无机盐-氧化物复合电解质导电机制

提高材料的电导率是固态离子学的一个重要研究目的．将某些离子导体与氧化物陶瓷结合起来构成复合电解质,在大多数情况下可提高材料的电导率．本文对这种陶瓷复合材料的各种导电机制和最新进展作了简要的综述．     

Mixed conduction in charge transfer materials based on aromatic diamines and iodine having different mole ratios

Mixed ionic and electronic conduction in charge transfer materials based on aromatic diamine electron donors (benzidine,o-tolidine (3,3′-dimethyl benzidine) andN,N′-diphenylbenzidine) with iodine in different mole ratios has been reported. The current-voltage and capacitance-voltage curves as a function of time and temperature have been obtained to determine the role of ionic conduction in electronic conductors based on charge transfer complexes. The compositional dependence of ionic transport numbers, diffusion parameters, ionic(σ _i) and electronic(σ _e) conductivities and thermal activation energies has been studied. Temperature and frequency dependence of AC impedance and related parameters have been studied to learn about the electrical conduction behaviour in these non-stoichiometric charge transfer materials. An electrochemical mechanism has been proposed to account for the ionic conduction in some of these complexes.     

Gated proton transport in aligned mesoporous silica films

Modulated proton transport plays significant roles in biological processes such as ATP synthesis as well as in technologically important applications including, for example, hydrogen fuel cells. The state-of-the-art proton-exchange membrane is the sulphonated tetrafluoroethylene copolymer Nafion developed by DuPont in the late 1960s, with a high proton conductivity. However, actively switchable proton conduction, a functional mimic of the ion transport within a cell membrane, has yet to be realized. Herein, we report the electrostatic gating of proton transport within aligned mesoporous silica thin film. It is observed that surface-charge-mediated transport is dominant at low proton concentrations. We have further demonstrated that the proton conduction can be actively modulated by two-fourfold with a gate voltage as low as 1 V. Such artificial gatable ion transport media could have potential applications in nanofluidic chemical processors, biomolecular separation and electrochemical energy conversion.     

Construction of nanostructures for selective lithium ion conduction using self-assembled molecular arrays in supramolecular solids

Abstract

In the development of innovative molecule-based materials, the identification of the structural features in supramolecular solids and the understanding of the correlation between structure and function are important factors. The author investigated the development of supramolecular solid electrolytes by constructing ion conduction paths using a supramolecular hierarchical structure in molecular crystals because the ion conduction path is an attractive key structure due to its ability to generate solid-state ion diffusivity. The obtained molecular crystals exhibited selective lithium ion diffusion via conduction paths consisting of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and small molecules such as ether or amine compounds. In the present review, the correlation between the crystal structure and ion conductivity of the obtained molecular crystals is addressed based on the systematic structural control of the ionic conduction paths through the modification of the component molecules. The relationship between the crystal structure and ion conductivity of the molecular crystals provides a guideline for the development of solid electrolytes based on supramolecular solids exhibiting rapid and selective lithium ion conduction.     

Differential Electrochemical Conductance Imaging at the Nanoscale

Electron transfer in proteins is essential in crucial biological processes. Although the fundamental aspects of biological electron transfer are well characterized, currently there are no experimental tools to determine the atomic‐scale electronic pathways in redox proteins, and thus to fully understand their outstanding efficiency and environmental adaptability. This knowledge is also required to design and optimize biomolecular electronic devices. In order to measure the local conductance of an electrode surface immersed in an electrolyte, this study builds upon the current–potential spectroscopic capacity of electrochemical scanning tunneling microscopy, by adding an alternating current modulation technique. With this setup, spatially resolved, differential electrochemical conductance images under bipotentiostatic control are recorded. Differential electrochemical conductance imaging allows visualizing the reversible oxidation of an iron electrode in borate buffer and individual azurin proteins immobilized on atomically flat gold surfaces. In particular, this method reveals submolecular regions with high conductance within the protein. The direct observation of nanoscale conduction pathways in redox proteins and complexes enables important advances in biochemistry and bionanotechnology.     

La0.5-xCexBa0.5CoO3化合物的磁性和输运特性

在La0.5Ba0.5CoO3中,系统研究了Ce对La的替代效应.Ce的掺入首先产生了电荷转移效应.材料高温磁化率测量表明,每个Ce原子向Co的3d壳层转移2.86个电子,结果随Ce掺入量增加,材料磁矩成线性下降.另外,随Ce含量增加,材料居里温度单调下降,这是由于稀土离子的尺寸效应.在所研究的温度范围内,所有材料的导电机理都属于极化子的变程跳跃导电.由于电荷转移效应,使材料电阻率随Ce掺入量增加而迅速加大.当La全部被Ce替代后,室温下材料的电阻率提高了五个数量级以上.     

Spin specific electron conduction through DNA oligomers

Spin-based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. Most of the development in spintronics is currently based on inorganic materials. Despite the fact that the magnetoresistance effect has been observed in organic materials, until now spin selectivity of organic based spintronics devices originated from an inorganic ferromagnetic electrode and was not determined by the organic molecules themselves. Here we show that conduction through double-stranded DNA oligomers is spin selective, demonstrating a true organic spin filter. The selectivity exceeds that of any known system at room temperature. The spin dependent resistivity indicates that the effect cannot result solely from the atomic spin-orbit coupling and must relate to a special property resulting from the chirality symmetry. The results may reflect on the importance of spin in determining electron transfer rates through biological systems.     

基于有机自组织的质子传导材料研究进展

分子可通过相分隔、静电和氢键等作用形成特定微观结构的自组织.氢键或磺酸基、味唑等官能团在有机材料中自组织后会形成空间连续分布的质子传递通道,通过Grutthuss机理或运载机理实现稳定的质子传导.基于不同的自组织及传导机理,有机质子传导体系可由共混物或单组分构建.评述了有机自组织在质子传导材料中的研究进展,并对双亲聚合...     

Ionic‐Liquid Doping Enables High Transconductance,Fast Response Time,and High Ion Sensitivity in Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) are highly attractive for applications ranging from circuit elements and neuromorphic devices to transducers for biological sensing, and the archetypal channel material is poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS. The operation of OECTs involves the doping and dedoping of a conjugated polymer due to ion intercalation under the application of a gate voltage. However, the challenge is the trade‐off in morphology for mixed conduction since good electronic charge transport requires a high degree of ordering among PEDOT chains, while efficient ion uptake and volumetric doping necessitates open and loose packing of the polymer chains. Ionic‐liquid‐doped PEDOT:PSS that overcomes this limitation is demonstrated. Ionic‐liquid‐doped OECTs show high transconductance, fast transient response, and high device stability over 3600 switching cycles. The OECTs are further capable of having good ion sensitivity and robust toward physical deformation. These findings pave the way for higher performance bioelectronics and flexible/wearable electronics.     

Probing Distinctive Electron Conduction in Multilayer Rhenium Disulfide

Charge carrier transport in multilayer van der Waals (vdW) materials, which comprise multiple conducting layers, is well described using Thomas–Fermi charge screening (λ_TF) and interlayer resistance (R_int). When both effects occur in carrier transport, a channel centroid migrates along the c‐axis according to a vertical electrostatic force, causing redistribution of the conduction centroid in a multilayer system, unlike a conventional bulk material. Thus far, numerous unique properties of vdW materials are discovered, but direct evidence for distinctive charge transport behavior in 2D layered materials is not demonstrated. Herein, the distinctive electron conduction features are reported in a multilayer rhenium disulfide (ReS₂), which provides decoupled vdW interaction between adjacent layers and much high interlayer resistivity in comparison with other transition‐metal dichalcogenides materials. The existence of two plateaus in its transconductance curve clearly reveals the relocation of conduction paths with respect to the top and bottom surfaces, which is rationalized by a theoretical resistor network model by accounting of λ_TF and R_int coupling. The effective tunneling distance probed via low‐frequency noise spectroscopy further supports the shift of electron conduction channel along the thickness of ReS₂.     

Analytical Prediction of Quench Energies of Cooled Superconductors Based on the Hyperbolic Heat Conduction Model

The critical energy characteristics of cooled composite superconductors is analytically predicted based on the one-dimensional hyperbolic heat conduction model. The temperature dependence of the Ohmic heat generation, the finite speed of heat transfer, and the finite duration and finite length of the thermal disturbances are taken into account in the present model. The critical energies are calculated using a model based on the analytical solution of the hyperbolic heat conduction equation by the Laplace transformation method. The computational model results show that the critical energy depends on the relaxation time and disturbance duration. It is found that the hyperbolic conduction model predicts a lower-critical energy as compared to the predictions of the parabolic heat conduction model.     

镧掺杂Sr0.4Ba0.6TiO3材料的导热性能

研究了不同镧掺杂浓度下Sr0.4Ba0.6TiO3材料的导热性能,研究镧元素对其导热性能的影响,得到了不同掺杂量下钛酸锶钡材料的热导率,材料密度随烧结温度与成型压力的增加而增大;同时发现少量镧元素的掺杂,可以增加钛酸锶钡材料的热导率;当镧元素掺杂量较大时,降低了材料的热导率.钛酸锶钡材料的电子热导率随材料烧结温度的升高基本不变,声子热导率随材料烧结温度的升高而增加.     

Rapid and precise scanning helium ion microscope milling of solid-state nanopores for biomolecule detection

We report the formation of solid-state nanopores using a scanning helium ion microscope. The fabrication process offers the advantage of high sample throughput along with fine control over nanopore dimensions, producing single pores with diameters below 4 nm. Electronic noise associated with ion transport through the resultant pores is found to be comparable with levels measured on devices made with the established technique of transmission electron microscope milling. We demonstrate the utility of our nanopores for biomolecular analysis by measuring the passage of double-strand DNA.     

Towards local electromechanical probing of cellular and biomolecular systems in a liquid environment

Electromechanical coupling is ubiquitous in biological systems, with examples ranging from simple piezoelectricity in calcified and connective tissues to voltage-gated ion channels, energy storage in mitochondria, and electromechanical activity in cardiac myocytes and outer hair cell stereocilia. Piezoresponse force microscopy (PFM) originally emerged as a technique to study electromechanical phenomena in ferroelectric materials, and in recent years has been employed to study a broad range of non-ferroelectric polar materials, including piezoelectric biomaterials. At the same time, the technique has been extended from ambient to liquid imaging on model ferroelectric systems. Here, we present results on local electromechanical probing of several model cellular and biomolecular systems, including insulin and lysozyme amyloid fibrils, breast adenocarcinoma cells, and bacteriorhodopsin in a liquid environment. The specific features of PFM operation in liquid are delineated and bottlenecks on the route towards nanometre-resolution electromechanical imaging of biological systems are identified.     

Coupled heat conduction and deformation in a viscoelastic composite cylinder

We study the coupled problem of deformation due to mechanical and thermal loading of a composite cylinder made up of two layers of linear isotropic viscoelastic materials. The effect of a time-varying temperature field due to unsteady heat conduction on the short term and long term material response is examined in terms of the stress, displacement, and strain fields. The material properties of the two layers of the composite cylinder at any given location and time are assumed to depend on the temperature at that location at that given instant of time. Sequentially coupled analyses of heat conduction and deformation of the viscoelastic composite cylinder are carried out. Analytical solutions for the stress, strain and displacement fields of the viscoelastic composite cylinder are obtained from the corresponding solution of the linear elasticity problem by applying the Correspondence Principle. We examine the discontinuity in the hoop stress and the radial strain at the interface of the two layers caused by mismatches in material properties, during transient heat conduction. We find that the discontinuities change over time as the mismatch in the moduli of the two layers changes due to the material properties which are time-dependent. We also investigate the effect of the thermal field on the time-dependent field variables in the composite body.     

粉末填料/聚合物导复电合材料的导电机理

综述了由粉末导电填料与聚合物母体配制而成的导电高分子材料的导电机理。此类材料导电机理异常复杂,目前主要有两种看法,即“导电通道”学说以及“隧道效应”学说或“电场发射”学说。     

In situ ion etching in a scanning electron microscope

A facility for ion etching in a scanning electron microscope is described which incorporates a new type of electrostatic ion source and viewing of the specimen is possible within about 30 sec after terminating the ion bombardment. Artefacts produced during etching have been studied and cone formation has been followed during its growth. The instrument has provided useful structural information on metals, alloys and sinters. However, although insulating materials, such as plastics, glass and resins, have been successfully etched, interpretation of the resultant micrographs is more difficult. Ion etching of soft biological tissues, such as the rat duodenum was found to be of considerable interest. The observed structural features arise from the selective intake of the heavy fixation elements by different parts of the tissue. Hard biological materials, such as dental tissues and restorative materials, have also been studied and the prismatic structure of the enamel and the form and distribution of the dentinal tubules have been revealed.     

Immunogold FIB‐SEM: Combining Volumetric Ultrastructure Visualization with 3D Biomolecular Analysis to Dissect Cell–Environment Interactions

Volumetric imaging techniques capable of correlating structural and functional information with nanoscale resolution are necessary to broaden the insight into cellular processes within complex biological systems. The recent emergence of focused ion beam scanning electron microscopy (FIB‐SEM) has provided unparalleled insight through the volumetric investigation of ultrastructure; however, it does not provide biomolecular information at equivalent resolution. Here, immunogold FIB‐SEM, which combines antigen labeling with in situ FIB‐SEM imaging, is developed in order to spatially map ultrastructural and biomolecular information simultaneously. This method is applied to investigate two different cell–material systems: the localization of histone epigenetic modifications in neural stem cells cultured on microstructured substrates and the distribution of nuclear pore complexes in myoblasts differentiated on a soft hydrogel surface. Immunogold FIB‐SEM offers the potential for broad applicability to correlate structure and function with nanoscale resolution when addressing questions across cell biology, biomaterials, and regenerative medicine.     

Self-chemisorption of azurin on functionalized oxide surfaces for the implementation of biomolecular devices

In this work, we investigate the formation of redox protein Azurin (Az) monolayers on functionalized oxygen exposing surfaces. These metallo-proteins mediate electron transfer in the denitrifying chain of Pseudomonas bacteria and exhibit self-assembly properties, therefore they are good candidates for bio-electronic applications. Azurin monolayers are self-assembled onto silane functionalized surfaces and characterized by atomic force microscopy (AFM). We show also that a biomolecular field effect transistor (FET) in the solid state can be implemented by interconnecting an Azurin monolayer immobilized on SiO₂ with two gold nanoelectrodes. Transport experiments, carried out at room temperature and ambient pressure, show FET behavior with conduction modulated by the gate potential.     

TiO2光催化中价电子的转移过程及其作用

简要分析了二氧化钛光催化中价电子转移过程,即价电子跃迁和电子空穴复合过程,指出价电子转移过程的变化必然引起TiO2光催化效率的变化,重点说明了改变电子受体的种类、半导体表面改性、重金属表面改性、阴离子掺杂和金属离子掺杂等方法的具体原理,进一步探讨了价电子转移过程同光催化效率之间的关系.