Nanomaterials

9 pages, 3650 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhanced Field-Effect Control of Single-Layer WS₂ Optical Features by hBN Full Encapsulation

by Anna Di Renzo, Onur Çakıroğlu, Felix Carrascoso, Hao Li, Giuseppe Gigli, Kenji Watanabe, Takashi Taniguchi, Carmen Munuera, Aurora Rizzo, Andres Castellanos-Gomez, Rosanna Mastria and Riccardo Frisenda

Nanomaterials 2022, 12(24), 4425; https://doi.org/10.3390/nano12244425 - 12 Dec 2022

Cited by 1 | Viewed by 2234

Abstract

The field-effect control of the electrical and optical properties of two-dimensional (2D) van der Waals semiconductors (vdW) is one important aspect of this novel class of materials. Thanks to their reduced thickness and decreased screening, electric fields can easily penetrate in a 2D [...] Read more.

The field-effect control of the electrical and optical properties of two-dimensional (2D) van der Waals semiconductors (vdW) is one important aspect of this novel class of materials. Thanks to their reduced thickness and decreased screening, electric fields can easily penetrate in a 2D semiconductor and thus modulate their charge density and their properties. In literature, the field effect is routinely used to fabricate atomically thin field-effect transistors based on 2D semiconductors. Apart from the tuning of the electrical transport, it has been demonstrated that the field effect can also be used to modulate the excitonic optical emission of 2D transition metal dichalcogenides such as MoS₂ or WSe₂. In this paper, we present some recent experiments on the field-effect control of the optical and excitonic properties of the monolayer WS₂. Using the deterministic transfer of van der Waals materials, we fabricate planar single-layer WS₂ devices contacted by a gold electrode and partially sandwiched between two insulating hexagonal boron nitride (hBN) flakes. Thanks to the planar nature of the device, we can optically access both the hBN encapsulated and the unencapsulated WS₂ regions and compare the field-effect control of the exciton population in the two cases. We find that the encapsulation strongly increases the range of tunability of the optical emission of WS₂, allowing us to tune the photoluminescence emission from excitons-dominated to trions-dominated. We also discuss how the full encapsulation of WS₂ with hBN helps reduce spurious hysteretic effects in the field-effect control of the optical properties, similar to what has been reported for 2D vdW field-effect transistors. Full article

(This article belongs to the Special Issue Advances in Semiconductor Nano-Structures)

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19 pages, 4737 KiB

Open AccessEditor’s ChoiceArticle

Effective Antibacterial/Photocatalytic Activity of ZnO Nanomaterials Synthesized under Low Temperature and Alkaline Conditions

by Sujeong Kim, Hyerim Park, Sadanand Pandey, Daewon Jeong, Chul-Tae Lee, Jeong Yeon Do, Sun-Min Park and Misook Kang

Nanomaterials 2022, 12(24), 4417; https://doi.org/10.3390/nano12244417 - 11 Dec 2022

Cited by 11 | Viewed by 1982

Abstract

The purpose of this study was to evaluate the surface properties of ZnO nanomaterials based on their ability to photodegrade methyl blue dye (MB) and to show their antibacterial properties against different types of Gram-positive bacteria (Bacillus manliponensis, Micrococcus luteus, [...] Read more.

The purpose of this study was to evaluate the surface properties of ZnO nanomaterials based on their ability to photodegrade methyl blue dye (MB) and to show their antibacterial properties against different types of Gram-positive bacteria (Bacillus manliponensis, Micrococcus luteus, Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). In this study, ZnO nanomaterials were synthesized rapidly and easily in the presence of 1–4 M NaOH at a low temperature of 40 °C within 4 h. It was found that the ZnO nanomaterials obtained from the 1.0 M (ZnO–1M) and 2.0 M (ZnO–2M) aqueous solutions of NaOH had spherical and needle-shaped forms, respectively. As the concentration of NaOH increased, needle thickness increased and the particles became rod-like. Although the ZnO nanomaterial shapes were different, the bandgap size remained almost unchanged. However, as the NaOH concentration increased, the energy position of the conduction band shifted upward. Photo current curves and photoluminescence intensities suggested that the recombination between photoexcited electrons and holes was low in the ZnO–4M materials prepared in 4.0 M NaOH solution; however, charge transfer was easy. ∙O₂⁻ radicals were generated more than ∙OH radicals in ZnO–4M particles, showing stronger antibacterial activity against both Gram-positive and Gram-negative bacteria and stronger decomposition ability on MB dye. The results of this study suggest that on the ZnO nanomaterial surface, ∙O₂⁻ radicals generated are more critical for antibacterial activity than particle shape. Full article

(This article belongs to the Special Issue Synthesis of Nanomaterials as Electrocatalysis, Photocatalysis and Thermal Catalysis)

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33 pages, 21104 KiB

Open AccessEditor’s ChoiceArticle

Micromagnetic Design of Skyrmionic Materials and Chiral Magnetic Configurations in Patterned Nanostructures for Neuromorphic and Qubit Applications

by Roxana-Alina One, Sever Mican, Angela-Georgiana Cimpoeșu, Marius Joldos, Romulus Tetean and Coriolan Viorel Tiușan

Nanomaterials 2022, 12(24), 4411; https://doi.org/10.3390/nano12244411 - 10 Dec 2022

Cited by 2 | Viewed by 2502

Abstract

Our study addresses the problematics of magnetic skyrmions, nanometer-size vortex-like swirling topological defects, broadly studied today for applications in classic, neuromorphic and quantum information technologies. We tackle some challenging issues of material properties versus skyrmion stability and manipulation within a multiple-scale modeling framework, [...] Read more.

Our study addresses the problematics of magnetic skyrmions, nanometer-size vortex-like swirling topological defects, broadly studied today for applications in classic, neuromorphic and quantum information technologies. We tackle some challenging issues of material properties versus skyrmion stability and manipulation within a multiple-scale modeling framework, involving complementary ab-initio and micromagnetic frameworks. Ab-initio calculations provide insight into the anatomy of the magnetic anisotropy, the Dzyaloshinskii–Moriya asymmetric exchange interaction (DMI) and their response to a gating electric field. Various multi-layered heterostructures were specially designed to provide electric field tunable perpendicular magnetization and sizeable DMI, which are required for skyrmion occurrence. Landau–Lifshitz–Gilbert micromagnetic calculations in nanometric disks allowed the extraction of material parameter phase diagrams in which magnetic textures were classified according to their topological charge. We identified suitable ranges of magnetic anisotropy, DMI and saturation magnetization for stabilizing skyrmionic ground states or writing/manipulating them using either a spin-transfer torque of a perpendicular current or the electric field. From analyzing the different contributions to the total magnetic free energy, we point out some critical properties influencing the skyrmions’ stability. Finally, we discuss some experimental issues related to the choice of materials or the design of novel magnetic materials compatible with skyrmionic applications. Full article

(This article belongs to the Special Issue New Achievements in Nanostructured and Low Dimensional Materials and Systems)

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13 pages, 2991 KiB

Open AccessEditor’s ChoiceArticle

Hydrogenated Amorphous Silicon-Based Nanomaterials as Alternative Electrodes to Graphite for Lithium-Ion Batteries

by Rocío Barrio, Nieves González, Álvaro Portugal, Carmen Morant and José Javier Gandía

Nanomaterials 2022, 12(24), 4400; https://doi.org/10.3390/nano12244400 - 9 Dec 2022

Cited by 1 | Viewed by 1781

Abstract

Graphite is the material most used as an electrode in commercial lithium-ion batteries. On the other hand, it is a material with low energy capacity, and it is considered a raw critical material given its large volume of use. In the current energy [...] Read more.

Graphite is the material most used as an electrode in commercial lithium-ion batteries. On the other hand, it is a material with low energy capacity, and it is considered a raw critical material given its large volume of use. In the current energy context, we must promote the search for alternative materials based on elements that are abundant, sustainable and that have better performance for energy storage. We propose thin materials based on silicon, which has a storage capacity eleven times higher than graphite. Nevertheless, due to the high-volume expansion during lithiation, it tends to crack, limiting the life of the batteries. To solve this problem, hydrogenated amorphous silicon has been researched, in the form of thin film and nanostructures, since, due to its amorphous structure, porosity and high specific surface, it could better absorb changes in volume. These thin films were grown by plasma-enhanced chemical vapor deposition, and then the nanowires were obtained by chemical etching. The compositional variations of films deposited at different temperatures and the incorporation of dopants markedly influence the stability and longevity of batteries. With these optimized electrodes, we achieved batteries with an initial capacity of 3800 mAhg⁻¹ and 82% capacity retention after 50 cycles. Full article

(This article belongs to the Special Issue Application of Nanomaterials for Electrochemical Energy Conversion and Storage Devices)

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15 pages, 3093 KiB

Open AccessEditor’s ChoiceArticle

Mechanically Enhanced Nanocrystalline Cellulose/Reduced Graphene Oxide/Polyethylene Glycol Electrically Conductive Composite Film

by Pengbo Xie, Ying Ge, Yida Wang, Jing Zhou, Yuanyuan Miao and Zhenbo Liu

Nanomaterials 2022, 12(24), 4371; https://doi.org/10.3390/nano12244371 - 8 Dec 2022

Cited by 3 | Viewed by 1962

Abstract

Traditional conductive materials do not meet the increasing requirements of electronic products because of such materials’ high rigidity, poor flexibility, and slow biodegradation after disposal. Preparing flexible conductive materials with excellent mechanical properties is an active area of research. The key to flexible [...] Read more.

Traditional conductive materials do not meet the increasing requirements of electronic products because of such materials’ high rigidity, poor flexibility, and slow biodegradation after disposal. Preparing flexible conductive materials with excellent mechanical properties is an active area of research. The key to flexible conductive materials lies in the combination of the polymer matrix and conductive components. This combination can be achieved by making a film of renewable nano-microcrystalline cellulose (NCC) and reduced graphene oxide (rGO) with excellent electrical conductivity—by simple filtration and introducing polyethylene glycol (PEG) to enhance the functionality of the composite film. Graphene imparted conductivity to the composite film, which reached 5.67 S·m⁻¹. A reinforced NCC/rGO/PEG-4 composite film with a thickness of only 21 μm exhibited a tensile strength of 30.56 MPa, which was 83% higher than that of the sample without PEG (16.71 MPa), and toughness of 727.18 kJ·m⁻³, which was about 132% higher than that of the control sample (NCC/rGO, 313.86 kJ·m⁻³). This ultra-thin conductive composite film—which can be prepared simply, consists of environmentally sustainable and biodegradable raw materials, and exhibits excellent mechanical properties—has substantial potential for applications in e.g., flexible electronic wearable devices, electrodes, and capacitors. Full article

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12 pages, 5293 KiB

Open AccessEditor’s ChoiceArticle

Green Extraction of Graphene from Natural Mineral Shungite

by Anastasia Novikova and Alina Karabchevsky

Nanomaterials 2022, 12(24), 4356; https://doi.org/10.3390/nano12244356 - 7 Dec 2022

Cited by 5 | Viewed by 1955

Abstract

Conventional fabrication methods to produce graphene are cumbersome, expensive, and not ecologically friendly. This is due to the fact that the processing of a large volume of raw materials requires large amounts of acids and alkalis which, in turn, require special disposal. Therefore, [...] Read more.

Conventional fabrication methods to produce graphene are cumbersome, expensive, and not ecologically friendly. This is due to the fact that the processing of a large volume of raw materials requires large amounts of acids and alkalis which, in turn, require special disposal. Therefore, it is necessary to develop new technologies or to refine existing ones for the production of graphene—and to create new, ecologically-safe and effective methods. Here, we utilized physical sonication to extract graphene films from natural mineral shungite rock. From our study of the structure of shungite by Raman spectrometry and X-ray phase analysis, we found that shungite is characterized by graphite-like mineral structures. Transmission electron microscopy images obtained from the processed material revealed graphene films—with surfaces as small as 200 nanometers long and several layers wide. Our green method of fabicating graphene can be widely used in a variety of fields, from electro-optics to ecology, to list a few. Full article

(This article belongs to the Special Issue 2D Materials for Advanced Sensors: Fabrication and Applications)

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13 pages, 4997 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Antiviral Properties against SARS-CoV-2 of Nanostructured ZnO Obtained by Green Combustion Synthesis and Coated in Waterborne Acrylic Coatings

by Julia de O. Primo, Jamille de S. Correa, Dienifer F. L. Horsth, Arkaprava Das, Marcin Zając, Polona Umek, Ruddy Wattiez, Fauze J. Anaissi, Rob C. A. Onderwater and Carla Bittencourt

Nanomaterials 2022, 12(23), 4345; https://doi.org/10.3390/nano12234345 - 6 Dec 2022

Cited by 7 | Viewed by 2458

Abstract

The COVID-19 pandemic has increased the need for developing disinfectant surfaces as well as reducing the spread of infections on contaminated surfaces and the contamination risk from the fomite route. The present work reports on the antiviral activity of coatings containing ZnO particles [...] Read more.

The COVID-19 pandemic has increased the need for developing disinfectant surfaces as well as reducing the spread of infections on contaminated surfaces and the contamination risk from the fomite route. The present work reports on the antiviral activity of coatings containing ZnO particles obtained by two simple synthesis routes using Aloe vera (ZnO-aloe) or cassava starch (ZnO-starch) as reaction fuel. After detailed characterization using XRD and NEXAFS, the obtained ZnO particles were dispersed in a proportion of 10% with two different waterborne acrylic coatings (binder and commercial white paint) and brushed on the surface of polycarbonates (PC). The cured ZnO/coatings were characterized by scanning electron microscopes (SEM) and energy-dispersive X-ray spectroscopy (EDS). Wettability tests were performed. The virucidal activity of the ZnO particles dispersed in the waterborne acrylic coating was compared to a reference control sample (PC plates). According to RT-PCR results, the ZnO-aloe/coating displays the highest outcome for antiviral activity against SARS-CoV-2 using the acrylic binder, inactivating >99% of the virus after 24 h of contact relative to reference control. Full article

(This article belongs to the Special Issue Applications of Nanomaterials in Diagnostics and Therapeutics)

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14 pages, 3264 KiB

Open AccessEditor’s ChoiceArticle

Postproduction Approach to Enhance the External Quantum Efficiency for Red Light-Emitting Diodes Based on Silicon Nanocrystals

by Hiroyuki Yamada, Junpei Watanabe, Kazuhiro Nemoto, Hong-Tao Sun and Naoto Shirahata

Nanomaterials 2022, 12(23), 4314; https://doi.org/10.3390/nano12234314 - 5 Dec 2022

Cited by 4 | Viewed by 2065

Abstract

Despite bulk crystals of silicon (Si) being indirect bandgap semiconductors, their quantum dots (QDs) exhibit the superior photoluminescence (PL) properties including high quantum yield (PLQY > 50%) and spectral tunability in a broad wavelength range. Nevertheless, their low optical absorbance character inhibits the [...] Read more.

Despite bulk crystals of silicon (Si) being indirect bandgap semiconductors, their quantum dots (QDs) exhibit the superior photoluminescence (PL) properties including high quantum yield (PLQY > 50%) and spectral tunability in a broad wavelength range. Nevertheless, their low optical absorbance character inhibits the bright emission from the SiQDs for phosphor-type light emitting diodes (LEDs). In contrast, a strong electroluminescence is potentially given by serving SiQDs as an emissive layer of current-driven LEDs with (Si-QLEDs) because the charged carriers are supplied from electrodes unlike absorption of light. Herein, we report that the external quantum efficiency (EQE) of Si-QLED was enhanced up to 12.2% by postproduction effect which induced by continuously applied voltage at 5 V for 9 h. The active layer consisted of SiQDs with a diameter of 2.0 nm. Observation of the cross-section of the multilayer QLEDs device revealed that the interparticle distance between adjacent SiQDs in the emissive layer is reduced to 0.95 nm from 1.54 nm by “post-electric-annealing”. The shortened distance was effective in promoting charge injection into the emission layer, leading improvement of the EQE. Full article

(This article belongs to the Special Issue Low-Dimensional Semiconductor Materials: Fabrication, Characterization and Applications)

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21 pages, 4805 KiB

Open AccessEditor’s ChoiceArticle

Conducting Electrospun Nanofibres: Monitoring of Iodine Doping of P3HT through Infrared (IRAV) and Raman (RaAV) Polaron Spectroscopic Features

by Alessia Arrigoni, Luigi Brambilla, Chiara Castiglioni and Chiara Bertarelli

Nanomaterials 2022, 12(23), 4308; https://doi.org/10.3390/nano12234308 - 4 Dec 2022

Cited by 4 | Viewed by 2087

Abstract

Aligned polymer nanofibres are prepared by means of the electrospinning of a chlorobenzene solution containing regioregular poly(3-hexyltiophene-2,5-diyl), P3HT, and poly(ethylene oxide), PEO. The PEO scaffold is easily dissolved with acetonitrile, leaving pure P3HT fibres, which do not show structural modification. Polymer fibres, either [...] Read more.

Aligned polymer nanofibres are prepared by means of the electrospinning of a chlorobenzene solution containing regioregular poly(3-hexyltiophene-2,5-diyl), P3HT, and poly(ethylene oxide), PEO. The PEO scaffold is easily dissolved with acetonitrile, leaving pure P3HT fibres, which do not show structural modification. Polymer fibres, either with or without the PEO supporting polymer, are effectively doped by exposure to iodine vapours. Doping is monitored following the changes in the doping-induced vibrational bands (IRAVs) observed in the infrared spectra and by means of Raman spectroscopy. Molecular orientation inside the fibres has been assessed by means of IR experiments in polarised light, clearly demonstrating that electrospinning induces the orientation of the polymer chains along the fibre axis as well as of the defects introduced by doping. This work illustrates a case study that contributes to the fundamental knowledge of the vibrational properties of the doping-induced defects—charged polarons—of P3HT. Moreover, it provides experimental protocols for a thorough spectroscopic characterisation of the P3HT nanofibres, and of doped conjugated polymers in general, opening the way for the control of the material structure when the doped polymer is confined in a one-dimensional architecture. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Application of Nanofibers)

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11 pages, 2547 KiB

Open AccessEditor’s ChoiceArticle

Silver Nanoparticle Chains for Ultra-Long-Range Plasmonic Waveguides for Nd³⁺ Fluorescence

by Javier Fernández-Martínez, Sol Carretero-Palacios, Pablo Molina, Jorge Bravo-Abad, Mariola O. Ramírez and Luisa E. Bausá

Nanomaterials 2022, 12(23), 4296; https://doi.org/10.3390/nano12234296 - 3 Dec 2022

Cited by 2 | Viewed by 1589

Abstract

Plasmonic waveguides have been shown to be a promising approach to confine and transport electromagnetic energy beyond the diffraction limit. However, ohmic losses generally prevent their integration at micrometric or millimetric scales. Here, we present a gain-compensated plasmonic waveguide based on the integration [...] Read more.

Plasmonic waveguides have been shown to be a promising approach to confine and transport electromagnetic energy beyond the diffraction limit. However, ohmic losses generally prevent their integration at micrometric or millimetric scales. Here, we present a gain-compensated plasmonic waveguide based on the integration of linear chains of Ag nanoparticles on an optically active Nd³⁺-doped solid-state gain medium. By means of dual confocal fluorescence microscopy, we demonstrate long-range optical energy propagation due to the near-field coupling between the plasmonic nanostructures and the Nd³⁺ ions. The subwavelength fluorescence guiding is monitored at distances of around 100 µm from the excitation source for two different emission ranges centered at around 900 nm and 1080 nm. In both cases, the guided fluorescence exhibits a strong polarization dependence, consistent with the polarization behavior of the plasmon resonance supported by the chain. The experimental results are interpreted through numerical simulations in quasi-infinite long chains, which corroborate the propagation features of the Ag nanoparticle chains at both excitation (λ_exc = 590 nm) and emission wavelengths. The obtained results exceed by an order of magnitude that of previous reports on electromagnetic energy transport using linear plasmonic chains. The work points out the potential of combining Ag nanoparticle chains with a small interparticle distance (~2 nm) with rare-earth-based optical gain media as ultra-long-range waveguides with extreme light confinement. The results offer new perspectives for the design of integrated hybrid plasmonic–photonic circuits based on rare-earth-activated solid-state platforms. Full article

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

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11 pages, 1959 KiB

Open AccessEditor’s ChoiceArticle

Dynamic Light Scattering Plus Scanning Electron Microscopy: Usefulness and Limitations of a Simplified Estimation of Nanocellulose Dimensions

by Quim Tarrés, Roberto Aguado, Justin O. Zoppe, Pere Mutjé, Núria Fiol and Marc Delgado-Aguilar

Nanomaterials 2022, 12(23), 4288; https://doi.org/10.3390/nano12234288 - 2 Dec 2022

Cited by 11 | Viewed by 2710

Abstract

Measurements of nanocellulose size usually demand very high-resolution techniques and tedious image processing, mainly in what pertains to the length of nanofibers. Aiming to ease the process, this work assesses a relatively simple method to estimate the dimensions of nanocellulose particles with an [...] Read more.

Measurements of nanocellulose size usually demand very high-resolution techniques and tedious image processing, mainly in what pertains to the length of nanofibers. Aiming to ease the process, this work assesses a relatively simple method to estimate the dimensions of nanocellulose particles with an aspect ratio greater than 1. Nanocellulose suspensions, both as nanofibers and as nanocrystals, are subjected to dynamic light scattering (DLS) and to field-emission scanning electron microscopy (FE-SEM). The former provides the hydrodynamic diameter, as long as the scatter angle and the consistency are adequate. Assays with different angles and concentrations compel us to recommend forward scattering (12.8°) and concentrations around 0.05–0.10 wt %. Then, FE-SEM with magnifications of ×5000–×20,000 generally suffices to obtain an acceptable approximation for the actual diameter, at least for bundles. Finally, length can be estimated by a simple geometric relationship. Regardless of whether they are collected from FE-SEM or DLS, size distributions are generally skewed to lower diameters. Width distributions from FE-SEM, in particular, are well fitted to log-normal functions. Overall, while this method is not valid for the thinnest fibrils or for single, small nanocrystals, it can be useful in lieu of very high-resolution techniques. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials and Nanocomposites)

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11 pages, 2277 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Electrochemical Performance with Dispersion Degree of CNTs in Electrode According to Ultrasonication Process and Slurry Viscosity for Lithium-Ion Battery

by Jaehong Choi, Chaewon Lee, Sungwoo Park, Tom James Embleton, Kyungmok Ko, Mina Jo, Kashif Saleem Saqib, Jeongsik Yun, Minki Jo, Yoonkook Son and Pilgun Oh

Nanomaterials 2022, 12(23), 4271; https://doi.org/10.3390/nano12234271 - 1 Dec 2022

Cited by 6 | Viewed by 3743

Abstract

Lithium-ion batteries (LIBs) continue to dominate the battery market with their efficient energy storage abilities and their ongoing development. However, at high charge/discharge C-rates their electrochemical performance decreases significantly. To improve the power density properties of LIBs, it is important to form a [...] Read more.

Lithium-ion batteries (LIBs) continue to dominate the battery market with their efficient energy storage abilities and their ongoing development. However, at high charge/discharge C-rates their electrochemical performance decreases significantly. To improve the power density properties of LIBs, it is important to form a uniform electron transfer network in the cathode electrode via the addition of conductive additives. Carbon nanotubes (CNTs) with high crystallinity, high electrical conductivity, and high aspect ratio properties have gathered significant interest as cathode electrode conductive additives. However, due to the high aggregational properties of CNTs, it is difficult to form a uniform network for electron transfer within the electrode. In this study, to help fabricate electrodes with well-dispersed CNTs, various electrodes were prepared by controlling (i) the mixing order of the conductive material, binder, and active material, and (ii) the sonication process of the CNTs/NMP solution before the electrode slurry preparation. When the binder was mixed with a well sonicated CNTs/NMP solution, the CNTs uniformly adsorbed to the then added cathode material of LiNi_0.6Co_0.2Mn_0.2O₂ and were well-dispersed to form a flowing uniform network. This electrode fabrication process achieved > 98.74% capacity retention after 50 cycles at 5C via suppressed polarization at high current densities and a more reversible H1-M phase transition of the active material. Our study presents a novel design benchmark for the fabricating of electrodes applying well-dispersed CNTs, which can facilitate the application of LIBs in high current density applications. Full article

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

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12 pages, 2617 KiB

Open AccessEditor’s ChoiceArticle

Dual-Wavelength Forward-Enhanced Directional Scattering and Second Harmonic Enhancement in Open-Hole Silicon Nanoblock

by Xinghua Wang, Yunbao Zheng, Min Ouyang, Haihua Fan, Qiaofeng Dai and Haiying Liu

Nanomaterials 2022, 12(23), 4259; https://doi.org/10.3390/nano12234259 - 30 Nov 2022

Cited by 1 | Viewed by 1626

Abstract

Nanostructures with appropriate sizes can limit light-matter interaction and support electromagnetic multipole resonance. The interaction between light and nanostructures is intimately related to manipulating the direction of scattered light in the far field as well as the electromagnetic field in the near field. [...] Read more.

Nanostructures with appropriate sizes can limit light-matter interaction and support electromagnetic multipole resonance. The interaction between light and nanostructures is intimately related to manipulating the direction of scattered light in the far field as well as the electromagnetic field in the near field. In this paper, we demonstrate dual-wavelength directional forward-scattering enhancement in an individual open-hole silicon nanoblock (OH-SiNB) and simultaneously achieve bulk and surface electromagnetic field localization. The second harmonic generation is enhanced using electromagnetic field localization on the square hole surface. Numerical simulations reveal that the resonance modes, at λ₁ = 800 nm and λ₂ = 1190 nm, approximately satisfy the Kerker condition. In the near field, the magnetic dipole modes at dual wavelength all satisfy the boundary condition that the normal component of the electric displacement is continuous on the square holes surface, thus obtaining the surface electromagnetic field localization. Moreover, highly efficient second harmonic generation can be achieved at dual wavelengths using the surface electromagnetic field localization and the increased surface area of the square holes. Our results provide a new strategy for the integration of nanoantennas and nonlinear optoelectronic devices in optical chips. Full article

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

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9 pages, 3312 KiB

Open AccessEditor’s ChoiceArticle

Surface Oxidation of Cu₂O Nanoparticles by Adsorbed Ammonia

by Siwoo Lee, Ji Won Jang and Young Bok Ryu

Nanomaterials 2022, 12(23), 4242; https://doi.org/10.3390/nano12234242 - 29 Nov 2022

Viewed by 1707

Abstract

Copper-based nanoparticles have been intensively studied owing to their superior antibacterial activity. In this study, cuprous oxide (Cu₂O) nanoparticles were synthesized using two different methods. In particular, two methods for synthesizing copper oxide from NaOH, namely, with and without the addition [...] Read more.

Copper-based nanoparticles have been intensively studied owing to their superior antibacterial activity. In this study, cuprous oxide (Cu₂O) nanoparticles were synthesized using two different methods. In particular, two methods for synthesizing copper oxide from NaOH, namely, with and without the addition of NH₃, were used to adjust the morphology of the nanoparticles. The nanoparticles from the NH₃ and NaOH samples possessed an octahedral morphology. The crystal structure of the samples was confirmed by X-ray diffraction. The size distribution of the NH₃ sample was narrower than that of the NaOH sample. Furthermore, the average size of the NH₃ sample was smaller than that of the NaOH sample. Unexpectedly, the antibacterial activity of the NH₃ sample was found to be lower than that of the NaOH sample. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy revealed that the adsorbed NH₃ caused the surface oxidation of Cu₂O nanoparticles with azide (N₃) formation on surface. Full article

(This article belongs to the Section Biology and Medicines)

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17 pages, 15925 KiB

Open AccessEditor’s ChoiceArticle

Towards Wireless Detection of Surface Modification of Silicon Nanowires by an RF Approach

by Florian Requena, Samuel Ahoulou, Nicolas Barbot, Darine Kaddour, Jean-Marie Nedelec, Thierry Baron and Etienne Perret

Nanomaterials 2022, 12(23), 4237; https://doi.org/10.3390/nano12234237 - 28 Nov 2022

Cited by 3 | Viewed by 1308

Abstract

This paper shows the possibility to detect the presence of grafted molecules on the surface of silicon nanowires with a wireless RF radar approach based on the measurement of the backscattered signal of a resonant structure on which the nanowires are deposited. The [...] Read more.

This paper shows the possibility to detect the presence of grafted molecules on the surface of silicon nanowires with a wireless RF radar approach based on the measurement of the backscattered signal of a resonant structure on which the nanowires are deposited. The measured resonance frequency allows the determination of the intrinsic properties related to temperature and humidity variations, which can be related to the presence of the grafted molecules. Several functionalizations of nanowires have been realized and characterized. For the first time, an RF approach is used to detect significant differences related to the presence of grafted molecules on the surface of nanowires. In addition to detecting their presence, the obtained results show the potential of the radar approach to identify the type of functionalization of nanowires. A set of six different grafted molecules (including octadecyltrichlorosilane, ethynylpyrene, N3) was tested and correctly separated with the proposed approach. Various measurements of the same samples showed a good repeatability which made the approach compatible with the possibility of differentiating the molecules with each other by radar reading. Moreover, discussions about the application of such functionalizations are made to increase the sensibility of sensors using a radar approach. Full article

(This article belongs to the Special Issue Functional Nanomaterials for Sensing and Detection)

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15 pages, 8896 KiB

Open AccessEditor’s ChoiceArticle

On-Chip Reconfigurable and Ultracompact Silicon Waveguide Mode Converters Based on Nonvolatile Optical Phase Change Materials

by Yedeng Fei, Yin Xu, Dongmei Huang, Yue Dong, Bo Zhang, Yi Ni and P. K. A. Wai

Nanomaterials 2022, 12(23), 4225; https://doi.org/10.3390/nano12234225 - 28 Nov 2022

Cited by 5 | Viewed by 2297

Abstract

Reconfigurable mode converters are essential components in efficient higher-order mode sources for on-chip multimode applications. We propose an on-chip reconfigurable silicon waveguide mode conversion scheme based on the nonvolatile and low-loss optical phase change material antimony triselenide (Sb₂Se₃). The [...] Read more.

Reconfigurable mode converters are essential components in efficient higher-order mode sources for on-chip multimode applications. We propose an on-chip reconfigurable silicon waveguide mode conversion scheme based on the nonvolatile and low-loss optical phase change material antimony triselenide (Sb₂Se₃). The key mode conversion region is formed by embedding a tapered Sb₂Se₃ layer into the silicon waveguide along the propagation direction and further cladding with graphene and aluminum oxide layers as the microheater. The proposed device can achieve the TE₀-to-TE₁ mode conversion and reconfigurable conversion (no mode conversion) depending on the phase state of embedded Sb₂Se₃ layer, whereas such function could not be realized according to previous reports. The proposed device length is only 2.3 μm with conversion efficiency (CE) = 97.5%, insertion loss (IL) = 0.2 dB, and mode crosstalk (CT) = −20.5 dB. Furthermore, the proposed device scheme can be extended to achieve other reconfigurable higher-order mode conversions. We believe the proposed reconfigurable mode conversion scheme and related devices could serve as the fundamental building blocks to provide higher-order mode sources for on-chip multimode photonics. Full article

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

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13 pages, 3193 KiB

Open AccessEditor’s ChoiceArticle

Valorization of Sugarcane By-Products through Synthesis of Biogenic Amorphous Silica Microspheres for Sustainable Cosmetics

by Joana R. Costa, Ana Paula Capeto, Carla F. Pereira, Sílvia S. Pedrosa, Inês F. Mota, João da Silva Burgal, Ana I. Pintado, Manuela E. Pintado, Catarina S. S. Oliveira, Patrícia Costa and Ana Raquel Madureira

Nanomaterials 2022, 12(23), 4201; https://doi.org/10.3390/nano12234201 - 26 Nov 2022

Cited by 6 | Viewed by 2095

Abstract

Ashes from sugarcane by-product incineration were used to synthesize silica powders through alkaline hot extraction, followed by ethanol/acid precipitation or the sol–gel method. Both production methods allowed amorphous spherical silica microparticles with sizes ranging from 1–15 μm and 97% purity to be obtained. [...] Read more.

Ashes from sugarcane by-product incineration were used to synthesize silica powders through alkaline hot extraction, followed by ethanol/acid precipitation or the sol–gel method. Both production methods allowed amorphous spherical silica microparticles with sizes ranging from 1–15 μm and 97% purity to be obtained. Water absorption ranged from 135–155 mL/100 g and 150–250 mL/100 g for precipitated silica and silica gel, respectively, while oil absorption ranged from 305 to 390 and from 250 to 350 mL/100 g. The precipitation with ethanol allowed the recovery of 178 g silica/kg ash, with a lab process cost of EUR 28.95/kg, while the sol-gel process showed a yield of 198 g silica/kg ash with a cost of EUR 10.89/kg. The experimental data suggest that ash from sugarcane by-products is a promising source to be converted into a competitive value-added product, minimizing the environmental impact of disposal problems. Full article

(This article belongs to the Special Issue Micro and Nanomaterials in Cosmetics)

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16 pages, 4193 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Development and Characterisation of a Whole Hybrid Sol-Gel Optofluidic Platform for Biosensing Applications

by Emma MacHugh, Graceson Antony, Arun Kumar Mallik, Alicja Kaworek, Declan McCormack, Brendan Duffy and Mohamed Oubaha

Nanomaterials 2022, 12(23), 4192; https://doi.org/10.3390/nano12234192 - 25 Nov 2022

Cited by 3 | Viewed by 1740

Abstract

This work outlines, for the first time, the fabrication of a whole hybrid sol-gel optofluidic platform by integrating a microfluidic biosensor platform with optical waveguides employing a standard photolithography process. To demonstrate the suitability of this new hybrid sol-gel optofluidic platform, optical and [...] Read more.

This work outlines, for the first time, the fabrication of a whole hybrid sol-gel optofluidic platform by integrating a microfluidic biosensor platform with optical waveguides employing a standard photolithography process. To demonstrate the suitability of this new hybrid sol-gel optofluidic platform, optical and bio-sensing proof-of-concepts are proposed. A photoreactive hybrid sol-gel material composed of a photopolymerisable organically modified silicon alkoxide and a transition metal complex was prepared and used as the fabrication material for the entire optofluidic platform, including the optical waveguides, the sensing areas, and the microfluidic device. The most suitable sol-gel materials chosen for the fabrication of the cladding and core of the waveguides showed a RIC of 3.5 × 10⁻³ and gave thicknesses between 5.5 and 7 μm. The material was optimised to simultaneously meet the photoreactive properties required for the photolithography fabrication process and the optical properties needed for the effective optical operability of the microstructured waveguides at 532 and 633 nm with an integrated microfluidic device. The optical proof-of-concept was performed using a fluorescent dye (Atto 633) and recording its optical responses while irradiated with a suitable optical excitation. The biosensing capability of the platform was assessed using a polyclonal primary IgG mouse antibody and a fluorescent labelled secondary IgG anti-mouse antibody. A limit of detection (LOD) of 50 ug/mL was achieved. A correlation between the concentration of the dye and the emission fluorescence was evidenced, thus clearly demonstrating the feasibility of the proposed hybrid sol-gel optofluidic platform concept. The successful integration and operability of optical and microfluidic components in the same optofluidic platform is a novel concept, particularly where the sol-gel fabrication material is concerned. Full article

(This article belongs to the Special Issue Eco-Friendly Microdevice Printing Techniques with Functional Nano/Biomaterials)

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15 pages, 1589 KiB

Open AccessEditor’s ChoiceArticle

Effect of Silica-Based Nanomaterials on Seed Germination and Seedling Growth of Rice (Oryza sativa L.)

by Yaqi Jiang, Jie Yang, Mingshu Li, Yuanbo Li, Pingfan Zhou, Quanlong Wang, Yi Sun, Guikai Zhu, Qibin Wang, Peng Zhang, Yukui Rui and Iseult Lynch

Nanomaterials 2022, 12(23), 4160; https://doi.org/10.3390/nano12234160 - 24 Nov 2022

Cited by 12 | Viewed by 2647

Abstract

The application of nanomaterials (NMs) in agriculture has become a global concern in recent years. However, studies on their effects on plants are still limited. Here, we conducted a seed germination experiment for 5 days and a hydroponics experiment for 14 days to [...] Read more.

The application of nanomaterials (NMs) in agriculture has become a global concern in recent years. However, studies on their effects on plants are still limited. Here, we conducted a seed germination experiment for 5 days and a hydroponics experiment for 14 days to study the effects of silicon dioxide NMs(nSiO₂) and silicon carbide NMs(nSiC) (0,10, 50, 200 mg/L) on rice (Oryza sativa L.). Bulk SiO₂ (bSiO₂) and sodium silicate (Na₂SiO₃) were used as controls. The results showed that nSiO₂ and nSiC increased the shoot length (11–37%, 6–25%) and root length (17–87%, 59–207%) of germinating seeds, respectively, compared with the control. Similarly, inter-root exposure to nSiO₂, bSiO_2, and nSiC improved the activity of aboveground catalase (10–55%, 31–34%, and 13–51%) and increased the content of trace elements magnesium, copper, and zinc, thus promoting the photosynthesis of rice. However, Na₂SiO₃ at a concentration of 200 mg/L reduced the aboveground and root biomass of rice by 27–51% and 4–17%, respectively. This may be because excess silicon not only inhibited the activity of root antioxidant enzymes but also disrupted the balance of mineral elements. This finding provides a new basis for the effect of silica-based NMs promotion on seed germination and rice growth. Full article

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11 pages, 2068 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

High-Reliability Perovskite Quantum Dots Using Atomic Layer Deposition Passivation for Novel Photonic Applications

by Tzu-Yi Lee, Tsau-Hua Hsieh, Wen-Chien Miao, Konthoujam James Singh, Yiming Li, Chang-Ching Tu, Fang-Chung Chen, Wen-Chung Lu and Hao-Chung Kuo

Nanomaterials 2022, 12(23), 4140; https://doi.org/10.3390/nano12234140 - 23 Nov 2022

Cited by 6 | Viewed by 2344

Abstract

In this study, we propose highly stable perovskite quantum dots (PQDs) coated with Al₂O₃ using atomic layer deposition (ALD) passivation technology. This passivation layer effectively protects the QDs from moisture infiltration and oxidation as well as from high temperatures and [...] Read more.

In this study, we propose highly stable perovskite quantum dots (PQDs) coated with Al₂O₃ using atomic layer deposition (ALD) passivation technology. This passivation layer effectively protects the QDs from moisture infiltration and oxidation as well as from high temperatures and any changes in the material characteristics. They exhibit excellent wavelength stability and reliability in terms of current variation tests, long-term light aging tests, and temperature/humidity tests (60°/90%). A white-light system has been fabricated by integrating a micro-LED and red phosphor exhibiting a high data transmission rate of 1 Gbit/s. These results suggest that PeQDs treated with ALD passivation protection offer promising prospects in full-color micro-displays and high-speed visible-light communication (VLC) applications. Full article

(This article belongs to the Special Issue Quantum Dots and Micro-LED Display 2.0)

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14 pages, 13242 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Characterization of Two-Segment Free-Standing ZnO Nanowires Using Lateral Force Microscopy

by János Volk, János Radó, Zsófia Baji and Róbert Erdélyi

Nanomaterials 2022, 12(23), 4120; https://doi.org/10.3390/nano12234120 - 22 Nov 2022

Viewed by 1236

Abstract

Mechanical characterization of quasi one-dimensional nanostructures is essential for the design of novel nanoelectromechanical systems. However, the results obtained on basic mechanical quantities, such as Young’s modulus and fracture strength, show significant standard deviation in the literature. This is partly because of diversity [...] Read more.

Mechanical characterization of quasi one-dimensional nanostructures is essential for the design of novel nanoelectromechanical systems. However, the results obtained on basic mechanical quantities, such as Young’s modulus and fracture strength, show significant standard deviation in the literature. This is partly because of diversity in the quality of the nanowire, and partly because of inappropriately performed mechanical tests and simplified mechanical models. Here we present orientation-controlled bending and fracture studies on wet chemically grown vertical ZnO nanowires, using lateral force microscopy. The lateral force signal of the atomic force microscope was calibrated by a diamagnetic levitation spring system. By acquiring the bending curves of 14 nanowires, and applying a two-segment mechanical model, an average bending modulus of 108 ± 17 GPa was obtained, which was 23% lower than the Young’s modulus of bulk ZnO in the [0001] direction. It was also found that the average fracture strain and stress inside the nanowire was above 3.1 ± 0.3 % and 3.3 ± 0.3 GPa, respectively. However, the fracture of the nanowires was governed by the quality of the nanowire/substrate interface. The demonstrated technique is a relatively simple and productive way for the accurate mechanical characterization of vertical nanowire arrays. Full article

(This article belongs to the Special Issue Low-Dimensional Semiconductor Materials: Fabrication, Characterization and Applications)

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12 pages, 3085 KiB

Open AccessEditor’s ChoiceArticle

Ethanol Electrooxidation at 1–2 nm AuPd Nanoparticles

by Juliette W. Strasser and Richard M. Crooks

Nanomaterials 2022, 12(22), 4093; https://doi.org/10.3390/nano12224093 - 21 Nov 2022

Cited by 2 | Viewed by 1331

Abstract

We report a systematic study of the electrocatalytic properties and stability of a series of 1–2 nm Au, Pd, and AuPd alloy nanoparticles (NPs) for the ethanol oxidation reaction (EOR). Following EOR electrocatalysis, NP sizes and compositions were characterized using aberration-corrected scanning transmission [...] Read more.

We report a systematic study of the electrocatalytic properties and stability of a series of 1–2 nm Au, Pd, and AuPd alloy nanoparticles (NPs) for the ethanol oxidation reaction (EOR). Following EOR electrocatalysis, NP sizes and compositions were characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and energy dispersive spectroscopy (EDS). Two main findings emerge from this study. First, alloyed AuPd NPs exhibit enhanced electrocatalytic EOR activity compared to either monometallic Au or Pd NPs. Specifically, NPs having a 3:1 ratio of Au:Pd exhibit an ~8-fold increase in peak current density compared to Pd NPs, with an onset potential shifted ~200 mV more to the negative compared to Au NPs. Second, the size and composition of AuPd alloy NPs do not (within experimental error) change following 1.0 or 2.0 h chronoamperometry experiments, while monometallic Au NPs increase in size from 2 to 5 nm under the same conditions. Notably, this report demonstrates the importance of post-catalytic ac-STEM/EDS characterization for fully evaluating NP activity and stability, especially for 1–2 nm NPs that may change in size or structure during electrocatalysis. Full article

(This article belongs to the Special Issue Nanomaterials and Nanotechnology for Electrocatalytic Applications)

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17 pages, 4515 KiB

Open AccessEditor’s ChoiceArticle

Cascade Förster Resonance Energy Transfer Studies for Enhancement of Light Harvesting on Dye-Sensitized Solar Cells

by Mulugeta Tesema Efa, Jheng-Chang Huang and Toyoko Imae

Nanomaterials 2022, 12(22), 4085; https://doi.org/10.3390/nano12224085 - 20 Nov 2022

Cited by 4 | Viewed by 1755

Abstract

This work reports cascade Förster resonance energy transfer (FRET)-based n-type (ZnO) and p-type (NiO) dye-sensitized solar cells (DSSCs), discussing approaches to enhance their overall performance. Although DSSCs suffer from poorer performance than other solar cells, the use of composites with carbon dot (Cdot) [...] Read more.

This work reports cascade Förster resonance energy transfer (FRET)-based n-type (ZnO) and p-type (NiO) dye-sensitized solar cells (DSSCs), discussing approaches to enhance their overall performance. Although DSSCs suffer from poorer performance than other solar cells, the use of composites with carbon dot (Cdot) can enhance the power conversion efficiency (PCE) of DSSCs. However, further improvements are demanded through molecular design to stimulate DSSCs. Here, a photosensitized system based on a cascade FRET was induced alongside the conventional photosensitizer dye (N719). To N719 in a DSSC is transferred the energy cascaded through donor fluorescence materials (pyrene, 3-acetyl-7-N,N-diethyl-coumarin or coumarin and acridine orange), and this process enhances the light-harvesting properties of the sensitizers in the DSSC across a broad region of the solar spectrum. PCE values of 10.7 and 11.3% were achieved for ZnO/Cdot and NiO/Cdot DSSCs, respectively. These high PCE values result from the energy transfer among multi-photosensitizers (cascade FRET fluorophores, N719, and Cdot). Moreover, Cdot can play a role in intensifying the adsorption of dyes and discouraging charge recombination on the semiconductor. The present results raise expectations that a significant improvement in photovoltaic performance can be attained of DSSCs exploiting the cascade FRET photonics phenomenon. Full article

(This article belongs to the Special Issue Quantum Materials for Photonic Devices)

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22 pages, 4191 KiB

Open AccessEditor’s ChoiceReview

Application of Peptides in Construction of Nonviral Vectors for Gene Delivery

by Yujie Yang, Zhen Liu, Hongchao Ma and Meiwen Cao

Nanomaterials 2022, 12(22), 4076; https://doi.org/10.3390/nano12224076 - 19 Nov 2022

Cited by 4 | Viewed by 2109

Abstract

Gene therapy, which aims to cure diseases by knocking out, editing, correcting or compensating abnormal genes, provides new strategies for the treatment of tumors, genetic diseases and other diseases that are closely related to human gene abnormalities. In order to deliver genes efficiently [...] Read more.

Gene therapy, which aims to cure diseases by knocking out, editing, correcting or compensating abnormal genes, provides new strategies for the treatment of tumors, genetic diseases and other diseases that are closely related to human gene abnormalities. In order to deliver genes efficiently to abnormal sites in vivo to achieve therapeutic effects, a variety of gene vectors have been designed. Among them, peptide-based vectors show superior advantages because of their ease of design, perfect biocompatibility and safety. Rationally designed peptides can carry nucleic acids into cells to perform therapeutic effects by overcoming a series of biological barriers including cellular uptake, endosomal escape, nuclear entrance and so on. Moreover, peptides can also be incorporated into other delivery systems as functional segments. In this review, we referred to the biological barriers for gene delivery in vivo and discussed several kinds of peptide-based nonviral gene vectors developed for overcoming these barriers. These vectors can deliver different types of genetic materials into targeted cells/tissues individually or in combination by having specific structure–function relationships. Based on the general review of peptide-based gene delivery systems, the current challenges and future perspectives in development of peptidic nonviral vectors for clinical applications were also put forward, with the aim of providing guidance towards the rational design and development of such systems. Full article

(This article belongs to the Special Issue Nanomaterials for Chemical Engineering)

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20 pages, 5067 KiB

Open AccessEditor’s ChoiceArticle

High-Performance Room-Temperature NO₂ Gas Sensor Based on Au-Loaded SnO₂ Nanowires under UV Light Activation

by Bo Zhang, Shuai Zhang, Yi Xia, Pingping Yu, Yin Xu, Yue Dong, Qufu Wei and Jing Wang

Nanomaterials 2022, 12(22), 4062; https://doi.org/10.3390/nano12224062 - 18 Nov 2022

Cited by 11 | Viewed by 2516

Abstract

Optical excitation is widely acknowledged as one of the most effective means of balancing sensor responses and response/recovery properties at room temperature (RT, 25 °C). Moreover, noble metals have been proven to be suitable as photosensitizers for optical excitation. Localized surface plasmon resonance [...] Read more.

Optical excitation is widely acknowledged as one of the most effective means of balancing sensor responses and response/recovery properties at room temperature (RT, 25 °C). Moreover, noble metals have been proven to be suitable as photosensitizers for optical excitation. Localized surface plasmon resonance (LSPR) determines the liberalization of quasi-free electrons in noble metals under light irradiation, and numerous injected electrons in semiconductors will greatly promote the generation of chemisorbed oxygen, thus elevating the sensor response. In this study, pure SnO₂ and Au/SnO₂ nanowires (NWs) were successfully synthesized through the electrospinning method and validated using XRD, EDS, HRTEM, and XPS. Although a Schottky barrier led to a much higher initial resistance of the Au/SnO₂ composite compared with pure SnO₂ at RT in the dark, the photoinduced resistance of the Au/SnO₂ composite became lower than that of pure SnO₂ under UV irradiation with the same intensity, which confirmed the effect of LSPR. Furthermore, when used as sensing materials, a detailed comparison between the sensing properties of pure SnO₂ and Au/SnO₂ composite toward NO₂ in the dark and under UV irradiation highlighted the crucial role of the LSPR effects. In particular, the response of Au/SnO₂ NWs toward 5 ppm NO₂ could reach 65 at RT under UV irradiation, and the response/recovery time was only 82/42 s, which far exceeded those under Au modification-only or optical excitation-only. Finally, the gas-sensing mechanism corresponding to the change in sensor performance in each case was systematically proposed. Full article

(This article belongs to the Topic Advanced Nanomaterials for Sensing Applications)

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11 pages, 4958 KiB

Open AccessEditor’s ChoiceArticle

Omnidirectional Triboelectric Nanogenerator for Wide-Speed-Range Wind Energy Harvesting

by Qiman Wang, Wenhao Li, Kun Wang, Yitao Liao, Junjie Zheng, Xiongtu Zhou, Jianpu Lin, Yongai Zhang and Chaoxing Wu

Nanomaterials 2022, 12(22), 4046; https://doi.org/10.3390/nano12224046 - 17 Nov 2022

Cited by 3 | Viewed by 2120

Abstract

The environmentally friendly harvesting of wind energy is an effective technique for achieving carbon neutrality and a green economy. In this work, a core–shell triboelectric nanogenerator (CS-TENG) for harvesting wind energy is demonstrated and the device structure parameters are optimized. The core–shell structure [...] Read more.

The environmentally friendly harvesting of wind energy is an effective technique for achieving carbon neutrality and a green economy. In this work, a core–shell triboelectric nanogenerator (CS-TENG) for harvesting wind energy is demonstrated and the device structure parameters are optimized. The core–shell structure enables the CS-TENG to respond sensitively to wind from any direction and generate electrical output on the basis of the vertical contact–separation mode. A single device can generate a maximum power density of 0.14 W/m³ and can power 124 light-emitting diodes. In addition, wind energy can be harvested even at a wind speed as low as 2.3 m/s by paralleling CS-TENGs of different sizes. Finally, a self-powered water quality testing system that uses the CS-TENG as its power supply is built. The CS-TENG exhibits the advantages of a simple structure, environmentally friendly materials, low cost, and simple fabrication process. These features are of considerable significance for the development of green energy harvesting devices. Full article

(This article belongs to the Special Issue Nanogenerators and Self-Powered Systems)

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12 pages, 1023 KiB

Open AccessEditor’s ChoiceArticle

Hydrogenated Boron Phosphide THz-Metamaterial-Based Biosensor for Diagnosing COVID-19: A DFT Coupled FEM Study

by Chunjian Tan, Shaogang Wang, Huiru Yang, Qianming Huang, Shizhen Li, Xu Liu, Huaiyu Ye and Guoqi Zhang

Nanomaterials 2022, 12(22), 4024; https://doi.org/10.3390/nano12224024 - 16 Nov 2022

Cited by 2 | Viewed by 1749

Abstract

Recent reports focus on the hydrogenation engineering of monolayer boron phosphide and simultaneously explore its promising applications in nanoelectronics. Coupling density functional theory and finite element method, we investigate the bowtie triangle ring microstructure composed of boron phosphide with hydrogenation based on structural [...] Read more.

Recent reports focus on the hydrogenation engineering of monolayer boron phosphide and simultaneously explore its promising applications in nanoelectronics. Coupling density functional theory and finite element method, we investigate the bowtie triangle ring microstructure composed of boron phosphide with hydrogenation based on structural and performance analysis. We determine the carrier mobility of hydrogenated boron phosphide, reveal the effect of structural and material parameters on resonance frequencies, and discuss the variation of the electric field at the two tips. The results suggest that the mobilities of electrons for hydrogenated BP monolayer in the armchair and zigzag directions are 0.51 and 94.4 cm²·V

^{- 1}

·s

^{- 1}

, whereas for holes, the values are 136.8 and 175.15 cm²·V

^{- 1}

·s

^{- 1}

. Meanwhile, the transmission spectra of the bowtie triangle ring microstructure can be controlled by adjusting the length of the bowtie triangle ring microstructure and carrier density of hydrogenated BP. With the increasing length, the transmission spectrum has a red-shift and the electric field at the tips of equilateral triangle rings is significantly weakened. Furthermore, the theoretical sensitivity of the BTR structure reaches 100 GHz/RIU, which is sufficient to determine healthy and COVID-19-infected individuals. Our findings may open up new avenues for promising applications in the rapid diagnosis of COVID-19. Full article

(This article belongs to the Special Issue Computational Modeling and Simulation for Nanomaterials, Nanotechnology, and Nanoscience - II)

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23 pages, 4588 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Targeting Ultrasmall Gold Nanoparticles with cRGD Peptide Increases the Uptake and Efficacy of Cytotoxic Payload

by Richard D. Perrins, Lee-Anne McCarthy, Angela Robinson, Kelly L. Spry, Valentin Cognet, Avelino Ferreira, John Porter, Cristina Espinosa Garcίa, Miguel Ángel Rodriguez, Diana Lopez, Ibon Perera, Kelly Conlon, Africa Barrientos, Tom Coulter, Alessandro Pace, Sarah J. M. Hale, Enrico Ferrari and Csanad Z. Bachrati

Nanomaterials 2022, 12(22), 4013; https://doi.org/10.3390/nano12224013 - 15 Nov 2022

Cited by 6 | Viewed by 2894

Abstract

Cyclic arginyl-glycyl-aspartic acid peptide (cRGD) peptides show a high affinity towards αVβ3 integrin, a receptor overexpressed in many cancers. We aimed to combine the versatility of ultrasmall gold nanoparticles (usGNP) with the target selectivity of cRGD peptide for the directed delivery of a [...] Read more.

Cyclic arginyl-glycyl-aspartic acid peptide (cRGD) peptides show a high affinity towards αVβ3 integrin, a receptor overexpressed in many cancers. We aimed to combine the versatility of ultrasmall gold nanoparticles (usGNP) with the target selectivity of cRGD peptide for the directed delivery of a cytotoxic payload in a novel design. usGNPs were synthesized with a modified Brust-Schiffrin method and functionalized via amide coupling and ligand exchange and their uptake, intracellular trafficking, and toxicity were characterized. Our cRGD functionalized usGNPs demonstrated increased cellular uptake by αVβ3 integrin expressing cells, are internalized via clathrin-dependent endocytosis, accumulated in the lysosomes, and when loaded with mertansine led to increased cytotoxicity. Targeting via cRGD functionalization provides a mechanism to improve the efficacy, tolerability, and retention of therapeutic GNPs. Full article

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

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13 pages, 2698 KiB

Open AccessEditor’s ChoiceArticle

Influence of Cocatalysts (Ni, Co, and Cu) and Synthesis Method on the Photocatalytic Activity of Exfoliated Graphitic Carbon Nitride for Hydrogen Production

by Adeem Ghaffar Rana, Michael Schwarze, Minoo Tasbihi, Xavier Sala, Jordi García-Antón and Mirjana Minceva

Nanomaterials 2022, 12(22), 4006; https://doi.org/10.3390/nano12224006 - 14 Nov 2022

Cited by 5 | Viewed by 2437

Abstract

Exfoliated graphitic carbon nitride (ex-g-CN) was synthesized and loaded with non-noble metals (Ni, Cu, and Co). The synthesized catalysts were tested for hydrogen production using a 300-W Xe lamp equipped with a 395 nm cutoff filter. A noncommercial double-walled quartz-glass reactor irradiated from [...] Read more.

Exfoliated graphitic carbon nitride (ex-g-CN) was synthesized and loaded with non-noble metals (Ni, Cu, and Co). The synthesized catalysts were tested for hydrogen production using a 300-W Xe lamp equipped with a 395 nm cutoff filter. A noncommercial double-walled quartz-glass reactor irradiated from the side was used with a 1 g/L catalyst in 20 mL of a 10 vol% triethanolamine aqueous solution. For preliminary screening, the metal-loaded ex-g-CN was synthesized using the incipient wetness impregnation method. The highest hydrogen production was observed on the Ni-loaded ex-g-CN, which was selected to assess the impact of the synthesis method on hydrogen production. Ni-loaded ex-g-CN was synthesized using different synthesis methods: incipient wetness impregnation, colloidal deposition, and precipitation deposition. The catalysts were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption using the Brunauer–Emmett–Teller method, and transmission electron microscopy. The Ni-loaded ex-g-CN synthesized using the colloidal method performed best with a hydrogen production rate of 43.6 µmol h⁻¹ g⁻¹. By contrast, the catalysts synthesized using the impregnation and precipitation methods were less active, with 28.2 and 10.1 µmol h⁻¹ g⁻¹, respectively. The hydrogen production performance of the suspended catalyst (440 µmol m⁻² g⁻¹) showed to be superior to that of the corresponding immobilized catalyst (236 µmol m⁻² g⁻¹). Full article

(This article belongs to the Special Issue Environmental Remediation by Photocatalytic Functional Nanomaterials)

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22 pages, 4560 KiB

Open AccessEditor’s ChoiceArticle

Influence of Tartrate Ligand Coordination over Luminescence Properties of Chiral Lanthanide-Based Metal–Organic Frameworks

by Uxua Huizi-Rayo, Xuban Gastearena, Ana M. Ortuño, Juan M. Cuerva, Antonio Rodríguez-Diéguez, Jose Angel García, Jesus Ugalde, Jose Manuel Seco, Eider San Sebastian and Javier Cepeda

Nanomaterials 2022, 12(22), 3999; https://doi.org/10.3390/nano12223999 - 13 Nov 2022

Viewed by 2167

Abstract

The present work reports on a detailed discussion about the synthesis, characterization, and luminescence properties of three pairs of enantiopure 3D metal–organic frameworks (MOFs) with general formula {[Ln₂(L/D-tart)₃(H₂O)₂]·3H₂O}_n (3D_Ln-L/D, where [...] Read more.

The present work reports on a detailed discussion about the synthesis, characterization, and luminescence properties of three pairs of enantiopure 3D metal–organic frameworks (MOFs) with general formula {[Ln₂(L/D-tart)₃(H₂O)₂]·3H₂O}_n (3D_Ln-L/D, where Ln = Sm(III), Eu(III) or Gd(III), and L/D-tart = L- or D-tartrate), and ten pairs of enantiopure 2D coordination polymers (CPs) with general formula [Ln(L/D-Htart)₂(OH)(H₂O)₂]_n (2D_Ln-L/D, where Ln = Y(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III) or Yb(III), and L/D-Htart = hydrogen L- or D-tartrate) based on single-crystal X-ray structures. Enantiopure nature of the samples has been further corroborated by Root Mean Square Deviation (RMSD) as well as by circular dichroism (CD) spectra. Solid-state emission spectra of Eu(III), Tb(III), and Dy(III)-based compounds confirm the occurrence of ligand-to-metal charge transfers in view of the characteristic emissions for these lanthanide ions, and emission decay curves were also recorded to estimate the emission lifetimes for the reported compounds. A complete theoretical study was accomplished to better understand the energy transfers occurring in the Eu-based counterparts, which allows for explaining the different performances of 3D-MOFs and 2D-layered compounds. As inferred from the colorimetric diagrams, emission characteristics of Eu-based 2D CPs depend on the temperature, so their luminescent thermometry has been determined on the basis of a ratiometric analysis between the ligand-centered and Eu-centered emission. Finally, a detailed study of the polarized luminescence intensity emitted by the samples is also accomplished to support the occurrence of chiro-optical activity. Full article

(This article belongs to the Special Issue Lanthanide-Doped Luminescent Nanomaterials: Design, Synthesis, Optical Properties and Applications)

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10 pages, 2287 KiB

Open AccessEditor’s ChoiceArticle

Complete Solution-Processed Semitransparent and Flexible Organic Solar Cells: A Success of Polyimide/Ag-Nanowires- and PH1000-Based Electrodes with Plasmonic Enhanced Light Absorption

by Jing Wang, Xiangfei Liang, Jianing Xie, Xiaolong Yin, Jinhao Chen, Tianfu Gu, Yueqi Mo, Jianqing Zhao, Shumei Liu, Donghong Yu, Jibin Zhang and Lintao Hou

Nanomaterials 2022, 12(22), 3987; https://doi.org/10.3390/nano12223987 - 12 Nov 2022

Cited by 5 | Viewed by 2073

Abstract

Organic solar cells (OSCs) have been widely studied due to the advantages of easy fabrication, low cost, light weight, good flexibility and sufficient transparency. In this work, flexible and semitransparent OSCs were successfully fabricated with the adoption of both polyimide/silver nanowires (PI/AgNW) and [...] Read more.

Organic solar cells (OSCs) have been widely studied due to the advantages of easy fabrication, low cost, light weight, good flexibility and sufficient transparency. In this work, flexible and semitransparent OSCs were successfully fabricated with the adoption of both polyimide/silver nanowires (PI/AgNW) and a conducting polymer PEDOT:PSS named PH1000 as the transparent conductive electrodes (TCEs). It is demonstrated that PI/AgNW is more suitable as a cathode rather than an anode in the viewpoint of its work function, photovoltaic performance, and simulations of optical properties. It is also found that the light incidence from PH1000 TCE can produce more plasmonic-enhanced photon absorption than the PI/AgNW electrode does, resulting in more high power conversion efficiency. Moreover, a high light transmittance of 33.8% and a decent efficiency of 3.88% are achieved for the whole all-flexible semitransparent device with only 9% decrease of resistance in PI/AgNW after 3000 bending cycles. This work illustrates that PI/AgNW has great potential and bright prospect in large-area OSC applications in the future. Full article

(This article belongs to the Special Issue Nanotechnology and Renewable Energy)

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22 pages, 2994 KiB

Open AccessEditor’s ChoiceArticle

Lanthanide(III) Ions and 5-Methylisophthalate Ligand Based Coordination Polymers: An Insight into Their Photoluminescence Emission and Chemosensing for Nitroaromatic Molecules

by Oier Pajuelo-Corral, Laura Razquin-Bobillo, Sara Rojas, Jose Angel García, Duane Choquesillo-Lazarte, Alfonso Salinas-Castillo, Ricardo Hernández, Antonio Rodríguez-Diéguez and Javier Cepeda

Nanomaterials 2022, 12(22), 3977; https://doi.org/10.3390/nano12223977 - 11 Nov 2022

Cited by 4 | Viewed by 2295

Abstract

The work presented herein reports on the synthesis, structural and physico-chemical characterization, luminescence properties and luminescent sensing activity of a family of isostructural coordination polymers (CPs) with the general formula [Ln₂(μ₄-5Meip)₃(DMF)]_n (where Ln(III) = Sm ( [...] Read more.

The work presented herein reports on the synthesis, structural and physico-chemical characterization, luminescence properties and luminescent sensing activity of a family of isostructural coordination polymers (CPs) with the general formula [Ln₂(μ₄-5Meip)₃(DMF)]_n (where Ln(III) = Sm (1_Sm), Eu (2_Eu), Gd (3_Gd), Tb (4_Tb) and Yb (5_Yb) and 5Meip = 5-methylisophthalate, DMF = N,N-dimethylmethanamide). Crystal structures consist of 3D frameworks tailored by the linkage between infinite lanthanide(III)-carboxylate rods by means of the tetradentate 5Meip ligands. Photoluminescence measurements in solid state at variable temperatures reveal the best-in-class properties based on the capacity of the 5Meip ligand to provide efficient energy transfers to the lanthanide(III) ions, which brings intense emissions in both the visible and near-infrared (NIR) regions. On the one hand, compound 5_Yb displays characteristic lanthanide-centered bands in the NIR with sizeable intensity even at room temperature. Among the compounds emitting in the visible region, 4_Tb presents a high QY of 63%, which may be explained according to computational calculations. At last, taking advantage of the good performance as well as high chemical and optical stability of 4_Tb in water and methanol, its sensing capacity to detect 2,4,6-trinitrophenol (TNP) among other nitroaromatic-like explosives has been explored, obtaining high detection capacity (with K_sv around 10⁵ M⁻¹), low limit of detection (in the 10⁻⁶–10⁻⁷ M) and selectivity among other molecules (especially in methanol). Full article

(This article belongs to the Special Issue Theoretical Calculation and Molecular Modeling of Nanomaterials)

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17 pages, 2416 KiB

Open AccessEditor’s ChoiceArticle

Surface Versus Bulk State Transitions in Inkjet-Printed All-Inorganic Perovskite Quantum Dot Films

by Thilini K. Ekanayaka, Dylan Richmond, Mason McCormick, Shashank R. Nandyala, Halle C. Helfrich, Alexander Sinitskii, Jon M. Pikal, Carolina C. Ilie, Peter A. Dowben and Andrew J. Yost

Nanomaterials 2022, 12(22), 3956; https://doi.org/10.3390/nano12223956 - 10 Nov 2022

Cited by 2 | Viewed by 1885

Abstract

The anion exchange of the halides, Br and I, is demonstrated through the direct mixing of two pure perovskite quantum dot solutions, CsPbBr₃ and CsPbI₃, and is shown to be both facile and result in a completely alloyed single phase [...] Read more.

The anion exchange of the halides, Br and I, is demonstrated through the direct mixing of two pure perovskite quantum dot solutions, CsPbBr₃ and CsPbI₃, and is shown to be both facile and result in a completely alloyed single phase mixed halide perovskite. Anion exchange is also observed in an interlayer printing method utilizing the pure, unalloyed perovskite solutions and a commercial inkjet printer. The halide exchange was confirmed by optical absorption spectroscopy, photoluminescent spectroscopy, X-ray diffraction, and X-ray photoemission spectroscopy characterization and indicates that alloying is thermodynamically favorable, while the formation of a clustered alloy is not favored. Additionally, a surface-to-bulk photoemission core level transition is observed for the Cs 4d photoemission feature, which indicates that the electronic structure of the surface is different from the bulk. Time resolved photoluminescence spectroscopy indicates the presence of multiple excitonic decay features, which is argued to originate from states residing at surface and bulk environments. Full article

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

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11 pages, 3128 KiB

Open AccessEditor’s ChoiceArticle

Bowtie Nanoantenna Coupled Metal-Oxide-Silicon (p-Doped) Diode for 28.3 THz IR Rectification

by Nasim Al Islam and Sangjo Choi

Nanomaterials 2022, 12(22), 3940; https://doi.org/10.3390/nano12223940 - 9 Nov 2022

Cited by 3 | Viewed by 1918

Abstract

Low-temperature waste heat in the infrared (IR) wavelength region offers an opportunity to harvest power from waste energy and requires further investigation in order to find efficient conversion techniques. Although grating-coupled metal-oxide-semiconductor (MOS) diode devices offer efficient conversion from low and moderate-temperature thermal [...] Read more.

Low-temperature waste heat in the infrared (IR) wavelength region offers an opportunity to harvest power from waste energy and requires further investigation in order to find efficient conversion techniques. Although grating-coupled metal-oxide-semiconductor (MOS) diode devices offer efficient conversion from low and moderate-temperature thermal sources, the integration of such diodes with a nanoantenna structure has yet to be explored. We propose a bowtie nanoantenna coupled with a p-doped MOS diode for IR to direct current (DC) conversion without any bias voltage at 28.3 THz. The nanoantenna was designed and optimized to provide maximum field enhancement in a 4 nm-thick oxide layer at the resonant frequency. The device was fabricated following the complementary MOS (CMOS) fabrication process and measured in a custom DC and optical characterization setup using a 10.6 μm wavelength CO₂ laser. The results reveal two different types of devices with linear and nonlinear I-V curves having kΩ and MΩ zero-bias resistance, respectively. The linear device generates a micron-level open-circuit voltage (V_oc) with clear polarization dependence from the laser input, but the nonlinear case suffers from a weak noise-like signal. Finally, we analyze two types of devices using thermoelectric and tunneling effects and discuss the future direction of nanoantenna-integrated MOS devices for efficient IR harvesters. Full article

(This article belongs to the Special Issue Nanomaterials for Photonics: Advances and Applications)

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11 pages, 517 KiB

Open AccessEditor’s ChoiceArticle

Electrical Conductive Properties of 3D-Printed Concrete Composite with Carbon Nanofibers

by Guido Goracci, David M. Salgado, Juan J. Gaitero and Jorge S. Dolado

Nanomaterials 2022, 12(22), 3939; https://doi.org/10.3390/nano12223939 - 8 Nov 2022

Cited by 4 | Viewed by 1733

Abstract

Electrical conductive properties in cement-based materials have received attention in recent years due to their key role in many innovative application (i.e., energy harvesting, deicing systems, electromagnetic shielding, and self-health monitoring). In this work, we explore the use 3D printing as an alternative [...] Read more.

Electrical conductive properties in cement-based materials have received attention in recent years due to their key role in many innovative application (i.e., energy harvesting, deicing systems, electromagnetic shielding, and self-health monitoring). In this work, we explore the use 3D printing as an alternative method for the preparation of electrical conductive concretes. With this aim, the conductive performance of cement composites with carbon nanofibers (0, 1, 2.5, and 4 wt%) was explored by means of a combination of thermogravimetric analysis (TGA) and dielectric spectroscopy (DS) and compared with that of specimens prepared with the traditional mold method. The combination of TGA and DS gave us a unique insight into the electrical conductive properties, measuring the specimens’ performance while monitoring the amount in water confined in the porous network. Experimental evidence of an additional contribution to the electrical conductivity due to sample preparation is provided. In particular, in this work, a strong correlation between water molecules in interconnected pores and the

σ (ω)

values is shown, originating, mainly, from the use of the 3D printing technique. Full article

(This article belongs to the Special Issue Nanostructured Materials for Energy Applications)

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15 pages, 2590 KiB

Open AccessEditor’s ChoiceArticle

Design and Development of Magnetic Iron Core Gold Nanoparticle-Based Fluorescent Multiplex Assay to Detect Salmonella

by Xinyi Zhao, Gwendoline Smith, Bilal Javed, Garret Dee, Yurii K. Gun’ko, James Curtin, Hugh J. Byrne, Christine O’Connor and Furong Tian

Nanomaterials 2022, 12(21), 3917; https://doi.org/10.3390/nano12213917 - 7 Nov 2022

Cited by 8 | Viewed by 2371

Abstract

Salmonella is a bacterial pathogen which is one of the leading causes of severe illnesses in humans. The current study involved the design and development of two methods, respectively using iron oxide nanoparticle (IONP) and iron core gold nanoparticle (ICGNP), conjugated with the [...] Read more.

Salmonella is a bacterial pathogen which is one of the leading causes of severe illnesses in humans. The current study involved the design and development of two methods, respectively using iron oxide nanoparticle (IONP) and iron core gold nanoparticle (ICGNP), conjugated with the Salmonella antibody and the fluorophore, 4-Methylumbelliferyl Caprylate (4-MUCAP), used as an indicator, for its selective and sensitive detection in contaminated food products. Twenty double-blind beverage samples, spiked with Salmonella enteritidis, Staphylococcus aureus, and Escherichia coli, were prepared in sterile Eppendorf^® tubes at room temperature. The gold layer and spikes of ICGNPs increased the surface areas. The ratio of the surface area is 0.76 (IONPs/ICGNPs). The comparative sensitivity and specificity of the IONP-based and the ICGNP-based methods to detect Salmonella were determined. The ICGNP method shows the limit of detection is 32 Salmonella per mL. The ICGNPs had an 83.3% sensitivity and a 92.9% specificity value for the presence and detection of Salmonella. The IONP method resulted in a limit of detection of 150 Salmonella per mL, and a 66.7% sensitivity and 83.3% specificity for the presence and detection of Salmonella. The higher surface area of ICGNPs increases the efficiency of detection. The monitoring of Salmonella can thus be achieved by a rapid magnetic fluorescent assay using a smartphone for image capture and analyze, providing quantitative results. The findings from the present study would help to detect Salmonella rapidly in water. It can improve the microbial quality of water and food safety due to the presence of Salmonella in the water environment. Full article

(This article belongs to the Special Issue Nanostructured Materials and Their Composites for Biosensing Applications)

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13 pages, 15815 KiB

Open AccessEditor’s ChoiceArticle

Fe₃O₄-Nanoparticle-Doped Epoxy Resin as a Detachable Adhesive by Electromagnetic Heating for GFRP Single-Lap Joints

by Xoan F. Sánchez-Romate, Antonio del Bosque, Anabel Crespo, Rafael Alonso, María Sánchez and Alejandro Ureña

Nanomaterials 2022, 12(21), 3913; https://doi.org/10.3390/nano12213913 - 6 Nov 2022

Cited by 2 | Viewed by 1610

Abstract

An adhesive based on a Fe₃O₄-nanoparticle (MNP)-doped epoxy resin was proposed for the development of detachable adhesive joints with GFRP substrates. The analysis of cryofractures showed that the increasing MNP content promotes a higher presence of larger aggregates and [...] Read more.

An adhesive based on a Fe₃O₄-nanoparticle (MNP)-doped epoxy resin was proposed for the development of detachable adhesive joints with GFRP substrates. The analysis of cryofractures showed that the increasing MNP content promotes a higher presence of larger aggregates and a lower sedimentation of nanoparticles due to the higher viscosity of the mixture. In this regard, the inclusion of expandable microspheres (MS) induces a more uniform dispersion of MNPs, reducing their sedimentation. The capability of the proposed adhesives for electromagnetic (EM) heating was also evaluated, with increases in temperature of around 100 °C at 750 A, enough to reach the T_g of the polymer required to facilitate the adhesive detachment, which is around 80 °C. Finally, the lap shear strength (LSS) of 14 and 20 wt.% MNP samples was evaluated in a single-lap shear joint with simultaneous EM heating. The LSS values were reduced by 60–80% at 750 A, thus promoting successful adhesive joint detachment under EM heating. Full article

(This article belongs to the Section Nanocomposite Materials)

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12 pages, 2934 KiB

Open AccessEditor’s ChoiceArticle

Reduced Thermal Conductivity in Nanostructured AgSbTe₂ Thermoelectric Material, Obtained by Arc-Melting

by Javier Gainza, Federico Serrano-Sánchez, Oscar J. Dura, Norbert M. Nemes, Jose Luis Martínez, María Teresa Fernández-Díaz and José Antonio Alonso

Nanomaterials 2022, 12(21), 3910; https://doi.org/10.3390/nano12213910 - 5 Nov 2022

Cited by 3 | Viewed by 2196

Abstract

AgSbTe₂ intermetallic compound is a promising thermoelectric material. It has also been described as necessary to obtain LAST and TAGS alloys, some of the best performing thermoelectrics of the last decades. Due to the random location of Ag and Sb atoms in [...] Read more.

AgSbTe₂ intermetallic compound is a promising thermoelectric material. It has also been described as necessary to obtain LAST and TAGS alloys, some of the best performing thermoelectrics of the last decades. Due to the random location of Ag and Sb atoms in the crystal structure, the electronic structure is highly influenced by the atomic ordering of these atoms and makes the accurate determination of the Ag/Sb occupancy of paramount importance. We report on the synthesis of polycrystalline AgSbTe₂ by arc-melting, yielding nanostructured dense pellets. SEM images show a conspicuous layered nanostructuration, with a layer thickness of 25–30 nm. Neutron powder diffraction data show that AgSbTe₂ crystalizes in the cubic Pm-3m space group, with a slight deficiency of Te, probably due to volatilization during the arc-melting process. The transport properties show some anomalies at ~600 K, which can be related to the onset temperature for atomic ordering. The average thermoelectric figure of merit remains around ~0.6 from ~550 up to ~680 K. Full article

(This article belongs to the Special Issue Advanced Nanoscale Materials for Thermoelectric Applications)

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10 pages, 5196 KiB

Open AccessEditor’s ChoiceArticle

Influence of Group-IVA Doping on Electronic and Optical Properties of ZnS Monolayer: A First-Principles Study

by Bin Liu, Wan-Sheng Su and Bi-Ru Wu

Nanomaterials 2022, 12(21), 3898; https://doi.org/10.3390/nano12213898 - 4 Nov 2022

Cited by 3 | Viewed by 1824

Abstract

Element doping is a universal way to improve the electronic and optical properties of two-dimensional (2D) materials. Here, we investigate the influence of group−ⅣA element (C, Si, Ge, Sn, and Pb) doping on the electronic and optical properties of the ZnS monolayer with [...] Read more.

Element doping is a universal way to improve the electronic and optical properties of two-dimensional (2D) materials. Here, we investigate the influence of group−ⅣA element (C, Si, Ge, Sn, and Pb) doping on the electronic and optical properties of the ZnS monolayer with a tetragonal phase by using first-principles calculations. The results indicate that the doping atoms tend to form tetrahedral structures with neighboring S atoms. In these doped models, the formation energies are all negative, indicating that the formation processes of the doped models will release energy. The formation energy is smallest for C−doped ZnS and gradually increases with the metallicity of the doping element. The doped ZnS monolayer retains a direct band gap, with this band gap changing little in other element doping cases. Moreover, intermediate states are observed that are induced by the sp³ hybridization from the doping atoms and S atoms. Such intermediate states expand the optical absorption range into the visible spectrum. Our findings provide an in-depth understanding of the electronic and optical properties of the ZnS monolayer and the associated doping structures, which is helpful for application in optoelectronic devices. Full article

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

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13 pages, 2215 KiB

Open AccessEditor’s ChoiceArticle

Cancer Diagnosis Using Terahertz-Graphene-Metasurface-Based Biosensor with Dual-Resonance Response

by Chunjian Tan, Shaogang Wang, Shizhen Li, Xu Liu, Jia Wei, Guoqi Zhang and Huaiyu Ye

Nanomaterials 2022, 12(21), 3889; https://doi.org/10.3390/nano12213889 - 3 Nov 2022

Cited by 21 | Viewed by 2484

Abstract

Owing to the outstanding physical properties of graphene, its biosensing applications implemented by the terahertz metasurface are widely concerned and studied. Here, we present a novel design of the graphene metasurface, which consists of an individual graphene ring and an H-shaped graphene structure. [...] Read more.

Owing to the outstanding physical properties of graphene, its biosensing applications implemented by the terahertz metasurface are widely concerned and studied. Here, we present a novel design of the graphene metasurface, which consists of an individual graphene ring and an H-shaped graphene structure. The graphene metasurface exhibits a dual-resonance response, whose resonance frequency strongly varies with the geometrical parameters of the proposed metasurface, the carrier density of graphene, and the analyte composition. The transparency window, including width and position, can be artificially controlled by adjusting the geometrical parameters or the Fermi energy. Furthermore, the sensing parameters of the graphene metasurface for cancerous and normal cells are investigated, focusing on two factors, namely cell quantity and position on the metasurface. The simulated results clearly show that the theoretical sensitivity, figure of merit, and quantity of the graphene metasurface for breast cells reach 1.21 THz/RIU, 2.75 RIU

^{- 1}

, and 2.43, respectively. Our findings may open up new avenues for promising applications in the diagnosis of cancers. Full article

(This article belongs to the Topic Advances and Applications of 2D Materials, 2nd Volume)

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22 pages, 4019 KiB

Open AccessEditor’s ChoiceReview

Recent Development of Carbon-Nanotube-Based Solar Heat Absorption Devices and Their Application

by Saiful Islam and Hiroshi Furuta

Nanomaterials 2022, 12(21), 3871; https://doi.org/10.3390/nano12213871 - 2 Nov 2022

Cited by 6 | Viewed by 3748

Abstract

Population growth and the current global weather patterns have heightened the need to optimize solar energy harvesting. Solar-powered water filtration, electricity generation, and water heating have gradually multiplied as viable sources of fresh water and power generation, especially for isolated places without access [...] Read more.

Population growth and the current global weather patterns have heightened the need to optimize solar energy harvesting. Solar-powered water filtration, electricity generation, and water heating have gradually multiplied as viable sources of fresh water and power generation, especially for isolated places without access to water and energy. The unique thermal and optical characteristics of carbon nanotubes (CNTs) enable their use as efficient solar absorbers with enhanced overall photothermal conversion efficiency under varying solar light intensities. Due to their exceptional optical absorption efficiency, low cost, environmental friendliness, and natural carbon availability, CNTs have attracted intense scientific interest in the production of solar thermal systems. In this review study, we evaluated CNT-based water purification, thermoelectric generation, and water heating systems under varying solar levels of illumination, ranging from domestic applications to industrial usage. The use of CNT composites or multilayered structures is also reviewed in relation to solar heat absorber applications. An aerogel containing CNTs was able to ameliorate water filtering performance at low solar intensities. CNTs with a Fresnel lens improved thermoelectric output power at high solar intensity. Solar water heating devices utilizing a nanofluid composed of CNTs proved to be the most effective. In this review, we also aimed to identify the most relevant challenges and promising opportunities in relation to CNT-based solar thermal devices. Full article

(This article belongs to the Special Issue State-of-the-Art 2D and Carbon Nanomaterials in Japan)

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43 pages, 4139 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in the Development of Lipid-, Metal-, Carbon-, and Polymer-Based Nanomaterials for Antibacterial Applications

by Ruohua Ren, Chiaxin Lim, Shiqi Li, Yajun Wang, Jiangning Song, Tsung-Wu Lin, Benjamin W. Muir, Hsien-Yi Hsu and Hsin-Hui Shen

Nanomaterials 2022, 12(21), 3855; https://doi.org/10.3390/nano12213855 - 1 Nov 2022

Cited by 25 | Viewed by 3658

Abstract

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to [...] Read more.

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to discover potential new antibiotics. The use of nanotechnology, encompassing a broad range of organic and inorganic nanomaterials, offers promising solutions. Organic nanomaterials, including lipid-, polymer-, and carbon-based nanomaterials, have inherent antibacterial activity or can act as nanocarriers in delivering antibacterial agents. Nanocarriers, owing to the protection and enhanced bioavailability of the encapsulated drugs, have the ability to enable an increased concentration of a drug to be delivered to an infected site and reduce the associated toxicity elsewhere. On the other hand, inorganic metal-based nanomaterials exhibit multivalent antibacterial mechanisms that combat MDR bacteria effectively and reduce the occurrence of bacterial resistance. These nanomaterials have great potential for the prevention and treatment of MDR bacterial infection. Recent advances in the field of nanotechnology are enabling researchers to utilize nanomaterial building blocks in intriguing ways to create multi-functional nanocomposite materials. These nanocomposite materials, formed by lipid-, polymer-, carbon-, and metal-based nanomaterial building blocks, have opened a new avenue for researchers due to the unprecedented physiochemical properties and enhanced antibacterial activities being observed when compared to their mono-constituent parts. This review covers the latest advances of nanotechnologies used in the design and development of nano- and nanocomposite materials to fight MDR bacteria with different purposes. Our aim is to discuss and summarize these recently established nanomaterials and the respective nanocomposites, their current application, and challenges for use in applications treating MDR bacteria. In addition, we discuss the prospects for antimicrobial nanomaterials and look forward to further develop these materials, emphasizing their potential for clinical translation. Full article

(This article belongs to the Special Issue Advanced Nanomaterials in Biomedical Application)

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7 pages, 2426 KiB

Open AccessEditor’s ChoiceReview

Role of Interdiffusion and Segregation during the Life of Indium Gallium Arsenide Quantum Dots, from Cradle to Grave

by Thomas Walther

Nanomaterials 2022, 12(21), 3850; https://doi.org/10.3390/nano12213850 - 31 Oct 2022

Cited by 3 | Viewed by 1388

Abstract

This article summarizes our understanding of the interplay between diffusion and segregation during epitaxial growth of InGaAs and InAs quantum dots. These quantum dots form spontaneously on flat GaAs (001) single-crystalline substrates by the so-called Stranski-Krastanow growth mechanism once a sufficient amount of [...] Read more.

This article summarizes our understanding of the interplay between diffusion and segregation during epitaxial growth of InGaAs and InAs quantum dots. These quantum dots form spontaneously on flat GaAs (001) single-crystalline substrates by the so-called Stranski-Krastanow growth mechanism once a sufficient amount of indium has accumulated on the surface. Initially a perfectly flat wetting layer is formed. This strained layer then starts to roughen as strain increases, leading first to small, long-range surface undulations and then to tiny coherent islands. These continue to grow, accumulating indium both from the underlying wetting layer by lateral indium segregation and from within these islands by vertical segregation, which for InGaAs deposition results in an indium-enriched InGaAs alloy in the centre of the quantum dots. For pure InAs deposition, interdiffusion also results in an InGaAs alloy. Further deposition can lead to the formation of misfit dislocations that nucleate at the edges of the islands and are generally sought to be avoided. Overgrowth by GaAs or InGaAs alloys with low indium content commences preferentially between the islands, avoiding their strained edges, which initially leads to trench formation. Further deposition is necessary to cap these quantum dots effectively and to re-gain an almost flat surface that can then be used for subsequent deposition of multiple layers of quantum dots as needed for many optoelectronic devices. Full article

(This article belongs to the Special Issue Transmission Electron Microscopy for Nanomaterials Research Advances)

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13 pages, 4181 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Cu Micromembrane as a Flexible Electrode

by Bo-Yao Sun, Wai-Hong Cheang, Shih-Cheng Chou, Jung-Chih Chiao and Pu-Wei Wu

Nanomaterials 2022, 12(21), 3829; https://doi.org/10.3390/nano12213829 - 29 Oct 2022

Viewed by 1563

Abstract

A Cu micromembrane is successfully fabricated and validated as a porous flexible electrode. The Cu micromembrane is prepared by functionalizing individual polypropylene (PP) fibers in a polypropylene micromembrane (PPMM) using a mixture of polydopamine (PDA) and polyethyleneimine (PEI). The mixture of PDA and [...] Read more.

A Cu micromembrane is successfully fabricated and validated as a porous flexible electrode. The Cu micromembrane is prepared by functionalizing individual polypropylene (PP) fibers in a polypropylene micromembrane (PPMM) using a mixture of polydopamine (PDA) and polyethyleneimine (PEI). The mixture of PDA and PEI provides adhesive, wetting, and reducing functionalities that facilitate subsequent Ag activation and Cu electroless plating. Scanning electron microscopy reveals conformal deposition of Cu on individual PP fibers. Porometer analysis indicates that the porous nature of PPMM is properly maintained. The Cu micromembrane demonstrates impressive electrical conductivities in both the X direction (1.04 ± 0.21 S/cm) and Z direction (2.99 ± 0.54 × 10⁻³ S/cm). In addition, its tensile strength and strain are better than those of pristine PPMM. The Cu micromembrane is flexible and mechanically robust enough to sustain 10,000 bending cycles with moderate deterioration. Thermogravimetric analysis shows a thermal stability of 400 °C and an effective Cu loading of 5.36 mg/cm². Cyclic voltammetric measurements reveal that the Cu micromembrane has an electrochemical surface area of 277.8 cm² in a 1 cm² geometric area (a roughness factor of 227.81), a value that is 45 times greater than that of planar Cu foil. Full article

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

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10 pages, 3766 KiB

Open AccessEditor’s ChoiceArticle

Hot Electron Extraction in SWCNT/TiO₂ for Photocatalytic H₂ Evolution from Water

by Masahiro Yamagami, Tomoyuki Tajima, Zihao Zhang, Jun Kano, Ki-ichi Yashima, Takana Matsubayashi, Huyen Khanh Nguyen, Naoto Nishiyama, Tomoya Hayashi and Yutaka Takaguchi

Nanomaterials 2022, 12(21), 3826; https://doi.org/10.3390/nano12213826 - 29 Oct 2022

Cited by 2 | Viewed by 2241

Abstract

Single-walled carbon nanotube (SWCNT)/TiO₂ hybrids were synthesized using 1,10-bis(decyloxy)decane-core PAMAM dendrimer as a molecular glue. Upon photoirradiation of a water dispersion of SWCNT/TiO₂ hybrids with visible light (λ > 422 nm), the hydrogen evolution reaction proceeded at a rate of 0.95 [...] Read more.

Single-walled carbon nanotube (SWCNT)/TiO₂ hybrids were synthesized using 1,10-bis(decyloxy)decane-core PAMAM dendrimer as a molecular glue. Upon photoirradiation of a water dispersion of SWCNT/TiO₂ hybrids with visible light (λ > 422 nm), the hydrogen evolution reaction proceeded at a rate of 0.95 mmol/h·g in the presence of a sacrificial agent (1-benzyl-1,4-dihydronicotinamide, BNAH). External quantum yields (EQYs) of the hydrogen production reaction photosensitized by (6,5), (7,5), and (8,3) tubes were estimated to be 5.5%, 3.6%, and 2.2%, respectively, using monochromatic lights corresponding to their E₂₂ absorptions (570 nm, 650 nm, and 680 nm). This order of EQYs (i.e., (6,5) > (7,5) > (8,3)SWCNTs) exhibited the dependence on the C₂ energy level of SWCNT for EQY and proved the hot electron extraction pathway. Full article

(This article belongs to the Special Issue State-of-the-Art 2D and Carbon Nanomaterials in Japan)

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17 pages, 4229 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Hydrogen Production from Glycerol Aqueous Solutions as Sustainable Feedstocks Using Zr-Based UiO-66 Materials under Simulated Sunlight Irradiation

by Celia M. Rueda-Navarro, Belén Ferrer, Herme G. Baldoví and Sergio Navalón

Nanomaterials 2022, 12(21), 3808; https://doi.org/10.3390/nano12213808 - 28 Oct 2022

Cited by 13 | Viewed by 2585

Abstract

There is an increasing interest in developing cost-effective technologies to produce hydrogen from sustainable resources. Herein we show a comprehensive study on the use of metal–organic frameworks (MOFs) as heterogeneous photocatalysts for H₂ generation from photoreforming of glycerol aqueous solutions under simulated [...] Read more.

There is an increasing interest in developing cost-effective technologies to produce hydrogen from sustainable resources. Herein we show a comprehensive study on the use of metal–organic frameworks (MOFs) as heterogeneous photocatalysts for H₂ generation from photoreforming of glycerol aqueous solutions under simulated sunlight irradiation. The list of materials employed in this study include some of the benchmark Zr-MOFs such as UiO-66(Zr)-X (X: H, NO₂, NH₂) as well as MIL-125(Ti)-NH₂ as the reference Ti-MOF. Among these solids, UiO-66(Zr)-NH₂ exhibits the highest photocatalytic H₂ production, and this observation is attributed to its adequate energy level. The photocatalytic activity of UiO-66(Zr)-NH₂ can be increased by deposition of small Pt NPs as the reference noble metal co-catalyst within the MOF network. This photocatalyst is effectively used for H₂ generation at least for 70 h without loss of activity. The crystallinity of MOF and Pt particle size were maintained as revealed by powder X-ray diffraction and transmission electron microscopy measurements, respectively. Evidence in support of the occurrence of photoinduced charge separation with Pt@UiO-66(Zr)-NH₂ is provided from transient absorption and photoluminescence spectroscopies together with photocurrent measurements. This study exemplifies the possibility of using MOFs as photocatalysts for the solar-driven H₂ generation using sustainable feedstocks. Full article

(This article belongs to the Special Issue Carbon-Based Nanomaterials for Visible-Light Photocatalysis and Photoelectrocatalysis)

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23 pages, 6604 KiB

Open AccessEditor’s ChoiceArticle

Adsorption of Peptides onto Carbon Nanotubes Grafted with Poly(ethylene Oxide) Chains: A Molecular Dynamics Simulation Study

by Zuzana Benková, Peter Čakánek and Maria Natália D. S. Cordeiro

Nanomaterials 2022, 12(21), 3795; https://doi.org/10.3390/nano12213795 - 27 Oct 2022

Cited by 1 | Viewed by 1474

Abstract

Carbon nanotubes (CNTs) display exceptional properties that predispose them to wide use in technological or biomedical applications. To remove the toxicity of CNTs and to protect them against undesired protein adsorption, coverage of the CNT sidewall with poly(ethylene oxide) (PEO) is often considered. [...] Read more.

Carbon nanotubes (CNTs) display exceptional properties that predispose them to wide use in technological or biomedical applications. To remove the toxicity of CNTs and to protect them against undesired protein adsorption, coverage of the CNT sidewall with poly(ethylene oxide) (PEO) is often considered. However, controversial results on the antifouling effectiveness of PEO layers have been reported so far. In this work, the interactions of pristine CNT and CNT covered with the PEO chains at different grafting densities with polyglycine, polyserine, and polyvaline are studied using molecular dynamics simulations in vacuum, water, and saline environments. The peptides are adsorbed on CNT in all investigated systems; however, the adsorption strength is reduced in aqueous environments. Save for one case, addition of NaCl at a physiological concentration to water does not appreciably influence the adsorption and structure of the peptides or the grafted PEO layer. It turns out that the flexibility of the peptide backbone allows the peptide to adopt more asymmetric conformations which may be inserted deeper into the grafted PEO layer. Water molecules disrupt the internal hydrogen bonds in the peptides, as well as the hydrogen bonds formed between the peptides and the PEO chains. Full article

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

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16 pages, 6096 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Investigation of Aerosol-Assisted Atmospheric Pressure Plasma Deposited Hybrid TiO₂ Containing Nanocomposite Coatings

by Chiara Lo Porto, Massimo Dell’Edera, Ilaria De Pasquale, Antonella Milella, Francesco Fracassi, Maria Lucia Curri, Roberto Comparelli and Fabio Palumbo

Nanomaterials 2022, 12(21), 3758; https://doi.org/10.3390/nano12213758 - 26 Oct 2022

Cited by 1 | Viewed by 1500

Abstract

We report on the aerosol-assisted atmospheric-pressure plasma deposition onto a stainless-steel woven mesh of a thin nanocomposite coating based on TiO₂ nanoparticles hosted in a hybrid organic–inorganic matrix, starting from nanoparticles dispersed in a mixture of hexamethyldisiloxane and isopropyl alcohol. The stainless-steel [...] Read more.

We report on the aerosol-assisted atmospheric-pressure plasma deposition onto a stainless-steel woven mesh of a thin nanocomposite coating based on TiO₂ nanoparticles hosted in a hybrid organic–inorganic matrix, starting from nanoparticles dispersed in a mixture of hexamethyldisiloxane and isopropyl alcohol. The stainless-steel mesh was selected as an effective support for the possible future technological application of the coating for photocatalytically assisted water depollution. The prepared coatings were thoroughly investigated from the chemical and morphological points of view and were demonstrated to be photocatalytically active in the degradation of an organic molecule, used as a pollutant model, in water upon UV light irradiation. In order to optimize the photocatalytic performance, different approaches were investigated for the coating’s realization, namely (i) the control of the deposition time and (ii) the application of a postdeposition O₂ plasma treatment on the pristine coatings. Both strategies were found to be able to increase the photocatalytic activity, and, remarkably, their combination resulted in a further enhancement of the photoactivity. Indeed, the proposed combined approach allowed a three-fold increase in the kinetic constant of the degradation reaction of the model dye methylene blue with respect to the pristine coating. Interestingly, the chemical and morphological characterizations of all the prepared coatings were able to account for the enhancement of the photocatalytic performance. Indeed, the presence of the TiO₂ nanoparticles on the outmost surface of the film confirmed the accessibility of the photocatalytic sites in the nanocomposite and reasonably explained the enhanced photocatalytic performance. In addition, the sustained photoactivity (>5 cycles of use) of the nanocomposites was demonstrated. Full article

(This article belongs to the Special Issue Unconventional and Green Approaches for the Synthesis of Crystalline Inorganic Materials)

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14 pages, 2230 KiB

Open AccessEditor’s ChoiceArticle

On the Development of Nanocomposite Covalent Associative Networks Based on Polycaprolactone and Reduced Graphite Oxide

by Alberto Vallin, Daniele Battegazzore, Giacomo Damonte, Alberto Fina and Orietta Monticelli

Nanomaterials 2022, 12(21), 3744; https://doi.org/10.3390/nano12213744 - 25 Oct 2022

Cited by 6 | Viewed by 1513

Abstract

In this work, the development of nanocomposite systems based on reduced graphite oxide (rGO) was combined with the development of crosslinked materials characterized by dynamic covalent bonds, i.e., a covalent associative network, starting from ad-hoc synthesized hydroxyl terminated polycaprolactone (PCL-OH). The crosslinking reaction [...] Read more.

In this work, the development of nanocomposite systems based on reduced graphite oxide (rGO) was combined with the development of crosslinked materials characterized by dynamic covalent bonds, i.e., a covalent associative network, starting from ad-hoc synthesized hydroxyl terminated polycaprolactone (PCL-OH). The crosslinking reaction was carried out using methylenediphenyl diisocyanate (MDI) to create systems capable of bond exchanges via transesterification and transcarbamoylation reactions, in the presence of stannous octoate as a catalyst. The above materials were prepared at two different temperatures (120 and 200 °C) and two PCL-OH:MDI ratios. FT-IR measurements proved the formation of urethane bonds in all the prepared samples. Crosslinking was demonstrated by contacting the samples with a solvent capable of dissolving the star-shaped PCL. These tests showed a significant increase in the crosslinked fraction with increasing the temperature and the PCL-OH:MDI ratio. In order to evidence the effect of crosslinking on rGO dispersion and the final properties of the material, a nanocomposite sample was also prepared using a linear commercial PCL, with the nanofiller mixed under the same conditions used to develop the crosslinked systems. The dispersion of rGO, which was investigated using FE-SEM measurements, was similar in the different systems prepared, indicating that the crosslinking process had a minor effect on the dispersibility of the nanofiller. As far as the thermal properties are concerned, the DSC measurements of the prepared samples showed that the crosslinking leads to a decrease in the crystallinity of the polymer, a phenomenon which was particularly evident in the sample prepared at 200 °C with a PCL-OH: MDI ratio of 1:1.33 and was related to the decrease in the polymer chain mobility. Moreover, rGO was found to act as a nucleating agent and increase the crystallization temperature of the nanocomposite sample based on linear commercial PCL, while the contribution of rGO in the crosslinked nanocomposite samples was minor. Rheological measurements confirmed the crosslinking of the PCL-OH system which generates a solid-like behavior depending on the PCL-OH:MDI ratio used. The presence of rGO during crosslinking generated a further huge increase in the viscosity of the melt with a remarkable solid-like behavior, confirming a strong interaction between rGO and crosslinked PCL. Finally, the prepared nanocomposites exhibited self-healing and recyclability properties, thus meeting the requirements for sustainable materials. Full article

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15 pages, 3754 KiB

Open AccessEditor’s ChoiceArticle

Electrostatic and Environmental Control of the Trion Fine Structure in Transition Metal Dichalcogenide Monolayers

by Yaroslav V. Zhumagulov, Alexei Vagov, Dmitry R. Gulevich and Vasili Perebeinos

Nanomaterials 2022, 12(21), 3728; https://doi.org/10.3390/nano12213728 - 24 Oct 2022

Cited by 2 | Viewed by 1924

Abstract

Charged excitons or trions are essential for optical spectra in low-dimensional doped monolayers (ML) of transitional metal dichalcogenides (TMDC). Using a direct diagonalization of the three-body Hamiltonian, we calculate the low-lying trion states in four types of TMDC MLs as a function of [...] Read more.

Charged excitons or trions are essential for optical spectra in low-dimensional doped monolayers (ML) of transitional metal dichalcogenides (TMDC). Using a direct diagonalization of the three-body Hamiltonian, we calculate the low-lying trion states in four types of TMDC MLs as a function of doping and dielectric environment. We show that the fine structure of the trion is the result of the interplay between the spin-valley fine structure of the single-particle bands and the exchange interaction. We demonstrate that by variations of the doping and dielectric environment, the fine structure of the trion energy can be tuned, leading to anticrossing of the bright and dark states, with substantial implications for the optical spectra of the TMDC ML. Full article

(This article belongs to the Special Issue Recent Advances in Optical Spectroscopy of Layered Materials)

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