance and versatile reactivity. Transition metal (Pd, Cu, Co, Ni, Fe,
.) catalyzed ...difunctionalization of alkenes provides efficient access to substituted molecules from readily available alkenes by installing functional groups across their carbon-carbon double bonds. Particularly, Nickel-based catalytic complexes have attracted a great deal of attention. This is because they are prone to undergoing oxidative addition and slow β-hydride elimination, and can access both two-electron and radical pathways. Numerous elegant Ni-catalyzed cross-coupling methods,
, (hetero)arylboration, alkenylboration, alkylboration and alkynylboration of alkenes, have been developed with broad scopes and a high tolerance to a variety of functional groups. Therefore, the Ni-catalyzed carboboration of alkenes has become an efficient synthetic protocol to deliver substituted compounds by the cross-coupling of alkenes, electrophiles, and B
Pin
. Despite this progress, a number of challenging issues remaining in the field include broadening the types of carboboration reactions, especially the asymmetric ones, diversifying electrophile types (which is limited to halogens for now) and gaining profound insight into the reaction mechanisms. This review summarizes the recent progress in this emerging field from the literature published since 2018. It will provide the scientific community with convenience to access collective information and to accelerate their further research in order to broaden the scope of methodology and application in drug discovery programs.
Abstract
The fabrication of macroscopic objects from covalent organic frameworks (COFs) is challenging but of great significance to fully exploit their chemical functionality and porosity. Herein, ...COF/reduced graphene oxide (rGO) aerogels synthesized by a hydrothermal approach are presented. The COFs grow in situ along the surface of the 2D graphene sheets, which are stacked in a 3D fashion, forming an ultralight aerogel with a hierarchical porous structure after freeze-drying, which can be compressed and expanded several times without breaking. The COF/rGO aerogels show excellent absorption capacity (uptake of >200 g organic solvent/g aerogel), which can be used for removal of various organic liquids from water. Moreover, as active material of supercapacitor devices, the aerogel delivers a high capacitance of 269 F g
−1
at 0.5 A g
−1
and cycling stability over 5000 cycles.
Covalent organic frameworks (COFs) have emerged as an important class of organic semiconductors and photocatalysts for the hydrogen evolution reaction (HER)from water. To optimize their ...photocatalytic activity, typically the organic moieties constituting the frameworks are considered and the most suitable combinations of them are searched for. However, the effect of the covalent linkage between these moieties on the photocatalytic performance has rarely been studied. Herein, we demonstrate that donor‐acceptor (D‐A) type imine‐linked COFs can produce hydrogen with a rate as high as 20.7 mmol g−1 h−1 under visible light irradiation, upon protonation of their imine linkages. A significant red‐shift in light absorbance, largely improved charge separation efficiency, and an increase in hydrophilicity triggered by protonation of the Schiff‐base moieties in the imine‐linked COFs, are responsible for the improved photocatalytic performance.
Protonation of imine‐linked COFs yields significant variations of their (opto)electronic properties and results in a largely enhanced performance in photocatalytic hydrogen evolution from water. This is attributed to an enhanced light absorption ability, charge separation efficiency, and hydrophilicity of imine‐linked COFs upon protonation.
A novel nickel-catalyzed asymmetric 1,2-vinylboration reaction has been developed to afford benzylic alkenylboration products with high yields and excellent enantioselectivities by using a chiral ...bisoxazoline ligand. Under optimized conditions, a wide variety of chiral 2-boryl-1,1-arylvinylalkanes are efficiently prepared from readily available olefins and vinyl halides in the presence of bis(pinacolato)diboron as the boron source in a mild and easy-to-operate manner. This three-component cascade protocol furnishes exceptional chemo- and stereoselectivity, and its usefulness is illustrated by its application in asymmetric modifications of several structurally complex natural products and pharmaceuticals.
A novel nickel-catalyzed asymmetric 1,2-vinylboration reaction has been developed to afford benzylic alkenylboration products with high yields and excellent enantioselectivities by using a chiral bisoxazoline ligand.
Firms use aspirations to regulate innovative search activities, but peer and historical referents may contain different signals regarding performance feedback. Integrating insights from the ...literature on profit persistence with the behavioral theory of the firm, we propose a persistence-based framework of organizational innovative search that connects the persistence characteristics of feedback from peer and historical referents with innovative search. We first predict that feedback from peer referents is more persistent than feedback from historical referents. Further, we theorize that peer performance feedback produces more pronounced effects: Performance above (below) peer aspiration leads to less (more) innovative search compared with performance above (below) the historical aspiration level. In addition, because industries impose heterogeneous levels of profit persistence, the differential effect between peer and historical performance feedback on innovative search is likely to be more evident in highly persistent industries. Examining the research-and-development intensity of a comprehensive panel of Compustat manufacturing firms over the past 45 years, our results from quasi–maximum likelihood analysis and fixed-effect panel regression largely support our theoretical development. Our study extends a nascent understanding of aspiration heterogeneity by revealing and empirically confirming the critical role of persistence.
Herein, we present a facile and efficient allylation method
via
Ni-catalyzed cross-electrophile coupling of readily available allylic acetates with a variety of substituted alkenyl bromides using ...zinc as the terminal reductant. This Ni-catalyzed modular approach displays excellent functional group tolerance and a broad substrate scope, which the creation of a series of 1,4-dienes including several structurally complex natural products and pharmaceutical motifs. Moreover, the coupling strategy has the potential to realize enantiomeric control. The practicality of this transformation is demonstrated through the potent modification of the naturally antitumor active molecule β-elemene.
Herein, we present a facile and efficient allylation method
via
Ni-catalyzed cross-electrophile coupling of readily available allylic acetates with a variety of substituted alkenyl bromides using zinc as the terminal reductant.
Covalent organic frameworks (COFs) are promising materials for applications in photocatalysis, due to their conjugated, porous and chemically stable architectures. Alternating electron ...donor-acceptor-type structures are known to enhance charge carrier transport mobility and stability in polymers and are therefore also interesting building units for COFs used as photocatalysts but also as photoinitiator. In this work, two donor-acceptor COFs using electron deficient 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)trianiline and electron rich thiophene-based thieno3,2-
b
thiophene-2,5-dicarbaldehyde or 2,2′-bithiophene-5,5′-dicarbaldehyde linkers are presented. The resulting crystalline and porous COFs have been applied as photoinitiator for visible light induced free radical polymerization of methyl methacrylate (MMA) to poly-methyl methacrylate (PMMA). These results pave the way to the development of robust and heterogeneous systems for photochemistry that offers the transfer of radicals induced by visible light.
Crystalline and porous covalent organic frameworks (COFs) with donor-acceptor moieties in their backbone are utilized as initiators for visible light induced radical polymerization. The COFs are efficient photoinitiators, maintaining their structural integrity for several cycles.
Video stabilization techniques are essential for most hand-held captured videos due to high-frequency shakes. Several 2D-, 2.5D-, and 3D-based stabilization techniques have been presented previously, ...but to the best of our knowledge, no solutions based on deep neural networks had been proposed to date. The main reason for this omission is shortage in training data as well as the challenge of modeling the problem using neural networks. In this paper, we present a video stabilization technique using a convolutional neural network. Previous works usually propose an off-line algorithm that smoothes a holistic camera path based on feature matching. Instead, we focus on low-latency, real-time camera path smoothing that does not explicitly represent the camera path and does not use future frames. Our neural network model, called StabNet, learns a set of mesh-grid transformations progressively for each input frame from the previous set of stabilized camera frames and creates stable corresponding latent camera paths implicitly. To train the network, we collect a dataset of synchronized steady and unsteady video pairs via a specially designed hand-held hardware. Experimental results show that our proposed online method performs comparatively to the traditional off-line video stabilization methods without using future frames while running about 10 times faster. More importantly, our proposed StabNet is able to handle low-quality videos, such as night-scene videos, watermarked videos, blurry videos, and noisy videos, where the existing methods fail in feature extraction or matching.
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