多组件学习器实现有机分子沸点的精准预测

沸点(BP)是有机分子液体的基本物理化学量, 也是化学工业生产中的重要参数. 有机分子的沸点由分子结构决定, 呈现复杂的结构-沸点关系, 函数法(Function Method)、基团贡献法(Group Contribution Method)等传统方法无法应对复杂多样有机分子结构的预测, 应用范围狭窄, 预测精度低. 本研究中, 我们利用基于人工神经网络(ANN)和支持向量机(SVM)的多组件学习器实现有机分子沸点的精准预测. 我们构建了基于可解释性描述符的ANN、基于相关性描述符的ANN及基于复合分子指纹的SVM三个异质模型, 并通过包含4550个各种类别的有机分子沸点的数据集进行训练得到了三个异质性学习器, 最后集成三个学习器对有机分子沸点进行预测. 相比于传统方法和此前的定量结构性质关系(QSPR)模型, 多组件模型结合了三种模型的优点, 展现出很好的预测精度和泛化能力以及低的过拟合, 实现了对多种类型有机分子的沸点的有效预测.     

基于ZIF-8/PAN复合薄膜的柔性丙酮气体传感器

ZIF-8是一种Zn基金属有机骨架材料, 可以吸附丙酮气体从而作为电容式丙酮传感器的气敏材料, 然而ZIF-8的传统使用形式为粉末态, 这导致其不能成为具备柔性的整体, 从而限制了传感器的柔性. 结合包埋种子和二次生长法将ZIF-8与纳米纤维结合成纤维型柔性材料, 并将其作为气敏层制备了柔性电容式丙酮气体传感器. 该传感器在9种常见挥发性有机化合物中表现出良好的选择性, 对250~2000 cm³/m³的丙酮气体具有灵敏的响应、良好的循环响应及长期稳定性. 值得注意的是该柔性传感器不仅在室温下进行传感, 而且在弯折180°的状态下对丙酮气体的响应值与不弯折(0°)状态下几乎一致, 在200次以内的180°弯折-恢复后同样表现出了传感性能的稳定, 表明了其在柔性传感器方面的潜力.     

石墨烯玻璃透明薄膜加热特性

Graphene has become a research focus in recent years owing to its excellent characteristics, and glass is a commonly used material with high transparency and low cost. Graphene glass combines the excellent properties of both graphene and glass; graphene glass has not only high thermal conductivity, high electrical conductivity, and good surface hydrophobicity but also exhibits superior electrothermal conversion and wide-spectrum high-light-transmittance characteristics. Therefore, the study of graphene glass films is of theoretical value and practical significance. In this study, a high-purity glass-based (JGS1 quartz glass) multilayer graphene film was developed based on an atmospheric-pressure chemical vapor deposition (APCVD) method, and its electrical characteristics, light transmittance, and electrical heating characteristics were experimentally investigated in detail. The results show that graphene glass with different surface resistance values obtained through direct growth on a high-purity quartz glass substrate using the APCVD method, not only has excellent uniformity and quality, but also has considerably flat and high transmittance across the entire visible light region and exhibits excellent heating performance and fast response time. For graphene glass with a surface resistance of 1500 Ω·sq^-1, the light transmittance can reach 74%, and the saturation temperature can rise to 185 ℃ by applying a bias voltage of 40 V. In addition, when the resistance value of the graphene glass is 420 Ω·sq^-1, the graphene glass reaches a high saturation temperature of 325 ℃ in 40 s, and the corresponding heating rate can exceed 18 ℃·s^-1, achieving a significantly higher heating rate than other heating films at the same voltage. Compared with the polyethylene-terephthalate- (PET-) based and silicon-based graphene films obtained by the transfer, graphene glass has a higher saturation temperature, shorter thermal response time, and faster heating rate. Furthermore, graphene glass exhibits better heating cycle stability and longer-term heating stability at a constant voltage. In addition, an experiment using the graphene glass to thermally tune the wavelength of a vertical-cavity surface-emitting laser was conducted and gave good results. The position of the laser peak controlled by the graphene glass was red-shifted by 1.78 nm by applying a voltage of 20 V, and the wavelength tuning efficiency reached 0.059 nm·℃^-1. Compared with PET-based and silicon-based graphene films, the actual electrical heating capacity of graphene glass increased by 195%. These experimental findings demonstrate that graphene glass transparent films with excellent electric heating characteristics can be used in various transparent electric heating fields and have relatively wide application prospects.     

Phosphorescent Bimetallic C^C* Platinum(ii) Complexes with Bridging Substituted Diphenylformamidinates

A series of phosphorescent bimetallic platinum(II) complexes is presented, which were synthesized by the combination of bidentate cyclometalated N-heterocyclic carbene ligands and different bridging diphenylformamidinates. The complexes were characterized by standard techniques and additionally two solid-state structures could be obtained. Photoluminescence measurements revealed the strong emissive behavior of the compounds with quantum yields of up to 90 % and emission lifetimes of approx. 2 μs. The effect of the substitution pattern in the bridging ligands on the structural and photophysical properties of the complexes was examined in detail and rationalized by density functional theory calculations (PBE0/6-311G*).     

[2+3] Amide Cages by Oxidation of [2+3] Imine Cages – Revisiting Molecular Hosts for Highly Efficient Nitrate Binding

The pollution of groundwater with nitrate is a serious issue because nitrate can cause several diseases such as methemoglobinemia or cancer. Therefore, selective removal of nitrate by efficient binding to supramolecular hosts is highly desired. Here we describe how to make [2+3] amide cages in very high to quantitative yields by applying an optimized Pinnick oxidation protocol for the conversion of corresponding imine cages. By NMR titration experiments of the eight different [2+3] amide cages with nitrate, chloride and hydrogen sulfate we identified one cage with an unprecedented high selectivity towards nitrate binding vs. chloride (S=705) or hydrogensulfate (S>13500) in CD₂Cl₂/CD₃CN (1 : 3). NMR experiments as well as single-crystal structure comparison of host-guest complexes give insight into structure-property-relationships.     

Phenylene-Bridged Perylene Monoimides as Acceptors for Organic Solar Cells: A Study on the Structure–Property Relationship

A series of non-fullerene acceptors based on perylene monoimides coupled in the peri position through phenylene linkers were synthesized via Suzuki-coupling reactions. Various substitution patterns were investigated using density functional theory (DFT) calculations in combination with experimental data to elucidate the geometry and their optical and electrochemical properties. Further investigations of the bulk properties with grazing incidence wide angle X-ray scattering (GIWAXS) gave insight into the stacking behavior of the acceptor thin films. Electrochemical and morphological properties correlate with the photovoltaic performance of devices with the polymeric donor PBDB-T and a maximum efficiency of 3.17 % was reached. The study gives detailed information about structure–property relationships of perylene-linker-perylene compounds.     

Flexible Alkylene Bridges as a Tool To Engineer Crystal Distyrylbenzene Structures Enabling Highly Fluorescent Monomeric Emission

To design ultrabright fluorescent solid dyes, a crystal engineering strategy that enables monomeric emission by blocking intermolecular electronic interactions is required. We introduced propylene moieties to distyrylbenzene (DSB) as bridges between the phenyl rings either side of its C=C bonds. The bridged DSB derivatives formed compact crystals that emit colors similar to those of the same molecules in dilute solution, with high quantum yields. The introduction of flexible seven-membered rings to the DSB core produced moderate distortion and steric hindrance in the DSB π-plane. However, owing to this strategy, it was possible to control the molecular arrangement with almost no decrease in the crystal density, and intermolecular electronic interactions were suppressed. The bridged DSB crystal structure differs from other DSB derivative structures; thus, bridging affords access to novel crystalline systems. This design strategy has important implications in many fields and is more effective than the conventional photofunctional molecular crystal design strategies.     

A Macrocyclic Furan with Accessible Oxidation States: Switching Between Aromatic and Antiaromatic Global Ring Currents

Macrocyclic furans are predicted to switch between global aromaticity and antiaromaticity, depending on their oxidation states. However, the macrocyclic furans reported to date are stabilized by electron withdrawing groups, which result in inaccessible oxidation states. To circumvent this problem, a post-macrocyclization approach was applied to introduce methylene-substituted macrocyclic furans, which display an extremely low oxidation potential of −0.23 vs. Fc/Fc⁺, and are partially oxidized in ambient conditions. Additional oxidation to the dication results in aromaticity switching to a global 30πe⁻ aromatic state, as indicated by the formation of a strong diatropic current observed in the ¹H NMR spectrum. NICS and ACID calculations support this trend and provide evidence for a different pathway for the global current in the neutral and dicationic states. According to these findings, macrocyclic furans can be rendered as promising p-type materials with stable oxidation states.     

卟啉-硫醚基共价有机框架材料用于氧还原反应电催化剂

氧还原反应（ORR）是能进行能量存储的核心电化学过程。由于它的动力学速率缓慢,因此亟需制备出高活性的电催化剂来促进这一反应的速率。二维共价有机框架材料（2D COFs）的π-π堆积结构可赋予骨架高导电率,并且一维有序的孔道有利于促进中间反应体传输。因此,其在可再生能源领域中具有良好的应用前景,并有望作为能量存储与转化的强大催化平台。本文通过向2D COFs中引入金属卟啉单元及硫醚单元成功制备了两个2D COFs （JUC-600和JUC-601）。通过多种表征手段证明,这两个2D COFs均具有AA堆积的sql拓扑结构。通过电化学测试表明,Co²⁺配位的JUC-601具有更正的ORR起始电势（0.825 V）和半波电势（0.7 V）、更高的活性表面积（7.8 mF/cm²）,更低的Tafel斜率（58 mV/dec）。这主要是由于JUC-601的高比表面积和高孔隙率使得中间产物能更易在COFs的表面和孔道中接触和传输。此外,Co²⁺-卟啉单元以及硫醚单元的存在使其骨架整体的电子结构发生了变化,更有利于电子转移。这一工作不仅开发了新的二维卟啉-硫醚基COFs材料,同时也拓展了2D COFs材料在电催化领域的应用。     

分散溶剂对PEMFC催化层中超薄Nafion离聚物质子传导的影响

质子交换膜燃料电池(PEMFC)商业化应用的瓶颈仍然是贵金属催化剂导致的成本问题。然而,目前对于催化层中纳米尺度全氟磺酸离聚物(以Nafion为代表)薄膜中质子传导的问题研究不足,无法完善三相界面的成型规律,进而指导催化层设计。在催化层浆料制备过程中,分散溶剂对Nafion的分散形态有直接影响,可能对催化层成型后附着在催化剂颗粒表面Nafion薄膜的微观结构有潜在影响,进而影响Nafion薄膜的质子传导能力。因此,在本文中利用分子自组装技术模拟催化层离聚物薄膜的聚集过程,于模型基底上制备厚度精确可控的纳米尺度Nafion薄膜,并通过微观测试表征技术探索并建立纳米尺度Nafion离聚物的微观结构模型,阐明分散溶剂对Nafion薄膜微观结构及质子传导的影响。研究发现Nafion薄膜在纳米尺度下的质子电导率比体相膜的质子电导率低一个数量级,使用介电常数较小的醇类溶剂可以使Nafion薄膜形成更有利于质子传导的微观结构,使Nafion薄膜的质子电导率得到提高。相关研究结果为优化PEMFC催化层结构,改善PEMFC催化层中质子传导问题提供给了依据。