基于镓铟合金电极的单分子层电输运研究进展

有机分子层的电输运特性是分子电子学研究的重要问题.镓铟合金电极技术具有成结率高、可靠性好及操作简便等优点,近年来已成为测量单分子层电输运的常用表征手段.本文介绍了镓铟合金电极技术的基本原理及测试方法,综述了该技术所带来的一些前沿成果,并对其目前存在的优势、缺点及未来发展前景进行了分析.     

有序分子组装膜电极非理想伏安图的理论研究

在有序分子组装体系的电化学研究中,电活性物种间的相互作用直接导致其偏离理想的电化学行为,譬如出现双峰或者峰展宽的现象。从这些非理想的电化学数据中提取热力学和动力学数据显得相对困难,因而了解和评价这些非理想的电化学行为显得十分有必要。本文着重就这些非理想电化学现象的理论模型、基本公式和微观认识进行了评述。理解这些非理性电化学的影响因素,不仅加深对表面电化学体系的认识,更对现在的研究热点课题如主客体识别、分子电子器件、生物传感器等具有重要意义。     

DFT法研究HCOOH在Pd/WC(0001)上的分解机理（英文）

作为便携式电子设备的动力源,直接甲酸燃料电池(DFAFC)具有燃料跨界范围小、电动势大、甲酸无毒、低温下功率密度大等优点,因而引起了人们的极大兴趣.DFAFC商业化的主要挑战之一是阳极电催化剂材料的高成本和低CO耐受性.阳极通常需要高负载的贵金属电催化剂(Pt或Pd)氧化甲酸(HCOOH)以获得所需的电能.完全电氧化甲酸在Pt和Pd表面上会产生强吸附的CO,从而降低了Pt或Pd催化剂的活性.Pt和Pd储量少且价格昂贵,减少Pt和Pd含量且保持催化性能的燃料电池催化剂一直是研究者的奋斗目标.本文用周期性密度泛函理论(DFT)系统地研究了WC负载的单分子层Pd(Pd/WC(0001))催化剂对甲酸的分解机理,这可为所需的反应路径设计、筛选催化剂提供指导.Trans-HCOOH通过C–H, O–H, C–O键的活化发生分解.关于吸附,确定了可能反应中间体的最稳定吸附构型.trans-HCOOH, HCOO, mHCOO, cis-COOH, trans-COOH, CO, H₂O, OH和H的吸附过程是化学吸附,而cis-HCOOH和CO₂与Pd/...     

Dzyaloshinskii–Moriya Interaction of Cr2O2ClI Janus Monolayer: A First-Principles Calculation

The Dzyaloshinskii–Moriya interactions (DMIs) of Cr₂O₂ClI Janus monolayer are investigated using the first-principles calculations. There are three DMI mechanisms (namely, the Half–Fert–Levy mechanism, the Fert–Levy mechanism, and the Rashba mechanism) in Cr₂O₂ClI Janus monolayer. The Half–Fert–Levy mechanism, by which the I atoms enhance the spin orbit coupling interaction on the type-I Cr atoms but have no such effect on the type-II Cr atoms, contributes to the y-component of the DMI vector between two nearest-neighbor Cr atoms. Originating from the strong spin orbit coupling interaction of the I atoms, the Fert–Levy mechanism results in a significant DMI vector via the Cr–I–Cr exchange path between two type-I next-nearest-neighbor Cr atoms. Induced by the intrinsic electric field of the Janus structure, the Rashba mechanism results in nonzero in-plane components of the DMI vectors. This work provides the first-principles calculations of the DMIs of Cr₂O₂ClI Janus monolayer and reveals insight into the physics behind the calculated DMIs, which promote the understanding of the complicated DMIs due to multiple mechanisms in 2D magnetic Janus monolayers.     

二维半导体中的能谷电子学

文章介绍了能谷电子学背后的基本物理原理,并回顾了此方向在材料实现上的进展。在理论背景部分简单回顾了基本模型和有关贝里曲率导致量子输运和光选择的重要概念,在材料实现部分除了总结在真实材料中重要的实验和理论的发现,也讨论了在这些材料中的自旋轨道耦合和近邻诱导的塞曼效应,最后展望了能谷电子学的发展前景。     

水溶性金单层包覆团簇的制备与光学性能分析

采用硼氢化钠在水溶液中还原氯金酸,并以水溶性硫醇巯基丁二酸在生成的金核表面包覆单分子层的方法,制备了单层包覆金团簇（MPC）。傅里叶变换红外光谱仪结果表明,巯基丁二酸与金形成了Au－S键,并得到了Auzx(SR)y形式的MPC。TEM照片显示,当Au和S的物质的量的比为1∶3时,金MPC的核尺寸约为2 nm。探讨了制得的金MPC的紫外-可见吸收特性及荧光特性,发现金MPC水溶液在520 nm附近无紫外吸收现象,而在451及480 nm波长紫外光激发下,可在796 nm附近观察到明显的荧光现象。反映表面等离子基元共振的520 nm附近吸收峰的消失是量子尺寸效应作用的结果。荧光现象与金MPC表面全充满的5d10和6(sp)1导带间的带间跃迁有关。     

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.     

Constructing Atomic Fe and N Co-doped Hollow Carbon Nanospheres with a Polymer Encapsulation Strategy for High-Performance Lithium-Sulfur Batteries with Accelerated Polysulfide Conversion

As competitive next-generation rechargeable batteries, lithium-sulfur batteries (LSBs) suffer from the shuttle effect and the sluggish kinetics of intermediate polysulfides during charge and discharge processes, adversely affecting their electrochemical performances and actual applications. Herein, we demonstrate a polymer encapsulation strategy to synthesize atomic Fe and N co-doped hollow carbon nanospheres (Fe−NHC) with Fe−N_x sites for modifying commercial PP separator of LSBs to suppress the shuttle effect and promote the kinetics of intermediate polysulfides. Benefiting from the excellent structural design, the doped-N with positive charges could effectively adsorb negatively charged soluble polysulfides, help attract the soluble polysulfides to the Fe atoms and boost the catalytic transformation of the soluble polysulfides. Additionally, such a thin carbon shell could provide a short mass diffusion pathway and hence promote the adsorption and the catalytic conversion. Therefore, the battery with the Fe−NHC/PP separator delivers outstanding cycling and rate performances. At the large current density of 1 C, the specific capacity is 1079 mA h g⁻¹ and maintains a low loss of 0.076 % per cycle within 500 cycles. Even at a harsh current density of 4 C, a high capacity of 824 mA h g⁻¹ is still achieved, indicating the advantage of the Fe−NHC/PP separator in LSBs.     

Structures of Peptidic H‐wires at Mercury Surface: Molecular Dynamics Study

Biopolymer immobilization strategies, self‐assembly systems and adsorption phenomenon in general are crucial for the development of methods that work on the basis of the surface‐detection principle, including electrochemistry. A mechanistic view into the interaction of biopolymers with electrode surfaces is also important for studying fundamental and dynamic processes such as electron/proton transport. In this sense, the utilization of new approaches for investigating the interfacial behavior of immobilized biomolecular architectures is a permanent focus. Here we use a molecular dynamics (MD) approach to simulate the structural changes and metallic surface interactions of a model 21‐mer peptide of His (H) and Ala (A), A₃(HA₂)₆, a peptidic proton wire (H‐wire). This H‐wire was previously proposed for the electrochemical study of proton transfer at mercury electrodes (Langmuir, 2018, 34, 6997). The rigid solid mercury mono‐atomic layer (α‐mercury lattice model) was used systematically in all our simulations. The calculations were performed in a simulation box with 1, 16 and 32 H‐wire strands attached covalently to the mercury layer via the thiol group of a cysteinamide residue appended to the H‐wire C‐terminus. The internal alpha‐helical configuration of H‐wires was maintained by the presence of 2,2,2‐trifluoroethanol. It was shown that both the surface density of H‐wires and the protonation state of His residues play a decisive role in the structural stability and orientation of the peptide to the surface, whereas the applied voltage only has a mild effect on it, especially in case of 16 and 32 H‐wire strand configurations. The MD simulations presented here could be used for the further investigation of other peptides at metallic surfaces and for electrochemical analyses of structural changes of surface‐attached peptides that depend on their protonation states and other external factors.     

Simultaneous Occurrence of Nanospheres and Nanofibers Self-Assembled from Achiral Tripeptides

The achiral tripeptide Boc-Aib-MABA-Aib-OMe has the ability to co-exist as nanospheres and as a network of nanofibers in methanol. Furthermore, AFM and TEM images show the presence of bulges in the network of nanofibers. Interestingly, the formation of nanofibers is seen to emerge from the outer boundary of the spherical structures. Some of the nanofibers curl up at the tip and later result in the formation of hollow nanospheres with thick boundaries. The presence of β-turn-like structures with hydrogen bonding is observed using FT-IR studies. The presence of hydrogen bonding is also demonstrated by using NMR studies.