Latest ArticlesFluorescent sensing for specific detection of berberine is an important issue in view of its potential jeopardization to food safety and human health, but remains less investigated. To the best of our knowledge, there is no fluorescence turn-on and ratiometric sensors available for specific detection of berberine. In this study, calix[4]carbazole (3) has been synthesized and its property of recognizing berberine has been evaluated by UV–vis, fluorescence, NMR, DLS and TEM techniques. The results show that 3 selectively recognizes berberine among the tested drugs and detects it with turn-on and ratiometric fluorescence due to their co-assembly nature. Moreover, 3 is not only low toxic and can reduce toxicity of berberine to human normal liver L02 cell, but also can release berberine to tumor HepG2 cells at acid micro-environment. It therefore holds a great potential for further exploration
With excellent color purity (full-width half maximum (FWHM) < 40 nm) and high quantum yield, multi-resonance (MR) molecules can harvest both singlet and triplet excitons for highly efficient narrowband organic light-emitting diodes (OLEDs) owing to their thermally activated delayed fluorescence (TADF) nature. However, the highly rigid molecular skeleton with the oppositely positioned boron and nitrogen in generating MR effects results in the intrinsic difficulties in the solution-processing of MR-OLEDs. Here, we demonstrate a facile strategy to increase the solubility, enhance the efficiencies and modulate emission color of MR-TADF molecules by extending aromatic rings and introducing tert-butyls into the MR backbone. Two MR-TADF emitters with smaller singlet-triplet splitting energies (ΔEST) and larger oscillator strengths were prepared conveniently, and the solution-processed MR-OLEDs were fabricated for the first time, exhibiting efficient bluish-green electroluminescence with narrow FWHM of 32 nm and external quantum efficiency of 16.3%, which are even comparable to the state-of-the-art performances of the vacuum-evaporated devices. These results prove the feasibility of designing efficient solution-processible MR molecules, offering important clues in developing high-performance solution-processed MR-OLEDs with high efficiency and color purity.
Helix structures at atomic/molecular level have not been found in self-assembled peptide sequence with less than three residues. As β-sheet supramolecular secondary structures have been discovered in solid-state amino acids, we here report the conjugation of simple N-terminal aryl protecting group could give rise to helical supramolecular secondary structures in solid-state, which determines the optical activities of the adjacent aryl groups. The carboxylic acid-involved asymmetric H-bonds in N-terminal aryl amino acids induce the emergence of super-helical structures of amino acid residues and aryl groups. In most cases, supramolecular tilted chirality of aryl groups is opposite to that of amino acid sequences, of which handedness and helical pitch are determined by the H-bond modalities. Determining correlation between supramolecular tilted chirality of aryl segments and their chiroptical activities is firstly unveiled, which was verified by the computational results based on density functional theory. Most aryl amino acids self-assembled by nanoprecipitation method via crystallization induced self-assembly into rigid one-dimensional microstructures with ultra-high Young's modulus. This study reveals the generic existence of chiral supramolecular structures in aggregated amino acid derivatives and gives an in-depth investigation into the structural-property relationships, which could guide the rational design and screening of chiroptical supramolecular materials.
Studies on the synthesis of antifungal and anticancer natural product, pseudolaric acid B, have led to the enantioselective synthesis of di-epi-trans-fused [5–7]-bicyclic core skeleton. The synthesis was achieved in 10 linear steps, which features the Sharpless asymmetric epoxidation, cyanide-opening reaction of epoxide, and intramolecular [5+2] cycloaddition reaction as the key transformations. The stereochemistry was determined by the X-ray crystallographic analysis.
Surface-enhanced Raman scattering (SERS) is a powerful spectroscopic tool in quantitative analysis of molecules, where the substrate plays a critical role in determining the detection performance. Herein, a silver nanocubes/polyelectrolyte/gold film sandwich structure was prepared as a reproducible, high-performance SERS substrate by the water/oil interfacial assembly method. In addition to the hot spots on the nanocubes surface, the edge-to-edge interspace of the Ag nanocubes led to marked enhancement of the SERS intensity, with a limit of detection of 10-11 mol/L and limit of quantitation of 10-10 mol/L for crystal violet. When rhodamine 6G and crystal violet were co-adsorbed on the Ag nanocube surfaces, the characteristic SERS peaks of the two molecules remained well resolved and separated, and the peak intensities varied with the respective concentration, which could be exploited for concurrent detection of dual molecules. Results from this work indicate that organized ensembles of Ag nanocubes can serve as effective SERS substrate can for sensitive analysis for complex molecular systems.
The utilization of thermal energy from different sources is an important development direction for conserving energy. With the development of technology, refined and rapid utilization of thermal energy is required. Traditional thermal conductive materials cannot meet the growing needs of human beings. Therefore, people pay attention to two-dimensional graphene film materials for their thermal conductivity. This review collects current modeling group of thermal transport on graphene, including non-equilibrium Green function (NEGF) theory, molecular dynamics (MD) simulations modeling and Boltzmann transport equation method. These models can well explain several phenomena of phonon transport in graphene. Further, structural defects were discussed and expounded the effect for graphene thermal conductivity, including doping, grain boundary and defects. Deeply understanding of defects on graphene, we can better grasp the thermal conductivity of graphene from the microscopic point of view.
Potassium-ion batteries (PIBs) have attracted enormous attention due to the abundance of potassium resources, low cost, fast ionic conductivity of electrolyte and relatively high operating voltage. Despite great efforts and progress, researches on PIBs are still at the initial stage, especially in the emerging field of flexible and wearable PIBs. The inevitable challenges for PIBs include low reversible capacity, unsatisfactory cycling stability and insufficient energy density, the solution to which mostly relies on designing advanced electrodes. Binder-free electrodes have emerged as promising electrode architecture for PIBs. Such electrodes avoid the use of insulating binders, which can be designed with various synergistic functional materials to address the aforementioned PIB issues and be endowed with flexibility/wearability. In this review, we mainly summarize the recent progress on binder-free electrodes for PIBs, with the focus on the methodologies, detailed strategies and functional materials for electrode construction. One strategy for binder-free electrodes is to assemble free-standing architecture with the help of carbon nanotubes (CNTs), graphitic fibers, and other carbon or mechanically robust materials, either alone or in combination. The other effective strategy is current collector substrate-assisted direct growth, including the use of carbon cloth, metal, MXenes and other conductive substrates. Additionally, challenges and research opportunities are put forward at the end as the guidance for future development of binder-free PIB devices.
Chemodivergent reactions of 2, 2-dimethoxyacetaldehyde and anilines were described, which were established on the basis of either a CC bond cleavage or a rearrangement process of a reaction intermediate. These reactions proceeded in a condition-determined manner with good functional group tolerance. In the first model, 2, 2-dimethoxyacetaldehyde reacted with aniline to form a new CN bond, in the presence of O2, via a CC bond cleavage reaction. However, in the second model, by performing the reaction in the absence of O2, Heyns rearrangement occurred and generated a new CO bond to form methyl phenylglycinate. Such condition-determined reactions not only offered the new way for value-added conversion of biomass-derived platform molecule, 2, 2-dimethoxyacetaldehyde, but also provided efficient methods for the synthesis of N-arylformamides and methyl phenylglycinates.
Tumor penetration is important for effectively tumor targeting drug delivery. Recently, many researches are published to overcome the barriers that restrict tumor penetration and improve drug delivery efficiency. In the mini review, we first analyzed the barriers influence the tumor penetration, including tumor microenvironment barriers, nanoparticle properties, and interaction barriers between tumor and nanoparticles. To overcome the barrier, several strategies are developed, including modulating tumor microenvironment, changing particle size, transcytosis enabled tumor penetration, cell penetrating peptide modification and overcoming binding site barrier, which could effectively improve tumor penetration, and finally enhance tumor treatment outcome.
Diseases caused by microbial bacteria such as Haemophilus influenzae type b (Hib), Streptococcus pneumoniae and Neisseria meningitidis are still very serious disease, which has brought a lot of burden to many countries. Development of vaccine has brought hope for the prevention of such diseases. Polysaccharide conjugate vaccines have been shown to have very good effects in preventing such diseases. The polysaccharide conjugate vaccine adds the positive characteristics of protein antigens to the polysaccharide antigen, thereby improving the immunogenicity of the polysaccharide antigen, solving the problem that the polysaccharide vaccine cannot be effectively applicated in toddler or children, which greatly promoting the development of this vaccine. This review introduces the progress of polysaccharide conjugate vaccines. We introduce the typical polysaccharide conjugate vaccines currently on the market firstly, and then elucidate the protein carriers, the coupling chemistry methods and quality control that required in the preparation of polysaccharide conjugate vaccines. We can see that polysaccharide conjugate vaccine is a kind of vaccine with great development potential, which can be a sharp edge for us to prevent diseases.
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