Latest ArticlesAmmonia (NH3), as an important chemical substance and clean energy carrier, plays an indispensable role in industrial and agricultural production. The electrocatalytic synthesis of NH3 under mild conditions has attracted worldwide attention in the energy field due to its environmental friendliness and cost efficiency, but unsatisfactory NH3 yields and Faradaic efficiencies are restricting its development. The introduction of defect has been demonstrated as a feasible way to overcome the disadvantages of electrochemistry, as it can regulate the electronic structure and modulate coordination environment of electrocatalysts, which further create active sites and enhance nitrogen adsorption. In this regard, it is necessary to understand the effects of various types of defects on electrocatalysts based on the latest progress in the defect engineering for nitrogen reduction reaction (NRR). In this review, the concept, classifications, and characterization of defects as well as the approaches to create them in electrocatalysts are firstly discussed. Then, certain types of defects (vacancy, dopant, amorphism, edge/corner, and porousness) affecting the performances of various electrocatalysts are further described. Finally, the summary and challenges of electrocatalytic ammonia synthesis are proposed to design advanced electrocatalysts with high efficiency.
We report that the photoinduced dynamics of the phytochrome chromophore is strongly dependent on the protonation/deprotonation states of the pyrrole ring. The on-the-fly surface hopping dynamics simulations were performed to study the photoisomerization of different protonation/deprotonation phytochrome chromophore models. The simulation results indicate that the deprotonations at the pyrrole rings significantly modify the photoinduced nonadiabatic dynamics, leading to distinctive population decay dynamics and different reaction channels. Such feature can be well explained by the formation of the different hydrogen bond network patterns. Therefore, the proper understanding of the photoisomerization mechanism of phytochrome chromophore must take the hydrogen bond network into account. This work provides the new insights into the photobiological functions of phytochrome chromophore and suggests the possible ideas to control of its photoconversion processes for further rational engineering in optical applications.
A photoactive polyoxometalate-based metal−organic framework (POMOF), NiW-DPNDI, was synthesized by combination of Ni(Ⅱ) ions, [ZnW12O40]6‒ anions, and N, N'-bis(4-pyridylmethyl)naphthalene diimide (DPNDI) molecules into one single framework. NiW-DPNDI displays a three-dimensional structure by the strong anion⋯π interactions between the trapped [ZnW12O40]6‒ anions and the electron-deficient naphthalenic ring centroids and the π−π stacking interactions between DPNDI moieties. NiW-DPNDI displayed a highly efficient hole-electron separation and ordered electron transfer under irradiation, thus ensuing its excellent photocatalysis in oxidation of styrene to produce benzaldehyde. In addition, it gave a high efficiency for styrene oxide under thermocatalytic conditions. Because the carbonic anhydrase (CA)-mimicking Ni sites and the negative electron-enriched [ZnW12O40]6‒ anions are well aligned in the pores, it can promote the cycloaddition of CO2 with epoxides under mild conditions.
Localized high-concentration electrolytes (LHCE) have shown good compatibility with high-voltage lithium (Li)-metal batteries, but their practicality is yet to be proved in terms of cost and safety. Here we develop a hybrid-LHCE with favorable integrated properties by combining the merits of two representative diluents, fluorobenzene (FB) and 1, 1, 2, 2-tetrafluoroethyl-2, 2, 2-trifluoroethyl ether (TFE). Specifically, the extremely cheap and lightweight FB significantly reduces the cost and density of electrolyte, while the fire-retardant TFE circumvents the flammable nature of FB and thus greatly improves the safety of electrolyte. Moreover, the FB–TFE mixture enhances the thermodynamic stability of hybrid-LHCE and renders a controllable defluorination of FB, contributing to the formation of a thin and durable inorganic-rich solid electrolyte interphase (SEI) with rapid ion-transport kinetics. Benefiting from the designed hybrid-LHCE, a Li|NCM523 battery demonstrates excellent cycling performance (215 cycles, 91% capacity retention) under challenging conditions of thin Li-anode (30 µm) and high cathode loading (3.5 mAh/cm2).
The accurate delivery of nanoparticles and organic small molecule drugs remains a serious challenge in nanoparticle-based tumor therapy. Dual-targeted therapy combining tumor cell targeting and organelle targeting is an effective solution. Here, an anticancer nanoformulation accurate delivery system was prepared using hyaluronic acid (HA) targeting CD44 receptors on the surface of tumor cells and IR780 iodine (IR780) targeting mitochondrial for delivery. The system is based on an ultra-small Janus structured inorganic sensitizer TiO2-x@NaGdF4 nanoparticles (TN NPs) prepared by one-step pyrolysis, further loaded with organic small molecule acoustic sensitizer IR780 and mitochondrial hexokinase Ⅱ inhibitor lonidamine (LND), followed by encapsulation of HA. Ultra-small size nanoparticles exhibit strong tissue penetration, tumor inhibition and in vivo metabolism. Under ultrasound radiation, TN NPs and IR780 could produce a synergistic effect, effectively increased the efficiency of reactive oxygen species (ROS) production. Meanwhile, the released IR780 could smoothly target the mitochondria, and the ROS produced by IR780 can destroy the mitochondrial structure and disrupt the mitochondrial respiration. LND could inhibit the energy metabolism of tumor cells by reducing the activity of hexokinase Ⅱ (HK Ⅱ), which further accelerates the process of apoptosis. Furthermore, since the Janus structure allows the integration of multifunctional components into a single system, TN NPs can not only serve as an acoustic sensitizer to generate ROS, but the Gd element contained can also act as the nuclear magnetic resonance (MR) imaging contrast agent, suggesting that the nanoformulation can enable imaging-guided diagnosis and therapy. In conclusion, a new scheme to enhance sonodynamic therapy (SDT) and chemotherapy synergistically is proposed here based on ultra-small dual-targeted nanoformulation with Janus structure in the ultrasound radiation environment.
Developing sustainable and powerful heterogeneous catalytic systems to convert sulfides into high-value sulfoxide products has become a particularly appealing field and an arduous challenge. In this work, two porous polyoxometalate-pillared metal-organic frameworks, formulated as H3n[Cu3(pidc)2(H2O)2.5]2[PW12O40]n·xH2O (n = 1.5, x = 6 for 1, n = 1, x = 12 for 2; and H3pidc = 2-(3-pyridinyl)-1H-imidazole-4,5-dicarboxylic acid), were consciously manufacture and employed for heterogeneously catalyzed sulfide-sulfoxide transformation. Structural analysis shows that 1 and 2 exhibit similar porous frameworks with nearly identical two-dimensional metal-organic layers further pillared by tetradentate POM ligands with different coordination modes, which also result in the porosity of 1 being almost twice that of 2. In catalyzing the conversion of methyl phenyl sulfide (MPS) to methyl phenyl sulfoxide (MPSO), 1 can convert nearly 100% of MPS into MPSO within 30 min, while 2 achieved the similar results requires 50 min. The higher activity of 1 may be attributed to its larger channel that can provide more active sites and more efficient mass transfer process. Systematic structure-activity analyses and mechanistic studies revealed dual-reaction pathways driven by POM sites and metal sites assisted by the structural microenvironment.
The cooperative effect plays a significant role in understanding the intermolecular donor-acceptor interactions of hydrogen bonds (H-bonds, D-H···A). Here, using the coupled-cluster singles and doubles with perturbative triple excitations (CCSD(T)) method of high-precision ab initio calculations, we show that the intermolecular H-bonded systems with different D and A atoms reproduce the structural changes predicted by the well-known cooperative effect upon intermolecular compression. That is, with decreasing intermolecular distance, the D-H bond length first increases and then decreases, while the H···A distance decreases. On the contrary, when D and A are the same, as the intermolecular distance decreases, the D-H bond length decreases without increasing. This obvious difference means that the cooperative effect may not be generally characterized by intermolecular compression. Interestingly, further analyses of many intermolecular systems confirm that this failure has boundaries, i.e., cooperative systems at their respective equilibrium positions have a smaller core-valence bifurcation (CVB) index (< 0.022) and stronger binding energies (> 0.25 eV), showing a clear linear inverse relationship related to H-bond strength. These findings provide an important reference for the comprehensive understanding of H-bonds and its calculation methods.
Mesoporous silica hollow spheres with a homogenous and high content distribution of Fe and Co were synthesized by a facile one-pot hydrothermal process. The sub-nanometer bimetallic components inside the silica framework facilitate the stable fixation and the open accessibility to active sites. The co-doped Fe/Co in the spheres showed excellent peroxidase-like activity and much higher catalytic performance than their monometallic-supported spheres. The synergistic effect between Fe and Co promotes the continuous formation of functional radicals during the oxidation process and thus accelerates the reaction rate. When used for colorimetric detection of hydrogen peroxide (H2O2), the Fe/Co incorporated silica hollow spheres show the capability of detection of H2O2 in a wide range (10-250 µmol/L) and with the low detection limit of 0.012 ppm.
78Li2S-22P2S5 are sulfide electrolytes with high lithium-ion conductivity and wide electrochemical windows in the Li2S-P2S5 system, making them attractive solid electrolytes for ASSLBs. However, the role and potential of 78Li2S-22P2S5 solid electrolytes over a wide temperature range are still not fully understood. Therefore, we constructed solid-state batteries with NCM622 as the positive electrode and 78Li2S-22P2S5 glass-ceramics as the electrolyte to investigate in depth the differences in battery performance over a wide temperature range and their intrinsic mechanisms. The in-situ impedance and relaxation time distribution (DRT) demonstrated the electrochemical stability of the electrolyte over a wide temperature range, while the in-situ stacking pressure observed a large volume change during cycling at 60 ℃, leading to local solid-solid contact failure and poor cycling stability. This study provides insight into the advantages and problems of 78Li2S-22P2S5 in the wide temperature range as well as a basis for the construction of ASSLBs with high energy density and long cycle life.
Two triphenylamine-based star-type push-pull chromophores (T1, T2) were designed and synthesized. Triphenylamine serves as the central core and acts as an electron-donating group surrounded by electron-withdrawing pentafluorobenzene or N, N-dimethyl substituted tetrafluorobenzene, which are connected by ethylene bridges. Single-crystal X-ray diffraction confirmed the structures and molecular arrangement of two chromophores. The systematic photophysical research of T1 and T2 absorption characteristics was carried out to gain a better understanding of how structure-property relationships affect the observed nonlinear optical absorption phenomenon. Complementary calculations based on density functional theory (DFT) further confirmed the experimental results. Both chromophores exhibited excellent two-photon absorption (TPA) properties in CH2Cl2. Notably, T2 has more remarkable nonlinear optical absorption effects with the TPA cross-section up to 4.24 × 107 GM. By adjusting the electronic structures of the chromophores through introducing pentafluorobenzene or N, N-dimethyl as functional groups with different electron-donating or withdrawing behaviors, the TPA performance of the small organic molecule could be greatly enhanced. These molecular structures with push-pull systems were excellent candidates for different two-photon applications.
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