Surfaces

29 pages, 4009 KB

Open AccessArticle

Plant-Mediated Synthesis of Electrocatalytically Active Cd–Cs Mixed Oxide Nanocomposites and Their Multifunctional Antioxidant and Anticorrosive Performance

by Shivani Naik, Ruchi Bharti, Renu Sharma, Sónia A. C. Carabineiro and Manas Sutradhar

Surfaces 2025, 8(4), 91; https://doi.org/10.3390/surfaces8040091 - 17 Dec 2025

Viewed by 627

Abstract

Mild steel readily corrodes in acidic environments, and most industrial corrosion inhibitors are synthetic, often toxic, and environmentally harmful. In this study, electrocatalytically active Cd–Cs mixed oxide nanocomposites were synthesized via a green route using an aqueous extract of Trachyspermum ammi (ajwain) seeds [...] Read more.

Mild steel readily corrodes in acidic environments, and most industrial corrosion inhibitors are synthetic, often toxic, and environmentally harmful. In this study, electrocatalytically active Cd–Cs mixed oxide nanocomposites were synthesized via a green route using an aqueous extract of Trachyspermum ammi (ajwain) seeds as a natural reducing, stabilizing, and capping agent. This eco-friendly method eliminates harsh chemicals while producing nanomaterials with active surfaces capable of facilitating electron transfer and scavenging free radicals. Incorporation of cesium introduces basic, electron-rich sites on the Cd–Cs oxide surface, serving as inhibition promoters that enhance charge transfer at the metal/electrolyte interface and assist in the formation of an adsorbed protective film on steel. The nanocomposites were optimized by adjusting precursor ratios, pH, temperature, and reaction time, and were characterized by UV–Vis, FTIR, XRD, SEM–EDS, HR-TEM EDS, BET, DLS, XPS, and zeta potential analyses. Strong antioxidant activity in ABTS and DPPH assays confirmed efficient catalytic quenching of reactive radicals. Corrosion inhibition potential, evaluated by using potentiodynamic polarization, electrochemical impedance spectroscopy, and gravimetric analysis in 0.5 M HCl, shows an inhibition efficiency of 90–91%. This performance is associated with an electrocatalytically active, adsorbed barrier layer that suppresses both anodic dissolution and cathodic hydrogen evolution, which depicts mixed-type inhibition. Overall, the biosynthesized Cd–Cs mixed oxide nanocomposites function as promising green synthesized nanomaterial with dual antioxidant and corrosion-inhibiting functions, underscoring their potential for advanced surface engineering and corrosion protection. Full article

(This article belongs to the Special Issue Recent Advances in Catalytic Surfaces and Interfaces, 2nd Edition)

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13 pages, 2781 KB

Open AccessArticle

Comparative Study on Cation Adsorption and Thermodynamic Characteristics of Clay Minerals in Electrolyte Solutions

by Jiazhong Wu, Heshu Hu, Shuke Zhao, Yisong Li, Kun Zhao, Minghui Zhang and Bin Ding

Surfaces 2025, 8(4), 90; https://doi.org/10.3390/surfaces8040090 - 15 Dec 2025

Viewed by 682

Abstract

The interaction between clay minerals and electrolyte solutions critically affects waterflooding efficiency in enhanced oil recovery (EOR). This study systematically investigated the adsorption and thermodynamic properties of montmorillonite, illite, and kaolinite in different cationic solutions (K⁺, Na⁺, Ca²⁺ [...] Read more.

The interaction between clay minerals and electrolyte solutions critically affects waterflooding efficiency in enhanced oil recovery (EOR). This study systematically investigated the adsorption and thermodynamic properties of montmorillonite, illite, and kaolinite in different cationic solutions (K⁺, Na⁺, Ca²⁺, Mg²⁺), integrating adsorption isotherm analysis with immersion calorimetry for the first time. Montmorillonite showed the highest adsorption capacity, with the cation affinity following K⁺ > Na⁺ > Ca²⁺ > Mg²⁺. The highest immersion enthalpy was observed in KCl solution, indicating the dominant roles of ionic radius and solvation energy. Cation adsorption induced deformation of clay lamellae and modification of Si-O and Al-OH groups. These findings suggest that optimizing injected ion composition can enhance reservoir stability and waterflood performance, providing thermodynamic insights for EOR process optimization. Full article

(This article belongs to the Special Issue Advances in Solid–Liquid Interface Science: From Fundamentals to Applications)

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15 pages, 1655 KB

Open AccessArticle

The Effect of Co/TiN Interfaces on Co Interconnect Resistivity

by Poyen Shen, Sanzida Rahman, Daniel M. Syracuse and Daniel Gall

Surfaces 2025, 8(4), 89; https://doi.org/10.3390/surfaces8040089 - 13 Dec 2025

Viewed by 990

Abstract

Electron transport measurements on Co/TiN multilayers are employed to explore the effect of TiN layers on Co resistivity. For this, 50 nm thick multilayer stacks containing N = 1–10 individual Co layers that are separated by 1 nm thick TiN layers are sputter [...] Read more.

Electron transport measurements on Co/TiN multilayers are employed to explore the effect of TiN layers on Co resistivity. For this, 50 nm thick multilayer stacks containing N = 1–10 individual Co layers that are separated by 1 nm thick TiN layers are sputter deposited on SiO₂/Si(001) substrates at 400 °C. X-ray diffraction and reflectivity measurements indicate a tendency for a 0001 preferred orientation, an X-ray coherence length of 13 nm that is nearly independent of N, and an interfacial roughness that increases with N. The in-plane multilayer resistivity ρ increases with increasing N = 1–10, from ρ = 14.4 to 36.6 µΩ-cm at room temperature and from ρ = 11.2 to 19.4 µΩ-cm at 77 K. This increase is due to a combination of increased electron scattering at interfaces and grain boundaries, as quantified using a combined Fuchs–Sondheimer and Mayadas–Shatzkes model. The analysis indicates that a decreasing thickness of the individual Co layers d_Co from 50 to 5 nm causes not only an increasing resistivity contribution from Co/TiN interface scattering (from 9 to 88% with respect to the room-temperature bulk resistivity) but also an increasing (39 to 154%) grain boundary scattering contribution, which exacerbates the resistivity penalty due to the TiN liner. These results are supported by Co/TiN bilayer and trilayer structures deposited on Al₂O₃ (0001) at 600 °C. Interfacial intermixing causes Co₂Ti and Co₃Ti alloy phase formation, an increase in the contact resistance, a degradation of the Co crystalline quality, and a 2.3× higher resistivity for Co deposited on TiN than Co directly deposited on Al₂O₃(0001). The overall results show that TiN liners cause a dramatic increase in Co interconnects due to diffuse surface scattering, interfacial intermixing/roughness, and Co grain renucleation at Co/TiN interfaces. Full article

(This article belongs to the Special Issue Surface Engineering of Thin Films)

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19 pages, 2621 KB

Open AccessArticle

Balancing Hydrophobicity and Water-Vapor Transmission in Sol–Silicate Coatings Modified with Colloidal SiO₂ and Silane Additives

by Dana Němcová, Klára Kobetičová, Petra Tichá, Ivana Burianová, Dana Koňáková, Pavel Kejzlar and Martin Böhm

Surfaces 2025, 8(4), 88; https://doi.org/10.3390/surfaces8040088 - 29 Nov 2025

Viewed by 849

Abstract

This study investigates the optimization of sol–silicate façade coatings modified with colloidal silica and a silane-based hydrophobizing additive to enhance hydrophobicity while maintaining a high water-vapor transmission rate (V). The effects of the binder ratio between potassium water glass (WG) and colloidal silica [...] Read more.

This study investigates the optimization of sol–silicate façade coatings modified with colloidal silica and a silane-based hydrophobizing additive to enhance hydrophobicity while maintaining a high water-vapor transmission rate (V). The effects of the binder ratio between potassium water glass (WG) and colloidal silica (CS), the type of colloidal silica (unmodified or epoxy-silanized), and the concentration of the hydrophobizing additive (HA) were systematically evaluated. Water-vapor transmission was determined according to EN ISO 7783, and surface wettability was measured before and after accelerated UV-A aging. Dynamic viscosity was monitored for two years to assess long-term storage stability. The optimized formulation contained 7 wt % potassium water glass, 15 wt % colloidal silica, and 1 wt % hydrophobizing additive. It exhibited stable viscosity over time (≈19,000 mPa·s after six months), high water-vapor transmission (V > 6700 g·m⁻²·d⁻¹, class V1), and an initial contact angle of 118°, which decreased only moderately after UV-A exposure. Coatings containing epoxy-silanized colloidal silica showed slightly lower transmission but still remained within the high V range suitable for vapor-open façade systems. The results confirm that balanced sol–silicate systems can combine durable hydrophobicity with long-term rheological and functional stability. Full article

(This article belongs to the Special Issue Surface Science: Polymer Thin Films, Coatings and Adhesives (2nd Edition))

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21 pages, 2296 KB

Open AccessArticle

Engineering Porous Biochar for Electrochemical Energy Storage

by Cheikh Ahmadou Bamba Diop, Déthié Faye, Momath Lo, Dahbia Bakiri, Huifeng Wang, Mohamed El Garah, Vaishali Sharma, Aman Mahajan, Mohamed Jouini, Diariatou Gningue-Sall and Mohamed M. Chehimi

Surfaces 2025, 8(4), 87; https://doi.org/10.3390/surfaces8040087 - 28 Nov 2025

Viewed by 975

Abstract

In recent years, porous carbon-based materials have demonstrated their potential as electrode materials, particularly as supercapacitors for energy storage. The specific capacitance of a carbon-based material is strongly influenced by its porosity. Herein, activated biochar (BCA) from millet was prepared using ZnCl₂ [...] Read more.

In recent years, porous carbon-based materials have demonstrated their potential as electrode materials, particularly as supercapacitors for energy storage. The specific capacitance of a carbon-based material is strongly influenced by its porosity. Herein, activated biochar (BCA) from millet was prepared using ZnCl₂ as an activator at temperatures of 400, 700, and 900 °C. Activation was achieved through wet and dry impregnation of millet bran powder particles. The porosity of BCAs was assessed by determining the iodine and methylene blue numbers (N_I and N_MB, respectively), which provide information on microporosity and mesoporosity, respectively. Characterization of the BCAs was carried out using Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and cyclic voltammetry. The data show that the BCA prepared at 700 °C following dry impregnation, P700(p), has the highest N_I and the highest geometric mean value (

ñ = \sqrt{N_{I} \times N_{M B}}

), a descriptor we introduce to characterize the overall porosity of the biochars. P700(p) biochar exhibited remarkable electrochemical properties and a maximum specific capacitance of 440 F g⁻¹ at a current density of 0.5 A g⁻¹, in the three-electrode configuration. This value drops to 110 F g⁻¹, in the two-electrode configuration. The high specific capacitance is not due to ZnO, but essentially to the textural properties of the biochar (represented by ñ descriptor), and possibly but to a lesser extent to small amounts of Zn₂SiO₄ left over in the biochar. Moreover, the capacitance retention increases with cycling, up to 130%, thus suggesting electrochemical activation of the biochar during the galvanostatic charge-discharge process. To sum up, the combination of pyrolysis temperature and the method of impregnation permitted to obtaining of a porous biochar with excellent electrochemical properties, meeting the requirements of supercapacitors and batteries. Full article

(This article belongs to the Special Issue Surface Science in Electrochemical Energy Storage)

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10 pages, 2210 KB

Open AccessArticle

The Supramolecular Structure Modulates the Acidity of Amphiphiles

by Javier Alejandro Bellon and Natalia Wilke

Surfaces 2025, 8(4), 86; https://doi.org/10.3390/surfaces8040086 - 28 Nov 2025

Viewed by 446

Abstract

It is recognized that the ionization state of amphipathic molecules can affect the curvature and arrangement of the supramolecular structure of which they are a part due to changes in their shape and interactions with neighboring molecules. The pKa influences the overall charge [...] Read more.

It is recognized that the ionization state of amphipathic molecules can affect the curvature and arrangement of the supramolecular structure of which they are a part due to changes in their shape and interactions with neighboring molecules. The pKa influences the overall charge of the molecule and its local environment, which in turn can cause it to pack into different structures, from planar lamellar membranes to curved micelles or reversed phases. It is also recognized, though less explored, that the supramolecular structure can, in turn, affect the pKa value of the molecule. We explored this possibility with oleic acid molecules and found that the apparent pKa changed by two pH units when the surfactant was forced to remain on a flat surface, compared to the value of the aggregate in suspension, where the molecule adopts the most stable supramolecular structure for each ionization state. The pKa shifted to higher values when fatty acid was forced to form planar structures, and the pH range in which neutral and ionic species coexist (conditions under which lamellar vesicles form spontaneously) increased. Thus, we propose that it is possible to control the ionization state of molecules adsorbed onto a surface, and consequently the surface charge, by modifying surface roughness. Full article

(This article belongs to the Special Issue Advances in Solid–Liquid Interface Science: From Fundamentals to Applications)

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19 pages, 3486 KB

Open AccessArticle

Impact of Mo Substrate Roughness on the Stability and Properties of Diamond Films for Aerospace Applications

by Luciano Velardi, Grazia Cicala, Antonio Della Torre, Luca Nunzio Francioso and Maria Assunta Signore

Surfaces 2025, 8(4), 85; https://doi.org/10.3390/surfaces8040085 - 26 Nov 2025

Viewed by 747

Abstract

This study deals with diamond films grown via the microwave plasma-enhanced chemical vapor deposition technique (MWPECVD) on molybdenum (Mo) substrates of different roughness. This work is motivated by the necessity of overcoming the poor adhesion of diamond films on smooth Mo substrates, to [...] Read more.

This study deals with diamond films grown via the microwave plasma-enhanced chemical vapor deposition technique (MWPECVD) on molybdenum (Mo) substrates of different roughness. This work is motivated by the necessity of overcoming the poor adhesion of diamond films on smooth Mo substrates, to ensure their effective application as cathodes for aerospace propulsion. The deposition process was monitored in situ using pyrometric interferometry (PI), thus enabling the real-time monitoring of both the rate and the temperature of deposition. The characterization of the obtained diamond films was performed using different techniques, such as Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The poor adhesion of diamond films on Mo substrates was solved by roughening their surface, which promotes residual stress reduction in the diamond films. In this work, the PI technique was also exploited to support the prediction of the adhesion and stability of diamond films before their exposure in air through the monitoring of the deposition temperature. This represents a novel point of our work that has never been discussed in other research papers, as pyrometric interferometry is generally mainly used to assess the rate and the temperature of deposition. Full article

(This article belongs to the Special Issue Surface Engineering of Thin Films)

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11 pages, 1834 KB

Open AccessArticle

Rapid Detection of Hexaconazole in Kiwifruit Using Surface-Enhanced Raman Spectroscopy (SERS) Technology

by Quanping Diao, Liyang Sun, Linlin Lv, Tiechun Li, Jiaqi Pan and Weiwei Luo

Surfaces 2025, 8(4), 84; https://doi.org/10.3390/surfaces8040084 - 25 Nov 2025

Viewed by 451

Abstract

Hexaconazole, a triazole-class fungicide, demonstrates broad-spectrum protective and therapeutic activity against fungal pathogens, particularly those from Basidiomycota and Ascomycota, such as brown spot and powdery mildew. Despite its efficacy in controlling Actinidia brown spot disease in kiwifruit, excessive hexaconazole residues pose significant health [...] Read more.

Hexaconazole, a triazole-class fungicide, demonstrates broad-spectrum protective and therapeutic activity against fungal pathogens, particularly those from Basidiomycota and Ascomycota, such as brown spot and powdery mildew. Despite its efficacy in controlling Actinidia brown spot disease in kiwifruit, excessive hexaconazole residues pose significant health risks due to its high toxicity. To address this challenge, a rapid analytical method for detecting hexaconazole residues in kiwifruit was developed using surface-enhanced Raman spectroscopy (SERS). The methodology employed silver colloid (C-AgNPs) as the active substrate and 1 mol/L NaCl as the aggregation agent, optimized through systematic testing, resulting in an optimal volume ratio of 400:225 between C-AgNPs and hexaconazole solution and a sequential mixing order of C-AgNPs + NaCl + Hexaconazole, followed by a 20 min incubation period. The characteristic Raman peak at 1584 cm⁻¹ was identified as the spectral signature for hexaconazole quantification. Analytical validation revealed a linear detection range of 0.25–2.25 mg/L (R² = 0.9870), precision with a relative standard deviation (RSD) of 1.7%, and an average recovery rate of 88.40–105.50%, confirming the method’s robustness. This approach enables rapid, non-destructive analysis with minimal sample pretreatment, offering high sensitivity and stability. This method demonstrates great potential for detecting hexaconazole residues in agricultural products. Full article

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20 pages, 4671 KB

Open AccessArticle

Post-Annealing Effect on the Physicochemical Properties of Sn-Te-O Thin Films

by Hee-Seung Yoon, Jihyeon Lee, Juyun Park and Yong-Cheol Kang

Surfaces 2025, 8(4), 83; https://doi.org/10.3390/surfaces8040083 - 21 Nov 2025

Viewed by 727

Abstract

This study explores how post-deposition thermal annealing alters the structural, morphological, and electronic properties of Sn–Te–O thin films grown by radio-frequency magnetron co-sputtering. Thin films were annealed at temperatures ranging from 298 K to 873 K and analyzed using a suite of techniques, [...] Read more.

This study explores how post-deposition thermal annealing alters the structural, morphological, and electronic properties of Sn–Te–O thin films grown by radio-frequency magnetron co-sputtering. Thin films were annealed at temperatures ranging from 298 K to 873 K and analyzed using a suite of techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Annealing at 473 K resulted in increased surface roughness (R_q) in Te-rich films, while higher annealing temperatures promoted a chemical shift in tin oxidation states from Sn²⁺ to Sn⁴⁺. XRD patterns of films annealed at 473 K revealed the emergence of cubic-phase SnTe reflections not prominent in unannealed samples. Contact angle measurements indicated enhanced wettability in high-Te films after annealing, and work function analysis via Kelvin probe showed a trend of decreasing surface potential with lower Te content. These results provide insight into the thermal oxidation behavior and surface evolution of SnTe films, relevant for thermoelectric and topological applications. Full article

(This article belongs to the Special Issue Surface Engineering of Thin Films)

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2 pages, 143 KB

Open AccessEditorial

On the Crucial Role of Surfaces and Interfaces in Polymer Thin Films, Coatings and Adhesives

by Maurice Brogly

Surfaces 2025, 8(4), 82; https://doi.org/10.3390/surfaces8040082 - 17 Nov 2025

Viewed by 394

Abstract

Polymeric materials are increasingly used as thin films or coatings with end-use dimensions approaching those of individual polymer molecules [...] Full article

(This article belongs to the Special Issue Surface Science: Polymer Thin Films, Coatings and Adhesives)

18 pages, 23939 KB

Open AccessArticle

Diffusion Barriers for Electrodes in Resistance Spot Welding of Aluminum Alloys—Investigation of Coating Characteristics Using Nanoindentation and SEM Analysis

by Sascha Brechelt, Henning Wiche, Jochen Junge, René Gustus, Harald Schmidt and Volker Wesling

Surfaces 2025, 8(4), 81; https://doi.org/10.3390/surfaces8040081 - 17 Nov 2025

Viewed by 725

Abstract

Resistance spot welding of aluminum alloys causes the electrode materials to degrade rapidly. This is due to diffusion processes occurring between the sheet materials and the copper electrodes at process temperatures of up to 600 °C. This significantly limits the electrode life, resulting [...] Read more.

Resistance spot welding of aluminum alloys causes the electrode materials to degrade rapidly. This is due to diffusion processes occurring between the sheet materials and the copper electrodes at process temperatures of up to 600 °C. This significantly limits the electrode life, resulting in less than 60 weld cycles before the joint quality becomes insufficient. Thin-film diffusion barriers can increase electrode life and improve joint quality. This article describes the generation of barrier layers of nickel and tungsten using physical vapor deposition. These layers directly influence the welding process by altering the electrical resistance and friction coefficients in the contact area. Nanoindentation is used to determine the specific properties of the barrier layers within the 2.5–3 µm layer thickness range. Hardness and modulus of elasticity are determined by indentation tests. Scratch tests determine the friction coefficients and adhesion strength of the coating against plastic deformation. Nanoindentation is also used to investigate the degradation process of the electrode base material and barrier layers. This reveals which damage mechanisms occur with uncoated electrodes and demonstrates how thin-film diffusion barrier coatings can prevent aluminum diffusion. Full article

(This article belongs to the Special Issue Surface Engineering of Thin Films)

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11 pages, 2505 KB

Open AccessArticle

Nylon Powder Composites with High Leveling Property and Toughness Prepared via Filler-Modified Method

by Si-Ao Xin, Yanxiang Wang, Shanshan Xu, Yanying Zhu, Ziyi Xu, Yanru Yuan, Dong Zhang, Yingfan Li and Shaoao Hu

Surfaces 2025, 8(4), 80; https://doi.org/10.3390/surfaces8040080 - 13 Nov 2025

Viewed by 595

Abstract

Powder coating, as a promising coating material, has attracted widespread attention due to its convenient construction and being a green option, promoting environmental protection. However, the existence of defects such as insufficient leveling and poor mechanical properties of the coating during the coating [...] Read more.

Powder coating, as a promising coating material, has attracted widespread attention due to its convenient construction and being a green option, promoting environmental protection. However, the existence of defects such as insufficient leveling and poor mechanical properties of the coating during the coating process limits the further expansion of its application fields. Therefore, for this article, powder coatings with high leveling performance were prepared by composite modification of nylon 12 (PA-12) resin with polyacrylates and ethylene-α-olefin copolymers (POE). The introduction of modified polyacrylates reduces the surface tension of nylon chains, enhancing melt flowability during curing and making the coating surface smooth. Furthermore, by introducing POE, the flexibility of the powder coating was improved, and its fracture elongation increased from 59% for pure PA-12 to a maximum of 234%. This study provides an effective method for the modification of nylon powder coatings and offers new insights into their use in high-performance coating applications. Full article

(This article belongs to the Special Issue Surface Science: Polymer Thin Films, Coatings and Adhesives (2nd Edition))

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18 pages, 5381 KB

Open AccessArticle

Development of a Colorimetric Polydiacetylene, Solid-Substrate Sensor for SARS-CoV-2 Detection in Human Saliva

by Christopher T. Stueber, Timothy W. Hanks, Paul L. Dawson, Julie K. Northcutt, William T. Pennington and Belinda Cochran

Surfaces 2025, 8(4), 79; https://doi.org/10.3390/surfaces8040079 - 11 Nov 2025

Viewed by 889

Abstract

The SARS-CoV-2 pandemic caused tremendous loss of life and long-term health effects for many. The virus continues to evolve, and new variants have the potential to cause widespread physical and economic impacts. Long-chain carboxylic acids featuring two conjugated acetylenes midway along the chain [...] Read more.

The SARS-CoV-2 pandemic caused tremendous loss of life and long-term health effects for many. The virus continues to evolve, and new variants have the potential to cause widespread physical and economic impacts. Long-chain carboxylic acids featuring two conjugated acetylenes midway along the chain easily self-assemble onto various substrates, particularly polyvinylidene fluoride, and then polymerize to form a deep blue film. COVID-19 nucleocapsid or spike protein antibodies can be conjugated to the film, and upon exposure to appropriate trigger proteins, they turn pink or red. Certain additives commonly found in commercial preparations of COVID-19 proteins can trigger false positives. The addition of small amounts of surfactants can increase detector sensitivity, though this must be carefully controlled to avoid false positives. Sensing systems based on both nucleocapsid and ACE2 antibodies can detect authentic samples of the virus in human saliva. The platform is readily adaptable to antibodies from new variants. Full article

(This article belongs to the Special Issue Biomolecules at Surface and Interfaces)

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13 pages, 12247 KB

Open AccessArticle

Effect of Linear and Staggered Surface Texture Patterns on the Tribological Performance of M50 Steel

by Ruiqi Cao, Jianhua Yang, Jun Luo and Xiangyu Xie

Surfaces 2025, 8(4), 78; https://doi.org/10.3390/surfaces8040078 - 31 Oct 2025

Viewed by 497

Abstract

M50 steel is a critical bearing material, yet its tribological properties may deteriorate in engineering applications. To reduce the frictional resistance between M50 steel and contact surfaces, this study utilized laser processing technology to fabricate square- and wave-shaped textures (with a depth of [...] Read more.

M50 steel is a critical bearing material, yet its tribological properties may deteriorate in engineering applications. To reduce the frictional resistance between M50 steel and contact surfaces, this study utilized laser processing technology to fabricate square- and wave-shaped textures (with a depth of ~30 μm) in both linear and staggered arrangements. The tribological performance of these textured surfaces was evaluated under dry and oil-lubrication conditions. Experimental results demonstrated that under dry friction conditions, linearly arranged textures reduced frictional resistance, while staggered textures exhibited superior anti-wear performance. Under oil-lubrication conditions, both linear and staggered textures contributed to friction and wear reduction. Moreover, a synergistic effect was observed for the composite staggered pattern, which achieved the maximum reduction in friction coefficient by up to 8.92% and 8.23% under dry and oil-lubricated conditions, respectively. Full article

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27 pages, 5100 KB

Open AccessArticle

Electrochemical and Computational Analyses of Thiocolchicoside as a New Corrosion Inhibitor for Biomedical Ti6Al4V Alloy in Saline Solution: DFT, NBO, and MD Approaches

by Inam M. A. Omar, Ibrahim H. Elshamy, Shimaa Abdel Halim and Magdy A. M. Ibrahim

Surfaces 2025, 8(4), 77; https://doi.org/10.3390/surfaces8040077 - 30 Oct 2025

Viewed by 742

Abstract

The Ti6Al4V alloy is considered the most beneficial of the titanium alloys for use in biomedical applications. However, it corrodes when exposed to various biocompatible fluids. This investigation aims to evaluate the corrosion inhibition performance of the Ti6Al4V in a saline solution (SS) [...] Read more.

The Ti6Al4V alloy is considered the most beneficial of the titanium alloys for use in biomedical applications. However, it corrodes when exposed to various biocompatible fluids. This investigation aims to evaluate the corrosion inhibition performance of the Ti6Al4V in a saline solution (SS) using thiocolchicoside (TCC) drug as an environmentally acceptable corrosion inhibitor. The corrosion assessments were conducted using potentiodynamic polarization curves (PPCs), open-circuit potential (OCP), and electrochemical impedance spectroscopy (EIS) methodologies, supplemented by scanning electron microscopy (SEM), energy-dispersive X-ray (EDS) analysis, atomic force microscopy (AFM), and contact angle (CA) measurements. The outcomes indicated that the inhibitory efficacy improved with higher TCC concentrations (achieving 92.40% at 200 mg/L of TCC) and diminished with an increase in solution temperature. TCC’s physical adsorption onto the surface of the Ti6A14V, which adheres to the Langmuir adsorption isotherm, explains its mitigating power. The TCC acts as a mixed-type inhibitor. The adsorption and inhibitory impact of TCC were examined at various temperatures using PPC and EIS. When TCC is present, the corrosion’s apparent activation energy is higher (35.79 kJ mol⁻¹) than when it is absent (14.46 kJ mol⁻¹). In addition, the correlation between the structural properties of thiocolchicoside (TCC) and its corrosion inhibition performance was systematically analyzed. Density Functional Theory (DFT) calculations were utilized to characterize the adsorption mechanism, supported by Natural Bond Orbital (NBO) analysis and Molecular Dynamics (MD) simulations. The combined computational and electrochemical findings confirm that TCC provides effective and enhanced corrosion protection for the Ti6Al4V alloy in a saline environment. These characteristics provide compelling evidence for the suitability of these pharmaceutical compounds as promising corrosion inhibitors. Full article

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24 pages, 9639 KB

Open AccessArticle

Theoretical Study of the Adsorption of Li₂S and Li₂S₂ Molecules on Multivacancy Defected Graphene

by Francisco Gaztañaga, Rubén E. Ambrusi, Alfredo Juan and Graciela P. Brizuela

Surfaces 2025, 8(4), 76; https://doi.org/10.3390/surfaces8040076 - 29 Oct 2025

Cited by 1 | Viewed by 1070

Abstract

A theoretical study of the adsorption of lithium–sulfur molecules (Li₂S and Li₂S₂) on graphene with three and four vacancies was conducted. The study analyzed the stability, adsorption geometry, electronic structure, charge distribution, and forming bonds between the [...] Read more.

A theoretical study of the adsorption of lithium–sulfur molecules (Li₂S and Li₂S₂) on graphene with three and four vacancies was conducted. The study analyzed the stability, adsorption geometry, electronic structure, charge distribution, and forming bonds between the molecule and the substrates. It has been demonstrated that both types of defects result in stable adsorptions; however, the underlying mechanisms differ. The three-vacancy graphene exhibits a site that favors the adsorption through bonds between S atoms and the substrate, while the graphene with four vacancies promotes the anchoring of molecules through Li atoms. The mechanism associated with the three-vacancy graphene results in increased exothermic adsorption energies. Full article

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15 pages, 15535 KB

Open AccessArticle

Oxide Uniformity and Oxygen Scavenging Correlate with Rapid Formation of Atomically Flat Si(111)–H Surfaces

by Peng-Mou Chen and Yit Lung Khung

Surfaces 2025, 8(4), 75; https://doi.org/10.3390/surfaces8040075 - 24 Oct 2025

Viewed by 898

Abstract

The formation of atomically flat Si(111)–H surfaces was critical for molecular electronics, nanoscale device fabrication, and surface chemistry studies. We systematically investigated how initial oxide composition and dissolved oxygen affected terrace-formation kinetics during ammonium fluoride (NH₄F) etching. N-type Si(111) was cleaned [...] Read more.

The formation of atomically flat Si(111)–H surfaces was critical for molecular electronics, nanoscale device fabrication, and surface chemistry studies. We systematically investigated how initial oxide composition and dissolved oxygen affected terrace-formation kinetics during ammonium fluoride (NH₄F) etching. N-type Si(111) was cleaned with either oxygen plasma or piranha solution to generate, respectively, a more uniform versus a chemically heterogeneous oxide, and then etched in NH₄F containing 0–5% (w/v) ammonium sulfite (AS) as an oxygen scavenger. AFM acquired every 2 min over 20 min revealed that plasma-pretreated surfaces reached atomically flat terraces earlier and more reproducibly than piranha-pretreated surfaces. Increasing AS concentration suppressed oxygen-induced etch pits and promoted the earlier appearance of large, well-ordered terraces, whereas prolonged etching led to roughening. XPS and ATR-FTIR corroborated differences in the starting oxides and confirmed post-etch H-termination. Collectively, the results indicated that oxide uniformity together with oxygen scavenging correlated with faster attainment and greater persistence of low-roughness terraces, providing a practical framework for reproducibly preparing hydrogen-terminated Si(111)–H surfaces. Full article

(This article belongs to the Collection Featured Articles for Surfaces)

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15 pages, 1969 KB

Open AccessArticle

Ion-Type Irradiation Effect on Optical, Structural, and Morphological Properties of ZnO Thin Films

by Alejandra López-Suárez, Dwight R. Acosta, Juan López-Patiño and Beatriz E. Fuentes

Surfaces 2025, 8(4), 74; https://doi.org/10.3390/surfaces8040074 - 24 Oct 2025

Viewed by 869

Abstract

ZnO thin films were deposited on soda–lime glass substrates using the chemical spray pyrolysis method at a temperature of 500 °C. After the deposition, the substrates were irradiated with 10 keV H⁺ and Ar⁺ ions using a Colutron ion gun. We [...] Read more.

ZnO thin films were deposited on soda–lime glass substrates using the chemical spray pyrolysis method at a temperature of 500 °C. After the deposition, the substrates were irradiated with 10 keV H⁺ and Ar⁺ ions using a Colutron ion gun. We investigated the optical, structural, and morphological properties of the irradiated samples using Rutherford Backscattering Spectrometry, Ultraviolet and Visible Spectroscopy, X-ray diffraction, and Scanning Electron Microscopy. Our results showed a slight decrease in the optical band gap of the irradiated samples, which can be attributed to the quantum confinement effect caused by changes in the crystallite size. The diffractograms displayed diffraction peaks corresponding to the characteristic planes of the hexagonal wurtzite phase of ZnO, indicating that the films were polycrystalline with a preferential orientation along the c-axis. We also observed a reduction in the average crystallite size of the samples after ion irradiation. The morphological study showed that the average grain size increased and the shape changed from spherical in the pristine sample to flake-like after irradiation. Additionally, the samples irradiated with Ar⁺ ions exhibited a bimodal distribution in grain size, which is attributed to the defects and nucleation centers generated during the irradiation process. Full article

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16 pages, 12162 KB

Open AccessArticle

Adjustable Capillary Forces Through Wetting State Changes in Liquid Bridges: Regulation via Trapezoidal Microstructures

by Yanlian Liu, Xueli Chen, Yu Wang, Guannan Lei, Junsheng Zhao, Taiyang Li, Liyang Huang and Bo Zhang

Surfaces 2025, 8(4), 73; https://doi.org/10.3390/surfaces8040073 - 12 Oct 2025

Viewed by 3232

Abstract

A detailed understanding of the mechanistic role of solid surface microstructures in modulating capillary forces and liquid transport in liquid bridge systems is crucial, for liquid bridges between rough surfaces are omnipresent in nature and various industries. In this work, Gibbs free energy [...] Read more.

A detailed understanding of the mechanistic role of solid surface microstructures in modulating capillary forces and liquid transport in liquid bridge systems is crucial, for liquid bridges between rough surfaces are omnipresent in nature and various industries. In this work, Gibbs free energy expression was derived for a liquid bridge system confined between a smooth surface and a microstructured surface, based on the principle of minimum thermodynamic potential. Furthermore, by analyzing the energy conversion during spacing variation between the two solid surfaces, an analytical expression for the capillary force of the liquid bridge was derived that incorporates the geometric parameters of the microstructures and the contact angle. Finally, numerical simulations were performed using the Fluent UDFs (User-Defined Functions) to validate the proposed capillary force model. The simulation results validated the analytical expression and revealed the influence of the microstructures on the force distribution on the upper and lower surfaces of the liquid bridge, and on the droplet transport performance. Full article

(This article belongs to the Special Issue Superhydrophobic Surfaces: Wetting Phenomena and Preparation Methods)

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14 pages, 6559 KB

Open AccessArticle

Application of Piper betle Leaf Extract as a Bioactive Additive in Eco-Friendly Antifouling Coatings

by Nguyen Duc Anh, Cao Nhat Linh, Le Thi My Hiep and Dong Van Kien

Surfaces 2025, 8(4), 72; https://doi.org/10.3390/surfaces8040072 - 11 Oct 2025

Viewed by 1443

Abstract

The present study aimed to evaluate the antifouling efficacy of Piper betle leaf extracts as a bioactive additive for eco-friendly antifouling coatings. The composition of P. betle extract was determined and analyzed. Phytochemical analysis revealed that the ethanol extract of P. betle contained [...] Read more.

The present study aimed to evaluate the antifouling efficacy of Piper betle leaf extracts as a bioactive additive for eco-friendly antifouling coatings. The composition of P. betle extract was determined and analyzed. Phytochemical analysis revealed that the ethanol extract of P. betle contained phenolics, tannins, proteins, carbohydrates, and flavonoids, with total phenolic content reaching 260.3 mg GAE/g dry weight and flavonoid content reaching 52.56 mg QE/g dry weight. The antibacterial test results showed that the ethanol extract of P. betle exhibited maximum antibacterial efficacy against E. coli, B. subtilis, S. aureus, and marine bacteria, with inhibition zone diameters of 28.7 ± 0.5, 27.0 ± 1.6, 22.1 ± 0.6, and 35.1 ± 0.5 mm, respectively. Based on the laboratory test results, the ethanol extract of P. betle was chosen to be added to coatings as an antifouling additive. The content of the extract was 0.5, 1.0, and 1.5 wt.%. A field test conducted in tropical seawater (at Nha Trang Bay) demonstrated that incorporating 1 wt.% of P. betle extract into an acrylic copolymer-based coating significantly enhanced its antifouling performance. After nine months of immersion in seawater, this sample maintained an antifouling efficiency of 74%. These findings highlight the potential of P. betle extract as a sustainable alternative to conventional antifouling agents in marine coatings. Full article

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17 pages, 2364 KB

Open AccessArticle

Exploring Electromagnetic Density of States Near Plasmonic Material Interfaces

by Rodolfo Cortés-Martínez, Ricardo Téllez-Limón, Cesar E. Garcia-Ortiz, Benjamín R. Jaramillo-Ávila and Gabriel A. Galaviz-Mosqueda

Surfaces 2025, 8(4), 71; https://doi.org/10.3390/surfaces8040071 - 10 Oct 2025

Viewed by 1034

Abstract

The electromagnetic density of states (EM-DOS) plays a crucial role in understanding light–matter interactions, especially at metal–dielectric interfaces. This study explores the impact of interface geometry, material properties, and nanostructures on EM-DOS, with a focus on surface plasmon polaritons (SPPs) and evanescent waves. [...] Read more.

The electromagnetic density of states (EM-DOS) plays a crucial role in understanding light–matter interactions, especially at metal–dielectric interfaces. This study explores the impact of interface geometry, material properties, and nanostructures on EM-DOS, with a focus on surface plasmon polaritons (SPPs) and evanescent waves. Using a combination of analytical and numerical methods, the behavior of EM-DOS is analyzed as a function of distance from metal–dielectric interfaces, showing exponential decay with penetration depth. The influence of different metals, including copper, gold, and silver, on EM-DOS is examined. Additionally, the effects of dielectric materials, such as Ti

O_{2}

, PMMA, and

{Al}_{2}

O_{3}

, on the enhancement of electromagnetic field confinement are discussed. The study also investigates the effect of nanostructures, like nanohole and nanopillar arrays, on EM-DOS by calculating effective permittivity and analyzing the interaction of quantum emitters with these structures. Results show that nanopillar arrays enhance EM-DOS more effectively than nanohole arrays, especially in the visible spectrum. The findings provide insights into optimizing plasmonic devices for applications in sensing, quantum technologies, and energy conversion. Full article

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36 pages, 2993 KB

Open AccessArticle

Removal of Diclofenac from Aqueous Solutions Using Surfactant-Modified Guava Seeds as Biosorbent

by Iris Coria-Zamudio, Adriana Vázquez-Guerrero, Gabriela Elizabeth Tapia-Quiroz, Selene Anaid Valencia-Leal, Jaime Espino-Valencia, Ruth Alfaro-Cuevas-Villanueva and Raúl Cortés-Martínez

Surfaces 2025, 8(4), 70; https://doi.org/10.3390/surfaces8040070 - 26 Sep 2025

Cited by 1 | Viewed by 1394

Abstract

The persistent pharmaceutical diclofenac (DCF) presents a significant environmental challenge due to its widespread presence and biological activity in water systems. This study aimed to develop and characterize a novel, low-cost biosorbent by modifying waste guava seeds (GS) with the cationic surfactant cetyltrimethylammonium [...] Read more.

The persistent pharmaceutical diclofenac (DCF) presents a significant environmental challenge due to its widespread presence and biological activity in water systems. This study aimed to develop and characterize a novel, low-cost biosorbent by modifying waste guava seeds (GS) with the cationic surfactant cetyltrimethylammonium bromide (CTAB) to enhance the removal of DCF from aqueous solutions. GS and seeds modified with CTAB at 2 mmol/L (MGS-2) and 10 mmol/L (MGS-10) were prepared and characterized using FTIR, SEM-EDS, TGA, and Zeta Potential measurements. Batch adsorption experiments were conducted to assess the effects of contact time, biosorbent dosage, and solution pH. CTAB modification changed the biosorbent’s surface charge from negative to positive, thereby enhancing DCF removal. The MGS-10 biosorbent demonstrated the fastest kinetics. Critically, an intermediate level of surfactant modification (MGS-2) proved optimal, achieving a maximum adsorption capacity of 38.0 mg/g at 45 °C. This capacity significantly surpassed both the GS (29.7 mg/g) and the MGS-10 (32.7 mg/g). This superior performance is attributed to a favorable multi-stage adsorption mechanism, which combines electrostatic attraction and hydrophobic interactions, and is determined to be an endothermic and entropy-driven process. While highly effective, the biosorbents showed poor regenerability with NaOH, indicating a need to explore alternative regeneration methods. This work demonstrates that optimally modified guava seeds are a promising and sustainable material for remediating pharmaceutical contaminants from water. Full article

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15 pages, 4118 KB

Open AccessArticle

Highly Efficient Conversion of Methane to Methanol on Fe-Cu/ZSM-5 Under Mild Conditions: Effective Utilization of Free Radicals by Favorable Valence Ratios

by Huajie Zhang, Yunhan Pu, Yanjun Li and Mingli Fu

Surfaces 2025, 8(4), 69; https://doi.org/10.3390/surfaces8040069 - 23 Sep 2025

Viewed by 1611

Abstract

The selective oxidation of methane to methanol under mild conditions remains a significant challenge due to its stable C-H bond and the propensity for overoxidation of products. Herein, we investigated the Fe- and Cu-modified ZSM-5 catalysts using H₂O₂ as an [...] Read more.

The selective oxidation of methane to methanol under mild conditions remains a significant challenge due to its stable C-H bond and the propensity for overoxidation of products. Herein, we investigated the Fe- and Cu-modified ZSM-5 catalysts using H₂O₂ as an oxidant for the selective oxidation of methane. It was found that the Fe/Cu ratio had a great impact on methanol yield. The Fe₃Cu₁ displayed the highest methanol yield of 29.7 mmol g_cat⁻¹ h⁻¹ with a selectivity of 80.9% at 70 °C. Further analysis revealed that Fe₃Cu₁ showed the highest Fe³⁺ and Cu⁺ contents. The optimal dual valence cycle not only facilitates the efficient utilization of H₂O₂, promoting the activation of methane to •CH₃ at the Fe site, but also suppresses the deep oxidation caused by the Fenton-like effect of Fe/H₂O₂, thus maintaining the high yield and high selectivity of methanol. Full article

(This article belongs to the Special Issue Surface and Interface Science in Energy Materials)

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Surfaces, Volume 8, Issue 4 (December 2025) – 23 articles

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