Latest ArticlesExploring efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) electrocatalysts is crucial for developing water splitting devices. The composition and structure of catalysts are of great importance for catalytic performance. In this work, a heterogeneous Ru modified strategy is engineered to improve the catalytic performance of porous NiCo2O4 nanosheets (NSs). Profiting from favorable elements composition and optimized structure property of decreased charge transfer barrier, more accessible active sites and increased oxygen vacancy concentration, the Ru-NiCo2O4 NSs exhibits excellent OER activity with a low overpotential of 230 mV to reach the current density of 10 mA/cm2 and decent durability. Furthermore, Ru-NiCo2O4 NSs show superior HER activity than the pristine NiCo2O4 NSs, as well. When assembling Ru-NiCo2O4 NSs couple as an alkaline water electrolyzer, a cell voltage of 1.60 V can deliver the current density of 10 mA/cm2. This work provides feasible guidance for improving the catalytic performance of spinel-based oxides.
Fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids are effective building blocks in self-assembled architectures at hierarchical levels, which however show limited luminescent properties and chiroptical activities. Here we introduce a charge-transfer strategy to build two-component luminescent materials with emerged circularly polarized luminescence properties. A library of Fmoc-amino acids was built, which selectively form charge-transfer complexes with the electron-deficient acceptor. Embedding in amorphous polymer matrix or physical grinding could trigger the charge-transfer luminescence with adjusted wavelengths in a general manner. X-ray diffraction results suggest the multiple binding modes between donor and acceptor. And, the solution-processed coassembly could selectively exhibit circularly polarized luminescence with high dissymmetry g-factors. This work illustrates a noncovalent charge-transfer strategy to construct luminescent and chiroptical organic composites based on the easy-accessible and economic chiral N-terminal aromatic amino acids.
The low-cost CuBr-promoted domino Biginelli reaction among readily available ketones, salicylaldehyde derivatives and 3-amino-1, 2, 4-triazole was studied under solvothermal conditions, giving the novel bridged polyheterocycles bearing two or three stereocenters depending on the starting ketones. This multicomponent reaction proceeded with high diastereoselectivity (dr > 20:1) based on a combined 1H NMR, crystallographic and supercritical fluid chromatographic (SFC) analysis of the product. Time-dependent high-resolution mass spectrometry (HRMS) was performed to track the reaction process, and several key intermediates were identified, leading to the drawing of a plausible reaction mechanism. Density functional theory (DFT) calculation was supplemented, and two reaction pathways were differentiated. Moreover, in vitro antitumor activity was evaluated using HeLa and HepG2 cell lines, and two of these polyheterocycles demonstrated promising activities against HepG2 cells with EC50 down to 10 µmol/L. Additionally, ESI-MS/MS studies on all the polyheterocycles suggest a common fragmentation pathway (loss of one molecule of amino-triazole) they shared, providing the first-hand fragmentation rules for future rapid structural identification of them. The multicomponent domino reaction presented here may offer prospects for future design of more efficient strategies to access medicinally important bridged polyheterocycles.
Highly selective binding of structurally similar substrates is common for biomolecular recognition, but is often challenging to realize in synthetic hosts. Herein, we report highly selective binding of methyl viologen over other analogues by an endo-functionalized naphthobox. X-ray single crystal structure and Density Functional Theory (DFT) calculations revealed that the endo-functionalized groups in the cavity of the naphthobox is important for the high binding selectivity through the formation of multiple C–H…N, C–H…π, and π…π interactions with methyl viologen.
CO oxidation is a vital catalytic reaction for environmental purification, facing challenges due to the catalysts applied to oxidize CO are mainly rare and expensive noble catalysts. Since the high atomic availability, catalytic efficiency, and selectivity of single-atom catalysis, it has been widely studied and proven to be brilliant in CO oxidation. Au single-atom catalysts are regarded as excellent single-atom catalysts in oxidizing CO, whose progress is limited by the indistinct understanding of the reaction mechanism and role of the active atom. Hence, DFT calculation was used to investigate CO oxidation processes, active mechanisms, and the role of Au single-atom. Graphene involving prominent physical and chemical properties was selected as a model supporter. The single-atom support graphene materials exhibit better CO oxidation activities than pristine graphene, among which CO oxidation property on Au/GP is the highest with a 0.38 eV rate-determining barrier following ER mechanism. The outstanding performances including excellent electronic structures, adsorption properties, and strong activation of intermediate products contribute to the high CO oxidation activity of Au/GP, and the Au single-atom is the active center. Our work provides a novel guide for single-atom catalytic CO oxidation, accelerating the development of single-atom catalysis.
Simple saccharides have a variety of biological functions, but their structural diversity and inherent structural features pose a major challenge for rapid analysis. In this work, we developed a derivative-free and ion mobility-free method for the rapid analysis of monosaccharides and disaccharides using paper spray tandem mass spectrometry. Trimeric cluster ions consisting of saccharide analytes, ligands and transition metal ions are used as precursor ions. We defined the R-value as the ratio of the intensity of the product ion that loses one molecule of ligand over the intensity of the product ion that loses one molecule of saccharide via collision induced dissociation (CID). The species and conformation of simple saccharides can be easily differentiated by calculating this R-value. With the capability of directly analyzing clinical samples using paper spray ionization, our method can be used to rapidly quantify the molar ratio of galactose to glucose in dried plasma samples to aid in the diagnosis of galactosemia. The analytical strategy provided herein has good potential to be applied to a wide range of saccharide analysis applications in the future.
As the connecting part of diet and host physiology, intestinal microbes can convert the ingested diet into a huge number of physiologically active small molecules. Indole metabolites of tryptophan are precursors or signal molecules for many biologically active substances, which are involved in serotonin and microbial catabolism pathways. To understand the influence of tryptophan metabolism in the intestinal environment on the neurological and immune systems at the molecular level, it is important to establish a high-coverage analytical method to comprehensively analyze the metabolites involved in tryptophan metabolism. However, due to a small molecular weight and poor response during mass spectrometry analysis, as well as weak retention on the reversed-phase chromatography, determination of indole metabolites of tryptophan is challenging. Here, we proposed a method for the simultaneous determination of 20 indole metabolites of tryptophan in a single run on reversed-phase chromatography by chemical labeling coupled to liquid chromatography-tandem mass spectrometry analysis. 4-(Dimethylamino)benzaldehyde (DMAB) was used for the labeling of indole metabolites of tryptophan, which could significantly improve the detection sensitivities and retention of these metabolites on reversed-phase chromatography. With the developed method, we realized the sensitive detection and comprehensive analysis of 15 endogenous indole metabolites of tryptophan in rat feces samples with functional dyspepsia intervention by acupuncture. The developed method offers a useful tool for studying tryptophan metabolism-related diseases.
Deuteriodifluoromethyl (CF2D) is a challenging and important functional group due to difficult deuterium incorporation and lack of effective precursor reagents. Herein, we report a bench-stable reagent, deuteriodifluoromethyl phosphine (DDFP) from cheap deuterium source for selectivity deuteriodifluoromethylation of azines with a high deuterium incorporation yield. The late-stage modification of complex molecules further confirmed the potential of this reagent for practical applications. We expect that our reagent to find applications in synthesis of isotope-labelled molecules of interests for drug-discovery and related ilucidation of mechanism of action.
Cascading reactions in fluorophores accompanied by the replacement of different fluorescence wavelengths can be used to develop luminescent materials and reactive fluorescent probes. Based on multiple signal channels, the selectivity of probes can be improved and the range of response to guest molecule recognition can be expanded. By regulating the position, number, and activity of active sites in fluorophores, fluorescent probes that successively react with thiol and amino groups in cysteine (Cys), homocysteine (Hcy) have been developed, which can only react with the thiol group of GSH. In this paper, we report the first probe capable of cascading nucleophilic substitution reaction with the thiol group and amino group of GSH at a single reaction site, and showed the dual-color recognition of GSH, which improved the selectivity of GSH also was an extension of GSH probes. The probe Rho-DEA was based on a TICS fluorophore, and the intramolecular cascade nucleophilic substitution reaction occurs with Cys/Hcy. The thiol substitution of the first step reaction with Cys/Hcy was quenched due to intersystem crossing to triplet state, so GSH can be selectively recognized from the fluorescence signal. Rho-DEA has the ability of mitochondrial localization, and finally realized in situ dual-color fluorescence recognition of GSH in mitochondria.
A bistable [2]rotaxane with a conformation-adaptive macrocycle bearing a 9, 14-diphenyl-9, 14-dihydrodibenzo[a, c]phenazine (DPAC) unit was synthesized, which could be utilized to optical probe the molecular shuttling motion of the functionalized rotaxane system. The UV–vis, 1H NMR and PL spectroscopic data clearly demonstrated that the DPAC ring was interlocked onto the thread and the fluorescence intensity of the DPAC unit in the macrocycle was effectively regulated by the location change of the macrocycle along the thread under acid/base stimulation, which was attributed to the modulation of the intramolecular photo-induced electron transfer between the DPAC unit and the methyltriazole (MTA) unit. This bistable rotaxane system containing a conformation-adaptive fluorophore unit in the macrocycle moiety opens an alternative way to design functional bistable mechanically interlocked molecules.
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