Well-defined Interface Research Articles

Gluing Ionic Liquids to Oxide Surfaces: Chemical Anchoring of Functionalized Ionic Liquids by Vapor Deposition onto Cobalt(II) Oxide.

Ionic liquids (IL) hold a great potential as novel electrolytes for applications in electronic materials and energy technology. The functionality of ILs in these applications relies on their interface to semiconducting nanomaterials. Therefore, methods to control the chemistry and structure of this interface are the key to assemble new IL-based electronic and electrochemical materials. Here, we present a new method to prepare a chemically well-defined interface between an oxide and an IL film. An imidazolium-based IL, which is carrying an ester group, is deposited onto cobalt oxide surface by evaporation. The IL binds covalently to the surface by thermally activated cleavage of the ester group and formation of a bridging carboxylate. The anchoring reaction shows high structure sensitivity, which implies that the IL film can be adhered selectively to specific oxide surfaces.

Interdiffusion Reaction-Assisted Hybridization of Two-Dimensional Metal-Organic Frameworks and Ti3C2Tx Nanosheets for Electrocatalytic Oxygen Evolution.

Two-dimensional (2D) metal-organic framework (MOF) nanosheets have been recently regarded as the model electrocatalysts due to their porous structure, fast mass and ion transfer through the thickness, and large portion of exposed active metal centers. Combining them with electrically conductive 2D nanosheets is anticipated to achieve further improved performance in electrocatalysis. In this work, we in situ hybridized 2D cobalt 1,4-benzenedicarboxylate (CoBDC) with Ti3C2Tx (the MXene phase) nanosheets via an interdiffusion reaction-assisted process. The resulting hybrid material was applied in the oxygen evolution reaction and achieved a current density of 10 mA cm-2 at a potential of 1.64 V vs reversible hydrogen electrode and a Tafel slope of 48.2 mV dec-1 in 0.1 M KOH. These results outperform those obtained by the standard IrO2-based catalyst and are comparable with or even better than those achieved by the previously reported state-of-the-art transition-metal-based catalysts. While the CoBDC layer provided the highly porous structure and large active surface area, the electrically conductive and hydrophilic Ti3C2Tx nanosheets enabled the rapid charge and ion transfer across the well-defined Ti3C2Tx-CoBDC interface and facilitated the access of aqueous electrolyte to the catalytically active CoBDC surfaces. The hybrid nanosheets were further fabricated into an air cathode for a rechargeable zinc-air battery, which was successfully used to power a light-emitting diode. We believe that the in situ hybridization of MXenes and 2D MOFs with interface control will provide more opportunities for their use in energy-based applications.

Dynamic Modeling of a Parabolic Trough Solar Thermal Power Plant with Thermal Storage Using Modelica

ABSTRACTConcentrating solar power (CSP) technology with thermal energy storage is a renewable and emerging technology. In this work, dynamic models for analyzing and evaluating energy storage concepts and its interaction with the solar field and the power block have been developed. A physical model of a 50 MW CSP plant has been implemented in the modeling language Modelica. The models are developed in a modular, flexible structure with a well-defined interface to easily replace and test modules of various detail and complexity. Models include turbine island, steam generator, solar field, and thermal energy storage system. In addition, a decentralized control configuration has been developed. Results have been successfully validated against the reference plant key steady-state data. Dynamic response of the power block has shown expected behavior, and transient durations were comparable with settling times predicted in literature. Furthermore, the performance of the plant has been evaluated during a typical summer day including effects such as variation of solar irradiance, charging and discharging the heat storage system, and dumping excess heat in the solar field. The summer day scenario results agreed with published performance of the plant.

Effect of interface on epitaxy and magnetism in h-RFeO3/Fe3O4/Al2O3 films (R = Lu, Yb)

We have carried out the growth of h-RFeO3 (0 0 1) (R = Lu, Yb) thin films on Fe3O4 (1 1 1)/Al2O3 (0 0 1) substrates, and studied the effect of the h-RFeO3 (0 0 1)/Fe3O4 (1 1 1) interfaces on the epitaxy and magnetism. The observed epitaxial relations between h-RFeO3 and Fe3O4 indicate an unusual matching of Fe sub-lattices rather than a matching of O sub-lattices. The out-of-plane direction was found to be the easy magnetic axis for h-YbFeO3 (0 0 1) but the hard axis for Fe3O4 (1 1 1) in the h-YbFeO3 (0 0 1)/Fe3O4 (1 1 1)/Al2O3 (0 0 1) films, suggesting a perpendicular magnetic alignment at the h-YbFeO3 (0 0 1)/Fe3O4 (1 1 1) interface. These results indicate that Fe3O4 (1 1 1)/Al2O3 (0 0 1) could be a promising substrate for epitaxial growth of h-RFeO3 films of well-defined interface and for exploiting their spintronic properties.

Identifying User-Input Privacy in Mobile Applications at a Large Scale

Identifying sensitive user inputs is a prerequisite for privacy protection in mobile applications. When it comes to today’s program analysis systems, however, only those data that go through well-defined system Application Program Interface (system controlled resources) can be automatically labeled. In this paper, we show that this conventional approach is far from adequate, as most sensitive inputs are actually entered by the user at an app’s runtime. In this paper, we inspect 13,072 top apps from Google Play, and find that 38.69% of them involve sensitive user inputs. Just like system controlled resources, these data are also exposed to a series of privacy leakage threats. For these sensitive user inputs, manually marking them involves a lot of efforts, impeding a large-scale, automated analysis of apps to defend against potential privacy leakage. To address this important issue, we present UIPicker , an adaptable framework for automatic identification of sensitive user inputs as the first step. UIPicker is designed to detect the semantic information within the application layout resources and the program code, and further analyze it for the locations where security-critical information may show up. This approach can support a variety of existing security analysis on mobile apps. We evaluate our approach over randomly selected popular apps on Google Play. UIPicker is able to accurately label sensitive user inputs most of the time, with 94.0% precision and 96.0% recall.

Enhanced photocatalytic degradation of Rhodamine B by reduced graphene oxides wrapped-Cu2SnS3 flower-like architectures

Abstract In this work, an ordered flower-like Cu 2 SnS 3 /reduced graphene oxide (CTS/RGO) hybrid materials was successfully synthesized via a facile and efficient hydrothermal route using thiourea as sulfur source and polyvinylpyrrolidone as chelating agent. The formation of CTS architectures and reduction of graphene oxide (GO) occur at the same time during the hydrothermal process. The flower-like CTS architectures were self-assembled by many nanosheets with an average thickness of 45 nm, and were wrapped in RGO nanosheets. The composite exhibited enhanced photocatalytic activities for the degradation of Rhodamine B (RhB) under visible light irradiation. The photodegradation rate of RhB in aqueous solutions (2 × 10 −5 ) reached to 87% in 210 min, which presented higher activity than pure CTS. The factors influencing photocatalytic activity, the photostability and the possible mechanism for the improved performance of CTS/RGO hybrid materials were also discussed and proposed. The present study may provide a new approach to gain in-depth insight to the design a highly efficient photocatalyst with well-defined interface.

Effect of device structure on the resistive switching characteristics of organic polymers fabricated through all printed technology

Developments in organic bi-stable non-volatile memory devices have shown that organic materials are essential for the next generation of electrical memory unit owing to their low cost, high flexibility and large scalability. This study depicts an important aspect of organic memory devices by observing the effect of changing device structure on its switching characteristics. Memory devices with a bilayer and bulk-heterojunction structure were fabricated through an all printed technology by utilizing two organic polymers such as MEH: PPV and PMMA. Silver (Ag) was selected as the top and bottom electrode due to its high conductivity and easy processing. Though identical polymers were used in both device structures, but interestingly change in structure caused change in properties. It was observed that bilayer structure had much higher switching ratio and stability against various biasing cycles as compared to its bulk-heterojunction counterpart. Superior switching characteristics of bilayer structure were due to the presence of a well-defined interface between both polymers. Bulk-heterojunction device suffers the drawback of phase separation in a single organic layer between the two polymers.

Oriented growth of layered-MnO2 nanosheets over α-MnO2 nanotubes for enhanced room-temperature HCHO oxidation

Construction of heterostructures with well-defined size, dimension, surface and interface is an effective approach to develop enhanced and unprecedented functionality. Herein, oriented growth of layered-MnO2 nanosheets (L-MnO2) over α-MnO2 nanotubes backbones is demonstrated. The epitaxial relationship in the resulting α-MnO2@L-MnO2 heteroepitaxy is rationalized as (110)(α-MnO2)||(001)(layered-MnO2). With loading of 1wt% Pt nanoparticles over the MnO2 samples, the resulting Pt/MnO2 samples show catalytic activity toward room-temperature HCHO oxidation via “HCHO+O2=CO2+H2O”. Upon 1h treatment, 92.1% HCHO becomes mineralized over the Pt/α-MnO2@L-MnO2, higher than that of 81.3% and 75.9% for the Pt/α-MnO2 and Pt/L-MnO2. The oxidation of HCHO was well fitted with the second-order kinetic model, with the rate constant of the Pt/α-MnO2@L-MnO2 exceeding that of the Pt/α-MnO2 and the Pt/L-MnO2 by 2.27 and 5.92 times. Density-Functional-Theory (DFT) simulations show that α-MnO2 {100} surface facilitates adsorption/activation of O2, and layered-MnO2 {001} surface is beneficial to desorption of resultant H2O. The α-MnO2@L-MnO2 heteroepitaxy simultaneously integrates exposed facets of α-MnO2 {100} surface and layered-MnO2 {001} surface, in which the synergetic effect of the two surfaces leads to significantly enhanced room-temperature HCHO oxidation activity. The present study provides a rational design of manganese oxide-based catalysts for advanced environmental and energy applications.

An approach for scaling cloud resource management

Given its current development trajectory, the complexity of cloud computing ecosystems are evolving to where traditional resource management strategies will struggle to remain fit for purpose. These strategies have to cope with ever-increasing numbers of heterogeneous resources, a proliferation of new services, and a growing user-base with diverse and specialized requirements. This growth not only significantly increases the number of parameters needed to make good decisions, it increases the time needed to take these decisions. Consequently, traditional resource management systems are increasingly prone to poor decisions making. Devolving resources management decisions to the local environment of that resource can dramatically increase the speed of decisions making; moreover, the cost of gathering global information can thus be eliminated; saving communication costs. Experimental data, provided in this paper, illustrate that extant cloud deployments can be used as effective vehicles for devolved decision making. This finding strengthens the case for the proposed paradigm shift, since it does not require a change to the architecture of existing cloud systems. This shift would result in systems in which resources decide for themselves how best they can be used. This paper takes this idea to its logical conclusion and proposes a system for supporting self-managing resources in cloud environments. It introduces the concept of coalitions, consisting of collaborating resources, formed for the purpose of service delivery. It suggests the utility of restricting the interactions between the end-user and the cloud service provider to a well-defined services interface. It shows how clouds can be considered functionally, as engines for delivering an appropriate set of resources in response to service requests. And finally, since modern applications are increasingly constructed from sophisticated workflows of complex components, it shows how combinatorial auctions can be used to effectively deliver packages of resources to support those workflows.

基于Vaadin的旋转机械动平衡计算系统开发与应用

传统的WEB应用程序在不同终端不同平台开发时，为实现全方位、多角度的用户需要而采用不同的开发框架，这无疑增加了开发人员的开发量和维护量。Vaadin是一个用于创建富客户端(RIA)应用程序的前端开发框架，应用程序在不同终端和平台实现时都基于相同的框架，其具有种类丰富和功能完善的界面表现力、灵活的数据监听处理功能，同时能兼顾跨平台跨终端的触屏交互、动画切换等移动特性。为实现旋转机械动平衡计算在智能手机、PAD等移动终端的应用需求，同时兼顾系统交互性和功能性，本文基于Vaadin开发框架设计实现了旋转机械动平衡计算系统。实例应用表明，系统在跨平台跨终端实现时，不仅显著提高了开发效率，也兼顾了不同终端的用户体验。 Traditional WEB applications use different development framework in different terminal and different platform development, in order to achieve all-round, multi-angle user needs, which un-doubtedly increase the developer’s development amount and maintenance amount. Vaadin is a new development framework for creating rich client (RIA) applications, which are based on the same framework when they are implemented on different terminals and platforms, with a rich and well-defined interface presentation, flexible data listening processing functions, and mobile features, such as cross-platform cross-terminal touch screen interaction, animation switching and so on. In order to realize the application of rotating machinery dynamic balance calculation in mobile phones such as smart phones and PADs, taking into account the system interactivity and functionality at the same time, this paper realizes the dynamic balance calculation system of rotating machinery based on Vaadin development framework design. Case application shows that when the system implements on cross-platform cross-terminal, it not only significantly improves the development efficiency, but also takes into account the different terminal user experience.

Tricalcium Phosphate - Magnesium Interface: Microstructure and Properties

The fabrication of a composite material based on magnesium (Mg) and tricalcium phosphate is reported in this work. Rods of β-tricalcium phosphate (β-TCP) were processed and consolidated together with pure Mg powder through spark plasma sintering (SPS). The microstructure at the interface, the chemical composition and transformation of the components and the microhardness were analysed. The microstructure of the composite shows two zones with well-defined and continuous interface between them: a ceramic zone composed by β-TCP filled with Mg and the metallic zone constituted by Mg and Mg rich eutectic. Vickers hardness shows the excellent mechanical interaction between the two zones.

In-situ growth of g-C3N4 layer on ZnO nanoparticles with enhanced photocatalytic performances under visible light irradiation

We proposed a facile method to prepare ZnO@g-C3N4 core/shell type photocatalyst via a two-step calcination. Thin layer of g-C3N4 was homogeneously coated on ZnO nanoparticles with well-defined interface, which reduces the charge transfer resistance and results in distinct PL quenching. Therefore, the as-prepared ZnO@g-C3N4 demonstrates significant photocatalytic improvement under visible-light irradiation than ZnO (~35 times) and g-C3N4 (~5 times) due to the effective charge separation and suppressed carrier recombination. Moreover the ZnO@g-C3N4 photocatalyst shows high stability which retains ~90% of its initial activity after 5-cycle reuse.

Bismuth core fibers

Elemental bismuth (Bi) exhibits a high magnetoresistance as a typical example of semimetal, which has significant application in information technologies. Silicate glass-clad Bi core fibers were fabricated by a molten core method and maintained core diameter of 100–150µm and overall diameter of 300–450µm. X-ray diffraction (XRD) and micro-Raman spectra showed the core to be highly crystalline with no observed secondary phases. Electro-probe micro-analyzer (EPMA) measurements confirmed a very well-defined core-clad interface. Demonstration of fibers with high magnetoresistance core materials and the potential integration with current state of the art technologies represents the first step in providing the building blocks for all-fiber sensors.

Environmental control of electron–phonon coupling in barium doped graphene

Two-dimensional superconductivity in alkali- and alkaline-Earth-metal doped monolayer graphene has been explained in the framework of electron–phonon coupling (EPC) and experiments yielded superconducting transition temperatures (TC) up to 6 K. In contrast to bulk graphite intercalation compounds, the interface of doped graphene with its environment affects its physical properties. Here we present a novel and well-defined BaC8 interface structure in Ba-doped single-layer graphene on Au and Ge substrates. We use angle-resolved photoemission spectroscopy in combination with ab initio modelling to extract the Eliashberg function and EPC for both substrates. This allows us to quantitatively assess the environmental effects for both Au and Ge substrates on superconductivity in graphene. We show that for semiconducting Ge substrates, the doping level and EPC are higher. Our study highlights that both dopant order and the metallicity of the substrate can be used to control EPC and hence superconductivity.

Spin accumulation at in-situ grown Fe/GaAs(100) Schottky barriers measured using the three- and four-terminal methods

We examined the spin accumulation in Fe/n-GaAs Schottky barriers to evaluate the accuracy of the three-terminal (3T) and four-terminal (4T) measurement geometries. A fully epitaxial Fe/n-GaAs junction was grown in situ using cluster molecular beam epitaxy without breaking the vacuum to exclude the formation of an oxide layer or surface roughness at the interface during intermixing. The spin resistance of the 4T nonlocal spin valve (ΔRNLSV = 0.71 Ω) was twice the value obtained using the 4T Hanle effect method (ΔR4TH = 0.35 Ω) at 10 K, as predicted theoretically, and this value remained constant over the temperature range examined, from 10 K to 77 K. The temperature-dependent spin lifetimes measured using the 3T and 4T Hanle effects exhibited similar behaviors. Although the spin resistance obtained using the 3T Hanle effect was enhanced compared with that obtained using the 4T effect, it was reasonable to conclude that the spin signals obtained from the 3T and 4T measurements originated from spin accumulation in n-GaAs due to the absence of an oxide tunnel barrier or a well-defined interface in our samples. These results completely ruled out any other sources of artifacts.

Synthesis of 2D-Mesoporous-Carbon/MoS2 Heterostructures with Well-Defined Interfaces for High-Performance Lithium-Ion Batteries.

A sandwich-like 2D-mesoporous-carbon/MoS2 -nanosheet heterostructure is fabricated for the first time. The hybrid structure is composed of three well-stacked monolayers: an ordered-mesoporous-carbon monolayer, a MoS2 monolayer, and a further ordered-mesoporous-carbon monolayer. This unique heterostructure exhibits excellent electrochemical performance as an anode material for lithium-ion batteries.

Reconstruction of the LiCoO2 Near-Surface Region upon Overgrowth of Lipon

Recently, all-solid-state batteries have been actively studied for a next-generation secondary battery. All-solid-state batteries have an advantage in safety compared with the current flammable liquid electrolyte-based lithium ion batteries because of its excellent chemical stability. In addition, since this improved stability will eliminate the need for safety apparatus, the energy density of the all-solid-state battery module is also expected to be improved. One of the major issues of all-solid-state batteries towards their practical application is high interfacial resistance between the solid electrolyte and electrode active materials. While it has been speculated that space charge layer formation at the interface is a major factor for the high interfacial resistance, the interfacial phenomena still remains unclear due mainly to the difficulty in analysis of the interface in bulk battery form. In this study, we prepared thin-film battery with a well-defined pristine interface using thin film technique, and studied the changes in the crystal structure and electronic state in the vicinity of the interface between the cathode active material and solid electrolyte upon charging and discharging. In this study, we used LiCoO2 as an positive-electrode active material, and LiPON as a solid electrolyte. LiCoO2 was epitaxially grown in (104) orientation after forming the SrRuO3 as a current collector on SrTiO3(100) substrate by Pulsed laser deposition (PLD). LiPON was deposited on LiCoO2 by RF sputtering method using Li3PO4 as a target under N2 atmosphere. Li metal was deposited by vapor deposition as a negative electrode. In all the film formation processes, the samples were kept in vacuum to prevent the surfaces from being exposed to air in order to maintain clean and pristine interfaces. Cross sectional transmission electron microscope (TEM) images of the as-deposited film revealed the presence of the interfacial layer between LiCoO2 and LiPON which corresponds to neither LiCoO2 nor LiPON. The thickness of the interfacial layer was about 15 nm. From the results of TEM-EDS and electron diffraction, the interfacial layer is composed of elements of Li, Co and O, and its structure is similar to LiCoO2 but with larger lattice constant than LiCoO2. In addition, from TEM-EELS measurement results, Li-K edge of the interface layer was found to be shifted to the low-energy side compared with that of LiCoO2. This indicates that the Li in the interfacial layer is bounded more weakly than that of LiCoO2. By charging and discharging the above thin film battery at a current density of 4.33 μA/cm2(1/20C), the discharge capacity of 140 mAh/g was obtained. The characterisitic plateau associated with the oxidation-reduction of LiCoO2 was observed, which confirms excellent charge and discharge characteristics of the thin film battery. Taking the cross sectional TEM images after charging and discharging, the interface layer disappeared after charging while the interface layer was found to appear again after discharge. From this result, it can be inferred that the interface layer was formed when the Li concentration of LiCoO2 in the vicinity of the interface was high. The effect of interfacial layer on the electrochemical properties are to be discussed at the presentation.

Oxidation of Si Surfaces: Effect of Ambient Air and Water Treatments on Surface Charge and Interface State Density

Surface sensitive methods, UV-VIS spectral ellipsometry (SE), surface photovoltage (SPV) measurements, and X-ray photoelectron spectroscopy (XPS) measurements were combined to investigate in detail the Si substrate oxidation and resulting interface electronic properties. Various wet-chemical oxidation methods utilizing hot deionized water with different HCl or Ozone content were optimized in order to prepare ultra-thin oxide layers with reproducible oxide thicknesses (<dox > 0.3 to 3.5 nm), low values of interface state densities and well-defined interface charges. The simulation tool ELifAnT (Effective Lifetime Analysis Tool) was utilised to analyse experimental excess minority charge carrier density (Δn) dependent charge carrier lifetimes τeff (Δn), and to establish correlations between preparation induced interface charges Qit and defect densities Dit on both p-and n-type substrates.

OpenMS: a flexible open-source software platform for mass spectrometry data analysis.

High-resolution mass spectrometry (MS) has become an important tool in the life sciences, contributing to the diagnosis and understanding of human diseases, elucidating biomolecular structural information and characterizing cellular signaling networks. However, the rapid growth in the volume and complexity of MS data makes transparent, accurate and reproducible analysis difficult. We present OpenMS 2.0 (http://www.openms.de), a robust, open-source, cross-platform software specifically designed for the flexible and reproducible analysis of high-throughput MS data. The extensible OpenMS software implements common mass spectrometric data processing tasks through a well-defined application programming interface in C++ and Python and through standardized open data formats. OpenMS additionally provides a set of 185 tools and ready-made workflows for common mass spectrometric data processing tasks, which enable users to perform complex quantitative mass spectrometric analyses with ease.

Computing Repairs of Inconsistent DL-Programs over EL Ontologies

Description Logic (DL) ontologies and non-monotonic rules are two prominent Knowledge Representation (KR) formalisms with complementary features that are essential for various applications. Nonmonotonic Description Logic (DL) programs combine these formalisms thus providing support for rule-based reasoning on top of DL ontologies using a well-defined query interface represented by so-called DL-atoms. Unfortunately, interaction of the rules and the ontology may incur inconsistencies such that a DL-program lacks answer sets (i.e., models), and thus yields no information. This issue is addressed by recently defined repair answer sets, for computing which an effective practical algorithm was proposed for DL-Lite A ontologies that reduces a repair computation to constraint matching based on so-called support sets. However, the algorithm exploits particular features of DL-Lite A and can not be readily applied to repairing DL-programs over other prominent DLs like EL. compared to DL-Lite A , in EL support sets may neither be small nor only few support sets might exist, and completeness of the algorithm may need to be given up when the support information is bounded. We thus provide an approach for computing repairs for DL-programs over EL ontologies based on partial (incomplete) support families. The latter are constructed using datalog query rewriting techniques as well as ontology approximation based on logical difference between EL-terminologies. We show how the maximal size and number of support sets for a given DL-atom can be estimated by analyzing the properties of a support hypergraph, which characterizes a relevant set of TBox axioms needed for query derivation. We present a declarative implementation of the repair approach and experimentally evaluate it on a set of benchmark problems; the promising results witness practical feasibility of our repair approach.