Nanomaterials

17 pages, 4645 KiB

Open AccessArticle

Dynamically Tunable Assemblies of Superparamagnetic Nanoparticles Stabilized with Liquid Crystal-like Ligands in Organic Thin Films

by Zuzanna Z. Jańczuk, Agnieszka Jedrych, Sylwia Parzyszek, Anita Gardias, Jacek Szczytko and Michal Wojcik

Nanomaterials 2023, 13(21), 2908; https://doi.org/10.3390/nano13212908 - 6 Nov 2023

Viewed by 1457

Abstract

The process of arranging magnetic nanoparticles (MNPs) into long-range structures that can be dynamically and reversibly controlled is challenging, although interesting for emerging spintronic applications. Here, we report composites of MNPs in excess of LC-like ligands as promising materials for MNP-based technologies. The [...] Read more.

The process of arranging magnetic nanoparticles (MNPs) into long-range structures that can be dynamically and reversibly controlled is challenging, although interesting for emerging spintronic applications. Here, we report composites of MNPs in excess of LC-like ligands as promising materials for MNP-based technologies. The organic part ensures the assembly of MNP into long-range ordered phases as well as precise and temperature-reversible control over the arrangement. The dynamic changes are fully reversible, which we confirm using X-ray diffraction (XRD). This methodology allows for the precise control of the nanomaterial’s structure in a thin film at different temperatures, translating to variable unit cell parameters. The composition of the materials (XPS, TGA), their structure (XRD), and magnetic properties (SQUID) were performed. Overall, this study confirms that LC-like materials provide the ability to dynamically control the magnetic nanoparticles in thin films, particularly the reversible control of their self-organization. Full article

(This article belongs to the Section Nanocomposite Materials)

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9 pages, 2782 KiB

Open AccessCommunication

Pillar Growth by Focused Electron Beam-Induced Deposition Using a Bimetallic Precursor as Model System: High-Energy Fragmentation vs. Low-Energy Decomposition

by Robert Winkler, Michele Brugger-Hatzl, Fabrizio Porrati, David Kuhness, Thomas Mairhofer, Lukas M. Seewald, Gerald Kothleitner, Michael Huth, Harald Plank and Sven Barth

Nanomaterials 2023, 13(21), 2907; https://doi.org/10.3390/nano13212907 - 6 Nov 2023

Cited by 3 | Viewed by 1561

Abstract

Electron-induced fragmentation of the HFeCo₃(CO)₁₂ precursor allows direct-write fabrication of 3D nanostructures with metallic contents of up to >95 at %. While microstructure and composition determine the physical and functional properties of focused electron beam-induced deposits, they also provide fundamental [...] Read more.

Electron-induced fragmentation of the HFeCo₃(CO)₁₂ precursor allows direct-write fabrication of 3D nanostructures with metallic contents of up to >95 at %. While microstructure and composition determine the physical and functional properties of focused electron beam-induced deposits, they also provide fundamental insights into the decomposition process of precursors, as elaborated in this study based on EDX and TEM. The results provide solid information suggesting that different dominant fragmentation channels are active in single-spot growth processes for pillar formation. The use of the single source precursor provides a unique insight into high- and low-energy fragmentation channels being active in the same deposit formation process. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: New Trends in Inorganic Nanoparticles and Composites from Preparation to Applications)

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13 pages, 985 KiB

Open AccessReview

Recent Trends in Foliar Nanofertilizers: A Review

by Yanru Ding, Weichen Zhao, Guikai Zhu, Quanlong Wang, Peng Zhang and Yukui Rui

Nanomaterials 2023, 13(21), 2906; https://doi.org/10.3390/nano13212906 - 6 Nov 2023

Cited by 8 | Viewed by 4292

Abstract

It is estimated that 40–70%, 80–90% and 50–90% of the conventional macronutrients N, P and K applied to the soil are lost, respectively, resulting in considerable loss of resources. Compared to conventional fertilizers, nanofertilizers have the advantages of controlled release, high nutrient utilization, [...] Read more.

It is estimated that 40–70%, 80–90% and 50–90% of the conventional macronutrients N, P and K applied to the soil are lost, respectively, resulting in considerable loss of resources. Compared to conventional fertilizers, nanofertilizers have the advantages of controlled release, high nutrient utilization, low cost and relatively low environmental pollution due to their small size (1–100 nm) and high specific surface area. The application of nanofertilizers is an up-and-coming field of agricultural research and is an attractive and economical substitute for common fertilizers which can boost global food productivity sustainably. Foliar fertilization is a popular way to satisfy the needs of higher plants. Because of its small application dose, faster nutrient uptake than soil application and relatively less environmental pollution, foliar fertilization is more popular among plants. It can be seen that nanofertilizers and foliar fertilization are the hotspots of attention at present and that current research on the foliar application of nanofertilizers is not as extensive as that on soil application. Based on this background, this paper provides an overview of various applications of foliar spraying of nanofertilizers in agriculture, including applications in improving crop yield and quality as well as mitigating heavy metal stress, salt stress and drought stress. Full article

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10 pages, 3898 KiB

Open AccessArticle

The Bonding State and Surface Roughness of Carbon-Doped TiZrN Coatings for Hydrogen Permeation Barriers

by Seonghoon Kim, Taewoo Kim, Seungjae Lee and Heesoo Lee

Nanomaterials 2023, 13(21), 2905; https://doi.org/10.3390/nano13212905 - 5 Nov 2023

Viewed by 1269

Abstract

We doped carbon into a TiZrN coating to reduce hydrogen permeability, and investigated the phase formation, bonding state, microstructure, and surface roughness of the carbon-doped TiZrN. The laser output for laser carburization was limited to a range of 20–50%. The grain size of [...] Read more.

We doped carbon into a TiZrN coating to reduce hydrogen permeability, and investigated the phase formation, bonding state, microstructure, and surface roughness of the carbon-doped TiZrN. The laser output for laser carburization was limited to a range of 20–50%. The grain size of the TiZrN coatings decreased from 26.49 nm before carburization to 18.31 nm after carburization. For XPS analysis, the sp²/sp³ ratio was 1.23 at 20% laser output, but it showed 2.64 at 40% laser output, which means that amorphous carbon was formed. As the grain size decreased with the formation of amorphous carbon, the surface microstructure of the carbon-doped TiZrN coatings transitioned to an intergranular structure, indicating the creation of amorphous carbon-embedded (Ti, Zr)(C, N) in the coating. The surface roughness (Ra) of the carbon-doped TiZrN coating was decreased to a maximum of 7.12 nm, and the hydrogen permeability correspondingly decreased by 78% at 573 K. Full article

(This article belongs to the Special Issue Nanostructured Thin Films: Growth, Properties and Applications)

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32 pages, 11676 KiB

Open AccessReview

Luminescence Thermometry with Nanoparticles: A Review

by Ljubica Đačanin Far and Miroslav D. Dramićanin

Nanomaterials 2023, 13(21), 2904; https://doi.org/10.3390/nano13212904 - 5 Nov 2023

Cited by 18 | Viewed by 4330

Abstract

Luminescence thermometry has emerged as a very versatile optical technique for remote temperature measurements, exhibiting a wide range of applicability spanning from cryogenic temperatures to 2000 K. This technology has found extensive utilization across many disciplines. In the last thirty years, there has [...] Read more.

Luminescence thermometry has emerged as a very versatile optical technique for remote temperature measurements, exhibiting a wide range of applicability spanning from cryogenic temperatures to 2000 K. This technology has found extensive utilization across many disciplines. In the last thirty years, there has been significant growth in the field of luminous thermometry. This growth has been accompanied by the development of temperature read-out procedures, the creation of luminescent materials for very sensitive temperature probes, and advancements in theoretical understanding. This review article primarily centers on luminescent nanoparticles employed in the field of luminescence thermometry. In this paper, we provide a comprehensive survey of the recent literature pertaining to the utilization of lanthanide and transition metal nanophosphors, semiconductor quantum dots, polymer nanoparticles, carbon dots, and nanodiamonds for luminescence thermometry. In addition, we engage in a discussion regarding the benefits and limitations of nanoparticles in comparison with conventional, microsized probes for their application in luminescent thermometry. Full article

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

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19 pages, 5296 KiB

Open AccessArticle

Dewatered Sludge Decorated with Nanoparticles for Alum Sludge Conditioning towards the Concept of “End-of-Waste”

by Hossam A. Nabwey and Maha A. Tony

Nanomaterials 2023, 13(21), 2903; https://doi.org/10.3390/nano13212903 - 5 Nov 2023

Viewed by 1560

Abstract

The circular economy concept is leading environmental engineering in the search for “End-of-Waste” criteria. Untreated waste residue results from drinking water treatment plants, causing severe environmental issues, and its reuse is essential. In this regard, this investigation introduces the beneficial reuses [...] Read more.

The circular economy concept is leading environmental engineering in the search for “End-of-Waste” criteria. Untreated waste residue results from drinking water treatment plants, causing severe environmental issues, and its reuse is essential. In this regard, this investigation introduces the beneficial reuses of alum sludge cake to close the loop between sludge waste generation and reuse. Considering alum sludge as a resource for dewatering instead of its categorization as a waste reflects an “End-of-Waste” approach. Alum sludge cake was thermally calcined at 400 °C and named thermally treated alum sludge cake (TAS-cake). In this study, TAS-cake decorated with magnetite with a percent weight of 5 to 1%, respectively, was labeled as TAS-cake@Fe-(5-1). X-ray diffraction (XRD) and morphologies were applied to characterize the hybrid composite. A Fenton-based hybrid composite was applied to extrude water from alum sludge for 7 min of conditioning time. Furthermore, the factorial design based on response surface methodology (RSM) was applied to optimize the operational variables. TAS-cake@Fe-(5-1) and hydrogen peroxide revealed 1.2 g/L and 740 mg/L doses at pH 3.0, showing pronounced performance and revealing the highest capillary suction time (CST) reduction, which reached 53%. A temperature increase also showed a pronounced enhancement effect on the sludge dewaterability that reached 72% when 55 °C was applied. Thus, such a novel conditioner is a promising candidate for alum sludge conditioning. Full article

(This article belongs to the Topic Emerging Materials in Water and Waste Remediation Processes)

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20 pages, 10471 KiB

Open AccessReview

Emerging Roles of Microrobots for Enhancing the Sensitivity of Biosensors

by Xiaolong Lu, Jinhui Bao, Ying Wei, Shuting Zhang, Wenjuan Liu and Jie Wu

Nanomaterials 2023, 13(21), 2902; https://doi.org/10.3390/nano13212902 - 4 Nov 2023

Cited by 2 | Viewed by 1704

Abstract

To meet the increasing needs of point-of-care testing in clinical diagnosis and daily health monitoring, numerous cutting-edge techniques have emerged to upgrade current portable biosensors with higher sensitivity, smaller size, and better intelligence. In particular, due to the controlled locomotion characteristics in the [...] Read more.

To meet the increasing needs of point-of-care testing in clinical diagnosis and daily health monitoring, numerous cutting-edge techniques have emerged to upgrade current portable biosensors with higher sensitivity, smaller size, and better intelligence. In particular, due to the controlled locomotion characteristics in the micro/nano scale, microrobots can effectively enhance the sensitivity of biosensors by disrupting conventional passive diffusion into an active enrichment during the test. In addition, microrobots are ideal to create biosensors with functions of on-demand delivery, transportation, and multi-objective detections with the capability of actively controlled motion. In this review, five types of portable biosensors and their integration with microrobots are critically introduced. Microrobots can enhance the detection signal in fluorescence intensity and surface-enhanced Raman scattering detection via the active enrichment. The existence and quantity of detection substances also affect the motion state of microrobots for the locomotion-based detection. In addition, microrobots realize the indirect detection of the bio-molecules by functionalizing their surfaces in the electrochemical current and electrochemical impedance spectroscopy detections. We pay a special focus on the roles of microrobots with active locomotion to enhance the detection performance of portable sensors. At last, perspectives and future trends of microrobots in biosensing are also discussed. Full article

(This article belongs to the Special Issue Advances in Micro-/Nanorobotics)

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11 pages, 1150 KiB

Open AccessFeature PaperArticle

Multivariate Analysis of Protein–Nanoparticle Binding Data Reveals a Selective Effect of Nanoparticle Material on the Formation of Soft Corona

by Susannah Emily Cornwell, Sarah Ogechukwu Okocha and Enrico Ferrari

Nanomaterials 2023, 13(21), 2901; https://doi.org/10.3390/nano13212901 - 4 Nov 2023

Cited by 2 | Viewed by 1437

Abstract

When nanoparticles are introduced into the bloodstream, plasma proteins accumulate at their surface, forming a protein corona. This corona affects the properties of intravenously administered nanomedicines. The firmly bound layer of plasma proteins in direct contact with the nanomaterial is called the “hard [...] Read more.

When nanoparticles are introduced into the bloodstream, plasma proteins accumulate at their surface, forming a protein corona. This corona affects the properties of intravenously administered nanomedicines. The firmly bound layer of plasma proteins in direct contact with the nanomaterial is called the “hard corona”. There is also a “soft corona” of loosely associated proteins. While the hard corona has been extensively studied, the soft corona is less understood due to its inaccessibility to analytical techniques. Our study used dynamic light scattering to determine the dissociation constant and thickness of the protein corona formed in solutions of silica or gold nanoparticles mixed with serum albumin, transferrin or prothrombin. Multivariate analysis showed that the nanoparticle material had a greater impact on binding properties than the protein type. Serum albumin had a distinct binding pattern compared to the other proteins tested. This pilot study provides a blueprint for future investigations into the complexity of the soft protein corona, which is key to developing nanomedicines. Full article

(This article belongs to the Special Issue Nanomaterials for Applied Nanotechnology and Nanoscience)

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Graphical abstract

19 pages, 4437 KiB

Open AccessFeature PaperReview

Collective Behaviors of Isotropic Micromotors: From Assembly to Reconstruction and Motion Control under External Fields

by Kai Feng, Ling Chen, Xinle Zhang, Jiang Gong, Jinping Qu and Ran Niu

Nanomaterials 2023, 13(21), 2900; https://doi.org/10.3390/nano13212900 - 3 Nov 2023

Viewed by 1711

Abstract

Swarms of self-propelled micromotors can mimic the processes of natural systems and construct artificial intelligent materials to perform complex collective behaviors. Compared to self-propelled Janus micromotors, the isotropic colloid motors, also called micromotors or microswimmers, have advantages in self-assembly to form micromotor swarms, [...] Read more.

Swarms of self-propelled micromotors can mimic the processes of natural systems and construct artificial intelligent materials to perform complex collective behaviors. Compared to self-propelled Janus micromotors, the isotropic colloid motors, also called micromotors or microswimmers, have advantages in self-assembly to form micromotor swarms, which are efficient in resistance to external disturbance and the delivery of large quantity of cargos. In this minireview, we summarize the fundamental principles and interactions for the assembly of isotropic active particles to generate micromotor swarms. Recent discoveries based on either catalytic or external physical field-stimulated micromotor swarms are also presented. Then, the strategy for the reconstruction and motion control of micromotor swarms in complex environments, including narrow channels, maze, raised obstacles, and high steps/low gaps, is summarized. Finally, we outline the future directions of micromotor swarms and the remaining challenges and opportunities. Full article

(This article belongs to the Special Issue Advances in Micro-/Nanorobotics)

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Graphical abstract

11 pages, 3509 KiB

Open AccessArticle

Improved Short-Circuit Current and Fill Factor in PM6:Y6 Organic Solar Cells through D18-Cl Doping

by Jianjun Yang, Xiansheng Wang, Xiaobao Yu, Jiaxuan Liu, Zhi Zhang, Jian Zhong and Junsheng Yu

Nanomaterials 2023, 13(21), 2899; https://doi.org/10.3390/nano13212899 - 3 Nov 2023

Cited by 2 | Viewed by 2353

Abstract

Based on the PM6:Y6 binary system, a novel non-fullerene acceptor material, D18-Cl, was doped into the PM6:Y6 blend to fabricate the active layer. The effects of different doping ratios of D18-Cl on organic solar cells were investigated. The best-performing organic solar cell was [...] Read more.

Based on the PM6:Y6 binary system, a novel non-fullerene acceptor material, D18-Cl, was doped into the PM6:Y6 blend to fabricate the active layer. The effects of different doping ratios of D18-Cl on organic solar cells were investigated. The best-performing organic solar cell was achieved when the doping ratio of D18-Cl reached 20 wt%. It exhibited a short-circuit current of 28.13 mA/cm², a fill factor of 70.25%, an open-circuit voltage (Voc) of 0.81 V, and a power conversion efficiency of 16.08%. The introduction of an appropriate amount of D18-Cl expanded the absorption spectrum of the active layer, improved the morphology of the active layer, reduced large molecular aggregation and defects, minimized bimolecular recombination, and optimized the collection efficiency of charge carriers. These results indicate the critical importance of selecting an appropriate third component in binary systems and optimizing the doping ratio to enhance the performance of ternary organic solar cells. Full article

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11 pages, 11824 KiB

Open AccessArticle

A Comparative Study of Gallium-, Xenon-, and Helium-Focused Ion Beams for the Milling of GaN

by Shuai Jiang and Volkan Ortalan

Nanomaterials 2023, 13(21), 2898; https://doi.org/10.3390/nano13212898 - 3 Nov 2023

Cited by 3 | Viewed by 1637

Abstract

The milling profiles of single-crystal gallium nitride (GaN) when subjected to focused ion beams (FIBs) using gallium (Ga), xenon (Xe), and helium (He) ion sources were investigated. An experimental analysis via annular dark-field scanning transmission electron microscopy (ADF-STEM) and high-resolution transmission electron microscopy [...] Read more.

The milling profiles of single-crystal gallium nitride (GaN) when subjected to focused ion beams (FIBs) using gallium (Ga), xenon (Xe), and helium (He) ion sources were investigated. An experimental analysis via annular dark-field scanning transmission electron microscopy (ADF-STEM) and high-resolution transmission electron microscopy (HRTEM) revealed that Ga-FIB milling yields trenches with higher aspect ratios compared to Xe-FIB milling for the selected ion beam parameters (30 kV, 42 pA), while He-FIB induces local lattice disorder. Molecular dynamics (MD) simulations were employed to investigate the milling process, confirming that probe size critically influences trench aspect ratios. Interestingly, the MD simulations also showed that Xe-FIB generates higher aspect ratios than Ga-FIB with the same probe size, indicating that Xe-FIB could also be an effective option for nanoscale patterning. Atomic defects such as vacancies and interstitials in GaN from He-FIB milling were suggested by the MD simulations, supporting the lattice disorder observed via HRTEM. This combined experimental and simulation approach has enhanced our understanding of FIB milling dynamics and will benefit the fabrication of nanostructures via the FIB technique. Full article

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15 pages, 3936 KiB

Open AccessArticle

Magnetism and Thermal Transport of Exchange-Spring-Coupled La_2/3Sr_1/3MnO₃/La₂MnCoO₆ Superlattices with Perpendicular Magnetic Anisotropy

by Vitaly Bruchmann-Bamberg, Isabell Weimer, Vladimir Roddatis, Ulrich Ross, Leonard Schüler, Karen P. Stroh and Vasily Moshnyaga

Nanomaterials 2023, 13(21), 2897; https://doi.org/10.3390/nano13212897 - 3 Nov 2023

Cited by 1 | Viewed by 1081

Abstract

Superlattices (SLs) comprising layers of a soft ferromagnetic metal La_2/3Sr_1/3MnO₃ (LSMO) with in-plane (IP) magnetic easy axis and a hard ferromagnetic insulator La₂MnCoO₆ (LMCO, out-of-plane anisotropy) were grown on SrTiO₃ (100)(STO) substrates by a [...] Read more.

Superlattices (SLs) comprising layers of a soft ferromagnetic metal La_2/3Sr_1/3MnO₃ (LSMO) with in-plane (IP) magnetic easy axis and a hard ferromagnetic insulator La₂MnCoO₆ (LMCO, out-of-plane anisotropy) were grown on SrTiO₃ (100)(STO) substrates by a metalorganic aerosol deposition technique. Exchange spring magnetic (ESM) behavior between LSMO and LMCO, manifested by a spin reorientation transition of the LSMO layers towards perpendicular magnetic anisotropy below T_SR = 260 K, was observed. Further, 3ω measurements of the [(LMCO)₉/(LSMO)₉]₁₁/STO(100) superlattices revealed extremely low values of the cross-plane thermal conductivity κ(300 K) = 0.32 Wm⁻¹K⁻¹. Additionally, the thermal conductivity shows a peculiar dependence on the applied IP magnetic field, either decreasing or increasing in accordance with the magnetic disorder induced by ESM. Furthermore, both positive and negative magnetoresistance were observed in the SL in the respective temperature regions due to the formation of 90°-Néel domain walls within the ESM, when applying IP magnetic fields. The results are discussed in the framework of electronic contribution to thermal conductivity originating from the LSMO layers. Full article

(This article belongs to the Topic Advances in Functional Thin Films)

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12 pages, 2408 KiB

Open AccessArticle

Nanograss-Assembled NiCo₂S₄ as an Efficient Platinum-Free Counter Electrode for Dye-Sensitized Solar Cell

by Shada A. Alsharif

Nanomaterials 2023, 13(21), 2896; https://doi.org/10.3390/nano13212896 - 2 Nov 2023

Cited by 1 | Viewed by 1373

Abstract

Dye-sensitized solar cells (DSSCs) are often viewed as the potential future of photovoltaic systems and have garnered significant attention in solar energy research. In this groundbreaking research, we introduced a novel solvothermal method to fabricate a unique “grass-like” pattern on fluorine-doped tin oxide [...] Read more.

Dye-sensitized solar cells (DSSCs) are often viewed as the potential future of photovoltaic systems and have garnered significant attention in solar energy research. In this groundbreaking research, we introduced a novel solvothermal method to fabricate a unique “grass-like” pattern on fluorine-doped tin oxide glass (FTO), specifically designed for use as a counter electrode in dye-sensitized solar cell (DSSC) assemblies. Through rigorous structural and morphological evaluations, we ascertained the successful deposition of nickel cobalt sulfide (NCS) on the FTO surface, exhibiting the desired grass-like morphology. Electrocatalytic performance assessment of the developed NCS-1 showed results that intriguingly rivaled those of the acclaimed platinum catalyst, especially during the conversion of I₃ to I⁻ as observed through cyclic voltammetry. Remarkably, when integrated into a solar cell assembly, both NCS-1 and NCS-2 electrodes exhibited encouraging power conversion efficiencies of 6.60% and 6.29%, respectively. These results become particularly noteworthy when compared to the 7.19% efficiency of a conventional Pt-based electrode under similar testing conditions. Central to the performance of the NCS-1 and NCS-2 electrodes is their unique thin and sharp grass-like morphology. This structure, vividly showcased through scanning electron microscopy, provides a vast surface area and an abundance of catalytic sites, pivotal for the catalytic reactions involving the electrolytes in DSSCs. In summation, given their innovative synthesis approach, affordability, and remarkable electrocatalytic attributes, the newly developed NCS counter electrodes stand out as potent contenders in future dye-sensitized solar cell applications. Full article

(This article belongs to the Special Issue Nanomaterials for Energy Applications: Materials Synthesis, Device Fabrication, and Characterization)

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9 pages, 1826 KiB

Open AccessArticle

Design and Fabrication of High Performance InGaAs near Infrared Photodetector

by Hezhuang Liu, Jingyi Wang, Daqian Guo, Kai Shen, Baile Chen and Jiang Wu

Nanomaterials 2023, 13(21), 2895; https://doi.org/10.3390/nano13212895 - 1 Nov 2023

Cited by 6 | Viewed by 3444

Abstract

InGaAs photodiodes have a wide range of important applications; for example, NIR imaging, fiber optical communication, and spectroscopy. In this paper, we studied InGaAs photodiodes with different doping concentration absorber layers. The simulated results suggested that, by reducing the absorber doping concentration from [...] Read more.

InGaAs photodiodes have a wide range of important applications; for example, NIR imaging, fiber optical communication, and spectroscopy. In this paper, we studied InGaAs photodiodes with different doping concentration absorber layers. The simulated results suggested that, by reducing the absorber doping concentration from 1 × 10¹⁶ to 1 × 10¹⁵ cm⁻³, the maximum quantum efficiency of the devices can rise by 1.2%, to 58%. The simulation also showed that, by increasing the doping concentration of the absorber layer within a certain range, the dark current of the device can be slightly reduced. A PIN structure was grown and fabricated, and CV measurements suggested a low doping concentration of about 1.2 × 10¹⁵ cm⁻³. Although the thermal activation energy of the dark current suggested a distinct component of shunt dark current at a high temperature range, a dark current of ~6 × 10⁻⁴ A/cm² (−0.5 V) was measured at room temperature. The peak quantum efficiency of the InGaAs device was characterized as 54.7% without antireflection coating and 80.2% with antireflection coating. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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15 pages, 16131 KiB

Open AccessArticle

Green Synthesis and Morphological Evolution for Bi₂Te₃ Nanosystems via a PVP-Assisted Hydrothermal Method

by Fang Zhou, Weichang Zhou, Yujing Zhao and Li Liu

Nanomaterials 2023, 13(21), 2894; https://doi.org/10.3390/nano13212894 - 1 Nov 2023

Cited by 1 | Viewed by 1599

Abstract

Bi

_{2}

Te

_{3}

has been extensively used because of its excellent thermoelectric properties at room temperature. Here, 230–420 nm of Bi

_{2}

Te

_{3}

hexagonal nanosheets has been successfully synthesized via a “green” method by using ethylene glycol solution and applying polyvinyl [...] Read more.

Bi

_{2}

Te

_{3}

has been extensively used because of its excellent thermoelectric properties at room temperature. Here, 230–420 nm of Bi

_{2}

Te

_{3}

hexagonal nanosheets has been successfully synthesized via a “green” method by using ethylene glycol solution and applying polyvinyl pyrrolidone (PVP) as a surfactant. In addition, factors influencing morphological evolution are discussed in detail in this study. Among these parameters, the reaction temperature, molar mass of NaOH, different surfactants, and reaction duration are considered as the most essential. The results show that the existence of PVP is vital to the formation of a plate-like morphology. The reaction temperature and alkaline surroundings played essential roles in the formation of Bi

_{2}

Te

_{3}

single crystals. By spark plasma sintering, the Bi

_{2}

Te

_{3}

hexagonal nanosheets were hot pressed into solid-state samples. We also studied the transport properties of solid-state samples. The electrical conductivity

σ

was 18.5 × 10

^{3}

Sm

^{- 1}

to 28.69 × 10

^{3}

Sm

^{- 1}

, and the Seebeck coefficient S was −90.4 to −113.3 µVK

^{- 1}

over a temperature range of 300–550 K. In conclusion, the observation above could serve as a catalyst for future exploration into photocatalysis, solar cells, nonlinear optics, thermoelectric generators, and ultraviolet selective photodetectors of Bi

_{2}

Te

_{3}

nanosheet-based photodetectors. Full article

(This article belongs to the Special Issue Nanomaterial-Based Nano-Electronic and Photonic Devices)

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15 pages, 5491 KiB

Open AccessArticle

An Investigation on the Use of Au@SiO₂@Au Nanomatryoshkas as Gap-Enhanced Raman Tags

by Brinton King Eldridge, Saghar Gomrok, James W. Barr, Elise Anne Chaffin, Lauren Fielding, Christian Sachs, Katie Stickels, Paiton Williams and Yongmei Wang

Nanomaterials 2023, 13(21), 2893; https://doi.org/10.3390/nano13212893 - 1 Nov 2023

Cited by 1 | Viewed by 1603

Abstract

Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. [...] Read more.

Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. Even though placing Raman molecules beneath an Au shell seems counter-intuitive, it has been shown that such systems produce a stronger surface-enhanced Raman scattering response due to the strong electric field inside the gap. While the theoretical support of the stronger electric field inside the gap was provided in the literature, a comprehensive understanding of how the electric field inside the gap compares with that of the outer surface of the particle was not readily available. We investigated Au@SiO

_{2}

@Au nanoparticles with diameters ranging from 35 nm to 70 nm with varying shell (2.5–10 nm) and gap (2.5–15 nm) thicknesses and obtained both far-field and near-field spectra. The extinction spectra from these particles always have two peaks. The low-energy peak redshifts with the decreasing shell thickness. However, when the gap thickness decreases, the low-energy peaks first blueshift and then redshift, producing a C-shape in the peak position. For every system we investigated, the near-field enhancement spectra were stronger inside the gap than on the outer surface of the nanoparticle. We find that a thin shell combined with a thin gap will produce the greatest near-field enhancement inside the gap. Our work fills the knowledge gap between the exciting potential applications of gap-enhanced Raman tags and the fundamental knowledge of enhancement provided by the gap. Full article

(This article belongs to the Topic Optical and Optoelectronic Properties of Materials and Their Applications)

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13 pages, 3945 KiB

Open AccessArticle

Temperature- and Size-Dependent Photoluminescence of CuInS₂ Quantum Dots

by Oleg Korepanov, Dmitriy Kozodaev, Olga Aleksandrova, Alexander Bugrov, Dmitrii Firsov, Demid Kirilenko, Dmitriy Mazing, Vyacheslav Moshnikov and Zamir Shomakhov

Nanomaterials 2023, 13(21), 2892; https://doi.org/10.3390/nano13212892 - 1 Nov 2023

Cited by 4 | Viewed by 2519

Abstract

We present the results of a temperature-dependent photoluminescence (PL) spectroscopy study on CuInS₂ quantum dots (QDs). In order to elucidate the influence of QD size on PL temperature dependence, size-selective precipitation was used to obtain several nanoparticle fractions. Additionally, the nanoparticles’ morphology [...] Read more.

We present the results of a temperature-dependent photoluminescence (PL) spectroscopy study on CuInS₂ quantum dots (QDs). In order to elucidate the influence of QD size on PL temperature dependence, size-selective precipitation was used to obtain several nanoparticle fractions. Additionally, the nanoparticles’ morphology and chemical composition were studied using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The obtained QDs showed luminescence in the visible–near infrared range. The PL energy, linewidth, and intensity were studied within an 11–300 K interval. For all fractions, a temperature decrease led to a shift in the emission maximum to higher energies and pronounced growth of the PL intensity down to 75–100 K. It was found that for large particle fractions, the PL intensity started to decrease, with temperature decreasing below 75 K, while the PL intensity of small nanoparticles remained stable. Full article

(This article belongs to the Special Issue Semiconductor Quantum Dots: Synthesis, Properties and Applications)

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6 pages, 230 KiB

Open AccessEditorial

Nanofibers and Nanotextured Materials: Design Insights, Bactericidal Mechanisms and Environmental Advances

by Touseef Amna and M. Shamshi Hassan

Nanomaterials 2023, 13(21), 2891; https://doi.org/10.3390/nano13212891 - 31 Oct 2023

Cited by 1 | Viewed by 1325

Abstract

Antibiotic resistance is rising and poses a serious threat to human health on a worldwide scale. It can make it more difficult to cure common infections, raise medical expenditures, and increase mortality. In order to combat the development of biofilms and treat fatal [...] Read more.

Antibiotic resistance is rising and poses a serious threat to human health on a worldwide scale. It can make it more difficult to cure common infections, raise medical expenditures, and increase mortality. In order to combat the development of biofilms and treat fatal bacterial infections, multifunctional polymeric nanofibers or nanotextured materials with specific structural features and special physiochemical capabilities have become a crucial tool. Due to the increased antibiotic resistance of many diseases, nanofibers with antibacterial activity are essential. Electrospinning is a flexible process able to produce fine fibers with specified properties by modifying variables such as the concentration of the solution, the feed flow, and the electric voltage. Substantial advancements have been made regarding the formation of nanofibers or nanotextured materials for a variety of applications, along with the development of electrospinning techniques in recent years. Using well-defined antimicrobial nanoparticles, encapsulating traditional therapeutic agents, plant-based bioactive agents, and pure compounds in polymer nanofibers has resulted in outstanding antimicrobial activity and has aided in curing deadly microbial infections. A plethora of studies have revealed that electrospinning is an effective technique for the production of antimicrobial fibers for the environmental, biomedical, pharmaceutical, and food sectors. Nevertheless, numerous studies have also demonstrated that the surface characteristics of substrates, such as holes, fibers, and ridges at the nanoscale, have an impact on cell proliferation, adhesion, and orientation. Full article

(This article belongs to the Special Issue Prospects of Bioinspired and Biomimetic Materials)

14 pages, 2650 KiB

Open AccessFeature PaperArticle

Si₃C Monolayer as an Efficient Metal-Free Catalyst for Nitrate Electrochemical Reduction: A Computational Study

by Wanying Guo, Tiantian Zhao, Fengyu Li, Qinghai Cai and Jingxiang Zhao

Nanomaterials 2023, 13(21), 2890; https://doi.org/10.3390/nano13212890 - 31 Oct 2023

Cited by 4 | Viewed by 1437

Abstract

Nitrate electroreduction reaction to ammonia (NO₃ER) holds great promise for both nitrogen pollution removal and valuable ammonia synthesis, which are still dependent on transition-metal-based catalysts at present. However, metal-free catalysts with multiple advantages for such processes have been rarely reported. Herein, [...] Read more.

Nitrate electroreduction reaction to ammonia (NO₃ER) holds great promise for both nitrogen pollution removal and valuable ammonia synthesis, which are still dependent on transition-metal-based catalysts at present. However, metal-free catalysts with multiple advantages for such processes have been rarely reported. Herein, by means of density functional theory (DFT) computations, in which the Perdew–Burke–Ernzerhof (PBE) functional is obtained by considering the possible van der Waals (vdW) interaction using the DFT+D3 method, we explored the potential of several two-dimensional (2D) silicon carbide monolayers as metal-free NO₃ER catalysts. Our results revealed that the excellent synergistic effect between the three Si active sites within the Si₃C monolayer enables the sufficient activation of NO₃⁻ and promotes its further hydrogenation into NO₂^*, NO^*, and NH₃, making the Si₃C monolayer exhibit high NO₃ER activity with a low limiting potential of −0.43 V. In particular, such an electrochemical process is highly dependent on the pH value of the electrolytes, in which acidic conditions are more favorable for NO₃ER. Moreover, ab initio molecular dynamics (AIMD) simulations demonstrated the high stability of the Si₃C monolayer. In addition, the Si₃C monolayer shows a low formation energy, excellent electronic properties, a superior suppression effect on competing reactions, and high stability, offering significant advantages for its experimental synthesis and practical applications in electrocatalysis. Thus, a Si₃C monolayer can perform as a promising NO₃ER catalyst, which would open a new avenue to further develop novel metal-free catalysts for NO₃ER. Full article

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

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30 pages, 8493 KiB

Open AccessReview

Selected I-III-VI₂ Semiconductors: Synthesis, Properties and Applications in Photovoltaic Cells

by Shubham Shishodia, Bilel Chouchene, Thomas Gries and Raphaël Schneider

Nanomaterials 2023, 13(21), 2889; https://doi.org/10.3390/nano13212889 - 31 Oct 2023

Cited by 5 | Viewed by 2869

Abstract

I–III–VI₂ group quantum dots (QDs) have attracted high attention in photoelectronic conversion applications, especially for QD-sensitized solar cells (QDSSCs). This group of QDs has become the mainstream light-harvesting material in QDSSCs due to the ability to tune their electronic properties through size, [...] Read more.

I–III–VI₂ group quantum dots (QDs) have attracted high attention in photoelectronic conversion applications, especially for QD-sensitized solar cells (QDSSCs). This group of QDs has become the mainstream light-harvesting material in QDSSCs due to the ability to tune their electronic properties through size, shape, and composition and the ability to assemble the nanocrystals on the surface of TiO₂. Moreover, these nanocrystals can be produced relatively easily via cost-effective solution-based synthetic methods and are composed of low-toxicity elements, which favors their integration into the market. This review describes the methods developed to prepare I-III-VI₂ QDs (AgInS₂ and CuInS₂ were excluded) and control their optoelectronic properties to favor their integration into QDSSCs. Strategies developed to broaden the optoelectronic response and decrease the surface-defect states of QDs in order to promote the fast electron injection from QDs into TiO₂ and achieve highly efficient QDSSCs will be described. Results show that heterostructures obtained after the sensitization of TiO₂ with I-III-VI₂ QDs could outperform those of other QDSSCs. The highest power-conversion efficiency (15.2%) was obtained for quinary Cu-In-Zn-Se-S QDs, along with a short-circuit density (J_SC) of 26.30 mA·cm⁻², an open-circuit voltage (V_OC) of 802 mV and a fill factor (FF) of 71%. Full article

(This article belongs to the Section Solar Energy and Solar Cells)

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4 pages, 836 KiB

Open AccessCorrection

Correction: Bischoff et al. The Effects of the Food Additive Titanium Dioxide (E171) on Tumor Formation and Gene Expression in the Colon of a Transgenic Mouse Model for Colorectal Cancer. Nanomaterials 2022, 12, 1256

by Nicolaj S. Bischoff, Héloïse Proquin, Marlon J. Jetten, Yannick Schrooders, Marloes C. M. Jonkhout, Jacco J. Briedé, Simone G. van Breda, Danyel G. J. Jennen, Estefany I. Medina-Reyes, Norma L. Delgado-Buenrostro, Yolanda I. Chirino, Henk van Loveren and Theo M. de Kok

Nanomaterials 2023, 13(21), 2888; https://doi.org/10.3390/nano13212888 - 31 Oct 2023

Viewed by 1134

Abstract

In the published publication [...] Full article

(This article belongs to the Section Biology and Medicines)

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28 pages, 19877 KiB

Open AccessReview

Application of Nanoparticles in Cancer Treatment: A Concise Review

by Mariana Sell, Ana Rita Lopes, Maria Escudeiro, Bruno Esteves, Ana R. Monteiro, Tito Trindade and Luísa Cruz-Lopes

Nanomaterials 2023, 13(21), 2887; https://doi.org/10.3390/nano13212887 - 31 Oct 2023

Cited by 13 | Viewed by 7916

Abstract

Timely diagnosis and appropriate antitumoral treatments remain of utmost importance, since cancer remains a leading cause of death worldwide. Within this context, nanotechnology offers specific benefits in terms of cancer therapy by reducing its adverse effects and guiding drugs to selectively target cancer [...] Read more.

Timely diagnosis and appropriate antitumoral treatments remain of utmost importance, since cancer remains a leading cause of death worldwide. Within this context, nanotechnology offers specific benefits in terms of cancer therapy by reducing its adverse effects and guiding drugs to selectively target cancer cells. In this comprehensive review, we have summarized the most relevant novel outcomes in the range of 2010–2023, covering the design and application of nanosystems for cancer therapy. We have established the general requirements for nanoparticles to be used in drug delivery and strategies for their uptake in tumor microenvironment and vasculature, including the reticuloendothelial system uptake and surface functionalization with protein corona. After a brief review of the classes of nanovectors, we have covered different classes of nanoparticles used in cancer therapies. First, the advances in the encapsulation of drugs (such as paclitaxel and fisetin) into nanoliposomes and nanoemulsions are described, as well as their relevance in current clinical trials. Then, polymeric nanoparticles are presented, namely the ones comprising poly lactic-co-glycolic acid, polyethylene glycol (and PEG dilemma) and dendrimers. The relevance of quantum dots in bioimaging is also covered, namely the systems with zinc sulfide and indium phosphide. Afterwards, we have reviewed gold nanoparticles (spheres and anisotropic) and their application in plasmon-induced photothermal therapy. The clinical relevance of iron oxide nanoparticles, such as magnetite and maghemite, has been analyzed in different fields, namely for magnetic resonance imaging, immunotherapy, hyperthermia, and drug delivery. Lastly, we have covered the recent advances in the systems using carbon nanomaterials, namely graphene oxide, carbon nanotubes, fullerenes, and carbon dots. Finally, we have compared the strategies of passive and active targeting of nanoparticles and their relevance in cancer theranostics. This review aims to be a (nano)mark on the ongoing journey towards realizing the remarkable potential of different nanoparticles in the realm of cancer therapeutics. Full article

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13 pages, 4648 KiB

Open AccessEditor’s ChoiceArticle

Monolithic Integration of Semi-Transparent and Flexible Integrated Image Sensor Array with a-IGZO Thin-Film Transistors (TFTs) and p-i-n Hydrogenated Amorphous Silicon Photodiodes

by Donghyeong Choi, Ji-Woo Seo, Jongwon Yoon, Seung Min Yu, Jung-Dae Kwon, Seoung-Ki Lee and Yonghun Kim

Nanomaterials 2023, 13(21), 2886; https://doi.org/10.3390/nano13212886 - 31 Oct 2023

Viewed by 2259

Abstract

A novel approach to fabricating a transparent and flexible one-transistor–one-diode (1T-1D) image sensor array on a flexible colorless polyimide (CPI) film substrate is successfully demonstrated with laser lift-off (LLO) techniques. Leveraging transparent indium tin oxide (ITO) electrodes and amorphous indium gallium zinc oxide [...] Read more.

A novel approach to fabricating a transparent and flexible one-transistor–one-diode (1T-1D) image sensor array on a flexible colorless polyimide (CPI) film substrate is successfully demonstrated with laser lift-off (LLO) techniques. Leveraging transparent indium tin oxide (ITO) electrodes and amorphous indium gallium zinc oxide (a-IGZO) channel-based thin-film transistor (TFT) backplanes, vertically stacked p-i-n hydrogenated amorphous silicon (a-Si:H) photodiodes (PDs) utilizing a low-temperature (<90 °C) deposition process are integrated with a densely packed 14 × 14 pixel array. The low-temperature-processed a-Si:H photodiodes show reasonable performance with responsivity and detectivity for 31.43 mA/W and 3.0 × 10¹⁰ Jones (biased at −1 V) at a wavelength of 470 nm, respectively. The good mechanical durability and robustness of the flexible image sensor arrays enable them to be attached to a curved surface with bending radii of 20, 15, 10, and 5 mm and 1000 bending cycles, respectively. These studies show the significant promise of utilizing highly flexible and rollable active-matrix technology for the purpose of dynamically sensing optical signals in spatial applications. Full article

(This article belongs to the Special Issue Low-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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14 pages, 5070 KiB

Open AccessArticle

Polycation-Intercalated MXene Membrane with Enhanced Permselective and Anti-Microbial Properties

by Jie Yang, Shilin Zhu and Hongli Zhang

Nanomaterials 2023, 13(21), 2885; https://doi.org/10.3390/nano13212885 - 31 Oct 2023

Cited by 4 | Viewed by 1772

Abstract

Two-dimensional (2D) nanomaterial-based membranes feature attractive properties for molecular separation and transport, which exhibit huge potential in various chemical processes. However, the low permeability and bio-fouling of the MXene membrane in water treatment become huge obstacles to its practical application. Herein, a highly [...] Read more.

Two-dimensional (2D) nanomaterial-based membranes feature attractive properties for molecular separation and transport, which exhibit huge potential in various chemical processes. However, the low permeability and bio-fouling of the MXene membrane in water treatment become huge obstacles to its practical application. Herein, a highly permselective and anti-bacterial 2D nanofiltration membrane is fabricated by intercalating a polycation of polydiallyldimethylammonium chloride (PDDA) into the Ti₃C₂T_x MXene laminar architecture through a facile and patternable electrostatic assembly strategy. As a result, the as-fabricated Ti₃C₂T_x/PDDA composite membrane exhibits higher water permeance up to 73.4 L m⁻² h⁻¹ with a rejection above 94.6% for MgCl₂. The resultant membrane simultaneously possesses good resistance to swelling and long-term stability in water environments, even after 8 h. Additionally, the Ti₃C₂T_x/PDDA membrane also demonstrates a high flux recovery ratio of nearly 96.1% to bovine serum albumin proteins after being cleaned. More importantly, the current membrane shows excellent anti-adhesive and anti-microbial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), with inhibition rates of 90% and 95% against E. coli and S. aureus, respectively. This holds great potential for the application of the polyelectrolyte-intercalated MXene membrane in serving as a promising platform to separate molecules and/or ions in an aquatic environment. Full article

(This article belongs to the Special Issue Two-Dimensional Materials Membrane and Adsorbent for Wastewater Treatment)

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9 pages, 2141 KiB

Open AccessArticle

Nanotribological Characteristics of the Al Content of Al_xGa_1−xN Epitaxial Films

by Hua-Chiang Wen, Ssu-Kuan Wu, Cheng-Wei Liu, Jin-Ji Dai and Wu-Ching Chou

Nanomaterials 2023, 13(21), 2884; https://doi.org/10.3390/nano13212884 - 31 Oct 2023

Viewed by 1003

Abstract

The nanotribological properties of aluminum gallium nitride (Al_xGa_1−xN) epitaxial films grown on low-temperature-grown GaN/AlN/Si substrates were investigated using a nanoscratch system. It was confirmed that the Al compositions played an important role, which was directly influencing the strength of [...] Read more.

The nanotribological properties of aluminum gallium nitride (Al_xGa_1−xN) epitaxial films grown on low-temperature-grown GaN/AlN/Si substrates were investigated using a nanoscratch system. It was confirmed that the Al compositions played an important role, which was directly influencing the strength of the bonding forces and the shear resistance. It was verified that the measured friction coefficient (μ) values of the Al_xGa_1−xN films from the Al compositions (where x = 0.065, 0.085, and 0.137) were in the range of 0.8, 0.5, and 0.3, respectively, for Fn = 2000 μN and 0.12, 0.9, and 0.7, respectively, for Fn = 4000 μN. The values of μ were found to decrease with the increases in the Al compositions. We concluded that the Al composition played an important role in the reconstruction of the crystallites, which induced the transition phenomenon of brittleness to ductility in the Al_xGa_1−xN system. Full article

(This article belongs to the Special Issue Thermophysical and Tribological Properties of Nanomaterials)

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20 pages, 13168 KiB

Open AccessArticle

Peat-Derived ZnCl₂-Activated Ultramicroporous Carbon Materials for Hydrogen Adsorption

by Egert Möller, Rasmus Palm, Kenneth Tuul, Meelis Härmas, Miriam Koppel, Jaan Aruväli, Marian Külaviir and Enn Lust

Nanomaterials 2023, 13(21), 2883; https://doi.org/10.3390/nano13212883 - 31 Oct 2023

Viewed by 1918

Abstract

Highly microporous adsorbents have been under considerable scrutiny for efficient adsorptive storage of H₂. Of specific interest are sustainable, chemically activated, microporous carbon adsorbents, especially from renewable and organic precursor materials. In this article, six peat-derived microporous carbon materials were synthesized [...] Read more.

Highly microporous adsorbents have been under considerable scrutiny for efficient adsorptive storage of H₂. Of specific interest are sustainable, chemically activated, microporous carbon adsorbents, especially from renewable and organic precursor materials. In this article, six peat-derived microporous carbon materials were synthesized by chemical activation with ZnCl₂. N₂ and CO₂ gas adsorption data were measured and simultaneously fitted with the 2D-NLDFT-HS model. Thus, based on the obtained results, the use of a low ratio of ZnCl₂ for chemical activation of peat-derived carbon yields highly ultramicroporous carbons which are able to adsorb up to 83% of the maximal adsorbed amount of adsorbed H₂ already at 1 bar at 77 K. This is accompanied by the high ratio of micropores, 99%, even at high specific surface area of 1260 m² g⁻¹, exhibited by the peat-derived carbon activated at 973 K using a 1:2 ZnCl₂ to peat mass ratio. These results show the potential of using low concentrations of ZnCl₂ as an activating agent to synthesize highly ultramicroporous carbon materials with suitable pore characteristics for the efficient low-pressure adsorption of H₂. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Gas Capture, Separation and Storage)

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10 pages, 652 KiB

Open AccessArticle

Mesoscopic Conductance Fluctuations in 2D HgTe Semimetal

by Daniiar Khudaiberdiev, Ze Don Kvon, Matvey V. Entin, Dmitriy A. Kozlov, Nikolay N. Mikhailov and Maxim Ryzhkov

Nanomaterials 2023, 13(21), 2882; https://doi.org/10.3390/nano13212882 - 31 Oct 2023

Cited by 1 | Viewed by 1435

Abstract

Mesoscopic conductance fluctuations were discovered in a weak localization regime of a strongly disordered two-dimensional HgTe-based semimetal. These fluctuations exist in macroscopic samples with characteristic sizes of 100

μ

m and exhibit anomalous dependences on the gate voltage, magnetic field, and temperature. They [...] Read more.

Mesoscopic conductance fluctuations were discovered in a weak localization regime of a strongly disordered two-dimensional HgTe-based semimetal. These fluctuations exist in macroscopic samples with characteristic sizes of 100

μ

m and exhibit anomalous dependences on the gate voltage, magnetic field, and temperature. They are absent in the regime of electron metal (at positive gate voltages) and strongly depend on the level of disorder in the system. All the experimental facts lead us to the conclusion that the origin of the fluctuations is a special collective state in which the current is conducted through the percolation network of electron resistances. We suppose that the network is formed by fluctuation potential whose amplitude is higher than the Fermi level of electrons due to their very low density. Full article

(This article belongs to the Special Issue Electron Transport and Electronic Properties in Low-Dimensional Materials)

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18 pages, 66694 KiB

Open AccessReview

Emerging Characteristics and Properties of Moiré Materials

by Shaofeng Wang, Jizhe Song, Mengtao Sun and Shuo Cao

Nanomaterials 2023, 13(21), 2881; https://doi.org/10.3390/nano13212881 - 30 Oct 2023

Cited by 2 | Viewed by 2132

Abstract

In recent years, scientists have conducted extensive research on Moiré materials and have discovered some compelling properties. The Moiré superlattice allows superconductivity through flat-band and strong correlation effects. The presence of flat bands causes the Moiré material to exhibit topological properties as well. [...] Read more.

In recent years, scientists have conducted extensive research on Moiré materials and have discovered some compelling properties. The Moiré superlattice allows superconductivity through flat-band and strong correlation effects. The presence of flat bands causes the Moiré material to exhibit topological properties as well. Modulating electronic interactions with magnetic fields in Moiré materials enables the fractional quantum Hall effect. In addition, Moiré materials have ferromagnetic and antiferromagnetic properties. By tuning the interlayer coupling and spin interactions of the Moiré superlattice, different magnetic properties can be achieved. Finally, this review also discusses the applications of Moiré materials in the fields of photocurrent, superconductivity, and thermoelectricity. Overall, Moiré superlattices provide a new dimension in the development of two-dimensional materials. Full article

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58 pages, 19582 KiB

Open AccessReview

Recent Advances of Graphene Quantum Dots in Chemiresistive Gas Sensors

by Xiaofeng Zhu, Yongzhen Li, Pei Cao, Peng Li, Xinzhu Xing, Yue Yu, Ruihua Guo and Hui Yang

Nanomaterials 2023, 13(21), 2880; https://doi.org/10.3390/nano13212880 - 30 Oct 2023

Cited by 3 | Viewed by 2141

Abstract

Graphene quantum dots (GQDs), as 0D graphene nanomaterials, have aroused increasing interest in chemiresistive gas sensors owing to their remarkable physicochemical properties and tunable electronic structures. Research on GQDs has been booming over the past decades, and a number of excellent review articles [...] Read more.

Graphene quantum dots (GQDs), as 0D graphene nanomaterials, have aroused increasing interest in chemiresistive gas sensors owing to their remarkable physicochemical properties and tunable electronic structures. Research on GQDs has been booming over the past decades, and a number of excellent review articles have been provided on various other sensing principles of GQDs, such as fluorescence-based ion-sensing, bio-sensing, bio-imaging, and electrochemical, photoelectrochemical, and electrochemiluminescence sensing, and therapeutic, energy and catalysis applications. However, so far, there is no single review article on the application of GQDs in the field of chemiresistive gas sensing. This is our primary inspiration for writing this review, with a focus on the chemiresistive gas sensors reported using GQD-based composites. In this review, the various synthesized strategies of GQDs and its composites, gas sensing enhancement mechanisms, and the resulting sensing characteristics are presented. Finally, the current challenges and future prospects of GQDs in the abovementioned application filed have been discussed for the more rational design of advanced GQDs-based gas-sensing materials and innovative gas sensors with novel functionalities. Full article

(This article belongs to the Special Issue Nanostructured Materials in Gas Sensing Applications)

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13 pages, 31318 KiB

Open AccessArticle

Influence of Different Carrier Gases, Temperature, and Partial Pressure on Growth Dynamics of Ge and Si Nanowires

by Nicolas Forrer, Arianna Nigro, Gerard Gadea and Ilaria Zardo

Nanomaterials 2023, 13(21), 2879; https://doi.org/10.3390/nano13212879 - 30 Oct 2023

Cited by 1 | Viewed by 1402

Abstract

The broad and fascinating properties of nanowires and their synthesis have attracted great attention as building blocks for functional devices at the nanoscale. Silicon and germanium are highly interesting materials due to their compatibility with standard CMOS technology. Their combination provides optimal templates [...] Read more.

The broad and fascinating properties of nanowires and their synthesis have attracted great attention as building blocks for functional devices at the nanoscale. Silicon and germanium are highly interesting materials due to their compatibility with standard CMOS technology. Their combination provides optimal templates for quantum applications, for which nanowires need to be of high quality, with carefully designed dimensions, crystal phase, and orientation. In this work, we present a detailed study on the growth kinetics of silicon (length 0.1–1

μ

m, diameter 10–60 nm) and germanium (length 0.06–1

μ

m, diameter 10–500 nm) nanowires grown by chemical vapor deposition applying the vapour–liquid–solid growth method catalysed by gold. The effects of temperature, partial pressure of the precursor gas, and different carrier gases are analysed via scanning electron microscopy. Argon as carrier gas enhances the growth rate at higher temperatures (120 nm/min for Ar and 48 nm/min H

_{2}

), while hydrogen enhances it at lower temperatures (35 nm/min for H

_{2}

and 22 nm/min for Ar) due to lower heat capacity. Both materials exhibit two growth regimes as a function of the temperature. The tapering rate is about ten times lower for silicon nanowires than for germanium ones. Finally, we identify the optimal conditions for nucleation in the nanowire growth process. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires: 2nd Edition)

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