Latest ArticlesThe existence of adsorbed water and structural water in the crystal structure of attapulgite (ATP) endows it with poor capability to store lithium ions. Herein, the chloride molten salt method was developed to function ATP materials based on theoretical calculations, which exhibit ground-breaking electrochemical performance. After the modification process, the metal ions in chloride molten salt occupy the vertices of the Mg-O octahedral structure from the liberation of structural water and hydroxyl groups in ATP, forming MaMgbAlcSixOy (M = Li, Na, or K). Using LiCl molten salt-modified ATP (Li-ATP) as a proof-of-concept, the detailed phase transition, physicochemical properties, and lithium storage capacity were investigated. Compared to the original ATP, Li-ATP achieves a nearly 7-fold increase in lithium storage capacity (498 mAh/g), featuring a promising low-cost polyanionic type anode material.
It has been widely recognized that hole transporting materials (HTMs) play a key role in the rapid progress of perovskite solar cells (PVSCs). However, common organic HTMs such as spiro-OMeTAD not only suffer from high synthetic costs, but also usually require the additional chemical doping process to improve their hole transport ability, which unfortunately induces the terrible stability issue. Therefore, it is urgent to develop low-cost dopant-free HTMs for efficient and stable PVSCs. In this work, we have successfully developed a new class of efficient dopant-free fluoranthene-based HTMs (TPF1–5) with quite low lab synthetic costs by combining donor-acceptor and branched structure designs. The detailed structure-property study revealed that tuning the twisted arms at different substitution sites would regulate the intermolecular interactions and film-forming ability, thereby significantly affecting the performance of the HTMs. By applying these HTMs in conventional PVSCs, the dopant-free TPF1-based devices not only achieved the best efficiency of 21.76%, which is comparable to that of the doped spiro-OMeTAD control devices, but also showed much better operational stability, which maintained over 87% of the initial efficiency under maximum power point tracking after 1038 h.
Reliable and selective sensing of dopamine (DA) is essential for early diagnosis of mental diseases. Among the various potential methods, nanozyme-based sensing systems have demonstrated promising sensitivity and reliability. However, owing to the lack of substrate specificity, it is challenging to selectively detect DA using nanozymes. Herein, based on the reactivity of the DA oxidation intermediates, we report a cascade colorimetric sensing system for the selective detection of DA using only a single nanozyme. It was disclosed that the oxidation product of DA catalyzed by Co-N-doped carbon sheets (Co-N-C, a common oxidase-like nanozyme), dopamine quinone (DAQ), showed significant biocatalytic electron-donating activity in the reduction of O2 to generate O2•−. Further using O2•− to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), a colorimetric sensing platform for DA was constructed with a linear detection range of 50 nmol/L to 50 µmol/L and a low limit of detection of 4 nmol/L. Thanks to the reactivity of the oxidation product, without any biometric units (such as nucleic acids, enzymes, and antibodies/antigens), the reaction selectivity of DA against other interferences (e.g., ascorbic acid, adrenaline, 5-hydroxytryptamine, and glutathione) was enhanced up to 71-fold. Beyond complicated cascade systems requiring at least two nanozymes, sophisticated artificial recognition via multiple interactions was simplified by exploiting the oxidative properties of product intermediates; thus, only a single common oxidase-like nanozyme was needed. This work offers a new strategy to enhance the selectivity of nanozymes for bioanalytical applications.
GPCRs are dominant targets for approved drugs and the discovery of lead compound targeting them is still challengeable. Affinity-based screening technique is a promising platform to uncover GPCR ligands. However, the intrinsic activities of them are seldom simultaneously determined during the screening. Taking beta2-adrenoceptor (β2AR) as a probe, this work created a strategy for screening GPCR ligands with simultaneous characterization of their downstream G protein binding responses associated with GTP. The strategy included (ⅰ) the design and expression of a protein miniature formed by β2AR and G protein α-subunit (Gαs) using circularly permuted HaloTag (cpHalo) as a flexible linker; (ⅱ) immobilization of the miniature onto silica gel by a click dehalogenation reaction; (ⅲ) systematic characterization of the immobilized miniature by fluorescent and chromatographic studies, and (ⅳ) simulating of ligand-induced β2AR-Gαs signaling cascade by chromatographic assays using GTP as an indicator. The immobilized miniature exhibited specificity to β2AR and Gαs antibodies and ligands. The specificity is stable at least within fifteen days with the variation less than 1%. The intrinsic activities of β2AR ligands were distinguished by the changes of GTP chromatographic behaviors on Gαs-cpHalo-β2AR column. Agonists strengthened the binding affinity and kinetics of GTP with Gαs, while antagonist did not give any effect on them. With the intrinsic activity evaluation, we believe, it will improve the attributes of chromatographic methods for drug discovery efforts with minimizing false-positive results.
A novel and readily available binaphthyl-based fluorescent probe (S)-1 was designed and synthesized. (S)-1 can be used to not only chemoselectively discriminate 3 basic amino acids out of common amino acids, but also enantioselectively recognize histidine. Encouragingly, enantioselective imaging of histidine in cells was achieved for the first time by the probe (S)-1. These performances endowed it potential application in the chiral analysis of basic amino acids in asymmetric synthesis and cell imaging for diagnosis of diseases caused by racemization of histidine. Nuclear magnetic resonance (NMR) and mass spectrometry investigations suggested that different reaction extent of (S)-1 with l/d-histidine and different product structures generated the observed enantioselective fluorescent response. The molecular structures and thermodynamic stability of the complexes, formed from (S)-1 + Zn2+ and enantiomers of histidine, were calculated by Gaussian 16 based on density functional theory (DFT) to validate the above action mechanism.
Rhodium-catalyzed C4aryl−H activation and ring-retentive annulation of 2H-imidazoles with internal alkynes to build imidazo[5,1-a]isoquinolinium salts with high yields and broad scope has been disclosed. These novel salts serve as new full-color emissive fluorophores (433−633 nm), just by simply modifying the substituents on C3 and C4 positions of isoquinoline ring. Furthermore, these salts can undergo ring-opening C5aryl−H activation/annulation with a different alkyne to form non-symmetric and AIE-active 1,1′-biisoquinolines, where NH4OAc plays an indispensable role that accounts for Hofmann elimination and imine formation, leading to an unprecedented imine dance: cyclic imine → N-alkenyl imine → NH imine. The 15N labelling experiments indicate that the 2nd annulation includes two pathways: N-exchange (major) and N-retention (minor).
A rhodium-catalyzed desymmetrization reaction for enantioselective methyl C−H arylation is achieved by utilizing an in situ arylating reagent via nucleophilic cyclization of o-aminoaryl alkyne. The reaction results in chiral indoles containing all-carbon quaternary stereocenters under atmospheric conditions, with a wide range of substrates exhibiting good enantioselectivity (44 examples). Mechnism and DFT studies show that the stereocontrol is reasonably achieved through the collaborative control of a large silicon substituted chiral ligand and C−H···π, LP···π interactions between aryl rings of the carboxylate group and the substrate. Control experiments demonstrate that Rh-aryl bond formation via in situ nucleophilic cyclization is more critical for reaction efficiency than via C−H activation of the nucleophilic cyclization byproduct.
When zero-valent iron (ZVI) is prepared and applied under neutral conditions, it is easy to form oxides or hydroxides on its surface, which hinders the electron release of ZVI. To this end, a nucleophile was introduced into the ZVI system to inhibit the precipitation of iron ions, improve the conductivity of the solution, and promote the removal efficiency of electrophilic functional groups in organic compounds. In this study, the addition of nucleophiles such as ethylenediamine, methylamine and dimethylamine to the ZVI/H2O2 system resulted in an enhanced removal efficiency of tetracycline (TC) under neutral condition, while electrophiles such as EDTA-2Na and oxalic acid dihydrate impeded the removal of TC. Experimental results demonstrated that the presence of nucleophiles could effectively promote the release of iron ions and increase the proportion of ferrous in both aqueous solution and solid surface of ZVI. Experimental and theoretical calculation results revealed that the electrophilic functional group was eliminated in the TC molecule, and the toxicity of the treated solution was reduced significantly. Overall, this work provides a selection of the conditions and pollutants applicable to ZVI under neutral pH conditions.
An oxidative annulation of 2-arylidene-1,3-indanediones with Meldrum's acid has been developed for the divergent syntheses of spirolactones with a spirocenter located at the γ-position with respect to the carbonyl group. This heteroannulation protocol tolerates various functional groups and delivers moderate-to-good product yields. Interestingly, the reaction outcomes are exclusively controlled by the reaction oxidant/medium. This annulation strategy can also be executed in the flow system with decent product yields. Control experiments revealed that the reaction proceeds via a radical tandem annulation pathway.
Using hydrogen-bonded organic frameworks (HOFs) as photosensitizers to perform photocatalytic oxidation reactions under green and mild conditions is still a challenge for the application of HOFs materials. This study presents a novel approach that exploits HOFs to enhance the efficiency of photocatalytic oxidation for achieving visible light catalytic oxidation of styrene and its derivatives in the aqueous environment. By using 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4TBAPy) as the monomer, a pyrene-based hydrogen-bonded organic framework (PFC-1) with a microporous structure was successfully prepared. Compared with monomer H4TBAPy, due to the exciton effect and the interlayer confinement of HOFs, the singlet oxygen (1O2) production efficiency is significantly improved, which has great potential in photocatalytic oxidation reactions. Subsequently, the practicality of PFC-1 as a photocatalyst was studied, and the photocatalytic oxidation of styrene and its derivatives in aqueous solution was achieved under visible light with high catalytic efficiency, indicating that PFC-1 has significant potential to promote photocatalytic oxidation reactions under mild conditions. The utilization of HOFs as photosensitizers in this straightforward approach enables the attainment of green photocatalytic oxidation, hence expanding the potential applications of HOFs materials within the realm of photocatalysis.
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