Latest ArticlesNanopore detection is a hot issue in current research. One of the challenges is how to slow down the transport velocity of nanoparticles in nanopores. In this paper, we propose a functional group modified nanopore. That means a polyelectrolyte brush layer is grafted on the surface of the nanopore to change the surface charge properties. The existing studies generally set the charge density of the brush layer to a fixed value. On the contrary, in this paper, we consider an essential property of the brush layer: the volume charge density is adjustable with pH. Thus, the charge property of the brush layer will change with the local H+ concentration. Based on this, we established a mathematical model to study the transport of nanoparticles in polyelectrolyte brush layer modified nanopores. We found that pH can effectively adjust the charge density and even the polarity of the brush layer. A larger pH can reduce the transport velocity of nanoparticles and improve the blockade degree of ion current. The grafting density does not change the polarity of the brush charge. The larger the grafting density, the greater the charge density of the brush layer, and the blockade degree of ion current is also more obvious. The polyelectrolyte brush layer modified nanopores in this paper can effectively reduce the nanoparticle transport velocity and retain the essential ion current characteristics, such as ion current blockade and enhancement.
This work demonstrates a two-step method to produce oxide-derived Cu nanowires on Cu mesh surface to offer a monolithic catalyst that outstandingly improves the hydrogen production from reforming formaldehyde and water under ambient conditions. Our results not only reveal that the special oxide-derived nanostructure can significantly improve the formaldehyde reforming performance of Cu, but also display that the hydrogen production has a linear relationship with oxygen pressure. Specially, a maximum of 36 times increment in hydrogen generation rate is observed than that without oxygen during the reaction. Density functional theory calculations show that the formaldehyde molecule is adsorbed on Cu surface only when the adsorbed oxygen is in adjacency, and hydrogen release process is the rate-determining step. This work highlights that the activity of deliberately synthesized catalyst can further be promoted by dynamic chemical modulation of surface states during working.
Quantum dots (QDs) based heterojunction is a candidate for the photocatalytic CO2 reduction, owing to the large extinction coefficient and easy modification of band structures. However, the van der Waals interaction causes the large charge resistance and strong recombination centers between QDs and host materials, which makes the poor photocatalytic performance. Herein, a covalent bonded CdSeTe QDs and NH2-UiO-66 heterojunction (NUC-x) is constructed through an acylamino (-CONH-). The results indicate that the acylamino between NH2-UiO-66 and CdSeTe QDs can serve as the transfer channels for the photogenerated charges and stabilize the QDs. The optimized NUC-1200 achieved a CO generation rate of 228.68 µmol/g, which is 13 and 4 times higher than that of NH2-UiO-66 and CdSeTe QDs, respectively. This work provides a new avenue for efficient and stable photocatalysis of QDs.
Developing redox switches that not only perform specific mechanical movements but also drive important chemical reactions is important but a great challenge. Herein, we report a redox pair of cobalt species (CoⅢ/CoⅡ) that switches through photo-dehydrogenation of alcohol and hydrogenation of azo-ligand. The cobalt species is equipped with a flexible azo-ligand containing two bulky planar substituents. A planar oxidated sate (CoⅢ species) can be photo-reduced to a saddle-like reduced state (CoⅡ) with alcohol molecules as electron donors, and in turn the CoⅢ species can be recovered with azo-ligand as oxidant under acidic surrounding. Both the redox states of the pair are isolated and characterized by single crystal X-ray diffraction. In the switching cycle, alcohol is oxidized to aldehyde by azo-ligand through proton coupled electron transfer and the cobalt complex acts as a redox catalyst. These results provide important insights into alcohol dehydrogenation catalyzed by redox complexes.
Schisandrin A is a natural dibenzocyclooctene lignan with potent neuroprotective activity. However, the specific mechanisms or direct target proteins have not been clarified up to now. In this study, we designed and synthesized the probes of schisandrin A with photoreactive diazirine and clickable alkyne to identify its direct target in SH-SY5Y cells by employing activity-based protein profiling (ABPP) technique. Ykt6 was prominent among the 13 proteins obtained with high confidence and we confirmed Ykt6 as the direct target of schisandrin A by CETSA, IF, SPR and knockdown assay. Functionally, schisandrin A protected the cells against the injury induced by glutamate by regulating autophagy via Ykt6. This discovery may provide a novel therapeutic option for various neuronal cell damage-mediated diseases.
The electrochemical nitrogen reduction reaction (NRR) for the ammonia production under ambient conditions is regarded as a sustainable alternative to the industrial Haber–Bosch process. However, the electrocatalytic systems that efficiently catalyze nitrogen reduction remain elusive. In the work, the nitrogen reduction activity of the transition metal decorated bismuthene TM@Bis is fully investigated by means of density functional theory calculations. Our results demonstrate that W@Bis delivers the best efficiency, wherein the potential-determining step is located at the last protonation step of *NH2 + H+ + e– → *NH3 via the distal mechanism with the limiting potential UL of 0.26 V. Furthermore, the dopants of Re and Os are also promising candidates for experimental synthesis due to its good selectivity, in despite of the slightly higher UL of NRR with the value of 0.55 V. However, the candidates of Ti, V, Nb and Mo delivered the relative lower UL of 0.35, 0.37, 0.41 and 0.43 V might be suffered from the side hydrogen evolution reaction. More interestingly, a volcano curve is established between UL and valence electrons of metal elements wherein W with 4 electrons in d band located at the summit. Such phenomenon originates from the underlying acceptance-back donation mechanism. Therefore, our work provides a fundament understanding for the material design for nitrogen reduction electrocatalysis.
Using a ditopic organic linker 4-(1H-pyrazol-4-yl)benzoic acid (H2pba), FICN-6, a metal-organic framework containing both Cu2(O2CR)4 and Cu3(OH)(pyz)3(O2CR) secondary building units (SBUs), was synthesized. FICN-6 adopts in an unusual intercatenated structure with SBUs from two distinct networks connecting to each other. Presence of Cu3 clusters makes FICN-6 a good heterogeneous catalyst for oxygen activation and aerobic oxidative C-C coupling of organic boronic acids.
Fluoranthenes have attracted tremendous attention due to their unique optoelectronic properties and extensive applications. Although several synthetic methodologies have been developed for the preparation of fluoranthene derivatives, it is still unfavorable to functionalize the fluoranthene framework at different positions due to the relatively low selectivity and reactivity. Herein, a catalyst-free intramolecular [4 + 2] annulation between thiophenes and alkynes is developed towards the synthesis of fluoranthenes. Altogether 20 examples have been demonstrated using this method. Various functional groups can be precisely introduced into the fluoranthene skeleton at different positions by simply tuning the substituents on the thiophenes and alkynes. The conjugation of the fluoranthene can be facilely extended through different directions. Furthermore, the feasibility of this [4 + 2] annulation reaction is also investigated by density functional theory calculations. Therefore, this protocol provides not only a synthetic methodology towards fluoranthenes with substituents functionalized at different positions, but also an effective pathway to construct large polycyclic aromatic hydrocarbons containing fluoranthene moieties.
Through-space charge transfer (TSCT) is regarded as an effective way to develop thermally activated delayed fluorescence (TADF) emitters. Based on this strategy, many molecular frameworks have been proposed, among which spirobased scaffolds have been extensively studied due to their unique advantages. In this work, we developed three emitters SPS, SPO, and SPON, which were constructed with the same donor and various acceptors to explore the influence of acceptor modulation at the C9 position of fluorene for spirostructure TSCT emitters. The results show that the acceptor with too weak electron-withdrawing ability will cause the emitter to not have TADF properties, while the acceptor with too much steric hindrance will weaken the face-to-face π-π stacking interaction between donor/acceptor (D/A). Since SPO balances the electron-withdrawing strength and steric hindrance of the acceptor, it achieves the highest external quantum efficiency (EQE) of 17.75%. This work shows that appropriate acceptor selection is essential for the TADF properties and high efficiency of the spirobased scaffold TSCT emitter
Aqueous zinc-ion batteries (ZIBs) has been regarded as a promising energy storage system for large-scale application due to the advantages of low cost and high safety. However, the growth of Zn dendrite, hydrogen evolution and passivation issues induce the poor electrochemical performance of ZIBs. Herein, a Na3Zr2Si2PO12 (NZSP) protection layer with high ionic conductivity of 2.94 mS/cm on Zn metal anode was fabricated by drop casting approach. The protection layer prevents Zn dendrites formation, hydrogen evolution as well as passivation, and facilitates a fast Zn2+ transport. As a result, the symmetric cells based on NZSP-coated Zn show a stable cycling over 1360 h at 0.5 mA/cm2 with 0.5 mAh/cm2 and 1000 h even at a high current density of 5 mA/cm2 with 2 mAh/cm2. Moreover, the full cells combined with V2O5-based cathode displays high capacities and high rate capability. This work offers a facile and effective approach to stabilizing Zn metal anode for enhanced ZIBs.
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