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Surfaces, Volume 8, Issue 4 (December 2025) – 5 articles

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16 pages, 12162 KB  
Article
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 137
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  
Article
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 189
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  
Article
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
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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 TiO2, PMMA, and Al2O3, 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  
Article
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
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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  
Article
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 447
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 gcat−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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