Surfaces

15 pages, 6566 KiB

Open AccessArticle

Etching and Compositional Ratio Effect on the Surface Properties of Bismuth Telluride Thin Films

by Jeongho Mun, Sangmin Han, Hee-Seung Yoon, Jisoo Kang, Oliver Jonas, Juyun Park and Yong-Cheol Kang

Surfaces 2024, 7(1), 181-195; https://doi.org/10.3390/surfaces7010012 - 15 Mar 2024

Cited by 1 | Viewed by 1927

Abstract

Bismuth telluride has garnered considerable attention owing to its versatile properties applicable in thermoelectric and antibacterial domains, as well as its intriguing topological insulating properties. In this work, our group fabricated bismuth telluride thin films with various ratios using radio frequency magnetron sputtering. [...] Read more.

Bismuth telluride has garnered considerable attention owing to its versatile properties applicable in thermoelectric and antibacterial domains, as well as its intriguing topological insulating properties. In this work, our group fabricated bismuth telluride thin films with various ratios using radio frequency magnetron sputtering. The surface properties of these thin films were thoroughly analyzed by employing a diverse array of analytical techniques, including X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), four-point probe and contact angle (CA) measurements. Specifically, our XPS findings indicated that Bi is more susceptible to oxidation than Te following Ar⁺-ion etching. Pure Te thin films exhibited the highest R_q value of 31.2 nm based on AFM and SEM results due to their larger grain sizes. The XRD patterns revealed a peak at 27.75° for thin films with 20% Te, attributed to its rhombohedral structure. Moreover, thin films with 30% Te yielded the highest weighted average work function with a value of 4.95 eV after etching. Additionally, pristine Bi and Te thin films demonstrated the most robust hydrophobic properties compared to intermediate-composition thin films, as determined by CA measurements. Full article

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

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17 pages, 5372 KiB

Open AccessArticle

Comparison between Electrooxidation of 1-Naphthol and 2-Naphthol in Different Non-Aqueous Solvents and Suppression of Layer Growth of Polymers

by László Kiss, Péter Szabó and Sándor Kunsági-Máté

Surfaces 2024, 7(1), 164-180; https://doi.org/10.3390/surfaces7010011 - 15 Mar 2024

Cited by 1 | Viewed by 1531

Abstract

The two naphthol isomers were investigated in different organic solvents by taking cyclic voltammograms, and fouling took place on a platinum electrode surface, except for dimethyl sulfoxide and dimethyl formamide. Studies in allyl alcohol rarely used in electrochemical investigations pointed to the importance [...] Read more.

The two naphthol isomers were investigated in different organic solvents by taking cyclic voltammograms, and fouling took place on a platinum electrode surface, except for dimethyl sulfoxide and dimethyl formamide. Studies in allyl alcohol rarely used in electrochemical investigations pointed to the importance of the carbon–carbon double bond as electrode deactivation was remarkably faster compared with its saturated analog solvent. Similarly, the use of the other unsaturated solvent mesityl oxide in the electropolymerization of naphthols resulted in different findings compared with methyl isobutyl ketone. As dimethyl formamide was the best choice concerning the solubility of products, it was successfully tested in electrode renewal after deactivation in an aqueous solution. The increase in dimethyl formamide content led to more and more improved reproducibility of the currents of the outlined aromatic compounds. Naphthol isomers were assessed in the suppression of layer growth originating from the electrooxidation of another monomer phloroglucinol. Its simultaneous electrooxidation with naphthol monomers had a dramatic effect on layer morphology and it was found that instead of a coherent organic layer originating from the homopolymerization of phloroglucinol, the copolymerization with naphthols led to the development of more porous and rougher deposits. The suppressed electropolymerization thus increased sensitivity towards a chosen redox active compound, 4-methoxyphenol. Full article

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21 pages, 16235 KiB

Open AccessArticle

Performance and Surface Modification of Cast Iron Corrosion Products by a Green Rust Converter (Mimosa tenuiflora Extract)

by David Enrique Arceo-Gómez, Javier Reyes-Trujeque, Patricia Balderas-Hernández, Andrés Carmona-Hernández, Araceli Espinoza-Vázquez, Ricardo Galván-Martínez and Ricardo Orozco-Cruz

Surfaces 2024, 7(1), 143-163; https://doi.org/10.3390/surfaces7010010 - 13 Mar 2024

Cited by 1 | Viewed by 2449

Abstract

One of the alternative materials used for conducting conservation treatment of iron artifacts is the rust converter, since it generates barrier properties and more stable oxides. The protective properties and surface modifications from using Mimosa tenuiflora extract as a green rust converter on [...] Read more.

One of the alternative materials used for conducting conservation treatment of iron artifacts is the rust converter, since it generates barrier properties and more stable oxides. The protective properties and surface modifications from using Mimosa tenuiflora extract as a green rust converter on a gray iron oxide layer were studied. The surface characterization was carried out using a Scanning Electron Microscope coupled to an energy-dispersive X-ray spectrometer (SEM-EDS), along with infrared spectroscopy (IR), Raman spectroscopy, X-ray Diffraction (XRD), and Water Contact Angle (WCA). Electrochemical characterization was performed with an Electrochemical Impedance Spectroscope (EIS) using 3.5 wt.% NaCl as the electrolyte. According to the results of the Raman spectroscopy and XRD, the layer of corrosion products formed after 90 days in the atmosphere was composed of goethite, lepidocrocite, maghemite, hematite, and magnetite. The surface of the corrosion products was transformed with the rust converter into an amorphous and microcracked layer. By IR, the Fe-O and C-O-Fe bonds associated with the iron chelate were found with absorption bands at 1540 and 1567 cm⁻¹, respectively. By XRD, a modification of the magnetite crystallinity was observed. Finally, the Water Contact Angle and the protective capacity of the corrosion products were improved by the presence of the rust converter. Full article

(This article belongs to the Special Issue Surface Treatments to Improve the Corrosion Resistance of Metals)

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23 pages, 12525 KiB

Open AccessReview

The Use of Magnetic Porous Carbon Nanocomposites for the Elimination of Organic Pollutants from Wastewater

by Bendi Anjaneyulu, Ravi Rana, Versha, Mozhgan Afshari and Sónia A. C. Carabineiro

Surfaces 2024, 7(1), 120-142; https://doi.org/10.3390/surfaces7010009 - 21 Feb 2024

Viewed by 2397

Abstract

One of the most significant challenges the world is currently facing is wastewater treatment. A substantial volume of effluents from diverse sources releases numerous pollutants into the water. Among these contaminants, organic pollutants are particularly concerning due to the associated risk of being [...] Read more.

One of the most significant challenges the world is currently facing is wastewater treatment. A substantial volume of effluents from diverse sources releases numerous pollutants into the water. Among these contaminants, organic pollutants are particularly concerning due to the associated risk of being released into the environment, garnering significant attention. Rapid advancements in agriculture and industry on a global scale generate vast volumes of hazardous organic compounds, which eventually find their way into natural systems. Recently, the release of industrial wastewater has been increasing, due to the progress of numerous businesses. This poses a danger to humans and the environment, leading to environmental contamination. The application of carbon nanocomposites in applied nanotechnology has recently expanded due to their large surface area, substantial pore volume, low preparation cost, and environmental resilience. Expanding the use of nanomaterials in water treatment is essential, as magnetic carbon nanocomposites consistently demonstrate an efficient elimination of pollutants from water solutions. In the current study, we have highlighted the application of magnetic porous carbon nanocomposites in removing organic pollutants from wastewater. Full article

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

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13 pages, 2627 KiB

Open AccessArticle

Synthesis of WS₂ Ultrathin Films by Magnetron Sputtering Followed by Sulfurization in a Confined Space

by Florinel Sava, Iosif-Daniel Simandan, Angel-Theodor Buruiana, Amelia Elena Bocirnea, Outman El Khouja, Teddy Tite, Mohamed Yasssine Zaki, Claudia Mihai and Alin Velea

Surfaces 2024, 7(1), 108-119; https://doi.org/10.3390/surfaces7010008 - 11 Feb 2024

Cited by 2 | Viewed by 2350

Abstract

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS₂) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS₂ directly on the desired substrate, eliminating the need for [...] Read more.

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS₂) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS₂ directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS₂ ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS₂ were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS₂ films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS₂ crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS₂ films for specific technological applications. Full article

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

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20 pages, 12440 KiB

Open AccessArticle

Impact of Corrosion in Simulated Body Fluid on Fatigue Characteristics of 3D-Printed Polylactic Acid-Coated AM60 Magnesium Alloys

by Seyed Ali Ashraf Talesh and Mohammad Azadi

Surfaces 2024, 7(1), 88-107; https://doi.org/10.3390/surfaces7010007 - 5 Feb 2024

Cited by 1 | Viewed by 1649

Abstract

In this research, the pure fatigue behaviors of AM60 magnesium alloy with polylactic acid (PLA) coating (PF-AM60-PLA) and the corrosion fatigue behaviors of magnesium alloy with PLA coating (CF-AM60-PLA) were evaluated. Polymer coating was made by fused deposition modeling (FDM) with a 3D [...] Read more.

In this research, the pure fatigue behaviors of AM60 magnesium alloy with polylactic acid (PLA) coating (PF-AM60-PLA) and the corrosion fatigue behaviors of magnesium alloy with PLA coating (CF-AM60-PLA) were evaluated. Polymer coating was made by fused deposition modeling (FDM) with a 3D printer and attached to standard fatigue test specimens with glue. Then, after 27 days of immersion in the simulated body fluid (SBF), the high-cycle bending fatigue test was performed on samples. Due to corrosion, the weight of the specimens was reduced by an average of 35%. The corrosion rate decreased in the first 7 days and then increased. PF samples with a coating had an average 49% increase in fatigue lifetime. Regarding the CF samples, despite the use of a 10-times stronger solution, the fatigue lifetime of these samples decreased by only 35%. The field-emission scanning electron microscopy (FESEM) results also showed cleavage plates and striations. In addition, the separation of the glue from the coating and Mg was observed. Corrosion products, in addition to microcracks and holes, were seen on the fracture surface of CF specimens, which caused the stress concentration and the crack initiation. Holes caused by the release of gases were also observed in polymer coatings, which were fabricated by 3D printing. Full article

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9 pages, 2135 KiB

Open AccessArticle

Substrate Doping and Defect Influence on P-Rich InP(001):H Surface Properties

by Rachele Sciotto, Isaac Azahel Ruiz Alvarado and Wolf Gero Schmidt

Surfaces 2024, 7(1), 79-87; https://doi.org/10.3390/surfaces7010006 - 12 Jan 2024

Cited by 5 | Viewed by 1979

Abstract

Density-functional theory calculations on P-rich InP(001):H surfaces are presented. Depending on temperature, pressure and substrate doping, hydrogen desorption or adsorption will occur and influence the surface electronic properties. For p-doped samples, the charge transition levels of the P dangling bond defects resulting [...] Read more.

Density-functional theory calculations on P-rich InP(001):H surfaces are presented. Depending on temperature, pressure and substrate doping, hydrogen desorption or adsorption will occur and influence the surface electronic properties. For p-doped samples, the charge transition levels of the P dangling bond defects resulting from H desorption will lead to Fermi level pinning in the lower half of the band gap. This explains recent experimental data. For n-doped substrates, H-deficient surfaces are the ground-state structure. This will lead to Fermi level pinning below the bulk conduction band minimum. Surface defects resulting from the adsorption of additional hydrogen can be expected as well, but affect the surface electronic properties less than H desorption. Full article

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

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25 pages, 15397 KiB

Open AccessReview

Reviewing Perovskite Oxide-Based Materials for the Effective Treatment of Antibiotic-Polluted Environments: Challenges, Trends, and New Insights

by Afonso Henrique da Silva Júnior, Carlos Rafael Silva de Oliveira, Tarcisio Wolff Leal, Leandro Pellenz, Selene Maria de Arruda Guelli Ulson de Souza, Antônio Augusto Ulson de Souza, António Benjamim Mapossa, Robert Kimutai Tewo, Hilary Limo Rutto, Luciano da Silva and Adriano da Silva

Surfaces 2024, 7(1), 54-78; https://doi.org/10.3390/surfaces7010005 - 11 Jan 2024

Cited by 5 | Viewed by 2715

Abstract

Society confronts the pressing environmental challenges posed by the pervasive presence of toxic pollutants in aquatic ecosystems. The repercussions of contaminant release extend far and wide, endangering marine life and human well-being. While various techniques such as bioremediation, filtration, and adsorption have been [...] Read more.

Society confronts the pressing environmental challenges posed by the pervasive presence of toxic pollutants in aquatic ecosystems. The repercussions of contaminant release extend far and wide, endangering marine life and human well-being. While various techniques such as bioremediation, filtration, and adsorption have been employed for wastewater treatment, they grapple with cost effectiveness and overall efficiency issues. Advanced oxidative processes, including photocatalysis and Fenton, have emerged as viable solutions in response to the emerging contaminants. However, the efficacy of photocatalysis largely hinges on the choice of catalyst. Their distinctive attributes, such as chemical defects and exceptional stability, make perovskite oxides a promising catalyst. These materials can be synthesized through diverse methods, rendering them versatile and adaptable for widespread applications. Ongoing research endeavors are diligently focused on enhancing the performance of perovskite oxides, optimizing their integration into catalytic processes, and exploring innovative approaches for material immobilization. This comprehensive review seeks to elucidate the most pivotal advances in perovskite oxides and their composites within the wastewater treatment domain. Additionally, it sheds light on burgeoning research trends and multifaceted challenges confronting this field, which present insights into techniques for treating the antibiotic-contaminated environment, delving into innovative strategies, green technologies, challenges, and emerging trends. Full article

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10 pages, 17572 KiB

Open AccessArticle

Ignition of Carbon Black during Nanosecond Diffuse and Spark Discharges in Air at Atmospheric Pressure

by Mikhail Lomaev, Victor Tarasenko, Dmitry Sorokin and Dmitry Beloplotov

Surfaces 2024, 7(1), 44-53; https://doi.org/10.3390/surfaces7010004 - 10 Jan 2024

Viewed by 1708

Abstract

Many scientific teams are currently studying the effects of plasma generated by nanosecond diffuse discharges on the surfaces of various materials in order to modify their properties. To achieve this, uniform plasma is required to act on the target being treated, which is [...] Read more.

Many scientific teams are currently studying the effects of plasma generated by nanosecond diffuse discharges on the surfaces of various materials in order to modify their properties. To achieve this, uniform plasma is required to act on the target being treated, which is often an electrode in a discharge system. Previously, the surface treatment uniformity of flat electrodes during a nanosecond discharge in a point-to-plane gap was studied by applying a carbon black layer, and a discharge mode was identified in which there was no erosion on the treated electrode. In this study, it was established that during a nanosecond discharge in air at atmospheric pressure in a non-uniform electric field, carbon black deposited on the surface of a flat anode can ignite. The conditions and dynamics of carbon black ignition during the nanosecond discharge were determined. It was observed that the carbon black is ignited on the surface and continues to combust in the gap in the form of flame plumes for tens of milliseconds. It was also found that the combustion of carbon black can occur in both diffuse and spark discharges. Full article

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18 pages, 2398 KiB

Open AccessArticle

The Effect of Mn Doping and Ti³⁺ Defects at TiO₂ Surfaces in NO and SO₂ Gas Capture Investigated Using Near-Ambient Pressure X-ray Photoelectron Spectroscopy

by Jack Chun-Ren Ke, Andrew Guy Thomas, Joseph Peake and Robert Sayer

Surfaces 2024, 7(1), 26-43; https://doi.org/10.3390/surfaces7010003 - 5 Jan 2024

Viewed by 1827

Abstract

The removal of air pollutants is an important research topic in order to improve the environment. In addition, many common pollutants can affect human health to varying degrees. In this work, we investigate NO and SO₂ conversion by reaction with a commonly [...] Read more.

The removal of air pollutants is an important research topic in order to improve the environment. In addition, many common pollutants can affect human health to varying degrees. In this work, we investigate NO and SO₂ conversion by reaction with a commonly used metal oxide catalyst, TiO₂. Rutile TiO₂(110) single crystals and industrial powder samples used in sunscreen are studied using near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as a main tool. This allows in situ monitoring of the gas conversion process. We find Ti³⁺ defects (oxygen vacancies) or Mn oxides/cations (MnO) at the TiO₂ surfaces can improve the conversion of NO and SO₂ to surface-bound species. MnO and Ti³⁺ defects at the surface of rutile TiO₂(110) exhibit a synergistic effect on the conversion of NO and SO₂ that is significantly improved by nearly an order of magnitude. The by-products are mainly in the form of NO₃⁻, SO₃²⁻, and SO₄²⁻. We find the main oxidation products formed on the single crystals are subtly different from those on the industrial powder samples. For TiO₂ nanopowders (undoped and Mndoped), the presence of Mn also shows improvement in toxic gas adsorption capacity. Overall, it is believed that the outcome obtained from NAP-XPS in this research provides useful insights for the future use of TiO₂ in pollutant gas capture. Full article

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14 pages, 3871 KiB

Open AccessArticle

Effective Surface Structure Changes and Characteristics of Activated Carbon with the Simple Introduction of Oxygen Functional Groups by Using Radiation Energy

by So Yeong Yang, Byong Chol Bai and Yong Ryeol Kim

Surfaces 2024, 7(1), 12-25; https://doi.org/10.3390/surfaces7010002 - 22 Dec 2023

Cited by 4 | Viewed by 1855

Abstract

In recent years, research has aimed to enhance the environmental friendliness of activated carbon by modifying its surface properties to effectively capture specific harmful gases. This study’s primary goal is to swiftly introduce oxygen functional groups to activated carbon surfaces using microwave and [...] Read more.

In recent years, research has aimed to enhance the environmental friendliness of activated carbon by modifying its surface properties to effectively capture specific harmful gases. This study’s primary goal is to swiftly introduce oxygen functional groups to activated carbon surfaces using microwave and plasma techniques and evaluate their characteristics. In the microwave method, we varied nitric acid concentrations and treatment durations for surface modification. Additionally, plasma treatment was used to introduce oxygen functional groups for comparative purposes. Surface characteristics were assessed through SEM, BET, XPS, and FT-IR analyses. The results indicate that in the microwave method, the quantity of oxygen functional groups increased with longer reaction times. Specifically, the sample treated for 20 min with 8 moles of nitric acid displayed an oxygen content of 14.11 at%, and higher nitric acid concentrations led to a reduced specific surface area. In the case of plasma treatment, higher oxygen flow rates resulted in an O1s content of 17.1 at%, and an increase in oxygen flow rate introduced more oxygen functional groups but decreased the specific surface area. Full article

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11 pages, 7213 KiB

Open AccessArticle

Surface Functionalization of TiO₂ Nanotubes Modified with a Thin Film of BiFeO₃

by Shikhgasan Ramazanov, Farid Orudzhev and Gaji Gajiev

Surfaces 2024, 7(1), 1-11; https://doi.org/10.3390/surfaces7010001 - 19 Dec 2023

Viewed by 1795

Abstract

The atomic layer deposition method allows for the production of a thin film with a high aspect ratio on the uneven surface of titanium dioxide nanotubes TiO₂(Nt). A modified BiFeO₃/TiO₂(Nt)/Ti (BFOT) structure with controllable electrical characteristics was [...] Read more.

The atomic layer deposition method allows for the production of a thin film with a high aspect ratio on the uneven surface of titanium dioxide nanotubes TiO₂(Nt). A modified BiFeO₃/TiO₂(Nt)/Ti (BFOT) structure with controllable electrical characteristics was obtained. BFOT possesses both ferroelectric and semiconductor properties with nonlinear conductivity dependent on the magnitude and duration of the voltage supply. Analysis of the temperature dependence of charge variation showed leakage currents in the BFOT structure due to the capture and release of charge carriers from defect levels. Surface modification of nanotubes with the multiferroic BiFeO₃ allows for the creation of semiconductors with adaptive functional properties. Full article

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Surfaces, Volume 7, Issue 1 (March 2024) – 12 articles

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