Latest ArticlesRational design of electrode meterials with unique core-shell nanostructures is of great significance for improving the electrochemical performance of supercapacitors. In this work, we prepare several CuCo2O4@Ni-Co-S composite electrodes by a controllable hydrothermal and electrodeposition route. One-dimensional nanowires can shorten the ions transport path, while two-dimensional nanosheets expose many active sites. This enables three-dimensional structured composite with high electrochemical activity. The as-prepared heterostructured materials show a specific of 1048 C/g at 1 A/g. It still maintains 75.6% of initial capacity after 20000 cycles at 10 A/g. The device delivers an energy density of 79.2 Wh/kg when the power density reaches to 2280 W/kg. Moreover, it possesses an excellent mechanical stability after repeated folding at different angles
The similarity of local structure-connection pattern and volumetrically compressive strain between host and guest phases can be used to stabilize heteroid metastable matter and tune the local structure and properties. Here a series of metastable ABO3 (A = Mn; B = Mn0.5Mo0.5, Mn1/3Ta2/3, and Mn0.5Ta0.5) were trapped in LiTaO3 to form solid-solutions, where the difference of solid solubility limit reveals the barrier of size effect on chemical pressure. All samples show antiferromagnetic characters, in which the (LiTaO3)1--[Mn(Mn0.5Mo0.5)O3] series exhibit more complex magnetic and dielectric behaviors with the increasing of metastable guest phase, stemming from the complex interactive mechanism between Mn2+ and Mo6+. The cell parameter variation of (LiTaO3)1--[Mn(Mn0.5Ta0.5)O3] shows a more regularly changing tendency, on account of the smallest size barrier. These findings show that chemical pressure can effectively stimulate the physical pressure to intercept and modulate a metastable phase at atomic-scale by compressibility effect between like structures at ambient pressure.
The development of efficient and cost-effective electrocatalysts for oxygen evolution reaction (OER) is crucial for the overall water splitting. Herein, we prepared a highly exposed NiFeOx ultra-small nanoclusters supported on boron-doped carbon nonotubes catalyst, which achieves a 10 mA/cm2 anodic current density at a low overpotential of 213 mV and the Tafel slope of 52 mV/dec in 1.0 mol/L KOH, superior to the pristine NiFeOx-CNTs and other state-of-the-art OER catalysts in alkaline media. A combination study (XPS, sXAS and XAFS) verifies that the local atomic structure of Ni and Fe atoms in the nanoclusters are similar to NiO and Fe2O3, respectively, and the B atoms which are doped into the crystal lattice of CNTs leads to the optimization of Ni 3d eg orbitals. Furthermore, in-situ X-ray absorption spectroscopies reveal that the high valence state of Ni atoms are served as the real active sites. This work highlights that the precise control of highly exposed multicomponent nanocluster catalysts paves a new way for designing highly efficient catalysts at the atomic scale.
Stimulus-responsive vesicles have broad applications in a variety of areas. Herein, oxidation-responsive framboidal triblock copolymer vesicles are prepared by photoinitiated RAFT seeded emulsion polymerization of a thioether-functionalized monomer using diblock copolymer vesicles as seeds. The obtained framboidal vesicles can transform into worms or spheres in the presence of reactive oxygen species, which can be further used for controlled release of cargos (e.g., silica nanoparticles).
Utilizing metal-organic frameworks (MOFs) to design photocatalysts for CO2 reduction catalysts is an excellent idea but currently restricted by the relatively low activity. Enhancing CO2 affinity and tuning the oxidation state of metal clusters in MOFs might be a solution to improve the catalytic performance. Herein, the Cl-bridge atoms in the metal clusters of a cobalt MOF were easily exchanged with OH−, which simultaneously oxidized a portion of Co(Ⅱ) to Co(Ⅲ) and resulted in a much enhanced photocatalytic activity for CO2 reduction. In contrast, the original framework does not exhibit such superior activity. Comprehensive characterizations on their physicochemical properties revealed that the introduction of hydroxyl group not only greatly increases the CO2 affinity but also alters the oxidation state of metal clusters, resulting in significantly improved photocatalytic activities for CO2 reduction. This work provides important insight into the design of efficient photocatalysts.
Angiotensin-converting enzyme 2 (ACE2) is not only an enzyme but also a functional receptor on cell membrane for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, the activity of ACE2 in single living cell is firstly determined using a nanokit coupled electrospray ionization mass spectrometry (nanokit-ESI-MS). Upon the insertion of a micro-capillary into the living hACE2-CHO cell and the electrochemical sorting of the cytosol, the target ACE2 enzyme hydrolyses angiotensin II inside the capillary to generate angiotensin 1–7. After the electrospray of the mixture at the tip of the capillary, the product is differentiated from the substrate in molecular weight to achieve the detection of ACE2 activity in single cells. The further measurement illustrates that the inflammatory state of cells does not lead to the significant change of ACE2 catalytic activity, which elucidates the relationship between intracellular ACE2 activity and inflammation at single cell level. The established strategy will provide a specific analytical method for further studying the role of ACE2 in the process of virus infection, and extend the application of nanokit based single cell analysis.
The direct epoxidation of propylene by O2 is a significant and challenging topic. The key factor for this homogeneous aerobic epoxidation is the activation of molecular oxygen under mild conditions. In this work, the aerobic epoxidation of propylene catalyzed by manganese porphyrins was achieved in the presence of isoprene. Isoprene contains an allyl methyl group, and the α-H can be easily removed to achieve the activation of molecular oxygen. The conversion of propylene was 38% and the selectivity toward propylene oxide (PO) was up to 87%. The role of isoprene was demonstrated, and a plausible mechanism was proposed. The protocol reported herein is expected to provide a strategy for the simultaneous preparation of propylene oxide and isoprene monoxide.
5-Formylcytosine (5fC), as an important epigenetic modification, plays a vital role in diverse biological processes and multiple diseases by regulating gene expression. Owing to the extremely low abundance of 5fC in all mammalian tissues and high structural similarity with other cytosine derivatives, the precise and sensitive detection of 5fC is challenging. Herein, a photo-elutable and template-free isothermal amplification strategy has been proposed for the sensitive detection of 5fC in genomic DNA based on 5fC-specific biotinylation, enrichment, photocleavage, and terminal deoxynucleotidyl transferase (TdT)-assisted fluorescence signal amplification, which is termed 5fC-PTIAS. By introducing the highly specific chemolabeling and the one-step photoelution processes, this strategy possesses a minimal nonspecific background as well as a much higher amplification efficiency. With the high signal-to-noise ratio, this strategy can achieve the accurate quantification of 5fC in various biological samples including mouse brain, kidney, and liver, with a limit of detection (LOD) of 0.025‰ in DNA (S/N = 3). These results not only confirm the widespread distribution of 5fC but also indicate its significant variation in different tissues and ages. The bisulfite- and mass spectrometry-free strategy is highly sensitive, selective, and easily mastered, holding great promise in detecting other epigenetic modifications with much lower levels.
Ribosomal RNAs (rRNAs) provide the structural framework of ribosomes and play critical roles in protein translation. In ribosome biogenesis, rRNAs acquire various modifications that can influence the structure and catalytic activity of ribosomes. However, rRNA modifications in plants have yet to be fully defined. Herein, we proposed a method to purify rRNAs by a successive isolation with different strategies, including polyA-based mRNA depletion and agarose gel electrophoresis-based purification, with which highly pure rRNAs could be obtained. In addition, we developed a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method to systematically profile and characterize modifications from the isolated highly pure plant 18S rRNA and 25S rRNA. LC-ESI-MS/MS analysis showed that 10 and 12 kinds of modifications were present in plant 18S rRNA and 25S rRNA, respectively. Notably, among these identified modifications, 2 kinds of modifications of N2,N2-dimethylguanosine (m2,2G) and N6,N6-dimethyladenosine (m6,6A) in 18S rRNA, and 4 kinds of modifications of m2,2G, m6,6A, N7-methylguanosine (m7G) and 3-methyluridin (m3U) in 25S rRNA, were first reported to be present in plants. Moreover, exposure of Arabidopsis thaliana to cadmium (Cd) led to significant changes of modifications in both 18S rRNA and 25S rRNA of plants, indicating that rRNA modifications play important roles in response to environmental stress. The discovery of new modifications in plant rRNAs improves the spectra of plant rRNA modifications and may promote the investigation of the functional roles of plant ribosomes in regulating gene expression.
A series of α-MnO2 catalysts with various Mn valence states were treated by hydrogen reduction for different periods of time. Their catalytic capacity for formaldehyde (HCHO) oxidation was evaluated. The results indicated that hydrogen reduction dramatically improves the catalytic performance of α-MnO2 in HCHO oxidation. The α-MnO2 sample reduced by hydrogen for 2 h possessed superior activity and could completely oxidize 150 ppm HCHO to CO2 and H2O at 70 ℃. Multiple characterization results illustrated that hydrogen reduction contributed to the production of more oxygen vacancies. The oxygen vacancies on the catalyst surface enhanced the adsorption, activation and mobility of O2 molecules, and thereby enhanced HCHO catalytic oxidation. This study provides novel insight into the design of outstanding MnOx catalysts for HCHO oxidation at low temperature.
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