Nanomaterials

28 pages, 9745 KiB

Open AccessReview

Graphene-Based Cathode Materials for Lithium-Ion Capacitors: A Review

by Dong Sui, Meijia Chang, Zexin Peng, Changle Li, Xiaotong He, Yanliang Yang, Yong Liu and Yanhong Lu

Nanomaterials 2021, 11(10), 2771; https://doi.org/10.3390/nano11102771 - 19 Oct 2021

Cited by 20 | Viewed by 4331

Abstract

Lithium-ion capacitors (LICs) are attracting increasing attention because of their potential to bridge the electrochemical performance gap between batteries and supercapacitors. However, the commercial application of current LICs is still impeded by their inferior energy density, which is mainly due to the low [...] Read more.

Lithium-ion capacitors (LICs) are attracting increasing attention because of their potential to bridge the electrochemical performance gap between batteries and supercapacitors. However, the commercial application of current LICs is still impeded by their inferior energy density, which is mainly due to the low capacity of the cathode. Therefore, tremendous efforts have been made in developing novel cathode materials with high capacity and excellent rate capability. Graphene-based nanomaterials have been recognized as one of the most promising cathodes for LICs due to their unique properties, and exciting progress has been achieved. Herein, in this review, the recent advances of graphene-based cathode materials for LICs are systematically summarized. Especially, the synthesis method, structure characterization and electrochemical performance of various graphene-based cathodes are comprehensively discussed and compared. Furthermore, their merits and limitations are also emphasized. Finally, a summary and outlook are presented to highlight some challenges of graphene-based cathode materials in the future applications of LICs. Full article

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15 pages, 3950 KiB

Open AccessFeature PaperArticle

Highly Sensitive and Stable Copper-Based SERS Chips Prepared by a Chemical Reduction Method

by Pei Dai, Haochen Li, Xianzhi Huang, Nan Wang and Lihua Zhu

Nanomaterials 2021, 11(10), 2770; https://doi.org/10.3390/nano11102770 - 19 Oct 2021

Cited by 21 | Viewed by 3020

Abstract

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction [...] Read more.

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction method. In the preparation process, Cu NPs were densely deposited onto fabric supports. The as-prepared Cu-coated fabric was hydrophobic with fairly good SERS performance. The Cu-coated fabric was able to be used as a SERS chip to detect crystal violet, and it exhibited an enhancement factor of 2.0 × 106 and gave a limit of detection (LOD) as low as 10–8 M. The hydrophobicity of the Cu membrane on the fabric is favorable to cleaning background interference signals and promoting the stability of Cu NPs to environment oxidation. However, this Cu SERS chip was still poor in its long-term stability. The SERS intensity on the chip was decreased to 18% of the original one after it was stored in air for 60 days. A simple introduction of Ag onto the clean Cu surface was achieved by a replacement reaction to further enhance the SERS performances of the Cu chips. The Ag-modified Cu chips showed an increase of the enhancement factor to 7.6 × 106 due to the plasmonic coupling between Cu and Ag in nanoscale, and decreased the LOD of CV to 10–11 M by three orders of magnitude. Owing to the additional protection of Ag shell, the SERS intensity of the Cu-Ag chip after a two-month storing maintained 80% of the original intensity. The Cu-Ag SERS chips were also applied to detect other organics, and showing wide linearity range and low LOD values for the quantitative detection. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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12 pages, 2508 KiB

Open AccessArticle

Enhanced Bioaccumulation and Toxicity of Arsenic in Marine Mussel Perna viridis in the Presence of CuO/Fe₃O₄ Nanoparticles

by Shuang Zhou, Wei Qian, Zigong Ning and Xiaoshan Zhu

Nanomaterials 2021, 11(10), 2769; https://doi.org/10.3390/nano11102769 - 19 Oct 2021

Cited by 2 | Viewed by 2070

Abstract

Leakage of metal oxide nanoparticles (MNPs) into marine environments is inevitable with the increasing use of MNPs. However, little is known about the effects of these lately emerged MNPs on the bioaccumulation and toxicity of pre-existing contaminants in marine biota. The current study [...] Read more.

Leakage of metal oxide nanoparticles (MNPs) into marine environments is inevitable with the increasing use of MNPs. However, little is known about the effects of these lately emerged MNPs on the bioaccumulation and toxicity of pre-existing contaminants in marine biota. The current study therefore investigated the effects of two common MNPs, CuO nanoparticles (nCuO) and Fe₃O₄ nanoparticles (nFe₃O₄), on bioaccumulation and toxicity of arsenic (As) in green mussel Perna viridis. Newly introduced MNPs remarkably promoted the accumulation of As and disrupted the As distribution in mussels because of the strong adsorption of As onto MNPs. Moreover, MNPs enhanced the toxicity of As by disturbing osmoregulation in mussels, which could be supported by decreased activity of Na⁺-K⁺-ATPase and average weight loss of mussels after MNPs exposure. In addition, the enhanced toxicity of As in mussels might be due to that MNPs reduced the biotransformation efficiency of more toxic inorganic As to less toxic organic As, showing an inhibitory effect on As detoxifying process of mussels. This could be further demonstrated by the overproduction of reactive oxygen species (ROS), as implied by the rise in quantities of superoxide dismutase (SOD) and lipid peroxidation (LPO), and subsequently restraining the glutathione-S-transferases (GST) activity and glutathione (GSH) content in mussels. Taken together, this study elucidated that MNPs may elevate As bioaccumulation and limit As biotransformation in mussels, which would result in an enhanced ecotoxicity of As towards marine organisms. Full article

(This article belongs to the Special Issue Nanomaterials Ecotoxicity Evaluation)

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22 pages, 3142 KiB

Open AccessEditor’s ChoiceArticle

NanoSafe III: A User Friendly Safety Management System for Nanomaterials in Laboratories and Small Facilities

by Elina Buitrago, Anna Maria Novello, Alke Fink, Michael Riediker, Barbara Rothen-Rutishauser and Thierry Meyer

Nanomaterials 2021, 11(10), 2768; https://doi.org/10.3390/nano11102768 - 19 Oct 2021

Cited by 9 | Viewed by 3854

Abstract

Research in nanoscience continues to bring forward a steady stream of new nanomaterials and processes that are being developed and marketed. While scientific committees and expert groups deal with the harmonization of terminology and legal challenges, risk assessors in research labs continue to [...] Read more.

Research in nanoscience continues to bring forward a steady stream of new nanomaterials and processes that are being developed and marketed. While scientific committees and expert groups deal with the harmonization of terminology and legal challenges, risk assessors in research labs continue to have to deal with the gap between regulations and rapidly developing information. The risk assessment of nanomaterial processes is currently slow and tedious because it is performed on a material-by-material basis. Safety data sheets are rarely available for (new) nanomaterials, and even when they are, they often lack nano-specific information. Exposure estimations or measurements are difficult to perform and require sophisticated and expensive equipment and personal expertise. The use of banding-based risk assessment tools for laboratory environments is an efficient way to evaluate the occupational risks associated with nanomaterials. Herein, we present an updated version of our risk assessment tool for working with nanomaterials based on a three-step control banding approach and the precautionary principle. The first step is to determine the hazard band of the nanomaterial. A decision tree allows the assignment of the material to one of three bands based on known or expected effects on human health. In the second step, the work exposure is evaluated and the processes are classified into three “nano” levels for each specific hazard band. The work exposure is estimated using a laboratory exposure model. The result of this calculation in combination with recommended occupational exposure limits (rOEL) for nanomaterials and an additional safety factor gives the final “nano” level. Finally, we update the technical, organizational, and personal protective measures to allow nanomaterial processes to be established in research environments. Full article

(This article belongs to the Special Issue Risk Analysis and Assessment of Nanomaterials)

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13 pages, 1567 KiB

Open AccessArticle

Mechanisms of Upconversion Luminescence of Er³⁺-Doped NaYF₄ via 980 and 1530 nm Excitation

by Yu Liu, Ziwen Zhou, Shaojian Zhang, Enming Zhao, Jing Ren, Lu Liu and Jianzhong Zhang

Nanomaterials 2021, 11(10), 2767; https://doi.org/10.3390/nano11102767 - 19 Oct 2021

Cited by 12 | Viewed by 2828

Abstract

To date, the mechanisms of Er³⁺ upconversion luminescence via 980 and 1530 nm excitation have been extensively investigated; however, based on discussions, they either suffer from the lack of convincing evidence or require elaborated and time-consuming numerical simulations. In this work, the [...] Read more.

To date, the mechanisms of Er³⁺ upconversion luminescence via 980 and 1530 nm excitation have been extensively investigated; however, based on discussions, they either suffer from the lack of convincing evidence or require elaborated and time-consuming numerical simulations. In this work, the steady-state and time-resolved upconversion luminescence data of Er³⁺-doped NaYF₄ were measured; we therefore investigated the upconversion mechanisms of Er³⁺ on the basis of the spectroscopic observations and the simplified rate equation modeling. This work provides a relatively simple strategy to reveal the UCL mechanisms of Er³⁺ upon excitation with various wavelengths, which may also be used in other lanthanide ion-doped systems. Full article

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20 pages, 7611 KiB

Open AccessArticle

Highly Stable Thin Films Based on Novel Hybrid 1D (PRSH)PbX₃ Pseudo-Perovskites

by Gabriele Calabrese, Candida Pipitone, Diego Marini, Francesco Giannici, Antonino Martorana, Luisa Barba, Caterina Summonte, Norberto Masciocchi and Silvia Milita

Nanomaterials 2021, 11(10), 2765; https://doi.org/10.3390/nano11102765 - 19 Oct 2021

Cited by 1 | Viewed by 2245

Abstract

In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX₃ (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films [...] Read more.

In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX₃ (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films are strongly crystalline already at room temperature, and annealing does not promote further crystallization or film reorganization. The film microstructure is found to be strongly influenced by the anion type and, to a lesser extent, by the DMF/DMSO solvent volume ratio used during film deposition by spin-coating. Comparison of specular X-ray diffraction and complementary grazing incidence X-ray diffraction analysis indicates that the use of DMF/DMSO mixed solvents promotes the strengthening of a dominant 100 or 210 texturing, as compared the case of pure DMF, and that the haloplumbate chains always lie in a plane parallel to the substrate. Under specific DMF/DMSO solvent volume ratios, the prepared films are found to be highly stable in time (up to seven months under fluxing N₂ and in the dark) and to highly moist conditions (up to 25 days at 78% relative humidity). Furthermore, for representative (PRSH)PbX₃ films, resistance against ultraviolet exposure (λ = 380 nm) is investigated, showing complete stability after irradiation for up to 15 h at a power density of 600 mW/cm². These results make such thin films interesting for highly stable perovskite-based (opto)electronic devices. Full article

(This article belongs to the Special Issue Total Scattering Based Characterization Techniques for Nanostructures)

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16 pages, 10093 KiB

Open AccessArticle

Using Dissipative Particle Dynamics to Model Effects of Chemical Reactions Occurring within Hydrogels

by Ya Liu, Joanna Aizenberg and Anna C. Balazs

Nanomaterials 2021, 11(10), 2764; https://doi.org/10.3390/nano11102764 - 19 Oct 2021

Cited by 5 | Viewed by 2362

Abstract

Computational models that reveal the structural response of polymer gels to changing, dissolved reactive chemical species would provide useful information about dynamically evolving environments. However, it remains challenging to devise one computational approach that can capture all the interconnected chemical events and responsive [...] Read more.

Computational models that reveal the structural response of polymer gels to changing, dissolved reactive chemical species would provide useful information about dynamically evolving environments. However, it remains challenging to devise one computational approach that can capture all the interconnected chemical events and responsive structural changes involved in this multi-stage, multi-component process. Here, we augment the dissipative particle dynamics (DPD) method to simulate the reaction of a gel with diffusing, dissolved chemicals to form kinetically stable complexes, which in turn cause concentration-dependent deformation of the gel. Using this model, we also examine how the addition of new chemical stimuli and subsequent reactions cause the gel to exhibit additional concentration-dependent structural changes. Through these DPD simulations, we show that the gel forms multiple latent states (not just the “on/off”) that indicate changes in the chemical composition of the fluidic environment. Hence, the gel can actuate a range of motion within the system, not just movements corresponding to the equilibrated swollen or collapsed states. Moreover, the system can be used as a sensor, since the structure of the layer effectively indicates the presence of chemical stimuli. Full article

(This article belongs to the Special Issue Advances in Computational Materials Science on Functional Interfaces and Surfaces)

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15 pages, 8023 KiB

Open AccessArticle

Self-Powered Acceleration Sensor Based on Multilayer Suspension Structure and TPU-RTV Film for Vibration Monitoring

by Xiaotao Han, Qiyuan Zhang, Junbin Yu, Jinsha Song, Zhengyang Li, Haoran Cui, Jian He, Xiujian Chou and Jiliang Mu

Nanomaterials 2021, 11(10), 2763; https://doi.org/10.3390/nano11102763 - 18 Oct 2021

Cited by 7 | Viewed by 2610

Abstract

In this paper, we designed a triboelectric acceleration sensor with excellent multiple parameters. To more easily detect weak vibrations, the sensor was founded on a multilayer suspension structure. To effectively improve the electrical properties of the sensor, a surface roughening and internal doping [...] Read more.

In this paper, we designed a triboelectric acceleration sensor with excellent multiple parameters. To more easily detect weak vibrations, the sensor was founded on a multilayer suspension structure. To effectively improve the electrical properties of the sensor, a surface roughening and internal doping friction film, which was refined with a room temperature vulcanized silicone rubber (RTV) and some thermoplastic polyurethanes (TPU) powder in a certain proportion, was integrated into the structure. It was found that the optimization of the RTV film increases the open circuit voltage and short circuit current of the triboelectric nanogenerator (TENG) by 223% and 227%, respectively. When the external vibration acceleration is less than 4 m/s², the sensitivity and linearity are 1.996 V/(m/s²) and 0.999, respectively. Additionally, when it is in the range between 4 m/s² and 15 m/s², those are 23.082 V/(m/s²) and 0.975, respectively. Furthermore, the sensor was placed in a simulated truck vibration environment, and its self-powered monitoring ability validated by experiments in real time. The results show that the designed sensor has strong practical value in the field of monitoring mechanical vibration acceleration. Full article

(This article belongs to the Special Issue Nanosensors)

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12 pages, 3736 KiB

Open AccessArticle

Construction of Chemically Bonded Interface of Organic/Inorganic g-C₃N₄/LDH Heterojunction for Z-Schematic Photocatalytic H₂ Generation

by Yuzhou Xia, Ruowen Liang, Min-Quan Yang, Shuying Zhu and Guiyang Yan

Nanomaterials 2021, 11(10), 2762; https://doi.org/10.3390/nano11102762 - 18 Oct 2021

Cited by 14 | Viewed by 2603

Abstract

The design and synthesis of a Z-schematic photocatalytic heterostructure with an intimate interface is of great significance for the migration and separation of photogenerated charge carriers, but still remains a challenge. Here, we developed an efficient Z-scheme organic/inorganic g-C₃N₄/LDH [...] Read more.

The design and synthesis of a Z-schematic photocatalytic heterostructure with an intimate interface is of great significance for the migration and separation of photogenerated charge carriers, but still remains a challenge. Here, we developed an efficient Z-scheme organic/inorganic g-C₃N₄/LDH heterojunction by in situ growing of inorganic CoAl-LDH firmly on organic g-C₃N₄ nanosheet (NS). Benefiting from the two-dimensional (2D) morphology and the surface exposed pyridine-like nitrogen atoms, the g-C₃N₄ NS offers efficient trap sits to capture transition metal ions. As such, CoAl-LDH NS can be tightly attached onto the g-C₃N₄ NS, forming a strong interaction between CoAl-LDH and g-C₃N₄ via nitrogen–metal bonds. Moreover, the 2D/2D interface provides a high-speed channel for the interfacial charge transfer. As a result, the prepared heterojunction composite exhibits a greatly improved photocatalytic H₂ evolution activity, as well as considerable stability. Under visible light irradiation of 4 h, the optimal H₂ evolution rate reaches 1952.9 μmol g⁻¹, which is 8.4 times of the bare g-C₃N₄ NS. The in situ construction of organic/inorganic heterojunction with a chemical-bonded interface may provide guidance for the designing of high-performance heterostructure photocatalysts. Full article

(This article belongs to the Special Issue Functional Nanomaterials for Optoelectronics and Photocatalysis)

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16 pages, 5632 KiB

Open AccessReview

Encapsulation of Dyes in Luminescent Metal-Organic Frameworks for White Light Emitting Diodes

by Zhihong Sun, Aaqib Khurshid, Muhammad Sohail, Weidong Qiu, Derong Cao and Shi-Jian Su

Nanomaterials 2021, 11(10), 2761; https://doi.org/10.3390/nano11102761 - 18 Oct 2021

Cited by 31 | Viewed by 4285

Abstract

The development of white light emitting diodes (WLEDs) holds great promise for replacing traditional lighting devices due to high efficiency, low energy consumption and long lifetime. Metal-organic frameworks (MOFs) with a wide range of luminescent behaviors are ideal candidates to produce white light [...] Read more.

The development of white light emitting diodes (WLEDs) holds great promise for replacing traditional lighting devices due to high efficiency, low energy consumption and long lifetime. Metal-organic frameworks (MOFs) with a wide range of luminescent behaviors are ideal candidates to produce white light emission in the phosphor-converted WLEDs. Encapsulation of emissive organic dyes is a simple way to obtain luminescent MOFs. In this review, we summarize the recent progress on the design and constructions of dye encapsulated luminescent MOFs phosphors. Different strategies are highlighted where white light emitting phosphors were obtained by combining fluorescent dyes with metal ions and linkers. Full article

(This article belongs to the Special Issue Luminescence Nanomaterials and Applications)

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13 pages, 2625 KiB

Open AccessArticle

Broadband Achromatic Metasurfaces for Longwave Infrared Applications

by Naitao Song, Nianxi Xu, Dongzhi Shan, Yuanhang Zhao, Jinsong Gao, Yang Tang, Qiao Sun, Xin Chen, Yansong Wang and Xiaoguo Feng

Nanomaterials 2021, 11(10), 2760; https://doi.org/10.3390/nano11102760 - 18 Oct 2021

Cited by 23 | Viewed by 4719

Abstract

Longwave infrared (LWIR) optics are essential for several technologies, such as thermal imaging and wireless communication, but their development is hindered by their bulk and high fabrication costs. Metasurfaces have recently emerged as powerful platforms for LWIR integrated optics; however, conventional metasurfaces are [...] Read more.

Longwave infrared (LWIR) optics are essential for several technologies, such as thermal imaging and wireless communication, but their development is hindered by their bulk and high fabrication costs. Metasurfaces have recently emerged as powerful platforms for LWIR integrated optics; however, conventional metasurfaces are highly chromatic, which adversely affects their performance in broadband applications. In this work, the chromatic dispersion properties of metasurfaces are analyzed via ray tracing, and a general method for correcting chromatic aberrations of metasurfaces is presented. By combining the dynamic and geometric phases, the desired group delay and phase profiles are imparted to the metasurfaces simultaneously, resulting in good achromatic performance. Two broadband achromatic metasurfaces based on all-germanium platforms are demonstrated in the LWIR: a broadband achromatic metalens with a numerical aperture of 0.32, an average intensity efficiency of 31%, and a Strehl ratio above 0.8 from 9.6 μm to 11.6 μm, and a broadband achromatic metasurface grating with a constant deflection angle of 30° from 9.6 μm to 11.6 μm. Compared with state-of-the-art chromatic-aberration-restricted LWIR metasurfaces, this work represents a substantial advance and brings the field a step closer to practical applications. Full article

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8 pages, 1032 KiB

Open AccessArticle

Unified Model of Shot Noise in the Tunneling Current in Sub-10 nm MOSFETs

by Jonghwan Lee

Nanomaterials 2021, 11(10), 2759; https://doi.org/10.3390/nano11102759 - 18 Oct 2021

Cited by 6 | Viewed by 2360

Abstract

A single unified analytical model is presented to predict the shot noise for both the source-to-drain (SD) and the gate tunneling current in sub-10 nm MOSFETs with ultrathin oxide. Based on the Landauer formula, the model is constructed from the sequential tunneling flows [...] Read more.

A single unified analytical model is presented to predict the shot noise for both the source-to-drain (SD) and the gate tunneling current in sub-10 nm MOSFETs with ultrathin oxide. Based on the Landauer formula, the model is constructed from the sequential tunneling flows associated with number fluctuations. This approach provides the analytical formulation of the shot noise as a function of the applied voltages. The model performs well in predicting the Fano factor for shot noise in the SD and gate tunneling currents. Full article

(This article belongs to the Special Issue Transport and Noise Behavior of Nanoelectronic Devices)

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22 pages, 7734 KiB

Open AccessArticle

Mono- and Dicationic DABCO/Quinuclidine Composed Nanomaterials for the Loading of Steroidal Drug: 3² Factorial Design and Physicochemical Characterization

by Ana R. Fernandes, Elena Sanchez-Lopez, Antonello Santini, Tiago dos Santos, Maria L. Garcia, Amélia M. Silva and Eliana B. Souto

Nanomaterials 2021, 11(10), 2758; https://doi.org/10.3390/nano11102758 - 18 Oct 2021

Cited by 10 | Viewed by 2539

Abstract

Oil-in-water nanoemulsions (NEs) are considered a suitable nanotechnological approach to improve the eye-related bioavailability of lipophilic drugs. The potential of cationic NEs is prominent due to the electrostatic interaction that occurs between the positively charged droplets with the negatively charged mucins present in [...] Read more.

Oil-in-water nanoemulsions (NEs) are considered a suitable nanotechnological approach to improve the eye-related bioavailability of lipophilic drugs. The potential of cationic NEs is prominent due to the electrostatic interaction that occurs between the positively charged droplets with the negatively charged mucins present in the tear film. This interaction offers prolonged NEs residence at the ocular surface, increasing the drug absorption. Triamcinolone acetonide (TA) is one of the first pharmacologic strategies applied as an intravitreal injection in the treatment of age-related macular degeneration (AMD). Newly synthesized quaternary derivatives of 1,4-diazabicyclo[2.2.2]octane (DABCO) and quinuclidine surfactants have been screened with the purpose to select the best compound to formulate long-term stable NEs that combine the best physicochemical properties for the loading of TA intended for ocular administration. Full article

(This article belongs to the Special Issue Nanoencapsulation Strategies for Active Compounds Delivery)

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27 pages, 3116 KiB

Open AccessReview

Biomedical Applications of Chinese Herb-Synthesized Silver Nanoparticles by Phytonanotechnology

by Rehmat Islam, Leming Sun and Lianbing Zhang

Nanomaterials 2021, 11(10), 2757; https://doi.org/10.3390/nano11102757 - 18 Oct 2021

Cited by 23 | Viewed by 5595

Abstract

Recent advances in nanotechnology have opened up new avenues for the controlled synthesis of nanoparticles for biomedical and pharmaceutical applications. Chinese herbal medicine is a natural gift to humanity, and it has long been used as an antibacterial and anticancer agent. This study [...] Read more.

Recent advances in nanotechnology have opened up new avenues for the controlled synthesis of nanoparticles for biomedical and pharmaceutical applications. Chinese herbal medicine is a natural gift to humanity, and it has long been used as an antibacterial and anticancer agent. This study will highlight recent developments in the phytonanotechnological synthesis of Chinese herbal medicines to utilize their bioactive components in biomedical and therapeutic applications. Biologically synthesized silver nanoparticles (AgNPs) have emerged as a promising alternative to chemical and physical approaches for various biomedical applications. The comprehensive rationale of combinational or synergistic effects of Chinese herb-based AgNPs synthesis was investigated with superior physicochemical and biological properties, and their biomedical applications, including antimicrobial and anticancer activity and wound healing properties. AgNPs can damage the cell ultrastructure by triggering apoptosis, which includes the formation of reactive oxygen species (ROS), DNA disintegration, protein inactivation, and the regulation of various signaling pathways. However, the anticancer mechanism of Chinese herbal medicine-based AgNPs is more complicated due to the potential toxicity of AgNPs. Further in-depth studies are required to address Chinese herbs’ various bioactive components and AgNPs as a synergistic approach to combat antimicrobial resistance, therapeutic efficiency of drug delivery, and control and prevention of newly emerged diseases. Full article

(This article belongs to the Section Biology and Medicines)

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16 pages, 4289 KiB

Open AccessEditor’s ChoiceArticle

Environmentally Benign Formation of Nickel Hexacyanoferrate-Derived Mesoframes for Heterogeneous Catalysis

by Sascha Keßler, Elrike R. Reinalter, Johannes Schmidt and Helmut Cölfen

Nanomaterials 2021, 11(10), 2756; https://doi.org/10.3390/nano11102756 - 18 Oct 2021

Cited by 3 | Viewed by 2587

Abstract

The tetramethylammonium hydroxide (TMAH)-controlled alkaline etching of nickel hexacyanoferrate (NiHCF) mesocrystals is explored. The alkaline etching enables the formation of hollow framework structures with an increased surface area, the exposure of active Ni and Fe sites and the retention of morphology. The ambient [...] Read more.

The tetramethylammonium hydroxide (TMAH)-controlled alkaline etching of nickel hexacyanoferrate (NiHCF) mesocrystals is explored. The alkaline etching enables the formation of hollow framework structures with an increased surface area, the exposure of active Ni and Fe sites and the retention of morphology. The ambient reaction conditions enable the establishment of a sustainable production. Our work reveals novel perspectives on the eco-friendly synthesis of hollow and colloidal superstructures for the efficient degradation of the organic contaminants rhodamine-B and bisphenol-A. In the case of peroxomonosulfate (PMS)-mediated bisphenol-A degradation, the rate constant of the etched mesoframes was 10,000 times higher indicating their significant catalytic activity. Full article

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

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18 pages, 18355 KiB

Open AccessArticle

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal T_d-WTe₂

by Rajdeep Adhikari, Soma Adhikari, Bogdan Faina, Marc Terschanski, Sophie Bork, Claudia Leimhofer, Mirko Cinchetti and Alberta Bonanni

Nanomaterials 2021, 11(10), 2755; https://doi.org/10.3390/nano11102755 - 18 Oct 2021

Cited by 3 | Viewed by 4032

Abstract

Layered van der Waals semimetallic

T_{d}

-WTe

_{2}

, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of [...] Read more.

Layered van der Waals semimetallic

T_{d}

-WTe

_{2}

, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of

T_{d}

-WTe

_{2}

are studied via atomic force microscopy, Raman spectroscopy, low-T/high-

μ_{0} H

magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse

{MR}_{⊥}

and the signature of chiral anomaly of the type-II Weyl Fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties is observed. A transverse

{MR}_{⊥}

∼1200 % and an average carrier mobility of 5000 cm

^{2}

V

^{- 1}

s

^{- 1}

at

T = 5 K

for an applied perpendicular field

μ_{0} H_{⊥} = 7 T

are established. The system follows a Fermi liquid model for

T \leq 50 K

and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. Optical reflectivity measurements confirm the anisotropy of the electronic behaviour. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to determine the observed chiral anomaly in the in-plane magnetotransport. The observed chiral anomaly in the WTe

_{2}

flakes is found to persist up to

T = 120 K

, a temperature at least four times higher than the ones reported to date. Full article

(This article belongs to the Special Issue Transition Metal Dichalcogenides: From Fundamentals to Nanoelectronics)

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16 pages, 1768 KiB

Open AccessArticle

Studies on Aggregated Nanoparticles Steering during Deep Brain Membrane Crossing

by Ali Kafash Hoshiar, Shahriar Dadras Javan, Tuan-Anh Le, Mohammad Reza Hairi Yazdi and Jungwon Yoon

Nanomaterials 2021, 11(10), 2754; https://doi.org/10.3390/nano11102754 - 17 Oct 2021

Cited by 1 | Viewed by 2716

Abstract

Many central nervous system (CNS) diseases, such as Alzheimer’s disease (AD), affect the deep brain region, which hinders their effective treatment. The hippocampus, a deep brain area critical for learning and memory, is especially vulnerable to damage during early stages of AD. Magnetic [...] Read more.

Many central nervous system (CNS) diseases, such as Alzheimer’s disease (AD), affect the deep brain region, which hinders their effective treatment. The hippocampus, a deep brain area critical for learning and memory, is especially vulnerable to damage during early stages of AD. Magnetic drug targeting has shown high potential in delivering drugs to a targeted disease site effectively by applying a strong electromagnetic force. This study illustrates a nanotechnology-based scheme for delivering magnetic nanoparticles (MNP) to the deep brain region. First, we developed a mathematical model and a molecular dynamic simulation to analyze membrane crossing, and to study the effects of particle size, aggregation, and crossing velocities. Then, using in vitro experiments, we studied effective parameters in aggregation. We have also studied the process and environmental parameters. We have demonstrated that aggregation size can be controlled when particles are subjected to external electromagnetic fields. Our simulations and experimental studies can be used for capturing MNPs in brain, the transport of particles across the intact BBB and deep region targeting. These results are in line with previous in vivo studies and establish an effective strategy for deep brain region targeting with drug loaded MNPs through the application of an external electromagnetic field. Full article

(This article belongs to the Special Issue Smart Nano-Devices)

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15 pages, 3145 KiB

Open AccessArticle

Synergetic Effect of Organic Flocculant and Montmorillonite Clay on the Removal of Nano-CuO by Coagulation-Flocculation-Sedimentation Process

by Rizwan Khan, Muhammad Ali Inam, Kang-Hoon Lee, Abdul Sami Channa, Mukhtiar Ali Mallah, Young-Min Wie and Mahmood Nabi Abbasi

Nanomaterials 2021, 11(10), 2753; https://doi.org/10.3390/nano11102753 - 17 Oct 2021

Cited by 3 | Viewed by 2541

Abstract

The widespread usage of nano-copper oxide particles (nano-CuO) in several industrial products and applications raises concerns about their release into water bodies. Thus, their elimination from drinking water is essential to reduce the risk to human health. This work investigated the removal of [...] Read more.

The widespread usage of nano-copper oxide particles (nano-CuO) in several industrial products and applications raises concerns about their release into water bodies. Thus, their elimination from drinking water is essential to reduce the risk to human health. This work investigated the removal of nano-CuO from pure water and montmorillonite clay (MC) suspensions using poly aluminum ferric chloride (PAFC) as well as cationic polyacrylamide (PAM) by the coagulation-flocculation-sedimentation (C/F/S) process. Moreover, the PAFC and PAFC/PAM flocculation performance for various nano-CuO particles concentrations, dosages, pH, settling times and stirring speeds were also investigated. The findings showed that the removal of nano-CuO and turbidity in MC suspension were higher as compared to pure water. Moreover, the combined effect of PAFC/PAM on the elimination of nano-CuO and turbidity was also substantially better than the individual use of PAFC or PAM. The efficient removal of CuO was observed in the solution containing higher mass concentration in the order (10 mg/L > 2.5 mg/L > 1 mg/L) with an increased coagulant dose. The improved removal performance of nano-CuO was observed in a pH range of 7–11 under various water matrices. The C/F/S conditions of nano-CuO were further optimized by the Box–Behnken statistical experiment design and response surface methodology. The PAFC/PAM dose resulted in the maximum removal of nano-CuO (10 mg/L) in both pure water (>97%) and MC suspension (>99%). The results of particle monitoring and Fourier transform infrared of composite flocs revealed that the main removal mechanism of nano-CuO may be the combined effect of neutralization, complexation as well as adsorption. Full article

(This article belongs to the Special Issue Nanostructured Materials and Advanced Processes for Application in Water Purification)

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30 pages, 5667 KiB

Open AccessReview

Simulation and Computer Study of Structures and Physical Properties of Hydroxyapatite with Various Defects

by Vladimir Bystrov, Ekaterina Paramonova, Leon Avakyan, José Coutinho and Natalia Bulina

Nanomaterials 2021, 11(10), 2752; https://doi.org/10.3390/nano11102752 - 17 Oct 2021

Cited by 30 | Viewed by 3755

Abstract

Simulation and computer studies of the structural and physical properties of hydroxyapatite (HAP) with different defects are presented in this review. HAP is a well-known material that is actively used in various fields of medicine, nanotechnology, and photocatalytic processes. However, all HAP samples [...] Read more.

Simulation and computer studies of the structural and physical properties of hydroxyapatite (HAP) with different defects are presented in this review. HAP is a well-known material that is actively used in various fields of medicine, nanotechnology, and photocatalytic processes. However, all HAP samples have various defects and are still insufficiently studied. First of all, oxygen and OH group vacancies are important defects in HAP, which significantly affect its properties. The properties of HAP are also influenced by various substitutions of atoms in the HAP crystal lattice. The results of calculations by modern density functional theory methods of HAP structures with these different defects, primarily with oxygen and hydroxyl vacancies are analyzed in this review. The results obtained show that during the structural optimization of HAP with various defects, both the parameters of the crystallographic cells of the HAP change and the entire band structure of the HAP changes (changes in the band gap). This affects the electronic, optical, and elastic properties of HAP. The review considers the results of modeling and calculation of HAP containing various defects, the applied calculation methods, and the features of the effect of these defects on the properties of HAP, which is important for many practical applications. Full article

(This article belongs to the Special Issue Simulation and Modeling of Nanomaterials)

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11 pages, 2942 KiB

Open AccessArticle

Stress Effects on Temperature-Dependent In-Plane Raman Modes of Supported Monolayer Graphene Induced by Thermal Annealing

by Yuehua Wei, Zhenhua Wei, Xiaoming Zheng, Jinxin Liu, Yangbo Chen, Yue Su, Wei Luo, Gang Peng, Han Huang, Weiwei Cai, Chuyun Deng, Xueao Zhang and Shiqiao Qin

Nanomaterials 2021, 11(10), 2751; https://doi.org/10.3390/nano11102751 - 17 Oct 2021

Cited by 6 | Viewed by 2821

Abstract

The coupling strength between two-dimensional (2D) materials and substrate plays a vital role on thermal transport properties of 2D materials. Here we systematically investigate the influence of vacuum thermal annealing on the temperature-dependence of in-plane Raman phonon modes in monolayer graphene supported on [...] Read more.

The coupling strength between two-dimensional (2D) materials and substrate plays a vital role on thermal transport properties of 2D materials. Here we systematically investigate the influence of vacuum thermal annealing on the temperature-dependence of in-plane Raman phonon modes in monolayer graphene supported on silicon dioxide substrate via Raman spectroscopy. Intriguingly, raising the thermal annealing temperature can significantly enlarge the temperature coefficient of supported monolayer graphene. The derived temperature coefficient of G band remains mostly unchanged with thermal annealing temperature below 473 K, while it increases from −0.030 cm⁻¹/K to −0.0602 cm⁻¹/K with thermal annealing temperature ranging from 473 K to 773 K, suggesting the great impact of thermal annealing on thermal transport in supported monolayer graphene. Such an impact might reveal the vital role of coupling strength on phonon scattering and on the thermal transport property of supported monolayer graphene. To further interpret the thermal annealing mechanism, the compressive stress in supported monolayer graphene, which is closely related to coupling strength and is studied through the temperature-dependent Raman spectra. It is found that the variation tendency for compressive stress induced by thermal annealing is the same as that for temperature coefficient, implying the intense connection between compressive stress and thermal transport. Actually, 773 K thermal annealing can result in 2.02 GPa compressive stress on supported monolayer graphene due to the lattice mismatch of graphene and substrate. This study proposes thermal annealing as a feasible path to modulate the thermal transport in supported graphene and to design future graphene-based devices. Full article

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

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15 pages, 3410 KiB

Open AccessArticle

Bamboo-Based Mesoporous Activated Carbon for High-Power-Density Electric Double-Layer Capacitors

by Ju-Hwan Kim, Hye-Min Lee, Sang-Chul Jung, Dong-Chul Chung and Byung-Joo Kim

Nanomaterials 2021, 11(10), 2750; https://doi.org/10.3390/nano11102750 - 17 Oct 2021

Cited by 15 | Viewed by 3558

Abstract

Demand for hybrid energy storage systems is growing, but electric double-layer capacitors (EDLCs) have insufficient output characteristics because of the microporous structure of the activated carbon electrode material. Commercially, activated carbon is prepared from coconut shells, which yield an activated carbon material (YP-50F) [...] Read more.

Demand for hybrid energy storage systems is growing, but electric double-layer capacitors (EDLCs) have insufficient output characteristics because of the microporous structure of the activated carbon electrode material. Commercially, activated carbon is prepared from coconut shells, which yield an activated carbon material (YP-50F) rich in micropores, whereas mesopores are desired in EDLCs. In this study, we prepared mesoporous activated carbon (PB-AC) using a readily available, environmentally friendly resource: bamboo. Crucially, modification using phosphoric acid and steam activation was carried out, which enabled the tuning of the crystal structure and the pore characteristics of the product. The structural characteristics and textural properties of the PB-AC were determined, and the specific surface area and mesopore volume ratio of the PB-AC product were 960–2700 m²/g and 7.5–44.5%, respectively. The high specific surface area and mesopore-rich nature originate from the phosphoric acid treatment. Finally, PB-AC was used as the electrode material in EDLCs, and the specific capacitance was found to be 86.7 F/g for the phosphoric-acid-treated sample steam activated at 900 °C for 60 min; this capacitance is 35% better than that of the commercial YP-50F (64.2 F/g), indicating that bamboo is a suitable material for the production of activated carbon. Full article

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

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25 pages, 3972 KiB

Open AccessReview

Effect of Metal Nanopowders on the Performance of Solid Rocket Propellants: A Review

by Weiqiang Pang, Yang Li, Luigi T. DeLuca, Daolun Liang, Zhao Qin, Xiaogang Liu, Huixiang Xu and Xuezhong Fan

Nanomaterials 2021, 11(10), 2749; https://doi.org/10.3390/nano11102749 - 17 Oct 2021

Cited by 37 | Viewed by 5274

Abstract

The effects of different types of nano-sized metal particles, such as aluminum (nAl), zirconium (nZr), titanium (nTi), and nickel (nNi), on the properties of a variety of solid rocket propellants (composite, fuel-rich, and composite modified double base (CMDB)) were analyzed and compared with [...] Read more.

The effects of different types of nano-sized metal particles, such as aluminum (nAl), zirconium (nZr), titanium (nTi), and nickel (nNi), on the properties of a variety of solid rocket propellants (composite, fuel-rich, and composite modified double base (CMDB)) were analyzed and compared with those of propellants loaded with micro-sized Al (mAl) powder. Emphasis was placed on the investigation of burning rate, pressure exponent (n), and hazardous properties, which control whether a propellant can be adopted in solid rocket motors. It was found that nano-sized additives can affect the combustion behavior and increase the burning rate of propellants. Compared with the corresponding micro-sized ones, the nano-sized particles promote higher impact sensitivity and friction sensitivity. In this paper, 101 references are enclosed. Full article

(This article belongs to the Special Issue Energetic Nanomaterials)

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15 pages, 2988 KiB

Open AccessArticle

Nonenzymatic Hydrogen Peroxide Detection Using Surface-Enhanced Raman Scattering of Gold–Silver Core–Shell-Assembled Silica Nanostructures

by Xuan-Hung Pham, Bomi Seong, Sungje Bock, Eunil Hahm, Kim-Hung Huynh, Yoon-Hee Kim, Wooyeon Kim, Jaehi Kim, Dong-Eun Kim and Bong-Hyun Jun

Nanomaterials 2021, 11(10), 2748; https://doi.org/10.3390/nano11102748 - 17 Oct 2021

Cited by 14 | Viewed by 3413

Abstract

Hydrogen peroxide (H₂O₂) plays important roles in cellular signaling and in industry. Thus, the accurate detection of H₂O₂ is critical for its application. Unfortunately, the direct detection of H₂O₂ by surface-enhanced Raman spectroscopy [...] Read more.

Hydrogen peroxide (H₂O₂) plays important roles in cellular signaling and in industry. Thus, the accurate detection of H₂O₂ is critical for its application. Unfortunately, the direct detection of H₂O₂ by surface-enhanced Raman spectroscopy (SERS) is not possible because of its low Raman cross section. Therefore, the detection of H₂O₂ via the presence of an intermediary such as 3,3,5,5-tetramethylbenzidine (TMB) has recently been developed. In this study, the peroxidase-mimicking activity of gold–silver core–shell-assembled silica nanostructures (SiO₂@Au@Ag alloy NPs) in the presence of TMB was investigated using SERS for detecting H₂O₂. In the presence of H₂O₂, the SiO₂@Au@Ag alloy catalyzed the conversion of TMB to oxidized TMB, which was absorbed onto the surface of the SiO₂@Au@Ag alloy. The SERS characteristics of the alloy in the TMB–H₂O₂ mixture were investigated. The evaluation of the SERS band to determine the H₂O₂ level utilized the SERS intensity of oxidized TMB bands. Moreover, the optimal conditions for H₂O₂ detection using SiO₂@Au@Ag alloy included incubating 20 µg/mL SiO₂@Au@Ag alloy NPs with 0.8 mM TMB for 15 min and measuring the Raman signal at 400 µg/mL SiO₂@Au@Ag alloy NPs. Full article

(This article belongs to the Special Issue Synthesis and Application of Optical Materials)

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20 pages, 1233 KiB

Open AccessReview

Characteristics, Toxic Effects, and Analytical Methods of Microplastics in the Atmosphere

by Huirong Yang, Yinglin He, Yumeng Yan, Muhammad Junaid and Jun Wang

Nanomaterials 2021, 11(10), 2747; https://doi.org/10.3390/nano11102747 - 17 Oct 2021

Cited by 36 | Viewed by 4984

Abstract

Microplastics (MPs) (including nanoplastics (NPs)) are pieces of plastic smaller than 5 mm in size. They are produced by the crushing and decomposition of large waste plastics and widely distributed in all kinds of ecological environments and even in organisms, so they have [...] Read more.

Microplastics (MPs) (including nanoplastics (NPs)) are pieces of plastic smaller than 5 mm in size. They are produced by the crushing and decomposition of large waste plastics and widely distributed in all kinds of ecological environments and even in organisms, so they have been paid much attention by the public and scientific community. Previously, several studies have reviewed the sources, occurrence, distribution, and toxicity of MPs in water and soil. By comparison, the review of atmospheric MPs is inadequate. In particular, there are still significant gaps in the quantitative analysis of MPs and the mechanisms associated with the toxic effects of inhaled MPs. Thus, this review summarizes and analyzes the distribution, source, and fate of atmospheric MPs and related influencing factors. The potential toxic effects of atmospheric MPs on animals and humans are also reviewed in depth. In addition, the common sampling and analysis methods used in existing studies are introduced. The aim of this paper is to put forward some feasible suggestions on the research direction of atmospheric MPs in the future. Full article

(This article belongs to the Special Issue Nanoparticles in the Environment and Nanotoxicology)

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32 pages, 10640 KiB

Open AccessReview

Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies

by Vo Pham Hoang Huy, Luong Trung Hieu and Jaehyun Hur

Nanomaterials 2021, 11(10), 2746; https://doi.org/10.3390/nano11102746 - 17 Oct 2021

Cited by 44 | Viewed by 7235

Abstract

Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as [...] Read more.

Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as the growth of Zn dendrites, occurrence of side reactions, and hydrogen evolution during repeated stripping/plating processes result in poor cycling life and low Coulombic efficiency, which severely impede further advancements in this technology. Despite recent efforts and impressive breakthroughs, the origin of these fundamental obstacles remains unclear and no successful strategy that can address these issues has been developed yet to realize the practical applications of rechargeable aqueous Zn-ion batteries. In this review, we have discussed various issues associated with the use of Zn metal anodes in mildly acidic aqueous electrolytes. Various strategies, including the shielding of the Zn surface, regulating the Zn deposition behavior, creating a uniform electric field, and controlling the surface energy of Zn metal anodes to repress the growth of Zn dendrites and the occurrence of side reactions, proposed to overcome the limitations of Zn metal anodes have also been discussed. Finally, the future perspectives of Zn anodes and possible design strategies for developing highly stable Zn anodes in mildly acidic aqueous environments have been discussed. Full article

(This article belongs to the Special Issue Nanomaterials for Ion Battery Applications)

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14 pages, 3747 KiB

Open AccessArticle

Oligo(Lactic Acid)₈-Docetaxel Prodrug-Loaded PEG-b-PLA Micelles for Prostate Cancer

by Lauren Repp, Christopher J. Unterberger, Zhengqing Ye, John B. Feltenberger, Steven M. Swanson, Paul C. Marker and Glen S. Kwon

Nanomaterials 2021, 11(10), 2745; https://doi.org/10.3390/nano11102745 - 17 Oct 2021

Cited by 11 | Viewed by 3928

Abstract

Docetaxel (DTX) is among the most frequently prescribed chemotherapy drugs and has recently been shown to extend survival in advanced prostate cancer patients. However, the poor water solubility of DTX prevents full exploitation of this potent anticancer drug. The current marketed formulation, Taxotere [...] Read more.

Docetaxel (DTX) is among the most frequently prescribed chemotherapy drugs and has recently been shown to extend survival in advanced prostate cancer patients. However, the poor water solubility of DTX prevents full exploitation of this potent anticancer drug. The current marketed formulation, Taxotere^®, contains a toxic co-solvent that induces adverse reactions following intravenous injection. Nano-sized polymeric micelles have been proposed to create safer, water-soluble carriers for DTX, but many have failed to reach the clinic due to poor carrier stability in vivo. In this study, we aimed to improve micelle stability by synthesizing an ester prodrug of DTX, oligo(lactic acid)₈-docetaxel (o(LA)₈-DTX), for augmented compatibility with the core of poly(ethylene glycol)-b-poly(lactic acid) (PEG-b-PLA) micelles. Due to the enhancement of drug-carrier compatibility, we were able to load 50% (w/w) prodrug within the micelle, solubilize 20 mg/mL o(LA)₈-DTX (~12 mg/mL DTX-equivalent) in aqueous media, and delay payload release. While the micelle core prohibited premature degradation, o(LA)₈-DTX was rapidly converted to parent drug DTX through intramolecular backbiting (t_1/2 = 6.3 h) or esterase-mediated degradation (t_1/2 = 2.5 h) following release. Most importantly, o(LA)₈-DTX micelles proved to be as efficacious but less toxic than Taxotere^® in a preclinical mouse model of prostate cancer. Full article

(This article belongs to the Special Issue Development of Multifunctional Nanoparticles for Therapy and/or Diagnosis)

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35 pages, 5713 KiB

Open AccessEditor’s ChoiceReview

Spherical Cellulose Micro and Nanoparticles: A Review of Recent Developments and Applications

by João P. F. Carvalho, Ana C. Q. Silva, Armando J. D. Silvestre, Carmen S. R. Freire and Carla Vilela

Nanomaterials 2021, 11(10), 2744; https://doi.org/10.3390/nano11102744 - 17 Oct 2021

Cited by 51 | Viewed by 9043

Abstract

Cellulose, the most abundant natural polymer, is a versatile polysaccharide that is being exploited to manufacture innovative blends, composites, and hybrid materials in the form of membranes, films, coatings, hydrogels, and foams, as well as particles at the micro and nano scales. The [...] Read more.

Cellulose, the most abundant natural polymer, is a versatile polysaccharide that is being exploited to manufacture innovative blends, composites, and hybrid materials in the form of membranes, films, coatings, hydrogels, and foams, as well as particles at the micro and nano scales. The application fields of cellulose micro and nanoparticles run the gamut from medicine, biology, and environment to electronics and energy. In fact, the number of studies dealing with sphere-shaped micro and nanoparticles based exclusively on cellulose (or its derivatives) or cellulose in combination with other molecules and macromolecules has been steadily increasing in the last five years. Hence, there is a clear need for an up-to-date narrative that gathers the latest advances on this research topic. So, the aim of this review is to portray some of the most recent and relevant developments on the use of cellulose to produce spherical micro- and nano-sized particles. An attempt was made to illustrate the present state of affairs in terms of the go-to strategies (e.g., emulsification processes, nanoprecipitation, microfluidics, and other assembly approaches) for the generation of sphere-shaped particles of cellulose and derivatives thereof. A concise description of the application fields of these cellulose-based spherical micro and nanoparticles is also presented. Full article

(This article belongs to the Special Issue Nanoparticles from Natural Polymers: Synthesis and Applications)

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15 pages, 3910 KiB

Open AccessArticle

Germanium Quantum-Dot Array with Self-Aligned Electrodes for Quantum Electronic Devices

by I-Hsiang Wang, Po-Yu Hong, Kang-Ping Peng, Horng-Chih Lin, Thomas George and Pei-Wen Li

Nanomaterials 2021, 11(10), 2743; https://doi.org/10.3390/nano11102743 - 16 Oct 2021

Cited by 6 | Viewed by 2820

Abstract

Semiconductor-based quantum registers require scalable quantum-dots (QDs) to be accurately located in close proximity to and independently addressable by external electrodes. Si-based QD qubits have been realized in various lithographically-defined Si/SiGe heterostructures and validated only for milli-Kelvin temperature operation. QD qubits have recently [...] Read more.

Semiconductor-based quantum registers require scalable quantum-dots (QDs) to be accurately located in close proximity to and independently addressable by external electrodes. Si-based QD qubits have been realized in various lithographically-defined Si/SiGe heterostructures and validated only for milli-Kelvin temperature operation. QD qubits have recently been explored in germanium (Ge) materials systems that are envisaged to operate at higher temperatures, relax lithographic-fabrication requirements, and scale up to large quantum systems. We report the unique scalability and tunability of Ge spherical-shaped QDs that are controllably located, closely coupled between each another, and self-aligned with control electrodes, using a coordinated combination of lithographic patterning and self-assembled growth. The core experimental design is based on the thermal oxidation of poly-SiGe spacer islands located at each sidewall corner or included-angle location of Si₃N₄/Si-ridges with specially designed fanout structures. Multiple Ge QDs with good tunability in QD sizes and self-aligned electrodes were controllably achieved. Spherical-shaped Ge QDs are closely coupled to each other via coupling barriers of Si₃N₄ spacer layers/c-Si that are electrically tunable via self-aligned poly-Si or polycide electrodes. Our ability to place size-tunable spherical Ge QDs at any desired location, therefore, offers a large parameter space within which to design novel quantum electronic devices. Full article

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

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20 pages, 4478 KiB

Open AccessArticle

Comparison of the Surface Properties of Hydrothermally Synthesised Fe₃O₄@C Nanocomposites at Variable Reaction Times

by Sadiq Sani, Rohana Adnan, Wen-Da Oh and Anwar Iqbal

Nanomaterials 2021, 11(10), 2742; https://doi.org/10.3390/nano11102742 - 16 Oct 2021

Cited by 5 | Viewed by 2160

Abstract

The influence of variable reaction time (t_r) on surface/textural properties (surface area, total pore volume, and pore diameter) of carbon-encapsulated magnetite (Fe₃O₄@C) nanocomposites fabricated by a hydrothermal process at 190 °C for 3, 4, and 5 h [...] Read more.

The influence of variable reaction time (t_r) on surface/textural properties (surface area, total pore volume, and pore diameter) of carbon-encapsulated magnetite (Fe₃O₄@C) nanocomposites fabricated by a hydrothermal process at 190 °C for 3, 4, and 5 h was studied. The properties were calculated using the Brunauer–Emmett–Teller (BET) isotherms data. The nanocomposites were characterised using Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetry, and scanning and transmission electron microscopies. Analysis of variance shows t_r has the largest effect on pore volume (F value = 1117.6, p value < 0.0001), followed by the surface area (F value = 54.8, p value < 0.0001) and pore diameter (F value = 10.4, p value < 0.001) with R²-adjusted values of 99.5%, 88.5% and 63.1%, respectively. Tukey and Fisher tests confirmed t_r rise to have caused increased variations in mean particle sizes (11–91 nm), crystallite sizes (5–21 nm), pore diameters (9–16 nm), pore volume (0.017–0.089 cm³ g⁻¹) and surface area (7.6–22.4 m² g⁻¹) of the nanocomposites with individual and simultaneous confidence limits of 97.9 and 84.4 (p-adj < 0.05). The nanocomposites’ retained Fe–O vibrations at octahedral (436 cm⁻¹) and tetrahedral (570 cm⁻¹) cubic ferrite sites, modest thermal stability (37–60 % weight loss), and large volume-specific surface area with potential for catalytic application in advanced oxidation processes. Full article

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

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12 pages, 4612 KiB

Open AccessArticle

Synthesis and Third-Order Nonlinear Synergistic Effect of ZrO₂/RGO Composites

by Xinting Zhao, Fangfang Wang, Jiawen Wu, Baohua Zhu and Yuzong Gu

Nanomaterials 2021, 11(10), 2741; https://doi.org/10.3390/nano11102741 - 16 Oct 2021

Cited by 3 | Viewed by 2025

Abstract

Tuning the third-order nonlinear properties of graphene by hybrid method is of great significance in nonlinear optics research. ZrO₂/reduced graphene oxide (RGO) composites with different ZrO₂ concentrations were prepared by a simple hydrothermal method. The morphology and structure show that [...] Read more.

Tuning the third-order nonlinear properties of graphene by hybrid method is of great significance in nonlinear optics research. ZrO₂/reduced graphene oxide (RGO) composites with different ZrO₂ concentrations were prepared by a simple hydrothermal method. The morphology and structure show that ZrO₂ nanoparticles were uniformly dispersed on the surface of graphene nanosheets. The nonlinear optical (NLO) characteristics of composites with different ZrO₂ concentrations were studied by the Z-scan technique of 532 nm picosecond pulsed laser. The results showed that ZrO₂/RGO composites had saturated absorption and positive nonlinear refraction characteristics. Meanwhile, the third-order nonlinear susceptibility of the ZrO₂/RGO composite with a 4:1 mass ratio of ZrO₂ to graphene oxide could reach 23.23 × 10⁻¹² esu, which increased tenfold compared to RGO, and the nonlinear modulation depth reached 11.22%. Therefore, the NLO characteristics could be effectively adjusted by controlling the concentration of ZrO₂, which lays a foundation for further research on the application of ZrO₂/RGO composites in NLO devices. Full article

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