Surfaces

22 pages, 6000 KB

Open AccessArticle

Magneto-Photoluminescent Hybrid Materials Based on Cobalt Ferrite Nanoparticles and Poly(terephthalaldehyde-undecan-2-one)

by Victor Alfonso Ortiz-Vergara, Marco Antonio Garza-Navarro, Virgilio Angel González-González, Enrique Lopez-Cuellar and Azael Martínez-de la Cruz

Surfaces 2026, 9(1), 6; https://doi.org/10.3390/surfaces9010006 - 27 Dec 2025

Abstract

Magneto-photoluminescent hybrid materials (MPHMs) were prepared by incorporating cobalt ferrite nanoparticles (CFNs) into the fluorescent polymer poly(terephthalaldehyde-undecan-2-one) (PT2U). The CFNs, with a mean size of 3.95 nm, formed aggregates within the PT2U matrix (650–1042 nm) due to surface and interfacial interactions, modulating aggregate [...] Read more.

Magneto-photoluminescent hybrid materials (MPHMs) were prepared by incorporating cobalt ferrite nanoparticles (CFNs) into the fluorescent polymer poly(terephthalaldehyde-undecan-2-one) (PT2U). The CFNs, with a mean size of 3.95 nm, formed aggregates within the PT2U matrix (650–1042 nm) due to surface and interfacial interactions, modulating aggregate morphology and interparticle coupling. Magnetization studies revealed non-monotonic variations in saturation magnetization (30.3–16.2 emu/g), mean blocking temperature (39.3–43.1 K) and effective magnetic anisotropy energy density (2.14 × 10⁶–1.31 × 10⁶ erg/cm³) with increasing CFN content, consistent with the presence of canted surface spins and enhanced magnetizing interparticle interactions. Photoluminescence exhibited progressive quenching, dominated by collisional mechanisms at low CFN content and by interfacial CFN–PT2U interactions at higher loadings. Under a magnetic field (800 Oe), additional quenching occurred, attributed to magnetically induced polymer-chain rearrangements that disrupted the molecular stacking required for efficient aggregation-induced emission. These results demonstrate tunable magneto-photoluminescent coupling in MPHMs governed by surface and interfacial phenomena, providing insights for the design of functional and responsive hybrid materials. Full article

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33 pages, 3267 KB

Open AccessArticle

A Simple Method for Porous Structure Characterization of Ultrafiltration Membranes from Permeability Data and Hydrodynamic Models: A Semi-Empirical Approach

by Manuel Palencia, Jina M. Martínez-Lara, Jorge M. Durango, José Sebastián López Vélez and Enrique M. Combatt

Surfaces 2026, 9(1), 5; https://doi.org/10.3390/surfaces9010005 - 27 Dec 2025

Abstract

New approaches to the characterization of porous materials must satisfy principles of green analytical chemistry; in addition, they should be reproducible, versatile, and capable of providing relevant information for specific applications. Membrane characterization techniques often fail to meet some of these requirements. Specifically, [...] Read more.

New approaches to the characterization of porous materials must satisfy principles of green analytical chemistry; in addition, they should be reproducible, versatile, and capable of providing relevant information for specific applications. Membrane characterization techniques often fail to meet some of these requirements. Specifically, hydrodynamic porous-based model methods (HPMMs) enable the simulation and evaluation of membrane properties, as well as the monitoring of changes in the response to controlled and uncontrolled modifications. Nevertheless, HPMMs are limited by the multifactorial relationships between their variables and by the generation of only single-value responses. Here, a semi-empirical approach to the characterization of membrane pore structure is proposed and evaluated using simple experimental measurements from pristine and modified membranes. The model enables the determination of the effective pore radius based on two size descriptors related to porosity and permeability, the construction of pore size distributions, and the estimation of structural parameters, such as the number of pores, pore size, and surface porosity. Furthermore, it allows for the simulation of Darcy-type flow behavior in both linear and nonlinear regimes. The model was evaluated on pristine and poly(vinyl alcohol)-modified poly(ethersulfone) ultrafiltration membranes (60–120 mmolL⁻¹) by diafiltration (100–400 kPa). Results demonstrate the usefulness of the model in characterizing membrane pore structure by using simple, fast, and non-destructive methods, thereby enabling advances in analytical diafiltration for membrane characterization. Full article

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

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26 pages, 6160 KB

Open AccessReview

Plasma Cleaning of Metal Surfaces: From Contaminant Removal to Surface Functionalization

by Ran Yang, Jing Kang, Zhiqiang Tian, Longfei Qie and Ruixue Wang

Surfaces 2026, 9(1), 4; https://doi.org/10.3390/surfaces9010004 (registering DOI) - 26 Dec 2025

Abstract

The cleanliness and functionalization of metal surfaces are critical factors to determining their performance in high-performance microelectronic packaging, reliable biomedical implants, advanced composite bonding, and other fields. Compared to traditional wet cleaning methods, plasma cleaning technology has emerged as a research hotspot in [...] Read more.

The cleanliness and functionalization of metal surfaces are critical factors to determining their performance in high-performance microelectronic packaging, reliable biomedical implants, advanced composite bonding, and other fields. Compared to traditional wet cleaning methods, plasma cleaning technology has emerged as a research hotspot in surface engineering due to its unique advantages, such as high efficiency and environmental friendliness. It operates under versatile conditions (e.g., power: tens of watts to several kilowatts; pressure: atmospheric to low vacuum; treatment time: seconds to minutes), enabling not only efficient contaminant removal but also targeted surface functionalization, including dramatically enhanced hydrophilicity (e.g., contact angles from >80° to <10°), significantly improved adhesion (e.g., up to 40% increase in bond strength), and modifications in surface roughness, corrosion resistance, and biocompatibility. This review systematically elaborates on the physical, chemical, and synergistic mechanisms of plasma cleaning technology as it acts on metal surfaces. It focuses on plasma cleaning applied to copper, aluminum, titanium and their respective alloys, as well as alloy steels, providing a detailed analysis of contaminant types, plasma cleaning methodologies, common challenges, surface functionalization responses, and subsequent functional applications. Furthermore, this review discusses the current challenges faced by plasma cleaning technology and offers perspectives on its future development directions. It aims to systematize the research progress in plasma cleaning of metal surfaces, thereby facilitating the transition of this technology towards large-scale industrial applications for metal surface functionalization. Full article

(This article belongs to the Special Issue Plasmonics Technology in Surface Science)

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22 pages, 3104 KB

Open AccessReview

Fluorination to Convert the Surface of Lignocellulosic Materials from Hydrophilic to Hydrophobic

by Alexandre Dumontel, Olivier Téraube, Tomy Falcon, Angélique Bousquet, Eric Tomasella, Monica Francesca Pucci, Pierre-Jacques Liotier, Yasser Ahmad, Karine Charlet and Marc Dubois

Surfaces 2026, 9(1), 3; https://doi.org/10.3390/surfaces9010003 - 25 Dec 2025

Abstract

Natural fibers are increasingly used as sustainable, lightweight, and low-cost alternatives to glass fibers in polymer composites. However, their inherent hydrophilicity and surface polarity limit compatibility with non-polar polymer matrices. Both gas/solid and plasma fluorination modify only the surface of lignocellulosic materials. Mild [...] Read more.

Natural fibers are increasingly used as sustainable, lightweight, and low-cost alternatives to glass fibers in polymer composites. However, their inherent hydrophilicity and surface polarity limit compatibility with non-polar polymer matrices. Both gas/solid and plasma fluorination modify only the surface of lignocellulosic materials. Mild conditions are mild, with reactivity governed by fluorine concentration, temperature, and material composition. Surface energy is typically assessed through contact-angle measurements and surface analytical techniques that quantify changes in hydrophobicity and chemical functionalities. In wood, fluorination proceeds preferentially in lignin-rich regions, making lignin a key component controlling reactivity and the spatial distribution of fluorinated groups. Natural fibers follow the same logic as for flax, which is a representative example of lignin content. Applications of fluorinated bio-based materials include improved moisture resistance, enhanced compatibility in composites, and functional surfaces with tailored wetting properties. Scalability depends on safety, cost, and process control, especially for direct fluorination. Durability of the treatment varies with depth of modification, and environmental considerations include the potential release of fluorinated species during use or disposal. Full article

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

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16 pages, 18448 KB

Open AccessArticle

Effects of Temperature on Anti-Seepage Coating During Vapor Phase Aluminizing of K4125 Ni-Based Superalloy

by Xuxian Zhou, Cheng Xie, Yidi Li and Yunping Li

Surfaces 2026, 9(1), 2; https://doi.org/10.3390/surfaces9010002 - 24 Dec 2025

Abstract

During the vapor phase aluminizing process, protecting the joint regions of turbine blades remains a critical challenge, as the formation of the aluminide coating can significantly increase the brittleness of these areas. To address this issue, a novel double-layer anti-seepage coating was designed [...] Read more.

During the vapor phase aluminizing process, protecting the joint regions of turbine blades remains a critical challenge, as the formation of the aluminide coating can significantly increase the brittleness of these areas. To address this issue, a novel double-layer anti-seepage coating was designed for the K4125 nickel-based superalloy. The coating employs a self-sealing mechanism, transforming from a porous structure into a dense NiAl/Al₂O₃ composite barrier at elevated temperatures, thereby suppressing aluminum penetration. Optimal anti-seepage performance is achieved at 1080 °C, reducing the transition zone width to 42 μm, which is a reduction of more than 70% compared to that of 880 °C. These results are attributed to the synergistic action of multiple mechanisms, including high-temperature densification, the formation of NiAl phase, and the growth of an oxide film on the substrate surface. Additionally, the thermal expansion mismatch enables easy mechanical removal of the coating after aluminizing without substrate damage. The coating system offers an effective and practical solution for high-temperature protection during vapor phase aluminizing in aerospace applications. Full article

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12 pages, 2333 KB

Open AccessArticle

Gas-Phase Modification as Key Process in Design of New Generation of Gd₂O₃-Based Contrast Agents for Computed Tomography

by Anton V. Kupriyanov, Igor Y. Kaplin, Evgeniya V. Suslova, Denis A. Shashurin, Alexei V. Shumyantsev, Dmitry N. Stolbov, Serguei V. Savilov and Georgy A. Chelkov

Surfaces 2026, 9(1), 1; https://doi.org/10.3390/surfaces9010001 - 22 Dec 2025

Abstract

In the present study, thin-layered core–shell Gd₂O₃@SiO_1.5R (R is C₃H₆NH₂) structures were synthesized by gas-phase surface modification of a Gd₂O₃ core with a 3-aminopropyltriethoxysilane (APTES) shell for the [...] Read more.

In the present study, thin-layered core–shell Gd₂O₃@SiO_1.5R (R is C₃H₆NH₂) structures were synthesized by gas-phase surface modification of a Gd₂O₃ core with a 3-aminopropyltriethoxysilane (APTES) shell for the first time. The proposed method consists of two consecutive steps carried out in a fixed-bed reactor. The first step involves APTES adsorption on the Gd₂O₃ surface, followed by APTES hydrolysis by water vapor. The organosyloxane shell formation was confirmed by transmission and scanning electron microscopy, IR spectroscopy, and thermogravimetric data. X-ray attenuation coefficients of Gd₂O₃ and Gd₂O₃@SiO_1.5R samples were determined by photon-counting computed tomography in a phantom study. The SiO_1.5R shells in the synthesized Gd₂O₃@SiO_1.5R samples had minimal thickness and did not affect the attenuation coefficients of Gd₂O₃. Full article

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

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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

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

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

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

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

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

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

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

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

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

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

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

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

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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