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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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15 pages, 2050 KiB  
Article
Quantifying the Charge Carrier Interaction in Metallic Twisted Bilayer Graphene Superlattices
by Evgueni F. Talantsev
Nanomaterials 2021, 11(5), 1306; https://doi.org/10.3390/nano11051306 - 15 May 2021
Cited by 8 | Viewed by 2866
Abstract
The mechanism of charge carrier interaction in twisted bilayer graphene (TBG) remains an unresolved problem, where some researchers proposed the dominance of the electron–phonon interaction, while the others showed evidence for electron–electron or electron–magnon interactions. Here we propose to resolve this problem by [...] Read more.
The mechanism of charge carrier interaction in twisted bilayer graphene (TBG) remains an unresolved problem, where some researchers proposed the dominance of the electron–phonon interaction, while the others showed evidence for electron–electron or electron–magnon interactions. Here we propose to resolve this problem by generalizing the Bloch–Grüneisen equation and using it for the analysis of the temperature dependent resistivity in TBG. It is a well-established theoretical result that the Bloch–Grüneisen equation power-law exponent, p, exhibits exact integer values for certain mechanisms. For instance, p = 5 implies the electron–phonon interaction, p = 3 is associated with the electron–magnon interaction and p = 2 applies to the electron–electron interaction. Here we interpret the linear temperature-dependent resistance, widely observed in TBG, as p→1, which implies the quasielastic charge interaction with acoustic phonons. Thus, we fitted TBG resistance curves to the Bloch–Grüneisen equation, where we propose that p is a free-fitting parameter. We found that TBGs have a smoothly varied p-value (ranging from 1.4 to 4.4) depending on the Moiré superlattice constant, λ, or the charge carrier concentration, n. This implies that different mechanisms of the charge carrier interaction in TBG superlattices smoothly transition from one mechanism to another depending on, at least, λ and n. The proposed generalized Bloch–Grüneisen equation is applicable to a wide range of disciplines, including superconductivity and geology. Full article
(This article belongs to the Special Issue Superconductivity in Nanoscaled Systems)
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11 pages, 3413 KiB  
Article
Studies of Defect Structure in Epitaxial AlN/GaN Films Grown on (111) 3C-SiC
by Andreea Bianca Serban, Vladimir Lucian Ene, Doru Dinescu, Iulia Zai, Nikolay Djourelov, Bogdan Stefan Vasile and Victor Leca
Nanomaterials 2021, 11(5), 1299; https://doi.org/10.3390/nano11051299 - 14 May 2021
Cited by 3 | Viewed by 3238
Abstract
Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heterostructure, the consistency of the interfaces, and elemental diffusion are achieved by High Resolution Transmission Electron Microscopy (HR-TEM). In addition, the dislocation densities together with the defect correlation lengths are [...] Read more.
Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heterostructure, the consistency of the interfaces, and elemental diffusion are achieved by High Resolution Transmission Electron Microscopy (HR-TEM). In addition, the dislocation densities together with the defect correlation lengths are investigated via High-Resolution X-ray Diffraction (HR-XRD) and the characteristic positron diffusion length is achieved by Doppler Broadening Spectroscopy (DBS). Moreover, a comparative analysis with our previous work (i.e., GaN/AlN/Si and GaN/AlN/Al2O3) has been carried out. Within the epitaxial GaN layer defined by the relationship F4¯3m (111) 3C-SiC || P63mc (0002) AlN || P63mc (0002) GaN, the total dislocation density has been assessed as being 1.47 × 1010 cm−2. Compared with previously investigated heterostructures (on Si and Al2O3 substrates), the obtained dislocation correlation lengths (Le = 171 nm and Ls =288 nm) and the mean distance between two dislocations (rd = 82 nm) are higher. This reveals an improved crystal quality of the GaN with SiC as a growth template. In addition, the DBS measurements upheld the aforementioned results with a higher effective positron diffusion length LeffGaN2 = 75 ± 20 nm for the GaN layer. Full article
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17 pages, 8325 KiB  
Article
Li4(OH)3Br-Based Shape Stabilized Composites for High-Temperature TES Applications: Selection of the Most Convenient Supporting Material
by Imane Mahroug, Stefania Doppiu, Jean-Luc Dauvergne, Angel Serrano and Elena Palomo del Barrio
Nanomaterials 2021, 11(5), 1279; https://doi.org/10.3390/nano11051279 - 13 May 2021
Cited by 4 | Viewed by 2494
Abstract
Peritectic compound Li4(OH)3Br has been recently proposed as phase change material (PCM) for thermal energy storage (TES) applications at approx. 300 °C Compared to competitor PCM materials (e.g., sodium nitrate), the main assets of this compound are high volumetric [...] Read more.
Peritectic compound Li4(OH)3Br has been recently proposed as phase change material (PCM) for thermal energy storage (TES) applications at approx. 300 °C Compared to competitor PCM materials (e.g., sodium nitrate), the main assets of this compound are high volumetric latent heat storage capacity (>140 kWh/m3) and very low volume changes (<3%) during peritectic reaction and melting. The objective of the present work was to find proper supporting materials able to shape stabilize Li4(OH)3Br during the formation of the melt and after its complete melting, avoiding any leakage and thus obtaining a composite apparently always in the solid state during the charge and discharge of the TES material. Micro-nanoparticles of MgO, Fe2O3, CuO, SiO2 and Al2O3 have been considered as candidate supporting materials combined with the cold-compression route for shape-stabilized composites preparation. The work carried out allowed for the identification of the most promising composite based on MgO nanoparticles through a deep experimental analysis and characterization, including chemical compatibility tests, anti-leakage performance evaluation, structural and thermodynamic properties analysis and preliminary cycling stability study. Full article
(This article belongs to the Special Issue Multifunctional Nanomaterials for Energy Applications)
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16 pages, 4800 KiB  
Article
Remotely Self-Healable, Shapeable and pH-Sensitive Dual Cross-Linked Polysaccharide Hydrogels with Fast Response to Magnetic Field
by Andrey V. Shibaev, Maria E. Smirnova, Darya E. Kessel, Sergey A. Bedin, Irina V. Razumovskaya and Olga E. Philippova
Nanomaterials 2021, 11(5), 1271; https://doi.org/10.3390/nano11051271 - 12 May 2021
Cited by 18 | Viewed by 3901
Abstract
The development of actuators with remote control is important for the construction of devices for soft robotics. The present paper describes a responsive hydrogel of nontoxic, biocompatible, and biodegradable polymer carboxymethyl hydroxypropyl guar with dynamic covalent cross-links and embedded cobalt ferrite nanoparticles. The [...] Read more.
The development of actuators with remote control is important for the construction of devices for soft robotics. The present paper describes a responsive hydrogel of nontoxic, biocompatible, and biodegradable polymer carboxymethyl hydroxypropyl guar with dynamic covalent cross-links and embedded cobalt ferrite nanoparticles. The nanoparticles significantly enhance the mechanical properties of the gel, acting as additional multifunctional non-covalent linkages between the polymer chains. High magnetization of the cobalt ferrite nanoparticles provides to the gel a strong responsiveness to the magnetic field, even at rather small content of nanoparticles. It is demonstrated that labile cross-links in the polymer matrix impart to the hydrogel the ability of self-healing and reshaping as well as a fast response to the magnetic field. In addition, the gel shows pronounced pH sensitivity due to pH-cleavable cross-links. The possibility to use the multiresponsive gel as a magnetic-field-triggered actuator is demonstrated. Full article
(This article belongs to the Special Issue Advanced Magnetic Nanocomposites: Structural, Physical Properties and Application)
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11 pages, 2750 KiB  
Article
Fabrication of Porous Lead Bromide Films by Introducing Indium Tribromide for Efficient Inorganic CsPbBr3 Perovskite Solar Cells
by Xianwei Meng, Kailin Chi, Qian Li, Bingtao Feng, Haodi Wang, Tianjiao Gao, Pengyu Zhou, Haibin Yang and Wuyou Fu
Nanomaterials 2021, 11(5), 1253; https://doi.org/10.3390/nano11051253 - 11 May 2021
Cited by 10 | Viewed by 3573
Abstract
In the process of preparing CsPbBr3 films by two-step or multi-step methods, due to the low solubility of CsBr in organic solvents, the prepared perovskite films often have a large number of holes, which is definitely not conducive to the performance of [...] Read more.
In the process of preparing CsPbBr3 films by two-step or multi-step methods, due to the low solubility of CsBr in organic solvents, the prepared perovskite films often have a large number of holes, which is definitely not conducive to the performance of CsPbBr3 perovskite solar cells (PSCs). In response to this problem, this article proposed a method of introducing InBr3 into the PbBr2 precursor to prepare a porous PbBr2 film to increase the reaction efficiency between CsBr and PbBr2 and achieve the purpose of In (Ⅲ) incorporation, which not only optimized the morphology of the produced CsPbBr3 film but also enhanced the charge extraction and transport capabilities, which was ascribed to the reduction of the trap state density and impurity phases in the perovskite films, improving the performance of CsPbBr3 PSCs. At the optimal InBr3 concentration of 0.21 M, the InBr3:CsPbBr3 perovskite solar cell exhibited a power conversion efficiency of 6.48%, which was significantly higher than that of the pristine device. Full article
(This article belongs to the Special Issue Nanostructures for Perovskite Solar Cells and Light-Emitting Diodes)
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11 pages, 7623 KiB  
Article
Fabrication of Flexible Electrode with Sub-Tenth Micron Thickness Using Heat-Induced Peelable Pressure-Sensitive Adhesive Containing Amide Groups
by Hyebeom Shin, Eunseong Yang, Yong-Hoon Kim, Min-Gi Kwak and Youngmin Kim
Nanomaterials 2021, 11(5), 1250; https://doi.org/10.3390/nano11051250 - 10 May 2021
Cited by 3 | Viewed by 2932
Abstract
In response to the increasing demand for flexible devices, there is increasing effort to manufacture flexible electrodes. However, the difficulty of handling a thin film is an obstacle to the production of flexible electrodes. In this study, a heat-induced peelable pressure-sensitive adhesive (h-PSA) [...] Read more.
In response to the increasing demand for flexible devices, there is increasing effort to manufacture flexible electrodes. However, the difficulty of handling a thin film is an obstacle to the production of flexible electrodes. In this study, a heat-induced peelable pressure-sensitive adhesive (h-PSA) was fabricated and used to manufacture a flexible electrode with sub-tenth micron thickness. Unlike the control PSA, the incorporation of amide groups made the h-PSA fail through adhesive failure at temperatures ranging from 20 to 80 °C. Compared to the peeling adhesion (1719 gf/in) of h-PSA measured at 20 °C, the value (171 gf/in) measured at 80 °C was decreased by one order of magnitude. Next, the 8 μm thick polyethylene terephthalate (PET) film was attached on a thick substrate (50 μm) via h-PSA, and Mo/Al/Mol patterns were fabricated on the PET film through sputtering, photolithography, and wet-etching processes. The thick substrate alleviated the difficulty of handling the thin PET film during the electrode fabrication process. Thanks to the low peel force and clean separation of the h-PSA at 80 °C, the flexible electrode of metal patterns on the PET (8 μm) film was isolated from the substrate with little change (<1%) in electrical conductivity. Finally, the mechanical durability of the flexible electrode was evaluated by a U-shape folding test, and no cracking or delamination was observed after 10,000 test cycles. Full article
(This article belongs to the Special Issue Nanomaterial Electrodes)
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30 pages, 12212 KiB  
Review
Graphene/Reduced Graphene Oxide-Carbon Nanotubes Composite Electrodes: From Capacitive to Battery-Type Behaviour
by Olena Okhay and Alexander Tkach
Nanomaterials 2021, 11(5), 1240; https://doi.org/10.3390/nano11051240 - 8 May 2021
Cited by 87 | Viewed by 9358
Abstract
Thanks to the advanced technologies for energy generation such as solar cells and thermo- or piezo-generators the amount of electricity transformed from light, heat or mechanical pressure sources can be significantly enhanced. However, there is still a demand for effective storage devices to [...] Read more.
Thanks to the advanced technologies for energy generation such as solar cells and thermo- or piezo-generators the amount of electricity transformed from light, heat or mechanical pressure sources can be significantly enhanced. However, there is still a demand for effective storage devices to conserve electrical energy which addresses the wide range of large stationary applications from electric vehicles to small portable devices. Among the large variety of energy-storage systems available today, electrochemical energy sources and, in particular, supercapacitors (SC), are rather promising in terms of cost, scaling, power management, life cycle and safety. Therefore, this review surveys recent achievements in the development of SC based on composites of such carbon-derived materials as graphene (G) and reduced graphene oxide (rGO) with carbon nanotubes (CNT). Various factors influencing the specific capacitance are discussed, while specific energy and power as well as cycling stability of SC with G/rGO-CNT composite electrode materials are overviewed. Full article
(This article belongs to the Special Issue Ceramics and Nanostructures for Energy Harvesting and Storage)
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11 pages, 5197 KiB  
Article
Enhanced Light Absorption by Facile Patterning of Nano-Grating on Mesoporous TiO2 Photoelectrode for Cesium Lead Halide Perovskite Solar Cells
by Kang-Pil Kim, Wook Hyun Kim, Soo Min Kwon, Jun Yong Kim, Yun Seon Do and Sungho Woo
Nanomaterials 2021, 11(5), 1233; https://doi.org/10.3390/nano11051233 - 7 May 2021
Cited by 9 | Viewed by 3494
Abstract
CsPbIBr2, a cesium-based all-inorganic halide perovskite (CsPe), is a very promising alternative material to mainstream organic–inorganic hybrid halide perovskite (HPe) materials owing to its exceptional moisture stability, thermal stability, and light stability. However, because of the wide band gap (2.05 eV) [...] Read more.
CsPbIBr2, a cesium-based all-inorganic halide perovskite (CsPe), is a very promising alternative material to mainstream organic–inorganic hybrid halide perovskite (HPe) materials owing to its exceptional moisture stability, thermal stability, and light stability. However, because of the wide band gap (2.05 eV) of CsPbIBr2, it has a low power conversion efficiency (PCE), which hinders its application in highly efficient solar cells. In this study, a facile nanoimprinted one-dimensional grating nanopattern (1D GNP) formation on mesoporous TiO2 (mp-TiO2) photoelectrodes was introduced to improve the effective light utilization and enhance the performance of CsPbIBr2 perovskite solar cells (PSCs). The 1D GNP structure on the mp-TiO2 layer increases the light absorption efficiency by diffracting the unabsorbed light into the active mp-TiO2 and CsPbIBr2 layers as well as increasing the charge separation and collection due to the extended interfacial contact area between the mp-TiO2 and CsPbIBr2 layers. Consequently, both the current density (JSC) and the fill factor (FF) of the fabricated cells improved, leading to over a 20% enhancement in the solar cell’s PCE. Thus, this periodic grating structure, fabricated by simple nanoimprinting, could play an important role in the large-scale production of highly efficient and cost-effective Cs-based PSCs. Full article
(This article belongs to the Special Issue Mesoporous Materials and Nanoscale Phenomena in Hybrid Photovoltaics)
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11 pages, 5243 KiB  
Article
Bimetallic ZIF-Derived Co/N-Codoped Porous Carbon Supported Ruthenium Catalysts for Highly Efficient Hydrogen Evolution Reaction
by Hui Qi, Xinglong Guan, Guangyu Lei, Mengyao Zhao, Hongwei He, Kai Li, Guoliang Zhang, Fengbao Zhang, Xiaobin Fan, Wenchao Peng and Yang Li
Nanomaterials 2021, 11(5), 1228; https://doi.org/10.3390/nano11051228 - 6 May 2021
Cited by 16 | Viewed by 4350
Abstract
Exploring the economical, powerful, and durable electrocatalysts for hydrogen evolution reaction (HER) is highly required for practical application. Herein, nanoclusters-decorated ruthenium, cobalt nanoparticles, and nitrogen codoped porous carbon (Ru-pCo@NC) are prepared with bimetallic zeolite imidazole frameworks (ZnCo-ZIF) as the precursor. Thus, the prepared [...] Read more.
Exploring the economical, powerful, and durable electrocatalysts for hydrogen evolution reaction (HER) is highly required for practical application. Herein, nanoclusters-decorated ruthenium, cobalt nanoparticles, and nitrogen codoped porous carbon (Ru-pCo@NC) are prepared with bimetallic zeolite imidazole frameworks (ZnCo-ZIF) as the precursor. Thus, the prepared Ru-pCo@NC catalyst with a low Ru loading of 3.13 wt% exhibits impressive HER catalytic behavior in 1 M KOH, with an overpotential of only 30 mV at the current density of 10 mA cm−2, Tafel slope as low as 32.1 mV dec−1, and superior stability for long-time running with a commercial 20 wt% Pt/C. The excellent electrocatalytic properties are primarily by virtue of the highly specific surface area and porosity of carbon support, uniformly dispersed Ru active species, and rapid reaction kinetics of the interaction between Ru and O. Full article
(This article belongs to the Special Issue Inorganic Materials in Nanotechnology: Fabrication, Characterization and Application)
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31 pages, 22082 KiB  
Review
Materials, Electrical Performance, Mechanisms, Applications, and Manufacturing Approaches for Flexible Strain Sensors
by Fei Han, Min Li, Huaiyu Ye and Guoqi Zhang
Nanomaterials 2021, 11(5), 1220; https://doi.org/10.3390/nano11051220 - 5 May 2021
Cited by 57 | Viewed by 8868
Abstract
With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As [...] Read more.
With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As a core member within the wearable electronics family, flexible strain sensors play an essential role in the structure design and functional optimization. To further enhance the stretchability, flexibility, sensitivity, and electricity performances of the flexible strain sensors, enormous efforts have been done covering the materials design, manufacturing approaches and various applications. Thus, this review summarizes the latest advances in flexible strain sensors over recent years from the material, application, and manufacturing strategies. Firstly, the critical parameters measuring the performances of flexible strain sensors and materials development contains different flexible substrates, new nano- and hybrid- materials are introduced. Then, the developed working mechanisms, theoretical analysis, and computational simulation are presented. Next, based on different material design, diverse applications including human motion detection and health monitoring, soft robotics and human-machine interface, implantable devices, and biomedical applications are highlighted. Finally, synthesis consideration of the massive production industry of flexible strain sensors in the future; different fabrication approaches that are fully expected are classified and discussed. Full article
(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)
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12 pages, 2166 KiB  
Article
An Inverted Honeycomb Plasmonic Lattice as an Efficient Refractive Index Sensor
by Javier Rodríguez-Álvarez, Lorenzo Gnoatto, Marc Martínez-Castells, Albert Guerrero, Xavier Borrisé, Arantxa Fraile Rodríguez, Xavier Batlle and Amílcar Labarta
Nanomaterials 2021, 11(5), 1217; https://doi.org/10.3390/nano11051217 - 4 May 2021
Cited by 2 | Viewed by 3232
Abstract
We present an efficient refractive index sensor consisting of a heterostructure that contains an Au inverted honeycomb lattice as a main sensing element. Our design aims at maximizing the out-of-plane near-field distributions of the collective modes of the lattice mapping the sensor surroundings. [...] Read more.
We present an efficient refractive index sensor consisting of a heterostructure that contains an Au inverted honeycomb lattice as a main sensing element. Our design aims at maximizing the out-of-plane near-field distributions of the collective modes of the lattice mapping the sensor surroundings. These modes are further enhanced by a patterned SiO2 layer with the same inverted honeycomb lattice, an SiO2 spacer, and an Au mirror underneath the Au sensing layer that contribute to achieving a high performance. The optical response of the heterostructure was studied by numerical simulation. The results corresponding to one of the collective modes showed high sensitivity values ranging from 99 to 395 nm/RIU for relatively thin layers of test materials within 50 and 200 nm. In addition, the figure of merit of the sensor detecting slight changes of the refractive index of a water medium at a fixed wavelength was as high as 199 RIU−1. As an experimental proof of concept, the heterostructure was manufactured by a simple method based on electron beam lithography and the measured optical response reproduces the simulations. This work paves the way for improving both the sensitivity of plasmonic sensors and the signal of some enhanced surface spectroscopies. Full article
(This article belongs to the Special Issue Plasmonic Nanostructures and Their Applications)
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11 pages, 1198 KiB  
Article
Beyond Nitrogen in the Oxygen Reduction Reaction on Nitrogen-Doped Carbons: A NEXAFS Investigation
by Eugenia Tanasa, Florentina Iuliana Maxim, Tugce Erniyazov, Matei-Tom Iacob, Tomáš Skála, Liviu Cristian Tanase, Cătălin Ianăși, Cristina Moisescu, Cristina Miron, Ioan Ardelean, Vlad-Andrei Antohe, Eugenia Fagadar-Cosma and Serban N. Stamatin
Nanomaterials 2021, 11(5), 1198; https://doi.org/10.3390/nano11051198 - 1 May 2021
Cited by 8 | Viewed by 3060
Abstract
Polymer electrolyte membrane fuel cells require cheap and active electrocatalysts to drive the oxygen reduction reaction. Nitrogen-doped carbons have been extensively studied regarding their oxygen reduction reaction. The work at hand looks beyond the nitrogen chemistry and brings to light the role of [...] Read more.
Polymer electrolyte membrane fuel cells require cheap and active electrocatalysts to drive the oxygen reduction reaction. Nitrogen-doped carbons have been extensively studied regarding their oxygen reduction reaction. The work at hand looks beyond the nitrogen chemistry and brings to light the role of oxygen. Nitrogen-doped nanocarbons were obtained by a radio-frequency plasma route at 0, 100, 250, and 350 W. The lateral size of the graphitic domain, determined from Raman spectroscopy, showed that the nitrogen plasma treatment decreased the crystallite size. Synchrotron radiation photoelectron spectroscopy showed a similar nitrogen chemistry, albeit the nitrogen concentration increased with the plasma power. Lateral crystallite size and several nitrogen moieties were plotted against the onset potential determined from oxygen reduction reaction curves. There was no correlation between the electrochemical activity and the sample structure, as determine from Raman and synchrotron radiation photoelectron spectroscopy. Near-edge X-ray absorption fine structure (NEXAFS) was performed to unravel the carbon and nitrogen local structure. A difference analysis of the NEXAFS spectra showed that the oxygen surrounding the pyridinic nitrogen was critical in achieving high onset potentials. The work shows that there were more factors at play, other than carbon organization and nitrogen chemistry. Full article
(This article belongs to the Special Issue Nanoparticles for Electrocatalysts)
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22 pages, 5251 KiB  
Article
Accessible Silver-Iron Oxide Nanoparticles as a Nanomaterial for Supported Liquid Membranes
by Ioana Alina Dimulescu (Nica), Aurelia Cristina Nechifor, Cristina Bǎrdacǎ (Urducea), Ovidiu Oprea, Dumitru Paşcu, Eugenia Eftimie Totu, Paul Constantin Albu, Gheorghe Nechifor and Simona Gabriela Bungău
Nanomaterials 2021, 11(5), 1204; https://doi.org/10.3390/nano11051204 - 1 May 2021
Cited by 29 | Viewed by 3362
Abstract
The present study introduces the process performances of nitrophenols pertraction using new liquid supported membranes under the action of a magnetic field. The membrane system is based on the dispersion of silver–iron oxide nanoparticles in n-alcohols supported on hollow microporous polypropylene fibers. The [...] Read more.
The present study introduces the process performances of nitrophenols pertraction using new liquid supported membranes under the action of a magnetic field. The membrane system is based on the dispersion of silver–iron oxide nanoparticles in n-alcohols supported on hollow microporous polypropylene fibers. The iron oxide–silver nanoparticles are obtained directly through cyclic voltammetry electrolysis run in the presence of soluble silver complexes ([AgCl2]−; [Ag(S2O3)2]3−; [Ag(NH3)2]+) and using pure iron electrodes. The nanostructured particles are characterized morphologically and structurally by scanning electron microscopy (SEM and HFSEM), EDAX, XRD, and thermal analysis (TG, DSC). The performances of the nitrophenols permeation process are investigated in a variable magnetic field. These studies show that the flux and extraction efficiency have the highest values for the membrane system embedding iron oxide–silver nanoparticles obtained electrochemically in the presence of [Ag(NH3)2]+ electrolyte. It is demonstrated that the total flow of nitrophenols through the new membrane system depends on diffusion, convection, and silver-assisted transport. Full article
(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)
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14 pages, 3467 KiB  
Article
Highly Conductive Al/Al Interfaces in Ultrafine Grained Al Compact Prepared by Low Oxygen Powder Metallurgy Technique
by Dasom Kim, Yusuke Hirayama, Zheng Liu, Hansang Kwon, Makoto Kobashi and Kenta Takagi
Nanomaterials 2021, 11(5), 1182; https://doi.org/10.3390/nano11051182 - 30 Apr 2021
Cited by 5 | Viewed by 2512
Abstract
The low oxygen powder metallurgy technique makes it possible to prepare full-dense ultrafine-grained (UFG) Al compacts with an average grain size of 160 nm by local surface bonding at a substantially lower temperature of 423 K from an Al nanopowder prepared by a [...] Read more.
The low oxygen powder metallurgy technique makes it possible to prepare full-dense ultrafine-grained (UFG) Al compacts with an average grain size of 160 nm by local surface bonding at a substantially lower temperature of 423 K from an Al nanopowder prepared by a low oxygen induction thermal plasma process. By atomic level analysis using transmission electron microscopy, it was found that there was almost no oxide layer at the Al/Al interfaces (grain boundaries) in UFG Al compact. The electrical conductivity of the UFG Al compact reached 3.5 × 107 S/m, which is the same level as that of the cast Al bulk. The Vickers hardness of the UFG Al compact of 1078 MPa, which is 8 times that of the cast Al bulk, could be explained by the Hall–Petch law. In addition, fracture behavior was analyzed by conducting a small punch test. The as-sintered UFG Al compact initially fractured before reaching its ultimate strength due to its large number of grain boundaries with a high misorientation angle. Ultimate strength and elongation were enhanced to 175 MPa and 24%, respectively, by reduction of grain boundaries after annealing, indicating that high compatibility of strength and elongation can be realized by appropriate microstructure control. Full article
(This article belongs to the Section Synthesis, Interfaces and Nanostructures)
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13 pages, 3937 KiB  
Communication
Functionalizable Glyconanoparticles for a Versatile Redox Platform
by Marie Carrière, Paulo Henrique M. Buzzetti, Karine Gorgy, Muhammad Mumtaz, Christophe Travelet, Redouane Borsali and Serge Cosnier
Nanomaterials 2021, 11(5), 1162; https://doi.org/10.3390/nano11051162 - 29 Apr 2021
Cited by 7 | Viewed by 3333
Abstract
A series of new glyconanoparticles (GNPs) was obtained by self-assembly by direct nanoprecipitation of a mixture of two carbohydrate amphiphilic copolymers consisting of polystyrene-block-β-cyclodextrin and polystyrene-block-maltoheptaose with different mass ratios, respectively 0–100, 10–90, 50–50 and 0–100%. Characterizations for all these GNPs were achieved [...] Read more.
A series of new glyconanoparticles (GNPs) was obtained by self-assembly by direct nanoprecipitation of a mixture of two carbohydrate amphiphilic copolymers consisting of polystyrene-block-β-cyclodextrin and polystyrene-block-maltoheptaose with different mass ratios, respectively 0–100, 10–90, 50–50 and 0–100%. Characterizations for all these GNPs were achieved using dynamic light scattering, scanning and transmission electron microscopy techniques, highlighting their spherical morphology and their nanometric size (diameter range 20–40 nm). In addition, by using the inclusion properties of cyclodextrin, these glyconanoparticles were successfully post-functionalized using a water-soluble redox compound, such as anthraquinone sulfonate (AQS) and characterized by cyclic voltammetry. The resulting glyconanoparticles exhibit the classical electroactivity of free AQS in solution. The amount of AQS immobilized by host–guest interactions is proportional to the percentage of polystyrene-block-β-cyclodextrin entering into the composition of GNPs. The modulation of the surface density of the β-cyclodextrin at the shell of the GNPs may constitute an attractive way for the elaboration of different electroactive GNPs and even GNPs modified by biotinylated proteins. Full article
(This article belongs to the Section Nanocomposite Materials)
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8 pages, 4088 KiB  
Article
Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction
by Georgia Basina, Hafsa Khurshid, Nikolaos Tzitzios, George Hadjipanayis and Vasileios Tzitzios
Nanomaterials 2021, 11(5), 1141; https://doi.org/10.3390/nano11051141 - 28 Apr 2021
Cited by 4 | Viewed by 2906
Abstract
Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results [...] Read more.
Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids’ surface functionalization in a nonpolar solvent. Full article
(This article belongs to the Special Issue Synthesis, Development and Characterization of Magnetic Nanomaterials)
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13 pages, 3803 KiB  
Article
Straightforward Patterning of Functional Polymers by Sequential Nanosecond Pulsed Laser Irradiation
by Edgar Gutiérrez-Fernández, Tiberio A. Ezquerra, Aurora Nogales and Esther Rebollar
Nanomaterials 2021, 11(5), 1123; https://doi.org/10.3390/nano11051123 - 27 Apr 2021
Cited by 8 | Viewed by 3186
Abstract
Laser-based methods have demonstrated to be effective in the fabrication of surface micro- and nanostructures, which have a wide range of applications, such as cell culture, sensors or controlled wettability. One laser-based technique used for micro- and nanostructuring of surfaces is the formation [...] Read more.
Laser-based methods have demonstrated to be effective in the fabrication of surface micro- and nanostructures, which have a wide range of applications, such as cell culture, sensors or controlled wettability. One laser-based technique used for micro- and nanostructuring of surfaces is the formation of laser-induced periodic surface structures (LIPSS). LIPSS are formed upon repetitive irradiation at fluences well below the ablation threshold and in particular, linear structures are formed in the case of irradiation with linearly polarized laser beams. In this work, we report on the simple fabrication of a library of ordered nanostructures in a polymer surface by repeated irradiation using a nanosecond pulsed laser operating in the UV and visible region in order to obtain nanoscale-controlled functionality. By using a combination of pulses at different wavelengths and sequential irradiation with different polarization orientations, it is possible to obtain different geometries of nanostructures, in particular linear gratings, grids and arrays of nanodots. We use this experimental approach to nanostructure the semiconductor polymer poly(3-hexylthiophene) (P3HT) and the ferroelectric copolymer poly[(vinylidenefluoride-co-trifluoroethylene] (P(VDF-TrFE)) since nanogratings in semiconductor polymers, such as P3HT and nanodots, in ferroelectric systems are viewed as systems with potential applications in organic photovoltaics or non-volatile memories. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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16 pages, 14648 KiB  
Article
Modulation of Macrophage Polarization by Carbon Nanodots and Elucidation of Carbon Nanodot Uptake Routes in Macrophages
by Andrew Dunphy, Kamal Patel, Sarah Belperain, Aubrey Pennington, Norman H. L. Chiu, Ziyu Yin, Xuewei Zhu, Brandon Priebe, Shaomin Tian, Jianjun Wei, Xianwen Yi and Zhenquan Jia
Nanomaterials 2021, 11(5), 1116; https://doi.org/10.3390/nano11051116 - 26 Apr 2021
Cited by 11 | Viewed by 3350
Abstract
Atherosclerosis represents an ever-present global concern, as it is a leading cause of cardiovascular disease and an immense public welfare issue. Macrophages play a key role in the onset of the disease state and are popular targets in vascular research and therapeutic treatment. [...] Read more.
Atherosclerosis represents an ever-present global concern, as it is a leading cause of cardiovascular disease and an immense public welfare issue. Macrophages play a key role in the onset of the disease state and are popular targets in vascular research and therapeutic treatment. Carbon nanodots (CNDs) represent a type of carbon-based nanomaterial and have garnered attention in recent years for potential in biomedical applications. This investigation serves as a foremost attempt at characterizing the interplay between macrophages and CNDs. We have employed THP-1 monocyte-derived macrophages as our target cell line representing primary macrophages in the human body. Our results showcase that CNDs are non-toxic at a variety of doses. THP-1 monocytes were differentiated into macrophages by treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) and co-treatment with 0.1 mg/mL CNDs. This co-treatment significantly increased the expression of CD 206 and CD 68 (key receptors involved in phagocytosis) and increased the expression of CCL2 (a monocyte chemoattractant and pro-inflammatory cytokine). The phagocytic activity of THP-1 monocyte-derived macrophages co-treated with 0.1 mg/mL CNDs also showed a significant increase. Furthermore, this study also examined potential entrance routes of CNDs into macrophages. We have demonstrated an inhibition in the uptake of CNDs in macrophages treated with nocodazole (microtubule disruptor), N-phenylanthranilic acid (chloride channel blocker), and mercury chloride (aquaporin channel inhibitor). Collectively, this research provides evidence that CNDs cause functional changes in macrophages and indicates a variety of potential entrance routes. Full article
(This article belongs to the Special Issue Nanomaterials for Drug Delivery and Cancer Therapy)
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25 pages, 10341 KiB  
Article
Superparamagnetic ZnFe2O4 Nanoparticles-Reduced Graphene Oxide-Polyurethane Resin Based Nanocomposites for Electromagnetic Interference Shielding Application
by Raghvendra Singh Yadav, Anju, Thaiskang Jamatia, Ivo Kuřitka, Jarmila Vilčáková, David Škoda, Pavel Urbánek, Michal Machovský, Milan Masař, Michal Urbánek, Lukas Kalina and Jaromir Havlica
Nanomaterials 2021, 11(5), 1112; https://doi.org/10.3390/nano11051112 - 25 Apr 2021
Cited by 28 | Viewed by 5178
Abstract
Superparamagnetic ZnFe2O4 spinel ferrite nanoparticles were prepared by the sonochemical synthesis method at different ultra-sonication times of 25 min (ZS25), 50 min (ZS50), and 100 min (ZS100). The structural properties of ZnFe2O4 spinel ferrite nanoparticles were controlled [...] Read more.
Superparamagnetic ZnFe2O4 spinel ferrite nanoparticles were prepared by the sonochemical synthesis method at different ultra-sonication times of 25 min (ZS25), 50 min (ZS50), and 100 min (ZS100). The structural properties of ZnFe2O4 spinel ferrite nanoparticles were controlled via sonochemical synthesis time. The average crystallite size increases from 3.0 nm to 4.0 nm with a rise of sonication time from 25 min to 100 min. The change of physical properties of ZnFe2O4 nanoparticles with the increase of sonication time was observed. The prepared ZnFe2O4 nanoparticles show superparamagnetic behavior. The prepared ZnFe2O4 nanoparticles (ZS25, ZS50, and ZS100) and reduced graphene oxide (RGO) were embedded in a polyurethane resin (PUR) matrix as a shield against electromagnetic pollution. The ultra-sonication method has been used for the preparation of nanocomposites. The total shielding effectiveness (SET) value for the prepared nanocomposites was studied at a thickness of 1 mm in the range of 8.2–12.4 GHz. The high attenuation constant (α) value of the prepared ZS100-RGO-PUR nanocomposite as compared with other samples recommended high absorption of electromagnetic waves. The existence of electric-magnetic nanofillers in the resin matrix delivered the inclusive acts of magnetic loss, dielectric loss, appropriate attenuation constant, and effective impedance matching. The synergistic effect of ZnFe2O4 and RGO in the PUR matrix led to high interfacial polarization and, consequently, significant absorption of the electromagnetic waves. The outcomes and methods also assure an inventive and competent approach to develop lightweight and flexible polyurethane resin matrix-based nanocomposites, consisting of superparamagnetic zinc ferrite nanoparticles and reduced graphene oxide as a shield against electromagnetic pollution. Full article
(This article belongs to the Special Issue Advanced Magnetic Nanocomposites: Structural, Physical Properties and Application)
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10 pages, 2247 KiB  
Article
High-Performance Non-Volatile InGaZnO Based Flash Memory Device Embedded with a Monolayer Au Nanoparticles
by Muhammad Naqi, Nayoung Kwon, Sung Hyeon Jung, Pavan Pujar, Hae Won Cho, Yong In Cho, Hyung Koun Cho, Byungkwon Lim and Sunkook Kim
Nanomaterials 2021, 11(5), 1101; https://doi.org/10.3390/nano11051101 - 24 Apr 2021
Cited by 13 | Viewed by 4858
Abstract
Non-volatile memory (NVM) devices based on three-terminal thin-film transistors (TFTs) have gained extensive interest in memory applications due to their high retained characteristics, good scalability, and high charge storage capacity. Herein, we report a low-temperature (<100 °C) processed top-gate TFT-type NVM device using [...] Read more.
Non-volatile memory (NVM) devices based on three-terminal thin-film transistors (TFTs) have gained extensive interest in memory applications due to their high retained characteristics, good scalability, and high charge storage capacity. Herein, we report a low-temperature (<100 °C) processed top-gate TFT-type NVM device using indium gallium zinc oxide (IGZO) semiconductor with monolayer gold nanoparticles (AuNPs) as a floating gate layer to obtain reliable memory operations. The proposed NVM device exhibits a high memory window (ΔVth) of 13.7 V when it sweeps from −20 V to +20 V back and forth. Additionally, the material characteristics of the monolayer AuNPs (floating gate layer) and IGZO film (semiconductor layer) are confirmed using transmission electronic microscopy (TEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) techniques. The memory operations in terms of endurance and retention are obtained, revealing highly stable endurance properties of the device up to 100 P/E cycles by applying pulses (±20 V, duration of 100 ms) and reliable retention time up to 104 s. The proposed NVM device, owing to the properties of large memory window, stable endurance, and high retention time, enables an excellent approach in futuristic non-volatile memory technology. Full article
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15 pages, 7353 KiB  
Article
Thermoelectric Energy Harvesting from Single-Walled Carbon Nanotube Alkali-Activated Nanocomposites Produced from Industrial Waste Materials
by Maliheh Davoodabadi, Ioanna Vareli, Marco Liebscher, Lazaros Tzounis, Massimo Sgarzi, Alkiviadis S. Paipetis, Jian Yang, Gianaurelio Cuniberti and Viktor Mechtcherine
Nanomaterials 2021, 11(5), 1095; https://doi.org/10.3390/nano11051095 - 23 Apr 2021
Cited by 22 | Viewed by 4675
Abstract
A waste-originated one-part alkali-activated nanocomposite is introduced herein as a novel thermoelectric material. For this purpose, single-walled carbon nanotubes (SWCNTs) were utilized as nanoinclusions to create an electrically conductive network within the investigated alkali-activated construction material. Thermoelectric and microstructure characteristics of SWCNT-alkali-activated nanocomposites [...] Read more.
A waste-originated one-part alkali-activated nanocomposite is introduced herein as a novel thermoelectric material. For this purpose, single-walled carbon nanotubes (SWCNTs) were utilized as nanoinclusions to create an electrically conductive network within the investigated alkali-activated construction material. Thermoelectric and microstructure characteristics of SWCNT-alkali-activated nanocomposites were assessed after 28 days. Nanocomposites with 1.0 wt.% SWCNTs exhibited a multifunctional behavior, a combination of structural load-bearing, electrical conductivity, and thermoelectric response. These nanocomposites (1.0 wt.%) achieved the highest thermoelectric performance in terms of power factor (PF), compared to the lower SWCNTs’ incorporations, namely 0.1 and 0.5 wt.%. The measured electrical conductivity (σ) and Seebeck coefficient (S) were 1660 S·m−1 and 15.8 µV·K−1, respectively, which led to a power factor of 0.414 μW·m−1·K−2. Consequently, they have been utilized as the building block of a thermoelectric generator (TEG) device, which demonstrated a maximum power output (Pout) of 0.695 µW, with a power density (PD) of 372 nW·m−2, upon exposure to a temperature gradient of 60 K. The presented SWCNT-alkali-activated nanocomposites could establish the pathway towards waste thermal energy harvesting and future sustainable civil engineering structures. Full article
(This article belongs to the Special Issue Novel Thermoelectric Nanomaterials, Nanocomposites and Advanced Fabrication Techniques for Thermoelectric Generator (TEG) Devices)
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10 pages, 3700 KiB  
Article
On the Insignificant Role of the Oxidation Process on Ultrafast High-Spatial-Frequency LIPSS Formation on Tungsten
by Priya Dominic, Florent Bourquard, Stéphanie Reynaud, Arnaud Weck, Jean-Philippe Colombier and Florence Garrelie
Nanomaterials 2021, 11(5), 1069; https://doi.org/10.3390/nano11051069 - 22 Apr 2021
Cited by 20 | Viewed by 3465
Abstract
The presence of surface oxides on the formation of laser-induced periodic surface structures (LIPSS) is regularly advocated to favor or even trigger the formation of high-spatial-frequency LIPSS (HSFL) during ultrafast laser-induced nano-structuring. This paper reports the effect of the laser texturing environment on [...] Read more.
The presence of surface oxides on the formation of laser-induced periodic surface structures (LIPSS) is regularly advocated to favor or even trigger the formation of high-spatial-frequency LIPSS (HSFL) during ultrafast laser-induced nano-structuring. This paper reports the effect of the laser texturing environment on the resulting surface oxides and its consequence for HSFLs formation. Nanoripples are produced on tungsten samples using a Ti:sapphire femtosecond laser under atmospheres with varying oxygen contents. Specifically, ambient, 10 mbar pressure of air, nitrogen and argon, and 10−7 mbar vacuum pressure are used. In addition, removal of any native oxide layer is achieved using plasma sputtering prior to laser irradiation. The resulting HSFLs have a sub-100 nm periodicity and sub 20 nm amplitude. The experiments reveal the negligible role of oxygen during the HSFL formation and clarifies the significant role of ambient pressure in the resulting HSFLs period. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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37 pages, 2397 KiB  
Review
Gold Nanoparticles Synthesis and Antimicrobial Effect on Fibrous Materials
by Behnaz Mehravani, Ana Isabel Ribeiro and Andrea Zille
Nanomaterials 2021, 11(5), 1067; https://doi.org/10.3390/nano11051067 - 21 Apr 2021
Cited by 59 | Viewed by 6612
Abstract
Depositing nanoparticles in textiles have been a promising strategy to achieve multifunctional materials. Particularly, antimicrobial properties are highly valuable due to the emergence of new pathogens and the spread of existing ones. Several methods have been used to functionalize textile materials with gold [...] Read more.
Depositing nanoparticles in textiles have been a promising strategy to achieve multifunctional materials. Particularly, antimicrobial properties are highly valuable due to the emergence of new pathogens and the spread of existing ones. Several methods have been used to functionalize textile materials with gold nanoparticles (AuNPs). Therefore, this review highlighted the most used methods for AuNPs preparation and the current studies on the topic in order to obtain AuNPs with suitable properties for antimicrobial applications and minimize the environmental concerns in their production. Reporting the detailed information on the functionalization of fabrics, yarns, and fibers with AuNPs by different methods to improve the antimicrobial properties was the central objective. The studies combining AuNPs and textile materials have opened valuable opportunities to develop antimicrobial materials for health and hygiene products, as infection control and barrier material, with improved properties. Future studies are needed to amplify the antimicrobial effect of AuNPs onto textiles and minimize the concerns related to the synthesis. Full article
(This article belongs to the Special Issue Inorganic Nanoparticles: Synthesis, Characterization and Nanoscopic Properties)
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17 pages, 3310 KiB  
Review
Revealing the Exciton Fine Structure in Lead Halide Perovskite Nanocrystals
by Lei Hou, Philippe Tamarat and Brahim Lounis
Nanomaterials 2021, 11(4), 1058; https://doi.org/10.3390/nano11041058 - 20 Apr 2021
Cited by 25 | Viewed by 7926
Abstract
Lead-halide perovskite nanocrystals (NCs) are attractive nano-building blocks for photovoltaics and optoelectronic devices as well as quantum light sources. Such developments require a better knowledge of the fundamental electronic and optical properties of the band-edge exciton, whose fine structure has long been debated. [...] Read more.
Lead-halide perovskite nanocrystals (NCs) are attractive nano-building blocks for photovoltaics and optoelectronic devices as well as quantum light sources. Such developments require a better knowledge of the fundamental electronic and optical properties of the band-edge exciton, whose fine structure has long been debated. In this review, we give an overview of recent magneto-optical spectroscopic studies revealing the entire excitonic fine structure and relaxation mechanisms in these materials, using a single-NC approach to get rid of their inhomogeneities in morphology and crystal structure. We highlight the prominent role of the electron-hole exchange interaction in the order and splitting of the bright triplet and dark singlet exciton sublevels and discuss the effects of size, shape anisotropy and dielectric screening on the fine structure. The spectral and temporal manifestations of thermal mixing between bright and dark excitons allows extracting the specific nature and strength of the exciton–phonon coupling, which provides an explanation for their remarkably bright photoluminescence at low temperature although the ground exciton state is optically inactive. We also decipher the spectroscopic characteristics of other charge complexes whose recombination contributes to photoluminescence. With the rich knowledge gained from these experiments, we provide some perspectives on perovskite NCs as quantum light sources. Full article
(This article belongs to the Special Issue Nanocrystals: Synthesis, Properties and Applications)
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8 pages, 1699 KiB  
Article
Design of Multifunctional Janus Metasurface Based on Subwavelength Grating
by Ruonan Ji, Chuan Jin, Kun Song, Shao-Wei Wang and Xiaopeng Zhao
Nanomaterials 2021, 11(4), 1034; https://doi.org/10.3390/nano11041034 - 19 Apr 2021
Cited by 19 | Viewed by 3780
Abstract
In this paper, a Janus metasurface is designed by breaking the structural symmetry based on the polarization selection property of subwavelength grating. The structure comprises three layers: a top layer having a metallic nanostructure, a dielectric spacer, and a bottom layer having subwavelength [...] Read more.
In this paper, a Janus metasurface is designed by breaking the structural symmetry based on the polarization selection property of subwavelength grating. The structure comprises three layers: a top layer having a metallic nanostructure, a dielectric spacer, and a bottom layer having subwavelength grating. For a forward incidence, the metal-insulator-metal (MIM) structure operates as a gap plasmonic cavity if the linearly polarized (LP) component is parallel to the grating wires. It also acts as a high-efficiency dual-layer grating polarizer for the orthogonal LP component. For the backward incidence, the high reflectance of the grating blocks the function of the gap plasmonic cavity, leading to its pure functioning as a polarizer. A bifunctional Janus metasurface for 45 degrees beam deflector and polarizer, with a transmission of 0.87 and extinction ratio of 3840, is designed at 1.55 μm and is investigated to prove the validity of the proposed strategy. Moreover, the proposed metasurface can be cascaded to achieve more flexible functions since these functions are independent in terms of operational mechanism and structural parameters. A trifunctional Janus metasurface that acts as a focusing lens, as a reflector, and as a polarizer is designed based on this strategy. The proposed metasurface and the design strategy provide convenience and flexibility in the design of multifunctional, miniaturized, and integrated optical components for polarization-related analysis and for detection systems. Full article
(This article belongs to the Special Issue State-of-the-Art Nanophotonics Materials and Devices in China)
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18 pages, 3114 KiB  
Article
Multifunctional Magnetic Nanocolloids for Hybrid Solar-Thermoelectric Energy Harvesting
by Elisa Sani, Maria Raffaella Martina, Thomas J. Salez, Sawako Nakamae, Emmanuelle Dubois and Véronique Peyre
Nanomaterials 2021, 11(4), 1031; https://doi.org/10.3390/nano11041031 - 18 Apr 2021
Cited by 16 | Viewed by 4383
Abstract
Present environmental issues force the research to explore radically new concepts in sustainable and renewable energy production. In the present work, a functional fluid consisting of a stable colloidal suspension of maghemite magnetic nanoparticles in water was characterized from the points of view [...] Read more.
Present environmental issues force the research to explore radically new concepts in sustainable and renewable energy production. In the present work, a functional fluid consisting of a stable colloidal suspension of maghemite magnetic nanoparticles in water was characterized from the points of view of thermoelectrical and optical properties, to evaluate its potential for direct electricity generation from thermoelectric effect enabled by the absorption of sunlight. These nanoparticles were found to be an excellent solar radiation absorber and simultaneously a thermoelectric power-output enhancer with only a very small volume fraction when the fluid was heated from the top. These findings demonstrate the investigated nanofluid’s high promise as a heat transfer fluid for co-generating heat and power in brand new hybrid flat-plate solar thermal collectors where top-heating geometry is imposed. Full article
(This article belongs to the Special Issue Future and Prospects in Nanofluids Research)
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12 pages, 2560 KiB  
Article
Carbon-Nanotube-Coated Surface Electrodes for Cortical Recordings In Vivo
by Katharina Foremny, Wiebke S. Konerding, Ailke Behrens, Peter Baumhoff, Ulrich P. Froriep, Andrej Kral and Theodor Doll
Nanomaterials 2021, 11(4), 1029; https://doi.org/10.3390/nano11041029 - 17 Apr 2021
Cited by 9 | Viewed by 3200
Abstract
Current developments of electrodes for neural recordings address the need of biomedical research and applications for high spatial acuity in electrophysiological recordings. One approach is the usage of novel materials to overcome electrochemical constraints of state-of-the-art metal contacts. Promising materials are carbon nanotubes [...] Read more.
Current developments of electrodes for neural recordings address the need of biomedical research and applications for high spatial acuity in electrophysiological recordings. One approach is the usage of novel materials to overcome electrochemical constraints of state-of-the-art metal contacts. Promising materials are carbon nanotubes (CNTs), as they are well suited for neural interfacing. The CNTs increase the effective contact surface area to decrease high impedances while keeping minimal contact diameters. However, to prevent toxic dissolving of CNTs, an appropriate surface coating is required. In this study, we tested flexible surface electrocorticographic (ECoG) electrodes, coated with a CNT-silicone rubber composite. First, we describe the outcome of surface etching, which exposes the contact nanostructure while anchoring the CNTs. Subsequently, the ECoG electrodes were used for acute in vivo recordings of auditory evoked potentials from the guinea pig auditory cortex. Both the impedances and the signal-to-noise ratios of coated contacts were similar to uncoated gold contacts. This novel approach for a safe application of CNTs, embedded in a surface etched silicone rubber, showed promising results but did not lead to improvements during acute recordings. Full article
(This article belongs to the Special Issue Biomedical Applications of Graphene-Based Nanomaterials)
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12 pages, 6533 KiB  
Article
Self-Organization Regimes Induced by Ultrafast Laser on Surfaces in the Tens of Nanometer Scales
by Anthony Nakhoul, Claire Maurice, Marion Agoyan, Anton Rudenko, Florence Garrelie, Florent Pigeon and Jean-Philippe Colombier
Nanomaterials 2021, 11(4), 1020; https://doi.org/10.3390/nano11041020 - 16 Apr 2021
Cited by 30 | Viewed by 4114
Abstract
A laser-irradiated surface is the paradigm of a self-organizing system, as coherent, aligned, chaotic, and complex patterns emerge at the microscale and even the nanoscale. A spectacular manifestation of dissipative structures consists of different types of randomly and periodically distributed nanostructures that arise [...] Read more.
A laser-irradiated surface is the paradigm of a self-organizing system, as coherent, aligned, chaotic, and complex patterns emerge at the microscale and even the nanoscale. A spectacular manifestation of dissipative structures consists of different types of randomly and periodically distributed nanostructures that arise from a homogeneous metal surface. The noninstantaneous response of the material reorganizes local surface topography down to tens of nanometers scale modifying long-range surface morphology on the impact scale. Under ultrafast laser irradiation with a regulated energy dose, the formation of nanopeaks, nanobumps, nanohumps and nanocavities patterns with 20–80 nm transverse size unit and up to 100 nm height are reported. We show that the use of crossed-polarized double laser pulse adds an extra dimension to the nanostructuring process as laser energy dose and multi-pulse feedback tune the energy gradient distribution, crossing critical values for surface self-organization regimes. The tiny dimensions of complex patterns are defined by the competition between the evolution of transient liquid structures generated in a cavitation process and the rapid resolidification of the surface region. Strongly influencing the light coupling, we reveal that initial surface roughness and type of roughness both play a crucial role in controlling the transient emergence of nanostructures during laser irradiation. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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17 pages, 30041 KiB  
Article
Characterization of Plasmonic Scattering, Luminescent Down-Shifting, and Metal-Enhanced Fluorescence and Applications on Silicon Solar Cells
by Wen-Jeng Ho, Jheng-Jie Liu and Jhih-Ciang Chen
Nanomaterials 2021, 11(4), 1013; https://doi.org/10.3390/nano11041013 - 15 Apr 2021
Cited by 5 | Viewed by 2583
Abstract
This paper studied characterized the plasmonic effects of silver nanoparticles (Ag-NPs), the luminescent down-shifting of Eu-doped phosphor particles, and the metal-enhanced fluorescence (MEF) achieved by combining the two processes to enhance the conversion efficiency of silicon solar cells. We obtained measurements of photoluminescence [...] Read more.
This paper studied characterized the plasmonic effects of silver nanoparticles (Ag-NPs), the luminescent down-shifting of Eu-doped phosphor particles, and the metal-enhanced fluorescence (MEF) achieved by combining the two processes to enhance the conversion efficiency of silicon solar cells. We obtained measurements of photoluminescence (PL) and external quantum efficiency (EQE) at room temperature to determine whether the fluorescence emissions intensity of Eu-doped phosphor was enhanced or quenched by excitation induced via surface plasmon resonance (SPR). Overall, fluorescence intensity was enhanced when the fluorescence emission band was strongly coupled to the SPR band of Ag-NPs and the two particles were separated by a suitable distance. We observed a 1.125× increase in PL fluorescence intensity at a wavelength of 514 nm and a 7.05% improvement in EQE (from 57.96% to 62.05%) attributable to MEF effects. The combined effects led to a 26.02% increase in conversion efficiency (from 10.23% to 12.89%) in the cell with spacer/NPs/SOG-phosphors and a 22.09% increase (from 10.23% to 12.48%) in the cell with spacer/SOG-phosphors, compared to the bare solar cell. This corresponds to an impressive 0.85% increase in absolute efficiency (from 12.04% to 12.89%), compared to the cell with only spacer/SOG. Full article
(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)
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12 pages, 1949 KiB  
Article
Probing the Surface Chemistry of Nanoporous Gold via Electrochemical Characterization and Atom Probe Tomography
by AmirHossein Foroozan-Ebrahimy, Brian Langelier and Roger Charles Newman
Nanomaterials 2021, 11(4), 1002; https://doi.org/10.3390/nano11041002 - 14 Apr 2021
Cited by 2 | Viewed by 3156
Abstract
Surface chemistry information is crucial in understanding catalytic and sensing mechanisms. However, resolving the outermost monolayer composition of metallic nanoporous materials is challenging due to the high tortuosity of their morphology. In this study, we first elaborate on the capabilities and limitations of [...] Read more.
Surface chemistry information is crucial in understanding catalytic and sensing mechanisms. However, resolving the outermost monolayer composition of metallic nanoporous materials is challenging due to the high tortuosity of their morphology. In this study, we first elaborate on the capabilities and limitations of atom probe tomography (APT) in resolving interfaces. Subsequently, an electrochemical approach is designed to characterize the surface composition of nanoporous gold (NPG), developed from dealloying an inexpensive precursor (95 at. % Ag, 5 at. % Au), by the means of aqueous electrochemical measurements of the selective electrosorption of sulfide ions, which react strongly with Ag, but to a significantly lesser extent with Au. Accordingly, cyclic voltammetry was performed at various scan rates on NPG in alkaline aqueous solutions (0.2 M NaOH; pH 13) in the presence and absence of 1 mM Na2S. Calibrations via similar voltammetric measurements on pure polycrystalline Ag and Au surfaces allowed for a quantitative estimation for the Ag surface coverage of NPG. The sensitivity threshold for the detection of the adsorbate–Ag interaction was assessed to be approximately 2% Ag surface coverage. As curves measured on NPG only showed featureless capacitive currents, no faradaic charge density associated with sulfide electrosorption could be detected. This study opens a new avenue to gain further insight into the monolayer surface coverage of metallic nanoporous materials and assists in enhancement of the interpretation of APT reconstructions. Full article
(This article belongs to the Special Issue Growth, Characterization, and Modelling of Nanostructures for Applications in Sensing)
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10 pages, 14327 KiB  
Article
Study on Performance Improvements in Perovskite-Based Ultraviolet Sensors Prepared Using Toluene Antisolvent and CH3NH3Cl
by Seong Gwan Shin, Chung Wung Bark and Hyung Wook Choi
Nanomaterials 2021, 11(4), 1000; https://doi.org/10.3390/nano11041000 - 13 Apr 2021
Cited by 13 | Viewed by 2914
Abstract
In this study, a simply structured perovskite-based ultraviolet C (UVC) sensor was prepared using a one-step, low-temperature solution-processing coating method. The UVC sensor utilized CH3NH3PbBr3 perovskite as the light-absorbing layer. To improve the characteristics of CH3NH [...] Read more.
In this study, a simply structured perovskite-based ultraviolet C (UVC) sensor was prepared using a one-step, low-temperature solution-processing coating method. The UVC sensor utilized CH3NH3PbBr3 perovskite as the light-absorbing layer. To improve the characteristics of CH3NH3PbBr3, an antisolvent process using toluene and the addition of CH3NH3Cl were introduced. The device with these modifications exhibited a response rise/fall time of 15.8/16.2 ms, mobility of 158.7 cm2/V·s, responsivity of 4.57 mA/W, detectivity of 1.02 × 1013 Jones, and external quantum efficiency of 22.32% under the 254-nm UV illumination. Therefore, this methodology could be a good approach in facilitating UVC detection. Full article
(This article belongs to the Section Nanophotonics Materials and Devices)
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24 pages, 9498 KiB  
Article
Numerical Study of Natural Convection Heat Transfer in a Porous Annulus Filled with a Cu-Nanofluid
by Lingyun Zhang, Yupeng Hu and Minghai Li
Nanomaterials 2021, 11(4), 990; https://doi.org/10.3390/nano11040990 - 12 Apr 2021
Cited by 17 | Viewed by 3447
Abstract
Natural convection heat transfer in a porous annulus filled with a Cu nanofluid has been investigated numerically. The Darcy–Brinkman and the energy transport equations are employed to describe the nanofluid motion and the heat transfer in the porous medium. Numerical results including the [...] Read more.
Natural convection heat transfer in a porous annulus filled with a Cu nanofluid has been investigated numerically. The Darcy–Brinkman and the energy transport equations are employed to describe the nanofluid motion and the heat transfer in the porous medium. Numerical results including the isotherms, streamlines, and heat transfer rate are obtained under the following parameters: Brownian motion, Rayleigh number (103–105), Darcy number (10−4–10−2), nanoparticle volume fraction (0.01–0.09), nanoparticle diameter (10–90 nm), porosity (0.1–0.9), and radius ratio (1.1–10). Results show that Brownian motion should be considered. The nanoparticle volume fraction has a positive effect on the heat transfer rate, especially with high Rayleigh number and Darcy number, while the nanoparticle diameter has an inverse influence. The heat transfer rate is enhanced with the increase of porosity. The radius ratio has a significant influence on the isotherms, streamlines, and heat transfer rate, and the rate is greatly enhanced with the increase of radius ratio. Full article
(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)
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10 pages, 5234 KiB  
Article
Enhanced Heat-Electric Conversion via Photonic-Assisted Radiative Cooling
by Jeng-Yi Lee, Chih-Ming Wang, Chieh-Lun Chi, Sheng-Rui Wu, Ya-Xun Lin, Mao-Kuo Wei and Chu-Hsuan Lin
Nanomaterials 2021, 11(4), 983; https://doi.org/10.3390/nano11040983 - 11 Apr 2021
Cited by 9 | Viewed by 2991
Abstract
In this paper, an inorganic polymer composite film is proposed as an effective radiative cooling device. The inherent absorption is enhanced by choosing an appropriately sized SiO2 microsphere with a diameter of 6 μm. The overall absorption at the transparent window of [...] Read more.
In this paper, an inorganic polymer composite film is proposed as an effective radiative cooling device. The inherent absorption is enhanced by choosing an appropriately sized SiO2 microsphere with a diameter of 6 μm. The overall absorption at the transparent window of the atmosphere is higher than 90%, as the concentration of SiO2–PMMA composite is 35 wt%. As a result, an effective radiative device is made by a spin coating process. Moreover, the device is stacked on the cold side of a thermoelectric generator chip. It is found that the temperature gradient can be increased via the effective radiative cooling process. An enhanced Seebeck effect is observed, and the corresponding output current can be enhanced 1.67-fold via the photonic-assisted radiative cooling. Full article
(This article belongs to the Special Issue State-of-the-Art Optical Properties and Applications of Metallic Nanostructures in Asia)
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23 pages, 4527 KiB  
Article
Synthesis of Polystyrene-Based Cationic Nanomaterials with Pro-Oxidant Cytotoxic Activity on Etoposide-Resistant Neuroblastoma Cells
by Silvana Alfei, Barbara Marengo, Giulia Elda Valenti and Cinzia Domenicotti
Nanomaterials 2021, 11(4), 977; https://doi.org/10.3390/nano11040977 - 10 Apr 2021
Cited by 19 | Viewed by 2632
Abstract
Drug resistance is a multifactorial phenomenon that limits the action of antibiotics and chemotherapeutics. Therefore, it is essential to develop new therapeutic strategies capable of inducing cytotoxic effects circumventing chemoresistance. In this regard, the employment of natural and synthetic cationic peptides and polymers [...] Read more.
Drug resistance is a multifactorial phenomenon that limits the action of antibiotics and chemotherapeutics. Therefore, it is essential to develop new therapeutic strategies capable of inducing cytotoxic effects circumventing chemoresistance. In this regard, the employment of natural and synthetic cationic peptides and polymers has given satisfactory results both in microbiology, as antibacterial agents, but also in the oncological field, resulting in effective treatment against several tumors, including neuroblastoma (NB). To this end, two polystyrene-based copolymers (P5, P7), containing primary ammonium groups, were herein synthetized and tested on etoposide-sensitive (HTLA-230) and etoposide-resistant (HTLA-ER) NB cells. Both copolymers were water-soluble and showed a positive surface charge due to nitrogen atoms, which resulted in protonation in the whole physiological pH range. Furthermore, P5 and P7 exhibited stability in solution, excellent buffer capacity, and nanosized particles, and they were able to reduce NB cell viability in a concentration-dependent way. Interestingly, a significant increase in reactive oxygen species (ROS) production was observed in both NB cell populations treated with P5 or P7, establishing for both copolymers an unequivocal correlation between cytotoxicity and ROS generation. Therefore, P5 and P7 could be promising template macromolecules for the development of new chemotherapeutic agents able to fight NB chemoresistance. Full article
(This article belongs to the Special Issue Nanoparticles for Bio-Medical Applications)
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21 pages, 4907 KiB  
Article
Synthesis of Poly(Malic Acid) Derivatives End-Functionalized with Peptides and Preparation of Biocompatible Nanoparticles to Target Hepatoma Cells
by Clarisse Brossard, Manuel Vlach, Elise Vène, Catherine Ribault, Vincent Dorcet, Nicolas Noiret, Pascal Loyer, Nicolas Lepareur and Sandrine Cammas-Marion
Nanomaterials 2021, 11(4), 958; https://doi.org/10.3390/nano11040958 - 9 Apr 2021
Cited by 15 | Viewed by 3232
Abstract
Recently, short synthetic peptides have gained interest as targeting agents in the design of site-specific nanomedicines. In this context, our work aimed at developing new tools for the diagnosis and/or therapy of hepatocellular carcinoma (HCC) by grafting the hepatotropic George Baker (GB) virus [...] Read more.
Recently, short synthetic peptides have gained interest as targeting agents in the design of site-specific nanomedicines. In this context, our work aimed at developing new tools for the diagnosis and/or therapy of hepatocellular carcinoma (HCC) by grafting the hepatotropic George Baker (GB) virus A (GBVA10-9) and Plasmodium circumsporozoite protein (CPB)-derived peptides to the biocompatible poly(benzyl malate), PMLABe. We successfully synthesized PMLABe derivatives end-functionalized with peptides GBVA10-9, CPB, and their corresponding scrambled peptides through a thiol/maleimide reaction. The corresponding nanoparticles (NPs), varying by the nature of the peptide (GBVA10-9, CPB, and their scrambled peptides) and the absence or presence of poly(ethylene glycol) were also successfully formulated using nanoprecipitation technique. NPs were further characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS) and transmission electron microscopy (TEM), highlighting a diameter lower than 150 nm, a negative surface charge, and a more or less spherical shape. Moreover, a fluorescent probe (DiD Oil) has been encapsulated during the nanoprecipitation process. Finally, preliminary in vitro internalisation assays using HepaRG hepatoma cells demonstrated that CPB peptide-functionalized PMLABe NPs were efficiently internalized by endocytosis, and that such nanoobjects may be promising drug delivery systems for the theranostics of HCC. Full article
(This article belongs to the Special Issue Development of Multifunctional Nanoparticles for Therapy and/or Diagnosis)
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10 pages, 2541 KiB  
Article
Li2(BH4)(NH2) Nanoconfined in SBA-15 as Solid-State Electrolyte for Lithium Batteries
by Qianyi Yang, Fuqiang Lu, Yulin Liu, Yijie Zhang, Xiujuan Wang, Yuepeng Pang and Shiyou Zheng
Nanomaterials 2021, 11(4), 946; https://doi.org/10.3390/nano11040946 - 8 Apr 2021
Cited by 9 | Viewed by 3391
Abstract
Solid electrolytes with high Li-ion conductivity and electrochemical stability are very important for developing high-performance all-solid-state batteries. In this work, Li2(BH4)(NH2) is nanoconfined in the mesoporous silica molecule sieve (SBA-15) using a melting–infiltration approach. This electrolyte exhibits [...] Read more.
Solid electrolytes with high Li-ion conductivity and electrochemical stability are very important for developing high-performance all-solid-state batteries. In this work, Li2(BH4)(NH2) is nanoconfined in the mesoporous silica molecule sieve (SBA-15) using a melting–infiltration approach. This electrolyte exhibits excellent Li-ion conduction properties, achieving a Li-ion conductivity of 5.0 × 10−3 S cm−1 at 55 °C, an electrochemical stability window of 0 to 3.2 V and a Li-ion transference number of 0.97. In addition, this electrolyte can enable the stable cycling of Li|Li2(BH4)(NH2)@SBA-15|TiS2 cells, which exhibit a reversible specific capacity of 150 mAh g−1 with a Coulombic efficiency of 96% after 55 cycles. Full article
(This article belongs to the Special Issue Advances in Nanomaterials for Lithium-Ion/Post-Lithium-Ion Batteries and Supercapacitors)
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17 pages, 3804 KiB  
Article
Gold-seeded Lithium Niobate Nanoparticles: Influence of Gold Surface Coverage on Second Harmonic Properties
by Rachael Taitt, Mathias Urbain, Zacharie Behel, Ana-María Pablo-Sainz-Ezquerra, Iryna Kandybka, Eloïse Millet, Nicolas Martinez-Rodriguez, Christelle Yeromonahos, Sandrine Beauquis, Ronan Le Dantec, Yannick Mugnier, Pierre-François Brevet, Yann Chevolot and Virginie Monnier
Nanomaterials 2021, 11(4), 950; https://doi.org/10.3390/nano11040950 - 8 Apr 2021
Cited by 8 | Viewed by 2831
Abstract
Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. [...] Read more.
Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO3 (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution. Full article
(This article belongs to the Special Issue Nanomaterials for Nonlinear Optics)
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14 pages, 2634 KiB  
Article
Investigations of Graphene and Nitrogen-Doped Graphene Enhanced Polycaprolactone 3D Scaffolds for Bone Tissue Engineering
by Weiguang Wang, Jun-Xiang Chen, Yanhao Hou, Paulo Bartolo and Wei-Hung Chiang
Nanomaterials 2021, 11(4), 929; https://doi.org/10.3390/nano11040929 - 6 Apr 2021
Cited by 14 | Viewed by 3700
Abstract
Scaffolds play a key role in tissue engineering applications. In the case of bone tissue engineering, scaffolds are expected to provide both sufficient mechanical properties to withstand the physiological loads, and appropriate bioactivity to stimulate cell growth. In order to further enhance cell–cell [...] Read more.
Scaffolds play a key role in tissue engineering applications. In the case of bone tissue engineering, scaffolds are expected to provide both sufficient mechanical properties to withstand the physiological loads, and appropriate bioactivity to stimulate cell growth. In order to further enhance cell–cell signaling and cell–material interaction, electro-active scaffolds have been developed based on the use of electrically conductive biomaterials or blending electrically conductive fillers to non-conductive biomaterials. Graphene has been widely used as functioning filler for the fabrication of electro-active bone tissue engineering scaffolds, due to its high electrical conductivity and potential to enhance both mechanical and biological properties. Nitrogen-doped graphene, a unique form of graphene-derived nanomaterials, presents significantly higher electrical conductivity than pristine graphene, and better surface hydrophilicity while maintaining a similar mechanical property. This paper investigates the synthesis and use of high-performance nitrogen-doped graphene as a functional filler of poly(ɛ-caprolactone) (PCL) scaffolds enabling to develop the next generation of electro-active scaffolds. Compared to PCL scaffolds and PCL/graphene scaffolds, these novel scaffolds present improved in vitro biological performance. Full article
(This article belongs to the Special Issue Biomedical Applications of Graphene-Based Nanomaterials)
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12 pages, 2782 KiB  
Article
Beam Theory of Thermal–Electro-Mechanical Coupling for Single-Wall Carbon Nanotubes
by Kun Huang and Ji Yao
Nanomaterials 2021, 11(4), 923; https://doi.org/10.3390/nano11040923 - 5 Apr 2021
Cited by 13 | Viewed by 1876
Abstract
The potential application field of single-walled carbon nanotubes (SWCNTs) is immense, due to their remarkable mechanical and electrical properties. However, their mechanical properties under combined physical fields have not attracted researchers’ attention. For the first time, the present paper proposes beam theory to [...] Read more.
The potential application field of single-walled carbon nanotubes (SWCNTs) is immense, due to their remarkable mechanical and electrical properties. However, their mechanical properties under combined physical fields have not attracted researchers’ attention. For the first time, the present paper proposes beam theory to model SWCNTs’ mechanical properties under combined temperature and electrostatic fields. Unlike the classical Bernoulli–Euler beam model, this new model has independent extensional stiffness and bending stiffness. Static bending, buckling, and nonlinear vibrations are investigated through the classical beam model and the new model. The results show that the classical beam model significantly underestimates the influence of temperature and electrostatic fields on the mechanical properties of SWCNTs because the model overestimates the bending stiffness. The results also suggest that it may be necessary to re-examine the accuracy of the classical beam model of SWCNTs. Full article
(This article belongs to the Section 2D and Carbon Nanomaterials)
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12 pages, 3065 KiB  
Article
Enzymatic Preparation and Characterization of Spherical Microparticles Composed of Artificial Lignin and TEMPO-Oxidized Cellulose Nanofiber
by Naoya Fukuda, Mayumi Hatakeyama and Takuya Kitaoka
Nanomaterials 2021, 11(4), 917; https://doi.org/10.3390/nano11040917 - 3 Apr 2021
Cited by 10 | Viewed by 4247
Abstract
A one-pot and one-step enzymatic synthesis of submicron-order spherical microparticles composed of dehydrogenative polymers (DHPs) of coniferyl alcohol as a typical lignin precursor and TEMPO-oxidized cellulose nanofibers (TOCNFs) was investigated. Horseradish peroxidase enzymatically catalyzed the radical coupling of coniferyl alcohol in an aqueous [...] Read more.
A one-pot and one-step enzymatic synthesis of submicron-order spherical microparticles composed of dehydrogenative polymers (DHPs) of coniferyl alcohol as a typical lignin precursor and TEMPO-oxidized cellulose nanofibers (TOCNFs) was investigated. Horseradish peroxidase enzymatically catalyzed the radical coupling of coniferyl alcohol in an aqueous suspension of TOCNFs, resulting in the formation of spherical microparticles with a diameter and sphericity index of approximately 0.8 μm and 0.95, respectively. The ζ-potential of TOCNF-functionalized DHP microspheres was about −40 mV, indicating that the colloidal systems had good stability. Nanofibrous components were clearly observed on the microparticle surface by scanning electron microscopy, while some TOCNFs were confirmed to be inside the microparticles by confocal laser scanning microscopy with Calcofluor white staining. As both cellulose and lignin are natural polymers known to biodegrade, even in the sea, these woody TOCNF−DHP microparticle nanocomposites were expected to be promising alternatives to fossil resource-derived microbeads in cosmetic applications. Full article
(This article belongs to the Special Issue Emerging Functions of Nano-Organized Polysaccharides)
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13 pages, 6213 KiB  
Article
The Influence of Scandium on the Composition and Structure of the Ti-Al Alloy Obtained by “Hydride Technology”
by Natalia Karakchieva, Olga Lepakova, Yuri Abzaev, Victor Sachkov and Irina Kurzina
Nanomaterials 2021, 11(4), 918; https://doi.org/10.3390/nano11040918 - 3 Apr 2021
Cited by 6 | Viewed by 2887
Abstract
In this study the influence of scandium on the structural and phase state of the Ti-Al alloy obtained by the method of “Hydride Technology” (HT). The Rietveld method has allowed for determining the content of basic phases of the 49at.%Ti-49at.%Al-2at.%Sc system. By means [...] Read more.
In this study the influence of scandium on the structural and phase state of the Ti-Al alloy obtained by the method of “Hydride Technology” (HT). The Rietveld method has allowed for determining the content of basic phases of the 49at.%Ti-49at.%Al-2at.%Sc system. By means of the methods of transmission electron microscopy (TEM) and X-ray spectral microanalysis, it has been established that scandium additives into the Ti-Al system result in the change of the quantitative content of phases in local regions of the structure. The Ti2Al5 phase has been found, and Ti2Al has been absent. In the morphology of substructures Ti-Al and Ti-Al-Sc there are lamellar structures or lamellae; the peculiarities of the distribution, fraction and size of which are influenced by scandium additives. The average width of Al-rich lamellae has been 0.85 µm, which is four times greater than that for the Ti-Al system (0.21 µm). For Ti-rich lamellae of the sample of the Ti-Al-Sc alloy, the average width of the lamellae has been 0.54 µm, and for Ti-Al it has been 0.34 µm. Based on the obtained data, a scheme of the distribution of phases in the composition of the Ti-Al-Sc alloy in the lamellar structures has been proposed. It has been established that in the Ti-Al-Sc system there is growth of the near-surface strength relative to Ti-Al. In this way, the microhardness of the Ti-Al-Sc alloy has amounted to 1.7 GPa, that is of the Ti-Al alloy which is 1.2 GPa. Full article
(This article belongs to the Special Issue Synthesis, Properties and Applications of Metal-Based Nanomaterials)
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16 pages, 3315 KiB  
Article
Hygro-Thermal Vibrations of Porous FG Nano-Beams Based on Local/Nonlocal Stress Gradient Theory of Elasticity
by Rosa Penna, Luciano Feo, Giuseppe Lovisi and Francesco Fabbrocino
Nanomaterials 2021, 11(4), 910; https://doi.org/10.3390/nano11040910 - 2 Apr 2021
Cited by 24 | Viewed by 2568
Abstract
In this manuscript the dynamic response of porous functionally-graded (FG) Bernoulli–Euler nano-beams subjected to hygro-thermal environments is investigated by the local/nonlocal stress gradient theory of elasticity. In particular, the influence of several parameters on both the thermo-elastic material properties and the structural response [...] Read more.
In this manuscript the dynamic response of porous functionally-graded (FG) Bernoulli–Euler nano-beams subjected to hygro-thermal environments is investigated by the local/nonlocal stress gradient theory of elasticity. In particular, the influence of several parameters on both the thermo-elastic material properties and the structural response of the FG nano-beams, such as material gradient index, porosity volume fraction, nonlocal parameter, gradient length parameter, and mixture parameter is examined. It is shown how the proposed approach is able to capture the dynamic behavior of porous functionally graded Bernoulli–Euler nano-beams under hygro-thermal loads and leads to well-posed structural problems of nano-mechanics. Full article
(This article belongs to the Special Issue Mechanics of Micro and Nano Structures and Materials)
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13 pages, 1731 KiB  
Article
Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets
by Alina Daniela Crisan, Aurel Leca, Cristina Bartha, Ioan Dan and Ovidiu Crisan
Nanomaterials 2021, 11(4), 896; https://doi.org/10.3390/nano11040896 - 31 Mar 2021
Cited by 4 | Viewed by 2656
Abstract
Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic [...] Read more.
Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic parameters and to illustrate the viability of these alloys as the next generation of rare earth (RE)-free magnets. By differential scanning calorimetry (DSC), activation energies and temperatures of onset of the ε-τ phase transformation were obtained. Structural analysis was performed using X-ray diffraction (XRD) and the resulting XRD patterns were quantitatively assessed using full profile Rietveld-type analysis. Appropriate annealing was performed in order to enable the ε-τ phase transformation. While hcp ε-phase was found to be predominant in the as-cast samples, after appropriate annealing, the tetragonal τ-phase, the one that furnishes the relevant magnetic response, was found to be predominant with an abundance of about 90%. The data suggested a mechanism of hcp ε-phase decomposition controlled by the segregation towards the interfacial regions, having the rate of transformation governed by antiphase boundary diffusion processes. Magnetic measurements of annealed sample Mn53Al45C2, consisting of predominant tetragonal τ-phase, showed high values of magnetization and increased coercivity, consistent with an energy product of about 10 MGOe, similar with previously reported magnetization measurements, providing further insight into the realization of future class of RE-free low-cost permanent magnets. Full article
(This article belongs to the Special Issue Preparation and Characterization of Nanomaterials with Multifunctional Properties)
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16 pages, 4640 KiB  
Article
Profiling of Sub-Lethal in Vitro Effects of Multi-Walled Carbon Nanotubes Reveals Changes in Chemokines and Chemokine Receptors
by Sandeep Keshavan, Fernando Torres Andón, Audrey Gallud, Wei Chen, Knut Reinert, Lang Tran and Bengt Fadeel
Nanomaterials 2021, 11(4), 883; https://doi.org/10.3390/nano11040883 - 30 Mar 2021
Cited by 9 | Viewed by 3011
Abstract
Engineered nanomaterials are potentially very useful for a variety of applications, but studies are needed to ascertain whether these materials pose a risk to human health. Here, we studied three benchmark nanomaterials (Ag nanoparticles, TiO2 nanoparticles, and multi-walled carbon nanotubes, MWCNTs) procured [...] Read more.
Engineered nanomaterials are potentially very useful for a variety of applications, but studies are needed to ascertain whether these materials pose a risk to human health. Here, we studied three benchmark nanomaterials (Ag nanoparticles, TiO2 nanoparticles, and multi-walled carbon nanotubes, MWCNTs) procured from the nanomaterial repository at the Joint Research Centre of the European Commission. Having established a sub-lethal concentration of these materials using two human cell lines representative of the immune system and the lungs, respectively, we performed RNA sequencing of the macrophage-like cell line after exposure for 6, 12, and 24 h. Downstream analysis of the transcriptomics data revealed significant effects on chemokine signaling pathways. CCR2 was identified as the most significantly upregulated gene in MWCNT-exposed cells. Using multiplex assays to evaluate cytokine and chemokine secretion, we could show significant effects of MWCNTs on several chemokines, including CCL2, a ligand of CCR2. The results demonstrate the importance of evaluating sub-lethal concentrations of nanomaterials in relevant target cells. Full article
(This article belongs to the Special Issue Nanoparticle-Macrophage Interactions: Implications for Nanosafety and Nanomedicine)
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26 pages, 10830 KiB  
Article
Obtaining and Properties of a Photocatalytic Composite Material of the “SiO2–TiO2” System Based on Various Types of Silica Raw Materials
by Valeria Strokova, Ekaterina Gubareva, Yulia Ogurtsova, Roman Fediuk, Piqi Zhao, Nikolai Vatin and Yuriy Vasilev
Nanomaterials 2021, 11(4), 866; https://doi.org/10.3390/nano11040866 - 29 Mar 2021
Cited by 12 | Viewed by 2797
Abstract
Compositions and technology for obtaining a photocatalytic composite material (PCM) by deposition of titanium dioxide particles synthesized by the sol–gel method on a silica support of various types (microsilica, gaize and diatomite) have been developed. The properties (chemical and mineral composition, dispersion, specific [...] Read more.
Compositions and technology for obtaining a photocatalytic composite material (PCM) by deposition of titanium dioxide particles synthesized by the sol–gel method on a silica support of various types (microsilica, gaize and diatomite) have been developed. The properties (chemical and mineral composition, dispersion, specific surface area, porosity, ζ-potential, acid–base properties, and microstructure) of microsilica, gaize and diatomite were studied to assess the effectiveness of using a photocatalytic agent as a carrier. In terms of specific viscosity (ηsp = 45), the concentration of the precursor (tetrabutoxytitanium—TBT) is set at 22 vol. % in a solvent (ethanol), at which it is possible to obtain the maximum amount of dissolved film oligomer without the formation of an aggregate-like precipitate. Modification of the reaction mixture (precursor: ethanol = 1:3) by replacing part of the solvent with a Span-60 surfactant/TBT = 1–1.1 made it possible to obtain polydisperse titanium dioxide particles with peak sizes of 43 nm and 690 nm according to laser granulometry data. Taking into account the interaction of titanium complexes with the surface of a silica support, a phenomenological model of the processes of structure formation of a photocatalytic composite material is proposed. By the value of the decomposition of rhodamine B, the photocatalytic activity of the developed composite materials was determined: PCM based on diatomite—86%; PCM based on microsilica—85%; PCM based on gaize—57%. Full article
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17 pages, 10631 KiB  
Article
Influence of Colloidal Au on the Growth of ZnO Nanostructures
by Frank Güell, Andreu Cabot, Sergi Claramunt, Ahmad Ostovari Moghaddam and Paulina R. Martínez-Alanis
Nanomaterials 2021, 11(4), 870; https://doi.org/10.3390/nano11040870 - 29 Mar 2021
Cited by 13 | Viewed by 2769
Abstract
Vapor-liquid-solid processes allow growing high-quality nanowires from a catalyst. An alternative to the conventional use of catalyst thin films, colloidal nanoparticles offer advantages not only in terms of cost, but also in terms of controlling the location, size, density, and morphology of the [...] Read more.
Vapor-liquid-solid processes allow growing high-quality nanowires from a catalyst. An alternative to the conventional use of catalyst thin films, colloidal nanoparticles offer advantages not only in terms of cost, but also in terms of controlling the location, size, density, and morphology of the grown nanowires. In this work, we report on the influence of different parameters of a colloidal Au nanoparticle suspension on the catalyst-assisted growth of ZnO nanostructures by a vapor-transport method. Modifying colloid parameters such as solvent and concentration, and growth parameters such as temperature, pressure, and Ar gas flow, ZnO nanowires, nanosheets, nanotubes and branched-nanowires can be grown over silica on silicon and alumina substrates. High-resolution transmission electron microscopy reveals the high-crystal quality of the ZnO nanostructures obtained. The photoluminescence results show a predominant emission in the ultraviolet range corresponding to the exciton peak, and a very broad emission band in the visible range related to different defect recombination processes. The growth parameters and mechanisms that control the shape of the ZnO nanostructures are here analyzed and discussed. The ZnO-branched nanowires were grown spontaneously through catalyst migration. Furthermore, the substrate is shown to play a significant role in determining the diameters of the ZnO nanowires by affecting the surface mobility of the metal nanoparticles. Full article
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13 pages, 1740 KiB  
Article
Loading of Beclomethasone in Liposomes and Hyalurosomes Improved with Mucin as Effective Approach to Counteract the Oxidative Stress Generated by Cigarette Smoke Extract
by Maria Letizia Manca, Maria Ferraro, Elisabetta Pace, Serena Di Vincenzo, Donatella Valenti, Xavier Fernàndez-Busquets, Catalina Anisoara Peptu and Maria Manconi
Nanomaterials 2021, 11(4), 850; https://doi.org/10.3390/nano11040850 - 26 Mar 2021
Cited by 11 | Viewed by 2835
Abstract
In this work beclomethasone dipropionate was loaded into liposomes and hyalurosomes modified with mucin to improve the ability of the payload to counteract the oxidative stress and involved damages caused by cigarette smoke in the airway. The vesicles were prepared by dispersing all [...] Read more.
In this work beclomethasone dipropionate was loaded into liposomes and hyalurosomes modified with mucin to improve the ability of the payload to counteract the oxidative stress and involved damages caused by cigarette smoke in the airway. The vesicles were prepared by dispersing all components in the appropriate vehicle and sonicating them, thus avoiding the use of organic solvents. Unilamellar and bilamellar vesicles small in size (~117 nm), homogeneously dispersed (polydispersity index lower than 0.22) and negatively charged (~−11 mV), were obtained. Moreover, these vesicle dispersions were stable for five months at room temperature (~25 °C). In vitro studies performed using the Next Generation Impactor confirmed the suitability of the formulations to be nebulized as they were capable of reaching the last stages of the impactor that mimic the deeper airways, thus improving the deposition of beclomethasone in the target site. Further, biocompatibility studies performed by using 16HBE bronchial epithelial cells confirmed the high biocompatibility and safety of all the vesicles. Among the tested formulations, only mucin-hyalurosomes were capable of effectively counteracting the production of reactive oxygen species (ROS) induced by cigarette smoke extract, suggesting that this formulation may represent a promising tool to reduce the damaging effects of cigarette smoke in the lung tissues, thus reducing the pathogenesis of cigarette smoke-associated diseases such as chronic obstructive pulmonary disease, emphysema, and cancer. Full article
(This article belongs to the Special Issue Nanocarriers and Targeted Drug Delivery)
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13 pages, 4610 KiB  
Article
Organic-to-Aqueous Phase Transfer of Alloyed AgInS2-ZnS Nanocrystals Using Simple Hydrophilic Ligands: Comparison of 11-Mercaptoundecanoic Acid, Dihydrolipoic Acid and Cysteine
by Patrycja Kowalik, Piotr Bujak, Mateusz Penkala and Adam Pron
Nanomaterials 2021, 11(4), 843; https://doi.org/10.3390/nano11040843 - 25 Mar 2021
Cited by 8 | Viewed by 3557
Abstract
The exchange of primary hydrophobic ligands for hydrophilic ones was studied for two types of alloyed AgInS2-ZnS nanocrystals differing in composition and by consequence exhibiting two different emission colors: red (R) and green (G). Three simple hydrophilic ligands were tested, namely, [...] Read more.
The exchange of primary hydrophobic ligands for hydrophilic ones was studied for two types of alloyed AgInS2-ZnS nanocrystals differing in composition and by consequence exhibiting two different emission colors: red (R) and green (G). Three simple hydrophilic ligands were tested, namely, 11-mercaptoundecanoic acid, dihydrolipoic acid and cysteine. In all cases, stable aqueous colloidal dispersions were obtained. Detailed characterization of the nanocrystal surface before and after the ligand exchange by NMR spectroscopy unequivocally showed that the exchange process was the most efficient in the case of dihydrolipoic acid, leading to the complete removal of the primary ligands with a relatively small photoluminescence quantum yield drop from 68% to 40% for nanocrystals of the R type and from 48% to 28% for the G ones. Full article
(This article belongs to the Special Issue Nanocrystals: Synthesis, Properties and Applications)
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13 pages, 14251 KiB  
Article
Self-Sensing Nanocomposites for Structural Applications: Choice Criteria
by Liberata Guadagno, Patrizia Lamberti, Vincenzo Tucci and Luigi Vertuccio
Nanomaterials 2021, 11(4), 833; https://doi.org/10.3390/nano11040833 - 24 Mar 2021
Cited by 11 | Viewed by 2369
Abstract
Epoxy resins containing multi-wall carbon nanotubes (MWCNTs) have proven to be suitable for manufacturing promising self-sensing materials to be applied in the automotive and aeronautic sectors. Different parameters concerning morphological and mechanical properties of the hosting matrices have been analyzed to choose the [...] Read more.
Epoxy resins containing multi-wall carbon nanotubes (MWCNTs) have proven to be suitable for manufacturing promising self-sensing materials to be applied in the automotive and aeronautic sectors. Different parameters concerning morphological and mechanical properties of the hosting matrices have been analyzed to choose the most suitable system for targeted applications. Two different epoxy precursors, the tetrafunctional tetraglycidyl methylene dianiline (TGMDA) and the bifunctional bisphenol A diglycidyl ether (DGEBA) have been considered. Both precursors have been hardened using the same hardener in stoichiometric conditions. The different functionality of the precursor strongly affects the crosslinking density and, as a direct consequence, the electrical and mechanical behavior. The properties exhibited by the two different formulations can be taken into account in order to make the most appropriate choice with respect to the sensing performance. For practical applications, the choice of one formulation rather than another can be performed on the basis of costs, sensitivity, processing conditions, and most of all, mechanical requirements and in-service conditions of the final product. The performed characterization shows that the nanocomposite based on the TGMDA precursor manifests better performance in applications where high values in the glass transition temperature and storage modulus are required. Full article
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19 pages, 13452 KiB  
Article
Hybrid Nanostructures Obtained by Transport and Condensation of Tungsten Oxide Vapours onto CNW Templates
by Lavinia Gabriela Carpen, Tomy Acsente, Veronica Sătulu, Elena Matei, Sorin Vizireanu, Bogdan Ionuț Biță and Gheorghe Dinescu
Nanomaterials 2021, 11(4), 835; https://doi.org/10.3390/nano11040835 - 24 Mar 2021
Cited by 12 | Viewed by 3174
Abstract
We present hybrid nanomaterial architectures, consisting of carbon nanowalls (CNW) templates decorated with tungsten oxide nanoparticles, synthesized using a mechanism based on tungsten oxide sublimation, vapor transport, followed by vapor condensation, in the absence or presence of plasma. The key steps in the [...] Read more.
We present hybrid nanomaterial architectures, consisting of carbon nanowalls (CNW) templates decorated with tungsten oxide nanoparticles, synthesized using a mechanism based on tungsten oxide sublimation, vapor transport, followed by vapor condensation, in the absence or presence of plasma. The key steps in the decoration mechanism are the sublimation of tungsten oxides, when are exposed in vacuum at high temperature (800 °C), and their redeposition on colder surfaces (400–600 °C). The morphology and chemical composition of the hybrid architectures, as obtained from Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy, are discussed with respect to substrate nature and the physical conditions of synthesis. We pointed out that the decoration process is strongly dependent on the temperature of the CNW templates and plasma presence. Thus, the decoration process performed with plasma was effective for a wider range of template temperatures, in contrast with the decoration process performed without plasma. The results are useful for applications using the sensing and photochemical properties of tungsten oxides, and have also relevance for fusion technology, tungsten walls erosion and material redeposition being widely observed in fusion machines. Full article
(This article belongs to the Special Issue Plasma Based Nanomaterials and Their Applications)
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