Nanomaterials

19 pages, 5029 KiB

Open AccessEditor’s ChoiceArticle

Bromine Ion-Intercalated Layered Bi₂WO₆ as an Efficient Catalyst for Advanced Oxidation Processes in Tetracycline Pollutant Degradation Reaction

by Rama Krishna Chava and Misook Kang

Nanomaterials 2023, 13(18), 2614; https://doi.org/10.3390/nano13182614 - 21 Sep 2023

Viewed by 1086

Abstract

The visible-light-driven photocatalytic degradation of pharmaceutical pollutants in aquatic environments is a promising strategy for addressing water pollution problems. This work highlights the use of bromine-ion-doped layered Aurivillius oxide, Bi₂WO₆, to synergistically optimize the morphology and increase the formation [...] Read more.

The visible-light-driven photocatalytic degradation of pharmaceutical pollutants in aquatic environments is a promising strategy for addressing water pollution problems. This work highlights the use of bromine-ion-doped layered Aurivillius oxide, Bi₂WO₆, to synergistically optimize the morphology and increase the formation of active sites on the photocatalyst’s surface. The layered Bi₂WO₆ nanoplates were synthesized by a facile hydrothermal reaction in which bromine (Br⁻) ions were introduced by adding cetyltrimethylammonium bromide (CTAB)/tetrabutylammonium bromide (TBAB)/potassium bromide (KBr). The as-synthesized Bi₂WO₆ nanoplates displayed higher photocatalytic tetracycline degradation activity (~83.5%) than the Bi₂WO₆ microspheres (~48.2%), which were obtained without the addition of Br precursors in the reaction medium. The presence of Br⁻ was verified experimentally, and the newly formed Bi₂WO₆ developed as nanoplates where the adsorbed Br⁻ ions restricted the multilayer stacking. Considering the significant morphology change, increased specific surface area, and enhanced photocatalytic performance, using a synthesis approach mediated by Br⁻ ions to design layered photocatalysts is expected to be a promising system for advancing water remediation. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalytic Degradation of Pollutant and Hydrogen Evolution)

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23 pages, 3432 KiB

Open AccessReview

Recent Tendency on Transition-Metal Phosphide Electrocatalysts for the Hydrogen Evolution Reaction in Alkaline Media

by Seo Jeong Yoon, Se Jung Lee, Min Hui Kim, Hui Ae Park, Hyo Seon Kang, Seo-Yoon Bae and In-Yup Jeon

Nanomaterials 2023, 13(18), 2613; https://doi.org/10.3390/nano13182613 - 21 Sep 2023

Cited by 3 | Viewed by 1436

Abstract

Hydrogen energy is regarded as an auspicious future substitute to replace fossil fuels, due to its environmentally friendly characteristics and high energy density. In the pursuit of clean hydrogen production, there has been a significant focus on the advancement of effective electrocatalysts for [...] Read more.

Hydrogen energy is regarded as an auspicious future substitute to replace fossil fuels, due to its environmentally friendly characteristics and high energy density. In the pursuit of clean hydrogen production, there has been a significant focus on the advancement of effective electrocatalysts for the process of water splitting. Although noble metals like Pt, Ru, Pd and Ir are superb electrocatalysts for the hydrogen evolution reaction (HER), they have limitations for large-scale applications, mainly high cost and low abundance. As a result, non-precious transition metals have emerged as promising candidates to replace their more expensive counterparts in various applications. This review focuses on recently developed transition metal phosphides (TMPs) electrocatalysts for the HER in alkaline media due to the cooperative effect between the phosphorus and transition metals. Finally, we discuss the challenges of TMPs for HER. Full article

(This article belongs to the Special Issue Transition Metal-Based Nanostructures for Energy Storage and Conversion)

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25 pages, 4843 KiB

Open AccessReview

(Fe-Co-Ni-Zn)-Based Metal–Organic Framework-Derived Electrocatalyst for Zinc–Air Batteries

by Anup Adhikari, Kisan Chhetri, Rajan Rai, Debendra Acharya, Jyotendra Kunwar, Roshan Mangal Bhattarai, Rupesh Kumar Jha, Dasharath Kandel, Hak Yong Kim and Mani Ram Kandel

Nanomaterials 2023, 13(18), 2612; https://doi.org/10.3390/nano13182612 - 21 Sep 2023

Cited by 12 | Viewed by 2308

Abstract

Zinc–air batteries (ZABs) have garnered significant interest as a viable substitute for lithium-ion batteries (LIBs), primarily due to their impressive energy density and low cost. However, the efficacy of zinc–air batteries is heavily dependent on electrocatalysts, which play a vital role in enhancing [...] Read more.

Zinc–air batteries (ZABs) have garnered significant interest as a viable substitute for lithium-ion batteries (LIBs), primarily due to their impressive energy density and low cost. However, the efficacy of zinc–air batteries is heavily dependent on electrocatalysts, which play a vital role in enhancing reaction efficiency and stability. This scholarly review article highlights the crucial significance of electrocatalysts in zinc–air batteries and explores the rationale behind employing Fe-Co-Ni-Zn-based metal–organic framework (MOF)-derived hybrid materials as potential electrocatalysts. These MOF-derived electrocatalysts offer advantages such as abundancy, high catalytic activity, tunability, and structural stability. Various synthesis methods and characterization techniques are employed to optimize the properties of MOF-derived electrocatalysts. Such electrocatalysts exhibit excellent catalytic activity, stability, and selectivity, making them suitable for applications in ZABs. Furthermore, they demonstrate notable capabilities in the realm of ZABs, encompassing elevated energy density, efficacy, and prolonged longevity. It is imperative to continue extensively researching and developing this area to propel the advancement of ZAB technology forward and pave the way for its practical implementation across diverse fields. Full article

(This article belongs to the Topic Metal Organic Frameworks and Derived Materials for Advanced Applications)

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12 pages, 4410 KiB

Open AccessArticle

The Fast and One-Step Growth of ZnO Nanorods on Cellulose Nanofibers for Highly Sensitive Photosensors

by Naveed ul Hassan Alvi, Mohammad Yusuf Mulla, Tiffany Abitbol, Andreas Fall and Valerio Beni

Nanomaterials 2023, 13(18), 2611; https://doi.org/10.3390/nano13182611 - 21 Sep 2023

Cited by 1 | Viewed by 1295

Abstract

Cellulose is the most abundant organic material on our planet which has a key role in our daily life (e.g., paper, packaging). In recent years, the need for replacing fossil-based materials has expanded the application of cellulose and cellulose derivatives including into electronics [...] Read more.

Cellulose is the most abundant organic material on our planet which has a key role in our daily life (e.g., paper, packaging). In recent years, the need for replacing fossil-based materials has expanded the application of cellulose and cellulose derivatives including into electronics and sensing. The combination of nanostructures with cellulose nanofibers (CNFs) is expected to create new opportunities for the development of innovative electronic devices. In this paper, we report on a single-step process for the low temperature (<100 °C), environmentally friendly, and fully scalable CNF-templated highly dense growth of zinc oxide (ZnO) nanorods (NRs). More specifically, the effect of the degree of substitution of the CNF (enzymatic CNFs and carboxymethylated CNFs with two different substitution levels) on the ZnO growth and the application of the developed ZnO NRs/CNF nanocomposites in the development of UV sensors is reported herein. The results of this investigation show that the growth and nature of ZnO NRs are strongly dependent on the charge of the CNFs; high charge promotes nanorod growth whereas with low charge, ZnO isotropic microstructures are created that are not attached to the CNFs. Devices manufactured via screen printing/drop-casting of the ZnO NRs/CNF nanocomposites demonstrate a good photo-sensing response with a very stable UV-induced photocurrent of 25.84 µA. This also exhibits excellent long-term stability with fast ON/OFF switching performance under the irradiance of a UV lamp (15 W). Full article

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12 pages, 2698 KiB

Open AccessArticle

Exploring Pt-Pd Alloy Nanoparticle Cluster Formation through Conventional Sizing Techniques and Single-Particle Inductively Coupled Plasma—Sector Field Mass Spectrometry

by Omar Martinez-Mora, Kristof Tirez, Filip Beutels, Wilfried Brusten, Luis F. Leon-Fernandez, Jan Fransaer, Xochitl Dominguez-Benetton and Milica Velimirovic

Nanomaterials 2023, 13(18), 2610; https://doi.org/10.3390/nano13182610 - 21 Sep 2023

Cited by 3 | Viewed by 989

Abstract

Accurate characterization of Pt-Pd alloy nanoparticle clusters (NCs) is crucial for understanding their synthesis using Gas-Diffusion Electrocrystallization (GDEx). In this study, we propose a comprehensive approach that integrates conventional sizing techniques—scanning electron microscopy (SEM) and dynamic light scattering (DLS)—with innovative single-particle inductively coupled [...] Read more.

Accurate characterization of Pt-Pd alloy nanoparticle clusters (NCs) is crucial for understanding their synthesis using Gas-Diffusion Electrocrystallization (GDEx). In this study, we propose a comprehensive approach that integrates conventional sizing techniques—scanning electron microscopy (SEM) and dynamic light scattering (DLS)—with innovative single-particle inductively coupled plasma—sector field mass spectrometry (spICP-SFMS) to investigate Pt-Pd alloy NC formation. SEM and DLS provide insights into morphology and hydrodynamic sizes, while spICP-SFMS elucidates the particle size and distribution of Pt-Pd alloy NCs, offering rapid and orthogonal characterization. The spICP-SFMS approach presented enables detailed characterization of Pt-Pd alloy NCs, which was previously challenging due to the absence of multi-element capabilities in conventional spICP-MS systems. This innovative approach not only enhances our understanding of bimetallic nanoparticle synthesis, but also paves the way for tailoring these materials for specific applications, marking a significant advancement in the field of nanomaterial science. Full article

(This article belongs to the Special Issue ICP-MS-Based Characterization and Quantification of Nano- and Microstructures)

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11 pages, 4339 KiB

Open AccessArticle

Graphitic Carbon Nitride Nanosheets Decorated with Zinc-Cadmium Sulfide for Type-II Heterojunctions for Photocatalytic Hydrogen Production

by Ammar Bin Yousaf, Muhammad Imran, Muhammad Farooq, Samaira Kausar, Samina Yasmeen and Peter Kasak

Nanomaterials 2023, 13(18), 2609; https://doi.org/10.3390/nano13182609 - 21 Sep 2023

Cited by 1 | Viewed by 944

Abstract

In this study, we fabricated graphitic carbon nitride (g-C₃N₄) nanosheets with embedded ZnCdS nanoparticles to form a type II heterojunction using a facile synthesis approach, and we used them for photocatalytic H₂ production. The morphologies, chemical [...] Read more.

In this study, we fabricated graphitic carbon nitride (g-C₃N₄) nanosheets with embedded ZnCdS nanoparticles to form a type II heterojunction using a facile synthesis approach, and we used them for photocatalytic H₂ production. The morphologies, chemical structure, and optical properties of the obtained g-C₃N₄–ZnCdS samples were characterized by a battery of techniques, such as TEM, XRD, XPS, and UV-Vis DRS. The as-synthesized g-C₃N₄–ZnCdS photocatalyst exhibited the highest hydrogen production rate of 108.9 μmol·g⁻¹·h⁻¹ compared to the individual components (g-C₃N₄: 13.5 μmol·g⁻¹·h⁻¹, ZnCdS: 45.3 μmol·g⁻¹·h⁻¹). The improvement of its photocatalytic activity can mainly be attributed to the heterojunction formation and resulting synergistic effect, which provided more channels for charge carrier migration and reduced the recombination of photogenerated electrons and holes. Meanwhile, the g-C₃N₄–ZnCdS heterojunction catalyst also showed a higher stability over a number of repeated cycles. Our work provides insight into using g-C₃N₄ and metal sulfide in combination so as to develop low-cost, efficient, visible-light-active hydrogen production photocatalysts. Full article

(This article belongs to the Special Issue Degradation and Photocatalytic Properties of Nanocomposites)

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18 pages, 5439 KiB

Open AccessArticle

Asymmetric and Flexible Ag-MXene/ANFs Composite Papers for Electromagnetic Shielding and Thermal Management

by Xiaoai Ye, Xu Zhang, Xinsheng Zhou and Guigen Wang

Nanomaterials 2023, 13(18), 2608; https://doi.org/10.3390/nano13182608 - 21 Sep 2023

Viewed by 1061

Abstract

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management capability are ideal for portable and flexible electronic devices. Herein, the asymmetric and multilayered structure Ag-MXene/ANFs composite papers (AMAGM) were fabricated based on Ag-MXene hybrids [...] Read more.

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management capability are ideal for portable and flexible electronic devices. Herein, the asymmetric and multilayered structure Ag-MXene/ANFs composite papers (AMAGM) were fabricated based on Ag-MXene hybrids and aramid nanofibers (ANFs) via a self-reduction and alternating vacuum-assisted filtration process. The resultant AMAGM composite papers exhibit high electrical conductivity of 248,120 S m⁻¹, excellent mechanical properties with tensile strength of 124.21 MPa and fracture strain of 4.98%, superior EMI shielding effectiveness (62 dB), ultra-high EMI SE/t (11,923 dB cm² g⁻¹) and outstanding EMI SE reliability as high as 96.1% even after 5000 cycles of bending deformation benefiting from the unique structure and the 3D network at a thickness of 34 μm. Asymmetric structures play an important role in regulating reflection and absorption of electromagnetic waves. In addition, the multifunctional nanocomposite papers reveal outstanding thermal management performances such as ultrafast thermal response, high heating temperatures at low operation voltage, and high heating stability. The results indicate that the AMAGM composite papers have excellent potential for high-integration electromagnetic shielding, wearable electronics, artificial intelligence, and high-performance heating devices. Full article

(This article belongs to the Special Issue Recent Advances in Two-Dimensional Monolayer Nanomaterials)

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9 pages, 1836 KiB

Open AccessArticle

Black Phosphorus Field-Effect Transistors with Improved Contact via Localized Joule Heating

by Fangyuan Shi, Shengguang Gao, Qichao Li, Yanming Zhang, Teng Zhang, Zhiyan He, Kunchan Wang, Xiaowo Ye, Jichao Liu, Shenghao Jiang and Changxin Chen

Nanomaterials 2023, 13(18), 2607; https://doi.org/10.3390/nano13182607 - 21 Sep 2023

Viewed by 1241

Abstract

Two-dimensional (2D) black phosphorus (BP) is considered an ideal building block for field-effect transistors (FETs) owing to its unique structure and intriguing properties. To achieve high-performance BP-FETs, it is essential to establish a reliable and low-resistance contact between the BP and the electrodes. [...] Read more.

Two-dimensional (2D) black phosphorus (BP) is considered an ideal building block for field-effect transistors (FETs) owing to its unique structure and intriguing properties. To achieve high-performance BP-FETs, it is essential to establish a reliable and low-resistance contact between the BP and the electrodes. In this study, we employed a localized Joule heating method to improve the contact between the 2D BP and gold electrodes, resulting in enhanced BP-FET performance. Upon applying a sufficiently large source–drain voltage, the zero-bias conductance of the device increased by approximately five orders of magnitude, and the linearity of the current–voltage curves was also enhanced. This contact improvement can be attributed to the formation of gold phosphide at the interface of the BP and the gold electrodes owing to current-generated localized Joule heat. The fabricated BP-FET demonstrated a high on/off ratio of 4850 and an on-state conductance per unit channel width of 1.25 μS μm⁻¹, significantly surpassing those of the BP-FETs without electrical annealing. These findings offer a method to achieve a low-resistance BP/metal contact for developing high-performance BP-based electronic devices. Full article

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12 pages, 3321 KiB

Open AccessArticle

Development of Hydroxyapatite Coatings for Orthopaedic Implants from Colloidal Solutions: Part 2—Detailed Characterisation of the Coatings and Their Growth Mechanism

by Bríd Murphy, Mick A. Morris and Jhonattan Baez

Nanomaterials 2023, 13(18), 2606; https://doi.org/10.3390/nano13182606 - 21 Sep 2023

Viewed by 1022

Abstract

This study is the second part of a two-part study whereby supersaturated solutions of calcium and phosphate ions generate well-defined hydroxyapatite coatings for orthopaedic implants. An ‘ideal’ process solution is selected from Part 1, and the detailed characterisation of films produced from this [...] Read more.

This study is the second part of a two-part study whereby supersaturated solutions of calcium and phosphate ions generate well-defined hydroxyapatite coatings for orthopaedic implants. An ‘ideal’ process solution is selected from Part 1, and the detailed characterisation of films produced from this solution is undertaken here in Part 2. Analysis is presented on the hydroxyapatite produced, in both powder form and as a film upon titanium substrates representative of orthopaedic implants. From thermal analysis data, it is shown that there is bound and interstitial water present in the hydroxyapatite. Nuclear magnetic resonance data allow for the distinction between an amorphous and a crystalline component of the material. As hydroxyapatite coatings are generated, their growth mechanism is tracked across repeated process runs. A clear understanding of the growth mechanism is achieved though crystallinity and electron imaging data. Transmission electron imaging data support the proposed crystal growth and deposition mechanism. All of the data conclude that this process has a clear propensity to grow the hydroxyapatite phase of octacalcium phosphate. The investigation of the hydroxyapatite coating and its growth mechanism establish that a stable and reproducible process window has been identified. Precise control is achieved, leading to the successful formation of the desired hydroxyapatite films. Full article

(This article belongs to the Special Issue Functional Coatings with Nanostructures: Synthesis, Characterizations and Applications)

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14 pages, 9755 KiB

Open AccessArticle

Thermal Stability of Cu-Al-Ni Shape Memory Alloy Thin Films Obtained by Nanometer Multilayer Deposition

by Jose F. Gómez-Cortés, María L. Nó, Andrey Chuvilin, Isabel Ruiz-Larrea and Jose M. San Juan

Nanomaterials 2023, 13(18), 2605; https://doi.org/10.3390/nano13182605 - 21 Sep 2023

Viewed by 954

Abstract

Cu-Al-Ni is a high-temperature shape memory alloy (HTSMA) with exceptional thermomechanical properties, making it an ideal active material for engineering new technologies able to operate at temperatures up to 200 °C. Recent studies revealed that these alloys exhibit a robust superelastic behavior at [...] Read more.

Cu-Al-Ni is a high-temperature shape memory alloy (HTSMA) with exceptional thermomechanical properties, making it an ideal active material for engineering new technologies able to operate at temperatures up to 200 °C. Recent studies revealed that these alloys exhibit a robust superelastic behavior at the nanometer scale, making them excellent candidates for developing a new generation of micro-/nano-electromechanical systems (MEMS/NEMS). The very large-scale integration (VLSI) technologies used in microelectronics are based on thin films. In the present work, 1 μm thickness thin films of 84.1Cu-12.4 Al-3.5Ni (wt.%) were obtained by solid-state diffusion from a multilayer system deposited on SiNx (200 nm)/Si substrates by e-beam evaporation. With the aim of evaluating the thermal stability of such HTSMA thin films, heating experiments were performed in situ inside the transmission electron microscope to identify the temperature at which the material was decomposed by precipitation. Their microstructure, compositional analysis, and phase identification were characterized by scanning and transmission electron microscopy equipped with energy dispersive X-ray spectrometers. The nucleation and growth of two stable phases, Cu-Al-rich alpha phase and Ni-Al-rich intermetallic, were identified during in situ heating TEM experiments between 280 and 450 °C. These findings show that the used production method produces an HTSMA with high thermal stability and paves the road for developing high-temperature MEMS/NEMS using shape memory and superelastic technologies. Full article

(This article belongs to the Special Issue Nanostructural Processing Effects in Shape Memory Alloys)

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24 pages, 10396 KiB

Open AccessArticle

Exploring Nitrogen-Functionalized Graphene Composites for Urinary Catheter Applications

by Rita Teixeira-Santos, Luciana C. Gomes, Rita Vieira, Francisca Sousa-Cardoso, Olívia S. G. P. Soares and Filipe J. Mergulhão

Nanomaterials 2023, 13(18), 2604; https://doi.org/10.3390/nano13182604 - 21 Sep 2023

Cited by 1 | Viewed by 1219

Abstract

Graphene has been broadly studied, particularly for the fabrication of biomedical devices, owing to its physicochemical and antimicrobial properties. In this study, the antibiofilm efficacy of graphene nanoplatelet (GNP)-based composites as coatings for urinary catheters (UCs) was investigated. GNPs were functionalized with nitrogen [...] Read more.

Graphene has been broadly studied, particularly for the fabrication of biomedical devices, owing to its physicochemical and antimicrobial properties. In this study, the antibiofilm efficacy of graphene nanoplatelet (GNP)-based composites as coatings for urinary catheters (UCs) was investigated. GNPs were functionalized with nitrogen (N-GNP) and incorporated into a polydimethylsiloxane (PDMS) matrix. The resulting materials were characterized, and the N-GNP/PDMS composite was evaluated against single- and multi-species biofilms of Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Both biofilm cell composition and structure were analyzed. Furthermore, the antibacterial mechanisms of action of N-GNP were explored. The N-GNP/PDMS composite showed increased hydrophobicity and roughness compared to PDMS. In single-species biofilms, this composite significantly reduced the number of S. aureus, P. aeruginosa, and K. pneumoniae cells (by 64, 41, and 29%, respectively), and decreased S. aureus biofilm culturability (by 50%). In tri-species biofilms, a 41% reduction in total cells was observed. These results are aligned with the outcomes of the biofilm structure analysis. Moreover, N-GNP caused changes in membrane permeability and triggered reactive oxygen species (ROS) synthesis in S. aureus, whereas in Gram-negative bacteria, it only induced changes in cell metabolism. Overall, the N-GNP/PDMS composite inhibited biofilm development, showing the potential of these carbon materials as coatings for UCs. Full article

(This article belongs to the Special Issue Graphene-Based Nanomaterials II)

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13 pages, 3297 KiB

Open AccessArticle

SnO₂-Based Memory Device with Filamentary Switching Mechanism for Advanced Data Storage and Computing

by Muhammad Ismail, Chandreswar Mahata, Myounggon Kang and Sungjun Kim

Nanomaterials 2023, 13(18), 2603; https://doi.org/10.3390/nano13182603 - 21 Sep 2023

Viewed by 889

Abstract

In this study, we fabricate a Pt/TiN/SnO_x/Pt memory device using reactive sputtering to explore its potential for neuromorphic computing. The TiON interface layer, formed when TiN comes into contact with SnO₂, acts as an oxygen vacancy reservoir, aiding the [...] Read more.

In this study, we fabricate a Pt/TiN/SnO_x/Pt memory device using reactive sputtering to explore its potential for neuromorphic computing. The TiON interface layer, formed when TiN comes into contact with SnO₂, acts as an oxygen vacancy reservoir, aiding the creation of conductive filaments in the switching layer. Our SnO_x-based device exhibits remarkable endurance, with over 200 DC cycles, ON/FFO ratio (>20), and 10⁴ s retention. Set and reset voltage variabilities are impressively low, at 9.89% and 3.2%, respectively. Controlled negative reset voltage and compliance current yield reliable multilevel resistance states, mimicking synaptic behaviors. The memory device faithfully emulates key neuromorphic characteristics, encompassing both long-term potentiation (LTP) and long-term depression (LTD). The filamentary switching mechanism in the SnO_x-based memory device is explained by an oxygen vacancy concentration gradient, where current transport shifts from Ohmic to Schottky emission dominance across different resistance states. These findings exemplify the potential of SnO_x-based devices for high-density data storage memory and revolutionary neuromorphic computing applications. Full article

(This article belongs to the Special Issue Advances in Memristive Nanomaterials)

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13 pages, 4229 KiB

Open AccessArticle

Influence of Carbonization Conditions on Structural and Surface Properties of K-Doped Mo₂C Catalysts for the Synthesis of Methyl Mercaptan from CO/H₂/H₂S

by Xiangqian Zheng, Tianhao Ai, Yuhong Hu, Zhizhi Xu, Yubei Li, Huan Jiang and Yongming Luo

Nanomaterials 2023, 13(18), 2602; https://doi.org/10.3390/nano13182602 - 21 Sep 2023

Viewed by 861

Abstract

The cooperative transition of sulfur-containing pollutants of H₂S/CO/H₂ to the high-value chemical methyl mercaptan (CH₃SH) is catalyzed by Mo-based catalysts and has good application prospects. Herein, a series of Al₂O₃-supported molybdenum carbide catalysts with [...] Read more.

The cooperative transition of sulfur-containing pollutants of H₂S/CO/H₂ to the high-value chemical methyl mercaptan (CH₃SH) is catalyzed by Mo-based catalysts and has good application prospects. Herein, a series of Al₂O₃-supported molybdenum carbide catalysts with K doping (denoted herein as K-Mo₂C/Al₂O₃) are fabricated by the impregnation method, with the carbonization process occurring under different atmospheres and different temperatures between 400 and 600 °C. The CH₄-K-Mo₂C/Al₂O₃ catalyst carbonized by CH₄/H₂ at 500 °C displays unprecedented performance in the synthesis of CH₃SH from CO/H₂S/H₂, with 66.1% selectivity and a 0.2990 g·g_cat⁻¹·h⁻¹ formation rate of CH₃SH at 325 °C. H₂ temperature-programmed reduction, temperature-programmed desorption, X-ray diffraction and Raman and BET analyses reveal that the CH₄-K-Mo₂C/Al₂O₃ catalyst contains more Mo coordinatively unsaturated surface sites that are responsible for promoting the adsorption of reactants and the desorption of intermediate products, thereby improving the selectivity towards and production of CH₃SH. This study systematically investigates the effects of catalyst carbonization and passivation conditions on catalyst activity, conclusively demonstrating that Mo₂C-based catalyst systems can be highly selective for producing CH₃SH from CO/H₂S/H₂. Full article

(This article belongs to the Special Issue Nanocatalysts for Air Purification)

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16 pages, 8427 KiB

Open AccessArticle

Nanodiamond Decorated PEO Oxide Coatings on NiTi Alloy

by Karlis Grundsteins, Kateryna Diedkova, Viktoriia Korniienko, Anita Stoppel, Sascha Balakin, Kaspars Jekabsons, Una Riekstina, Natalia Waloszczyk, Agata Kołkowska, Yuliia Varava, Jörg Opitz, Wojciech Simka, Natalia Beshchasna and Maksym Pogorielov

Nanomaterials 2023, 13(18), 2601; https://doi.org/10.3390/nano13182601 - 20 Sep 2023

Cited by 1 | Viewed by 1207

Abstract

Cardiovascular diseases (CVDs) remain a leading cause of death in the European population, primarily attributed to atherosclerosis and subsequent complications. Although statin drugs effectively prevent atherosclerosis, they fail to reduce plaque size and vascular stenosis. Bare metal stents (BMS) have shown promise in [...] Read more.

Cardiovascular diseases (CVDs) remain a leading cause of death in the European population, primarily attributed to atherosclerosis and subsequent complications. Although statin drugs effectively prevent atherosclerosis, they fail to reduce plaque size and vascular stenosis. Bare metal stents (BMS) have shown promise in acute coronary disease treatment but are associated with restenosis in the stent. Drug-eluting stents (DES) have improved restenosis rates but present long-term complications. To overcome these limitations, nanomaterial-based modifications of the stent surfaces have been explored. This study focuses on the incorporation of detonation nanodiamonds (NDs) into a plasma electrolytic oxidation (PEO) coating on nitinol stents to enhance their performance. The functionalized ND showed a high surface-to-volume ratio and was incorporated into the oxide layer to mimic high-density lipoproteins (HDL) for reverse cholesterol transport (RCT). We provide substantial characterization of DND, including stability in two media (acetone and water), Fourier transmission infrared spectroscopy, and nanoparticle tracking analysis. The characterization of the modified ND revealed successful functionalization and adequate suspension stability. Scanning electron microscopy with EDX demonstrated successful incorporation of DND into the ceramic layer, but the formation of a porous surface is possible only in the high-voltage PEO. The biological assessment demonstrated the biocompatibility of the decorated nitinol surface with enhanced cell adhesion and proliferation. This study presents a novel approach to improving the performance of nitinol stents using ND-based surface modifications, providing a promising avenue for cardiovascular disease. Full article

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

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12 pages, 2661 KiB

Open AccessArticle

The Effect of Nanobubbles on Transdermal Applications

by Athanasios Ch. Mitropoulos, Christina Pappa, Ramonna I. Kosheleva and George Z. Kyzas

Nanomaterials 2023, 13(18), 2600; https://doi.org/10.3390/nano13182600 - 20 Sep 2023

Viewed by 1039

Abstract

In the present work, a new method for dermal delivery using nanobubbles (NBs) is investigated. Oxygen NBs are generated in deionized water and used to produce cosmetic formulations with hyaluronic acid as an active ingredient. Nanobubbles result in the improvement of the effect [...] Read more.

In the present work, a new method for dermal delivery using nanobubbles (NBs) is investigated. Oxygen NBs are generated in deionized water and used to produce cosmetic formulations with hyaluronic acid as an active ingredient. Nanobubbles result in the improvement of the effect and penetration of the active ingredient through Strat-M, a synthetic membrane that resembles human skin. Experiments conducted with the Franz Cell device confirm the greater penetration of the active ingredient into Strat-M due to NBs, compared to cosmetic formulations that do not contain NBs. The effect of NBs was further examined by measuring UV-Vis and FTIR spectra. A possible mechanism was outlined, too. It was also found that NBs do not change the pH or the FTIR spectrum of the cosmetic serum indicating non-toxicity. Full article

(This article belongs to the Special Issue Advances in Bioactive Nanoparticles on Wound Healing, Tissue Engineering and Drug Delivery)

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27 pages, 5147 KiB

Open AccessFeature PaperReview

State of the Art Progress in Copper Vanadate Materials for Solar Water Splitting

by Shankara S. Kalanur, Jaldappagari Seetharamappa, Qadeer Akbar Sial and Bruno G. Pollet

Nanomaterials 2023, 13(18), 2599; https://doi.org/10.3390/nano13182599 - 20 Sep 2023

Viewed by 1125

Abstract

The development of a single junction photoelectrode material having specific properties is essential and challenging for the efficient application in solar water splitting for oxygen production and a high value-added product, hydrogen. Moreover, the present material solutions based on binary metal oxides offer [...] Read more.

The development of a single junction photoelectrode material having specific properties is essential and challenging for the efficient application in solar water splitting for oxygen production and a high value-added product, hydrogen. Moreover, the present material solutions based on binary metal oxides offer limited catalytic activity and hydrogen production efficiency. Therefore, it is paramount to develop and exploit a unique range of materials derived from ternary metal oxides with specifically engineered properties to advance in photoelectrochemical (PEC) water splitting. Among the ternary oxides, copper vanadates offer promising characteristics, such as a narrow bandgap and catalytic surface properties along with favorable band edges for facile oxygen evolution reaction (OER), which is considered the bottleneck step in performing overall water dissociation. Furthermore, the copper vanadates allow the tuning of the stoichiometry through which a wide range of polymorphs and materials could be obtained. This review provides a complete outlook on the range of copper vanadates and the established synthesis approach, morphology, crystal structure, band edge properties, and PEC characterizations. Mainly, the underlying charge dynamic properties, carrier path length, effect of doping, and influence of surface catalysts are discussed. The review concludes that the advancement toward obtaining low-bandgap materials is a main challenge to overcome the limitations for efficient water dissociation to OER and copper vanadates, which offer a promising solution with their unique properties and advantages. Importantly, intense and strategically focused research is vital to overcome the scientific challenges involved in copper vanadates and to explore and exploit new polymorphs to set new efficiency benchmarks and PEC water splitting solutions. Full article

(This article belongs to the Section Energy and Catalysis)

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28 pages, 4986 KiB

Open AccessEditor’s ChoiceReview

Exposure of Rats to Multi-Walled Carbon Nanotubes: Correlation of Inhalation Exposure to Lung Burden, Bronchoalveolar Lavage Fluid Findings, and Lung Morphology

by Tatsuya Kasai and Shoji Fukushima

Nanomaterials 2023, 13(18), 2598; https://doi.org/10.3390/nano13182598 - 20 Sep 2023

Viewed by 928

Abstract

To evaluate lung toxicity due to inhalation of multi-walled carbon nanotubes (MWCNTs) in rats, we developed a unique MWCNT aerosol generator based on dry aerosolization using the aerodynamic cyclone principle. Rats were exposed to MWNT-7 (also known as Mutsui-7 and MWCNT-7) aerosolized using [...] Read more.

To evaluate lung toxicity due to inhalation of multi-walled carbon nanotubes (MWCNTs) in rats, we developed a unique MWCNT aerosol generator based on dry aerosolization using the aerodynamic cyclone principle. Rats were exposed to MWNT-7 (also known as Mutsui-7 and MWCNT-7) aerosolized using this device. We report here an analysis of previously published data and additional unpublished data obtained in 1-day, 2-week, 13-week, and 2-year inhalation exposure studies. In one-day studies, it was found that approximately 50% of the deposited MWNT-7 fibers were cleared the day after the end of exposure, but that clearance of the remaining fibers was markedly reduced. This is in agreement with the premise that the rapidly cleared fibers were deposited in the ciliated airways while the slowly cleared fibers were deposited beyond the ciliated airways in the respiratory zone. Macrophage clearance of MWNT-7 fibers from the alveoli was limited. Instead of macrophage clearance from the alveoli, containment of MWNT-7 fibers within induced granulomatous lesions was observed. The earliest changes indicative of pulmonary toxicity were seen in the bronchoalveolar lavage fluid. Macrophage-associated inflammation persisted from the one-day exposure to MWNT-7 to the end of the two-year exposure period. Correlation of lung tumor development with MWNT-7 lung burden required incorporating the concept of area under the curve for the duration of the study; the development of lung tumors induced by MWNT-7 correlated with lung burden and the duration of MWNT-7 residence in the lung. Full article

(This article belongs to the Special Issue Safety and Toxicity of Carbon Nanotubes, Nanoparticles and Other Nanomaterials)

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21 pages, 3169 KiB

Open AccessArticle

Magnetoliposomes with Calcium-Doped Magnesium Ferrites Anchored in the Lipid Surface for Enhanced DOX Release

by Beatriz D. Cardoso, Diana E. M. Fernandes, Carlos O. Amorim, Vítor S. Amaral, Paulo J. G. Coutinho, Ana Rita O. Rodrigues and Elisabete M. S. Castanheira

Nanomaterials 2023, 13(18), 2597; https://doi.org/10.3390/nano13182597 - 20 Sep 2023

Cited by 1 | Viewed by 980

Abstract

Nanotechnology has provided a new insight into cancer treatment by enabling the development of nanocarriers for the encapsulation, transport, and controlled release of antitumor drugs at the target site. Among these nanocarriers, magnetic nanosystems have gained prominence. This work presents the design, development, [...] Read more.

Nanotechnology has provided a new insight into cancer treatment by enabling the development of nanocarriers for the encapsulation, transport, and controlled release of antitumor drugs at the target site. Among these nanocarriers, magnetic nanosystems have gained prominence. This work presents the design, development, and characterization of magnetoliposomes (MLs), wherein superparamagnetic nanoparticles are coupled to the lipid surface. For this purpose, dimercaptosuccinic acid (DMSA)-functionalized Ca_0.25Mg_0.75Fe₂O₄ superparamagnetic nanoparticles were prepared for the first time. The magnetic nanoparticles demonstrated a cubic shape with an average size of 13.36 nm. Furthermore, their potential for photothermal hyperthermia was evaluated using 4 mg/mL, 2 mg/mL, and 1 mg/mL concentrations of NPs@DMSA, which demonstrated a maximum temperature variation of 20.4 °C, 11.4 °C, and 7.3 °C, respectively, during a 30 min NIR-laser irradiation. Subsequently, these nanoparticles were coupled to the lipid surface of DPPC/DSPC/CHEMS and DPPC/DSPC/CHEMS/DSPE-PEG-based MLs using a new synthesis methodology, exhibiting average sizes of 153 ± 8 nm and 136 ± 2 nm, respectively. Doxorubicin (DOX) was encapsulated with high efficiency, achieving 96% ± 2% encapsulation in non-PEGylated MLs and 98.0% ± 0.6% in stealth MLs. Finally, drug release assays of the DOX-loaded DPPC/DSPC/CHEMS MLs were performed under different conditions of temperature (37 °C and 42 °C) and pH (5.5 and 7.4), simulating physiological and therapeutic conditions. The results revealed a higher release rate at 42 °C and acidic pH. Release rates significantly increased when introducing the stimulus of laser-induced photothermal hyperthermia at 808 nm (1 W/cm²) for 5 min. After 48 h of testing, at pH 5.5, 67.5% ± 0.5% of DOX was released, while at pH 7.4, only a modest release of 27.0% ± 0.1% was achieved. The results demonstrate the potential of the MLs developed in this work to the controlled release of DOX under NIR-laser stimulation and acidic environments and to maintain a sustained and reduced release profile in physiological environments with pH 7.4. Full article

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13 pages, 3524 KiB

Open AccessArticle

Scanning Tunneling Microscopy Study of Lipoic Acid, Mannose, and cRGD@AuNPs Conjugates

by Andrés Rodríguez-Galván, Mitzi Reyes, Marisol Ávila-Cruz, Margarita Rivera and Vladimir A. Basiuk

Nanomaterials 2023, 13(18), 2596; https://doi.org/10.3390/nano13182596 - 20 Sep 2023

Viewed by 882

Abstract

The functionalization of AuNPs with different biological elements was achieved to investigate their possibility in biomedical applications such as drug delivery, vaccine development, sensing, and imaging. Biofunctionalized AuNPs are pursued for applications such as drug delivery, vaccine development, sensing, and imaging. In this [...] Read more.

The functionalization of AuNPs with different biological elements was achieved to investigate their possibility in biomedical applications such as drug delivery, vaccine development, sensing, and imaging. Biofunctionalized AuNPs are pursued for applications such as drug delivery, vaccine development, sensing, and imaging. In this study, AuNPs with diameters of 20 nm were functionalized with lipoic acid, mannose, or the cRGD peptide. By using UV-vis spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering, transmission electron microscopy, and scanning tunneling microscopy techniques, we showed that AuNPs can be functionalized by these biomolecules in a reliable way to obtain conjugates to explore potential biomedical applications. In particular, we demonstrate that the STM technique can be employed to analyze biofunctionalized AuNPs, and the obtained information can be valuable in the design of biomedical applications. Full article

(This article belongs to the Special Issue Synthesis and Applications of Gold Nanoparticles)

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10 pages, 5014 KiB

Open AccessArticle

Nanostructured PbSe Films Deposited by Spray Pyrolysis Using PbSe Colloidal Solutions

by Esteban Díaz-Torres, Jorge Roque, Alma Sofía Arreola-Pina, Manuel Alejandro Pérez-Guzmán, Rebeca Ortega-Amaya and Mauricio Ortega-López

Nanomaterials 2023, 13(18), 2595; https://doi.org/10.3390/nano13182595 - 20 Sep 2023

Viewed by 850

Abstract

This work describes the spray pyrolysis deposition of PbSe films, using as-prepared PbSe colloids as the starting solution. The PbSe colloids were prepared by using the alkahest approach, where Pb and Se precursors were made to react with the following green polyols: glycerin, [...] Read more.

This work describes the spray pyrolysis deposition of PbSe films, using as-prepared PbSe colloids as the starting solution. The PbSe colloids were prepared by using the alkahest approach, where Pb and Se precursors were made to react with the following green polyols: glycerin, ethylene glycol, and propylene glycol, to subsequently spray them onto glass substrates. The results of the characterization indicated that amine or thiol groups-free and single-phase rock-salt cubic PbSe powder was obtained, producing nanocrystals 16–30 nm in size. X-ray diffraction also showed that the PbSe films containing PbSeO₃ and PbO·xH₂O as impurity phases were produced during the deposition. The morphology of the powders and films was developed by a self-assembly process, in which the primary PbSe nanoparticles self-assemble to produce peanut-like microstructures. Additionally, a non-continuous and porous feature was formed in the thick films. Certain films revealed optical structures characterized by broad- and low-intensity bands resembling an exciton-like behavior. This could be attributed to the presence of nanocrystals with a size less than the Bohr radius, indicating reminiscent quantum effects. The results suggest that the usage of colloidal dispersions as spray solutions represents an effective approach to forming PbSe films, as well as that the synthesis method allows for the elimination of thiol and amine groups before deposition, significantly simplifying the process. Full article

(This article belongs to the Special Issue Nano-Structured Thin Films: Growth, Characteristics, and Application)

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4 pages, 195 KiB

Open AccessEditorial

Editorial for the Special Issue “Amorphous and Nanocrystalline Semiconductors: Selected Papers from ICANS 29”

by Kunji Chen, Shunri Oda and Linwei Yu

Nanomaterials 2023, 13(18), 2594; https://doi.org/10.3390/nano13182594 - 20 Sep 2023

Viewed by 680

Abstract

The 29th International Conference on Amorphous and Nanocrystalline Semiconductors served as a continuation of the biennial conference that has been held since 1965 [...] Full article

(This article belongs to the Special Issue Amorphous and Nanocrystalline Semiconductors: Selected Papers from ICANS 29)

12 pages, 2866 KiB

Open AccessArticle

Eco-Friendly Dispersant-Free Purification Method of Boron Nitride Nanotubes through Controlling Surface Tension and Steric Repulsion with Solvents

by Minsung Kang, Jungmo Kim, Hongjin Lim, Jaehyoung Ko, Hong-Sik Kim, Yongho Joo, Se Youn Moon, Se Gyu Jang, Eunji Lee and Seokhoon Ahn

Nanomaterials 2023, 13(18), 2593; https://doi.org/10.3390/nano13182593 - 19 Sep 2023

Viewed by 1173

Abstract

Boron nitride nanotubes (BNNTs) were purified without the use of a dispersant by controlling the surface tension and steric repulsion of solvent molecules. This method effectively enhanced the difference in solubilities of impurities and BNNTs. The purification process involved optimizing the alkyl-chains of [...] Read more.

Boron nitride nanotubes (BNNTs) were purified without the use of a dispersant by controlling the surface tension and steric repulsion of solvent molecules. This method effectively enhanced the difference in solubilities of impurities and BNNTs. The purification process involved optimizing the alkyl-chains of alcohol solvents and adjusting the concentration of alcohol solvent in water to regulate surface tension and steric repulsion. Among the solvents tested, a 70 wt% t-butylalcohol in water mixture exhibited the highest selective isolation of BNNTs from impurities based on differences in solubilities. This favorable outcome was attributed to the surface tension matching with BNNTs, steric repulsion from bulky alkyl chain structures, and differences in interfacial energy between BNNT–liquid and impurity–liquid interfaces. Through this optimized purification process, impurities were removed to an extent of up to 93.3%. Additionally, the purified BNNTs exhibited a distinct liquid crystal phase, which was not observed in the unpurified BNNTs. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes: Volume II)

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14 pages, 9331 KiB

Open AccessCommunication

Si-Based Polarizer and 1-Bit Phase-Controlled Non-Polarizing Beam Splitter-Based Integrated Metasurface for Extended Shortwave Infrared

by Leidong Shi, Lidan Lu, Weiqiang Chen, Guang Chen, Yanlin He, Guanghui Ren and Lianqing Zhu

Nanomaterials 2023, 13(18), 2592; https://doi.org/10.3390/nano13182592 - 19 Sep 2023

Viewed by 769

Abstract

Metasurfaces, composed of micro-nano-structured planar materials, offer highly tunable control over incident light and find significant applications in imaging, navigation, and sensing. However, highly efficient polarization devices are scarce for the extended shortwave infrared (ESWIR) range (1.7~2.5 μm). This paper proposes and demonstrates [...] Read more.

Metasurfaces, composed of micro-nano-structured planar materials, offer highly tunable control over incident light and find significant applications in imaging, navigation, and sensing. However, highly efficient polarization devices are scarce for the extended shortwave infrared (ESWIR) range (1.7~2.5 μm). This paper proposes and demonstrates a highly efficient all-dielectric diatomic metasurface composed of single-crystalline Si nanocylinders and nanocubes on SiO₂. This metasurface can serve as a nanoscale linear polarizer for generating polarization-angle-controllable linearly polarized light. At the wavelength of 2172 nm, the maximum transmission efficiency, extinction ratio, and linear polarization degree can reach 93.43%, 45.06 dB, and 0.9973, respectively. Moreover, a nonpolarizing beam splitter (NPBS) was designed and deduced theoretically based on this polarizer, which can achieve a splitting angle of ±13.18° and a phase difference of π. This beam splitter can be equivalently represented as an integration of a linear polarizer with controllable polarization angles and an NPBS with one-bit phase modulation. It is envisaged that through further design optimization, the phase tuning range of the metasurface can be expanded, allowing for the extension of the operational wavelength into the mid-wave infrared range, and the splitting angle is adjustable. Moreover, it can be utilized for integrated polarization detectors and be a potential application for optical digital encoding metasurfaces. Full article

(This article belongs to the Special Issue Experimental and Numerical Modelling of Nanostructures Processing, Structure and Properties: Volume II)

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11 pages, 2249 KiB

Open AccessArticle

The Influence of Capping Layers on Tunneling Magnetoresistance and Microstructure in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions upon Annealing

by Geunwoo Kim, Soogil Lee, Sanghwa Lee, Byonggwon Song, Byung-Kyu Lee, Duhyun Lee, Jin Seo Lee, Min Hyeok Lee, Young Keun Kim and Byong-Guk Park

Nanomaterials 2023, 13(18), 2591; https://doi.org/10.3390/nano13182591 - 19 Sep 2023

Cited by 1 | Viewed by 1268

Abstract

This study investigates the effects of annealing on the tunnel magnetoresistance (TMR) ratio in CoFeB/MgO/CoFeB-based magnetic tunnel junctions (MTJs) with different capping layers and correlates them with microstructural changes. It is found that the capping layer plays an important role in determining the [...] Read more.

This study investigates the effects of annealing on the tunnel magnetoresistance (TMR) ratio in CoFeB/MgO/CoFeB-based magnetic tunnel junctions (MTJs) with different capping layers and correlates them with microstructural changes. It is found that the capping layer plays an important role in determining the maximum TMR ratio and the corresponding annealing temperature (T_ann). For a Pt capping layer, the TMR reaches ~95% at a T_ann of 350 °C, then decreases upon a further increase in T_ann. A microstructural analysis reveals that the low TMR is due to severe intermixing in the Pt/CoFeB layers. On the other hand, when introducing a Ta capping layer with suppressed diffusion into the CoFeB layer, the TMR continues to increase with T_ann up to 400 °C, reaching ~250%. Our findings indicate that the proper selection of a capping layer can increase the annealing temperature of MTJs so that it becomes compatible with the complementary metal-oxide-semiconductor backend process. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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13 pages, 9238 KiB

Open AccessArticle

Sculpting Windows onto AuAg Hollow Cubic Nanocrystals

by Javier Patarroyo, Neus G. Bastús and Victor Puntes

Nanomaterials 2023, 13(18), 2590; https://doi.org/10.3390/nano13182590 - 19 Sep 2023

Cited by 1 | Viewed by 654

Abstract

Using surfactants in the galvanic replacement reaction (GRR) offers a versatile approach to modulating hollow metal nanocrystal (NC) morphology and composition. Among the various surfactants available, quaternary ammonium cationic surfactants are commonly utilised. However, understanding how they precisely influence morphological features, such as [...] Read more.

Using surfactants in the galvanic replacement reaction (GRR) offers a versatile approach to modulating hollow metal nanocrystal (NC) morphology and composition. Among the various surfactants available, quaternary ammonium cationic surfactants are commonly utilised. However, understanding how they precisely influence morphological features, such as the size and void distribution, is still limited. In this study, we aim to uncover how adding different surfactants—CTAB, CTAC, CTApTS, and PVP—can fine-tune the morphological characteristics of AuAg hollow NCs synthesised via GRR at room temperature. Our findings reveal that the halide counterion in the surfactant significantly controls void formation within the hollow structure. When halogenated surfactants, such as CTAB or CTAC, are employed, multichambered opened nanoboxes are formed. In contrast, with non-halogenated CTApTS, single-walled closed nanoboxes with irregularly thick walls form. Furthermore, when PVP, a polymer surfactant, is utilised, changes in concentration lead to the production of well-defined single-walled closed nanoboxes. These observations highlight the role of surfactants in tailoring the morphology of hollow NCs synthesised through GRR. Full article

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

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18 pages, 4392 KiB

Open AccessArticle

Optical Properties of Sc_nY_n (Y = N, P As) Nanoparticles

by Fotios I. Michos, Alexandros G. Chronis and Michail M. Sigalas

Nanomaterials 2023, 13(18), 2589; https://doi.org/10.3390/nano13182589 - 19 Sep 2023

Viewed by 647

Abstract

In this work, using Density Functional Theory (DFT) and Time Dependent DFT, the absorption spectrum, the optical gap, and the binding energy of scandium pnictogen family nanoparticles (NPs) are examined. The calculated structures are created from an initial cubic-like building block of the [...] Read more.

In this work, using Density Functional Theory (DFT) and Time Dependent DFT, the absorption spectrum, the optical gap, and the binding energy of scandium pnictogen family nanoparticles (NPs) are examined. The calculated structures are created from an initial cubic-like building block of the form Sc₄Y₄, where Y = N, P, As after elongation along one and two perpendicular directions. The existence of stable structures over a wide range of morphologies was one of the main findings of this research, and this led to the study of several exotic NPs. The absorption spectrum of all the studied structures is within the visible spectrum, while the optical gap varies between 1.62 and 3 eV. These NPs could be used in the field in photovoltaics (quantum dot sensitized solar cells) and display applications. Full article

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17 pages, 4162 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Exfoliation of Expanded Graphite to Graphene-Based Materials and Modification with Palladium Nanoparticles for Hydrogen Storage

by Darren Chow, Nicholas Burns, Emmanuel Boateng, Joshua van der Zalm, Stefan Kycia and Aicheng Chen

Nanomaterials 2023, 13(18), 2588; https://doi.org/10.3390/nano13182588 - 19 Sep 2023

Cited by 1 | Viewed by 1388

Abstract

Hydrogen is a promising green fuel carrier that can replace fossil fuels; however, its storage is still a challenge. Carbon-based materials with metal catalysts have recently been the focus of research for solid-state hydrogen storage due to their efficacy and low cost. Here, [...] Read more.

Hydrogen is a promising green fuel carrier that can replace fossil fuels; however, its storage is still a challenge. Carbon-based materials with metal catalysts have recently been the focus of research for solid-state hydrogen storage due to their efficacy and low cost. Here, we report on the exfoliation of expanded graphite (EG) through high shear mixing and probe tip sonication methods to form graphene-based nanomaterial ShEG and sEG, respectively. The exfoliation processes were optimized based on electrochemical capacitance measurements. The exfoliated EG was further functionalized with palladium nanoparticles (Pd-NP) for solid-state hydrogen storage. The prepared graphene-based nanomaterials (ShEG and sEG) and the nanocomposites (Pd-ShEG and Pd-sEG) were characterized with various traditional techniques (e.g., SEM, TEM, EDX, XPS, Raman, XRD) and the advanced high-resolution pair distribution function (HRPDF) analysis. Electrochemical hydrogen uptake and release (Q_H) were measured, showing that the sEG decorated with Pd-NP (Pd-sEG, 31.05 mC cm⁻²) and ShEG with Pd-NP (Pd-ShEG, 24.54 mC cm⁻²) had a notable improvement over Pd-NP (9.87 mC cm⁻²) and the composite of Pd-EG (14.7 mC cm⁻²). Q_H showed a strong linear relationship with an effective surface area to volume ratio, indicating nanoparticle size as a determining factor for hydrogen uptake and release. This work is a promising step toward the design of the high-performance solid-state hydrogen storage devices through mechanical exfoliation of the substrate EG to control nanoparticle size and dispersion. Full article

(This article belongs to the Special Issue Functional Graphene-Based Nanodevices)

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11 pages, 4405 KiB

Open AccessArticle

Geometrical Selection of GaN Nanowires Grown by Plasma-Assisted MBE on Polycrystalline ZrN Layers

by Karol Olszewski, Marta Sobanska, Vladimir G. Dubrovskii, Egor D. Leshchenko, Aleksandra Wierzbicka and Zbigniew R. Zytkiewicz

Nanomaterials 2023, 13(18), 2587; https://doi.org/10.3390/nano13182587 - 19 Sep 2023

Viewed by 878

Abstract

GaN nanowires grown on metal substrates have attracted increasing interest for a wide range of applications. Herein, we report GaN nanowires grown by plasma-assisted molecular beam epitaxy on thin polycrystalline ZrN buffer layers, sputtered onto Si(111) substrates. The nanowire orientation was studied by [...] Read more.

GaN nanowires grown on metal substrates have attracted increasing interest for a wide range of applications. Herein, we report GaN nanowires grown by plasma-assisted molecular beam epitaxy on thin polycrystalline ZrN buffer layers, sputtered onto Si(111) substrates. The nanowire orientation was studied by X-ray diffraction and scanning electron microscopy, and then described within a model as a function of the Ga beam angle, nanowire tilt angle, and substrate rotation. We show that vertically aligned nanowires grow faster than inclined nanowires, which leads to an interesting effect of geometrical selection of the nanowire orientation in the directional molecular beam epitaxy technique. After a given growth time, this effect depends on the nanowire surface density. At low density, the nanowires continue to grow with random orientations as nucleated. At high density, the effect of preferential growth induced by the unidirectional supply of the material in MBE starts to dominate. Faster growing nanowires with smaller tilt angles shadow more inclined nanowires that grow slower. This helps to obtain more regular ensembles of vertically oriented GaN nanowires despite their random position induced by the metallic grains at nucleation. The obtained dense ensembles of vertically aligned GaN nanowires on ZrN/Si(111) surfaces are highly relevant for device applications. Importantly, our results are not specific for GaN nanowires on ZrN buffers, and should be relevant for any nanowires that are epitaxially linked to the randomly oriented surface grains in the directional molecular beam epitaxy. Full article

(This article belongs to the Special Issue New Advances in Nanowires and Quantum Dots)

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25 pages, 2339 KiB

Open AccessReview

Advancements in Nanoparticle Deposition Techniques for Diverse Substrates: A Review

by Daniel Escorcia-Díaz, Sebastián García-Mora, Leidy Rendón-Castrillón, Margarita Ramírez-Carmona and Carlos Ocampo-López

Nanomaterials 2023, 13(18), 2586; https://doi.org/10.3390/nano13182586 - 19 Sep 2023

Cited by 10 | Viewed by 2610

Abstract

Nanoparticle deposition on various substrates has gained significant attention due to the potential applications of nanoparticles in various fields. This review paper comprehensively analyzes different nanoparticle deposition techniques on ceramic, polymeric, and metallic substrates. The deposition techniques covered include electron gun evaporation, physical [...] Read more.

Nanoparticle deposition on various substrates has gained significant attention due to the potential applications of nanoparticles in various fields. This review paper comprehensively analyzes different nanoparticle deposition techniques on ceramic, polymeric, and metallic substrates. The deposition techniques covered include electron gun evaporation, physical vapor deposition, plasma enriched chemical vapor deposition (PECVD), electrochemical deposition, chemical vapor deposition, electrophoretic deposition, laser metal deposition, and atomic layer deposition (ALD), thermophoretic deposition, supercritical deposition, spin coating, and dip coating. Additionally, the sustainability aspects of these deposition techniques are discussed, along with their potential applications in anti-icing, antibacterial power, and filtration systems. Finally, the review explores the importance of deposition purities in achieving optimal nanomaterial performance. This comprehensive review aims to provide valuable insights into state-of-the-art techniques and applications in the field of nanomaterial deposition. Full article

(This article belongs to the Special Issue Synthesis of Nanocomposites and Catalysis Applications II)

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43 pages, 5028 KiB

Open AccessEditor’s ChoiceReview

A Review of the Current State of Magnetic Force Microscopy to Unravel the Magnetic Properties of Nanomaterials Applied in Biological Systems and Future Directions for Quantum Technologies

by Robert Winkler, Miguel Ciria, Margaret Ahmad, Harald Plank and Carlos Marcuello

Nanomaterials 2023, 13(18), 2585; https://doi.org/10.3390/nano13182585 - 18 Sep 2023

Cited by 22 | Viewed by 2194

Abstract

Magnetism plays a pivotal role in many biological systems. However, the intensity of the magnetic forces exerted between magnetic bodies is usually low, which demands the development of ultra-sensitivity tools for proper sensing. In this framework, magnetic force microscopy (MFM) offers excellent lateral [...] Read more.

Magnetism plays a pivotal role in many biological systems. However, the intensity of the magnetic forces exerted between magnetic bodies is usually low, which demands the development of ultra-sensitivity tools for proper sensing. In this framework, magnetic force microscopy (MFM) offers excellent lateral resolution and the possibility of conducting single-molecule studies like other single-probe microscopy (SPM) techniques. This comprehensive review attempts to describe the paramount importance of magnetic forces for biological applications by highlighting MFM’s main advantages but also intrinsic limitations. While the working principles are described in depth, the article also focuses on novel micro- and nanofabrication procedures for MFM tips, which enhance the magnetic response signal of tested biomaterials compared to commercial nanoprobes. This work also depicts some relevant examples where MFM can quantitatively assess the magnetic performance of nanomaterials involved in biological systems, including magnetotactic bacteria, cryptochrome flavoproteins, and magnetic nanoparticles that can interact with animal tissues. Additionally, the most promising perspectives in this field are highlighted to make the reader aware of upcoming challenges when aiming toward quantum technologies. Full article

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Nanomaterials, Volume 13, Issue 18 (September-2 2023) – 119 articles

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