Latest ArticlesAqueous rechargeable Zn//MnO2 batteries have been considered as the promising candidate for future energy storage system due to their economic and environmental merits. However, the high-performance Zn//MnO2 batteries are plagued by poor sluggish reaction kinetics and capacity degradation due to the strong electrostatic interactions and complicated reaction process. Herein, the synergistic effect of atom defects engineering and phase transformation mechanism is confirmed as the effective strategy to enhance ion/charge transfer kinetics and structural stability. Defects gradient controlling and electrochemically induced phase transformation from spinel to layered structure render the aqueous Zn//λ-MnO2 system delivers a high discharge capacity of 285 mAh/g and capacity retention of 81% after 500 cycles.
Realizing efficient charge separation and directional transfer is a challenge for single-component semiconductors. The spatial electric field generated by dipole moment could promote charge separation. Here, three-dimensional hierarchical CuCo2S4 microspheres with lattice distortion were prepared, and lattice distortion was modulated by changing feed Co/Cu molar ratios in synthesis. CuCo2S4 showed asymmetric crystal structure, leading to generation of dipole moment. The charge separation efficiency of CuCo2S4 was related to lattice distortion, and lattice expansion was in favor for charge separation. The CuCo2S4 with feed Cu/Co molar ratio of 1:4 (CCS-4) showed the maximum lattice expansion and exhibited the highest photocatalytic activity, which was attributable to the highest charge separation efficiency and the largest specific surface area. CCS-4 can remove 95.4% of tetracycline hydrochloride within 40 min photocatalysis, and effectively improve the biodegradability of pharmaceutical wastewater. Importantly, this study provides a new vision for constructing single-component photocatalysts with high photocatalytic performance.
The development of carbon materials with high electrochemical performance for next-generation energy device is emerging, especially N, S co-doped carbon materials have sparked intensive attention. However, the exploration of N, S co-doped carbon with well-defined active sites and hierarchical porous structures are still limited. In this study, we prepared a series of edge-enriched N, S co-doped carbon materials through pyrolysis of thiourea (TU) encapsulated in zeolitic imidazolate frameworks (TU@ZIF) composites, which delivered very good oxygen reduction reaction (ORR) performance in alkaline medium with onset potential of 0.94 V vs. reversible hydrogen electrode (RHE), good stability and methanol tolerance. Density functional theory (DFT) calculations suggested that carbon atoms adjacent to N and S are probable active sites for ORR intermediates in edge-enriched N, S co-doped carbon materials because higher electron density can enhance O2 adsorption, lower formation barriers of intermediates, improving the ORR performance comparing to intact N, S co-doped carbon materials. This study might provide a new pathway for improving ORR activity by the integration engineering of edge sites, and electronic structure of heteroatom doped carbon electrocatalysts.
The unique structure of fluorescent proteins in which the fluorophore is encapsulated by the protein shell to restrict rotation and emit light inspired the screening of chromophores that selectively bind to biomolecules to generate fluorescence. In this paper, we report a curcuminoid-BF2-like fluorescent dye N-BF2 containing 4-dimethylaniline as an electron-donating group. When this dye is combined with HSA or BSA, the fluorescence is enhanced 90/112-fold, and the fluorescence quantum yield increases from < 0.001 to 0.16/0.19. Such a large change in fluorescence enhancement is due to the encapsulation of N-BF2 in the protein cavity by HSA/BSA, which inhibits the intramolecular rotation of the aniline moiety caused by charge transfer after the fluorophore is excited by light. N-BF2 has fast and strong binding to HSA or BSA and was found to be reversible in solution and intracellularly. Since N-BF2 also has the ability to target lipid droplets, the complex of N-BF2/HSA realizes the regulation of reversible lipid droplet staining in cells.
Through uncomplicated carbonation process, a carbon-embedded CoNiSe2/C nanosphere was synthesized from Ni-Co-MOF (metal-organic framework) precursor whose controllable structure and synergistic effect of bimetallic Ni/Co brought CoNiSe2/C anodes with high specific surface area (172.79 m2/g) and outstanding electrochemical performance. CoNiSe2/C anodes obtained reversible discharge capacities of 850.9 mAh/g at 0.1 A/g after cycling for 100 cycles. In addition, CoNiSe2/C exhibits excellent cycle stability and reversibility in the rate test at a current density of 0.1–2.0 A/g. When the current density returns to 0.5 A/g for 150 cycles, its discharge ratio the capacity is 330.8 mAh/g. Electrochemical impedance spectroscopy (EIS) tests suggested that CoNiSe2/C anodes had a lower charge transfer impedance of 130.02 Ω after 30 cycles. In-situ X-ray diffraction (XRD) tests confirmed the alloying mechanism of CoNiSe2/C which realized higher lithium storage capacity. This work affords substantial evidence for the extension of bimetallic selenides in secondary batteries, promoting the development of bimetallic selenides in anode materials for LIBs.
Exosome, which is a kind of extracellular vesicles with size around 40-160 nm, plays an important role in cell-to-cell communication in multiple diseases. Especially in tumor microenvironment, exosomes are the important pathway to transit proteins, nucleic acids and small molecules between different kinds of cells. Based on these characteristics, exosomes are served as both therapeutic agents and drug delivery systems in cancer therapy. In this review, the applications of exosomes as drug delivery systems in cancer therapy were summarized and classified according to the cell source of the exosomes, including normal cells, immune cells and tumor cells. Different modifications of exosomes and drug loading methods were presented. Finally, some challenges that hindered the clinical translation of exosomes were also discussed.
Coordination-driven self-assembly was used to construct two metallacycles of a dicarboxylate-functionalized dibenzo-18-crown-6 in combination with either a 0° anthracene-based clip-type acceptor or a 60° phenanthrene-based acceptor. The angularities of these moieties make them suitable for the formation of a [2 + 2] rectangle and a [3 + 3] triangle, respectively. The synthesis, characterization and host-guest chemistry of two metallacycles were described and supported by 31P{1H}, 1H NMR spectra and electrospray mass spectrometry.
Dynamic manipulation of enzymatic activity is a challenging task for applications in chemical and pharmaceutical industries due to the difficult modification and variable conformation of various enzymes. Here, we report a new strategy for reversible dynamic modulation of enzymatic activity by near-infrared light-induced photothermal conversion based on polyphenol-functionalized liquid metal nanodroplets (LM). The metal-phenolic nanocoating not only provides colloidal stability of LM nanodroplets but also generates nanointerfaces for the assembly of various enzymes on the LM nanodroplets. Upon near infrared (NIR) irradiation, the localized microenvironmental heating through photothermal effect of the LM nanodroplets allows tailoring the enzymatic activity without affecting the bulk temperature. A library of functional enzymes, including proteinase K, glucoamylase, glucose oxidase, and Bst DNA polymerase, is integrated to perform a reversible control and enhanced activities even after five times of cycles, demonstrating great potential in bacterial fermentation, bacteriostasis, and target gene amplification.
The issue about how outstanding scientists obtained innovative findings has drawn the interest of researchers in science, policy and scientometrics. Here, we attempt to address this question by using computational methods to measure the cognitive content and concepts of K. Barry Sharpless' research and estimate the knowledge flow of his click chemistry to other fields. First, we traced Sharpless' conceptual journey over time through topic modeling approach, mapping and clustering of the epistemic network from distant reading his publications. We find that connectivity and functions, the core features of click chemistry, are embodied in his constant search for simplicity. What makes simplicity possible is his continuous work with collaborators on reactivity and reaction mechanisms. Moreover, citation and link analysis show that click chemistry had a much richer impact on other research fields than what is generally acknowledged, and drew solutions to significant and practical questions back to chemistry from biology. Together with these findings, we propose that the click chemistry philosophy follows the way that values nature's principle. Chemistry has a clear-cut epistemic domain in modeling Nature. Thus, click chemistry as a concept on doing science beyond a connective technology goes across the boundaries between disciplines and impacts many other fields.
Derivative-extremum analysis (DEA) of j-E curves is a newly proposed method of half wave potential (E1/2) and activation feature extraction from steady-state voltammetry. Here, the DEA is demonstrated to be valid in the full range of reversibility using numerical simulations with a derived universal electrode equation, providing a novel perspective of electrochemical kinetics in the reversibility domain. The results reveal that E1/2 is a better choice of the reference potential instead of equilibrium potential (Eeq) in electrode equations, especially since Eeq is meaningless in an irreversible case. The equations referenced with standard potential, E1/2 and Eeq, are summarized in three tables, and their applications in parameter determinations are specified. Finally, reversibility is proved to be a relative measure between kinetic slowness and mass transport of electroactive species, and the reversibility classifications are proposed according to the DEA feature in the reversibility domain. This work, based on the DEA principle, refines the electrode equation forms and generalizes their applicability in the full range of reversibility.
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