Dual Surface Research Articles

Molten salt-lithium process induced controllable surface defects in titanium oxide for efficient photocatalysis

The efficiency of photoabsorption, photo-generated charge separation, and surface redox reaction determine the overall efficiency of photocatalysts. Therefore, exploring ways to simultaneously optimize the parameters is key to improving the photocatalytic performance. Herein, a novel low-temperature ternary molten salt-lithium reduction method is designed to create controllable oxygen vacancies (Ovs) as well as to manipulate the surface microstructure of the classic photocatalyst TiO2. The optimized TiO2 exhibits a 10-fold increase in the photocatalytic RhB breakdown rate and H2 generation quantity compared to pristine TiO2. The dual surface defects result in synergistic effects: i) Ovs lower band gap, enhance the charge separation efficiency as capture centers, and facilitate hydrogen adsorption; ii) the enlarged surface area enhances light-harvesting and provides more active sites. This research proposes a novel strategy for manipulating surface defects in a controlled manner and highlights the synergistic optimization of the thermodynamical and kinetical parameters to promote the photocatalytic performance.

Construction of micro/macro‐scale Janus polypeptoid‐based two‐dimensional structures at the air–water interface

AbstractJanus two‐dimensional (2D) polymeric materials present asymmetric dual surfaces that enable a variety of applications of biosensors, catalysts, drug delivery, etc. This work reports the evaporation‐induced interfacial self‐assembly of amphiphilic block copolymer poly(ethylene glycol)‐b‐poly(N‐(2‐phenylethyl) glycine) (PEG‐b‐PNPE) at the air–water interface. The PEG‐b‐PNPE was initially assembled into a monolayer with a uniform thickness of ~2.5 ± 0.1 nm, which was mechanically compressed into a bilayer structure by Langmuir–Blodgett (LB) technology as surface pressure is exceeding the critical collapse pressure. Both monolayer and bilayer nanostructure span over hundreds of microns in both dimensions. The surface contact angle of the sample was measured by dynamic/static optical contact angle/interface tensiometer, which showed asymmetric wettability on the air side and the water side. The evolution from a monolayer to a bilayer was further tracked by an atomic force microscope. By the evaporation‐induced interfacial self‐assembly at the air–water interface, we also prepared macroscopic Janus films with a diameter of ~3.5 mm. The obtained micro/macro‐scale 2D materials have potential applications in nanoscience and biomedicine.

Design of smart autonomous solar panel with cascaded SEPIC-boost converter for high voltage renewable applications

ABSTRACT The most admired alternative to conventional energy sources is solar energy. In north-eastern regions of India, where availability of sun is unpredictable but irradiance level is high, special observation is needed to upgrade the solar collection systems. The main objective of the research work is to develop a renewable system, which can extract maximum voltage using dual axis movable surface and design a cascaded converter, which can further increase the voltage while maintaining high efficiency. The output of the smart independent self-regulating solar panel hardware model proposed in this paper is fed into a DC–DC cascaded Boost-SEPIC system for renewable-based applications. The newly created renewable system is built to move the panel so that the most voltage is extracted. The DC–DC cascaded converter receives power from the solar panel’s output. To assess the system’s effectiveness and voltage gain, a thorough circuit analysis is carried out. The converter is tested using various duty cycles. With a 50% duty ratio and 90% efficiency, the suggested converter produces a 40 V DC output from a 20 V DC input voltage from a solar panel. Results from an experimental prototype are used to verify the converter’s viability.

Modified 2.5D singular boundary methods to deal with spurious eigensolutions in exterior acoustic problems

This paper studies the problem of spurious eigensolutions in the context of the singular boundary method (SBM) formulated in the two-and-a-half-dimensional (2.5D) domain and proposes two numerical schemes to overcome this numerical difficulty. The SBM can be seen as a version of the method of fundamental solutions where the source points are located at the physical boundary. Similar to other boundary-type discretization schemes, the SBM also encounters the non-uniqueness problem at the vicinity of the eigensolutions of the corresponding interior problem. In the 2.5D domain framework, the so-called fictitious eigenfrequencies appearing in 3D problems arise in the form of spurious dispersion curves associated with propagation modes of the corresponding interior problem. The two enhanced 2.5D SBM approaches proposed in this work, based on the Burton–Miller method in one case and the dual surface method in the other, are designed to filter out the spurious eigenvalues from the simulation results and deliver accurate solutions along the wavenumber-frequency spectrum. Three benchmark examples including the radiation problems of an infinitely long cylinder under Dirichlet and Neumann boundary conditions and the radiation problem of a longitudinally infinite object with a constant star-like cross section subjected to a Dirichlet boundary condition are considered to study the proposed methods. The results demonstrate the capability of the proposed numerical schemes to successfully avoid the non-uniqueness problem when the 2.5D SBM is employed.

A new adhesion concept based on a dual surface modification for resin Ti adhesion

The objective of this resin Ti adhesion study was to compare and contrast the effect of two novel dual surface modification methods on the surface morphology, changes in surface chemistry and to evaluate their enclosed mold micro-shear bond strength variation on artificial ageing. A total amount of 168 c.p. grade 2 titanium specimens were first manually polished, then 24 of them were randomly selected as control specimens. To study the effect of dual surface modification (silicatization followed by etching), 72 polished titanium specimens were silicatized (Rocatec™ Plus, 3M ESPE, 110 μm silica-coated alumina powder) according to the manufacturer’s protocol and then 36 of the silicatized specimens were etched with a blend of HNO3–HCl at 60 °C for 2 mins. The reversed dual surface modification (etching followed by silicatization) was done for the remaining 72 titanium specimens. They were first etched with a blend of HNO3–HCl at 60 °C for 2 mins, and then 36 of the etched specimens were silicatized with the same protocol as mentioned above. As a final treatment one third of all differently modified sample groups were silanized by Monobond™ Plus (Ivoclar Vivadent), and the other third with an experimental silane primer blend, 1.0 vol% 3-acryloxypropyltrimethoxysilane + 0.3 vol% 1,2-bis-(triethoxysilyl)ethane. One third of each sample groups was left without silanization. SEM, EDX, XPS, AFM, and surface roughness profilometry were conducted to study the effects of different surface modifications. Two enclosed mold resin stubs were bonded on each surface treated titanium specimens to evaluate the enclosed mold micro-shear bond strength. The specimens were artificially aged for 1 day, 1 week, 4 weeks, and 8 weeks, followed by adhesion strength testing and failure mode analyses. SpeedCem™ (Ivoclar Vivadent) was used as resin cement. The highest surface roughness was detected on the titanium specimens, silicatized and followed by etching with and without silanization (group E), while the lowest surface roughness was observed in two groups, silanized polished titanium (group A, control) and etched polished titanium with and without silanization (group C). The surface roughness of titanium only silicatized (group B) and specimens silicatized after etching (group D) exhibited similar surface roughness, higher than groups A and C, but lower than group E. These results were supported by the SEM images and AFM analysis. The EDX and EM-μSBS analyses pointed out that specimens which had higher [Si] and [Al], exhibited higher EM-μSBS values. The highest EM-μSBS values were observed in Ti specimens which were silicatized only or those which were silicatized after etching, i.e., groups B and D. Adhesive and mixed mode of fractures were observed in the specimens after EM-μSBS tests. A novel approach of silicatized titanium surface after etching might prevent the removal of embedded SiO2 and Al2O3, allowing the formation of a durable chemical bond with a silane blend.

Micro-Thrust, Low-Fuel Consumption, and High-Precision East/West Station Keeping Control for GEO Satellites Based on Synovial Variable Structure Control

Aiming at the shortcomings of non-optimal fuel consumption and low accuracy of Geosynchronous orbit (GEO) satellites in the east/west station keeping (EWSK) at the current stage, a micro-thrust EWSK algorithm for GEO satellites based on a single-synovial surface is proposed. This algorithm has the characteristics of low fuel consumption and high control precision. However, when this algorithm performs GEO station switching under the condition of limited velocity increment, the mean longitude capture path may not be optimal, the capture time of the mean longitude is too long, and the engineering applicability is not good. In view of the above problems, a micro-thrust EWSK for GEO satellites based on dual synovial surfaces is proposed. Through the advance planning of the mean longitude, the control lag caused by the limited velocity increment is eliminated, the optimal path-planning problem of the mean longitude is solved, and the capture time of the mean longitude is greatly shortened. The two EWSK algorithms proposed in this paper have the advantages of small calculation amount, optimal fuel consumption, high precision and strong stability, which have good engineering application value.

Dual functional low surface energy coating of anti-corrosion / fouling via crosslinking polysilazane preceramic precursor incorporated with fluorine

A dual functional low surface energy coating with polysilazane preceramic precursor is developed to form a silicon-based polymeric film. The result shows that the lowest surface free energy of the fluorinated silicon-based polymeric film is about 28.43 mJ/m2 and its corrosion potential achieves 0.0899 V by the tafel polarization indicating that it has relatively low surface free energy with high corrosion resistance. The water contact angle of the silicon-based polymeric film with polysilazane preceramic precursor diluted in acetone crosslinked at 400 °C can achieve 126.8°. Polysilazane preceramic precursor incorporated with titanium dioxide, TiO2 is able to reduce the surface energy to lower than 30 mJ/m2 for anti-fouling application. Nanoindentation result shows the fluorinated silicon-based polymeric film has the higher elastic recovery rate, 77.3 % representing that fluoride dopant improves its surface toughness. The average hardness and reduced modulus of the silicon-based polymeric film are superior to that of the pure aluminum, showing that this dual functional low surface energy coating provides a relatively high surface strength with high toughness.

Dual Topology of Dirac Electron Transport and Photo-galvanic Effect in Low-dimensional Topological Insulator Superlattices.

Dual topological insulators, simultaneously protected by time-reversal symmetry and crystalline symmetry, open great opportunities to explore different symmetry-protected metallic surface states. However, the conventional dual topological states located on different facets hinders integration into planar opto-electronic/spintronic devices. Here, we construct dual topological superlattices (TSLs) Bi2 Se3 -(Bi2 /Bi2 Se3 )N with limited stacking layer number N. Angle-resolved photoelectron emission spectra of the TSLs identify the coexistence and adjustion of dual topological surface states on Bi2 Se3 facet. The existence and tunability of spin-polarized dual-topological bands with N on Bi2 Se3 facet result in an unconventionally weak antilocalization effect (WAL) with variable WAL coefficient α (maximum close to 3/2) from quantum transport experiments. Most importantly, we identify the spin-polarized surface electrons from dual topological bands exhibit circularly and linearly polarized photo-galvanic effect (CPGE and LPGE). We anticipate that the stacked dual-topology and stacking layer number controlled bands evolution provide a platform for realizing intrinsic CPGE and LPGE. Our results show that the surface electronic structure of the dual TSLs is highly tunable and well-regulated for quantum transport and photoexcitation, which shed light on engineering for opto-electronic/spintronic applications. This article is protected by copyright. All rights reserved.

A robust membrane with dual superlyophobicity for solving water-caused lubricant deterioration and water contamination

Lubricants are often contaminated by water in different ways. Water-polluted lubricants extremely accelerate wear corrosion, leading to the deterioration of lubricity performance. Recently, multiphase media superwettability has been developed to endow one surface with compatible functions, such as on-demand separation of oily wastewater. However, realizing the robustness of the dual superlyophobic surface to solve water-caused lubricant deterioration and water contamination as needed remains challenges. Herein, a robust dual superlyophobic membrane is presented to realize on-demand separation for various lubricant—water emulsions. Compared to pure lubricants, the purified lubricants have equivalent tribology performance, which are much better than that of water-polluted lubricants. The as-prepared membrane maintains dual superlyophobicity, high-efficient for water or lubricant purification, and excellent tribology performance of the purified lubricant, even after immersion in hot liquids for 24 h, multicycle separation, and sandpaper abrasion for 50 cycles. Water-polluted lubricant extremely accelerates wear corrosion to promote catalytic dehydrogenation of lubricants, generating too much harmful carbon-based debris. This work shows great guiding significance for recovering the tribology performance of water-polluted lubricants and purifying water by the dual superlyophobic membrane.

Bioinspired Under-Liquid Dual Superlyophobic Surface for On-Demand Oil/Water Separation.

Porous membranes with under-liquid dual superlyophobic properties, which are difficult to achieve because of a thermodynamic contradiction, have attracted considerable interest in the field of switchable oil/water separation. Herein, a bioinspired mesh membrane with alternating hydrophilic and hydrophobic chemical patterns on its surface that endows it with superamphiphilic and under-liquid dual superlyophobic properties is fabricated by a simple liquidus modification process. The as-prepared membrane possesses a combination of under-oil superhydrophobic and under-water superoleophobic characteristics in the absence of external stimuli. Moreover, it can effectively perform the on-demand separation of various oil/water systems, including immiscible oil/water mixtures and oil/water emulsions owing to its under-liquid dual superlyophobic properties.

Dual Imaging Single Vesicle Surface Protein Profiling and Early Cancer Detection.

Single vesicle molecular profiling has the potential to transform cancer detection and monitoring by precisely probing cancer-associated extracellular vesicles (EVs) in the presence of normal EVs in body fluids, but it is challenging due to the small EV size, low abundance of antigens on individual vesicles, and a complex biological matrix. Here, we report a facile dual imaging single vesicle technology (DISVT) for surface protein profiling of individual EVs and quantification of target-specific EV subtypes based on direct molecular capture of EVs from diluted biofluids, dual EV-protein fluorescence-light scattering imaging, and fast image analysis using Bash scripts, Python, and ImageJ. Plasmonic gold nanoparticles (AuNPs) were used to label and detect targeted surface protein markers on individual EVs with dark-field light scattering imaging at the single particle level. Monte Carlo calculations estimated that the AuNPs could detect EVs down to 40 nm in diameter. Using the DISVT, we profiled surface protein markers of interest across individual EVs derived from several breast cancer cell lines, which reflected the parental cells. Studies with plasma EVs from healthy donors and breast cancer patients revealed that the DISVT, but not the traditional bulk enzyme-linked immunosorbent assay, detected human epidermal growth factor receptor 2 (HER2)-positive breast cancer at an early stage. The DISVT also precisely differentiated HER2-positive breast cancer from HER2-negative breast cancer. We additionally showed that the amount of tumor-associated EVs was tripled in locally advanced patients compared to that in early-stage patients. These studies suggest that single EV surface protein profiling with DISVT can provide a facile and high-sensitivity method for early cancer detection and quantitative monitoring.

Ternary PtCoMo Alloy with Dual Surface Co and Mo Defects for Synergistically Enhanced Acidic Oxygen Reduction

AbstractProton exchange membrane fuel cell (PEMFC) is considered as the most promising energy conversion technology, which is hampered by the unsatisfied activity and high loading of Pt. The performance of Pt‐based catalyst toward PEMFC depends on the surface bond length of Pt−Pt, which is closely related to the surface defect engineering. Here we firstly present a ternary alloy PtCoMo nanocatalyst with dual surface Co and Mo vacancy defects (VCo−Mo−PtCoMo) that compressed the Pt−Pt bonds, thus exhibiting an outstanding activity toward oxygen reduction reaction (ORR) with a mass activity of 0.57 A mgPt−1 at 0.9 V (RHE, reversible hydrogen electrode), which is 5.2 times higher as compared with commercial Pt/C (20 wt %) in 0.1 M HClO4. The characterizations and density functional theory calculations demonstrate that the Pt−Pt bonds are significantly compressed through the dual surface defects, thus weakening the binding energy and effectively enhancing the acidic ORR performance.

On dual surfaces in Galilean 3-space

<abstract><p>In the present paper, we describe dual translation surfaces in the Galilean 3-space having the constant Gaussian and mean curvatures as well as Weingarten and linear Weingarten dual translation surfaces. We also study dual translation surfaces in $ \mathbb{G}_{3} $ under the condition $ \Delta ^{II}r = \lambda _{i}r_{i} $, where $ \lambda _{i}\in R $ and $ \Delta ^{II} $ denotes the Laplacian operator respect to the second fundamental form.</p></abstract>

Enhanced Frequency Stability of SAW Yarn Tension Sensor by Using the Dual Differential Channel Surface Acoustic Wave Oscillator.

This paper presents a 60 MHz surface acoustic wave (SAW) yarn tension sensor incorporating a novel SAW oscillator with high-frequency stability. A SAW delay line was fabricated on ST-X quartz substrate using the unbalanced-split electrode and bi-directional engraving slots. The dual differential channel delay linear acoustic surface wave oscillator is designed and implemented to test yarn tension, which can effectively remove the interference of temperature, humidity, and other peripheral factors through differential design. The yarn tension sensor using the surface acoustic wave has high-precision characteristics, and the SAW delay line oscillator is designed to ensure the test system’s stable operation. The effect of time and tension on oscillator frequency stability is studied in detail, and the single oscillator and the dual differential channel system were tested, respectively. After using the dual differential channel system, the short-term frequency stability from is reduced from 1.0163 ppm to 0.17726 ppm, the frequency accuracy of the tension sensor is improved from 134 Hz to 27 Hz, and the max frequency jump steady is reduced from 2.2395 ppm to 0.45123 ppm.

Active Damping Control Method for Different Dual-Parallel-SPMSM Systems with Single Inverter

This paper presents a stabilization method for different dual parallel surface permanent magnet synchronous motor (SPMSM) systems with a single inverter. When a single inverter drives two synchronous motors, disturbance can cause a torque difference between the two motors. This can cause the motor's electrical and mechanical resonance. Several damping control methods have been proposed to suppress such resonance. However, such methods consider that the parameters of the two motors are identical. When a single inverter controls two motors with different parameters, the damping control performance deteriorates. Besides, the motor's resonance sound and current ripple increase. To address these problems, this paper proposes a control method for dual-parallel-SPMSM drive systems with a single inverter.

Dual mode antibacterial surfaces based on Prussian blue and silver nanoparticles.

Prussian Blue (PB) is an inexpensive, biocompatible, photothermally active material. In this paper, self-assembled monolayers of PB nanoparticles were grafted on a glass surface, protected with a thin layer of silica and decorated with spherical silver nanoparticles. This combination of a photothermally active nanomaterial, PB, and an intrinsically antibacterial one, silver, leads to a versatile coating that can be used for medical devices and implants. The intrinsic antibacterial action of nanosilver, always active over time, can be enhanced on demand by switching on the photothermal effect of PB using near infrared (NIR) radiation, which has a good penetration depth through tissues and low side effects. Glass surfaces functionalized by this layer-by-layer approach have been characterized for their morphology and composition, and their intrinsic and photothermal antibacterial effect was studied against Gram+ and Gram- planktonic bacteria.

Nanoarchitectonics on Z-scheme and Mott-Schottky heterostructure for photocatalytic water oxidation via dual-cascade charge-transfer pathways.

The bottleneck for water splitting to generate hydrogen fuel is the sluggish oxidation of water. Even though the monoclinic-BiVO4 (m-BiVO4)-based heterostructure has been widely applied for water oxidation, carrier recombination on dual surfaces of the m-BiVO4 component have not been fully resolved by a single heterojunction. Inspired by natural photosynthesis, we established an m-BiVO4/carbon nitride (C3N4) Z-scheme heterostructure based on the m-BiVO4/reduced graphene oxide (rGO) Mott-Schottky heterostructure, constructing the face-contact C3N4/m-BiVO4/rGO (CNBG) ternary composite to remove excessive surface recombination during water oxidation. The rGO can accumulate photogenerated electrons from m-BiVO4 through a high conductivity region over the heterointerface, with the electrons then prone to diffuse along a highly conductive carbon network. In an internal electric field at the heterointerface of m-BiVO4/C3N4, the low-energy electrons and holes are rapidly consumed under irradiation. Therefore, spatial separation of electron-hole pairs occurs, and strong redox potentials are maintained by the Z-scheme electron transfer. These advantages endow the CNBG ternary composite with over 193% growth in O2 yield, and a remarkable rise in ·OH and ·O2- radicals, compared to the m-BiVO4/rGO binary composite. This work shows a novel perspective for rationally integrating Z-scheme and Mott-Schottky heterostructures in the water oxidation reaction.

Dual broad Band-Stop Polarization-Insensitive and scanning angle stability Frequency Selective Surface

In this communication, broad dual band-stop characteristics, polarization–insensitive FSS with large scanning angle stability is developed. A simple square ring with T – shaped resonator is implemented to develop dual-band characteristics. L – Shaped and circular ring metallic layers are incorporated on the proposed unit cell FSS to get optimum polarization insensitive dual-stop frequency bands. The proposed FSS is fabricated on one side of a single layer FR4 substrate. The smallest dimension of the unit cell is 0.1λ0×0.1λ0×0.01λ0 (10.2mm×10.2mm×1.6mm), where λ0 is the free space wavelength at the lower cutoff frequency of 1.97 GHz. The proposed −10 dB dual-band FSS has rejection characteristics over the frequency ranges of (1.97 GHz – 4.06 GHz) and (8 GHz – 12.3 GHz). The achieved −20 dB bandwidth are (2.74 GHz – 3.43 GHz) and (9.5 GHz – 11 GHz) under the TE mode. Equivalent circuit model is implemented to ensure the validity of the work. The fabricated FSS can be used to shield EM wave for S–band and X–band applications.

Boosting bone cell growth using nanofibrous carboxymethylated cellulose and chitosan on titanium dioxide nanotube array with dual surface charges as a novel multifunctional bioimplant surface

One of the most vital aspects of the orthopedic implant field has been the development of multifunctional coatings that improve bone-implant contact while simultaneously preventing bacterial infection. The present study investigates the fabrication and characterization of multifunctional polysaccharides, including carboxymethyl cellulose (CMCn) and carboxymethyl chitosan nanofibers (CMCHn), as a novel implant coating on titania nanotube arrays (T). Field emission scanning electron microscopy (FESEM) images revealed a nanofibrous morphology with a narrow diameter for CMCn and CMCHn, similar to extracellular matrix nanostructures. Compared to the T surface, the roughness of CMCn and CMCHn samples increased by over 250 %. An improved cell proliferation rate was observed on CMCHn nanofibers with a positively charged surface caused by the amino groups. Furthermore, in an antibacterial experiment, CMCn and CMCHn inhibited bacterial colony formation by 80 % and 73 %, respectively. According to the results, constructed modified CMCn and CMCHn increased osteoblast cell survival while inhibiting bacterial biofilm formation owing to their surface charge and bioinspired physicochemical properties.

Remarkable Reduction in IG with an Explicit Investigation of the Leakage Conduction Mechanisms in a Dual Surface-Modified Al2O3/SiO2 Stack Layer AlGaN/GaN MOS-HEMT.

We demonstrated the performance of an Al2O3/SiO2 stack layer AlGaN/GaN metal-oxide semiconductor (MOS) high-electron-mobility transistor (HEMT) combined with a dual surface treatment that used tetramethylammonium hydroxide (TMAH) and hydrochloric acid (HCl) with post-gate annealing (PGA) modulation at 400 °C for 10 min. A remarkable reduction in the reverse gate leakage current (IG) up to 1.5×10-12 A/mm (@ VG = -12 V) was observed in the stack layer MOS-HEMT due to the combined treatment. The performance of the dual surface-treated MOS-HEMT was significantly improved, particularly in terms of hysteresis, gate leakage, and subthreshold characteristics, with optimized gate annealing treatment. In addition, an organized gate leakage conduction mechanism in the AlGaN/GaN MOS-HEMT with the Al2O3/SiO2 stack gate dielectric layer was investigated before and after gate annealing treatment and compared with the conventional Schottky gate. The conduction mechanism in the reverse gate bias was Poole-Frankel emission for the Schottky-gate HEMT and the MOS-HEMT before annealing. The dominant conduction mechanism was ohmic/Poole-Frankel at low/medium forward bias. Meanwhile, gate leakage was governed by the hopping conduction mechanism in the MOS-HEMT without gate annealing modulation at a higher forward bias. After post-gate annealing (PGA) treatment, however, the leakage conduction mechanism was dominated by trap-assisted tunneling at the low to medium forward bias region and by Fowler-Nordheim tunneling at the higher forward bias region. Moreover, a decent product of maximum oscillation frequency and gate length (fmax × LG) was found to reach 27.16 GHz∙µm for the stack layer MOS-HEMT with PGA modulation. The dual surface-treated Al2O3/SiO2 stack layer MOS-HEMT with PGA modulation exhibited decent performance with an IDMAX of 720 mA/mm, a peak extrinsic transconductance (GMMAX) of 120 mS/mm, a threshold voltage (VTH) of -4.8 V, a higher ION/IOFF ratio of approximately 1.2×109, a subthreshold swing of 82 mV/dec, and a cutoff frequency(ft)/maximum frequency of (fmax) of 7.5/13.58 GHz.