Nanomaterials

12 pages, 3169 KiB

Open AccessEditor’s ChoiceArticle

by Meiqi Li, Zhibing Li, Huanjun Chen and Weiliang Wang

Nanomaterials 2024, 14(7), 607; https://doi.org/10.3390/nano14070607 - 29 Mar 2024

Viewed by 618

In recent studies, it has been discovered that phonons can carry angular momentum, leading to a series of investigations into systems with three-fold rotation symmetry. However, for systems with two-fold screw rotational symmetry, such as α-MoO₃, there has been no relevant [...] Read more.

In recent studies, it has been discovered that phonons can carry angular momentum, leading to a series of investigations into systems with three-fold rotation symmetry. However, for systems with two-fold screw rotational symmetry, such as α-MoO₃, there has been no relevant discussion. In this paper, we investigated the pseudoangular momentum of phonons in crystals with two-fold screw rotational symmetry. Taking α-MoO₃ as an example, we explain the selection rules in circularly polarized Raman experiments resulting from pseudoangular momentum conservation, providing important guidance for experiments. This study of pseudoangular momentum in α-MoO₃ opens up a new degree of freedom for its potential applications, expanding into new application domains. Full article

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

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15 pages, 4387 KiB

Open AccessEditor’s ChoiceArticle

Reduced Graphene Oxide Modified Nitrogen-Doped Chitosan Carbon Fiber with Excellent Electromagnetic Wave Absorbing Performance

by Mengyao Guo, Ming Lin, Jingwei Xu, Yongjiao Pan, Chen Ma and Guohua Chen

Nanomaterials 2024, 14(7), 587; https://doi.org/10.3390/nano14070587 - 27 Mar 2024

Viewed by 615

Abstract

Lightweight and low-cost one-dimensional carbon materials, especially biomass carbon fibers with multiple porous structures, have received wide attention in the field of electromagnetic wave absorption. In this paper, graphene-coated N-doped porous carbon nanofibers (PCNF) with excellent wave absorption properties were successfully synthesized via [...] Read more.

Lightweight and low-cost one-dimensional carbon materials, especially biomass carbon fibers with multiple porous structures, have received wide attention in the field of electromagnetic wave absorption. In this paper, graphene-coated N-doped porous carbon nanofibers (PCNF) with excellent wave absorption properties were successfully synthesized via electrostatic spinning, electrostatic self-assembly, and high-temperature carbonization. The obtained results showed that the minimum reflection loss of the absorbing carbon fiber obtained under the carbonization condition of 800 °C is −51.047 dB, and the absorption bandwidth of reflection loss below −20 dB is 10.16 GHz. This work shows that carbonization temperature and filler content have a certain effect on the wave-absorbing properties of fiber, graphene with nanofiber, and the design and preparation of high-performance absorbing materials by combining the characteristics of graphene and nanofibers and multi-component coupling to provide new ideas for the research of absorbing materials. Full article

(This article belongs to the Special Issue Graphene and Graphene-Based Polymer Composites: From Preparation to Applications)

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13 pages, 6727 KiB

Open AccessEditor’s ChoiceArticle

Effect of Anisotropy of Reduced Graphene Oxide on Thermal and Electrical Properties in Silicon Carbide Matrix Composites

by Kamil Broniszewski, Jarosław Woźniak, Tomasz Cygan, Marek Kostecki, Dorota Moszczyńska, Marcin Chmielewski, Kamil Dydek and Andrzej Olszyna

Nanomaterials 2024, 14(6), 555; https://doi.org/10.3390/nano14060555 - 21 Mar 2024

Viewed by 735

Abstract

Reduced graphene oxide, due to its structure, exhibits anisotropic properties, which are particularly evident in electrical and thermal conductivity. This study focuses on examining the influence of reduced graphene oxide in silicon carbide on these properties in directions perpendicular and parallel to the [...] Read more.

Reduced graphene oxide, due to its structure, exhibits anisotropic properties, which are particularly evident in electrical and thermal conductivity. This study focuses on examining the influence of reduced graphene oxide in silicon carbide on these properties in directions perpendicular and parallel to the direction of the aligned rGO flakes in produced composites. Reduced graphene oxide is characterized by very high in-plane thermal and electrical conductivity. It was observed that the addition of rGO increases thermal conductivity from 64 W/mK (reference sample) up to 98 W/mK for a SiC–3 wt.% rGO composite in the direction parallel to the rGO flakes. In the perpendicular direction, the values were slightly lower, reaching up to 84 W/mK. The difference observed in electrical conductivity values is more significant and is 1–2 orders of magnitude higher for the flakes’ alignment direction. The measured electrical conductivity increased from 1.2710⁻⁸ S/m for the reference SiC sinter up to 1.55 × 10⁻⁵ S/m and 1.2410⁻⁴ S/m for the composites with 3 wt.% rGO for the perpendicular and parallel directions, respectively. This represents an enhancement of four orders of magnitude, with a clearly visible influence of the anisotropy of the rGO. The composite’s enhanced electrical and thermal conductivity make it particularly attractive for electronic devices and high-power applications. Full article

(This article belongs to the Section 2D and Carbon Nanomaterials)

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33 pages, 9959 KiB

Open AccessEditor’s ChoiceReview

Resistive Switching Devices for Neuromorphic Computing: From Foundations to Chip Level Innovations

by Kannan Udaya Mohanan

Nanomaterials 2024, 14(6), 527; https://doi.org/10.3390/nano14060527 - 15 Mar 2024

Viewed by 1097

Abstract

Neuromorphic computing has emerged as an alternative computing paradigm to address the increasing computing needs for data-intensive applications. In this context, resistive random access memory (RRAM) devices have garnered immense interest among the neuromorphic research community due to their capability to emulate intricate [...] Read more.

Neuromorphic computing has emerged as an alternative computing paradigm to address the increasing computing needs for data-intensive applications. In this context, resistive random access memory (RRAM) devices have garnered immense interest among the neuromorphic research community due to their capability to emulate intricate neuronal behaviors. RRAM devices excel in terms of their compact size, fast switching capabilities, high ON/OFF ratio, and low energy consumption, among other advantages. This review focuses on the multifaceted aspects of RRAM devices and their application to brain-inspired computing. The review begins with a brief overview of the essential biological concepts that inspire the development of bio-mimetic computing architectures. It then discusses the various types of resistive switching behaviors observed in RRAM devices and the detailed physical mechanisms underlying their operation. Next, a comprehensive discussion on the diverse material choices adapted in recent literature has been carried out, with special emphasis on the benchmark results from recent research literature. Further, the review provides a holistic analysis of the emerging trends in neuromorphic applications, highlighting the state-of-the-art results utilizing RRAM devices. Commercial chip-level applications are given special emphasis in identifying some of the salient research results. Finally, the current challenges and future outlook of RRAM-based devices for neuromorphic research have been summarized. Thus, this review provides valuable understanding along with critical insights and up-to-date information on the latest findings from the field of resistive switching devices towards brain-inspired computing. Full article

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

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13 pages, 1322 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Stability of Oral Vitamin C Delivery: A Novel Large-Scale Method for Liposomes Production and Encapsulation through Dynamic High-Pressure Microfluidization

by Eugenia Romano, Roberta Palladino, Mariagabriella Cannavale, Erwin Pavel Lamparelli and Barbara Maglione

Nanomaterials 2024, 14(6), 516; https://doi.org/10.3390/nano14060516 - 14 Mar 2024

Viewed by 890

Abstract

In recent years, nanocarriers have been widely used as an effective solution for oral administration of pharmaceuticals. However, there is still an urgent need to speed up their translation to clinical practice. Cost-effective and industrially scalable methodologies are still needed. Herein, the production [...] Read more.

In recent years, nanocarriers have been widely used as an effective solution for oral administration of pharmaceuticals. However, there is still an urgent need to speed up their translation to clinical practice. Cost-effective and industrially scalable methodologies are still needed. Herein, the production of vitamin C-loaded liposomes for nutraceutical purposes has been investigated and optimized by adopting a High-Pressure Homogenizer. Initially, the impact of process parameters on particles size, distributions, and morphology was explored. The findings document that the pressure and cycle manipulation allow for control over liposome size and polydispersity, reaching a maximum encapsulation efficiency exceeding 80%. This significantly improves the storage stability of vitamin C, as demonstrated by monitoring its antioxidant activity. Furthermore, the in vitro simulation of gastrointestinal digestion shows that liposomes could protect the active substance from damage and control its release in the gastrointestinal fluid. Thus, the whole nanodelivery system can contribute to enhancing vitamin C bioavailability. In conclusion, the results indicate that this innovative approach to producing vitamin C liposomes holds promise for clinical translation and industrial scale-up. Indeed, by utilizing food-grade materials and straightforward equipment, it is possible to produce stable and functional liposomes suitable for health products. Full article

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

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22 pages, 6977 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Adsorption of Methylene Blue Dye on Functionalized Multi-Walled Carbon Nanotubes

by Ludovica Ceroni, Stefania Benazzato, Samuel Pressi, Laura Calvillo, Ester Marotta and Enzo Menna

Nanomaterials 2024, 14(6), 522; https://doi.org/10.3390/nano14060522 - 14 Mar 2024

Cited by 1 | Viewed by 786

Abstract

Carbon nanomaterials are promising adsorbents for dye removal from wastewater also due to their possible surface functionalization that, in principle, can increase the adsorption rate and provide regeneration. To investigate the real advantages of functionalization, we synthesized and characterized through IR, TGA, TEM, [...] Read more.

Carbon nanomaterials are promising adsorbents for dye removal from wastewater also due to their possible surface functionalization that, in principle, can increase the adsorption rate and provide regeneration. To investigate the real advantages of functionalization, we synthesized and characterized through IR, TGA, TEM, XPS and DLS measurements a multi-walled carbon nanotube (MWCNT) derivative bearing benzenesulfonate groups (MWCNT-S). The obtained material demonstrated to have good dispersibility in water and better capability to adsorb methylene blue (MB) compared to the pristine MWCNT adsorbent. Adsorption kinetic studies showed a very fast process, with a constant significantly higher with respect not only to that of the unfunctionalized MWCNT adsorbent but also to those of widely used activated carbons. Moreover, the adsorption capacity of MWCNT-S is more than doubled with respect to that of the insoluble pristine MWCNT adsorbent, thanks to the dispersibility of the derivatives, providing a larger available surface, and to the possible electrostatic interactions between the cationic MB and the anionic sulfonate groups. Additionally, the reversibility of ionic interactions disclosed the possibility to release the adsorbed cationic pollutant through competition with salts, not only regenerating the adsorbent, but also recovering the dye. Indeed, by treating the adsorbed material for 1 h with 1 M NaCl, a regeneration capacity of 75% was obtained, demonstrating the validity of this strategy. Full article

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

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14 pages, 6090 KiB

Open AccessEditor’s ChoiceArticle

Cellulose Sulfate Nanofibers for Enhanced Ammonium Removal

by Ken I. Johnson, William Borges, Priyanka R. Sharma, Sunil K. Sharma, Hao-Yen Chang, Mortaga M. Abou-Krisha, Abdulrahman G. Alhamzani and Benjamin S. Hsiao

Nanomaterials 2024, 14(6), 507; https://doi.org/10.3390/nano14060507 - 12 Mar 2024

Viewed by 671

Abstract

In this study, a sulfonation approach using chlorosulfonic acid (CSA) to prepare cellulose sulfate nanofibers (CSNFs) from raw jute fibers is demonstrated. Both elemental sulfur content and zeta potential in the CSNFs are found to increase with increasing CSA content used. However, the [...] Read more.

In this study, a sulfonation approach using chlorosulfonic acid (CSA) to prepare cellulose sulfate nanofibers (CSNFs) from raw jute fibers is demonstrated. Both elemental sulfur content and zeta potential in the CSNFs are found to increase with increasing CSA content used. However, the corresponding crystallinity in the CSNFs decreases with the increasing amount of CSA used due to degradation of cellulose chains under harsh acidic conditions. The ammonium adsorption results from the CSNFs with varying degrees of sulfonation were analyzed using the Langmuir isotherm model, and the analysis showed a very high maximum ammonium adsorption capacity (41.1 mg/g) under neutral pH, comparable to the best value from a synthetic hydrogel in the literature. The high ammonium adsorption capacity of the CSNFs was found to be maintained in a broad acidic range (pH = 2.5 to 6.5). Full article

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

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31 pages, 43899 KiB

Open AccessEditor’s ChoiceArticle

“Polymerization” of Bimerons in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy

by Natsuki Mukai and Andrey O. Leonov

Nanomaterials 2024, 14(6), 504; https://doi.org/10.3390/nano14060504 - 11 Mar 2024

Viewed by 784

Abstract

We re-examine the internal structure of bimerons, which are stabilized in easy-plane chiral magnets and represent coupled states of two merons with the same topological charge

| 1 / 2 |

but with opposite vorticity and the polarity. We find that, in addition [...] Read more.

We re-examine the internal structure of bimerons, which are stabilized in easy-plane chiral magnets and represent coupled states of two merons with the same topological charge

| 1 / 2 |

but with opposite vorticity and the polarity. We find that, in addition to the vortices and antivortices, bimerons feature circular regions which are located behind the anti-vortices and bear the rotational sense opposite to the rotational sense chosen by the Dzyaloshinskii–Moriya interaction. In an attempt to eliminate these wrong-twist regions with an excess of positive energy density, bimerons assemble into chains, and as such exhibit an attracting interaction potential. As an alternative to chains, we demonstrate the existence of ring-shaped bimeron clusters of several varieties. In some rings, bimeron dipoles are oriented along the circle and swirl clockwise and/or counterclockwise (dubbed “roundabouts”). Moreover, a central meron encircled by the outer bimerons may possess either positive or negative polarity. In other rings, the bimeron dipoles point towards the center of a ring and consequently couple to the central meron (dubbed “crossings”). We point out that the ringlike solutions for baryons obtained within the Skyrme model of pions, although driven by the same tendency of the energy reduction, yield only one type of bimeron rings. The conditions of stability applied to the described bimeron rings are additionally extended to bimeron networks when bimerons fill the whole space of two-dimensional samples and exhibit combinations of rings and chains dispersed with different spatial density (dubbed bimeron “polymers”). In particular, bimeron crystals with hexagonal and the square bimeron orderings are possible when the sides of the unit cells represent chains of bimerons joined in intersections with three or four bimerons, respectively; otherwise, bimeron networks represent disordered bimeron structures. Moreover, we scrutinize the inter-transformations between hexagonal Skyrmion lattices and disordered bimeron polymers occuring via nucleation and mutual annihilation of merons within the cell boundaries. Our theory provides clear directions for experimental studies of bimeron orderings in different condensed-matter systems with quasi-two-dimensional geometries. Full article

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

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14 pages, 3643 KiB

Open AccessEditor’s ChoiceArticle

A Long-Term Study on the Bactericidal Effect of ZrN-Cu Nanostructured Coatings Deposited by an Industrial Physical Vapor Deposition System

by Sahand Behrangi, Eva Staňková, Ivo Sedláček, Lucie Šimoníková, Pavel Souček, Vilma Buršíková, Vjačeslav Sochora, Karel Novotný and Petr Vašina

Nanomaterials 2024, 14(6), 496; https://doi.org/10.3390/nano14060496 - 10 Mar 2024

Viewed by 802

Abstract

ZrN-Cu coatings containing two different amounts of Cu (~11 at.% and ~25 at.%) were deposited using an industrial physical vapor deposition (PVD) system. The as-deposited coatings exhibited 100% bactericidal efficiency against Escherichia coli CCM 3988 for an exposure time of 40 min. Subsequently, [...] Read more.

ZrN-Cu coatings containing two different amounts of Cu (~11 at.% and ~25 at.%) were deposited using an industrial physical vapor deposition (PVD) system. The as-deposited coatings exhibited 100% bactericidal efficiency against Escherichia coli CCM 3988 for an exposure time of 40 min. Subsequently, the samples were attached onto our faculty’s door handles for six months to study the coatings’ long-term effectiveness and durability under actual operational conditions. The samples were periodically evaluated and it was observed that the coatings with 25 at.% Cu performed better than the ones with 11 at.% Cu. For example, following 15 days of being touched, the bactericidal effectiveness of the sample containing 25 at.% Cu dropped to 65% while it fell to 42% for the sample containing 11 at.%. After 6 months, however, both samples showed bactericidal efficiency of ~16–20%. The bactericidal efficiency of the samples touched for 6 months was successfully restored by polishing them. Furthermore, a group of samples was kept untouched and was also evaluated. The untouched samples with Cu content of ~25 at.% did not show any drop in their bactericidal properties after 6 months. ZrN-Cu coatings were concluded to be promising materials for self-sanitizing application on high-touch surfaces. Full article

(This article belongs to the Special Issue Nanocoating for Antibacterial Applications)

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14 pages, 3820 KiB

Open AccessEditor’s ChoiceArticle

Regioselectively Carboxylated Cellulose Nanofibril Models from Dissolving Pulp: C6 via TEMPO Oxidation and C2,C3 via Periodate–Chlorite Oxidation

by Mengzhe Guo, James D. Ede, Christie M. Sayes, Jo Anne Shatkin, Nicole Stark and You-Lo Hsieh

Nanomaterials 2024, 14(5), 479; https://doi.org/10.3390/nano14050479 - 06 Mar 2024

Cited by 1 | Viewed by 669

Abstract

Regioselective C6 and C2,C3 carboxylated cellulose nanofibrils (CNFs) have been robustly generated from dissolving pulp, a readily available source of unmodified cellulose, via stoichiometrically optimized 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO)-mediated and sequential sodium periodate-sodium chlorite (PC) oxidation coupled with high-speed blending. Both regioselectively optimized carboxylated CNF [...] Read more.

Regioselective C6 and C2,C3 carboxylated cellulose nanofibrils (CNFs) have been robustly generated from dissolving pulp, a readily available source of unmodified cellulose, via stoichiometrically optimized 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO)-mediated and sequential sodium periodate-sodium chlorite (PC) oxidation coupled with high-speed blending. Both regioselectively optimized carboxylated CNF series possess the widest ranges of comparable charges (0.72–1.48 mmol/g for T-CNFs vs. 0.72–1.10 mmol/g for PC-CNFs), but similar ranges of thickness (1.3–2.4 nm for T-CNF, 1.8–2.7 nm PC-CNF), widths (4.6–6.6 nm T-CNF, 5.5–5.9 nm PC-CNF), and lengths (254–481 nm T-CNF, 247–442 nm PC-CNF). TEMPO-mediated oxidation is milder and one-pot, thus more time and process efficient, whereas the sequential periodate–chlorite oxidation produces C2,C3 dialdehyde intermediates that are amenable to further chemical functionalization or post-reactions. These two well-characterized regioselectively carboxylated CNF series represent coherent cellulose nanomaterial models from a single woody source and have served as references for their safety study toward the development of a safer-by-design substance evaluation tool. Full article

(This article belongs to the Special Issue From Biomass to Nanomaterials)

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24 pages, 2443 KiB

Open AccessEditor’s ChoiceReview

An Updated Overview of Silica Aerogel-Based Nanomaterials

by Adelina-Gabriela Niculescu, Dana-Ionela Tudorache, Maria Bocioagă, Dan Eduard Mihaiescu, Tony Hadibarata and Alexandru Mihai Grumezescu

Nanomaterials 2024, 14(5), 469; https://doi.org/10.3390/nano14050469 - 04 Mar 2024

Cited by 1 | Viewed by 1569

Abstract

Silica aerogels have gained much interest due to their unique properties, such as being the lightest solid material, having small pore sizes, high porosity, and ultralow thermal conductivity. Also, the advancements in synthesis methods have enabled the creation of silica aerogel-based composites in [...] Read more.

Silica aerogels have gained much interest due to their unique properties, such as being the lightest solid material, having small pore sizes, high porosity, and ultralow thermal conductivity. Also, the advancements in synthesis methods have enabled the creation of silica aerogel-based composites in combination with different materials, for example, polymers, metals, and carbon-based structures. These new silica-based materials combine the properties of silica with the other materials to create a new and reinforced architecture with significantly valuable uses in different fields. Therefore, the importance of silica aerogels has been emphasized by presenting their properties, synthesis process, composites, and numerous applications, offering an updated background for further research in this interdisciplinary domain. Full article

(This article belongs to the Collection Metallic and Metal Oxide Nanohybrids and Their Applications)

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30 pages, 4620 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Tactile Sensory Systems: Mechanisms, Fabrication, and Applications

by Jianguo Xi, Huaiwen Yang, Xinyu Li, Ruilai Wei, Taiping Zhang, Lin Dong, Zhenjun Yang, Zuqing Yuan, Junlu Sun and Qilin Hua

Nanomaterials 2024, 14(5), 465; https://doi.org/10.3390/nano14050465 - 04 Mar 2024

Viewed by 1703

Abstract

Flexible electronics is a cutting-edge field that has paved the way for artificial tactile systems that mimic biological functions of sensing mechanical stimuli. These systems have an immense potential to enhance human–machine interactions (HMIs). However, tactile sensing still faces formidable challenges in delivering [...] Read more.

Flexible electronics is a cutting-edge field that has paved the way for artificial tactile systems that mimic biological functions of sensing mechanical stimuli. These systems have an immense potential to enhance human–machine interactions (HMIs). However, tactile sensing still faces formidable challenges in delivering precise and nuanced feedback, such as achieving a high sensitivity to emulate human touch, coping with environmental variability, and devising algorithms that can effectively interpret tactile data for meaningful interactions in diverse contexts. In this review, we summarize the recent advances of tactile sensory systems, such as piezoresistive, capacitive, piezoelectric, and triboelectric tactile sensors. We also review the state-of-the-art fabrication techniques for artificial tactile sensors. Next, we focus on the potential applications of HMIs, such as intelligent robotics, wearable devices, prosthetics, and medical healthcare. Finally, we conclude with the challenges and future development trends of tactile sensors. Full article

(This article belongs to the Special Issue Advances in Flexible Nanoelectronics)

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11 pages, 2842 KiB

Open AccessEditor’s ChoiceArticle

Fish Scale for Wearable, Self-Powered TENG

by Liwei Zhao, Jin Han, Xing Zhang and Chunchang Wang

Nanomaterials 2024, 14(5), 463; https://doi.org/10.3390/nano14050463 - 03 Mar 2024

Viewed by 2840

Abstract

Flexible and wearable devices are attracting more and more attention. Herein, we propose a self-powered triboelectric nanogenerator based on the triboelectric effect of fish scales. As the pressure on the nanogenerator increases, the output voltage of the triboelectric nanogenerator increases. The nanogenerator can [...] Read more.

Flexible and wearable devices are attracting more and more attention. Herein, we propose a self-powered triboelectric nanogenerator based on the triboelectric effect of fish scales. As the pressure on the nanogenerator increases, the output voltage of the triboelectric nanogenerator increases. The nanogenerator can output a voltage of 7.4 V and a short-circuit current of 0.18 μA under a pressure of 50 N. The triboelectric effect of fish scales was argued to be related to the lamellar structure composed of collagen fiber bundles. The nanogenerator prepared by fish scales can sensitively perceive human activities such as walking, finger tapping, and elbow bending. Moreover, fish scales are a biomass material with good biocompatibility with the body. The fish-scale nanogenerator is a kind of flexible, wearable, and self-powered triboelectric nanogenerator showing great prospects in healthcare and body information monitoring. Full article

(This article belongs to the Special Issue Nanoelectronics: Materials, Devices and Applications)

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15 pages, 1819 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of the Orientation and Order Effects on the Thermoelectric Performance of 2D and 3D Perovskites

by Yi-Hsiang Wang, Cheng-Hsien Yeh, I-Ta Hsieh, Po-Yu Yang, Yuan-Wen Hsiao, Hsuan-Ta Wu, Chun-Wei Pao and Chuan-Feng Shih

Nanomaterials 2024, 14(5), 446; https://doi.org/10.3390/nano14050446 - 28 Feb 2024

Viewed by 819

Abstract

Calcium titanium oxide has emerged as a highly promising material for optoelectronic devices, with recent studies suggesting its potential for favorable thermoelectric properties. However, current experimental observations indicate a low thermoelectric performance, with a significant gap between these observations and theoretical predictions. Therefore, [...] Read more.

Calcium titanium oxide has emerged as a highly promising material for optoelectronic devices, with recent studies suggesting its potential for favorable thermoelectric properties. However, current experimental observations indicate a low thermoelectric performance, with a significant gap between these observations and theoretical predictions. Therefore, this study employs a combined approach of experiments and simulations to thoroughly investigate the impact of structural and directional differences on the thermoelectric properties of two-dimensional (2D) and three-dimensional (3D) metal halide perovskites. Two-dimensional (2D) and three-dimensional (3D) metal halide perovskites constitute the focus of examination in this study, where an in-depth exploration of their thermoelectric properties is conducted via a comprehensive methodology incorporating simulations and experimental analyses. The non-equilibrium molecular dynamics simulation (NEMD) was utilized to calculate the thermal conductivity of the perovskite material. Thermal conductivities along both in-plane and out-plane directions of 2D perovskite were computed. The NEMD simulation results show that the thermal conductivity of the 3D perovskite is approximately 0.443 W/mK, while the thermal conductivities of the parallel and vertical oriented 2D perovskites increase with n and range from 0.158 W/mK to 0.215 W/mK and 0.289 W/mK to 0.309 W/mK, respectively. Hence, the thermal conductivity of the 2D perovskites is noticeably lower than the 3D ones. Furthermore, the parallel oriented 2D perovskites exhibit more effective blocking of heat transfer behavior than the perpendicular oriented ones. The experimental results reveal that the Seebeck coefficient of the 2D perovskites reaches 3.79 × 10² µV/K. However, the electrical conductivity of the 2D perovskites is only 4.55 × 10⁻⁵ S/cm, which is one order of magnitude lower than that of the 3D perovskites. Consequently, the calculated thermoelectric figure of merit for the 2D perovskites is approximately 1.41 × 10⁻⁷, slightly lower than that of the 3D perovskites. Full article

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23 pages, 4263 KiB

Open AccessEditor’s ChoiceReview

Zein-Based Nanoparticles as Active Platforms for Sustainable Applications: Recent Advances and Perspectives

by Emilia Oleandro, Mariamelia Stanzione, Giovanna Giuliana Buonocore and Marino Lavorgna

Nanomaterials 2024, 14(5), 414; https://doi.org/10.3390/nano14050414 - 23 Feb 2024

Viewed by 953

Abstract

Nanomaterials, due to their unique structural and functional features, are widely investigated for potential applications in a wide range of industrial sectors. In this context, protein-based nanoparticles, given proteins’ abundance, non-toxicity, and stability, offer a promising and sustainable methodology for encapsulation and protection, [...] Read more.

Nanomaterials, due to their unique structural and functional features, are widely investigated for potential applications in a wide range of industrial sectors. In this context, protein-based nanoparticles, given proteins’ abundance, non-toxicity, and stability, offer a promising and sustainable methodology for encapsulation and protection, and can be used in engineered nanocarriers that are capable of releasing active compounds on demand. Zein is a plant-based protein extracted from corn, and it is biocompatible, biodegradable, and amphiphilic. Several approaches and technologies are currently involved in zein-based nanoparticle preparation, such as antisolvent precipitation, spray drying, supercritical processes, coacervation, and emulsion procedures. Thanks to their peculiar characteristics, zein-based nanoparticles are widely used as nanocarriers of active compounds in targeted application fields such as drug delivery, bioimaging, or soft tissue engineering, as reported by others. The main goal of this review is to investigate the use of zein-based nanocarriers for different advanced applications including food/food packaging, cosmetics, and agriculture, which are attracting researchers’ efforts, and to exploit the future potential development of zein NPs in the field of cultural heritage, which is still relatively unexplored. Moreover, the presented overview focuses on several preparation methods (i.e., antisolvent processes, spry drying), correlating the different analyzed methodologies to NPs’ structural and functional properties and their capability to act as carriers of bioactive compounds, both to preserve their activity and to tune their release in specific working conditions. Full article

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21 pages, 3743 KiB

Open AccessEditor’s ChoiceArticle

Origin of Multiferroism in VOX₂ (X = Cl, Br, I) Monolayers

by Angel Todorov Apostolov, Iliana Naumova Apostolova and Julia Mihailova Wesselinowa

Nanomaterials 2024, 14(5), 408; https://doi.org/10.3390/nano14050408 - 23 Feb 2024

Viewed by 620

Abstract

Based on the proposed microscopic model, we investigate the multiferroic characteristics of VOX₂ (X = Cl, Br, I) monolayers using a Green’s function method. The dependence of the microscopic parameters of the ferroelectric system (pseudo-spin arrangement and flipping rate) on the magnitude [...] Read more.

Based on the proposed microscopic model, we investigate the multiferroic characteristics of VOX₂ (X = Cl, Br, I) monolayers using a Green’s function method. The dependence of the microscopic parameters of the ferroelectric system (pseudo-spin arrangement and flipping rate) on the magnitude and sign of the exchange magnetic interaction along the b-axis and the value of the Dzyaloshinskii–Moria vector have been investigated and qualitatively explained. The possibility of observing a spin-reorientation transition with a change in the character of spin ordering from antiferromagnetic to ferromagnetic is investigated. It is found that the antisymmetric magnetoelectric interaction may be responsible for the spin-reorientation transition without a change in the ordering of magnetic moments. Changing the sign of the exchange magnetic interaction along the b-axis leads to ferromagnetic ordering without observing a spin-reorientation transition. The dependence of isotropic and antisymmetric magnetic interactions on the microscopic parameters of the ferroelectric system is qualitatively explained. A mechanism for the occurrence of the spin-reorientation transition is presented based on the proposed microscopic model. The obtained results qualitatively coincide with Density Functional Theory calculations. Full article

(This article belongs to the Special Issue Multifunctional Nanomaterials Based on Oxide Nanocrystals: Synthesis, Properties and Applications)

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12 pages, 2879 KiB

Open AccessEditor’s ChoiceArticle

Superprotonic Conductivity in a Metalloporphyrin-Based SMOF (Supramolecular Metal–Organic Framework)

by Arkaitz Fidalgo-Marijuan, Idoia Ruiz de Larramendi and Gotzone Barandika

Nanomaterials 2024, 14(5), 398; https://doi.org/10.3390/nano14050398 - 21 Feb 2024

Viewed by 635

Abstract

Metal–organic frameworks and supramolecular metal–organic frameworks (SMOFs) exhibit great potential for a broad range of applications taking advantage of the high surface area and pore sizes and tunable chemistry. In particular, metalloporphyrin-based MOFs and SMOFs are becoming of great importance in many fields [...] Read more.

Metal–organic frameworks and supramolecular metal–organic frameworks (SMOFs) exhibit great potential for a broad range of applications taking advantage of the high surface area and pore sizes and tunable chemistry. In particular, metalloporphyrin-based MOFs and SMOFs are becoming of great importance in many fields due to the bioessential functions of these macrocycles that are being mimicked. On the other hand, during the last years, proton-conducting materials have aroused much interest, and those presenting high conductivity values are potential candidates to play a key role in some solid-state electrochemical devices such as batteries and fuel cells. In this way, using metalloporphyrins as building units we have obtained a new crystalline material with formula [H(bipy)]₂[(MnTPPS)(H₂O)₂]·2bipy·14H₂O, where bipy is 4,4′-bipyidine and TPPS⁴⁻ is the meso-tetra(4-sulfonatephenyl) porphyrin. The crystal structure shows a zig-zag water chain along the [100] direction located between the sulfonate groups of the porphyrin. Taking into account those structural features, the compound was tested for proton conduction by complex electrochemical impedance spectroscopy (EIS). The as-obtained conductivity is 1 × 10⁻² S·cm⁻¹ at 40 °C and 98% relative humidity, which is a remarkably high value. Full article

(This article belongs to the Special Issue Nanoscale Coordination Polymers for Advanced Applications)

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12 pages, 3715 KiB

Open AccessEditor’s ChoiceArticle

Terahertz Detection by Asymmetric Dual Grating Gate Bilayer Graphene FETs with Integrated Bowtie Antenna

by E. Abidi, A. Khan, J. A. Delgado-Notario, V. Clericó, J. Calvo-Gallego, T. Taniguchi, K. Watanabe, T. Otsuji, J. E. Velázquez and Y. M. Meziani

Nanomaterials 2024, 14(4), 383; https://doi.org/10.3390/nano14040383 - 19 Feb 2024

Viewed by 1024

Abstract

An asymmetric dual-grating gate bilayer graphene-based field effect transistor (ADGG-GFET) with an integrated bowtie antenna was fabricated and its response as a Terahertz (THz) detector was experimentally investigated. The device was cooled down to 4.5 K, and excited at different frequencies (0.15, 0.3 [...] Read more.

An asymmetric dual-grating gate bilayer graphene-based field effect transistor (ADGG-GFET) with an integrated bowtie antenna was fabricated and its response as a Terahertz (THz) detector was experimentally investigated. The device was cooled down to 4.5 K, and excited at different frequencies (0.15, 0.3 and 0.6 THz) using a THz solid-state source. The integration of the bowtie antenna allowed to obtain a substantial increase in the photocurrent response (up to 8 nA) of the device at the three studied frequencies as compared to similar transistors lacking the integrated antenna (1 nA). The photocurrent increase was observed for all the studied values of the bias voltage applied to both the top and back gates. Besides the action of the antenna that helps the coupling of THz radiation to the transistor channel, the observed enhancement by nearly one order of magnitude of the photoresponse is also related to the modulation of the hole and electron concentration profiles inside the transistor channel by the bias voltages imposed to the top and back gates. The creation of local n and p regions leads to the formation of homojuctions (

n p

,

p n

or

p p^{+}

) along the channel that strongly affects the overall photoresponse of the detector. Additionally, the bias of both back and top gates could induce an opening of the gap of the bilayer graphene channel that would also contribute to the photocurrent. Full article

(This article belongs to the Special Issue Abridging the CMOS Technology II)

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17 pages, 6532 KiB

Open AccessEditor’s ChoiceArticle

Silver-Sulfamethazine-Conjugated β-Cyclodextrin/Dextran-Coated Magnetic Nanoparticles for Pathogen Inhibition

by Anastasiia B. Shatan, Vitalii Patsula, Hana Macková, Andrii Mahun, Renáta Lehotská, Elena Piecková and Daniel Horák

Nanomaterials 2024, 14(4), 371; https://doi.org/10.3390/nano14040371 - 17 Feb 2024

Viewed by 881

Abstract

In the fight against antibiotic resistance, which is rising to dangerously high levels worldwide, new strategies based on antibiotic-conjugated biocompatible polymers bound to magnetic nanoparticles that allow the drug to be manipulated and delivered to a specific target are being proposed. Here, we [...] Read more.

In the fight against antibiotic resistance, which is rising to dangerously high levels worldwide, new strategies based on antibiotic-conjugated biocompatible polymers bound to magnetic nanoparticles that allow the drug to be manipulated and delivered to a specific target are being proposed. Here, we report the direct surface engineering of nontoxic iron oxide nanoparticles (IONs) using biocompatible dextran (Dex) covalently linked to β-cyclodextrin (β-CD) with the ability to form non-covalent complexes with silver-sulfamethazine (SMT-Ag). To achieve a good interaction of β-CD-modified dextran with the surface of the nanoparticles, it was functionalized with diphosphonic acid (DPA) that provides strong binding to Fe atoms. The synthesized polymers and nanoparticles were characterized by various methods, such as nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and ultraviolet–visible (UV–Vis) spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), atomic absorption spectroscopy (AAS), dynamic light scattering (DLS), etc. The resulting magnetic ION@DPA-Dex-β-CD-SMT-Ag nanoparticles were colloidally stable in water and contained 24 μg of antibiotic per mg of the particles. When tested for in vitro antimicrobial activity on Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and fungi (yeast Candida albicans and mold Aspergillus niger), the particles showed promising potential. Full article

(This article belongs to the Special Issue Antimicrobial and Antioxidant Activity of Nanoparticles)

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14 pages, 7941 KiB

Open AccessEditor’s ChoiceArticle

In Situ Lubrication in Forging of Pure Titanium Using Carbon Supersaturated Die Materials

by Tatsuhiko Aizawa, Tatsuya Funazuka and Tomomi Shiratori

Nanomaterials 2024, 14(4), 363; https://doi.org/10.3390/nano14040363 - 15 Feb 2024

Viewed by 656

Abstract

A new solid lubrication method was proposed for dry forging of pure titanium with high reduction in thickness. A free-carbon tribofilm was formed in situ at the hot spots on the contact interface to protect the die surfaces from severe adhesion of work [...] Read more.

A new solid lubrication method was proposed for dry forging of pure titanium with high reduction in thickness. A free-carbon tribofilm was formed in situ at the hot spots on the contact interface to protect the die surfaces from severe adhesion of work materials. This film consisted of the free carbon, which isolated from the carbon supersaturated die substrate materials, diffused to the contact interface and agglomerated to a thin film. Two different routes of carbon supersaturation process were developed to prepare carbon supersaturated ceramic and metal dies for the dry forging of pure titanium wires. A pure titanium bar was utilized as an easy-to-adherent work material for upsetting in dry and cold. The round bar was upset up to 70% in reduction in thickness with a low friction coefficient from 0.05 to 0.1 in a single stroke. Work hardening was suppressed by this low friction. SEM-EDX, EBSD and Raman spectroscopy were utilized to analyze the contact interface and to understand the role of in situ formed free-carbon films on the low friction and low work hardening during forging. Precise nanostructure analyses were utilized to describe low friction forging behavior commonly observed in these two processes. The in situ solid lubrication mechanism is discussed based on the equivalence between the nitrogen and carbon supersaturation processes. Full article

(This article belongs to the Section Nanofabrication and Nanomanufacturing)

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10 pages, 3169 KiB

Open AccessEditor’s ChoiceArticle

Fully Printed Cellulose Nanofiber–Ag Nanoparticle Composite for High-Performance Humidity Sensor

by Mijin Won, Minhun Jung, Jaehwan Kim and Dong-Soo Kim

Nanomaterials 2024, 14(4), 343; https://doi.org/10.3390/nano14040343 - 10 Feb 2024

Viewed by 789

Abstract

This paper reports a high-performance humidity sensor made using a novel cellulose nanofiber (CNF)–silver nanoparticle (AgNP) sensing material. The interdigital electrode pattern was printed via reverse-offset printing using Ag nano-ink, and the sensing layer on the printed interdigitated electrode (IDE) was formed by [...] Read more.

This paper reports a high-performance humidity sensor made using a novel cellulose nanofiber (CNF)–silver nanoparticle (AgNP) sensing material. The interdigital electrode pattern was printed via reverse-offset printing using Ag nano-ink, and the sensing layer on the printed interdigitated electrode (IDE) was formed by depositing the CNF-AgNP composite via inkjet printing. The structure and morphology of the CNF-AgNP layer are characterized using ultraviolet–visible spectroscopy, an X-ray diffractometer, field emission scanning electron microscopy, energy-dispersive X-ray analysis, and transmission electron microscopy. The humidity-sensing performance of the prepared sensors is evaluated by measuring the impedance changes under the relative humidity variation between 10 and 90% relative humidity. The CNF-AgNP sensor exhibited very sensitive and fast humidity-sensing responses compared to the CNF sensor. The electrode distance effect and the response and recovery times are investigated. The enhanced humidity-sensing performance is reflected in the increased conductivity of the Ag nanoparticles and the adsorption of free water molecules associated with the porous characteristics of the CNF layer. The CNF-AgNP composite enables the development of highly sensitive, fast-responding, reproducible, flexible, and inexpensive humidity sensors. Full article

(This article belongs to the Special Issue Nanomaterials for Flexible and Printed Electronics)

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29 pages, 5582 KiB

Open AccessEditor’s ChoiceArticle

Multifaceted Assessment of Porous Silica Nanocomposites: Unraveling Physical, Structural, and Biological Transformations Induced by Microwave Field Modification

by Aleksandra Strach, Mateusz Dulski, Daniel Wasilkowski, Krzysztof Matus, Karolina Dudek, Jacek Podwórny, Patrycja Rawicka, Vladlens Grebnevs, Natalia Waloszczyk, Anna Nowak, Paulina Poloczek and Sylwia Golba

Nanomaterials 2024, 14(4), 337; https://doi.org/10.3390/nano14040337 - 08 Feb 2024

Viewed by 904

Abstract

In response to the persistent challenge of heavy and noble metal environmental contamination, our research explores a new idea to capture silver through porous spherical silica nanostructures. The aim was realized using microwave radiation at varying power (P = 150 or 800 W) [...] Read more.

In response to the persistent challenge of heavy and noble metal environmental contamination, our research explores a new idea to capture silver through porous spherical silica nanostructures. The aim was realized using microwave radiation at varying power (P = 150 or 800 W) and exposure times (t = 60 or 150 s). It led to the development of a silica surface with enhanced metal-capture capacity. The microwave-assisted silica surface modification influences the notable changes within the carrier but also enforces the crystallization process of silver nanoparticles with different morphology, structure, and chemical composition. Microwave treatment can also stimulate the formation of core–shell bioactive Ag/Ag₂CO₃ heterojunctions. Due to the silver nanoparticles’ sphericity and silver carbonate’s presence, the modified nanocomposites exhibited heightened toxicity against common microorganisms, such as E. coli and S. epidermidis. Toxicological assessments, including minimum inhibitory concentration (MIC) and half-maximal inhibitory concentration (IC₅₀) determinations, underscored the efficacy of the nanocomposites. This research represents a significant stride in addressing pollution challenges. It shows the potential of microwave-modified silicas in the fight against environmental contamination. Microwave engineering underscores a sophisticated approach to pollution remediation and emphasizes the pivotal role of nanotechnology in shaping sustainable solutions for environmental stewardship. Full article

(This article belongs to the Special Issue Biomedical Applications of Metallic Nanoparticles)

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15 pages, 4559 KiB

Open AccessEditor’s ChoiceArticle

Imaging of Endometriotic Lesions Using cRGD-MN Probe in a Mouse Model of Endometriosis

by Nazanin Talebloo, M. Ariadna Ochoa Bernal, Elizabeth Kenyon, Christiane L. Mallett, Sujan Kumar Mondal, Asgerally Fazleabas and Anna Moore

Nanomaterials 2024, 14(3), 319; https://doi.org/10.3390/nano14030319 - 05 Feb 2024

Viewed by 892

Abstract

Approximately 10% of women suffer from endometriosis during their reproductive years. This disease is a chronic debilitating condition whose etiology for lesion implantation and survival heavily relies on adhesion and angiogenic factors. Currently, there are no clinically approved agents for its detection. In [...] Read more.

Approximately 10% of women suffer from endometriosis during their reproductive years. This disease is a chronic debilitating condition whose etiology for lesion implantation and survival heavily relies on adhesion and angiogenic factors. Currently, there are no clinically approved agents for its detection. In this study, we evaluated cRGD-peptide-conjugated nanoparticles (RGD-Cy5.5-MN) to detect lesions using magnetic resonance imaging (MRI) in a mouse model of endometriosis. We utilized a luciferase-expressing murine suture model of endometriosis. Imaging was performed before and after 24 h following the intravenous injection of RGD-Cy5.5-MN or control nanoparticles (Cy5.5-MN). Next, we performed biodistribution of RGD-Cy5.5-MN and correlative fluorescence microscopy of lesions stained for CD34. Tissue iron content was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Our results demonstrated that targeting endometriotic lesions with RGD-Cy5.5-MN resulted in a significantly higher delta T2* upon its accumulation compared to Cy5.5-MN. ICP-OES showed significantly higher iron content in the lesions of the animals in the experimental group compared to the lesions of the animals in the control group. Histology showed colocalization of Cy5.5 signal from RGD-Cy5.5-MN with CD34 in the lesions pointing to the targeted nature of the probe. This work offers initial proof-of-concept for targeting angiogenesis in endometriosis which can be useful for potential clinical diagnostic and therapeutic approaches for treating this disease. Full article

(This article belongs to the Section Biology and Medicines)

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14 pages, 3175 KiB

Open AccessEditor’s ChoiceArticle

Density Functional Theory Study of Methanol Steam Reforming on Pt₃Sn(111) and the Promotion Effect of a Surface Hydroxy Group

by Ping He, Houyu Zhu, Qianyao Sun, Ming Li, Dongyuan Liu, Rui Li, Xiaoqing Lu, Wen Zhao, Yuhua Chi, Hao Ren and Wenyue Guo

Nanomaterials 2024, 14(3), 318; https://doi.org/10.3390/nano14030318 - 05 Feb 2024

Viewed by 733

Abstract

Methanol steam reforming (MSR) is studied on a Pt₃Sn surface using the density functional theory (DFT). An MSR network is mapped out, including several reaction pathways. The main pathway proposed is CH₃OH + OH → CH₃O → [...] Read more.

Methanol steam reforming (MSR) is studied on a Pt₃Sn surface using the density functional theory (DFT). An MSR network is mapped out, including several reaction pathways. The main pathway proposed is CH₃OH + OH → CH₃O → CH₂O → CH₂O + OH → CH₂OOH → CHOOH → COOH → COOH + OH → CO₂ + H₂O. The adsorption strengths of CH₃OH, CH₂O, CHOOH, H₂O and CO₂ are relatively weak, while other intermediates are strongly adsorbed on Pt₃Sn(111). H₂O decomposition to OH is the rate-determining step on Pt₃Sn(111). The promotion effect of the OH group is remarkable on the conversions of CH₃OH, CH₂O and trans-COOH. In particular, the activation barriers of the O–H bond cleavage (e.g., CH₃OH → CH₃O and trans-COOH → CO₂) decrease substantially by ~1 eV because of the involvement of OH. Compared with the case of MSR on Pt(111), the generation of OH from H₂O decomposition is more competitive on Pt₃Sn(111), and the presence of abundant OH facilitates the combination of CO with OH to generate COOH, which accounts for the improved CO tolerance of the PtSn alloy over pure Pt. Full article

(This article belongs to the Special Issue Computational Approaches to Electronic Structures and Properties of Nanomaterials)

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12 pages, 7256 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Visualization of Photogenerated Carriers on an Avalanche Photodiode Surface Using Ultrafast Scanning Electron Microscopy

by Yuan Tian, Dong Yang, Yu Ma, Zhongwen Li, Jun Li, Zhen Deng, Huanfang Tian, Huaixin Yang, Shuaishuai Sun and Jianqi Li

Nanomaterials 2024, 14(3), 310; https://doi.org/10.3390/nano14030310 - 03 Feb 2024

Viewed by 1069

Abstract

The spatiotemporal evolution of photogenerated charge carriers on surfaces and at interfaces of photoactive materials is an important issue for understanding fundamental physical processes in optoelectronic devices and advanced materials. Conventional optical probe-based microscopes that provide indirect information about the dynamic behavior of [...] Read more.

The spatiotemporal evolution of photogenerated charge carriers on surfaces and at interfaces of photoactive materials is an important issue for understanding fundamental physical processes in optoelectronic devices and advanced materials. Conventional optical probe-based microscopes that provide indirect information about the dynamic behavior of photogenerated carriers are inherently limited by their poor spatial resolution and large penetration depth. Herein, we develop an ultrafast scanning electron microscope (USEM) with a planar emitter. The photoelectrons per pulse in this USEM can be two orders of magnitude higher than that of a tip emitter, allowing the capture of high-resolution spatiotemporal images. We used the contrast change of the USEM to examine the dynamic nature of surface carriers in an InGaAs/InP avalanche photodiode (APD) after femtosecond laser excitation. It was observed that the photogenerated carriers showed notable longitudinal drift, lateral diffusion, and carrier recombination associated with the presence of photovoltaic potential at the surface. This work demonstrates an in situ multiphysics USEM platform with the capability to stroboscopically record carrier dynamics in space and time. Full article

(This article belongs to the Special Issue Advanced Characterization Techniques for Nanomaterials)

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22 pages, 2713 KiB

Open AccessEditor’s ChoiceReview

Titanium Dioxide Nanoparticles Doped with Iron for Water Treatment via Photocatalysis: A Review

by Domenico Rosa, Nigar Abbasova and Luca Di Palma

Nanomaterials 2024, 14(3), 293; https://doi.org/10.3390/nano14030293 - 31 Jan 2024

Cited by 1 | Viewed by 958

Abstract

Iron-doped titanium dioxide nanoparticles are widely employed for photocatalytic applications under visible light due to their promising performance. Nevertheless, the manufacturing process, the role of Fe³⁺ ions within the crystal lattice of titanium dioxide, and their impact on operational parameters are still [...] Read more.

Iron-doped titanium dioxide nanoparticles are widely employed for photocatalytic applications under visible light due to their promising performance. Nevertheless, the manufacturing process, the role of Fe³⁺ ions within the crystal lattice of titanium dioxide, and their impact on operational parameters are still a subject of controversy. Based on these assumptions, the primary objective of this review is to delineate the role of iron, ascertain the optimal quantity, and elucidate its influence on the main photocatalysis parameters, including nanoparticle size, band gap, surface area, anatase–rutile transition, and point of zero charge. Moreover, an optimized synthesis method based on comprehensive data and insights from the existing literature is proposed, focusing exclusively on iron-doped titanium oxide while excluding other dopant variants. Full article

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

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13 pages, 6108 KiB

Open AccessEditor’s ChoiceArticle

Nonthermal Plasma Synthesis of Metallic Ti Nanocrystals

by Qiaomiao Tu, David L. Poerschke and Uwe R. Kortshagen

Nanomaterials 2024, 14(3), 264; https://doi.org/10.3390/nano14030264 - 26 Jan 2024

Viewed by 760

Abstract

Nanoscale metallic titanium (Ti) offers unique energetic and biocompatible characteristics for the aerospace and biomedical industries. A rapid and sustainable method to form purified Ti nanocrystals is still in demand due to their high oxygen affinity. Herein, we report the production of highly [...] Read more.

Nanoscale metallic titanium (Ti) offers unique energetic and biocompatible characteristics for the aerospace and biomedical industries. A rapid and sustainable method to form purified Ti nanocrystals is still in demand due to their high oxygen affinity. Herein, we report the production of highly purified Ti nanoparticles with a nonequilibrium face center cubic (FCC) structure from titanium tetrachloride (TiCl₄) via a capacitively coupled plasma (CCP) route. Furthermore, we demonstrate a secondary H₂ treatment plasma as an effective strategy to improve the air stability of a thin layer of nanoparticles by further removal of chlorine from the particle surface. Hexagonal and cubic-shaped Ti nanocrystals of high purity were maintained in the air after the secondary H₂ plasma treatment. The FCC phase potentially originates from small-sized grains in the initial stage of nucleation inside the plasma environment, which is revealed by a size evolution study with variations of plasma power input. Full article

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

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19 pages, 5934 KiB

Open AccessEditor’s ChoiceReview

Tissue Nanotransfection Silicon Chip and Related Electroporation-Based Technologies for In Vivo Tissue Reprogramming

by Yi Xuan, Cong Wang, Subhadip Ghatak and Chandan K. Sen

Nanomaterials 2024, 14(2), 217; https://doi.org/10.3390/nano14020217 - 19 Jan 2024

Viewed by 1746

Abstract

Tissue nanotransfection (TNT), a cutting-edge technique of in vivo gene therapy, has gained substantial attention in various applications ranging from in vivo tissue reprogramming in regenerative medicine, and wound healing to cancer treatment. This technique harnesses the advancements in the semiconductor processes, facilitating [...] Read more.

Tissue nanotransfection (TNT), a cutting-edge technique of in vivo gene therapy, has gained substantial attention in various applications ranging from in vivo tissue reprogramming in regenerative medicine, and wound healing to cancer treatment. This technique harnesses the advancements in the semiconductor processes, facilitating the integration of conventional transdermal gene delivery methods—nanoelectroporation and microneedle technologies. TNT silicon chips have demonstrated considerable promise in reprogramming fibroblast cells of skin in vivo into vascular or neural cells in preclinical studies to assist in the recovery of injured limbs and damaged brain tissue. More recently, the application of TNT chips has been extended to the area of exosomes, which are vital for intracellular communication to track their functionality during the wound healing process. In this review, we provide an in-depth examination of the design, fabrication, and applications of TNT silicon chips, alongside a critical analysis of the electroporation-based gene transfer mechanisms. Additionally, the review discussed the existing limitations and challenges in the current technique, which may project future trajectories in the landscape of gene therapy. Through this exploration, the review aims to shed light on the prospects of TNT in the broader context of gene therapy and tissue regeneration. Full article

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14 pages, 2269 KiB

Open AccessEditor’s ChoiceArticle

Near-Plasma Chemical Surface Engineering

by Paula Navascués, Urs Schütz, Barbara Hanselmann and Dirk Hegemann

Nanomaterials 2024, 14(2), 195; https://doi.org/10.3390/nano14020195 - 15 Jan 2024

Viewed by 906

Abstract

As a new trend in plasma surface engineering, plasma conditions that allow more-defined chemical reactions at the surface are being increasingly investigated. This is achieved by avoiding high energy deposition via ion bombardment during direct plasma exposure (DPE) causing destruction, densification, and a [...] Read more.

As a new trend in plasma surface engineering, plasma conditions that allow more-defined chemical reactions at the surface are being increasingly investigated. This is achieved by avoiding high energy deposition via ion bombardment during direct plasma exposure (DPE) causing destruction, densification, and a broad variety of chemical reactions. In this work, a novel approach is introduced by placing a polymer mesh with large open area close to the plasma–sheath boundary above the plasma-treated sample, thus enabling near-plasma chemistry (NPC). The mesh size effectively extracts ions, while reactive neutrals, electrons, and photons still reach the sample surface. The beneficial impact of this on the plasma activation of poly (tetrafluoroethylene) (PTFE) to enhance wettability and on the plasma polymerization of siloxanes, combined with the etching of residual hydrocarbons to obtain highly porous SiOx coatings at low temperatures, is discussed. Characterization of the treated samples indicates a predominant chemical modification yielding enhanced film structures and durability. Full article

(This article belongs to the Special Issue New Trends in Plasma Technology for Nanomaterials and Applications)

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24 pages, 6825 KiB

Open AccessEditor’s ChoiceReview

Progress of One-Dimensional SiC Nanomaterials: Design, Fabrication and Sensing Applications

by Haiyan Liu, Xiaoshan Zhang, Nana Xu, Cheng Han, Nan Wu, Bing Wang and Yingde Wang

Nanomaterials 2024, 14(2), 187; https://doi.org/10.3390/nano14020187 - 13 Jan 2024

Viewed by 942

Abstract

One-dimensional silicon carbide (SiC) nanomaterials hold great promise for a series of applications, such as nanoelectronic devices, sensors, supercapacitors, and catalyst carriers, attributed to their unique electrical, mechanical, and physicochemical properties. Recent progress in their design and fabrication has led to a deep [...] Read more.

One-dimensional silicon carbide (SiC) nanomaterials hold great promise for a series of applications, such as nanoelectronic devices, sensors, supercapacitors, and catalyst carriers, attributed to their unique electrical, mechanical, and physicochemical properties. Recent progress in their design and fabrication has led to a deep understanding of the structural evolution and structure–property correlation. Several unique attributes, such as high electron mobility, offer SiC nanomaterials an opportunity in the design of SiC-based sensors with high sensitivity. In this review, a brief introduction to the structure and properties of SiC is first presented, and the latest progress in design and fabrication of one-dimensional SiC nanomaterials is summarized. Then, the sensing applications of one-dimensional SiC nanomaterials are reviewed. Finally, our perspectives on the important research direction and future opportunities of one-dimensional SiC nanomaterial for sensors are proposed. Full article

(This article belongs to the Special Issue Advances in Micro and Nanofiber: Fabrication, Properties and Applications)

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13 pages, 4326 KiB

Open AccessEditor’s ChoiceArticle

Controlled Crystallinity of a Sn-Doped α-Ga₂O₃ Epilayer Using Rapidly Annealed Double Buffer Layers

by Kyoung-Ho Kim, Yun-Ji Shin, Seong-Min Jeong, Heesoo Lee and Si-Young Bae

Nanomaterials 2024, 14(2), 178; https://doi.org/10.3390/nano14020178 - 12 Jan 2024

Viewed by 824

Abstract

Double buffer layers composed of (Al_xGa_1−x)₂O₃/Ga₂O₃ structures were employed to grow a Sn-doped α-Ga₂O₃ epitaxial thin film on a sapphire substrate using mist chemical vapor deposition. The insertion of [...] Read more.

Double buffer layers composed of (Al_xGa_1−x)₂O₃/Ga₂O₃ structures were employed to grow a Sn-doped α-Ga₂O₃ epitaxial thin film on a sapphire substrate using mist chemical vapor deposition. The insertion of double buffer layers improved the crystal quality of the upper-grown Sn-doped α-Ga₂O₃ thin films by blocking dislocation generated by the substrates. Rapid thermal annealing was conducted for the double buffer layers at phase transition temperatures of 700–800 °C. The slight mixing of κ and β phases further improved the crystallinity of the grown Sn-Ga₂O₃ thin film through local lateral overgrowth. The electron mobility of the Sn-Ga₂O₃ thin films was also significantly improved due to the smoothened interface and the diffusion of Al. Therefore, rapid thermal annealing with the double buffer layer proved advantageous in achieving strong electrical properties for Ga₂O₃ semiconductor devices within a shorter processing time. Full article

(This article belongs to the Special Issue Advances in Wide-Bandgap Semiconductor Nanomaterials)

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10 pages, 2390 KiB

Open AccessEditor’s ChoiceArticle

Short-Time Magnetron Sputtering for the Development of Carbon–Palladium Nanocomposites

by Florian Knabl, Nikolaos Kostoglou, Velislava Terziyska, Steven Hinder, Mark Baker, Etienne Bousser, Claus Rebholz and Christian Mitterer

Nanomaterials 2024, 14(2), 164; https://doi.org/10.3390/nano14020164 - 12 Jan 2024

Viewed by 1157

Abstract

In recent nanomaterials research, combining nanoporous carbons with metallic nanoparticles, like palladium (Pd), has emerged as a focus due to their potential in energy, environmental and biomedical fields. This study presents a novel approach for synthesizing Pd-decorated carbons using magnetron sputter deposition. This [...] Read more.

In recent nanomaterials research, combining nanoporous carbons with metallic nanoparticles, like palladium (Pd), has emerged as a focus due to their potential in energy, environmental and biomedical fields. This study presents a novel approach for synthesizing Pd-decorated carbons using magnetron sputter deposition. This method allows for the functionalization of nanoporous carbon surfaces with Pd nano-sized islands, creating metal–carbon nanocomposites through brief deposition times of up to 15 s. The present research utilized direct current magnetron sputtering to deposit Pd islands on a flexible activated carbon cloth substrate. The surface chemistry, microstructure, morphology and pore structure were analyzed using a variety of material characterization techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, gas sorption analysis and scanning electron microscopy. The results showed Pd islands of varying sizes distributed across the cloth’s carbon fibers, achieving high-purity surface modifications without the use of chemicals. The synthesis method preserves the nanoporous structure of the carbon cloth substrate while adding functional Pd islands, which could be potentially useful in emerging fields like hydrogen storage, fuel cells and biosensors. This approach demonstrates the possibility of creating high-quality metal–carbon composites using a simple, clean and economical method, expanding the possibilities for future nanomaterial-based applications. Full article

(This article belongs to the Section Nanocomposite Materials)

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14 pages, 3913 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Consolidation of Spray-Dried Amorphous Calcium Phosphate by Ultrafast Compression: Chemical and Structural Overview

by Sylvain Le Grill, Christophe Drouet, Olivier Marsan, Yannick Coppel, Vincent Mazel, Marie-Claire Barthelemy and Fabien Brouillet

Nanomaterials 2024, 14(2), 152; https://doi.org/10.3390/nano14020152 - 10 Jan 2024

Cited by 1 | Viewed by 799

Abstract

A large amount of research in orthopedic and maxillofacial domains is dedicated to the development of bioactive 3D scaffolds. This includes the search for highly resorbable compounds, capable of triggering cell activity and favoring bone regeneration. Considering the phosphocalcic nature of bone mineral, [...] Read more.

A large amount of research in orthopedic and maxillofacial domains is dedicated to the development of bioactive 3D scaffolds. This includes the search for highly resorbable compounds, capable of triggering cell activity and favoring bone regeneration. Considering the phosphocalcic nature of bone mineral, these aims can be achieved by the choice of amorphous calcium phosphates (ACPs). Because of their metastable property, these compounds are however to-date seldom used in bulk form. In this work, we used a non-conventional “cold sintering” approach based on ultrafast low-pressure RT compaction to successfully consolidate ACP pellets while preserving their amorphous nature (XRD). Complementary spectroscopic analyses (FTIR, Raman, solid-state NMR) and thermal analyses showed that the starting powder underwent slight physicochemical modifications, with a partial loss of water and local change in the HPO₄^2- ion environment. The creation of an open porous structure, which is especially adapted for non-load bearing bone defects, was also observed. Moreover, the pellets obtained exhibited sufficient mechanical resistance allowing for manipulation, surgical placement and eventual cutting/reshaping in the operation room. Three-dimensional porous scaffolds of cold-sintered reactive ACP, fabricated through this low-energy, ultrafast consolidation process, show promise toward the development of highly bioactive and tailorable biomaterials for bone regeneration, also permitting combinations with various thermosensitive drugs. Full article

(This article belongs to the Special Issue Synthesis and Spectral Characterization of Ceramics and Nanomaterials)

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18 pages, 24917 KiB

Open AccessEditor’s ChoiceArticle

Using Hierarchically Structured, Nanoporous Particles as Building Blocks for NCM111 Cathodes

by Werner Bauer, Marcus Müller, Luca Schneider, Marcel Häringer, Nicole Bohn, Joachim R. Binder, Julian Klemens, Philip Scharfer, Wilhelm Schabel and Helmut Ehrenberg

Nanomaterials 2024, 14(2), 134; https://doi.org/10.3390/nano14020134 - 06 Jan 2024

Cited by 1 | Viewed by 916

Abstract

Nanoparticles have many advantages as active materials, such as a short diffusion length, low charge transfer resistance, or a reduced probability of cracking. However, their low packing density makes them unsuitable for commercial battery applications. Hierarchically structured microparticles are synthesized from nanoscale primary [...] Read more.

Nanoparticles have many advantages as active materials, such as a short diffusion length, low charge transfer resistance, or a reduced probability of cracking. However, their low packing density makes them unsuitable for commercial battery applications. Hierarchically structured microparticles are synthesized from nanoscale primary particles by targeted aggregation. Due to their open accessible porosity, they retain the advantages of nanomaterials but can be packed much more densely. However, the intrinsic porosity of the secondary particles leads to limitations in processing properties and increases the overall porosity of the electrode, which must be balanced against the improved rate stability and increased lifetime. This is demonstrated for an established cathode material for lithium-ion batteries (LiNi_0.33Co_0.33Mn_0.33O₂, NCM111). For active materials with low electrical or ionic conductivity, especially post-lithium systems, hierarchically structured particles are often the only way to produce competitive electrodes. Full article

(This article belongs to the Special Issue Functionalized Nanostructures for Novel Energy Storage Systems)

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20 pages, 5487 KiB

Open AccessEditor’s ChoiceArticle

Nitrogen-Doped Graphene Materials with High Electrical Conductivity Produced by Electrochemical Exfoliation of Graphite Foil

by Hela Kammoun, Benjamin D. Ossonon and Ana C. Tavares

Nanomaterials 2024, 14(1), 123; https://doi.org/10.3390/nano14010123 - 04 Jan 2024

Viewed by 1608

Abstract

Nitrogen-doped graphene-based materials are of utmost importance in sensing and energy conversion devices due to their unique physicochemical properties. However, the presence of defects such as pyrrolic nitrogen and oxygenated functional groups reduces their electrical conductivity. Herein, a two-step approach based on the [...] Read more.

Nitrogen-doped graphene-based materials are of utmost importance in sensing and energy conversion devices due to their unique physicochemical properties. However, the presence of defects such as pyrrolic nitrogen and oxygenated functional groups reduces their electrical conductivity. Herein, a two-step approach based on the electrochemical exfoliation of graphite foils in aqueous mixed electrolytes followed by thermal reduction at 900 °C is used to prepare high-quality few layers of N-doped graphene-based materials. The exfoliations were conducted in 0.1 M (NH₄)₂SO₄ or H₂SO₄ and HNO₃ (5 mM or 0.1 M) electrolytes mixtures and the HNO₃ vol% varied. Chemical analysis demonstrated that the as-prepared graphene oxides contain nitro and amine groups. Thermal reduction is needed for substitutional N-doping. Nitrogen and oxygen surface concentrations vary between 0.23–0.96% and 3–8%, respectively. Exfoliation in (NH₄)₂SO₄ and/or 5 mM HNO₃ favors the formation of pyridinic-N (10–40% of the total N), whereas 1 M HNO₃ favors the formation of graphitic-N (≈60%). The electrical conductivity ranges between 166–2705 Scm⁻¹. Raman spectroscopy revealed a low density of defects (I_D/I_G ratio between 0.1 and 0.7) and that most samples are composed of mono-to-bilayer graphene-based materials (I_G/I_2D integrated intensities ratio). Structural and compositional stability of selected samples after storage in air for three months is demonstrated. These results confirm the high quality of the synthesized undoped and N-doped graphene-type materials. Full article

(This article belongs to the Special Issue Electronic Applications of Graphene-Based Composites)

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20 pages, 5164 KiB

Open AccessEditor’s ChoiceArticle

Novel Nanostructured Pd/Co-Alumina Materials for the Catalytic Oxidation of Atmospheric Pollutants

by Eleni F. Iliopoulou, Eleni Pachatouridou and Angelos A. Lappas

Nanomaterials 2024, 14(1), 124; https://doi.org/10.3390/nano14010124 - 04 Jan 2024

Viewed by 691

Abstract

Cobalt-doped alumina catalysts were prepared using different methods, either conventional wet impregnation (WI) and/or advanced spray impregnation (SI), and they were evaluated as novel oxidation catalysts for CO and MeOH oxidation. The spray impregnation technique was used with the aim of achieving the [...] Read more.

Cobalt-doped alumina catalysts were prepared using different methods, either conventional wet impregnation (WI) and/or advanced spray impregnation (SI), and they were evaluated as novel oxidation catalysts for CO and MeOH oxidation. The spray impregnation technique was used with the aim of achieving the synthesis of core–shell catalytic nanostructures to secure the chemical/thermal stability of active sites on the catalyst carrier. The catalysts were further promoted with a low Pd content (0.5 wt.%) incorporated via either incipient wetness impregnation (DI) or spray impregnation. The results revealed the superior performance of the spray-impregnated catalysts (Co/γ-Al₂O₃-SI) for both reactions. The deposition of Co oxide on the outer surface of the alumina particle (SEM images) and the availability of the active Co phase resulted in the enhancement of the Co/γ-Al₂O₃ catalysts’ oxidation activity. Pd incorporation increased the catalysts’ reducibility (TPR-H₂) and improved the catalysts’ performance for both reactions. However, the Pd incorporation method affected the catalytic performance; with the SI method, the active phase of Co₃O₄ was probably covered with PdO and was not available for the oxidation reactions. On the contrary, the incorporation of Pd with the DI method resulted in a better dispersion of PdO all over the Co/Al catalyst surface, maintaining available Co active sites and a better Pd-Co interaction. MeOH desorption studies revealed the methanol oxidation mechanism: the Co/Al catalysts promoted the partial oxidation of MeOH to formaldehyde (HCHO) and dehydration to dimethyl ether (DME), while the Pd-based Co/Al catalysts enhanced the complete oxidation of methanol to CO₂ and H₂O. Full article

(This article belongs to the Special Issue Nanocatalysis for Environmental Protection, Energy, and Green Chemistry, Volume II)

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12 pages, 1751 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

3D Magnetization Textures: Toroidal Magnetic Hopfion Stability in Cylindrical Samples

by Konstantin Guslienko

Nanomaterials 2024, 14(1), 125; https://doi.org/10.3390/nano14010125 - 04 Jan 2024

Viewed by 842

Abstract

Topologically non-trivial magnetization configurations in ferromagnetic materials on the nanoscale, such as hopfions, skyrmions, and vortices, have attracted considerable attention of researchers during the last few years. In this article, by applying the theory of micromagnetism, I demonstrate that the toroidal hopfion magnetization [...] Read more.

Topologically non-trivial magnetization configurations in ferromagnetic materials on the nanoscale, such as hopfions, skyrmions, and vortices, have attracted considerable attention of researchers during the last few years. In this article, by applying the theory of micromagnetism, I demonstrate that the toroidal hopfion magnetization configuration is a metastable state of a thick cylindrical ferromagnetic nanodot or a nanowire of a finite radius. The existence of this state is a result of the competition among exchange, magnetostatic, and magnetic anisotropy energies. The Dzyaloshinskii–Moriya exchange interaction and surface magnetic anisotropy are of second importance for the hopfion stabilization. The toroidal hopfion metastable magnetization configuration may be reached in the process of remagnetizing the sample by applying an external magnetic field along the cylindrical axis. Full article

(This article belongs to the Special Issue Magnetism and Magnetic Properties of Nanomaterials)

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14 pages, 2959 KiB

Open AccessEditor’s ChoiceArticle

Impact of Single-Walled Carbon Nanotube Functionalization on Ion and Water Molecule Transport at the Nanoscale

by Alia Mejri, Nicolas Arroyo, Guillaume Herlem, John Palmeri, Manoel Manghi, François Henn and Fabien Picaud

Nanomaterials 2024, 14(1), 117; https://doi.org/10.3390/nano14010117 - 03 Jan 2024

Cited by 1 | Viewed by 975

Abstract

Nanofluidics has a very promising future owing to its numerous applications in many domains. It remains, however, very difficult to understand the basic physico-chemical principles that control the behavior of solvents confined in nanometric channels. Here, water and ion transport in carbon nanotubes [...] Read more.

Nanofluidics has a very promising future owing to its numerous applications in many domains. It remains, however, very difficult to understand the basic physico-chemical principles that control the behavior of solvents confined in nanometric channels. Here, water and ion transport in carbon nanotubes is investigated using classical force field molecular dynamics simulations. By combining one single walled carbon nanotube (uniformly charged or not) with two perforated graphene sheets, we mimic single nanopore devices similar to experimental ones. The graphitic edges delimit two reservoirs of water and ions in the simulation cell from which a voltage is imposed through the application of an external electric field. By analyzing the evolution of the electrolyte conductivity, the role of the carbon nanotube geometric parameters (radius and chirality) and of the functionalization of the carbon nanotube entrances with OH or COO⁻ groups is investigated for different concentrations of group functions. Full article

(This article belongs to the Special Issue State-of-the-Art Carbon Related and Low-Dimensional Functional Nanomaterials)

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11 pages, 4532 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Cost-Effective Preparation of Hydrophobic and Thermal-Insulating Silica Aerogels

by Jiaqi Shan, Yunpeng Shan, Chang Zou, Ye Hong, Jia Liu and Xingzhong Guo

Nanomaterials 2024, 14(1), 119; https://doi.org/10.3390/nano14010119 - 03 Jan 2024

Cited by 1 | Viewed by 1215

Abstract

The aim of this study is to reduce the manufacturing cost of a hydrophobic and heat-insulating silica aerogel and promote its industrial application in the field of thermal insulation. Silica aerogels with hydrophobicity and thermal-insulation capabilities were synthesized by using water-glass as the [...] Read more.

The aim of this study is to reduce the manufacturing cost of a hydrophobic and heat-insulating silica aerogel and promote its industrial application in the field of thermal insulation. Silica aerogels with hydrophobicity and thermal-insulation capabilities were synthesized by using water-glass as the silicon source and supercritical drying. The effectiveness of acid and alkali catalysis is compared in the formation of the sol. The introduction of sodium methyl silicate for the copolymerization enhances the hydrophobicity of the aerogel. The resultant silica aerogel has high hydrophobicity and a mesoporous structure with a pore volume exceeding 4.0 cm³·g⁻¹ and a specific surface area exceeding 950 m²·g⁻¹. The obtained silica aerogel/fiber-glass-mat composite has high thermal insulation, with a thermal conductivity of less than 0.020 W·m⁻¹·K⁻¹. The cost-effective process is promising for applications in the industrial preparation of silica aerogel thermal-insulating material. Full article

(This article belongs to the Special Issue Nanomaterials in Aerogel Composites)

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16 pages, 5150 KiB

Open AccessEditor’s ChoiceArticle

Modified 3D Graphene for Sensing and Electrochemical Capacitor Applications

by Kavitha Mulackampilly Joseph, Gabrielle R. Dangel and Vesselin Shanov

Nanomaterials 2024, 14(1), 108; https://doi.org/10.3390/nano14010108 - 02 Jan 2024

Viewed by 817

Abstract

Less defective, nitrogen-doped 3-dimensional graphene (N3DG) and defect-rich, nitrogen-doped 3-dimensional graphene (N3DG-D) were made by the thermal CVD (Chemical Vapor Deposition) process via varying the carbon precursors and synthesis temperature. These modified 3D graphene materials were compared with pristine 3-dimensional graphene (P3DG), which [...] Read more.

Less defective, nitrogen-doped 3-dimensional graphene (N3DG) and defect-rich, nitrogen-doped 3-dimensional graphene (N3DG-D) were made by the thermal CVD (Chemical Vapor Deposition) process via varying the carbon precursors and synthesis temperature. These modified 3D graphene materials were compared with pristine 3-dimensional graphene (P3DG), which has fewer defects and no nitrogen in its structure. The different types of graphene obtained were characterized for morphological, structural, and compositional assessment through Scanning Electron Microscopy (SEM), Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) techniques. Electrodes were fabricated, and electrochemical characterizations were conducted to evaluate the suitability of the three types of graphene for heavy metal sensing (lead) and Electric Double-Layer Capacitor (EDLC) applications. Initially, the various electrodes were treated with a mixture of 2.5 mM Ruhex (Ru (NH₃)₆Cl₃ and 25 mM KCl to confirm that all the electrodes underwent a reversible and diffusion-controlled electrochemical process. Defect-rich graphene (N3DG-D) revealed the highest current density, followed by pristine (P3DG) and less-defect graphene (N3DG). Further, the three types of graphene were subjected to a sensing test by square wave anodic stripping voltammetry (SWASV) for lead detection. The obtained preliminary results showed that the N3DG material provided a great lead-sensing capability, detecting as little as 1 µM of lead in a water solution. The suitability of the electrodes to be employed in an Electric Double-Layer Capacitor (EDLC) was also comparatively assessed. Electrochemical characterization using 1 M sodium sulfate electrolyte was conducted through cyclic voltammetry and galvanostatic charge-discharge studies. The voltammogram and the galvanostatic charge-discharge (GCD) curves of the three types of graphene confirmed their suitability to be used as EDLC. The N3DG electrode proved superior with a gravimetric capacitance of 6.1 mF/g, followed by P3DG and N3DG, exhibiting 1.74 mF/g and 0.32 mF/g, respectively, at a current density of 2 A/g. Full article

(This article belongs to the Special Issue Nanomaterials for Energy Conversion and Storage)

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15 pages, 4426 KiB

Open AccessEditor’s ChoiceArticle

Chiroptically Active Multi-Modal Calcium Carbonate-Based Nanocomposites

by Fearghal C. Donnelly, Finn Purcell-Milton, Eoin Caffrey, Lorenzo Branzi, Shelley Stafford, Faisal Ali Alhammad, Olan Cleary, Munirah Ghariani, Vera Kuznetsova and Yurii K. Gun’ko

Nanomaterials 2024, 14(1), 100; https://doi.org/10.3390/nano14010100 - 31 Dec 2023

Viewed by 776

Abstract

The development of multimodal nano- and micro-structures has become an increasingly popular area of research in recent years. In particular, the combination of two or more desirable properties within a single structure opens multiple opportunities from biomedicine, sensing, and catalysis, to a variety [...] Read more.

The development of multimodal nano- and micro-structures has become an increasingly popular area of research in recent years. In particular, the combination of two or more desirable properties within a single structure opens multiple opportunities from biomedicine, sensing, and catalysis, to a variety of optical applications. Here, for the first time, we report the synthesis and characterization of multimodal chiroptically active CaCO₃ nanocomposites. These composites have been prepared by a modified microemulsion method in the presence of an amino acid (cysteine). Following this, additional modalities have been introduced by loading the composites with luminescent nanoparticles or doping with Eu³⁺ ions. The luminescent composites have been produced by the incorporation of CuInZnS/ZnS or CdSe@ZnS/ZnS core/shell quantum dots, or via doping with trivalent europium. In this manner, we have produced chiroptically active composites with orange, green, and red luminescence. Overall, this work demonstrates the unique advantage and potential of our approach and new class of chiroptically active CaCO₃ nanocomposites, which display tunable functionality to specific requirements via the incorporation of desired ions, nanoparticles, and chirality of the structure. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface-Related Properties (Volume II))

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15 pages, 4313 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Effect of the Synthetic Method and Surface Chemistry on the Properties of CsPbBr₃ Nanoparticles

by Mariangela Giancaspro, Annamaria Panniello, Nicoletta Depalo, Roberto Comparelli, Marinella Striccoli, Maria Lucia Curri and Elisabetta Fanizza

Nanomaterials 2024, 14(1), 81; https://doi.org/10.3390/nano14010081 - 27 Dec 2023

Viewed by 699

Abstract

Over the last decade, the attractive properties of CsPbBr₃ nanoparticles (NPs) have driven ever-increasing progress in the development of synthetic procedures to obtain high-quality NPs at high concentrations. Understanding how the properties of NPs are influenced by the composition of the reaction [...] Read more.

Over the last decade, the attractive properties of CsPbBr₃ nanoparticles (NPs) have driven ever-increasing progress in the development of synthetic procedures to obtain high-quality NPs at high concentrations. Understanding how the properties of NPs are influenced by the composition of the reaction mixture in combination with the specific synthetic methodology is crucial, both for further elucidating the fundamental characteristics of this class of materials and for their manufacturing towards technological applications. This work aims to shed light on this aspect by synthesizing CsPbBr₃ NPs by means of two well-assessed synthetic procedures, namely, hot injection (HI) and ligand-assisted reprecipitation (LARP) in non-polar solvents, using PbBr₂ and Cs₂CO₃ as precursors in the presence of already widely investigated ligands. The overall goal is to study and compare the properties of the NPs to understand how each synthetic method influences the NPs’ size and/or the optical properties. Reaction composition and conditions are purposely tuned towards the production of nanocubes with narrow size distribution, high emission properties, and the highest achievable concentration. As a result, the formation of bulk crystals as precipitate in LARP limits the achievement of a highly concentrated NP solution. The size of the NPs obtained by LARP seems to be poorly affected by the ligands’ nature and the excess bromide, as consequence of bromide-rich solvation agents, effectively results in NPs with excellent emission properties. In contrast, NPs synthesized by HI exhibit high reaction yield, diffusion growth-controlled size, and less striking emission properties, probably ascribed to a bromide-deficient condition. Full article

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

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16 pages, 3124 KiB

Open AccessEditor’s ChoiceArticle

Improved Thermophysical and Mechanical Properties in LiNaSO₄ Composites for Thermal Energy Storage

by Maria Taeño, Ariba Adnan, Cristina Luengo, Ángel Serrano, Jean-Luc Dauvergne, Paola Crocomo, Ali Huerta, Stefania Doppiu and Elena Palomo del Barrio

Nanomaterials 2024, 14(1), 78; https://doi.org/10.3390/nano14010078 - 27 Dec 2023

Viewed by 754

Abstract

Solid-solid phase-change materials have great potential for developing compact and low-cost thermal storage systems. The solid-state nature of these materials enables the design of systems analogous to those based on natural rocks but with an extraordinarily higher energy density. In this scenario, the [...] Read more.

Solid-solid phase-change materials have great potential for developing compact and low-cost thermal storage systems. The solid-state nature of these materials enables the design of systems analogous to those based on natural rocks but with an extraordinarily higher energy density. In this scenario, the evaluation and improvement of the mechanical and thermophysical properties of these solid-solid PCMs are key to exploiting their full potential. In this study, LiNaSO₄-based composites, comprising porous MgO and expanded graphite (EG) as the dispersed phases and LiNaSO₄ as the matrix, have been prepared with the aim of enhancing the thermophysical and mechanical properties of LiNaSO₄. The characteristic structure of MgO and the high degree of crystallinity of the EG600 confer on the LiNaSO₄ sample mechanical stability, which leads to an increase in the Young’s modulus (almost three times higher) compared to the pure LiNaSO₄ sample. These materials are proposed as a suitable candidate for thermal energy storage applications at high temperatures (400–550 °C). The addition of 5 wt.% of MgO or 5% of EG had a minor influence on the solid-solid phase change temperature and enthalpy; however, other thermal properties such as thermal conductivity or specific heat capacity were increased, extending the scope of PCMs use. Full article

(This article belongs to the Special Issue Nanomaterials for Energy Conversion and Storage II)

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13 pages, 3870 KiB

Open AccessEditor’s ChoiceArticle

Bayesian Optimization of Wet-Impregnated Co-Mo/Al₂O₃ Catalyst for Maximizing the Yield of Carbon Nanotube Synthesis

by Sangsoo Shin, Hyeongyun Song, Yeon Su Shin, Jaegeun Lee and Tae Hoon Seo

Nanomaterials 2024, 14(1), 75; https://doi.org/10.3390/nano14010075 - 26 Dec 2023

Cited by 1 | Viewed by 1052

Abstract

Multimetallic catalysts have demonstrated their high potential for the controlled synthesis of carbon nanotubes (CNTs), but their development requires a more complicated optimization than that of monometallic catalysts. Here, we employed Bayesian optimization (BO) to optimize the preparation of Co-Mo/Al₂O₃ [...] Read more.

Multimetallic catalysts have demonstrated their high potential for the controlled synthesis of carbon nanotubes (CNTs), but their development requires a more complicated optimization than that of monometallic catalysts. Here, we employed Bayesian optimization (BO) to optimize the preparation of Co-Mo/Al₂O₃ catalyst using wet impregnation, with the goal of maximizing carbon yield in the chemical vapor deposition (CVD) synthesis of CNTs. In the catalyst preparation process, we selected four parameters to optimize: the weight percentage of metal, the ratio of Co to Mo in the catalyst, the drying temperature, and the calcination temperature. We ran two parallel BO processes to compare the performance of two types of acquisitions: expected improvement (EI), which does not consider noise, and one-shot knowledge gradient (OKG), which takes noise into account. As a result, both acquisition functions successfully optimized the carbon yield with similar performance. The result suggests that the use of EI, which has a lower computational load, is acceptable if the system has sufficient robustness. The investigation of the contour plots showed that the addition of Mo has a negative effect on carbon yield. Full article

(This article belongs to the Section 2D and Carbon Nanomaterials)

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10 pages, 1979 KiB

Open AccessEditor’s ChoiceArticle

Observation of Multi-Phonon Emission in Monolayer WS₂ on Various Substrates

by Eli R. Adler, Thy Doan Mai Le, Ibrahim Boulares, Robert Boyd, Yangchen He, Daniel Rhodes, Edward Van Keuren, Paola Barbara and Sina Najmaei

Nanomaterials 2024, 14(1), 37; https://doi.org/10.3390/nano14010037 - 22 Dec 2023

Viewed by 1072

Abstract

Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin–orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, [...] Read more.

Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin–orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, it is known that the excitons formed from electrons in the lower-energy conduction bands are dark in nature, whereas low-energy emissions in the photoluminescence spectrum have been linked to the brightening of these transitions, either via defect scattering or via phonon scattering with first-order phonon replicas. Through temperature and incident-power-dependent studies of WS₂ grown by CVD or exfoliated from high-purity bulk crystal on different substrates, we demonstrate that the strong exciton–phonon coupling yields brightening of dark transitions up to sixth-order phonon replicas. We discuss the critical role of defects in the brightening pathways of dark excitons and their phonon replicas, and we elucidate that these emissions are intrinsic to the material and independent of substrate, encapsulation, growth method, and transfer approach. Full article

(This article belongs to the Special Issue Two-Dimensional Materials for (Opto)-Electronic Applications)

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17 pages, 5960 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Lead-Free Perovskite Thin Films for Gas Sensing through Surface Acoustic Wave Device Detection

by Nicoleta Enea, Valentin Ion, Cristian Viespe, Izabela Constantinoiu, Anca Bonciu, Maria Luiza Stîngescu, Ruxandra Bîrjega and Nicu Doinel Scarisoreanu

Nanomaterials 2024, 14(1), 39; https://doi.org/10.3390/nano14010039 - 22 Dec 2023

Viewed by 1056

Abstract

Thin film technology shows great promise in fabricating electronic devices such as gas sensors. Here, we report the fabrication of surface acoustic wave (SAW) sensors based on thin films of (1 − x) Ba(Ti_0.8Zr_0.2)O_3−x(Ba_0.7Ca_0.3 [...] Read more.

Thin film technology shows great promise in fabricating electronic devices such as gas sensors. Here, we report the fabrication of surface acoustic wave (SAW) sensors based on thin films of (1 − x) Ba(Ti_0.8Zr_0.2)O_3−x(Ba_0.7Ca_0.3)TiO₃ (BCTZ50, x = 50) and Polyethylenimine (PEI). The layers were deposited by two laser-based techniques, namely pulsed laser deposition (PLD) for the lead-free material and matrix assisted pulsed laser evaporation (MAPLE) for the sensitive polymer. In order to assay the impact of the thickness, the number of laser pulses was varied, leading to thicknesses between 50 and 350 nm. The influence of BCTZ film’s crystallographic features on the characteristics and performance of the SAW device was studied by employing substrates with different crystal structures, more precisely cubic Strontium Titanate (SrTiO₃) and orthorhombic Gadolinium Scandium Oxide (GdScO₃). The SAW sensors were further integrated into a testing system to evaluate the response of the BCTZ thin films with PEI, and then subjected to tests for N₂, CO₂ and O₂ gases. The influence of the MAPLE’s deposited PEI layer on the overall performance was demonstrated. For the SAW sensors based on BCTZ/GdScO₃ thin films with a PEI polymer, a maximum frequency shift of 39.5 kHz has been obtained for CO₂; eight times higher compared to the sensor without the polymeric layer. Full article

(This article belongs to the Special Issue New Challenges in Designed Nanointerfaces)

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15 pages, 12522 KiB

Open AccessEditor’s ChoiceArticle

Silicon–Nanodiamond-Based Anode for a Lithium-Ion Battery

by Cheng-Ying Jhan, Shi-Hong Sung and Yonhua Tzeng

Nanomaterials 2024, 14(1), 43; https://doi.org/10.3390/nano14010043 - 22 Dec 2023

Viewed by 895

Abstract

Maintaining the physical integrity of a silicon-based anode, which suffers from damage caused by severe volume changes during cycling, is a top priority in its practical applications. The performance of silicon-flake-based anodes has been significantly improved by mixing nanodiamond powders with silicon flakes [...] Read more.

Maintaining the physical integrity of a silicon-based anode, which suffers from damage caused by severe volume changes during cycling, is a top priority in its practical applications. The performance of silicon-flake-based anodes has been significantly improved by mixing nanodiamond powders with silicon flakes for the fabrication of anodes for lithium-ion batteries (LIBs). Nanodiamonds adhere to the surfaces of silicon flakes and are distributed in the binder between flakes. A consistent and robust solid electrolyte interphase (SEI) is promoted by the aid of abundant reactive surface-linked functional groups and exposed dangling bonds of nanodiamonds, leading to enhanced physical integrity of the silicon flakes and the anode. The battery’s high-rate discharge capabilities and cycle life are thus improved. SEM, Raman spectroscopy, and XRD were applied to examine the structure and morphology of the anode. Electrochemical performance was evaluated to demonstrate a capacity retention of nearly 75% after 200 cycles, with the final specific capacity exceeding 1000 mAh/g at a test current of 4 mA/cm². This is attributed to the improved stability of the solid electrolyte interphase (SEI) structure that was achieved by integrating nanodiamonds with silicon flakes in the anode, leading to enhanced cycling stability and rapid charge-discharge performance. The results from this study present an effective strategy of achieving high-cycling-performance by adding nanodiamonds to silicon-flake-based anodes. Full article

(This article belongs to the Topic Advanced Nanomaterials for Lithium-Ion Batteries)

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22 pages, 12744 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Resonance-Based Sensing of Magnetic Nanoparticles Using Microfluidic Devices with Ferromagnetic Antidot Nanostructures

by Reyne Dowling, Ryszard Narkowicz, Kilian Lenz, Antje Oelschlägel, Jürgen Lindner and Mikhail Kostylev

Nanomaterials 2024, 14(1), 19; https://doi.org/10.3390/nano14010019 - 20 Dec 2023

Viewed by 805

Abstract

We demonstrated resonance-based detection of magnetic nanoparticles employing novel designs based upon planar (on-chip) microresonators that may serve as alternatives to conventional magnetoresistive magnetic nanoparticle detectors. We detected 130 nm sized magnetic nanoparticle clusters immobilized on sensor surfaces after flowing through PDMS microfluidic [...] Read more.

We demonstrated resonance-based detection of magnetic nanoparticles employing novel designs based upon planar (on-chip) microresonators that may serve as alternatives to conventional magnetoresistive magnetic nanoparticle detectors. We detected 130 nm sized magnetic nanoparticle clusters immobilized on sensor surfaces after flowing through PDMS microfluidic channels molded using a 3D printed mold. Two detection schemes were investigated: (i) indirect detection incorporating ferromagnetic antidot nanostructures within microresonators, and (ii) direct detection of nanoparticles without an antidot lattice. Using scheme (i), magnetic nanoparticles noticeably downshifted the resonance fields of an antidot nanostructure by up to 207 G. In a similar antidot device in which nanoparticles were introduced via droplets rather than a microfluidic channel, the largest shift was only 44 G with a sensitivity of 7.57 G/ng. This indicated that introduction of the nanoparticles via microfluidics results in stronger responses from the ferromagnetic resonances. The results for both devices demonstrated that ferromagnetic antidot nanostructures incorporated within planar microresonators can detect nanoparticles captured from dispersions. Using detection scheme (ii), without the antidot array, we observed a strong resonance within the nanoparticles. The resonance’s strength suggests that direct detection is more sensitive to magnetic nanoparticles than indirect detection using a nanostructure, in addition to being much simpler. Full article

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

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21 pages, 5259 KiB

Open AccessEditor’s ChoiceArticle

Nanostructural Characterization of Luminescent Polyvinyl Alcohol/Graphene Quantum Dots Nanocomposite Films

by Dhanumalayan Elumalai, Beatriz Rodríguez, Ganna Kovtun, Pedro Hidalgo, Bianchi Méndez, Shaik Kaleemulla, Girish M. Joshi and M. Teresa Cuberes

Nanomaterials 2024, 14(1), 5; https://doi.org/10.3390/nano14010005 - 19 Dec 2023

Cited by 1 | Viewed by 1297

Abstract

This study focuses on the fabrication of polymer nanocomposite films using polyvinyl alcohol (PVA)/graphene quantum dots (GQDs). We investigate the relationship between the structural, thermal, and nanoscale morphological properties of these films and their photoluminescent response. Although according to X-ray diffraction (XRD), Fourier-transform [...] Read more.

This study focuses on the fabrication of polymer nanocomposite films using polyvinyl alcohol (PVA)/graphene quantum dots (GQDs). We investigate the relationship between the structural, thermal, and nanoscale morphological properties of these films and their photoluminescent response. Although according to X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and differential thermal analysis (DTA), the incorporation of GQDs does not significantly affect the percentage crystallinity of the PVA matrix, for a range of added GQD concentrations, atomic force microscopy (AFM) showed the formation of islands with apparent crystalline morphology on the surface of the PVA/GQD films. This observation suggests that GQDs presumably act as nucleating agents for island growth. The incorporation of GQDs also led to the formation of characteristic surface pores with increased stiffness and frictional contrast, as indicated by ultrasonic force microscopy (UFM) and frictional force microscopy (FFM) data. The photoluminescence (PL) spectra of the films were found to depend both on the amount of GQDs incorporated and on the film morphology. For GQD loads >1.2%wt, a GQD-related band was observed at ~1650 cm⁻¹ in FT-IR, along with an increase in the PL band at lower energy. For a load of ~2%wt GQDs, the surface morphology was characterized by extended cluster aggregates with lower stiffness and friction than the surrounding matrix, and the PL signal decreased. Full article

(This article belongs to the Special Issue Advances in Polymer Nanocomposite Films)

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14 pages, 2407 KiB

Open AccessEditor’s ChoiceArticle

Layered Double Hydroxides as an Intercalation System for Hydrophobic Molecules

by Lei Li, Anastasia Sevciuc and Patrick van Rijn

Nanomaterials 2023, 13(24), 3145; https://doi.org/10.3390/nano13243145 - 15 Dec 2023

Viewed by 794

Abstract

Layered double hydroxides (LDHs) have been extensively studied as drug delivery systems due to their favorable characteristics, including biocompatibility, high loading efficiency, and pH-responsive release. However, the current research predominantly focuses on LDHs as carriers for various anionic drugs, while there are only [...] Read more.

Layered double hydroxides (LDHs) have been extensively studied as drug delivery systems due to their favorable characteristics, including biocompatibility, high loading efficiency, and pH-responsive release. However, the current research predominantly focuses on LDHs as carriers for various anionic drugs, while there are only limited reports on LDHs as carriers for hydrophobic drugs. In this study, we successfully achieved the loading of a hydrophobic drug mimic, Nile red (NR), into LDHs using sodium dodecyl sulfate (SDS) as an intermediate storage medium. Furthermore, we optimized the experimental methods and varied the SDS/NR molar ratio to optimize this intercalation system. With an increase in the SDS/NR molar ratio from 2/1 to 32/1, the loading efficiency of LDH-SDS-NR for NR initially increased from 1.32% for LDH-SDS-NR_2/1 to 4.46% for LDH-SDS-NR_8/1. Then, the loading efficiency slightly decreased to 3.64% for LDH-SDS-NR_16.8/1, but then increased again to 6.31% for LDH-SDS-NR_32/1. We believe that the established method and the obtained results in this study broaden the application scope of LDHs as delivery systems for hydrophobic drugs and contribute to the further expansion of the application scope of LDHs. Full article

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