Nanomaterials

25 pages, 5169 KiB

Open AccessArticle

Natural Sunlight Driven Photocatalytic Degradation of Methylene Blue and Rhodamine B over Nanocrystalline Zn₂SnO₄/SnO₂

by Maria Vesna Nikolic, Zorka Z. Vasiljevic, Milena Dimitrijevic, Nadezda Radmilovic, Jelena Vujancevic, Marija Tanovic and Nenad B. Tadic

Nanomaterials 2025, 15(14), 1138; https://doi.org/10.3390/nano15141138 - 21 Jul 2025

Viewed by 610

Abstract

The natural sunlight driven photocatalytic degradation of organic pollutants is a sustainable solution for water purification. The use of heterojunction nanocomposites in this process shows promise for improved photodegradation efficiency. In this work, nanocrystalline Zn₂SnO₄/SnO₂ obtained by the [...] Read more.

The natural sunlight driven photocatalytic degradation of organic pollutants is a sustainable solution for water purification. The use of heterojunction nanocomposites in this process shows promise for improved photodegradation efficiency. In this work, nanocrystalline Zn₂SnO₄/SnO₂ obtained by the solid-state synthesis method was tested as a heterojunction photocatalyst material for the degradation of methylene blue (MB) and Rhodamine B (RhB) dyes as single and multicomponent systems in natural sunlight. Characterization of the structure and morphology of the synthesized nanocomposite using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectroscopy confirmed the formation of Zn₂SnO₄/SnO₂ and heterojunctions between Zn₂SnO₄ and the SnO₂ nanoparticles. A photodegradation efficiency of 99.1% was achieved in 120 min with 50 mg of the photocatalyst for the degradation of MB and 70.6% for the degradation of RhB under the same conditions. In the multicomponent system, the degradation efficiency of 97.9% for MB and 53.2% for RhB was obtained with only 15 mg of the photocatalyst. The degradation of MB occurred through N-demethylation and the formation of azure intermediates and degradation of RhB occurred through sequential deethylation and fragmentation of the xanthene ring, both in single and multicomponent systems. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Water Remediation (2nd Edition))

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13 pages, 2944 KiB

Open AccessArticle

Enhancing the Performance of Si/Ga₂O₃ Heterojunction Solar-Blind Photodetectors for Underwater Applications

by Nuoya Li, Zhixuan Liao, Linying Peng, Difei Xue, Kai Peng and Peiwen Lv

Nanomaterials 2025, 15(14), 1137; https://doi.org/10.3390/nano15141137 - 21 Jul 2025

Viewed by 398

Abstract

Epitaxial growth of β-Ga₂O₃ nanowires on silicon substrates was realized by the low-pressure chemical vapor deposition (LPCVD) method. The as-grown Si/Ga₂O₃ heterojunctions were employed in the Underwater DUV detection. It is found that the carrier type as [...] Read more.

Epitaxial growth of β-Ga₂O₃ nanowires on silicon substrates was realized by the low-pressure chemical vapor deposition (LPCVD) method. The as-grown Si/Ga₂O₃ heterojunctions were employed in the Underwater DUV detection. It is found that the carrier type as well as the carrier concentration of the silicon substrate significantly affect the performance of the Si/Ga₂O₃ heterojunction. The p-Si/β-Ga₂O₃ (2.68 × 10¹⁵ cm⁻³) devices exhibit a responsivity of up to 205.1 mA/W, which is twice the performance of the devices on the n-type substrate (responsivity of 93.69 mA/W). Moreover, the devices’ performance is enhanced with the increase in the carrier concentration of the p-type silicon substrates; the corresponding device on the high carrier concentration substrate (6.48 × 10¹⁷ cm⁻³) achieves a superior responsivity of 845.3 mA/W. The performance enhancement is mainly attributed to the built-in electric field at the p-Si/n-Ga₂O₃ heterojunction and the reduction in the Schottky barrier under high carrier concentration. These findings would provide a strategy for optimizing carrier transport and interface engineering in solar-blind UV photodetectors, advancing the practical use of high-performance solar-blind photodetectors for underwater application. Full article

(This article belongs to the Special Issue The Latest Progress of Nanoscale Materials for Photoelectric Detectors)

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81 pages, 10454 KiB

Open AccessReview

Glancing Angle Deposition in Gas Sensing: Bridging Morphological Innovations and Sensor Performances

by Shivam Singh, Kenneth Christopher Stiwinter, Jitendra Pratap Singh and Yiping Zhao

Nanomaterials 2025, 15(14), 1136; https://doi.org/10.3390/nano15141136 - 21 Jul 2025

Viewed by 465

Abstract

Glancing Angle Deposition (GLAD) has emerged as a versatile and powerful nanofabrication technique for developing next-generation gas sensors by enabling precise control over nanostructure geometry, porosity, and material composition. Through dynamic substrate tilting and rotation, GLAD facilitates the fabrication of highly porous, anisotropic [...] Read more.

Glancing Angle Deposition (GLAD) has emerged as a versatile and powerful nanofabrication technique for developing next-generation gas sensors by enabling precise control over nanostructure geometry, porosity, and material composition. Through dynamic substrate tilting and rotation, GLAD facilitates the fabrication of highly porous, anisotropic nanostructures, such as aligned, tilted, zigzag, helical, and multilayered nanorods, with tunable surface area and diffusion pathways optimized for gas detection. This review provides a comprehensive synthesis of recent advances in GLAD-based gas sensor design, focusing on how structural engineering and material integration converge to enhance sensor performance. Key materials strategies include the construction of heterojunctions and core–shell architectures, controlled doping, and nanoparticle decoration using noble metals or metal oxides to amplify charge transfer, catalytic activity, and redox responsiveness. GLAD-fabricated nanostructures have been effectively deployed across multiple gas sensing modalities, including resistive, capacitive, piezoelectric, and optical platforms, where their high aspect ratios, tailored porosity, and defect-rich surfaces facilitate enhanced gas adsorption kinetics and efficient signal transduction. These devices exhibit high sensitivity and selectivity toward a range of analytes, including NO₂, CO, H₂S, and volatile organic compounds (VOCs), with detection limits often reaching the parts-per-billion level. Emerging innovations, such as photo-assisted sensing and integration with artificial intelligence for data analysis and pattern recognition, further extend the capabilities of GLAD-based systems for multifunctional, real-time, and adaptive sensing. Finally, current challenges and future research directions are discussed, emphasizing the promise of GLAD as a scalable platform for next-generation gas sensing technologies. Full article

(This article belongs to the Special Issue Advances and Innovations in Glancing Angle Deposition and Related Nanostructures)

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14 pages, 4332 KiB

Open AccessArticle

Powerful Tribocatalytic Degradation of Methyl Orange Solutions with Concentrations as High as 100 mg/L by BaTiO₃ Nanoparticles

by Mingzhang Zhu, Zeren Zhou, Yanhong Gu, Lina Bing, Yuqin Xie, Zhenjiang Shen and Wanping Chen

Nanomaterials 2025, 15(14), 1135; https://doi.org/10.3390/nano15141135 - 21 Jul 2025

Cited by 1 | Viewed by 330

Abstract

In sharp contrast to photocatalysis and other prevalent catalytic technologies, tribocatalysis has emerged as a promising technology to degrade high-concentration organic dyes in recent years. In this study, BaTiO₃ (BTO) nanoparticles were challenged to degrade methyl orange (MO) solutions with unprecedentedly high [...] Read more.

In sharp contrast to photocatalysis and other prevalent catalytic technologies, tribocatalysis has emerged as a promising technology to degrade high-concentration organic dyes in recent years. In this study, BaTiO₃ (BTO) nanoparticles were challenged to degrade methyl orange (MO) solutions with unprecedentedly high concentrations through magnetic stirring. With BTO nanoparticles and home-made PTFE magnetic rotary disks in 50 mg/L MO solutions, 10 h of magnetic stirring resulted in 91.4% and 98.1% degradations in an as-received glass beaker and in a beaker with a PTFE disk coated on its bottom, respectively. Even for 100 mg/L MO solutions, nearly complete degradation was achieved by magnetic-stirring-stimulated BTO nanoparticles in beakers with the following four kinds of bottom: 97.3% degradation in 30 h for a glass bottom, 97.4% degradation in 20 h for a PTFE coating, 97.9% degradation in 42 h for a Ti coating, and 97.4% degradation in 74 h for an Al₂O₃ coating. Electron paramagnetic resonance (EPR) analyses revealed that the generation of reactive oxygen species (ROS) by magnetic-stirring-stimulated BTO nanoparticles is dramatically affected by the bottom material of beakers. These findings suggest an appealing prospect for BTO nanoparticles to utilize mechanical energy for sustainable water remediation. Full article

(This article belongs to the Special Issue Nanomaterial Application in Environmental Monitoring and Water Treatment: 2nd Edition)

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20 pages, 1106 KiB

Open AccessArticle

Synchrotron-Based Structural Analysis of Nanosized Gd₂(Ti_1−xZr_x)₂O₇ for Radioactive Waste Management

by Marco Pinna, Andrea Trapletti, Claudio Minelli, Armando di Biase, Federico Bianconi, Michele Clemente, Alessandro Minguzzi, Carlo Castellano and Marco Scavini

Nanomaterials 2025, 15(14), 1134; https://doi.org/10.3390/nano15141134 - 21 Jul 2025

Viewed by 366

Abstract

Complex oxides with the general formula Gd₂(Ti_1−xZr_x)₂O₇ are promising candidates for radioactive waste immobilization due to their capacity to withstand radiation by dissipating part of the free energy driving defect creation and phase transitions. [...] Read more.

Complex oxides with the general formula Gd₂(Ti_1−xZr_x)₂O₇ are promising candidates for radioactive waste immobilization due to their capacity to withstand radiation by dissipating part of the free energy driving defect creation and phase transitions. In this study, samples with varying zirconium content (xZr = 0.00, 0.15, 0.25, 0.375, 0.56, 0.75, 0.85, 1.00) were synthesized via the sol–gel method and thermally treated at 500 °C to obtain nanosized powders mimicking the defective structure of irradiated materials. Synchrotron-based techniques were employed to investigate their structural properties: High-Resolution X-ray Powder Diffraction (HR-XRPD) was used to assess long-range structure, while Pair Distribution Function (PDF) analysis and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy provided insights into the local structure. HR-XRPD data revealed that samples with low Zr content (xZr ≤ 0.25) are amorphous. Increasing Zr concentration led to the emergence of a crystalline phase identified as defective fluorite (xZr = 0.375, 0.56). Samples with the highest Zr content (xZr ≥ 0.75) were fully crystalline and exhibited only the fluorite phase. The experimental G(r) functions of the fully crystalline samples in the low r range are suitably fitted by the Weberite structure, mapping the relaxations induced by structural disorder in defective fluorite. These structural insights informed the subsequent EXAFS analysis at the Zr-K and Gd-L₃ edges, confirming the splitting of the cation–cation distances associated with different metal species. Moreover, EXAFS provided a local structural description of the amorphous phases, identifying a consistent Gd-O distance across all compositions. Full article

(This article belongs to the Section Physical Chemistry at Nanoscale)

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23 pages, 2150 KiB

Open AccessReview

Nanomaterials for Persistent Organic Pollutants Decontamination in Water: Mechanisms, Challenges, and Future Perspectives

by Risky Ayu Kristanti, Tony Hadibarata, Adelina-Gabriela Niculescu, Dan Eduard Mihaiescu and Alexandru Mihai Grumezescu

Nanomaterials 2025, 15(14), 1133; https://doi.org/10.3390/nano15141133 - 21 Jul 2025

Viewed by 441

Abstract

Nanomaterials possess unique physicochemical properties that position them as promising candidates for environmental remediation, particularly in the removal of persistent organic pollutants (POPs) from aqueous systems. Their high surface area, tunable functionality, and strong adsorption capabilities have attracted significant attention. In this context, [...] Read more.

Nanomaterials possess unique physicochemical properties that position them as promising candidates for environmental remediation, particularly in the removal of persistent organic pollutants (POPs) from aqueous systems. Their high surface area, tunable functionality, and strong adsorption capabilities have attracted significant attention. In this context, this paper reviews the mechanisms of nanomaterial-based POP decontamination, also providing a critical overview of the limitations and challenges in applying these methods. Specifically, issues of stability, reusability, and aggregation are discussed, which can lead to performance decay during repeated use. In addition, the practical application requires nanocomposites to enable efficient separation and mitigate agglomeration. Environmental concerns also arise from nanomaterials’ fate, transport, and potential toxicity, which may impact aquatic ecosystems and non-target organisms. When checking for large-scale application feasibility, impurities typically add to production costs, recovery problems, and general infrastructure limitations. In addition to these points, there are no standard guidelines or clear risk assessment procedures for registering a product. Unprecedented cross-disciplinary research between natural, human, and technological studies and outreach programs is needed to facilitate the development and diffusion of the results. The barriers will eventually be breached to move from laboratory success in developing the desperately needed new water purification technologies to field-ready water treatment solutions that can address the global POP contamination problem. Full article

(This article belongs to the Special Issue Application of Nanotechnology in Detection and Removal of Pollutants in Water System)

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35 pages, 13218 KiB

Open AccessReview

Research Advances in Nanosensor for Pesticide Detection in Agricultural Products

by Li Feng, Xiaofei Yue, Junhao Li, Fangyao Zhao, Xiaoping Yu and Ke Yang

Nanomaterials 2025, 15(14), 1132; https://doi.org/10.3390/nano15141132 - 21 Jul 2025

Viewed by 551

Abstract

Over the past few decades, pesticide application has increased significantly, driven by population growth and associated urbanization. To date, pesticide use remains crucial for sustaining global food security by enhancing crop yields and preserving quality. However, extensive pesticide application raises serious environmental and [...] Read more.

Over the past few decades, pesticide application has increased significantly, driven by population growth and associated urbanization. To date, pesticide use remains crucial for sustaining global food security by enhancing crop yields and preserving quality. However, extensive pesticide application raises serious environmental and health concerns worldwide due to its chemical persistence and high toxicity to organisms, including humans. Therefore, there is an urgent need to develop rapid and reliable analytical procedures for the quantification of trace pesticide residues to support public health management. Traditional methods, such as chromatography-based detection techniques, cannot simultaneously achieve high sensitivity, selectivity, cost-effectiveness, and portability, which limits their practical application. Nanomaterial-based sensing techniques are increasingly being adopted due to their rapid, efficient, user-friendly, and on-site detection capabilities. In this review, we summarize recent advances and emerging trends in commonly used nanosensing technologies, such as optical and electrochemical sensing, with a focus on recognition elements including enzymes, antibodies, aptamers, and molecularly imprinted polymers (MIPs). We discuss the types of nanomaterials used, preparation methods, performance, characteristics, advantages and limitations, and applications of these nanosensors in detecting pesticide residues in agricultural products. Furthermore, we highlight current challenges, ongoing efforts, and future directions in the development of pesticide detection nanosensors. Full article

(This article belongs to the Special Issue Nanosensors for the Rapid Detection of Agricultural Products)

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21 pages, 4597 KiB

Open AccessArticle

Preparation of Non-Covalent BPTCD/g-C₃N₄ Heterojunction Photocatalysts and Photodegradation of Organic Dyes Under Solar Irradiation

by Xing Wei, Gaopeng Jia, Ru Chen and Yalong Zhang

Nanomaterials 2025, 15(14), 1131; https://doi.org/10.3390/nano15141131 - 21 Jul 2025

Viewed by 323

Abstract

In this study, the BPTCD/g-C₃N₄ heterojunction photocatalyst was successfully prepared by the hydrothermal method. BPTCD (3,3′,4,4′-benzophenone tetracarboxylic dianhydride) is immobilised on the surface of g-C₃N₄ by non-covalent π-π stacking. The BPTCD/g-C₃N₄ heterojunction photocatalyst is [...] Read more.

In this study, the BPTCD/g-C₃N₄ heterojunction photocatalyst was successfully prepared by the hydrothermal method. BPTCD (3,3′,4,4′-benzophenone tetracarboxylic dianhydride) is immobilised on the surface of g-C₃N₄ by non-covalent π-π stacking. The BPTCD/g-C₃N₄ heterojunction photocatalyst is an all-organic photocatalyst with significantly improved photocatalytic performance compared with g-C₃N₄. BPTCD/g-C₃N₄-60% was able to effectively degrade MO solution (10 mg/L) to 99.9% and 82.8% in 60 min under full spectrum and visible light. The TOC measurement results indicate that MO can ultimately be decomposed into H₂O and CO₂ through photocatalytic action. The photodegradation of methyl orange by BPTCD/g-C₃N₄ composite materials under sunlight is mainly attributed to the successful construction of the heterojunction structure and its excellent π-π stacking effect. Superoxide radicals (^•O₂⁻) were found to be the main active species, while ^•OH and h⁺ played a secondary role. The synthesised BPTCD/g-C₃N₄ also showed excellent stability in the activity of photodegradation of MO in wastewater, with the performance remaining above 90% after three cycles. The mechanism of the photocatalytic removal of MO dyes was also investigated by the trap agent experiments. Additionally, BPTCD/g-C₃N₄-60% demonstrated exceptional photodegradation performance in the degradation of methylene blue (MB). BPTCD/g-C₃N₄ heterojunctions have great potential to degrade organic pollutants in wastewater under solar irradiation conditions. Full article

(This article belongs to the Section Environmental Nanoscience and Nanotechnology)

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23 pages, 3863 KiB

Open AccessReview

Memristor-Based Spiking Neuromorphic Systems Toward Brain-Inspired Perception and Computing

by Xiangjing Wang, Yixin Zhu, Zili Zhou, Xin Chen and Xiaojun Jia

Nanomaterials 2025, 15(14), 1130; https://doi.org/10.3390/nano15141130 - 21 Jul 2025

Viewed by 781

Abstract

Threshold-switching memristors (TSMs) are emerging as key enablers for hardware spiking neural networks, offering intrinsic spiking dynamics, sub-pJ energy consumption, and nanoscale footprints ideal for brain-inspired computing at the edge. This review provides a comprehensive examination of how TSMs emulate diverse spiking behaviors—including [...] Read more.

Threshold-switching memristors (TSMs) are emerging as key enablers for hardware spiking neural networks, offering intrinsic spiking dynamics, sub-pJ energy consumption, and nanoscale footprints ideal for brain-inspired computing at the edge. This review provides a comprehensive examination of how TSMs emulate diverse spiking behaviors—including oscillatory, leaky integrate-and-fire (LIF), Hodgkin–Huxley (H-H), and stochastic dynamics—and how these features enable compact, energy-efficient neuromorphic systems. We analyze the physical switching mechanisms of redox and Mott-type TSMs, discuss their voltage-dependent dynamics, and assess their suitability for spike generation. We review memristor-based neuron circuits regarding architectures, materials, and key performance metrics. At the system level, we summarize bio-inspired neuromorphic platforms integrating TSM neurons with visual, tactile, thermal, and olfactory sensors, achieving real-time edge computation with high accuracy and low power. Finally, we critically examine key challenges—such as stochastic switching origins, device variability, and endurance limits—and propose future directions toward reconfigurable, robust, and scalable memristive neuromorphic architectures. Full article

(This article belongs to the Special Issue Neuromorphic Devices: Materials, Structures and Bionic Applications)

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13 pages, 9148 KiB

Open AccessArticle

Investigation of Thermoelectric Properties in Altermagnet RuO₂

by Jun Liu, Chunmin Ning, Xiao Liu, Sicong Zhu and Shuling Wang

Nanomaterials 2025, 15(14), 1129; https://doi.org/10.3390/nano15141129 - 21 Jul 2025

Viewed by 340

Abstract

An altermagnet, characterized by its distinctive magnetic properties, may hold potential applications in diverse fields such as magnetic materials, spintronics, data storage, and quantum computing. As a prototypical altermagnet, RuO₂ exhibits spin polarization and demonstrates the advantageous characteristics of high electrical conductivity [...] Read more.

An altermagnet, characterized by its distinctive magnetic properties, may hold potential applications in diverse fields such as magnetic materials, spintronics, data storage, and quantum computing. As a prototypical altermagnet, RuO₂ exhibits spin polarization and demonstrates the advantageous characteristics of high electrical conductivity and low thermal conductivity. These exceptional properties endow it with considerable promise in the emerging field of thermal spintronics. We studied the electronic structure and thermoelectric properties of RuO₂; the constructed RuO₂/TiO₂/RuO₂ all-antiferromagnetic tunnel junction (AFMTJ) exhibited thermally induced magnetoresistance (TIMR), reaching a maximum TIMR of 1756% at a temperature gradient of 5 K. Compared with prior studies on RuO₂-based antiferromagnetic tunnel junctions, the novelty of this work lies in the thermally induced magnetoresistance based on its superior thermoelectric properties. In parallel structures, the spin-down current dominates the transmission spectrum, whereas in antiparallel structures, the spin-up current governs the transmission spectrum, underscoring the spin-polarized thermal transport. In addition, thermoelectric efficiency emphasizes the potential of RuO₂ to link antiferromagnetic robustness with ferromagnetic spin functionality. These findings promote the development of efficient spintronic devices and spin-based storage technology for waste heat recovery and emphasize the role of spin splitting in zero-magnetization systems. Full article

(This article belongs to the Special Issue Ferroelectricity, Multiferroicity, and Magnetism in Low-Dimensional Nanomaterials)

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10 pages, 2061 KiB

Open AccessArticle

Controlled Synthesis of Tellurium Nanowires and Performance Optimization of Thin-Film Transistors via Percolation Network Engineering

by Mose Park, Zhiyi Lyu, Seung Hyun Song and Hoo-Jeong Lee

Nanomaterials 2025, 15(14), 1128; https://doi.org/10.3390/nano15141128 - 21 Jul 2025

Viewed by 350

Abstract

In this study, we propose a method for systematic nanowire length control through the precise control of the polyvinylpyrrolidone (PVP) concentration during the synthesis of tellurium nanowires. Furthermore, we report the changes in the electrical properties of thin-film transistor (TFT) devices with different [...] Read more.

In this study, we propose a method for systematic nanowire length control through the precise control of the polyvinylpyrrolidone (PVP) concentration during the synthesis of tellurium nanowires. Furthermore, we report the changes in the electrical properties of thin-film transistor (TFT) devices with different lengths of synthesized tellurium nanowires used as channels. Through the use of scanning electron microscopy (SEM) and atomic force microscopy (AFM), it was determined that the length of the wires increased in relation to the amount of PVP incorporated, while the diameter remained consistent. The synthesized long wires formed a well-connected percolation network with a junction density of 4.6 junctions/µm², which enabled the fabrication of devices with excellent electrical properties, the highest on/off ratio of 10³, and charge mobility of 1.1 cm²/V·s. In contrast, wires with comparatively reduced PVP content demonstrated a junction density of 2.1 junctions/µm², exhibiting a lower on/off ratio and reduced charge mobility. These results provide guidance on how the amount of PVP added during wire growth affects the length of the synthesized wires and how it affects the connectivity between the wires when they form a network, which may help optimize the performance of high-performance nanoelectronic devices. Full article

(This article belongs to the Special Issue Nanowires: Growth, Properties, and Applications)

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17 pages, 4345 KiB

Open AccessArticle

Preparation of Superhydrophobic P-TiO₂-SiO₂/HDTMS Self-Cleaning Coatings with UV-Aging Resistance by Acid Precipitation Method

by Le Zhang, Ying Liu, Xuefeng Bai, Hao Ding, Xuan Wang, Daimei Chen and Yihe Zhang

Nanomaterials 2025, 15(14), 1127; https://doi.org/10.3390/nano15141127 - 20 Jul 2025

Viewed by 399

Abstract

The superhydrophobic coatings for outdoor use need to be exposed to sunlight for a long time; therefore, their UV-aging resistances are crucial in practical applications. In this study, the primary product of titanium dioxide (P-TiO₂) was used as the raw material. [...] Read more.

The superhydrophobic coatings for outdoor use need to be exposed to sunlight for a long time; therefore, their UV-aging resistances are crucial in practical applications. In this study, the primary product of titanium dioxide (P-TiO₂) was used as the raw material. Nano-silica (SiO₂) was coated onto the surface of P-TiO₂ by the acid precipitation method to prepare P-TiO₂-SiO₂ composite particles. Then, they were modified and sprayed simply to obtain a superhydrophobic P-TiO₂-SiO₂/HDTMS coating. The results indicated that amorphous nano-SiO₂ was coated on the P-TiO₂ surface, forming a micro–nano binary structure, which was the essential structure to form superhydrophobic coatings. Additionally, the UV-aging property of P-TiO₂ was significantly enhanced after being coated with SiO₂. After continuous UV irradiation for 30 days, the color difference (ΔE*) and yellowing index (Δb*) values of the coating prepared with P-TiO₂-SiO₂ increased from 0 to 0.75 and 0.23, respectively. In contrast, the ΔE* and Δb* of the coating prepared with P-TiO₂ increased from 0 to 1.68 and 0.74, respectively. It was clear that the yellowing degree of the P-TiO₂-SiO₂ coating was lower than that of P-TiO₂, and its UV-aging resistance was significantly improved. After modification with HDTMS, the P-TiO₂-SiO₂ coating formed a superhydrophobic P-TiO₂-SiO₂/HDTMS coating. The water contact angle (WCA) and water slide angle (WSA) on the surface of the coating were 154.9° and 1.3°, respectively. Furthermore, the coating demonstrated excellent UV-aging resistance. After continuous UV irradiation for 45 days, the WCA on the coating surface remained above 150°. Under the same conditions, the WCAs of the P-TiO₂/HDTMS coating decreased from more than 150° to 15.3°. This indicated that the retention of surface hydrophobicity of the P-TiO₂-SiO₂/HDTMS coating was longer than that of P-TiO₂/HDTMS, and the P-TiO₂-SiO₂/HDTMS coating’s UV-aging resistance was greater. The superhydrophobic P-TiO₂-SiO₂/HDTMS self-cleaning coating reported in this study exhibited outstanding UV-aging resistance, and it had the potential for long-term outdoor use. Full article

(This article belongs to the Section Nanocomposite Materials)

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19 pages, 5463 KiB

Open AccessArticle

Evaluation of Aqueous and Ethanolic Extracts for the Green Synthesis of Zinc Oxide Nanoparticles from Tradescantia spathacea

by Pedro Gerardo Trejo-Flores, Yazmin Sánchez-Roque, Heber Vilchis-Bravo, Yolanda del Carmen Pérez-Luna, Paulina Elizabeth Velázquez-Jiménez, Francisco Ramírez-González, Karen Magaly Soto Martínez, Pascual López de Paz, Sergio Saldaña-Trinidad and Roberto Berrones-Hernández

Nanomaterials 2025, 15(14), 1126; https://doi.org/10.3390/nano15141126 - 20 Jul 2025

Viewed by 490

Abstract

In this work, we report a green synthesis of zinc oxide (ZnO) nanoparticles using aqueous and ethanolic extracts of Tradescantia spathacea (purple maguey) as bioreducing and stabilizing agents, which are plant extracts not previously employed for metal oxide nanoparticle synthesis. This method provides [...] Read more.

In this work, we report a green synthesis of zinc oxide (ZnO) nanoparticles using aqueous and ethanolic extracts of Tradescantia spathacea (purple maguey) as bioreducing and stabilizing agents, which are plant extracts not previously employed for metal oxide nanoparticle synthesis. This method provides an efficient, eco-friendly, and reproducible route to obtain ZnO nanoparticles, while minimizing environmental impact compared to conventional chemical approaches. The extracts were prepared following a standardized protocol, and their phytochemical profiles, including total phenolics, flavonoids, and antioxidant capacity, were quantified via UV-Vis spectroscopy to confirm their reducing potential. ZnO nanoparticles were synthesized using zinc acetate dihydrate as a precursor, with variations in pH and precursor concentration in both aqueous and ethanolic media. UV-Vis spectroscopy confirmed nanoparticle formation, while X-ray diffraction (XRD) revealed a hexagonal wurtzite structure with preferential (101) orientation and lattice parameters a = b = 3.244 Å, c = 5.197 Å. Scanning electron microscopy (SEM) showed agglomerated morphologies, and Fourier transform infrared spectroscopy (FTIR) confirmed the presence of phytochemicals such as quercetin, kaempferol, saponins, and terpenes, along with Zn–O bonding, indicating surface functionalization. Zeta potential measurements showed improved dispersion under alkaline conditions, particularly with ethanolic extracts. This study presents a sustainable synthesis strategy with tunable parameters, highlighting the critical influence of precursor concentration and solvent environment on ZnO nanoparticle formation. Notably, aqueous extracts promote ZnO synthesis at low precursor concentrations, while alkaline conditions are essential when using ethanolic extracts. Compared to other green synthesis methods, this strategy offers control and reproducibility and employs a non-toxic, underexplored plant source rich in phytochemicals, potentially enhancing the crystallinity, surface functionality, and application potential of the resulting ZnO nanoparticles. These materials show promise for applications in photocatalysis, in antimicrobial coatings, in UV-blocking formulations, and as functional additives in optoelectronic and environmental remediation technologies. Full article

(This article belongs to the Special Issue Advanced Nanocatalysis in Environmental Applications)

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16 pages, 4720 KiB

Open AccessArticle

Optical Response Tailoring via Morphosynthesis of Ag@Au Nanoparticles

by David Oswaldo Romero-Quitl, Siva Kumar Krishnan, Martha Alicia Palomino-Ovando, Orlando Hernández-Cristobal, José Concepción Torres-Guzmán, Jesús Eduardo Lugo and Miller Toledo-Solano

Nanomaterials 2025, 15(14), 1125; https://doi.org/10.3390/nano15141125 - 19 Jul 2025

Viewed by 387

Abstract

We present a simple method for customizing the optical characteristics of gold-core, silver-shell (Au@Ag) nanoparticles through controlled morphosynthesis via a seed-mediated chemical reduction approach. By systematically adjusting the concentration of cetyltrimethylammonium chloride (CTAC), we obtained precise control over both the thickness of the [...] Read more.

We present a simple method for customizing the optical characteristics of gold-core, silver-shell (Au@Ag) nanoparticles through controlled morphosynthesis via a seed-mediated chemical reduction approach. By systematically adjusting the concentration of cetyltrimethylammonium chloride (CTAC), we obtained precise control over both the thickness of the Ag shell and the particle shape, transitioning from spherical nanoparticles to distinctly defined nanocubes. Bright field and high-angle annular dark-field scanning transmission electron microscopy (BF-STEM and HAADF-STEM), and energy-dispersive X-ray spectroscopy (EDS) were employed to validate the structural and compositional changes. To link morphology with optical behavior, we utilized the Mie and Maxwell–Garnett theoretical models to simulate the dielectric response of the core–shell nanostructures, showing trends that align with experimental UV-visible absorption spectra. This research presents an easy and adjustable method for modifying the plasmonic properties of Ag@Au nanoparticles by varying their shape and shell, offering opportunities for advanced applications in sensing, photonics, and nanophotonics. Full article

(This article belongs to the Section Nanophotonics Materials and Devices)

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10 pages, 1632 KiB

Open AccessArticle

An Ultra-Narrowband Graphene-Perfect Absorber Based on Bound States in the Continuum of All-Dielectric Metasurfaces

by Qi Zhang, Xiao Zhang, Zhihong Zhu and Chucai Guo

Nanomaterials 2025, 15(14), 1124; https://doi.org/10.3390/nano15141124 - 19 Jul 2025

Viewed by 379

Abstract

Enhancing light absorption in two-dimensional (2D) materials, particularly few-layer structures, is critical for advancing optoelectronic devices such as light sources, photodetectors, and sensors. However, conventional absorption enhancement strategies often suffer from unstable resonant wavelengths and low-quality factors (Q-factors) due to the inherent weak [...] Read more.

Enhancing light absorption in two-dimensional (2D) materials, particularly few-layer structures, is critical for advancing optoelectronic devices such as light sources, photodetectors, and sensors. However, conventional absorption enhancement strategies often suffer from unstable resonant wavelengths and low-quality factors (Q-factors) due to the inherent weak light–matter interactions in 2D materials. To address these limitations, we propose an all-dielectric metasurface graphene-perfect absorber based on toroidal dipole bound state in the continuum (TD-BIC) with an ultra-narrow bandwidth and stable resonant wavelength. The proposed structure achieves tunable absorption linewidths spanning three orders of magnitude (6 nm to 0.0076 nm) through critical coupling modulation. Furthermore, the operational wavelength can be flexibly extended to any near-infrared region by adjusting the grating width. This work establishes a novel paradigm for enhancing the absorption of 2D materials in photonic device applications. Full article

(This article belongs to the Special Issue Two-Dimensional Materials and Metamaterials in Photonics and Optoelectronics (Second Edition))

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14 pages, 1039 KiB

Open AccessArticle

Enhanced Magnetic and Dielectric Performance in Fe₃O₄@Li_0.5Cr_0.5Fe₂O₄ Core/Shell Nanoparticles

by Mohammed K. Al Turkestani

Nanomaterials 2025, 15(14), 1123; https://doi.org/10.3390/nano15141123 - 19 Jul 2025

Viewed by 365

Abstract

This study presents the first successful integration of Fe₃O₄ and Li_0.5Cr_0.5Fe₂O₄ into a well-defined core/shell nanostructure through a two-step synthesis that combines co-precipitation and sol–gel auto-combustion methods. Unlike conventional composites, the core/shell design [...] Read more.

This study presents the first successful integration of Fe₃O₄ and Li_0.5Cr_0.5Fe₂O₄ into a well-defined core/shell nanostructure through a two-step synthesis that combines co-precipitation and sol–gel auto-combustion methods. Unlike conventional composites, the core/shell design effectively suppresses the magnetic dead layer and promotes exchange coupling at the interface, leading to enhanced saturation magnetization, superior magnetic heating (specific absorption rate; SAR), and improved dielectric properties. Our research introduces a novel interfacial engineering strategy that simultaneously optimizes both magnetic and dielectric performance, offering a multifunctional platform for applications in magnetic hyperthermia, electromagnetic interference (EMI) shielding, and microwave devices. Full article

(This article belongs to the Section Nanoelectronics, Nanosensors and Devices)

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13 pages, 9483 KiB

Open AccessArticle

Abnormal Angle-Dependent Multi-Channel Filtering in Photonic Crystals Containing Hyperbolic Metamaterials

by Mingyan Xie, Yuanda Huang, Haoyuan Qin and Guiqiang Du

Nanomaterials 2025, 15(14), 1122; https://doi.org/10.3390/nano15141122 - 19 Jul 2025

Viewed by 426

Abstract

Tunneling modes in all-dielectric one-dimensional photonic crystals can be utilized for multi-channel filtering. However, these tunneling modes generally blue shift upon increasing the incident angle. When hyperbolic metamaterials are introduced into one-dimensional photonic crystals, the competition between the propagation phase shifts in the [...] Read more.

Tunneling modes in all-dielectric one-dimensional photonic crystals can be utilized for multi-channel filtering. However, these tunneling modes generally blue shift upon increasing the incident angle. When hyperbolic metamaterials are introduced into one-dimensional photonic crystals, the competition between the propagation phase shifts in the dielectric materials and hyperbolic metamaterials can result in different angle dependencies, including blue shift, abnormal zero shift, and abnormal red shift. When the reduction in the propagation phase in the dielectric layer exceeds the increment in the propagation phase in the hyperbolic metamaterial, the tunneling modes are blue-shifted; conversely, when the phase increment in the hyperbolic metamaterial exceeds the phase reduction in the dielectric layer, the tunneling modes are abnormally red-shifted. When the phase changes in the two materials are the same, the tunneling modes are angle independent. In this study, we investigated the multiple filtering effects of one-dimensional photonic structures composed of hyperbolic metamaterials. These composed structures exhibited multiple tunneling modes based on one-, two-, or three-angle dependencies and can be applied in novel optical devices with different angle-dependence requirements. Full article

(This article belongs to the Special Issue Design and Fabrication of Nanostructured Metamaterials: Bridging Nanophotonics to Next-Generation Optical Technologies)

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19 pages, 1567 KiB

Open AccessReview

Design Efficiency: A Critical Perspective on Testing Methods for Solar-Driven Photothermal Evaporation and Photocatalysis

by Hady Hamza, Maria Vittoria Diamanti, Vanni Lughi, Sergio Rossi and Daniela Meroni

Nanomaterials 2025, 15(14), 1121; https://doi.org/10.3390/nano15141121 - 18 Jul 2025

Viewed by 419

Abstract

Water scarcity is a growing global challenge, intensified by climate change, seawater intrusion, and pollution. While conventional desalination methods are energy-intensive, solar-driven interfacial evaporators offer a promising low-energy solution by leveraging solar energy for water evaporation, with the resulting steam condensed into purified [...] Read more.

Water scarcity is a growing global challenge, intensified by climate change, seawater intrusion, and pollution. While conventional desalination methods are energy-intensive, solar-driven interfacial evaporators offer a promising low-energy solution by leveraging solar energy for water evaporation, with the resulting steam condensed into purified water. Despite advancements, challenges persist, particularly in addressing volatile contaminants and biofouling, which can compromise long-term performance. The integration of photocatalysts into solar-driven interfacial evaporators has been proposed as a solution, enabling pollutant degradation and microbial inactivation while enhancing water transport and self-cleaning properties. This review critically assesses testing methodologies for solar-driven interfacial evaporators incorporating both photothermal and photocatalytic functions. While previous studies have examined materials and system design, the added complexity of photocatalysis necessitates new testing approaches. First, solar still setups are analyzed, particularly concentrating on the selection of materials and geometry for the transparent cover and water-collecting surfaces. Then, performance evaluation tests are discussed, with focus on the types of tested pollutants and analytical techniques. Finally, key challenges are presented, providing insights for future advancements in sustainable water purification. Full article

(This article belongs to the Special Issue Degradation of Pollutants by Nanostructured Photocatalysts)

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12 pages, 1891 KiB

Open AccessArticle

Full-Space Three-Dimensional Holograms Enabled by a Reflection–Transmission Integrated Reconfigurable Metasurface

by Rui Feng, Yaokai Yu, Dongyang Wu, Qiulin Tan and Shah Nawaz Burokur

Nanomaterials 2025, 15(14), 1120; https://doi.org/10.3390/nano15141120 - 18 Jul 2025

Viewed by 316

Abstract

A metasurface capable of flexibly manipulating electromagnetic waves to realize holograms presents significant potential in millimeter-wave imaging systems and data storage domains. In this study, full-space three-dimensional holograms are realized from a reflection–transmission integrated reconfigurable metasurface, which can achieve nearly 360° phase coverage [...] Read more.

A metasurface capable of flexibly manipulating electromagnetic waves to realize holograms presents significant potential in millimeter-wave imaging systems and data storage domains. In this study, full-space three-dimensional holograms are realized from a reflection–transmission integrated reconfigurable metasurface, which can achieve nearly 360° phase coverage in reflection space and 180° phase coverage in transmission space. By adjusting the voltage applied to the constituting electronically tunable meta-atoms of the metasurface, an octahedron hologram constituted by three hologram images in different focal planes is generated in the reflection space at 6.25 GHz. Moreover, a diamond hologram, also composed of three hologram images in different focal planes, is achieved in the transmission space at 6.75 GHz. Both the numerical simulation and experimental measurement are performed to validate the full-space holograms implemented by the modified weighted Gerchberg–Saxton (WGS) algorithm with specific phase distribution in different imaging planes. The obtained results pave the way for a wide range of new applications, such as next-generation three-dimensional displays for immersive viewing experiences, high-capacity optical communication systems with enhanced data encoding capabilities, and ultra-secure anti-counterfeiting solutions that are extremely difficult to replicate. Full article

(This article belongs to the Special Issue Metamaterials and Metasurfaces for Advanced Electromagnetic Wave Manipulation and Applications)

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17 pages, 4334 KiB

Open AccessArticle

Wafer-Level Fabrication of Radiofrequency Devices Featuring 2D Materials Integration

by Vitor Silva, Ivo Colmiais, Hugo Dinis, Jérôme Borme, Pedro Alpuim and Paulo M. Mendes

Nanomaterials 2025, 15(14), 1119; https://doi.org/10.3390/nano15141119 - 18 Jul 2025

Viewed by 321

Abstract

Two-dimensional (2D) materials have been proposed for use in a multitude of applications, with graphene being one of the most well-known 2D materials. Despite their potential to contribute to innovative solutions, the fabrication of such devices still faces significant challenges. One of the [...] Read more.

Two-dimensional (2D) materials have been proposed for use in a multitude of applications, with graphene being one of the most well-known 2D materials. Despite their potential to contribute to innovative solutions, the fabrication of such devices still faces significant challenges. One of the key challenges is the fabrication at a wafer-level scale, a fundamental step for allowing reliable and reproducible fabrication of a large volume of devices with predictable properties. Overcoming this barrier will allow further integration with sensors and actuators, as well as enabling the fabrication of complex circuits based on 2D materials. This work presents the fabrication steps for a process that allows the on-wafer fabrication of active and passive radiofrequency (RF) devices enabled by graphene. Two fabrication processes are presented. In the first one, graphene is transferred to a back gate surface using critical point drying to prevent cracks in the graphene. In the second process, graphene is transferred to a flat surface planarized by ion milling, with the gate being buried beneath the graphene. The fabrication employs a damascene-like process, ensuring a flat surface that preserves the graphene lattice. RF transistors, passive RF components, and antennas designed for backscatter applications are fabricated and measured, illustrating the versatility and potential of the proposed method for 2D material-based RF devices. The integration of graphene on devices is also demonstrated in an antenna. This aimed to demonstrate that graphene can also be used as a passive device. Through this device, it is possible to measure different backscatter responses according to the applied graphene gating voltage, demonstrating the possibility of wireless sensor development. With the proposed fabrication processes, a flat graphene with good quality is achieved, leading to the fabrication of RF active devices (graphene transistors) with intrinsic f_T and f_max of 14 GHz and 80 GHz, respectively. Excellent yield and reproducibility are achieved through these methods. Furthermore, since the graphene membranes are grown by Chemical Vapor Deposition (CVD), it is expected that this process can also be applied to other 2D materials. Full article

(This article belongs to the Special Issue Advanced 2D Materials for Emerging Application)

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29 pages, 1812 KiB

Open AccessReview

A Review on the Design Strategies of Copper-Based Catalysts for Enhanced Activity and Stability in Methanol Reforming to Hydrogen

by Shuang Pang, Xueying Dou, Wei Zhao, Suli Bai, Bo Wan, Tiaoxia Wang and Jing-He Yang

Nanomaterials 2025, 15(14), 1118; https://doi.org/10.3390/nano15141118 - 18 Jul 2025

Viewed by 483

Abstract

Methanol Steam Reforming (MSR) is one of the most promising technologies in the hydrogen economy, and copper-based catalysts have become the core materials in this field due to their high activity and low cost. In this paper, we systematically review the design strategies [...] Read more.

Methanol Steam Reforming (MSR) is one of the most promising technologies in the hydrogen economy, and copper-based catalysts have become the core materials in this field due to their high activity and low cost. In this paper, we systematically review the design strategies of copper-based catalysts in MSR reactions in recent years, including structure control, component optimization, support effect, and surface modification. We focus on the mechanisms of active site exposure, improvement of anti-sintering ability, and the enhancement of anti-carbon deposition performance. Finally, we summarize the challenges of current research and propose the future development direction. This review aims to provide a reference for subsequent related research through the experience of this paper. Full article

(This article belongs to the Special Issue Structural Regulation and Performance Assessment of Nanocatalysts)

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14 pages, 5943 KiB

Open AccessArticle

Preparation and Optimization of Mn²⁺-Activated Na₂ZnGeO₄ Phosphors: Insights into Precursor Selection and Microwave-Assisted Solid-State Synthesis

by Xiaomeng Wang, Siyi Wei, Jiaping Zhang, Jiaren Du, Yukun Li, Ke Chen and Hengwei Lin

Nanomaterials 2025, 15(14), 1117; https://doi.org/10.3390/nano15141117 - 18 Jul 2025

Viewed by 374

Abstract

Mn²⁺-doped phosphors emitting green light have garnered significant interest due to their potential applications in display technologies and solid-state lighting. To facilitate the rapid synthesis of high-performance Mn²⁺-activated green phosphors, this research optimizes a microwave-assisted solid-state (MASS) method for [...] Read more.

Mn²⁺-doped phosphors emitting green light have garnered significant interest due to their potential applications in display technologies and solid-state lighting. To facilitate the rapid synthesis of high-performance Mn²⁺-activated green phosphors, this research optimizes a microwave-assisted solid-state (MASS) method for the preparation of Na₂ZnGeO₄:Mn²⁺. Leveraging the unique attributes of the MASS technique, a systematic investigation into the applicability of various Mn-source precursors was conducted. Additionally, the integration of the MASS approach with traditional solid-state reaction (SSR) methods was assessed. The findings indicate that the MASS technique effectively incorporates Mn ions from diverse precursors (including higher oxidation states of manganese) into the crystal lattice, resulting in efficient green emission from Mn²⁺. Notably, the photoluminescence quantum yield (PLQY) of the sample utilizing MnCO₃ as the manganese precursor was recorded at 2.67%, whereas the sample synthesized from MnO₂ exhibited a remarkable PLQY of 17.69%. Moreover, the post-treatment of SSR-derived samples through the MASS process significantly enhanced the PLQY from 0.67% to 8.66%. These results underscore the promise of the MASS method as a novel and efficient synthesis strategy for the rapid and scalable production of Mn²⁺-doped green luminescent materials. Full article

(This article belongs to the Section Inorganic Materials and Metal-Organic Frameworks)

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15 pages, 2929 KiB

Open AccessArticle

Graphene-Loaded LiNbO₃ Directional Coupler: Characteristics and Potential Applications

by Yifan Liu, Fei Lu, Hui Hu, Haoyang Du, Yan Liu and Yao Wei

Nanomaterials 2025, 15(14), 1116; https://doi.org/10.3390/nano15141116 - 18 Jul 2025

Viewed by 342

Abstract

This study explores the impact of graphene integration on lithium niobate (LiNbO₃, LN) ridge waveguides and directional couplers, focusing on coupling efficiency, polarization-dependent light absorption, and temperature sensitivity. Experimental and simulation results reveal that graphene loading significantly alters the effective mode [...] Read more.

This study explores the impact of graphene integration on lithium niobate (LiNbO₃, LN) ridge waveguides and directional couplers, focusing on coupling efficiency, polarization-dependent light absorption, and temperature sensitivity. Experimental and simulation results reveal that graphene loading significantly alters the effective mode refractive index and enhances waveguide coupling, enabling precise control over light transmission and power distribution. The temperature-dependent behavior of graphene–LN structures demonstrates strong thermal sensitivity, with notable changes in output power ratios between cross and through ports under varying temperatures. These findings highlight the potential of graphene–LN hybrid devices for compact, high-performance photonic circuits and temperature sensing applications. This study provides valuable insights into the design of advanced integrated photonic systems, paving the way for innovations in optical communication, sensing, and quantum technologies. Full article

(This article belongs to the Special Issue Photonics/Optoelectronics Properties and Applications of Two-Dimensional Heterostructures)

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16 pages, 10306 KiB

Open AccessArticle

Fabrication and Characterization of Flexible pH Sensors Based on Pulsed Laser-Ablated Graphene/MoS₂ Interdigitated Electrodes

by Zhaochi Chen, Chengche Liu and Minh-Quang Tran

Nanomaterials 2025, 15(14), 1115; https://doi.org/10.3390/nano15141115 - 18 Jul 2025

Viewed by 489

Abstract

Point-of-care (POC) diagnostic technologies have become essential for the real-time monitoring and management of chronic wounds, where maintaining a moist environment and controlling pH levels are critical for effective healing. In this study, a flexible pH sensor based on a graphene/molybdenum disulfide (graphene/MoS [...] Read more.

Point-of-care (POC) diagnostic technologies have become essential for the real-time monitoring and management of chronic wounds, where maintaining a moist environment and controlling pH levels are critical for effective healing. In this study, a flexible pH sensor based on a graphene/molybdenum disulfide (graphene/MoS₂) composite interdigitated electrode (IDE) structure was fabricated using pulsed laser ablation. The pH sensor, with an active area of 30 mm × 30 mm, exhibited good adhesion to the polyethylene terephthalate (PET) substrate and maintained structural integrity under repeated bending cycles. Precise ablation was achieved under optimized conditions of 4.35 J/cm² laser fluence, a repetition rate of 300 kHz, and a scanning speed of 500 mm/s, enabling the formation of defect-free IDE arrays without substrate damage. The influence of laser processing parameters on the surface morphology, electrical conductivity, and wettability of the composite thin films was systematically characterized. The fabricated pH sensor exhibited high sensitivity (~4.7% change in current per pH unit) across the pH 2–10 range, rapid response within ~5.2 s, and excellent mechanical stability under 100 bending cycles with negligible performance degradation. Moreover, the sensor retained > 95% of its stable sensitivity after 7 days of ambient storage. Furthermore, the pH response behavior was evaluated for electrode structures with different pitches, demonstrating that structural design parameters critically impact sensing performance. These results offer valuable insights into the scalable fabrication of flexible, wearable pH sensors, with promising applications in wound monitoring and personalized healthcare systems. Full article

(This article belongs to the Special Issue Laser-Based Nano Fabrication and Nano Lithography: Second Edition)

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15 pages, 2521 KiB

Open AccessArticle

Interface-Driven Electrothermal Degradation in GaN-on-Diamond High Electron Mobility Transistors

by Huanran Wang, Yifan Liu, Xiangming Dong, Abid Ullah, Jisheng Sun, Chuang Zhang, Yucheng Xiong, Peng Gu, Ge Chen and Xiangjun Liu

Nanomaterials 2025, 15(14), 1114; https://doi.org/10.3390/nano15141114 - 18 Jul 2025

Viewed by 351

Abstract

Diamond is an attractive substrate candidate for GaN high-electron-mobility transistors (HEMT) to enhance heat dissipation due to its exceptional thermal conductivity. However, the thermal boundary resistance (TBR) at the GaN–diamond interface poses a significant bottleneck to heat transport, exacerbating self-heating and limiting device [...] Read more.

Diamond is an attractive substrate candidate for GaN high-electron-mobility transistors (HEMT) to enhance heat dissipation due to its exceptional thermal conductivity. However, the thermal boundary resistance (TBR) at the GaN–diamond interface poses a significant bottleneck to heat transport, exacerbating self-heating and limiting device performance. In this work, TCAD simulations were employed to systematically investigate the effects of thermal boundary layer (TBL) thickness (d_TBL) and thermal conductivity (κ_TBL) on the electrothermal behavior of GaN-on-diamond HEMTs. Results show that increasing the TBL thickness (5–20 nm) or decreasing its thermal conductivity (0.1–1.0 W/(m·K)) leads to elevated hotspot temperatures and degraded electron mobility, resulting in a notable deterioration of I–V characteristics. The nonlinear dependence of device performance on κ_TBL is attributed to Fourier’s law, where heat flux is inversely proportional to thermal resistance. Furthermore, the co-analysis of substrate thermal conductivity and interfacial quality reveals that interface TBR has a more dominant impact on device behavior than substrate conductivity. Remarkably, devices with low thermal conductivity substrates and optimized interfaces can outperform those with high-conductivity substrates but poor interfacial conditions. These findings underscore the critical importance of interface engineering in thermal management of GaN–diamond HEMTs and provide a theoretical foundation for future work on phonon transport and defect-controlled thermal interfaces. Full article

(This article belongs to the Special Issue Low-Dimensional Materials: Thermal Characterization, Thermal Devices, and Thermal Management)

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16 pages, 1420 KiB

Open AccessArticle

Light-Driven Quantum Dot Dialogues: Oscillatory Photoluminescence in Langmuir–Blodgett Films

by Tefera Entele Tesema

Nanomaterials 2025, 15(14), 1113; https://doi.org/10.3390/nano15141113 - 18 Jul 2025

Viewed by 338

Abstract

This study explores the optical properties of a close-packed monolayer composed of core/shell-alloyed CdSeS/ZnS quantum dots (QDs) of two different sizes and compositions. The monolayers were self-assembled in a stacked configuration at the water/air interface using Langmuir–Blodgett (LB) techniques. Under continuous 532 nm [...] Read more.

This study explores the optical properties of a close-packed monolayer composed of core/shell-alloyed CdSeS/ZnS quantum dots (QDs) of two different sizes and compositions. The monolayers were self-assembled in a stacked configuration at the water/air interface using Langmuir–Blodgett (LB) techniques. Under continuous 532 nm laser illumination on the red absorption edge of the blue-emitting smaller QDs (QD450), the red-emitting larger QDs (QD645) exhibited oscillatory temporal dynamics in their photoluminescence (PL), characterized by a pronounced blueshift in the emission peak wavelength and an abrupt decrease in peak intensity. Conversely, excitation by a 405 nm laser on the blue absorption edge induced a drastic redshift in the emission wavelength over time. These significant shifts in emission spectra are attributed to photon- and anisotropic-strain-assisted interlayer atom transfer. The findings provide new insights into strain-driven atomic rearrangements and their impact on the photophysical behavior of QD systems. Full article

(This article belongs to the Special Issue Fundamental and Applied Aspects of the Physics in Low-Dimensional Systems)

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13 pages, 2199 KiB

Open AccessArticle

Non-Invasive Composition Identification in Organic Solar Cells via Deep Learning

by Yi-Hsun Chang, You-Lun Zhang, Cheng-Hao Cheng, Shu-Han Wu, Cheng-Han Li, Su-Yu Liao, Zi-Chun Tseng, Ming-Yi Lin and Chun-Ying Huang

Nanomaterials 2025, 15(14), 1112; https://doi.org/10.3390/nano15141112 - 17 Jul 2025

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Abstract

Accurate identification of active-layer compositions in organic photovoltaic (OPV) devices often relies on invasive techniques such as electrical measurements or material extraction, which risk damaging the device. In this study, we propose a non-invasive classification approach based on simulated full-device absorption spectra. To [...] Read more.

Accurate identification of active-layer compositions in organic photovoltaic (OPV) devices often relies on invasive techniques such as electrical measurements or material extraction, which risk damaging the device. In this study, we propose a non-invasive classification approach based on simulated full-device absorption spectra. To account for fabrication-related variability, the active-layer thickness varied by over ±15% around the optimal value, creating a realistic and diverse training dataset. A multilayer perceptron (MLP) neural network was applied with various activation functions, optimization algorithms, and data split ratios. The optimized model achieved classification accuracies exceeding 99% on both training and testing sets, with minimal sensitivity to random initialization or data partitioning. These results demonstrate the potential of applying deep learning to spectral data for reliable, non-destructive OPV composition classification, paving the way for integration into automated manufacturing diagnostics and quality control workflows. Full article

(This article belongs to the Special Issue Advances in Theoretical and Computational Physics of Low-Dimensional Materials)

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12 pages, 2577 KiB

Open AccessArticle

Single-Atom Catalysts Dispersed on Graphitic Carbon Nitride (g-CN): Eley–Rideal-Driven CO-to-Ethanol Conversion

by Jing Wang, Qiuli Song, Yongchen Shang, Yuejie Liu and Jingxiang Zhao

Nanomaterials 2025, 15(14), 1111; https://doi.org/10.3390/nano15141111 - 17 Jul 2025

Viewed by 363

Abstract

The electrochemical reduction of carbon monoxide (COER) offers a promising route for generating value-added multi-carbon (C₂₊) products, such as ethanol, but achieving high catalytic performance remains a significant challenge. Herein, we performed comprehensive density functional theory (DFT) computations to evaluate CO-to-ethanol [...] Read more.

The electrochemical reduction of carbon monoxide (COER) offers a promising route for generating value-added multi-carbon (C₂₊) products, such as ethanol, but achieving high catalytic performance remains a significant challenge. Herein, we performed comprehensive density functional theory (DFT) computations to evaluate CO-to-ethanol conversion on single metal atoms anchored on graphitic carbon nitride (TM/g–CN). We showed that these metal atoms stably coordinate with edge N sites of g–CN to form active catalytic centers. Screening 20 TM/g–CN candidates, we identified V/g–CN and Zn/g–CN as optimal catalysts: both exhibit low free-energy barriers (<0.50 eV) for the key ^*CO hydrogenation steps and facilitate C–C coupling via an Eley–Rideal mechanism with a negligible kinetic barrier (~0.10 eV) to yield ethanol at low limiting potentials, which explains their superior COER performance. An analysis of d-band centers, charge transfer, and bonding–antibonding orbital distributions revealed the origin of their activity. This work provides theoretical insights and useful guidelines for designing high-performance single-atom COER catalysts. Full article

(This article belongs to the Section Theory and Simulation of Nanostructures)

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17 pages, 2675 KiB

Open AccessArticle

An Ab Initio Metadynamics Study Reveals Multiple Mechanisms of Reactivity by a Primal Carbon Cluster Toward Hydrogen and Ammonia in Space

by Dobromir A. Kalchevski, Stefan K. Kolev, Dimitar V. Trifonov, Ivan G. Grozev, Hristiyan A. Aleksandrov, Valentin N. Popov and Teodor I. Milenov

Nanomaterials 2025, 15(14), 1110; https://doi.org/10.3390/nano15141110 - 17 Jul 2025

Viewed by 415

Abstract

We present a theoretical model of the hydrogenation and amination of a primal carbon cluster of the tangled polycyclic type. Hydrogen atoms were introduced via H₂, while the nitrogen source was NH₃. The initial chemical processes were modeled using [...] Read more.

We present a theoretical model of the hydrogenation and amination of a primal carbon cluster of the tangled polycyclic type. Hydrogen atoms were introduced via H₂, while the nitrogen source was NH₃. The initial chemical processes were modeled using Born–Oppenheimer Molecular Dynamics. Metadynamics was employed to accelerate the saturation. The reactions were characterized in terms of barriers, topology, and intricate changes in the electronic structure. All transition states were identified. Multiple mechanisms for each type of reaction were discovered. Occasional unbiased changes in the carbon skeleton, induced by the guided processes, were observed. The initial addition reactions had no barriers due to the instability and high reactivity of the carbon structure. The final product of barrierless hydrogen saturation was C₂₅H₂₆. This molecule included multiple isolated double bonds, a medium-sized conjugated π system, and no triple bonds. Ammonia additions resulted in quaternary ammonium groups and primary amino groups. In the subsequent amination, a barrier appeared in fewer steps than in repetitive hydrogenation. The final product of barrierless saturation with NH₃ was C₂₅H₂(NH₃)₂NH₂. Further amination was characterized by a forward free-energy barrier of an order of magnitude larger than the reverse reaction, and the product was found to be unstable. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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14 pages, 5463 KiB

Open AccessArticle

First-Principles Study of Topological Nodal Line Semimetal I229-Ge₄₈ via Cluster Assembly

by Liwei Liu, Xin Wang, Nan Wang, Yaru Chen, Shumin Wang, Caizhi Hua, Tielei Song, Zhifeng Liu and Xin Cui

Nanomaterials 2025, 15(14), 1109; https://doi.org/10.3390/nano15141109 - 17 Jul 2025

Viewed by 351

Abstract

Group IV element-based topological semimetals (TSMs) are pivotal for next-generation quantum devices due to their ultra-high carrier mobility and low-energy consumption. However, germanium (Ge)-based TSMs remain underexplored despite their compatibility with existing semiconductor technologies. Here, we propose a novel I229-Ge₄₈ allotrope constructed [...] Read more.

Group IV element-based topological semimetals (TSMs) are pivotal for next-generation quantum devices due to their ultra-high carrier mobility and low-energy consumption. However, germanium (Ge)-based TSMs remain underexplored despite their compatibility with existing semiconductor technologies. Here, we propose a novel I229-Ge₄₈ allotrope constructed via bottom-up cluster assembly that exhibits a unique porous spherical Fermi surface and strain-tunable topological robustness. First-principles calculations reveal that I229-Ge₄₈ is a topological nodal line semimetal with exceptional mechanical anisotropy (Young’s modulus ratio: 2.27) and ductility (B/G = 2.21, ν = 0.30). Remarkably, the topological property persists under spin-orbit coupling (SOC) and tensile strain, while compressive strain induces a semiconductor transition (bandgap: 0.29 eV). Furthermore, I229-Ge₄₈ demonstrates strong visible-light absorption (10⁵ cm⁻¹) and a strong strain-modulated infrared response, surpassing conventional Ge allotropes. These findings establish I229-Ge₄₈ as a multifunctional platform for strain-engineered nanoelectronics and optoelectronic devices. Full article

(This article belongs to the Special Issue First-Principles Investigations of Low-Dimensional Nanomaterials (2nd Edition))

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