Metal Surface Research Articles

A compliant metastructure design with reconfigurability up to six degrees of freedom

Abstract Compliant mechanisms with reconfigurable degrees of freedom are gaining attention in the development of kinesthetic haptic devices, robotic systems, and mechanical metamaterials. However, available devices exhibit limited programmability and form-customizability, restricting their versatility. To address this gap, we propose a metastructure concept featuring reconfigurable motional freedom and tunable stiffness, adaptable to various form factors and applications. These devices incorporate passive flexures and actively stiffness-changing rods to modify kinematic freedom. A rational design pipeline informs the flexures’ topological arrangements, geometric parameters, and control signals based on targeted mobilities, enabling the creation of unitary joints with up to six degrees of freedom. Our demonstrative application examples include a wrist device that has an effective stiffness of 0.370 Nm/deg (unlocked state, 5% displacement) to 2.278 Nm/deg (locked state, 1% displacement) to enable dynamic joint mobility control, a haptic thimble device (2.27-52.815 Nmm−1 at 1% displacement) that mimics the sensation of touching physical materials ranging from soft gel to metal surfaces, and a wearable device composed of multiple joints tailored for the arm and hand to augment haptic experiences or facilitate muscle training. We believe the presented method can help democratize compliant metastructures development and expand their versatility for broader contexts.

A functional integral approach to magnon mediated plasmon friction

In this paper, we discuss quantum friction in a system formed by two metallic surfaces separated by a ferromagnetic intermedium of a certain thickness. The internal degrees of freedom in the two metallic surfaces are assumed to be plasmons, while the excitations in the intermediate material are magnons, modeling plasmons coupled to magnons. During relative sliding, one surface moves uniformly parallel to the other, causing friction in the system. By calculating the effective action of the magnons, we can determine the particle production probability, which shows a positive correlation between the probability and the sliding speed. Finally, we derive the frictional force of the system, with both theoretical and numerical results indicating that the friction, like the particle production probability, also has a positive correlation with the speed.

Advances, Challenges, and Opportunities in Plasmonic Nanogap-Enhanced Raman Scattering with Nanoparticles.

Surface-enhanced Raman scattering has been widely used for molecular/material characterization and chemical and biological sensing and imaging applications. In particular, plasmonic nanogap-enhanced Raman scattering (NERS) is based on the highly localized electric field formed within the nanogap between closely spaced metallic surfaces to more strongly amplify Raman signals than the cases with molecules on metal surfaces. Nanoparticle-based NERS offers extraordinarily strong Raman signals and a plethora of opportunities in sensing, imaging and many different types of biomedical applications. Despite its potential, several challenges still remain for NERS to be widely useful in real-world applications. This Perspective introduces various plasmonic nanogap configurations with nanoparticles, discusses key advances and critical challenges while addressing possible misunderstandings in this field, and provides future directions for NERS to generate stronger, more uniform, and stable signals over a large number of structures for practical applications.

Enhancing corrosion resistance in HCl environments: Comparative efficacy of a conjugated 3ph-Schiff base versus benzotriazole

This research addresses the need for effective corrosion inhibitors in industrial applications, evaluating the performance of 4-nitro-2-(((1E,2E)-3-phenylallylidene)amino)aniline (noted as 3ph-Schiff base) as a corrosion inhibitor in comparison to benzotriazole (BTA) in a high-concentration 3 M HCl environment. Unlike studies conducted in lower concentrations (e.g. 0.1 and 1 M), this study aims to assess inhibitor performance under more aggressive conditions. Rigorous methods, including Tafel polarisation, electrochemical impedance spectroscopy (EIS), and mass loss measurements, revealed variations in inhibition efficiency (IE). Polarisation data indicated that 3ph-Schiff base at 0.3% (approximately 8.96 mM) achieved a maximum IE of 99.5%, surpassing BTA at the same concentration (approximately 25.2 mM), which recorded an IE of 96.9%. Meanwhile, EIS analysis yielded slightly lower IE values, with 3ph-Schiff base reaching 90.21% and BTA 67.39%, reflecting the complementary nature of these methods. The corrosion inhibition mechanism of 3ph-Schiff base is attributed to strong adsorption on the metal surface, where amino (NH2) and nitro (NO2) groups promote stable complex formation with metal ions, enhancing electron donation and forming a protective layer that blocks corrosive agents. Scanning electron microscopy and elemental mapping confirm uniform nitrogen and carbon surface coverage, integral to the protective layer. This layer acts as both a physical barrier and an electrochemical passivator, effectively reducing anodic and cathodic reactions. The combined effects of adsorption, physical blocking and passivation underscore the 3ph-Schiff base's superior performance as a corrosion inhibitor in acidic environments.

Machine Learning Committee Neural Network Potential Energy Surfaces for Two-Dimensional Metal–Organic Frameworks

Machine Learning Committee Neural Network Potential Energy Surfaces for Two-Dimensional Metal–Organic Frameworks

The Planar Si(IV) of Bis(catecholato)silane on a Metal Surface Induced by a Surface Constraint

The Planar Si(IV) of Bis(catecholato)silane on a Metal Surface Induced by a Surface Constraint

Analysis of Refractive Index Sensing Properties of a Hybrid Hollow Cylindrical Tetramer Array

In recent years, metal surface plasmon resonance sensors and dielectric guided-mode resonance sensors have attracted the attention of researchers. Metal sensors are sensitive to environmental disturbances but have high optical losses, while dielectric sensors have low losses but limited sensitivity. To overcome these limitations, hybrid resonance sensors that combine the advantages of metal and dielectric were proposed to achieve a high sensitivity and a high Q factor at the same time. In this paper, a hybrid hollow cylindrical tetramer array was designed, and the effects of the hole radius, external radius, height, period, incidence angle, and polarization angle of the hollow cylindrical tetramer array on the refractive index sensing properties were quantitatively analyzed using the finite difference time domain method. It is found that the position of the resonance peaks can be freely tuned in the visible and near-infrared regions, and a sensitivity of up to 542.8 nm/RIU can be achieved, with a Q factor of 1495.1 and a figure of merit of 1103.3 RIU−1. The hybrid metal–dielectric nanostructured array provides a possibility for the realization of high-performance sensing devices.

Comparative Study of Volatile Corrosion Inhibitors in Various Electrochemical Setups

Volatile corrosion inhibitors (VCIs) are increasingly used in closed systems affected by atmospheric corrosion. In order to achieve a satisfactory level of protection, an inhibitor must be present in a sufficient concentration that should be determined experimentally. Electrochemical measurements are indispensable in corrosion studies examining the protection efficiency of corrosion inhibitors. Volatile corrosion inhibitors are often examined by electrochemical measurements conducted in a bulk of electrolyte, although they protect metal surfaces from atmospheric corrosion where a thin film of electrolyte is present. The aim of this work is to study the protection of carbon steel by two VCIs on different types of electrodes that allow electrochemical tests in a thin electrolyte film and to compare the obtained results with those obtained in a larger volume in a classical electrochemical cell. For this purpose, disc and comb-like electrodes are used. The investigations are carried out in two corrosion media simulating either a marine or urban polluted atmosphere. Studies are performed on low-carbon S235JR steel, which is typically used for crude oil tank bottoms that often suffer from atmospheric corrosion and are increasingly protected by VCIs. Two benzoate-based VCIs recommended for such application are selected for this study.

Lubricating Performance of Lanzhou Lily Crude Extract as Natural Additive

Due to environmental concerns and multifunctional requirements, natural additives are a promising alternative to traditional enhancers like metal nanoparticles. Lanzhou lily crude extract (LLCE) was investigated as an additive in PEG400 base oil. Firstly, different contents of LLCE as an additive notably improved physiochemical properties, such as thermal stability, viscosity, and the viscosity index. With 5–10 wt.% of LLCE added in PEG400, the thermal degradation temperature increased by 37.3–49.5 °C. Secondly, the addition of LLCE significantly reduced the friction coefficient and wear rate of the steel disc at 50–150 N compared to pure PEG400 base oil with a reduction degree of up to 30% and 92%. The optimum additive content was 7 wt.%, and further increasing the content of the additive did not bring about obvious improvements, even worsening the product in some cases. Thirdly, the lower friction coefficient and wear rate achieved through the addition of LLCE may be due to the higher viscosity facilitating a thicker lubricating film and the higher polarity providing better chemical affinity with the metallic surface. In summary, LLCE is a promising additive that significantly improves the physicochemical properties and lubricating performance of PEG400 base oil.

Plasmon-Enhanced CO2 Reduction to Liquid Fuel via Modified UiO-66 Photocatalysts

Metal–organic frameworks (MOFs) have emerged as versatile materials with remarkably high surface areas and tunable properties, attracting significant attention for various applications. In this work, the modification of a UiO-66 MOF with metal nanoparticles (NPs) is investigated for the purpose of enhancing its photocatalytic activity for CO2 reduction to liquid fuels. Several NPs (Au, Cu, Ag, Pd, Pt, and Ni) were loaded into the UiO-66 framework and employed as photocatalysts. The synergistic effects of plasmonic resonance and MOF characteristics were investigated to improve photocatalytic performance. The synthesized materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), confirming the successful integration of metal NPs onto the UiO-66 framework. Morphological analysis revealed distinct distributions and sizes of NPs on the UiO-66 surface for different metals. Photocatalytic CO2 reduction experiments demonstrated enhanced activity of plasmonic MOFs, yielding methanol and ethanol. The findings revealed by this study provide valuable insights into tailoring MOFs for improved photocatalytic applications through the incorporation of plasmonic metal nanoparticles.

First-Principle Insights into Positive Triboelectrification of Polyoxymethylene Through Homolytic Bond Rupture

Understanding the mechanism underlying triboelectrification (TE) in polymers is crucial for developing cheap and effective triboelectric nanogenerators. Finding out how a polymer becomes tribopositive is especially relevant, as most polymers tend to charge negatively, reducing the power output and the range of applications. Thus far, it has remained unclear whether TE in polymers is to be attributed to homolytic ion transfer, heterolytic material transfer, or electronic transfer. Investigating the triboelectrification mechanism of polyoxymethylene by first-principle investigations, this study reveals a novel pathway driven by homolytic bond rupture. Our study demonstrates that the homolytic cleavage of a C–H bond upon contact with a metal surface drives a rearrangement in the oxidation state of the carbon atom, leading its dangling bond to cede an electron to the countersurface, leading to significant positive charging of the POM. This mechanism aligns with the triboelectric series and experimental observations. These insights suggest that TE mechanisms can be more complicated than heterolytic material transfer, depending on material-specific composition and chemistry. This study potentially paves the way for designing materials with tailored triboelectric properties for enhanced nanogenerator performance.

Current-induced circular dichroism on metallic surfaces: A first-principles study

Current-induced circular dichroism on metallic surfaces: A first-principles study

Maximizing H2 Production from a Combination of Catalytic Partial Oxidation of CH4 and Water Gas Shift Reaction

A single-bed and dual-bed catalyst system was studied to maximize H2 production from the combination of partial oxidation of CH4 and water gas shift reaction. In addition, the different types of catalysts, including Ni, Cu, Ni-Re, and Cu-Re supported on gadolinium-doped ceria (GDC) were investigated under different operating conditions of temperature (400–650 °C). Over Ni-based catalysts, methane can easily dissociate on a Ni surface to give hydrogen and carbon species. Then, carbon species react with lattice oxygen of ceria-based material to form CO. The addition of Re to Ni/GDC enhances CH4 dissociation on the Ni surface and increases oxygen storage capacity in the catalyst, thus promoting carbon elimination. In addition, the results showed that a dual-bed catalyst system exhibited catalytic activity better than a single-bed catalyst system. The dual-bed catalyst system, by the combination of 1%Re4%Ni/GDC as a partial oxidation catalyst and 1%Re4%Cu/GDC as a water gas shift catalyst, provided the highest CH4 conversion and H2 yield. An addition of Re onto Ni/GDC and Cu/GDC caused an increase in catalytic performance because Re addition could improve the catalyst reducibility and increase metal surface area, as more of their surface active sites are exposed to reactants.

Plasmon-Enhanced Luminescence of Gold Nanoclusters by Using Silver and Gold Metal Nanostructures.

Plasmonic materials can be utilized as effective platforms to enhance luminescent signals of luminescent metal nanoclusters (LMNCs). Both surface enhanced fluorescence (SEF) and shell-isolated nanoparticle-enhanced fluorescence (SHINEF) strategies take advantage of the localized and increased external electric field created around the plasmonic metal surface when excited at or near their characteristic plasmonic resonance. In this context,we present an experimental and computational study of different plasmonic composites, (Ag) Ag@SiO2 and (Au) Au@SiO2 nanoparticles, which were used to enhance the luminescent signal of Au nanoclusters coated with glutathione (GSH) molecule (Au25GSH NCs). This specific LMNC has recently attracted particular interest due to its luminescent response and characteristic photostability. Our study presents a wide characterization of the optical and morphologic features of the synthetized particles: plasmonic metal nanostructures and Au25GSH NCs through different experimental techniques including UV-Visible, IR, luminescentspectroscopies, along with TEM and AFM microscopies. Additionally, we have carried out computational simulations based on time-dependent density functional theory (TD-DFT) and classical electrodynamics simulation based on Mie Theory to support our experimental findings. In this study, we report up to 3-fold luminescence enhancement of Au25GSH NCs which is mainly attributed to slow dynamics SEF.

Plasma Treatment of Metal Surfaces for Enhanced Bonding Strength of Metal–Polymer Hybrid Structures

The adhesion between metals and polymers plays a pivotal role in numerous industrial applications, especially within the automotive and aerospace sectors, where there is a growing demand for materials that are both lightweight and durable. This study introduces an innovative technique to improve the adhesion between a metal and a polymer in hybrid structures through the synergistic use of anodization and plasma treatment. By forming a nanoporous oxide layer on aluminum surfaces, anodization enhances the interface for polymer binding. Plasma treatment further augments the surface properties by increasing the concentration of functional groups, thus allowing better polymer infiltration during the 3D printing process. Comprehensive analyses, including X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, and contact angle measurements confirm the substantial enhancement in the bonding strength achieved through this method. Additionally, cross-sectional analysis via focused ion-beam etching provides a detailed view of polymer integration into the treated layers. The findings suggest significant potential for these surface modification strategies to advance the development of lightweight, robust composites suitable for use in sectors such as automotive, aerospace, and consumer electronics.

Sulfur functionalized diamondoid phosphines enable building nanocomposites interfacing sp3-carbon and gold nanolayers.

Interfacing metal frameworks with carbon-based materials is attractive for the bottom-up construction of nanocomposite functional materials. The stepwise layering of difunctionalized diamantanes and gold metal from physical and chemical vapor deposition for the preparation of nanocomposites inverts the conventional preparation of metal-organic frameworks (MOFs) and self-assemblies, where the metal is introduced first, and this method delivers metal surfaces with modified properties originating from the sp3-carbon core. However, appropriate diamondoid candidates for such an approach are rare. By the mild chemical vapor deposition of the organometallic complex MeAuPMe3, gold coating is achieved on a diamantane SP(V) sulfide primary phosphine diamantanol 2. This later leads to sulfide and polysulfide surface rearrangement and provides a suitable substrate for metal-organic nanocomposite formation through a fully-dry vapor process, with the advantage, in contrast to the P(III) primary phosphine phosphinodiamantanol 1, of being resistant to uncontrolled oxidation at phosphorus during physical vapor deposition (PVD) and chemical vapor deposition (CVD) processing.

Managing thrombosis risk in flow diversion: A review of antiplatelet approaches.

Flow diversion is a transformative approach in neurointerventional surgery for intracranial aneurysms that relies heavily on effective antiplatelet therapy. The ideal approach, including the timing of treatment, the use of dual antiplatelet therapy (DAPT), and the number of flow-diverter devices to use, remains unknown. DAPT, which combines aspirin with a thienopyridine like clopidogrel, prasugrel, or ticagrelor, is the standard regimen, balancing thromboembolic protection and hemorrhagic risk. The variable response to clopidogrel, influenced by genetic polymorphisms, necessitates personalized treatment strategies. Alternatives like prasugrel and ticagrelor provide superior efficacy in specific scenarios but require careful consideration of bleeding risks and costs. Platelet function testing plays a critical role in tailoring antiplatelet regimens for patients undergoing flow diversion for intracranial aneurysms. Special considerations were made for ruptured aneurysms, and the implications of the extensive metallic surface of flow diverters on platelet activation were noted. Emerging technologies such as drug-eluting flow diverters and reversal agents for P2Y12 inhibitors suggest a potential shift toward more refined antiplatelet strategies in the future. Personalized medication that is compatible with the stent structure and metal is essential for optimizing patient outcomes in cerebral flow diversion procedures. Ongoing research and multidisciplinary collaboration will be key in refining these strategies and enhancing the safety and efficacy of neurointerventional treatments.

Geometric Effects on C-C Coupling of Aryl-Carbenes under 2D Confinement.

It is well established that the confinement of reactants to two dimensions influences their reactivity. However, such confinement is often dominated by charge transfer effects between the reactants and the confining walls, in particular if the walls are conductive. Also, the reactivity of carbenes on metal surfaces is significantly affected by the charge transfer between the carbene and the metal, rendering the carbene more nucleophilic or electrophilic. Here, we investigate the geometrical effects of 2D confinement without an influence of the supporting metal for a photoinduced reaction of an aryl carbene on an ionic decoupling layer. We demonstrate the decoupling concept for the C-C coupling of 3-methoxy-9-fluorenylidene (C14H10O) on a NaBr(100) bilayer on Ag(111). We combine scanning tunneling microscopy with infrared reflection absorption spectroscopy to follow the photoinduced C-C coupling of the carbene from its diazo-protected precursor in two dimensions. Our study demonstrates that the NaBr decoupling bilayer efficiently suppresses the effects of the metal surface, facilitating carbene chemistry under geometrical confinement.

Vacuum DC breakdown characteristics between grid electrodes with ion sputtering

Abstract In ion thrusters, grid electrodes are biased at high voltage to extract and accelerate ions. However, they are susceptible to vacuum breakdown which considerably undermines the ion thruster performance. To optimize the grid electrode design and improve the ion thruster longevity, the impact of ion sputtering on the vacuum DC breakdown characteristics of grid electrodes are systemically examined. The adopted seven-aperture grid electrodes are made of three materials including molybdenum, graphite, and stainless steel, which are exposed to Ar⁺ and Xe⁺ sputtering at energies of 400 eV and 1000 eV for durations ranging from 0.5 to 8 hours. It is found that the initial breakdown voltage, which means the first breakdown voltage after sputtering, generally decreased regardless of the electrode material as the sputtering time increased. However, the breakdown voltage rapidly increases with more repeated discharges. Each kind of electrode material demonstrates unique responses to ion sputtering and breakdowns. In comparison with metal electrodes, the graphite surface relatively easy to appear defects but exhibites the least insulation degradation. The metal surface remains relatively smooth, but breakdown voltage is significantly affected, with electrode materials such as stainless steel failing to recover to their initial insulation levels. Xe⁺ sputtering leads to greater breakdown voltage fluctuations during repeated discharges due to higher sputtering yield. Dark current is measured, and field enhancement factor is calculated to reveal correlations between local electric field and the breakdown voltage. Furthermore, micro particles are identified as major contributor to the first few times breakdown. Based on above observations, two kinds of distinct discharge mechanisms, including the cascade discharge induced by micro particles and the discharge induced by field emission are proposed to interpret experimental data.

Conformational Selectivity and Chiral Self-Assembly Structures of Crown Ethers on Metal Surfaces.

Crown ethers (CEs), macrocyclic polyethers, have attracted significant attention in supramolecular chemistry. It is known that they have many isomers due to their flexibility. It is challenging to select some exact conformation and tune the following self-assembly structure of CEs, and it has rarely been reported to date. Herein, by choosing 18-crown-6-ether and dibenzo-18-crown-6-ether for study, we report an effective stereoisomeric selectivity of CEs by a strategy of both chemical modification and CEs hosting Na/K ions. The conformational difference in CEs can further tune the molecular interactions, resulting in the chiral self-assembly structures of CEs. By the combination of scanning tunneling microscopy, density functional theory, and X-ray photoelectron spectroscopy, this study reveals the underlying mechanism of CEs in both conformational selectivity and the formation of chiral assembly structures.