Surface Electrical Properties Research Articles

Experimental, Hirshfeld surface computational and electrical properties of a novel organic cation perchlorate

Experimental, Hirshfeld surface computational and electrical properties of a novel organic cation perchlorate

Mechanism of micro-wetting of highly hydrophobic coal dust in underground mining and new wetting agent development

The internal mechanism of the high hydrophobicity of the coal samples from the Pingdingshan mining area was studied through industrial, element, and surface functional group analysis. Laboratory testing and molecular dynamics simulations were employed to study the impact of three types of surfactants on the surface adsorption properties and wettability of highly hydrophobic bituminous coal. The results show that the surface of highly hydrophobic bituminous coal is compact, rich in inorganic minerals, and poorly wettable and that coal molecules are dominated by hydrophobic functional groups of aromatic rings and aliphatic structures. The wetting performance of surfactants as the intermediate carrier to connect coal and water molecules is largely determined by the interaction force between surfactants and coal (Fs-c) and the interaction force between surfactants and water (Fs-w), which effectively improve the wettability of modified coal dust via modifying its surface electrical properties and surface energy. A new type of wetting agent with a dust removal rate of 89% has been developed through discovery of a compound wetting agent solution with optimal wetting and settling performance. This paper provides theoretical and technical support for removing highly hydrophobic bituminous coal dust in underground mining.

Surface Morphology and Electronic Properties of SnTe Films Prepared by Molecular Beam Epitaxy

SnTe is receiving a lot of attention as a topological crystalline insulator. Herein, SnTe films are grown directly on GaAs (100) substrates by molecular beam epitaxy. The surface morphology and electronic properties are measured by atomic force microscopy and Hall effect measurement, respectively. Considering previous X‐ray diffraction results, the samples grown with high beam‐intensity ratios show hexagonal Te segregation in the films, which deteriorates the surface morphology and decreases the conductivity. By suppressing the supply of Te, better surface morphology and electrical properties are obtained.

Resolving the Subsurface Structure and Elastic Modulus of Layered Films via Contact Resonance Atomic Force Microscopy.

Since its discovery, atomic force microscopy (AFM) has become widely used for surface characterization, evolving from a tool for probing surface topography to a versatile method for characterizing mechanical, electrical, chemical, magnetic, and electro-optical properties of surfaces at the nanoscale. Developments of several AFM-based techniques have enabled even subsurface imaging, which is routinely being carried out at the qualitative level of feature detection for localized subsurface inhomogeneities. We surmise, however, that a quantitative three-dimensional (3D) subsurface characterization can emerge from the AFM mechanical response of flat buried interfaces, and present here a methodology for determining the depth of a film and its mechanical properties. Using load-dependent contact resonance atomic force microscopy (CR-AFM) and accurate modeling of the contact between the AFM tip and a layered sample, we determine the relationship between the measured resonance frequency of the AFM probe and the contact stiffness. Our subsequent statistical analysis reveals an intrinsic and sample-specific interdependence between the depth and modulus sensitivities of CR-AFM. This interdependence prevents the simultaneous accurate determination of both depth and modulus from measurements on a single-layered sample. If the elastic moduli of the sample components are predetermined from separate investigations of bulk samples (or otherwise known), then this methodology accurately yields the location of the interface between the layers of the sample; as such, it can serve as a nondestructive and robust technique for probing layer thickness, subsurface features, and elastic properties of materials used in semiconductor electronics, additive manufacturing, or biomaterials.

Growth Mechanism of Ice Lens in Saturated Clay Considering Surface Charge

The main purpose of this study is to reveal the growth mechanism of ice lens in saturated clay. The deformation and fracturing of clay skeletons caused by ice crystal growth during the freezing process are gradually discussed, and a theoretical model for the whole process of ice lens growth considering the surface charge is proposed. Firstly, the electrical properties of clay surfaces and the pore structure characteristics of frozen clay are introduced, and the stress of pore walls during the growth of single pore ice crystals is calculated. Secondly, the values of parameters in the theoretical formula of separation pressure between adjacent clay particles are given when considering the linear elasticity of clay. Finally, the formation mechanism of the new lens is described, and the crack growth velocity equation is given. This paper shows that: there is a good consistency between the soil tensile strength of the macroscopic dimension and the intergranular separation pressure of the molecular dimension in judging the production conditions of the new lens; the formation of the new ice lens is the result of the destruction of the pore structure and the propagation of cracks caused by the growth of ice crystals, and more pore freezing can be caused only when the infiltration path of the ice crystals is formed in the pore structure. In order to verify the model, the ultimate compressive strength of soil calculated in this study was compared with the existing test results, and the rationality and correctness of the model are discussed. This study is of great significance to accurately understand the frost heave process.

Effect of pulse overlapping on temperature field and physical characteristics in pulsed laser sintering of inkjet-printed silver nanoparticles

Pulsed laser sintering of metal nanoparticles (NPs) has been studied owing to its minimal impact on heat-sensitive zones. The characteristic effects of pulse overlapping during pulsed laser sintering of metal NPs on metal NP surface morphology and electrical properties have not been reported to date. We therefore investigated millisecond pulsed laser sintering of inkjet-printed silver (Ag) NP lines at 30, 50, 70, 80, and 90% pulse overlaps (POs). We then assessed the thermal, electrical, and surface-morphological characteristics for each PO case. The temperature history was investigated via numerical analysis using a designed algorithm for treating thermal conductivity. The 70% PO produced the lowest Ag NP line resistivity with the highest degree of consistency as a result of the uniform temperature distribution and relatively continuous surface morphology with minimal porosity. The results of this study can guide the understanding of the thermal response, electrical performance, and surface morphology of Ag NPs corresponding to pulse overlapping during a pulsed laser sintering operation.

Synthesis of Al and In dual-doped CuO nanostructures via SILAR method: Structural, optical and electrical properties

In this article, we investigated the doping characteristics of Al-doped CuO (ACO), and Al/In co-doped CuO (AICO) thin films, which were synthesized on glass substrates, via the solution-based successive ionic layer adsorption and reaction (SILAR) technique. The surface morphological, chemical composition, structural, optical, and electrical properties of the nanocrystalline films were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier-transform Infrared Spectroscopy (FTIR), Ultraviolet–visible (UV–vis.) spectrophotometry, and Transmission Line Method (TLM), respectively. Surface morphology studies exhibited that a decrease in the films' thickness caused an increment in the optical transmittance. XRD patterns displayed that the obtained samples were polycrystalline and crystallized in a bare CuO monoclinic structure. FTIR studies of the CuO samples displayed that Al and In co-doping influenced the forms and the violence of the absorption bands. The optical bandgap energy of bare CuO was determined to increase from 1.45 to 1.78 eV as a result of the co-doping. The substitution of In displayed in the irregularity of the morphology, owing to its wide ionic radius, which caused an increase in band gap energy and a decrease in resistance. The co-doping of Al and In is hence anticipated to ensure an extensive range of physical and optical properties of nanostructured metal oxide samples for a variety of technological applications.

Charge modifications of graphene oxide enhance the inhibitory effect on insulin amyloid fibrillation based on electrostatic interactions

Graphene oxide (GO) is a biocompatible nanomaterial that has an inhibitory effect on insulin amyloid fibrillation. In order to enhance the inhibitory effect of GO and explore the rules of electrostatic interactions on the inhibitory effect, carboxyl group, PEI and PEG were coupled to the GO nanoplatelet surface to prepare inhibitors of different surface electrical properties. The effects of surface electrical properties of inhibitors on insulin fibrillation were investigated. The results showed that GO, carboxyl group modified GO (GO-COOH), PEI modified GO (GO-PEI), and PEG modified GO (GO-PEG) inhibited insulin fibrillation in a dose-dependent manner. Compared with GO, positive charge-modified GO-PEI and negative charge-modified GO-COOH enhanced the inhibitory effect, while uncharged polymer-modified GO-PEG weakened the inhibitory effect. The inhibitory effect of the inhibitors increased with the increase of surface charge density. The difference in inhibitory effect between GO-PEI and GO-COOH was due to the different electrostatic interactions between inhibitors and insulin, and the different inhibition mechanisms. In addition, inhibitors mainly interact with insulin during the nucleation phase to hinder insulin fibrillation. The charge modifications of graphene oxide enhanced the inhibitory effect on insulin fibrillation based on electrostatic interactions, which will provide new thoughts for the development of anti-amyloid fibrillation drugs.

Effect of substrate temperature on the optical properties of DC magnetron sputtered copper oxide thin films

Copper oxide thin films are deposited on quartz substrates by DC magnetron sputtering and the effect of deposition temperature on the optical properties is examined in detail. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) analysis, Raman spectroscopy, UV–vis spectroscopy, and four-probe sheet resistance measurements are used to characterize the surface morphology, structural, optical, and electrical properties of the deposited films respectively. Sputter deposition is carried out with the substrate at room temperature and at elevated temperatures between 200 and 300 °C. XRD analysis indicates that the oxide formed is primarily Cu2O and the absorption spectra show a critical absorption edge at around 300 nm. The sheet resistance gradually decreases with increase in deposition temperature, corresponding to an increase in the conductivity of the films. Also observed is an increase in the band gap energy from 2.02 eV for room temperature deposition to 2.35 eV at 300 °C, corresponding to an improved film crystallinity and reduction in defect density. The band gap energy and the variation of sheet resistance with substrate temperature shows that the microstructure plays a vital role in their behavior. These transformation characteristics are of huge technological importance having variety of applications including transparent solar cell fabrication.

Time-course analysis of pulmonary inflammation induced by intratracheal instillation of nanosized crystalline silica particles in F344 rats.

Crystalline silica is an important cause of serious pulmonary diseases, and its toxic potential is known to be associated with its surface electrical properties. However, in vivo data clarifying the relevance of silica's toxic potential, especially its long-term effects, remain insufficient. To investigate the contribution of physico-chemical property including surface potential on the hazard of nanocrystalline silica, we performed single intratracheal instillation testing using five different crystalline silicas in a rat model and assessed time-course changes in pulmonary inflammation, lung burden, and thoracic lymph node loads. Silica-nanoparticles were prepared from two commercial products (Min-U-Sil5 [MS5] and SIO07PB [SPB]) using three different pretreatments: centrifugation (C), grinding (G), and surface dissolving (D). The five types of silica particles-MS5, MS5_C, SPB_C, SPB_G, and SPB_D-were intratracheally instilled into male F344 rats at doses of 0mg/kg (purified water), 0.22 mg/kg (SPB), and 0.67, 2, or 6mg/kg (MS5). Bronchoalveolar lavage, a lung burden analysis, and histopathological examination were performed at 3, 28, and 91 days after instillation. Granuloma formation was present in MS5 group at 91 days after instillation, although granuloma formation was suppressed in MS5_C group, which had a smaller particle size. SPB_C induced severe and progressive inflammation and kinetic lung overload, whereas SPB_G and SPB_D induced only slight and transient acute inflammation. Our results support that in vivo toxic potential of nanosilica by intratracheal instillation may involve with surface electrical properties leading to prolonged effect and may not be dependent not only on surface properties but also on other physico-chemical properties.

Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films.

This study focuses on the effect of the substrate temperature (TS) on the quality of VO2 thin films prepared by DC magnetron sputtering. TS was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that TS below 500 °C favors the growth of V2O5 phase, whereas higher TS (≥500 °C) facilitates the formation of the VO2 phase. Optical characterization of the as-prepared VO2 films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (Tt), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) between the insulating and metallic phases of the VO2 films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at TS lower than 650 °C presents significant challenges.

Electrochemical Determination of Levofloxacin Using Poly(Pyrogallol Red) Modified Glassy Carbon Electrode

AbstractIn this paper, an electrochemical sensor for levofloxacin detection was developed by electrochemical polymerization of pyrogallol red (PGR) on the glassy carbon electrode (GCE) surfaces. Surface morphology and electrical properties of the Poly(PGR)/GCE obtained was characterized by SEM and EIS techniques. Voltammetric behaviour of the levofloxacin was found pH dependent, and the best response was obtained at pH 6.0 PBS. By monitoring the peak current at around 0.9 V, a wide linear range of calibration graph: from 0.2 μM‐ 15 μM LEV and 15 μM‐ 355 μM for levofloxacin, and very low detection limit of 97 nM were achieved with amperometry. Selectivity of the method developed was proven in the presence of possible interfering substances and the method was successfully employed for levofloxacin detection in pharmaceutical tablet and synthetic urine sample.

Enhancement of surface electrical performances of epoxy film by blending with fluorinated and crosslinking monomer

• Fluorinated monomers were synthesized through a facile method to prepare fluorinated epoxy films. • Effects of introducing –CF 3 groups on physicochemical characters of the films are studied. • Electrical strength of the fluorinated film was evidently enhanced. In order to introduce fluorine-containing functional groups into epoxy resins to stably enhance the surface electrical properties of thin films, the trifluoromethyl group containing diglycidyl ethers bisphenol A (F-DGEBA) monomer was prepared by a simple and environmentally friendly method. Further, the film was obtained by blending the prepared monomers with DGEBA in different proportions and curing at high temperature with methyl tetrahydrophthalic anhydride (MTHPA). The prepared films not only have improved hydrophobic properties, but also exhibit better surface electrical properties. With the increase of the content of F-DGEBA, the epoxy resin films have higher surface insulation strength and better potential decay performance, which is due to the existence of –CF 3 groups changing the distribution of deep and shallow traps. Compared with the non-fluorinated film, the flashover voltage of the fluorinated film with the best electrical properties is increased by 32.2%, and the potential decay rate is also much faster.

Flexible kesterite thin-film solar cells under stress

Understanding the stress-induced phenomena is essential for improving the long-term application of flexible solar cells to non-flat surfaces. Here, we investigated the electronic band structure and carrier transport mechanism of Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic devices under mechanical stress. Highly efficient flexible CZTSSe devices were fabricated controlling the Na incorporation. The electronic structure of CZTSSe was deformed with stress as the band gap, valence band edge, and work function changed. Electrical properties of the bent CZTSSe surface were probed by Kelvin probe force microscopy and the CZTSSe with Na showed less degraded carrier transport compared to the CZTSSe without Na. The local open-circuit voltage (VOC) on the bent CZTSSe surface decreased due to limited carrier excitation. The reduction of local VOC occurred larger with convex bending than in concave bending, which is consistent with the degradation of device parameters. This study paves the way for understanding the stress-induced optoelectronic changes in flexible photovoltaic devices.

Tailor-designed Pd-Cu-Ni/rGO nanocomposite for efficient glucose electro-oxidation

• Pd-Cu-Ni/rGO shows a striking activity towards GOR. • Capacitance measurements explain the observed enhancement. • Smart design of the catalyst increases the fuel utilization and turnover frequency values. • Pd-Cu-Ni/rGO/GC shows high sensitivity and selectivity towards GOR. The study presented in this paper introduces a promising ternary catalyst composed of palladium-copper-nickel nanocomposite which is electro-deposited at reduced graphene oxide modified glass carbon electrode (Pd-Cu-Ni/rGO/GC). The modified electrode is shown to exhibit an excellent activity towards glucose electrooxidation reaction (GOR), where the peak current obtained at its surface is 4.6, 3.0, 2.2 times of that achieved at Cu/rGO/GC, Ni/rGO/GC, and Pd/rGO/GC electrodes, respectively. Additionally, Pd-Cu-Ni/rGO/GC electrode exhibits a high capacitance, a long-term stability, besides supporting a high oxidation capacity and a high turnover frequency for GOR. Moreover, Pd-Cu-Ni/rGO/GC electrode exhibits a great sensitivity of 2800 µA mM −1 cm −2 to GOR with detection limit of 0.01 µM using a signal-to-noise ratio value of 3, it also has a high molecular selectivity for GOR. rGO is believed to augment the surface area, durability, and electrical properties of the catalyst. Pd provides the active sites and NiOx acts as a catalytic mediators for GOR. CuOx has a narrow band gap suitable for glucose sensing applications.

The Effects of Graphene Oxide and Reduced Graphene Oxide Conductive Additives on Activated Carbon Supercapacitors

With their relative ease of production and coupled strong surface functionality and electrical conductivity properties, graphene oxide (GO) and reduced graphene oxide (rGO) are exciting, yet overlooked, graphene-like additive prospects for activated carbon (AC) electrodes in supercapacitors. In this work, we incorporated small amounts of synthesized GO and rGO in AC electrodes via a simple mixing procedure to explore their effects. In addition to materials characterizations, symmetric supercapacitors were made from these electrodes and tested across current densities ranging from 0.1–10 A g−1 and across 10,000 additional charge-discharge cycles at 2 A g−1. Performance measurements indicate that GO and rGO enhance the rate resistance and capacity, respectively, of AC electrodes, but these effects are modest and do not prevent increases in internal resistance over the course of 10,000 cycles. The overall ineffectuality of GO and rGO is reasoned to be due to their isolation and infrequency as a result of the relatively impotent distribution method used.

Evaluation of L-arginine as an Eco-Friendly Activator for Malachite Sulfidization Flotation

Sulfidization xanthate flotation remains the most promising method for the beneficiation of malachite. In this study, L-arginine (LA) was first used to modify the malachite surface and improve the efficiency of sulfidization flotation. The performance of LA was evaluated by the flotation experiments. The mechanism of interaction between LA and the malachite surface was investigated by adsorption experiments, zeta potential measurements, scanning electron microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analysis. Flotation experiments showed that LA had a significantly promoting effect on malachite sulfidization flotation. Adsorption experiments and SEM-EDS results indicated that LA improved the adsorption of S (II) species into the malachite surface and promoted the formation of sulfides. This finding was further confirmed by the XPS analysis. The XPS measurements results determined that S (II) species reacted with Cu (II) on the malachite surface and form polysulfides, adding LA promoted the reaction. The zeta potential measurements showed that LA increased the positive electrical properties of the mineral surface, which was conducive to S (II) species adsorption and the sulfidization reaction. This work sheds new light on the development of sulfidization activation.

Ultra-large dynamic range synaptic indium gallium zinc oxide transistors

Three-terminal neuromorphic transistors have garnered considerable attention owing to their superior learning and recognition capabilities in neural computing. For efficient and rapid computing of parallel arithmetic and unstructured large-sized data, a high-synaptic channel conductance (G) (i.e., synaptic weight) and large dynamic range (DR) (i.e., weight update) are necessary. In this study, we successfully fabricated high-performance and all-solution-processed synaptic transistors by employing a thiol–ene photoclick chemistry-based, cross-linked vinyl addition polynorbornene copolymer dielectric layer, poly(norbornene-co-5-vinyl-2-norbornene) (P(NB/VNB)) and sol-gel-derived indium gallium zinc oxide (IGZO) semiconducting channel layer. The molecular behaviors of free hydroxyl group in the dielectric layer formed via ultraviolet photo-induced thiol–ene click reactions of the polar cross-linker pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) allows slow dipole polarization effects on the IGZO channel layer. An exhaustive and systemic investigation of the surface physicochemical and electrical properties confirmed that the mutual interface coupling between the cross-linked P(NB/VNB) dielectric and IGZO semiconductor exhibited remarkable synaptic functionality with a high G (∼540 μS), large DR (∼6213), and long-term operational stability following excitation with 104 successive pulses that resulted in neural recognition accuracy of 87.11% based on the use of MNIST database set which is close to ideal value of 88%. This high-performance synaptic transistor based on all-solution-derived functional organic–inorganic hybrid stack layers can serve as a basis for the successful implementation of novel neuromorphic computing systems that satisfy the requirements for strong neuronal signal transmission and distinguishable multi-level data states.

Controlled Surface Morphology and Electrical Properties of Sputtered Titanium Nitride Thin Film for Metal–Insulator–Metal Structures

Titanium nitride (TiN) is a material of interest for electrodes owing to its high-temperature stability, robustness, low-cost, and suitable electrical properties. Herein, we studied the surface morphology and electrical properties of TiN thin film deposited onto an Si/SiO2 <100> substrate through direct current (DC) sputtering with a high-purity TiN target in an argon-gas environment. The electrical properties and surface morphology of TiN thin film significantly improved with increased source power and decreased working pressure. The improved electrical properties could be attributed to the suppressed secondary phase (Ti2N) formation and the reduced electron scattering on smoother surface. Consequently, high-quality TiN thin film with the lowest resistivity (ρ = 0.1 mΩ·cm) and the smallest surface roughness (RMS roughness, Rq = 0.3 nm) was obtained under the optimized condition. The TiN film was further used as the bottom electrode for a metal–insulator–metal (MIM) capacitor. Results demonstrated that the electrical properties of TiN film were comparable to those of noble-metal thin films. Therefore, the TiN thin film fabricated by DC sputtering method had excellent electrical properties and good Rq, indicating its potential applications in MIM capacitors and Si technology.

Measurement and Analysis of Mechanical Properties of All-Solid-State Electrodes Fabricated By Dry Process with Saicas

Due to battery fire accidents while driving and charging an electric vehicle, research on improving battery safety as well as increasing the energy density has been extensively performed. For this purpose, an all-solid-state battery without the flammable liquid electrolyte is being more actively conducted. Among various solid electrolyte types, the sulfide-based solid electrolyte has been investigated as the most promising candidate owing to its high ionic conductivity and ductility. However, since sulfide solid electrolyte is too reactive to organic solvents like N-methyl pyrrolidone, a few nonpolar solvents (xylene or toluene) can be used to fabricate sulfide solid electrolyte. Thus, except for rubber binders such as nitrile butadiene rubber, other conventional adhesive binders are excluded from candidates. So, to solve this limitation fundamentally, a dry process without any solvents must be an attractive method for using the sulfide electrolyte in battery manufacturing process. For example, polytetrafluoroethylene (PTFE) is frequently used for fabricating all-solid-state electrode (ASSE) with sulfide electrolytes due to its wonderful fibrilization property. However, comparing to the wet process, it is more challenging to distribute all the electrode components uniformly in the dry process, where all the components are mixed through kneading the electrode dough. That is, to maximize the electrochemical performances of ASSEs, it is essential to evaluate the mechanical properties of ASSEs fabricated from dry process and to quantify them for optimization. However, most of research on ASSEs have been focused on their electrochemical performances up to now.Thus, in this work, we attempted to measure the mechanical properties of ASSEs with sulfide electrolyte using a surface and interfacial cutting analysis system (SAICAS). The ASSEs were fabricated through dry process while changing the PTFE binder content. Subsequently, both bulk and interfacial adhesive strengths were analyzed systematically and deliberately by a few μm resolution. Furthermore, to unveil the surface, bulk, and interfacial electrical properties are also measured using an electrode resistance measuring instrument (HIOKI RM2610). Thus, we can provide a correlation between binder content and mechanical/electrical properties of dry ASSEs. Finally, comparative results based on wet processed ASSEs will also be included in this work.