Conduction Channel Research Articles

Extracting connectivity paths in digital core images using solution of partial minimum eigenvalue problem

Abstract We show theoretically and numerically that the lowest non-trivial eigenvector function for a specific eigenproblem has almost constant values in high conductivity channels, which are different in separate channels. Therefore, based on these distinct values, all separate connected clusters of open pores can be identified in digital cores.

Structural Inhomogeneities and Nonlinear Phenomena in Charge Transfer under Cold Field Emission in Individual Closed Carbon Nanotubes

The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the I-V characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the I-V characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim (F-N) function by one to three orders of magnitude. The I-V characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the I-V characteristics have distinct regions of negative differential conductivity.

Thickness-Dependent Charge Transport in Three Dimensional Ru(II)- Tris(phenanthroline)-Based Molecular Assemblies.

We describe here the fabrication of large-area molecular junctions with a configuration of ITO/[Ru(Phen)3]/Al to understand temperature- and thickness-dependent charge transport phenomena. Thanks to the electrochemical technique, thin layers of electroactive ruthenium(II)-tris(phenanthroline) [Ru(Phen)3] with thicknesses of 4-16 nm are covalently grown on sputtering-deposited patterned ITO electrodes. The bias-induced molecular junctions exhibit symmetric current-voltage (j-V) curves, demonstrating highly efficient long-range charge transport and weak attenuation with increased molecular film thickness (β = 0.70 to 0.79 nm-1). Such a lower β value is attributed to the accessibility of Ru(Phen)3 molecular conduction channels to Fermi levels of both the electrodes and a strong electronic coupling at ITO-molecules interfaces. The thinner junctions (d = 3.9 nm) follow charge transport via resonant tunneling, while the thicker junctions (d = 10-16 nm) follow thermally activated (activation energy, Ea ∼ 43 meV) Poole-Frenkel charge conduction, showing a clear "molecular signature" in the nanometric junctions.

Construction of ammonium polyphosphate-modified halloysite nanotubes on phase change material microcapsules for the enhancement of thermophysical performance and flame retardant properties

Organic microencapsulated phase change materials (MPCMs) are regarded as promising for building energy efficiency while the low thermal conductivity and flammability limit their further application. Aiming at improving the thermal response performance and flame retardancy of the MPCMs, the MPCMs embedded by ammonium polyphosphate-modified halloysite nanotubes (a-HNTs) are developed and then applied in the epoxy resin (EP) coatings. Herein, the ammonium polyphosphate (APP) is grafted onto HNTs as a flame retardant for the first time and the resultant nanotubes are successfully embedded into the shell of traditional MPCMs. As a result, the obtained microcapsules (a-MPCMs) possess a regular spherical morphology and the desired chemical composition. Moreover, the a-HNTs with their unique inorganic tubular structure connect the inside and outside of the original polymethylmethacrylate (PMMA) shell and act as the thermally conductive channel, which greatly facilitates the conversion of external heat to the latent heat of the capric acid (CA) core. The phase change data show that the embedding of a-HNTs has little effect on the encapsulation efficiency of MPCMs, and the latent heat of a-MPCMs is 118.3 J/g. Meanwhile, the a-HNTs/PMMA hybrid shell also significantly improves the thermal stability of MPCMs with the highest residual weight of 24.3%. With the addition of a-MPCMs, the resultant temperature-control coatings (a-MPCMs/EP) hold a high thermal cycle stability and excellent temperature control performance with less temperature fluctuation. In addition, a-HNTs also provide superior flame retardant properties for a-MPCMs/EP. Compared to the EP composites with the same mass fraction of pristine MPCMs added (MPCMs/EP), the pHRR and THR of a-MPCMs/EP are reduced by 30.2% and 4.5%, respectively. Through flame retardant modification of HNTs and incorporating them into the shell material of MPCMs, this work provides a promising approach to the development of multifunctional MPCMs with enhanced thermophysical performance and flame retardant properties.

Replacing Tunnel Junctions in InP with Conduction Channels with GaP Crystallites

Replacing Tunnel Junctions in InP with Conduction Channels with GaP Crystallites

The influence of second-order effect on circuit design

The purpose of this paper is to deeply study and understand the influence of second-order effects (channel length modulation effect, bulk effect, subthreshold conductivity short channel effect) on the performance of electronic devices and circuits, and to propose effective methods and techniques to reduce their negative effects. The author will pay attention to the mechanism and characteristics of channel length modulation effect, bulk effect, subthreshold conductivity and short channel effect, and the key factors leading to their changes. Through theoretical analysis, process inversion and simulation, various effective suppression or compensation strategies are explored to improve the performance of electronic devices and circuits and enhance their reliability and stability. Through the in-depth study of the second-order effect, readers can better understand and solve the influence brought by the second-order effect.

Remarkable chemical adsorption and catalysis of monodisperse metallic cobalt sulfide nanoparticles enable long-cycling Li–S battery with high areal capacity and low shuttle constant

High-energy density lithium-sulfur battery is considered as one of the most potential new-generation energy-storage technologies. Nevertheless, the capacity decays rapidly due to severe volumetric change of sulfur, dissolution and slow redox kinetics of intermediate polysulfides, and instability of lithium anode. Herein, a novel highly conductive porous sulfur cathode host composed of graphene aerogel and polar Co9S8 nanoparticle is designed to address these obstacles. The porous conductive framework not only provides channels for rapid conduction of electron and lithium ion, but also provides adequate space to physically confine the lithium polysulfides and accommodate the volume expansion. Both experimental and theoretical calculations demonstrate that the in-situ uniformly deposited Co9S8 nanoparticles can effectively bind polar lithium polysulfides and catalyze their interconversion, and the shuttle effect is therefore effectively suppressed. The Co9S8-GA/S cathode exhibits high specific discharge capacity (1219.1 mAh g−1) and high areal specific capacity (14.3 mAh m−2) at 0.1 C, low shuttle constant (0.15 h−1), excellent rate performance (625.6 mAh g−1/7.4 mAh m−2 at 5 C), outstanding long cyclic stability (low decay of 0.024 %/cycle during 1000 cycles at 2 C). This study demonstrates a promising aerogel strategy to design high-performance composite cathode for lithium-sulfur battery.

Sodium carboxymethylcellulose/MXene/zeolite imidazolium framework-67-derived 3D porous carbon aerogel for high-performance asymmetric supercapacitors

Herein, we propose a carbon/TiO2/Co3O4 (CTC) composite carbon aerogel with a 3D porous conductive network structure derived from sodium carboxymethylcellulose (CMC)/Mxene (Ti3C2Tx)/zeolite imidazolium framework-67 (ZIF-67). Among them, CMC is used as the carbon skeleton, which can reduce the powdering caused by volume change and improve the cycle stability. Ti3C2Tx acts as the conductive agent and dispersant for ZIF-67, exposing more reactive sites while constructing fast conductive channels to enhance electrochemical performance. The microstructure of the CTC carbon aerogel is modulated by controlling the mass ratio of Ti3C2Tx to ZIF-67, and the carbon aerogel with a mass ratio of 2:3 (CTC-2:3) is experimentally demonstrated to have the best electrochemical performance. The CTC-2:3 electrode exhibits a high specific capacitance of 481.7 F g−1 at 1 A g−1 and possesses a rate performance of 78.9 % at 10 A g−1. The assembled asymmetric supercapacitor (ASC, CTC-2:3//Ti3C2Tx) delivers an energy density of 48.4 Wh kg−1 at a power density of 699.8 W kg−1. Moreover, the ASC device maintains 85.3 % initial capacitance and 99.1 % coulombic efficiency after 10,000 GCD cycles, indicating good cycling stability. This facile design pathway provides a new insight for the development of high-performance electrode materials.

Membrane Protein Structures in Native Cellular Membranes Revealed by Solid-State NMR Spectroscopy.

The structural characterization of membrane proteins within the cellular membrane environment is critical for understanding the molecular mechanism in their native functional context. However, conducting residue site-specific structural analysis of membrane proteins in native membranes by solid-state NMR faces challenges due to poor spectral sensitivity and serious interference from background protein signals. In this study, we present a new protocol that combines various strategies for cellular membrane sample preparations, enabling us to reveal the secondary structure of the mechanosensitive channel of large conductance from Methanosarcina acetivorans (MaMscL) in Escherichia coli inner membranes. Our findings demonstrate the feasibility of achieving complete resonance assignments and the potential for determining the 3D structures of membrane proteins within cellular membranes. We find that the use of the BL21(DE3) strain in this protocol is crucial for effectively suppressing background protein labeling without compromising the sensitivity of the target protein. Furthermore, our data reveal that the structures of different proteins exhibit varying degrees of sensitivity to the membrane environment. These results underscore the significance of studying membrane proteins within their native cellular membranes when performing structural characterizations. Overall, this study opens up a new avenue for achieving the atomic-resolution structural characterization of membrane proteins within their native cellular membranes, providing valuable insights into the nativeness of membrane proteins.

High performance quaternary ammonium-functionalized polybenzoxazine-based anion exchange membranes

Two kinds of benzoxazine monomers were synthesized by Mannich reaction with N,N-dimethyl-p-phenylenediamine and N,N-dimethylethylenediamine using polyformaldehyde, 4,4′-dihydroxydiphenylmethane as raw materials. Subsequently, quaternary ammonium functionalization was realized by Menshutkin reaction. The aromatic amine-based quaternary ammonium-functionalized polybenzoxazine (AQPBZ) and aliphatic amine-based quaternary ammonium-functionalized polybenzoxazine (LQPBZ) were synthesized by ring-opening polymerization. Polybenzoxazine anion exchange membrane (AEM) was prepared by solution casting method. The AQPBZ and LQPBZ AEMs exhibit micro-phase separated morphology clearly. LQPBZ AEM displays more large ion clusters and ion conductive channels due to the flexible alkyl connection between QA group and polybenzoxazine skeleton. AQPBZ and LQPBZ AEMs have the ionic conductivity of 75.5 mS/cm and 86.3 mS/cm at 80 °C and 100% relative humidity, respectively. AQPBZ and LQPBZ AEMs show excellent alkaline stability. After treated with 6 M sodium hydroxide solution at 80 °C for 240 h, they manitained the 49.8 mS/cm and 50.2 mS/cm, respectively. They also exhibit good oxidation stability and thermal stability. Their oxidation weight losses are 4.1% and 7.2% through Fenton test, respectively. Their Td5s are 325 °C and 289 °C, respectively.

Activation mechanisms of recombination processes in irradiated poly(arylenephthalides)

The recombination of separated ion-radical states (SIRS) in poly(arylenephthalide) (PAPh) films accompanied by emission of light with a maximum of ∼ 500 nm has been analyzed. The density functional theory methods [PBE1PBE/6-311+G(d,p)] and mathematical modeling were used for description of thermally stimulated luminescence (TSL) kinetics of PAPh. The versatility of the earlier proposed three-step kinetic model of metastable (X) and labile (Y) SIRS recombination was demonstrated on the example of various cardo polymers. The contribution of X-SIRS recombination to total luminescence was found to be characterized by the vanishingly small intensity in a vacuum and moderate and maximum one in inert gases and an oxygen-containing medium, respectively. It was found out that the recombination of labile SIRS does not depend on the nature of the atmosphere. It was theoretically substantiated that SIRS recombination can proceed via the transfer of both positive and negative charges. It was shown that the key factor determining the efficiency of thermal activation of recombination processes is the ratio of radiant and conductive channels of energy transfer from the heating element to the polymer sample.

Highly flexible multilayer MXene hollow carbon nanofibers confined with Fe3C particles for high-performance lithium-ion batteries

Designing electrode structures with excellent mechanical properties, fast electrochemical kinetics and stability is important for the development of flexible wearable electrodes. In this paper, a hollow carbon nanofiber composite of Ti3C2Tx MXene and Fe3C nanoparticles is designed. The synergistic effect of Ti3C2Tx MXene and Fe3C nanoparticles forms a strong conductive channel with the hollow channel to form a dual conductive channel, which plays an important role in the preparation of high-performance lithium-ion batteries. Benefiting from the advantages of the above structure, the Fe3C@MXene/hollow multichannel carbon fibers (Fe3C@MXene/HMCFs) electrodes at a current density of 0.2 A/g achieve an initial capacity of 1294 mA h g−1 and a high reversible capacity of 831 mA h g−1 after 200 turns of charge/discharge cycles.

Synaptic devices based on organic ferroelectric memtransistor with arithmetic calculating and logic functions

The bionic features offered by memory device are being actively explored. However, two-terminal memristors exhibit variability and limited capacity due to their inherent single presynaptic input scheme. Compared with the two-terminal memristor, the memtransistor can realize the modulation of conductive channel through the synergistic effect of gate, which enables the multifunctional modulation. Here, based on Schottky barrier tuning at metal-semiconductor interfaces by means of ferroelectric domain switching, a programmable memtransistor with arithmetic calculating and logic function is realized. Memtransistor with drain and gate adjustable non-volatile memory function effectively simulates the plasticity of biological synapses. Moreover, four arithmetical operations: addition, subtraction, multiplication and division are carried out by using the synaptic device. At the same time, the logic gate functions of “XOR” and “XNOR” were implemented based on ferroelectric memtransistor. This result will be helpful to further promote the development of memory computing for synaptic devices.

Using atomic absorption spectrometry to determine how sodium ions exchange between plant tissues (roots of Daucus carota L.) and a liquid aqueous environment during thermal treatments

In order to characterize the transport of sodium ions that takes place in roots of carrots Daucus carota L. during thermal treatment, without or with sodium chloride added to the liquid environment in which the roots are thermally processed, the sodium concentration of different parts of roots was measured by flame atomic absorption spectrometry (after prior mineralization). Much of the sodium lost during a treatment in pure water, or absorbed during a treatment in a solution of sodium chloride, is likely to be transferred both through lateral surfaces of roots and by the conductive channels (xylem, phloem). These results can help to determine how much salt is consumed, with traditional culinary preparations.

Synergistically improved hydroxide ions conduction of quaternized Poly(2.6 Dimethyl-1.4 phenylene Oxide)-Based anion exchange membrane with necklace shaped metal-organic Framework@Carbon nanotube oxide

During the development of anion exchange membranes (AEMs), there is a dilemma of mutual restriction relationship between quick hydroxide ions conduction and reinforced alkaline stability. In this research, the necklace shaped metal-organic framework (MOF) crystals decorating carbon nanotube oxide (OCNT) is prepared through the self-assembly process owing to the interfacial tension force and intermolecular hydrogen bonds. The necklace shaped MOF@OCNT is introduced into quaternized poly(phenylene) oxide (QPPO) to synergistically improve hydroxide ions conduction and alkaline stability of the QPPO/MOF@OCNT membrane. The hydroxide ions conduction process is accelerated even at subzero temperature owing to the formation of oriented hydroxide ions conduction channels. Additionally, MOF@OCNT can resist hydroxide radical (OH−) continuous attacks to functional groups in the polymer molecular chains of QPPO. As a result, QPPO/MOF@OCNT exhibits the hydroxide conductivities of 3.20 mS/cm at −25 °C and 44.8 mS/cm at 80 °C. Most importantly, the enhanced alkaline stability is revealed from the ten-cycle hydroxide conductivity and the long-term hydroxide conductivity. After immersing in 2 M potassium hydroxide (KOH) solution for 48 h, the tensile stress of QPPO/MOF@OCNT reaches 24.1 MPa. A single fuel cell with QPPO/MOF@OCNT as the electrolyte exhibits the peak power densities of 0.133 W/cm2 at 30 °C and 0.610 W/cm2 at 60 °C.

Crystallizing Self-Standing Covalent Organic Framework Membranes for Ultrafast Proton Transport in Flow Batteries.

Covalent organic frameworks (COFs) display great potential to be assembled into proton conductive membranes for their uniform and controllable pore structure, yet constructing self-standing COF membrane with high crystallinity to fully exploit their ordered crystalline channels for efficient ionic conduction remains a great challenge. Here, a macromolecular-mediated crystallization strategy is designed to manipulate the crystallization of self-standing COF membrane, where the -SO3 H groups in introduced sulfonated macromolecule chains function as the sites to interact with the precursors of COF and thus offer long-range ordered template for membrane crystallization. The optimized self-standing COF membrane composed of highly-ordered nanopores exhibits high proton conductivity (75 mS cm-1 at 100 % relative humidity and 20 °C) and excellent flow battery performance, outperforming Nafion 212 and reported membranes. Meanwhile, the long-term run of membrane is achieved with the help of the anchoring effect of flexible macromolecule chains. Our work provides inspiration to design self-standing COF membranes with ordered channels for permselective application.

Crystallizing Self‐Standing Covalent Organic Framework Membranes for Ultrafast Proton Transport in Flow Batteries

AbstractCovalent organic frameworks (COFs) display great potential to be assembled into proton conductive membranes for their uniform and controllable pore structure, yet constructing self‐standing COF membrane with high crystallinity to fully exploit their ordered crystalline channels for efficient ionic conduction remains a great challenge. Here, a macromolecular‐mediated crystallization strategy is designed to manipulate the crystallization of self‐standing COF membrane, where the −SO3H groups in introduced sulfonated macromolecule chains function as the sites to interact with the precursors of COF and thus offer long‐range ordered template for membrane crystallization. The optimized self‐standing COF membrane composed of highly‐ordered nanopores exhibits high proton conductivity (75 mS cm−1 at 100 % relative humidity and 20 °C) and excellent flow battery performance, outperforming Nafion 212 and reported membranes. Meanwhile, the long‐term run of membrane is achieved with the help of the anchoring effect of flexible macromolecule chains. Our work provides inspiration to design self‐standing COF membranes with ordered channels for permselective application.

Tungsten-Doped Indium Tin Oxide Thin-Film Transistors for Dual-mode Proximity Sensing Application.

Technologies for human-machine interactions are booming now. In order to achieve multifunctional sensing abilities of electronic skins, further developments of various sensors are in urgent demand. Herein, a dual-mode proximity sensor based on an oxide thin-film transistor (TFT) is reported. Although InSnO (ITO) is featured with high mobility, the inherent high carrier concentration limits its use as a channel material for thin-film transistors. Herein, the tungsten element was introduced as a carrier suppressor to develop ITO-based semiconducting materials and devices. TFTs with amorphous tungsten-doped ITO (ITWO) channel layers were fabricated. As for a flat panel display application, the TFT device from 250 °C-annealed ITWO layer with an atomic ratio of In/Sn/W = 86:9:5 presented the optimal device performance with carrier mobility of 11.53 cm2 V-1 s-1, swing subthreshold of 0.66 V dec-1, threshold voltage of -2.18 V, and Ion/Ioff ratio of 3.33 × 107 and much small hysteresis of transfer characteristic. ITWO TFT devices were further developed as dual-mode proximity sensors that could work with both extended-gate and compact configurations, where the drain current was directly related to the surface potential of a charged object and the distance between the sensing end and the object, enabling the proximity sensing of charged stimuli. For extended-gate-configured proximity sensing, a charged object modulated the formation of a conductive channel at the semiconductor/SiO2 interface, while this conductive channel occurred at the semiconductor/air interface for compact-configured sensing. Formation of the conductive channel of the compact transistor was modulated by the electric field component in the direction perpendicular to the interface, and the drain current was sensitive to the orientation of the approaching object, which implied the capacity of angle sensing to the approach of a charged object. This work further emphasizes that the basic device performance should be optimized according to its specific application scenarios rather than only considering the requirements of the panel display.

Diamond Electronics and Related Wideband Gap Semiconductors for High Temperature Applications

This presentation is focused on understanding the basic science of two-dimensional carrier systems in diamond-based semiconductor electronics. Over the course of the presentation, we will present the following: • Process technology for diamond power field effect transistors (FETs) based on two-dimensional (2D) carrier transport in subsurface boron delta-doped structures • The theory of carrier transport in diamond FETs with 2D conducting channels • The results from materials and defect characterization techniques to locate, characterize, and monitor radiation-induced defects in these structures over various timescales • New research directions in applying 2D conduction channels to ultra-wide bandgap semiconductor transistors based on diamond materials as well as related wide band gap semiconductors, • Understand the dominant failure mechanisms operative in diamond-based FETs exposed to ionizing and non-ionizing radiation.

Layered GeSe/thermally-reduced graphene oxide composites as efficient anodes for high-performance Li-ion batteries

Due to their layered structure and greater electrical conductivity compared to traditional metal oxides, layered metal selenides have been extensively explored as promising electrode materials for Li-ion batteries. The greatest obstacles to their continued growth, however, are the substantial volume change and particle agglomeration during cycling. In this work, layered GeSe/ thermally-reduced graphene oxide (TRG) composites were successfully synthesized by using a facile shear-force exfoliation approach. When a highly conductive TRG matrix was incorporated with GeSe particles, the resultant GeSe/TRG composite electrode achieved an impressive reversible capacity (>840.1 mAh g−1 at 0.1C), improved rate capability as well as excellent cycling stability. The remarkable improvement in electrochemical performance of the GeSe/TRG composite electrode corresponds to the TRG matrix, which potentially constructs an efficient conductive channel and serves as a flexible mechanical buffer for the restriction of volume expansion and particle aggregation.