MLIMC: Machine Learning-Based Implicit-Solvent Monte Carlo

Monte Carlo (MC) methods are important computational tools for molecular structure optimizations and predictions. When solvent effects are explicitly considered, MC methods become very expensive due to the large degree of freedom associated with the water molecules and mobile ions. Alternatively implicit-solvent MC can largely reduce the computational cost by applying a mean field approximation to solvent effects and meanwhile maintains the atomic detail of the target molecule. The two most popular implicit-solvent models are the Poisson-Boltzmann (PB) model and the Generalized Born (GB) model in a way such that the GB model is an approximation to the PB model but is much faster in simulation time. In this work, we develop a machine learning-based implicit-solvent Monte Carlo (MLIMC) method by combining the advantages of both implicit solvent models in accuracy and efficiency. Specifically, the MLIMC method uses a fast and accurate PB-based machine learning (PBML) scheme to compute the electrostatic solvation free energy at each step. We validate our MLIMC method by using a benzene-water system and a protein-water system. We show that the proposed MLIMC method has great advantages in speed and accuracy for molecular structure optimization and prediction.     

Dynamic Variation of Excitonic Coupling in Excited Bilayer Graphene Quantum Dots?

The intermolecular interaction determines the photophysical properties of the organic aggregates, which are critical to the performance of organic photovoltaics. Here, excitonic coupling, an important intermolecular interaction in organic aggregates, between the π-stacking graphene quantum dots is studied by using transient absorption spectroscopy. We find that the spectral evolution of the ground state bleach arises from the dynamic variation of the excitonic coupling in the excited π-stacks. According to the spectral simulations, we demonstrate that the kinetics of the vibronic peak can be exploited as a probe to measure the dynamics of excitonic coupling in the excited π-stacks.     

亚表面引发原子转移自由基聚合构筑温度响应型纳米纤维油水分离膜

亚表面引发聚合是一种用于制备共价嵌入型聚合物刷的新型改性策略.该方法在发展高稳定性聚合物刷功能化表界面材料方面具有显著的优势.本工作利用亚表面引发原子转移自由基聚合(sSI-ATRP)对静电纺丝聚丙烯腈(PAN)基纳米纤维膜进行亚表面改性,通过接枝聚N-异丙基丙烯酰胺(PNIPAM)制备了温度响应型纳米纤维油水分离膜(...     

原位限域生长策略制备有序介孔碳负载的超小MoO3纳米颗粒

采用原位限域生长策略制备了一系列有序介孔碳负载的超小MoO₃纳米颗粒复合物(OMC-US-MoO₃). 其中, 有序介孔碳被用作基质来原位限域MoO₃纳米晶的生长. 依此方法制备的MoO₃纳米晶具有超小的晶粒尺寸(<5 nm), 并在介孔碳骨架内具有良好的分散度. 制得的OMC-US-MoO₃复合物具有可调的比表面积(428~796 m²/g)、 孔容(0.27~0.62 cm³/g)、 MoO₃质量分数(4%~27%)和孔径(4.6~5.7 nm). 当MoO₃纳米晶的质量分数为7%时, 所得样品OMC-US-MoO₃-7具有最大的孔径、 最小的孔壁厚度和最规整的介观结构. 该样品作为催化剂时, 表现出优异的环辛烯选择性氧化性能.     

锂嵌入型化合物-氢气电池

可充电氢气电池作为一种新兴的电池体系在大规模能源储存领域显示出富有前景的电化学性能. 锂嵌入型化合物作为一大类的锂离子电池正极材料能够很好地用作可充电氢气电池的正极. 本文开发了 2种新型锂嵌入型化合物-氢气电池. 通过使用钴酸锂与磷酸铁锂2种正极材料分别与氢气负极在硫酸锂 水系电解液中进行匹配, 得到了钴酸锂-氢气电池与磷酸铁锂-氢气电池. 钴酸锂-氢气电池展现出约1.27 V 的放电电位, 约97 mA·h·g^-1的比容量及10C的高倍率; 磷酸铁锂-氢气电池展现出约0.66 V的放电电位, 约125 mA·h·g^-1的比容量以及10C的高倍率. 虽然, 钴酸锂-氢气电池和磷酸铁锂-氢气电池因为使用了未经优化的、 不稳定的锂嵌入型化合物正极材料而导致全电池容量衰减, 但这2种电池经过氢气负极的再循环利用均表现出优异的恢复能力. 本文结果证明了氢气电池的化学稳定性及其在未来长寿命电池中具有的大规模能源储存潜力.     

金刚石纳米线氮空位色心的表面与尺寸效应

使用大规模自旋极化密度泛函理论计算研究了表面修饰和尺寸对金刚石纳米线(DNs)中氮空位(NV)色心的几何结构、 电子结构、 磁性和稳定性的影响. 理论上设计了几种不同的DNs, 这些DNs具有不同的表面修饰(干净、 氢化和氟化), 并且直径达数百个原子. 实验结果证明, 中性(NV⁰)和带1个负电荷(NV^-)的NV色心的电子结构不受半导体表面修饰和DNs直径大小的影响, 但NV色心的稳定性对这两个因素具有不同的响应. 此外, 研究中还发现, 由于DNs中存在圆柱形表面电偶极子层, 对DNs中掺杂的NV^-色心的稳定性, 表面改性诱导了不依赖尺寸的长程效应. 特别地, 对于n型氟化金刚石表面, 掺杂在DN中的NV^-色心可以稳定存在, 而对于p型氢化表面, NV⁰则相对更稳定. 因此, 表面修饰为控制金刚石纳米线中的NV色心的电子结构和稳定性提供了一种精确有效的调控方法.     

Facile preparation of MgAl2O4/CeO2/Mn3O4 heterojunction photocatalyst and enhanced photocatalytic activity

Novel Mn₃O₄-promoted double p?n junction MgAl₂O₄/CeO₂/Mn₃O₄ heterojunction photocatalyst was constructed by one-step synthesis method and two-step synthesis method. The X-ray powder diffraction, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, optical and photoluminescence demonstrated that the MgAl₂O₄/CeO₂/Mn₃O₄ heterojunction photocatalyst was synthesized by the two-step synthesis method comprehends a high crystallinity, charge carrier migration and separation efficiency, and relatively low optical absorption coefficient. The MgAl₂O₄/CeO₂/Mn₃O₄ heterojunction photocatalysts were efficiently used as simulated sunlight-driven n-n and p-n double junction photocatalyst for the simultaneous degradation of methylene blue (MB) dye. The continuous double p?n junction MgAl₂O₄/CeO₂/Mn₃O₄ heterojunctions strengthened the function of single n-n or p-n junction and guided the charge carrier migration and separation direction; thus, the oxidation and reduction reactions occur at the active site of spatial separation and prevent the recombination of electrons and holes. The results suggest that the continuous double p?n junction MgAl₂O₄/CeO₂/Mn₃O₄ heterojunctions are very promising candidate material for enhancing the photocatalytic activity in the photocatalytic degradation of MB dye.     

Selection of hydrogel electrolytes for flexible zinc–air batteries

Flexible zinc–air batteries attract more attention due to their high energy density, safety, environmental protection, and low cost. However, the traditional aqueous electrolyte has the disadvantages of leakage and water evaporation, which cannot meet application demand of flexible zinc–air batteries. Hydrogels possessing good conductivity and mechanical properties become a candidate as the electrolytes of flexible zinc–air batteries. In this work, advances in aspects of conductivity, mechanical toughness, environmental adaptability, and interfacial compatibility of hydrogel electrolytes for flexible zinc–air batteries are investigated. First, the additives to improve conductivity of hydrogel electrolytes are summarized. Second, the measures to enhance the mechanical properties of hydrogels are taken by way of structure optimization and composition modification. Third, the environmental adaptability of hydrogel electrolytes is listed in terms of temperature, humidity, and air composition. Fourth, the compatibility of electrolyte–electrode interface is discussed from physical properties of hydrogels. Finally, the prospect for development and application of hydrogels is put forward.     

Au@ZIF-8核壳结构中金纳米粒子分布的调控及其在荧光分子光致发光传感中的应用

控制金属@MOF核壳纳米结构中金属纳米粒子的分布不容易实现。我们应用了合成MOF胶体粒子所用到的配位调制方法来合成Au@ZIF-8核壳纳米结构。通过使用过量的2-甲基咪唑和不同用量的1-甲基咪唑可获得不同的Au@ZIF-8。该合成方法可在ZIF-8纳米晶体中灵活调整Au纳米粒子（Au NPs）的分布。此外,我们分别研究了2种不同尺寸的荧光分子与Au@ZIF-8结合后的光致发光光谱和寿命。ZIF-8的孔径可以决定这2种分子是否可通过多孔壳结构接近Au NPs。分子光学特性对Au NPs近场的发光增强和荧光猝灭的竞争非常敏感。     

Two New 3D Metal-Organic Frameworks Constructed by Polycarboxylate and N-Donor Ligands: Crystal Structure,Photocatalytic Performances,and DFT Calculation

Russian Journal of Coordination Chemistry - Two new metal-organic frameworks, [Zn(Bdc)(Bip)?H2O] (I) and {[Cd2(Btc)2(H2O)2](H2Bib)· 6H2O} (II) (H2Bdc = 1,3-benzenedicarboxylic acid,...