kary

Porous sulfur‐modified Cd (P–Cd|S) architectures are synthesized, exhibiting superior activity for CO generation. The low CO selectivity of unmodified Cd indicates that the sulfur dopant enables a selectivity shift from HCOOH to CO. Mechanistic investigations reveal that the covalently hybridized sp band system with dual collaborative sites naturally breaks the linear correlation among intermediates binding and enables the convenient selectivity modulation.

Abstract

Electrochemical CO₂ reduction is regarded as a promising strategy for the sustainable conversion of greenhouse gas. However, it still remains a significant challenge to manipulate the selectivity and activity. Herein, amorphous and porous Cd modified by sulfur (P–Cd|S) is synthesized by a p‐block sulfur dopant. In comparison with unmodified Cd metal, the P–Cd|S architecture exhibits superior activity for selective CO generation, indicating that the sulfur dopant enables a selectivity shift from formic acid to CO. The high selectivity of P–Cd|S is partially ascribed to the local alkalization and suppression of hydrogen evolution as indicated by the finite element analysis. In‐depth mechanistic investigations by operando Raman, Infrared, and X‐ray photoelectron spectroscopy in combination with theory calculations indicate that the covalently hybridized sp band system with dual collaborative sites (Cd ^{δ +} and S ^{δ −}) gives rise to a strong interplay with CO₂ molecules and carbonaceous species, leading to the natural elimination of linear correlation among intermediates binding for d‐band metals and the convenient modulation of selectivity toward CO versus HCOOH.

A new image : A benzothiadiazole‐based covalent organic framework is reported to promote two‐photon induction and to overcome the aggregation‐caused emission quenching of the chromophores. The design improves upon current near‐infrared two‐photon induced fluorescence imaging techniques.

Abstract

Fluorescent materials exhibiting two‐photon induction (TPI) are used for nonlinear optics, bioimaging, and phototherapy. Polymerizations of molecular chromophores to form π‐conjugated structures were hindered by the lack of long‐range ordering in the structure and strong π–π stacking between the chromophores. Reported here is the rational design of a benzothiadiazole‐based covalent organic framework (COF) for promoting TPI and obtaining efficient two‐photon induced fluorescence emissions. Characterization and spectroscopic data revealed that the enhancement in TPI performance is attributed to the donor‐π‐acceptor‐π‐donor configuration and regular intervals of the chromophores, the large π‐conjugation domain, and the long‐range order of COF crystals. The crystalline structure of TPI‐COF attenuates the π–π stacking interactions between the layers, and overcomes aggregation‐caused emission quenching of the chromophores for improving near‐infrared two‐photon induced fluorescence imaging.

Sulfone-containing covalent organic frameworks for photocatalytic hydrogen evolution from water

Sulfone-containing covalent organic frameworks for photocatalytic hydrogen evolution from water, Published online: 01 October 2018; doi:10.1038/s41557-018-0141-5

POC Zika detection: A valve‐enabled lysis, paper‐based RNA enrichment, and RNA amplification device (VLEAD) is designed for sample‐to‐answer Zika virus detection. RNA is enriched with VLEAD in 25 min. A colorimetric signal is generated with SYBR Green dye and a blue LED flashlight after 25 min of reverse transcription loop‐mediated amplification (RT‐LAMP).

Abstract

The recent outbreaks of Zika virus (ZIKV) infection represent a public health challenge. Rapid, cost‐effective, and reliable diagnostic tools for ZIKV detection at the point of care (POC) are highly desirable, especially for resource‐limited nations. To address the need, we have developed an integrated device to achieve sample‐to‐answer ZIKV detection. The device features innovative ball‐based valves enabling the storage and sequential delivery of reagents for virus lysis and a paper‐based unit for RNA enrichment and purification. The paper unit is placed in a commercially available coffee mug that provides a constant temperature for reverse transcription loop‐mediated isothermal amplification (RT‐LAMP), followed by colorimetric detection by naked eye or a cellphone camera. Using the device, we demonstrated the reproducible detection of ZIKV in human urine and saliva samples.

PFS‐b‐PI (poly(ferrocenyldimethylsilane)‐block‐polyisoprene) diblock copolymers self‐assemble into biomorphic structures with shapes that depend on the assembly conditions. Long fiber‐like micelles of uniform width are formed with a crystalline PFS core in decane. Injection of a THF polymer solution into THF/decane leads to micrometer‐scale barbed and branched structures with shapes that depend upon the final THF content.

Abstract

Branched and barbed structures are common in nature but rare in nanoscale or mesoscale objects formed by bottom‐up self‐assembly. Key characteristics of the morphology of natural objects, such as various types of insects and conifer branches, is that despite their similarities no two individual objects are exactly the same. Here we report the self‐assembly conditions for a series of poly(ferrocenyldimethylsilane)‐block‐polyisoprene (PFS‐b‐PI) diblock copolymers that generate structures with biomorphic shapes. All of these polymers yield long uniform fiber‐like micelles with a crystalline PFS core in decane. Injection of a concentrated THF solution of these polymers into THF/decane mixtures, however, leads to barbed and branched mesostructures, with shapes that depend upon the final THF content of the mixed solvent. Interestingly, evaporation of the THF from suspensions of the colloidal biomorphic structures led to elongated fiber‐like structures.

The ketenimine species generated in situ from sulfonyl azides and terminal alkynes were trapped by the chiral guanidine/Cu^I complex and followed by a [2+2] reaction, which afforded various spiro‐azetidinimine oxindoles in good yields and excellent stereoselectivities. Control experiments and X‐ray crystallography were used to probe into the interaction of the chiral guanidinium salt with the copper salt.

Abstract

We report the development of a chiral guanidine‐based copper(I) catalyst for the asymmetric azide‐alkyne cycloaddition/[2+2] cascade reaction. Optically active spiroazetidinimine oxindoles were constructed by trapping the ketenimine species under mild reaction conditions. High level of enantioinduction and excellent isolated yields were achieved in the three‐component reaction of various isatin‐derived ketimines, sulfonyl azides, and terminal alkynes. Control experiments and X‐ray crystallography were used to probe into the interaction of chiral guanidinium salt with copper salt.