Surfaces

17 pages, 4647 KiB

Open AccessArticle

Nanoscale Organic Contaminant Detection at the Surface Using Nonlinear Bond Model

by Hendradi Hardhienata, Muhammad Ahyad, Fasya Nabilah, Husin Alatas, Faridah Handayasari, Agus Kartono, Tony Sumaryada and Muhammad D. Birowosuto

Surfaces 2025, 8(1), 11; https://doi.org/10.3390/surfaces8010011 - 2 Feb 2025

Viewed by 476

Abstract

Environmental pollution from organic dyes such as malachite green and rhodamine B poses significant threats to ecosystems and human health due to their toxic properties. The rapid detection of these contaminants with high sensitivity and selectivity is crucial and can be effectively achieved [...] Read more.

Environmental pollution from organic dyes such as malachite green and rhodamine B poses significant threats to ecosystems and human health due to their toxic properties. The rapid detection of these contaminants with high sensitivity and selectivity is crucial and can be effectively achieved using nonlinear optical methods. In this study, we combine the Simplified Bond Hyperpolarizability Model (SBHM) and molecular docking (MD) simulations to investigate the Second-Harmonic Generation (SHG) intensity of organic dyes on a silicon (Si(001)) substrate for nanoscale pollutant detection. Our simulations show good agreement with rotational anisotropy (RA) SHG intensity experimental data across all polarization angles, with a total error estimate of 3%. We find for the first time that the SBHM not only identifies the different organic pollutant dyes on the surface, as in conventional SHG detection, but can also determine their relative orientation and different concentrations on the surface. Meanwhile, MD simulations reveal that rhodamine B shows a strong adsorption affinity of

- 10.4 kcal / mol

to a single-layer graphene oxide (GO) substrate, primarily through

π

-

π

stacking interactions (36 instances) and by adopting a perpendicular molecular orientation. These characteristics significantly enhance SHG sensitivity. A nonlinear susceptibility analysis reveals good agreement between the SBHM and group theory. The susceptibility tensors confirm that the dominant contributions to the SHG signal arise from both the molecular structure and the surface interactions. This underscores the potential of GO-coated silicon substrates for detecting trace levels of organic pollutants with interaction distances ranging from

3.75 Å

to

5.81 Å

. This approach offers valuable applications in environmental monitoring, combining the sensitivity of SHG with the adsorption properties of GO for nanoscale detection. Full article

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

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15 pages, 3540 KiB

Open AccessArticle

Effect of Hydrodynamic Conditions on the Corrosion Mechanism of HSLA X100 Steel by EIS and EN Analysis

by Ricardo Galván-Martínez, Clarisa Campechano-Lira, Ricardo Orozco-Cruz, Miguel Ángel Hernández-Pérez, Francisco López-Huerta, Edgar Mejía-Sánchez, Jorge Alberto Ramírez-Cano and Andres Carmona-Hernández

Surfaces 2025, 8(1), 10; https://doi.org/10.3390/surfaces8010010 - 1 Feb 2025

Viewed by 301

Abstract

In this research work, the influence of the electrolyte hydrodynamic conditions on the corrosion mechanism of the high-strength low-alloy (HSLA) X100 steel used in the petroleum transportation pipelines was analyzed. A Rotary Cylinder Electrode (RCE) was used to simulate the hydrodynamic conditions (1000 [...] Read more.

In this research work, the influence of the electrolyte hydrodynamic conditions on the corrosion mechanism of the high-strength low-alloy (HSLA) X100 steel used in the petroleum transportation pipelines was analyzed. A Rotary Cylinder Electrode (RCE) was used to simulate the hydrodynamic conditions (1000 and 5000 rpm). Mechanical, microstructural and elemental characterization tests were performed on X100 steel, and the electrochemical impedance spectroscopy (EIS) technique was used to analyze the corrosion mechanism, while the morphology of the corrosion process on the corroded surfaces was obtained by scanning electronic microscopy (SEM). It was found that the increasing rotation rate (υ rot) generates a fully developed flow regime where the system was dominated by a mass transfer process and increases the kinetics of chemical and electrochemical reactions so there is an increase in the corrosion rate (CR). On the other hand, the adsorption of corrosion product films that limits the charge transfer process depended on the magnitude of the shear stress that can generate wear and roughness, as well as a greater number of anodic sites, leaving the metal exposure to the corrosive medium. Full article

(This article belongs to the Special Issue Advancements in Surface Engineering for Metallic Alloys)

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16 pages, 12655 KiB

Open AccessArticle

Microstructure Refinement or Increased Copper Solubility: Factors That Contribute to the Pitting Corrosion Tendency in Aluminum–Copper Alloys

by Akbar Niaz and Muhammad Mudassir Ahmad Alwi

Surfaces 2025, 8(1), 9; https://doi.org/10.3390/surfaces8010009 - 25 Jan 2025

Viewed by 318

Abstract

Aluminum–copper alloys are commonly used in the aerospace industry due to their low density and high strength. Pitting corrosion is the major problem of Al-Cu alloys due to the presence of largely separated electrochemical potential difference phases. Microstructure refinement and phase homogenization of [...] Read more.

Aluminum–copper alloys are commonly used in the aerospace industry due to their low density and high strength. Pitting corrosion is the major problem of Al-Cu alloys due to the presence of largely separated electrochemical potential difference phases. Microstructure refinement and phase homogenization of the alloys are believed to be the factors that contribute to decreasing the galvanic coupling between phases, hence decreasing the pitting tendency. In this work, we investigate whether microstructure refinement is the only factor that contributes to pitting or whether some other factors are involved in the pitting tendency. The investigation was conducted on two frequently used aerospace aluminum–copper alloys, Al-2024 T3 and Al-2014 T6. The surface refinement was conducted by laser surface melting, and microstructure characterization was conducted by scanning electron microscopy with an energy-dispersive X-ray analysis. Phase identification before and after the laser surface melting was conducted by X-ray diffraction, while pitting tendency was measured by a polarization test in 1 molar sodium chloride solution. These experimental results revealed that the enrichment of copper in the α-matrix phase was the major contributing factor in pitting as compared to the largely believed microstructural phase refinement. Full article

(This article belongs to the Special Issue Advancements in Surface Engineering for Metallic Alloys)

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12 pages, 2679 KiB

Open AccessArticle

Synthesis and Characterization of SnO₂/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and ZnO/α-Fe₂O₃ Thin Films: Photocatalytic and Antibacterial Applications

by Asma Arfaoui and Ammar Mhamdi

Surfaces 2025, 8(1), 8; https://doi.org/10.3390/surfaces8010008 - 9 Jan 2025

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Abstract

The fabrication of metal oxide semiconductor heterostructures is a major way to enhance their properties in photocatalytic and antibacterial applications. In the present work, ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂ [...] Read more.

The fabrication of metal oxide semiconductor heterostructures is a major way to enhance their properties in photocatalytic and antibacterial applications. In the present work, ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂O₃ are chosen to create the heterostructure of thin films using the spray pyrolysis method. This paper compares the experimental results of the structural and morphological properties of the prepared thin layers using XRD, Raman and SEM. The X-ray diffraction shows that the obtained thin film heterostructures crystallize in a hexagonal phase of ZnO, a cubic phase of In₂O₃ and a tetragonal structure of SnO₂, with all of the preceding phases positioned on the rhombohedral phase of the hematite α-Fe₂O₃. In addition, the SEM study provided the morphology and surface structure and confirmed the presence of a highly folded, rough, uneven surface with imperfections of 20 and 65 nm for In₂O₃/α-Fe₂O₃ and SnO₂/α-Fe₂O₃. The photoactivity of the prepared materials was tested via the photocatalytic degradation of methylene blue (MB) dye. Consequently, our findings demonstrate that the cracked surface improves the rapid absorption of contaminants and allows water to easily pass through the surface of the thin layers. Finally, the antibacterial abilities of ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂O₃ thin films were investigated by using the agar well-diffusion technique, comparing the results to the Gram-negative of Pseudomonas aeruginosa and Gram-positive of Bacillus subtilis, and these thin films were found to have high antibacterial activity. Full article

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

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20 pages, 8626 KiB

Open AccessReview

Electrospinning for Biomedical Applications: An Overview of Material Fabrication Techniques

by Anastasiia D. Tsareva, Valeriia S. Shtol, Dmitriy V. Klinov and Dimitri A. Ivanov

Surfaces 2025, 8(1), 7; https://doi.org/10.3390/surfaces8010007 - 8 Jan 2025

Viewed by 657

Abstract

This review examines recent methodologies for fabricating nonwoven polymer materials through electrospinning, focusing on the underlying physical principles, including the effects of external parameters, experimental conditions, material selection, and primary operational mechanisms. Potential applications of electrospun polymer matrices in tissue engineering are analyzed, [...] Read more.

This review examines recent methodologies for fabricating nonwoven polymer materials through electrospinning, focusing on the underlying physical principles, including the effects of external parameters, experimental conditions, material selection, and primary operational mechanisms. Potential applications of electrospun polymer matrices in tissue engineering are analyzed, with particular emphasis on their utility in biomedical contexts. Key challenges in incorporating new materials into biomedical devices are discussed, along with recent advances in electrospinning techniques driving innovation in this field. Full article

(This article belongs to the Special Issue Bio-Inspired Surfaces)

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15 pages, 4338 KiB

Open AccessArticle

Self-Reduction of Nitric Oxide on Alumina-Supported Ultra-Small Nickel Particles

by Ramazan T. Magkoev, Yong Men, Reza Behjatmanesh-Ardakani, Mohammadreza Elahifard, Nelli E. Pukhaeva, Aleksandr A. Takaev, Ramazan A. Khekilaev, Tamerlan T. Magkoev and Oleg. G. Ashkhotov

Surfaces 2025, 8(1), 6; https://doi.org/10.3390/surfaces8010006 - 8 Jan 2025

Viewed by 469

Abstract

The adsorption and reaction of nitric oxide (NO) molecules on the surface of the model-supported metal/oxide system, consisting of Ni nanoparticles deposited on α-Al₂O₃ (0001) in ultra-high vacuum, have been studied using in situ surface-sensitive techniques and density functional theory [...] Read more.

The adsorption and reaction of nitric oxide (NO) molecules on the surface of the model-supported metal/oxide system, consisting of Ni nanoparticles deposited on α-Al₂O₃ (0001) in ultra-high vacuum, have been studied using in situ surface-sensitive techniques and density functional theory (DFT) calculations. As a combination of X-ray and Auger electron spectroscopy (XPS, AES), Fourier-transform infrared (FTIR) spectroscopy, and temperature-programmed desorption (TPD) techniques reveals, there is a threshold of Ni particle mean size (<d>) of c.a. 2 nm, differentiating the electron state of adsorbed NO molecules and their reaction. The main feature of Ni particles normally not exceeding 2 nm is that the NO adsorbs in the form of (NO)₂ dimers, whereas, for larger particles, the NO molecules adsorb in the form of monomers, usually characteristic for the bulk Ni substrate. This difference is demonstrated to be the main reason for the different reaction of NO molecules on the surface of Ni/alumina. The striking feature is that, in the case of ultra-small Ni particles (<d> ≤ 2 nm), the nitrous oxide (N₂O) molecules are formed upon heating as a result of the NO self-reduction mechanism, which are otherwise not formed in the case of larger Ni particles. According to DFT results, this is due to the significant synergistic impact of NO co-adsorption on the neighboring NO dissociation reaction over ultra-small Ni particles, mediated by the metal/oxide perimeter interface. The observed molecular conversion effects offer an opportunity to tune the catalytic selectivity of this and related metal/oxide systems via varying the supported metal particle size. Full article

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17 pages, 3662 KiB

Open AccessFeature PaperArticle

Superhydrophilic Titania Coatings on Glass Substrates via the Hydrosol Approach

by George V. Theodorakopoulos, Michalis K. Arfanis, Nafsika Mouti, Andreas Kaidatzis, Christian Mitterer, Konstantinos Giannakopoulos and Polycarpos Falaras

Surfaces 2025, 8(1), 5; https://doi.org/10.3390/surfaces8010005 - 6 Jan 2025

Viewed by 489

Abstract

This study presents a comprehensive investigation into the synthesis and characterization of TiO₂ coatings on glass substrates, focusing on the development of superhydrophilic, self-cleaning titania coatings using the hydrosol approach. Stringent cleaning protocols were accurately followed to ensure the pristine condition of [...] Read more.

This study presents a comprehensive investigation into the synthesis and characterization of TiO₂ coatings on glass substrates, focusing on the development of superhydrophilic, self-cleaning titania coatings using the hydrosol approach. Stringent cleaning protocols were accurately followed to ensure the pristine condition of glass surfaces prior to deposition. Various organic precursor solutions were precisely prepared and applied to the glass substrate via dip-coating, followed by subsequent thermal treatment. A range of characterization techniques, including Raman spectroscopy, UV/Vis spectroscopy, scanning and atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements, were employed to assess the properties of the coatings. The results revealed that the samples were influenced by precursor concentration and withdrawal rate, with slow speed leading to minimal alteration of transmittance. The coatings show superhydrophilic properties, as evidenced by contact angle values below 3 degrees for the thinnest films. Their thickness is approximately 13 nm with very low roughness, indicative of a smooth and uniform surface. Optimization of the deposition conditions permits the fabrication of uniform and transparent TiO₂ coatings on glass substrates, offering promising opportunities for the practical use of photoinduced self-cleaning surfaces in real-life applications. Finally, a cost analysis of scaling up the coating and mirror fabrication processes confirmed the economic feasibility of this approach for concentrated solar power (CSP) applications. Full article

(This article belongs to the Special Issue Surface Modification and Coating to Improve Properties of Various Materials)

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12 pages, 3064 KiB

Open AccessArticle

Etching Ceramic Samples with Fast Argon Atoms

by Alexander S. Metel, Sergey N. Grigoriev, Marina A. Volosova, Yury A. Melnik and Enver S. Mustafaev

Surfaces 2025, 8(1), 4; https://doi.org/10.3390/surfaces8010004 - 6 Jan 2025

Viewed by 365

Abstract

A new approach to stripping surface layers from ceramics with fast atoms is proposed. The existing beam sources do not allow for a stripping rate of more than a few µm/h to be achieved. Usually, an increase in the etching rate is associated [...] Read more.

A new approach to stripping surface layers from ceramics with fast atoms is proposed. The existing beam sources do not allow for a stripping rate of more than a few µm/h to be achieved. Usually, an increase in the etching rate is associated with growing flux density and energy of fast atoms, which can heat the parts of the beam source up to an inadmissible temperature. In the present work, the etching rate was significantly increased at permanent flux density and energy due to an increase in the angle of incidence of fast atoms on the product surface. An increase in the angle of incidence from zero to 80° resulted not only in an increase in the etching rate by several times but also in simultaneous polishing of the surface to a high finishing class. Full article

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16 pages, 2465 KiB

Open AccessArticle

Enhanced Photocatalytic Degradation of Cyanide in Mining Wastewater Using a ZnO-BiOI Heterojunction Catalyst

by Darlington C. Ashiegbu, Paballo Pilane, John Moma and Herman Potgieter

Surfaces 2025, 8(1), 3; https://doi.org/10.3390/surfaces8010003 - 5 Jan 2025

Viewed by 447

Abstract

The mining industry often relies on the natural degradation of tailings dams to break down cyanide in wastewater. However, this method has drawbacks, including high costs due to significant water demand and variable effectiveness dependent on environmental conditions, and it is a time-consuming [...] Read more.

The mining industry often relies on the natural degradation of tailings dams to break down cyanide in wastewater. However, this method has drawbacks, including high costs due to significant water demand and variable effectiveness dependent on environmental conditions, and it is a time-consuming process. To address this issue, this study focused on preparing, characterizing, and applying a ZnO-BiOI heterostructure for cyanide removal in water. The heterojunction was thoroughly characterized using techniques such as SEM-EDX, X-ray diffraction, nitrogen adsorption–desorption isotherms, photoluminescence, and XPS scans. The photocatalytic efficacy was evaluated by degrading CN⁻-containing solutions across varying photocatalyst masses, temperatures, and initial cyanide concentrations. The results showed that 5 mg of the heterostructure completely eliminated 40 ppm of cyanide in 35 min. Increasing the catalyst mass to 15 mg significantly reduced the time for the complete degradation of 40 ppm cyanide, while 25 mg of the photocatalyst achieved cyanide removal in 35 min. The optimal temperature was found to be 50 °C, with complete cyanide removal occurring in 20 min within the temperature range of 25 °C to 70 °C. Moreover, when the cyanide concentration ranged from 40 ppm to 100 ppm, 15 mg of heterojunction catalyst achieved a 97% destruction efficiency in removing a 100 ppm cyanide solution within 35 min. These results strongly indicate that the synthesized heterojunction has the potential to serve as an effective and efficient photocatalyst for cyanide degradation in process effluents and wastewater. Full article

(This article belongs to the Special Issue Surface Modification and Coating to Improve Properties of Various Materials)

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19 pages, 5303 KiB

Open AccessArticle

Effects of Temperature on the Fracture Response of EMC-Si Interface Found in Multilayer Semiconductor Components

by João Valdoleiros, Alireza Akhavan-Safar, Payam Maleki, Pedro F. C. Videira, Ricardo J. C. Carbas, Eduardo A. S. Marques, Bala Karunamurthy and Lucas F. M. da Silva

Surfaces 2025, 8(1), 2; https://doi.org/10.3390/surfaces8010002 - 3 Jan 2025

Viewed by 594

Abstract

Despite the fact that temperature is an important condition that affects the behavior of material interfaces used in integrated circuits (ICs), such as the case for epoxy molding compound (EMC) and silicon (Si), this has not been thoroughly studied. To fill this gap, [...] Read more.

Despite the fact that temperature is an important condition that affects the behavior of material interfaces used in integrated circuits (ICs), such as the case for epoxy molding compound (EMC) and silicon (Si), this has not been thoroughly studied. To fill this gap, the present work aims to examine the fracture of the bi-material interfaces in multilayered semiconductor components and, more specifically, the EMC-Si, through the experimental quasi-static mode I fracture experiments conducted at different temperatures. The experiments were followed by numerical simulations using cohesive zone modeling (CZM) implemented using Abaqus. Simulation results were aimed at matching experimental data using an inverse CZM approach to determine cohesive properties such as initial stiffness and maximum traction. Experimental results revealed temperature-dependent variations in fracture behavior, with low temperature (−20 °C) showing a decrease in stiffness with values around 650 MPa/mm and a maximum tensile strength of 48 MPa; high temperature (100 °C) revealed a maximum traction and stiffness of 120 MPa and 1200 MPa/mm, respectively. A possible explanation for the results obtained at high temperatures is that temperature changes cause a significant redistribution of residual stresses in the sample and at the interfaces, reducing the stiffness at lower temperatures. Full article

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

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11 pages, 4269 KiB

Open AccessArticle

The Characterization of Sliding/Pinning Behaviors of Water Droplets on Highly Adhesive Hydrophobic Surfaces

by Jiaru Zhang, Liang Zhang and Jichun You

Surfaces 2025, 8(1), 1; https://doi.org/10.3390/surfaces8010001 - 2 Jan 2025

Viewed by 740

Abstract

Sliding angle (SA) has been widely employed to describe the sliding behaviors of water droplets on substrates. However, it does not work on highly adhesive surfaces since droplets cannot slide along the substrate even at a 90° tilt. In this work, [...] Read more.

Sliding angle (SA) has been widely employed to describe the sliding behaviors of water droplets on substrates. However, it does not work on highly adhesive surfaces since droplets cannot slide along the substrate even at a 90° tilt. In this work, a novel strategy has been developed to characterize the sliding/pinning behaviors based on the collision between a tilted substrate and falling droplets released from a certain height. The critical tilted angle of substrate (i.e., secondary sliding angle, SSA) and the critical releasing height (i.e., H_c) of water droplets have been introduced and measured with the help of commercial equipment (drop shape analysis, DSA). Our results indicate that SSA, H_c and the phase diagram based on the combination of them work well in describing the sliding/pinning behaviors of droplets along highly adhesive substrates. The developed strategy makes it possible to distinguish sliding/pinning behaviors of water droplets along different surfaces as well as different adhesions between them. It can act as an efficient supplement to conventional methods. Full article

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