Nanomaterials

12 pages, 1873 KiB

Open AccessEditor’s ChoiceArticle

Nanostructured Hybrid Metal Mesh as Transparent Conducting Electrodes: Selection Criteria Verification in Perovskite Solar Cells

by John Mohanraj, Chetan R. Singh, Tanaji P. Gujar, C. David Heinrich and Mukundan Thelakkat

Nanomaterials 2021, 11(7), 1783; https://doi.org/10.3390/nano11071783 - 9 Jul 2021

Cited by 6 | Viewed by 3977

Abstract

Nanostructured metal mesh structures demonstrating excellent conductivity and high transparency are one of the promising transparent conducting electrode (TCE) alternatives for indium tin oxide (ITO). Often, these metal nanostructures are to be employed as hybrids along with a conducting filler layer to collect [...] Read more.

Nanostructured metal mesh structures demonstrating excellent conductivity and high transparency are one of the promising transparent conducting electrode (TCE) alternatives for indium tin oxide (ITO). Often, these metal nanostructures are to be employed as hybrids along with a conducting filler layer to collect charge carriers from the network voids and to minimize current and voltage losses. The influence of filler layers on dictating the extent of such ohmic loss is complex. Here, we used a general numerical model to correlate the sheet resistance of the filler, lateral charge transport distance in network voids, metal mesh line width and ohmic losses in optoelectronic devices. To verify this correlation, we prepared gold or copper network electrodes with different line widths and different filler layers, and applied them as TCEs in perovskite solar cells. We show that the photovoltaic parameters scale with the hybrid metal network TCE properties and an Au-network or Cu-network with aluminum-doped zinc oxide (AZO) filler can replace ITO very well, validating our theoretical predictions. Thus, the proposed model could be employed to select an appropriate filler layer for a specific metal mesh electrode geometry and dimensions to overcome the possible ohmic losses in optoelectronic devices. Full article

(This article belongs to the Special Issue Nanomaterial Electrodes)

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34 pages, 2073 KiB

Open AccessEditor’s ChoiceReview

Zebrafish Models for the Safety and Therapeutic Testing of Nanoparticles with a Focus on Macrophages

by Alba Pensado-López, Juan Fernández-Rey, Pedro Reimunde, José Crecente-Campo, Laura Sánchez and Fernando Torres Andón

Nanomaterials 2021, 11(7), 1784; https://doi.org/10.3390/nano11071784 - 9 Jul 2021

Cited by 27 | Viewed by 8494

Abstract

New nanoparticles and biomaterials are increasingly being used in biomedical research for drug delivery, diagnostic applications, or vaccines, and they are also present in numerous commercial products, in the environment and workplaces. Thus, the evaluation of the safety and possible therapeutic application of [...] Read more.

New nanoparticles and biomaterials are increasingly being used in biomedical research for drug delivery, diagnostic applications, or vaccines, and they are also present in numerous commercial products, in the environment and workplaces. Thus, the evaluation of the safety and possible therapeutic application of these nanomaterials has become of foremost importance for the proper progress of nanotechnology. Due to economical and ethical issues, in vitro and in vivo methods are encouraged for the testing of new compounds and/or nanoparticles, however in vivo models are still needed. In this scenario, zebrafish (Danio rerio) has demonstrated potential for toxicological and pharmacological screenings. Zebrafish presents an innate immune system, from early developmental stages, with conserved macrophage phenotypes and functions with respect to humans. This fact, combined with the transparency of zebrafish, the availability of models with fluorescently labelled macrophages, as well as a broad variety of disease models offers great possibilities for the testing of new nanoparticles. Thus, with a particular focus on macrophage–nanoparticle interaction in vivo, here, we review the studies using zebrafish for toxicological and biodistribution testing of nanoparticles, and also the possibilities for their preclinical evaluation in various diseases, including cancer and autoimmune, neuroinflammatory, and infectious diseases. Full article

(This article belongs to the Special Issue Nanoparticle-Macrophage Interactions: Implications for Nanosafety and Nanomedicine)

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19 pages, 5977 KiB

Open AccessEditor’s ChoiceArticle

Study on the Effect of Nanoparticle Used in Nano-Fluid Flooding on Droplet–Interface Electro-Coalescence

by Donghai Yang, Huayao Sun, Qing Chang, Yongxiang Sun and Limin He

Nanomaterials 2021, 11(7), 1764; https://doi.org/10.3390/nano11071764 - 6 Jul 2021

Cited by 10 | Viewed by 2620

Abstract

Nano-fluid flooding is a new method capable of improving oil recovery; however, nanoparticles (NPs) significantly affect electric dehydration, which has rarely been investigated. The effect of silica (SiO₂) NPs on the droplet–interface coalescence was investigated using a high-speed digital camera under [...] Read more.

Nano-fluid flooding is a new method capable of improving oil recovery; however, nanoparticles (NPs) significantly affect electric dehydration, which has rarely been investigated. The effect of silica (SiO₂) NPs on the droplet–interface coalescence was investigated using a high-speed digital camera under an electric field. The droplet experienced a fall, coalescence, and secondary droplet formation. The results revealed that the oil–water interfacial tension and water conductivity changed because of the SiO₂ NPs. The decrease of interfacial tension facilitated droplet deformation during the falling process. However, with the increase of particle concentration, the formed particle film inhibited the droplet deformation degree. Droplet and interface are connected by a liquid bridge during coalescence, and the NP concentration also resulted in the shape of this liquid bridge changing. The increase of NP concentration inhibited the horizontal contraction of the liquid bridge while promoting vertical collapse. As a result, it did not facilitate secondary droplet formation. Moreover, the droplet falling velocity decreased, while the rising velocity of the secondary droplet increased. Additionally, the inverse calculation of the force balance equation showed that the charge of the secondary droplet also increased. This is attributed to nanoparticle accumulation, which resulted in charge accumulation on the top of the droplet. Full article

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15 pages, 1814 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Water Filtration Membranes Based on Non-Woven Cellulose Fabrics: Effect of Nanopolysaccharide Coatings on Selective Particle Rejection, Antifouling, and Antibacterial Properties

by Blanca Jalvo, Andrea Aguilar-Sanchez, Maria-Ximena Ruiz-Caldas and Aji P. Mathew

Nanomaterials 2021, 11(7), 1752; https://doi.org/10.3390/nano11071752 - 5 Jul 2021

Cited by 31 | Viewed by 6965

Abstract

This article presents a comparative study of the surface characteristics and water purification performance of commercially available cellulose nonwoven fabrics modified, via cast coating, with different nano-dimensioned bio-based carbohydrate polymers, viz. cellulose nanocrystals (CNC), TEMPO-oxidized cellulose nanofibers (T-CNF), and chitin nanocrystals (ChNC). The [...] Read more.

This article presents a comparative study of the surface characteristics and water purification performance of commercially available cellulose nonwoven fabrics modified, via cast coating, with different nano-dimensioned bio-based carbohydrate polymers, viz. cellulose nanocrystals (CNC), TEMPO-oxidized cellulose nanofibers (T-CNF), and chitin nanocrystals (ChNC). The surface-modified nonwoven fabrics showed an improvement in wettability, surface charge modification, and a slight decrease of maximum pore size. The modification improved the water permeance in most of the cases, enhanced the particle separation performance in a wide range of sizes, upgraded the mechanical properties in dry conditions, and showed abiotic antifouling capability against proteins. In addition, T-CNF and ChNC coatings proved to be harmful to the bacteria colonizing on the membranes. This simple surface impregnation approach based on green nanotechnology resulted in highly efficient and fully bio-based high-flux water filtration membranes based on commercially available nonwoven fabrics, with distinct performance for particle rejection, antifouling and antibacterial properties. Full article

(This article belongs to the Special Issue Antibacterial Nanomaterials Coating: Fabrication and Applications)

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8 pages, 1428 KiB

Open AccessEditor’s ChoiceArticle

Gold Nanoparticle DNA Damage by Photon Beam in a Magnetic Field: A Monte Carlo Study

by Mehwish Jabeen and James C. L. Chow

Nanomaterials 2021, 11(7), 1751; https://doi.org/10.3390/nano11071751 - 3 Jul 2021

Cited by 23 | Viewed by 3749

Abstract

Ever since the emergence of magnetic resonance (MR)-guided radiotherapy, it is important to investigate the impact of the magnetic field on the dose enhancement in deoxyribonucleic acid (DNA), when gold nanoparticles are used as radiosensitizers during radiotherapy. Gold nanoparticle-enhanced radiotherapy is known to [...] Read more.

Ever since the emergence of magnetic resonance (MR)-guided radiotherapy, it is important to investigate the impact of the magnetic field on the dose enhancement in deoxyribonucleic acid (DNA), when gold nanoparticles are used as radiosensitizers during radiotherapy. Gold nanoparticle-enhanced radiotherapy is known to enhance the dose deposition in the DNA, resulting in a double-strand break. In this study, the effects of the magnetic field on the dose enhancement factor (DER) for varying gold nanoparticle sizes, photon beam energies and magnetic field strengths and orientations were investigated using Geant4-DNA Monte Carlo simulations. Using a Monte Carlo model including a single gold nanoparticle with a photon beam source and DNA molecule on the left and right, it is demonstrated that as the gold nanoparticle size increased, the DER increased. However, as the photon beam energy decreased, an increase in the DER was detected. When a magnetic field was added to the simulation model, the DER was found to increase by 2.5–5% as different field strengths (0–2 T) and orientations (x-, y- and z-axis) were used for a 100 nm gold nanoparticle using a 50 keV photon beam. The DNA damage reflected by the DER increased slightly with the presence of the magnetic field. However, variations in the magnetic field strength and orientation did not change the DER significantly. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Biomedical Imaging and Cancer Therapy)

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17 pages, 4042 KiB

Open AccessEditor’s ChoiceArticle

A Novel Approach to the Facile Growth and Organization of Photothermal Prussian Blue Nanocrystals on Different Surfaces

by Giang Ngo, Gautier Félix, Christophe Dorandeu, Jean-Marie Devoisselle, Luca Costa, Pierre-Emmanuel Milhiet, Yannick Guari, Joulia Larionova and Joël Chopineau

Nanomaterials 2021, 11(7), 1749; https://doi.org/10.3390/nano11071749 - 2 Jul 2021

Cited by 4 | Viewed by 3119

Abstract

We report here a novel “one-pot” approach for the controlled growth and organization of Prussian blue nanostructures on three different surfaces: pure Au⁰, cysteamine-functionalized Au⁰, and SiO₂-supported lipid bilayers with different natures of lipids. We demonstrate that [...] Read more.

We report here a novel “one-pot” approach for the controlled growth and organization of Prussian blue nanostructures on three different surfaces: pure Au⁰, cysteamine-functionalized Au⁰, and SiO₂-supported lipid bilayers with different natures of lipids. We demonstrate that fine control over the size, morphology, and the degree and homogeneity of the surface coverage by Prussian Blue (PB) nanostructures may be achieved by manipulating different parameters, which are the precursor concentration, the nature of the functional groups or the nature of lipids on the surfaces. This allows the growth of isolated PB nanopyramids and nanocubes or the design of thin dense films over centimeter square surfaces. The formation of unusual Prussian blue nanopyramids is discussed. Finally, we demonstrate, by using experimental techniques and theoretical modeling, that PB nanoparticles deposited on the gold surface exhibit strong photothermal properties, permitting a rapid temperature increase up to 90 °C with a conversion of the laser power of almost 50% for power source heat. Full article

(This article belongs to the Special Issue Frontiers in Functional Nanomaterials)

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20 pages, 9084 KiB

Open AccessEditor’s ChoiceArticle

Continuous Long-Term Exposure to Low Concentrations of MWCNTs Induces an Epithelial-Mesenchymal Transition in BEAS-2B Cells

by Hélène Barthel, Christian Darne, Laurent Gaté, Athanase Visvikis and Carole Seidel

Nanomaterials 2021, 11(7), 1742; https://doi.org/10.3390/nano11071742 - 1 Jul 2021

Cited by 6 | Viewed by 3389

Abstract

In the field of nanotechnology, the use of multi-walled carbon nanotubes (MWCNTs) is growing. Pulmonary exposure during their production, use, and handling is raising concerns about their potential adverse health effects. The purpose of this study is to assess how the physical characteristics [...] Read more.

In the field of nanotechnology, the use of multi-walled carbon nanotubes (MWCNTs) is growing. Pulmonary exposure during their production, use, and handling is raising concerns about their potential adverse health effects. The purpose of this study is to assess how the physical characteristics of MWCNTs, such as diameter and/or length, can play a role in cellular toxicity. Our experimental design is based on the treatment of human bronchial epithelial cells (BEAS-2B) for six weeks with low concentrations (0.125–1 µg/cm²) of MWCNTs having opposite characteristics: NM-403 and Mitsui-7. Following treatment with both MWCNTs, we observed an increase in mitotic abnormalities and micronucleus-positive cells. The cytotoxic effect was delayed in cells treated with NM-403 compared to Mitsui-7. After 4–6 weeks of treatment, a clear cellular morphological change from epithelial to fibroblast-like phenotype was noted, together with a change in the cell population composition. BEAS-2B cells underwent a conversion from the epithelial to mesenchymal state as we observed a decrease in the epithelial marker E-cadherin and an increased expression of mesenchymal markers N-cadherin, Vimentin, and Fibronectin. After four weeks of recovery, we showed that the induced epithelial-mesenchymal transition is reversible, and that the degree of reversibility depends on the MWCNT. Full article

(This article belongs to the Special Issue Biological and Toxicological Studies of Nanoparticles)

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15 pages, 3326 KiB

Open AccessEditor’s ChoiceArticle

Effect of Nitrogen Doping on the Crystallization Kinetics of Ge₂Sb₂Te₅

by Minh Anh Luong, Nikolay Cherkashin, Béatrice Pecassou, Chiara Sabbione, Frédéric Mazen and Alain Claverie

Nanomaterials 2021, 11(7), 1729; https://doi.org/10.3390/nano11071729 - 30 Jun 2021

Cited by 19 | Viewed by 3873

Abstract

Among the phase change materials, Ge₂Sb₂Te₅ (GST-225) is the most studied and is already integrated into many devices. N doping is known to significantly improve some key characteristics such as the thermal stability of materials and the resistance [...] Read more.

Among the phase change materials, Ge₂Sb₂Te₅ (GST-225) is the most studied and is already integrated into many devices. N doping is known to significantly improve some key characteristics such as the thermal stability of materials and the resistance drift of devices. However, the origin, at the atomic scale, of these alterations is rather elusive. The most important issue is to understand how N doping affects the crystallization characteristics, mechanisms and kinetics, of GST-225. Here, we report the results of a combination of in situ and ex situ transmission electron microscopy (TEM) investigations carried out on specifically designed samples to evidence the influence of N concentration on the crystallization kinetics and resulting morphology of the alloy. Beyond the known shift of the crystallization temperature and the observation of smaller grains, we show that N renders the crystallization process more “nucleation dominated” and ascribe this characteristic to the increased viscosity of the amorphous state. This increased viscosity is linked to the mechanical rigidity and the reduced diffusivity resulting from the formation of Ge–N bonds in the amorphous phase. During thermal annealing, N hampers the coalescence of the crystalline grains and the cubic to hexagonal transition. Making use of AbStrain, a recently invented TEM-based technique, we evidence that the nanocrystals formed from the crystallization of N-doped amorphous GST-225 are under tension, which suggests that N is inserted in the lattice and explains why it is not found at grain boundaries. Globally, all these results demonstrate that the origin of the effect of N on the crystallization of GST-225 is not attributed to the formation of a secondary phase such as a nitride, but to the ability of N to bind to Ge in the amorphous and crystalline phases and to unbind and rebind with Ge along the diffusion path of this atomic species during annealing. Full article

(This article belongs to the Special Issue Synthesis, Properties and Applications of Germanium Chalcogenides)

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13 pages, 3841 KiB

Open AccessEditor’s ChoiceArticle

Characteristics of Plasma Flow for Microwave Plasma Assisted Aerosol Deposition

by In-Je Kang, Chang-Hyun Cho, Hyonu Chang, Soo-Ouk Jang, Hyun-Jae Park, Dae-Gun Kim, Kyung-Min Lee and Ji-Hun Kim

Nanomaterials 2021, 11(7), 1705; https://doi.org/10.3390/nano11071705 - 29 Jun 2021

Cited by 6 | Viewed by 3416

Abstract

To validate the possibility of the developed microwave plasma source with a novel structure for plasma aerosol deposition, the characteristics of the plasma flow velocity generated from the microwave plasma source were investigated by a Mach probe with pressure variation. Simulation with the [...] Read more.

To validate the possibility of the developed microwave plasma source with a novel structure for plasma aerosol deposition, the characteristics of the plasma flow velocity generated from the microwave plasma source were investigated by a Mach probe with pressure variation. Simulation with the turbulent model was introduced to deduce calibration factor of the Mach probe and to compare experimental measurements for analyses of collisional plasma conditions. The results show calibration factor does not seem to be a constant parameter and highly dependent on the collision parameter. The measured plasma flow velocity, which witnessed fluctuations produced by a shock flow, was between 400 and 700 m/s. The optimized conditions for microwave plasma assisted aerosol deposition were derived by the results obtained from analyses of the parameters of microwave plasma jet. Under the optimized conditions, Y₂O₃ coatings deposited on an aluminum substrate were investigated using scanning electron microscope. The results presented in this study show the microwave plasma assisted aerosol deposition with the developed microwave plasma source is highly feasible for thick films with >50 μm. Full article

(This article belongs to the Special Issue Plasma-Enabled Synthesis of Nanostructured Surfaces and Nanoparticles)

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10 pages, 3172 KiB

Open AccessEditor’s ChoiceArticle

Four-Period Vertically Stacked SiGe/Si Channel FinFET Fabrication and Its Electrical Characteristics

by Yongliang Li, Fei Zhao, Xiaohong Cheng, Haoyan Liu, Ying Zan, Junjie Li, Qingzhu Zhang, Zhenhua Wu, Jun Luo and Wenwu Wang

Nanomaterials 2021, 11(7), 1689; https://doi.org/10.3390/nano11071689 - 28 Jun 2021

Cited by 25 | Viewed by 7806

Abstract

In this paper, to solve the epitaxial thickness limit and the high interface trap density of SiGe channel Fin field effect transistor (FinFET), a four-period vertically stacked SiGe/Si channel FinFET is presented. A high crystal quality of four-period stacked SiGe/Si multilayer epitaxial grown [...] Read more.

In this paper, to solve the epitaxial thickness limit and the high interface trap density of SiGe channel Fin field effect transistor (FinFET), a four-period vertically stacked SiGe/Si channel FinFET is presented. A high crystal quality of four-period stacked SiGe/Si multilayer epitaxial grown with the thickness of each SiGe layer less than 10 nm is realized on a Si substrate without any structural defect impact by optimizing its epitaxial grown process. Meanwhile, the Ge atomic fraction of the SiGe layers is very uniform and its SiGe/Si interfaces are sharp. Then, a vertical profile of the stacked SiGe/Si Fin is achieved with HBr/O₂/He plasma by optimizing its bias voltage and O₂ flow. After the four-period vertically stacked SiGe/Si Fin structure is introduced, its FinFET device is successfully fabricated under the same fabrication process as the conventional SiGe FinFET. And it attains better drive current I_on, subthreshold slope (SS) and I_on/I_off ratio electrical performance compared with the conventional SiGe channel FinFET, whose Fin height of SiGe channel is almost equal to total thickness of SiGe in the four-period stacked SiGe/Si channel FinFET. This may be attributed to that the four-period stacked SiGe/Si Fin structure has larger effective channel width (W_eff) and may maintain a better quality and surface interfacial performance during the whole fabrication process. Moreover, Si channel of the stacked SiGe/Si channel turning on first also may have contribution to its better electrical properties. This four-period vertically stacked SiGe/Si channel FinFET device has been demonstrated to be a practical candidate for the future technology nodes. Full article

(This article belongs to the Special Issue Silicon Nanodevices)

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22 pages, 3920 KiB

Open AccessEditor’s ChoiceArticle

Impact of Nanocomposite Combustion Aerosols on A549 Cells and a 3D Airway Model

by Matthias Hufnagel, Nadine May, Johanna Wall, Nadja Wingert, Manuel Garcia-Käufer, Ali Arif, Christof Hübner, Markus Berger, Sonja Mülhopt, Werner Baumann, Frederik Weis, Tobias Krebs, Wolfgang Becker, Richard Gminski, Dieter Stapf and Andrea Hartwig

Nanomaterials 2021, 11(7), 1685; https://doi.org/10.3390/nano11071685 - 27 Jun 2021

Cited by 14 | Viewed by 4090

Abstract

The use of nanomaterials incorporated into plastic products is increasing steadily. By using nano-scaled filling materials, thermoplastics, such as polyethylene (PE), take advantage of the unique properties of nanomaterials (NM). The life cycle of these so-called nanocomposites (NC) usually ends with energetic recovery. [...] Read more.

The use of nanomaterials incorporated into plastic products is increasing steadily. By using nano-scaled filling materials, thermoplastics, such as polyethylene (PE), take advantage of the unique properties of nanomaterials (NM). The life cycle of these so-called nanocomposites (NC) usually ends with energetic recovery. However, the toxicity of these aerosols, which may consist of released NM as well as combustion-generated volatile compounds, is not fully understood. Within this study, model nanocomposites consisting of a PE matrix and nano-scaled filling material (TiO₂, CuO, carbon nano tubes (CNT)) were produced and subsequently incinerated using a lab-scale model burner. The combustion-generated aerosols were characterized with regard to particle release as well as compound composition. Subsequently, A549 cells and a reconstituted 3D lung cell culture model (MucilAir™, Epithelix) were exposed for 4 h to the respective aerosols. This approach enabled the parallel application of a complete aerosol, an aerosol under conditions of enhanced particle deposition using high voltage, and a filtered aerosol resulting in the sole gaseous phase. After 20 h post-incubation, cytotoxicity, inflammatory response (IL-8), transcriptional toxicity profiling, and genotoxicity were determined. Only the exposure toward combustion aerosols originated from PE-based materials induced cytotoxicity, genotoxicity, and transcriptional alterations in both cell models. In contrast, an inflammatory response in A549 cells was more evident after exposure toward aerosols of nano-scaled filler combustion, whereas the thermal decomposition of PE-based materials revealed an impaired IL-8 secretion. MucilAir™ tissue showed a pronounced inflammatory response after exposure to either combustion aerosols, except for nanocomposite combustion. In conclusion, this study supports the present knowledge on the release of nanomaterials after incineration of nano-enabled thermoplastics. Since in the case of PE-based combustion aerosols no major differences were evident between exposure to the complete aerosol and to the gaseous phase, adverse cellular effects could be deduced to the volatile organic compounds that are generated during incomplete combustion of NC. Full article

(This article belongs to the Special Issue Biological and Toxicological Studies of Nanoparticles)

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7 pages, 1283 KiB

Open AccessEditor’s ChoiceArticle

Dynamics of Monolayer Growth in Vapor–Liquid–Solid GaAs Nanowires Based on Surface Energy Minimization

by Hadi Hijazi and Vladimir G. Dubrovskii

Nanomaterials 2021, 11(7), 1681; https://doi.org/10.3390/nano11071681 - 26 Jun 2021

Viewed by 2005

Abstract

The vapor–liquid–solid growth of III-V nanowires proceeds via the mononuclear regime, where only one island nucleates in each nanowire monolayer. The expansion of the monolayer is governed by the surface energetics depending on the monolayer size. Here, we study theoretically the role of [...] Read more.

The vapor–liquid–solid growth of III-V nanowires proceeds via the mononuclear regime, where only one island nucleates in each nanowire monolayer. The expansion of the monolayer is governed by the surface energetics depending on the monolayer size. Here, we study theoretically the role of surface energy in determining the monolayer morphology at a given coverage. The optimal monolayer configuration is obtained by minimizing the surface energy at different coverages for a set of energetic constants relevant for GaAs nanowires. In contrast to what has been assumed so far in the growth modeling of III-V nanowires, we find that the monolayer expansion may not be a continuous process. Rather, some portions of the already formed monolayer may dissolve on one of its sides, with simultaneous growth proceeding on the other side. These results are important for fundamental understanding of vapor–liquid–solid growth at the atomic level and have potential impacts on the statistics within the nanowire ensembles, crystal phase, and doping properties of III-V nanowires. Full article

(This article belongs to the Special Issue Preparation and Application of Nanowires)

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17 pages, 7581 KiB

Open AccessEditor’s ChoiceArticle

Porphyrin-Based Supramolecular Flags in the Thermal Gradients’ Wind: What Breaks the Symmetry, How and Why

by Angelo Nicosia, Fabiana Vento, Giovanni Marletta, Grazia M. L. Messina, Cristina Satriano, Valentina Villari, Norberto Micali, Maria Teresa De Martino, Maaike J. G. Schotman and Placido Giuseppe Mineo

Nanomaterials 2021, 11(7), 1673; https://doi.org/10.3390/nano11071673 - 25 Jun 2021

Cited by 9 | Viewed by 3365

Abstract

The Spontaneous Symmetry Breaking (SSB) phenomenon is a natural event in which a system changes its symmetric state, apparently reasonless, in an asymmetrical one. Nevertheless, this occurrence could be hiding unknown inductive forces. An intriguing investigation pathway uses supramolecular aggregates of suitable achiral [...] Read more.

The Spontaneous Symmetry Breaking (SSB) phenomenon is a natural event in which a system changes its symmetric state, apparently reasonless, in an asymmetrical one. Nevertheless, this occurrence could be hiding unknown inductive forces. An intriguing investigation pathway uses supramolecular aggregates of suitable achiral porphyrins, useful to mimic the natural light-harvesting systems (as chlorophyll). Using as SSB probe supramolecular aggregates of 5,10,15,20-tetrakis[p(ω-methoxypolyethyleneoxy)phenyl]porphyrin (StarP), a non-ionic achiral PEGylated porphyrin, we explore here its interaction with weak asymmetric thermal gradients fields. The cross-correlation of the experimental data (circular dichroism, confocal microscopy, atomic force microscopy, and cryo-transmission electron microscopy) revealed that the used building blocks aggregate spontaneously, organizing in flag-like structures whose thermally-induced circular dichroism depends on their features. Finally, thermal gradient-induced enantioselectivity of the supramolecular flag-like aggregates has been shown and linked to their size-dependence mesoscopic deformation, which could be visualized as waving flags in the wind. Full article

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

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14 pages, 2123 KiB

Open AccessEditor’s ChoiceArticle

Combining Augmented Radiotherapy and Immunotherapy through a Nano-Gold and Bacterial Outer-Membrane Vesicle Complex for the Treatment of Glioblastoma

by Mei-Hsiu Chen, Tse-Ying Liu, Yu-Chiao Chen and Ming-Hong Chen

Nanomaterials 2021, 11(7), 1661; https://doi.org/10.3390/nano11071661 - 24 Jun 2021

Cited by 48 | Viewed by 4671

Abstract

Glioblastoma, formerly known as glioblastoma multiforme (GBM), is refractory to existing adjuvant chemotherapy and radiotherapy. We successfully synthesized a complex, Au–OMV, with two specific nanoparticles: gold nanoparticles (AuNPs) and outer-membrane vesicles (OMVs) from E. coli. Au–OMV, when combined with radiotherapy, produced radiosensitizing [...] Read more.

Glioblastoma, formerly known as glioblastoma multiforme (GBM), is refractory to existing adjuvant chemotherapy and radiotherapy. We successfully synthesized a complex, Au–OMV, with two specific nanoparticles: gold nanoparticles (AuNPs) and outer-membrane vesicles (OMVs) from E. coli. Au–OMV, when combined with radiotherapy, produced radiosensitizing and immuno-modulatory effects that successfully suppressed tumor growth in both subcutaneous G261 tumor-bearing and in situ (brain) tumor-bearing C57BL/6 mice. Longer survival was also noted with in situ tumor-bearing mice treated with Au–OMV and radiotherapy. The mechanisms for the successful treatment were evaluated. Intracellular reactive oxygen species (ROS) greatly increased in response to Au–OMV in combination with radiotherapy in G261 glioma cells. Furthermore, with a co-culture of G261 glioma cells and RAW 264.7 macrophages, we found that GL261 cell viability was related to chemotaxis of macrophages and TNF-

α

production. Full article

(This article belongs to the Special Issue Nanomaterials for Drug Delivery and Cancer Therapy)

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12 pages, 24719 KiB

Open AccessEditor’s ChoiceArticle

Growth and Crystallization of SiO₂/GeO₂ Thin Films on Si(100) Substrates

by Jordi Antoja-Lleonart, Václav Ocelík, Silang Zhou, Kit de Hond, Gertjan Koster, Guus Rijnders and Beatriz Noheda

Nanomaterials 2021, 11(7), 1654; https://doi.org/10.3390/nano11071654 - 23 Jun 2021

Cited by 4 | Viewed by 4061

Abstract

The growth of

α

-quartz-based piezoelectric thin films opens the door to higher-frequency electromechanical devices than those available through top-down approaches. We report on the growth of SiO

_{2}

/GeO

_{2}

thin films by pulsed laser deposition and their subsequent crystallization. By introducing [...] Read more.

The growth of

α

-quartz-based piezoelectric thin films opens the door to higher-frequency electromechanical devices than those available through top-down approaches. We report on the growth of SiO

_{2}

/GeO

_{2}

thin films by pulsed laser deposition and their subsequent crystallization. By introducing a devitrifying agent uniformly within the film, we are able to obtain the

α

-quartz phase in the form of platelets with lateral sizes above 100 μm at accessible temperatures. Films containing different amounts of devitrifying agent are investigated, and their crystallinity is ascertained with X-ray diffraction and electron back-scatter diffraction. Our work highlights the difficulty in crystallization when competing phases arise that have markedly different crystalline orientation. Full article

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

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14 pages, 7208 KiB

Open AccessEditor’s ChoiceArticle

Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

by Qiang Zhang, Yohanes Pramudya, Wolfgang Wenzel and Christof Wöll

Nanomaterials 2021, 11(7), 1631; https://doi.org/10.3390/nano11071631 - 22 Jun 2021

Cited by 9 | Viewed by 4818

Abstract

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin [...] Read more.

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations. Full article

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12 pages, 5775 KiB

Open AccessEditor’s ChoiceArticle

Plasmon-Enhanced Antibacterial Activity of Chiral Gold Nanoparticles and In Vivo Therapeutic Effect

by Yuelong Xu, Hongxia Wang, Min Zhang, Jianhao Zhang and Wenjing Yan

Nanomaterials 2021, 11(6), 1621; https://doi.org/10.3390/nano11061621 - 21 Jun 2021

Cited by 21 | Viewed by 4185

Abstract

d-cysteine (d-cys) has been demonstrated to possess an extraordinary antibacterial activity because of its unique steric configuration. However, inefficient antibacterial properties seriously hinder its wide applications. Here, cysteine-functionalized gold nanoparticles (d-/l-Au NPs) were prepared by loading [...] Read more.

d-cysteine (d-cys) has been demonstrated to possess an extraordinary antibacterial activity because of its unique steric configuration. However, inefficient antibacterial properties seriously hinder its wide applications. Here, cysteine-functionalized gold nanoparticles (d-/l-Au NPs) were prepared by loading d-/l-cysteine on the surface of gold nanoparticles for the effective inhibition of Escherichia coli (E. coli) in vitro and in vivo, and the effects on the intestinal microflora in mice were explored during the treatment of E. coli infection in the gut. We found that the antibacterial activity of d-/l-Au NPs was more than 2–3 times higher than pure d-cysteine, l-cysteine and Au NPs. Compared with l-Au NPs, d-Au NPs showed the stronger antibacterial activity, which was related to its unique steric configuration. Chiral Au NPs showed stronger destructive effects on cell membrane compared to other groups, which further leads to the leakage of the cytoplasm and bacterial cell death. The in vivo antibacterial experiment illustrated that d-Au NPs displayed impressive antibacterial activity in the treatment of E. coli-infected mice comparable to kanamycin, whereas they could not affect the balance of intestinal microflora. This work is of great significance in the development of an effective chiral antibacterial agent. Full article

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10 pages, 4999 KiB

Open AccessEditor’s ChoiceArticle

Resolving Site-Specific Energy Levels of Small-Molecule Donor-Acceptor Heterostructures Close to Metal Contacts

by Amani Benhnia, Shinta Watanabe, Rouzhaji Tuerhong, Masato Nakaya, Jun Onoe and Jean-Pierre Bucher

Nanomaterials 2021, 11(6), 1618; https://doi.org/10.3390/nano11061618 - 20 Jun 2021

Cited by 1 | Viewed by 3723

Abstract

The active material of optoelectronic devices must accommodate for contacts which serve to collect or inject the charge carriers. It is the purpose of this work to find out to which extent properties of organic optoelectronic layers change close to metal contacts compared [...] Read more.

The active material of optoelectronic devices must accommodate for contacts which serve to collect or inject the charge carriers. It is the purpose of this work to find out to which extent properties of organic optoelectronic layers change close to metal contacts compared to known properties of bulk materials. Bottom-up fabrication capabilities of model interfaces under ultrahigh vacuum and single-atom low temperature (LT)-STM spectroscopy with density functional theory (DFT) calculations are used to detect the spatial modifications of electronic states such as frontier-orbitals at interfaces. The system under consideration is made of a silver substrate covered with a blend of C₆₀ and ZnPc molecules of a few monolayers. When C₆₀ and ZnPc are separately adsorbed on Ag(111), they show distinct spectroscopic features in STM. However, when C₆₀ is added to the ZnPc monolayer, it shows scanning tunneling spectra similar to ZnPc, revealing a strong interaction of C₆₀ with the ZnPc induced by the substrate. DFT calculations on a model complex confirm the strong hybridization of C₆₀ with ZnPc layer upon adsorption on Ag(111), thus highlighting the role of boundary layers where the donor-acceptor character is strongly perturbed. The calculation also reveals a significant charge transfer from the Ag to the complex that is likely responsible for a downward shift of the molecular LUMO in agreement with the experiment. Full article

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19 pages, 8055 KiB

Open AccessEditor’s ChoiceArticle

Nanoscale Strontium-Substituted Hydroxyapatite Pastes and Gels for Bone Tissue Regeneration

by Caroline J. Harrison, Paul V. Hatton, Piergiorgio Gentile and Cheryl A. Miller

Nanomaterials 2021, 11(6), 1611; https://doi.org/10.3390/nano11061611 - 19 Jun 2021

Cited by 17 | Viewed by 4245

Abstract

Injectable nanoscale hydroxyapatite (nHA) systems are highly promising biomaterials to address clinical needs in bone tissue regeneration, due to their excellent biocompatibility, bioinspired nature, and ability to be delivered in a minimally invasive manner. Bulk strontium-substituted hydroxyapatite (SrHA) is reported to encourage bone [...] Read more.

Injectable nanoscale hydroxyapatite (nHA) systems are highly promising biomaterials to address clinical needs in bone tissue regeneration, due to their excellent biocompatibility, bioinspired nature, and ability to be delivered in a minimally invasive manner. Bulk strontium-substituted hydroxyapatite (SrHA) is reported to encourage bone tissue growth by stimulating bone deposition and reducing bone resorption, but there are no detailed reports describing the preparation of a systematic substitution up to 100% at the nanoscale. The aim of this work was therefore to fabricate systematic series (0–100 atomic% Sr) of SrHA pastes and gels using two different rapid-mixing methodological approaches, wet precipitation and sol-gel. The full range of nanoscale SrHA materials were successfully prepared using both methods, with a measured substitution very close to the calculated amounts. As anticipated, the SrHA samples showed increased radiopacity, a beneficial property to aid in vivo or clinical monitoring of the material in situ over time. For indirect methods, the greatest cell viabilities were observed for the 100% substituted SrHA paste and gel, while direct viability results were most likely influenced by material disaggregation in the tissue culture media. It was concluded that nanoscale SrHAs were superior biomaterials for applications in bone surgery, due to increased radiopacity and improved biocompatibility. Full article

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

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13 pages, 1056 KiB

Open AccessEditor’s ChoiceReview

Nanomaterial Databases: Data Sources for Promoting Design and Risk Assessment of Nanomaterials

by Zuowei Ji, Wenjing Guo, Sugunadevi Sakkiah, Jie Liu, Tucker A. Patterson and Huixiao Hong

Nanomaterials 2021, 11(6), 1599; https://doi.org/10.3390/nano11061599 - 18 Jun 2021

Cited by 35 | Viewed by 7587

Abstract

Nanomaterials have drawn increasing attention due to their tunable and enhanced physicochemical and biological performance compared to their conventional bulk materials. Owing to the rapid expansion of the nano-industry, large amounts of data regarding the synthesis, physicochemical properties, and bioactivities of nanomaterials have [...] Read more.

Nanomaterials have drawn increasing attention due to their tunable and enhanced physicochemical and biological performance compared to their conventional bulk materials. Owing to the rapid expansion of the nano-industry, large amounts of data regarding the synthesis, physicochemical properties, and bioactivities of nanomaterials have been generated. These data are a great asset to the scientific community. However, the data are on diverse aspects of nanomaterials and in different sources and formats. To help utilize these data, various databases on specific information of nanomaterials such as physicochemical characterization, biomedicine, and nano-safety have been developed and made available online. Understanding the structure, function, and available data in these databases is needed for scientists to select appropriate databases and retrieve specific information for research on nanomaterials. However, to our knowledge, there is no study to systematically compare these databases to facilitate their utilization in the field of nanomaterials. Therefore, we reviewed and compared eight widely used databases of nanomaterials, aiming to provide the nanoscience community with valuable information about the specific content and function of these databases. We also discuss the pros and cons of these databases, thus enabling more efficient and convenient utilization. Full article

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

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10 pages, 3211 KiB

Open AccessEditor’s ChoiceArticle

Improved Photoelectrochemical Performance of MoS₂ through Morphology-Controlled Chemical Vapor Deposition Growth on Graphene

by Dong-Bum Seo, Tran Nam Trung, Sung-Su Bae and Eui-Tae Kim

Nanomaterials 2021, 11(6), 1585; https://doi.org/10.3390/nano11061585 - 17 Jun 2021

Cited by 14 | Viewed by 3572

Abstract

The morphology of MoS₂ nanostructures was manipulated from thin films to vertically aligned few-layer nanosheets on graphene, in a controllable and practical manner, using metalorganic chemical vapor deposition. The effects of graphene layer and MoS₂ morphology on photoelectrochemical (PEC) performance were [...] Read more.

The morphology of MoS₂ nanostructures was manipulated from thin films to vertically aligned few-layer nanosheets on graphene, in a controllable and practical manner, using metalorganic chemical vapor deposition. The effects of graphene layer and MoS₂ morphology on photoelectrochemical (PEC) performance were systematically studied on the basis of electronic structure and transitions, carrier dynamic behavior, and PEC measurements. The heterojunction quality of the graphene/vertical few-layer MoS₂ nanosheets was ensured by low-temperature growth at 250−300 °C, resulting in significantly improved charge transfer properties. As a result, the PEC photocurrent density and photoconversion efficiency of the few-layer MoS₂ nanosheets significantly increased upon the insertion of a graphene layer. Among the graphene/MoS₂ samples, the few-layer MoS₂ nanosheet samples exhibited shorter carrier lifetimes and smaller charge transfer resistances than the thin film samples, suggesting that vertically aligned nanosheets provide highly conductive edges as an efficient pathway for photo-generated carriers and have better electronic contact with graphene. In addition, the height of vertical MoS₂ nanosheets on graphene should be controlled within the carrier diffusion length (~200 nm) to achieve the optimal PEC performance. These results can be utilized effectively to exploit the full potential of two-dimensional MoS₂ for various PEC applications. Full article

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

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15 pages, 1893 KiB

Open AccessEditor’s ChoiceArticle

Targeting NF-κB with Nanotherapy in a Mouse Model of Adult T-Cell Leukemia/Lymphoma

by Daniel A. Rauch, John C. Harding, Lee Ratner, Samuel A. Wickline and Hua Pan

Nanomaterials 2021, 11(6), 1582; https://doi.org/10.3390/nano11061582 - 16 Jun 2021

Cited by 8 | Viewed by 4436

Abstract

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive, clonal malignancy of mature T cells caused by human T-cell leukemia virus type 1. Although it is a rare tumor type, it serves as an excellent model of a virus driven process that transforms cells and [...] Read more.

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive, clonal malignancy of mature T cells caused by human T-cell leukemia virus type 1. Although it is a rare tumor type, it serves as an excellent model of a virus driven process that transforms cells and engenders a highly malignant tumor that is extraordinarily difficult to treat. The viral transcriptional transactivator (Tax) in the HTLV-1 genome directly promotes tumorigenesis, and Tax-induced oncogenesis depends on its ability to constitutively activate NF-κB signaling. Accordingly, we developed and evaluated a nano-delivery system that simultaneously inhibits both canonical (p65) and noncanonical (p100) NF-κB signaling pathways locally in tumors after systemic administration. Our results demonstrate that siRNA is delivered rapidly to ATLL tumors after either i.p. or i.v. injection. The siRNA treatment significantly reduced both p65 and p100 mRNA and protein expression. Anti-NF-κB nanotherapy significantly inhibited tumor growth in two distinct tumor models in mice: a spontaneous Tax-driven tumor model, and a Tax tumor cell transplant model. Moreover, siRNA nanotherapy sensitized late-stage ATLL tumors to the conventional chemotherapeutic agent etoposide, indicating a pleiotropic benefit for localized siRNA nanotherapeutics. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Biology and Medicines)

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13 pages, 22215 KiB

Open AccessEditor’s ChoiceArticle

Resveratrol-Loaded Nanoemulsions: In Vitro Activity on Human T24 Bladder Cancer Cells

by Federica Rinaldi, Linda Maurizi, Jacopo Forte, Massimiliano Marazzato, Patrizia Nadia Hanieh, Antonietta Lucia Conte, Maria Grazia Ammendolia, Carlotta Marianecci, Maria Carafa and Catia Longhi

Nanomaterials 2021, 11(6), 1569; https://doi.org/10.3390/nano11061569 - 15 Jun 2021

Cited by 13 | Viewed by 3189

Abstract

The chemopreventive potential of Resveratrol (RV) against bladder cancer and its mechanism of action have been widely demonstrated. The physicochemical properties of RV, particularly its high reactivity and low solubility in aqueous phase, have been limiting factors for its bioavailability and in vivo [...] Read more.

The chemopreventive potential of Resveratrol (RV) against bladder cancer and its mechanism of action have been widely demonstrated. The physicochemical properties of RV, particularly its high reactivity and low solubility in aqueous phase, have been limiting factors for its bioavailability and in vivo efficacy. In order to overcome these limitations, its inclusion in drug delivery systems needs to be taken into account. In particular, oil-in-water (O/W) nanoemulsions (NEs) have been considered ideal candidates for RV encapsulation. Since surfactant and oil composition can strongly influence NE features and their application field, a ternary phase diagram was constructed and evaluated to select a suitable surfactant/oil/water ratio. The selected sample was deeply characterized in terms of physical chemical features, stability, release capability and cytotoxic activity. Results showed a significant decrease in cell viability after the incubation of bladder T24 cancer cells with RV-loaded NEs, compared to free RV. The selected NE formulation was able to preserve and improve RV cytotoxic activity by a more rapid drug uptake into the cells. O/W NEs represent an effective approach to improve RV bioavailability. Full article

(This article belongs to the Special Issue Nanonutraceuticals Delivery)

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9 pages, 3309 KiB

Open AccessEditor’s ChoiceArticle

Extraordinary Optical Transmission by Hybrid Phonon–Plasmon Polaritons Using hBN Embedded in Plasmonic Nanoslits

by Shinpei Ogawa, Shoichiro Fukushima and Masaaki Shimatani

Nanomaterials 2021, 11(6), 1567; https://doi.org/10.3390/nano11061567 - 14 Jun 2021

Cited by 7 | Viewed by 3446

Abstract

Hexagonal boron nitride (hBN) exhibits natural hyperbolic dispersion in the infrared (IR) wavelength spectrum. In particular, the hybridization of its hyperbolic phonon polaritons (HPPs) and surface plasmon resonances (SPRs) induced by metallic nanostructures is expected to serve as a new platform for novel [...] Read more.

Hexagonal boron nitride (hBN) exhibits natural hyperbolic dispersion in the infrared (IR) wavelength spectrum. In particular, the hybridization of its hyperbolic phonon polaritons (HPPs) and surface plasmon resonances (SPRs) induced by metallic nanostructures is expected to serve as a new platform for novel light manipulation. In this study, the transmission properties of embedded hBN in metallic one-dimensional (1D) nanoslits were theoretically investigated using a rigorous coupled wave analysis method. Extraordinary optical transmission (EOT) was observed in the type-II Reststrahlen band, which was attributed to the hybridization of HPPs in hBN and SPRs in 1D nanoslits. The calculated electric field distributions indicated that the unique Fabry–Pérot-like resonance was induced by the hybridization of HPPs and SPRs in an embedded hBN cavity. The trajectory of the confined light was a zigzag owing to the hyperbolicity of hBN, and its resonance number depended primarily on the aspect ratio of the 1D nanoslit. Such an EOT is also independent of the slit width and incident angle of light. These findings can not only assist in the development of improved strategies for the extreme confinement of IR light but may also be applied to ultrathin optical filters, advanced photodetectors, and optical devices. Full article

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

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14 pages, 5111 KiB

Open AccessEditor’s ChoiceArticle

Application of ZnO Nanoparticles in Sn99Ag0.3Cu0.7-Based Composite Solder Alloys

by Agata Skwarek, Olivér Krammer, Tamás Hurtony, Przemysław Ptak, Krzysztof Górecki, Sebastian Wroński, Dániel Straubinger, Krzysztof Witek and Balázs Illés

Nanomaterials 2021, 11(6), 1545; https://doi.org/10.3390/nano11061545 - 11 Jun 2021

Cited by 38 | Viewed by 3221

Abstract

The properties of Sn99Ag0.3Cu0.7 (SACX0307) solder alloy reinforced with ZnO nanoparticles were investigated. The primary ZnO particle sizes were 50, 100, and 200 nm. They were added to a solder paste at a ratio of 1.0 wt %. The wettability, the void formation, [...] Read more.

The properties of Sn99Ag0.3Cu0.7 (SACX0307) solder alloy reinforced with ZnO nanoparticles were investigated. The primary ZnO particle sizes were 50, 100, and 200 nm. They were added to a solder paste at a ratio of 1.0 wt %. The wettability, the void formation, the mechanical strength, and the thermoelectric parameters of the composite solder alloys/joints were investigated. Furthermore, microstructural evaluations were performed using scanning electron and ion microscopy. ZnO nanoparticles decreased the composite solder alloys’ wettability, which yielded increased void formation. Nonetheless, the shear strength and the thermoelectric parameters of the composite solder alloy were the same as those of the SACX0307 reference. This could be explained by the refinement effects of ZnO ceramics both on the Sn grains and on the Ag₃Sn and Cu₆Sn₅ intermetallic grains. This could compensate for the adverse impact of lower wettability. After improving the wettability, using more active fluxes, ZnO composite solder alloys are promising for high-power applications. Full article

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

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13 pages, 2587 KiB

Open AccessEditor’s ChoiceArticle

A Multifunctional Au/CeO₂-Mg(OH)₂ Catalyst for One-Pot Aerobic Oxidative Esterification of Aldehydes with Alcohols to Alkyl Esters

by Seulgi Lim, Seungdon Kwon, Nagyeong Kim and Kyungsu Na

Nanomaterials 2021, 11(6), 1536; https://doi.org/10.3390/nano11061536 - 10 Jun 2021

Cited by 11 | Viewed by 3487

Abstract

Au nanoparticles bound to crystalline CeO₂ nanograins that were dispersed on the nanoplate-like Mg(OH)₂, denoted as Au/CeO₂-Mg(OH)₂, were developed as the highly active and selective multifunctional heterogeneous catalyst for direct oxidative esterification of aldehydes with alcohols [...] Read more.

Au nanoparticles bound to crystalline CeO₂ nanograins that were dispersed on the nanoplate-like Mg(OH)₂, denoted as Au/CeO₂-Mg(OH)₂, were developed as the highly active and selective multifunctional heterogeneous catalyst for direct oxidative esterification of aldehydes with alcohols to produce alkyl esters under base-free aerobic conditions using oxygen or air as the green oxidants. Au/CeO₂-Mg(OH)₂ converted 93.3% of methacrylaldehyde (MACR) to methyl methacrylate (MMA, monomer of poly(methyl methacrylate)) with 98.2% selectivity within 1 h, and was repeatedly used over eight recycle runs without regeneration. The catalyst was extensively applied to other aldehydes and alcohols to produce desirable alkyl esters. Comprehensive characterization analyses revealed that the strong metal–support interaction (SMSI) among the three catalytic components (Au, CeO₂, and Mg(OH)₂), and the proximity and strong contact between Au/CeO₂ and the Mg(OH)₂ surface were prominent factors that accelerated the reaction toward a desirable oxidative esterification pathway. During the reaction, MACR was adsorbed on the surface of CeO₂-Mg(OH)₂, upon which methanol was simultaneously activated for esterifying the adsorbed MACR. Hemiacetal-form intermediate species were subsequently produced and oxidized to MMA on the surface of the electron-rich Au nanoparticles bound to partially reduced CeO_2−x with electron-donating properties. The present study provides new insights into the design of SMSI-induced supported-metal-nanoparticles for the development of novel, multifunctional, and heterogeneous catalysts. Full article

(This article belongs to the Special Issue Design and Synthesis of Nanostructured Materials for Catalytic Applications)

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17 pages, 4016 KiB

Open AccessEditor’s ChoiceArticle

Ultrabright Fluorescent Silica Nanoparticles for Dual pH and Temperature Measurements

by Saquib Ahmed M. A. Peerzade, Nadezhda Makarova and Igor Sokolov

Nanomaterials 2021, 11(6), 1524; https://doi.org/10.3390/nano11061524 - 9 Jun 2021

Cited by 9 | Viewed by 2568

Abstract

The mesoporous nature of silica nanoparticles provides a novel platform for the development of ultrabright fluorescent particles, which have organic molecular fluorescent dyes physically encapsulated inside the silica pores. The close proximity of the dye molecules, which is possible without fluorescence quenching, gives [...] Read more.

The mesoporous nature of silica nanoparticles provides a novel platform for the development of ultrabright fluorescent particles, which have organic molecular fluorescent dyes physically encapsulated inside the silica pores. The close proximity of the dye molecules, which is possible without fluorescence quenching, gives an advantage of building sensors using FRET coupling between the encapsulated dye molecules. Here we present the use of this approach to demonstrate the assembly of ultrabright fluorescent ratiometric sensors capable of simultaneous acidity (pH) and temperature measurements. FRET pairs of the temperature-responsive, pH-sensitive and reference dyes are physically encapsulated inside the silica matrix of ~50 nm particles. We demonstrate that the particles can be used to measure both the temperature in the biologically relevant range (20 to 50 °C) and pH within 4 to 7 range with the error (mean absolute deviation) of 0.54 °C and 0.09, respectively. Stability of the sensor is demonstrated. The sensitivity of the sensor ranges within 0.2–3% °C⁻¹ for the measurements of temperature and 2–6% pH⁻¹ for acidity. Full article

(This article belongs to the Special Issue Silica and Silicon Based Nanostructures)

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30 pages, 7929 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Transition Metal Dichalcogenide Cathode Materials for Aqueous Rechargeable Multivalent Metal-Ion Batteries

by Vo Pham Hoang Huy, Yong Nam Ahn and Jaehyun Hur

Nanomaterials 2021, 11(6), 1517; https://doi.org/10.3390/nano11061517 - 8 Jun 2021

Cited by 44 | Viewed by 8962

Abstract

The generation of renewable energy is a promising solution to counter the rapid increase in energy consumption. Nevertheless, the availability of renewable resources (e.g., wind, solar, and tidal) is non-continuous and temporary in nature, posing new demands for the production of next-generation large-scale [...] Read more.

The generation of renewable energy is a promising solution to counter the rapid increase in energy consumption. Nevertheless, the availability of renewable resources (e.g., wind, solar, and tidal) is non-continuous and temporary in nature, posing new demands for the production of next-generation large-scale energy storage devices. Because of their low cost, highly abundant raw materials, high safety, and environmental friendliness, aqueous rechargeable multivalent metal-ion batteries (AMMIBs) have recently garnered immense attention. However, several challenges hamper the development of AMMIBs, including their narrow electrochemical stability, poor ion diffusion kinetics, and electrode instability. Transition metal dichalcogenides (TMDs) have been extensively investigated for applications in energy storage devices because of their distinct chemical and physical properties. The wide interlayer distance of layered TMDs is an appealing property for ion diffusion and intercalation. This review focuses on the most recent advances in TMDs as cathode materials for aqueous rechargeable batteries based on multivalent charge carriers (Zn²⁺, Mg²⁺, and Al³⁺). Through this review, the key aspects of TMD materials for high-performance AMMIBs are highlighted. Furthermore, additional suggestions and strategies for the development of improved TMDs are discussed to inspire new research directions. Full article

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

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16 pages, 1976 KiB

Open AccessEditor’s ChoiceArticle

Continuous Microfluidic Production of Citrem-Phosphatidylcholine Nano-Self-Assemblies for Thymoquinone Delivery

by Esra Ilhan-Ayisigi, Aghiad Ghazal, Barbara Sartori, Maria Dimaki, Winnie Edith Svendsen, Ozlem Yesil-Celiktas and Anan Yaghmur

Nanomaterials 2021, 11(6), 1510; https://doi.org/10.3390/nano11061510 - 7 Jun 2021

Cited by 8 | Viewed by 4098

Abstract

Lamellar and non-lamellar liquid crystalline nanodispersions, including liposomes, cubosomes, and hexosomes are attractive platforms for drug delivery, bio-imaging, and related pharmaceutical applications. As compared to liposomes, there is a modest number of reports on the continuous production of cubosomes and hexosomes. Using a [...] Read more.

Lamellar and non-lamellar liquid crystalline nanodispersions, including liposomes, cubosomes, and hexosomes are attractive platforms for drug delivery, bio-imaging, and related pharmaceutical applications. As compared to liposomes, there is a modest number of reports on the continuous production of cubosomes and hexosomes. Using a binary lipid mixture of citrem and soy phosphatidylcholine (SPC), we describe the continuous production of nanocarriers for delivering thymoquinone (TQ, a substance with various therapeutic potentials) by employing a commercial microfluidic hydrodynamic flow-focusing chip. In this study, nanoparticle tracking analysis (NTA) and synchrotron small-angle X-ray scattering (SAXS) were employed to characterize TQ-free and TQ-loaded citrem/SPC nanodispersions. Microfluidic synthesis led to formation of TQ-free and TQ-loaded nanoparticles with mean sizes around 115 and 124 nm, and NTA findings indicated comparable nanoparticle size distributions in these nanodispersions. Despite the attractiveness of the microfluidic chip for continuous production of citrem/SPC nano-self-assemblies, it was not efficient as comparable mean nanoparticle sizes were obtained on employing a batch (discontinuous) method based on low-energy emulsification method. SAXS results indicated the formation of a biphasic feature of swollen lamellar (L_α) phase in coexistence with an inverse bicontinuous cubic Pn3m phase in all continuously produced TQ-free and TQ-loaded nanodispersions. Further, a set of SAXS experiments were conducted on samples prepared using the batch method for gaining further insight into the effects of ethanol and TQ concentration on the structural features of citrem/SPC nano-self-assemblies. We discuss these effects and comment on the need to introduce efficient microfluidic platforms for producing nanocarriers for delivering TQ and other therapeutic agents. Full article

(This article belongs to the Section Nanofabrication and Nanomanufacturing)

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28 pages, 5785 KiB

Open AccessEditor’s ChoiceReview

Electrospinning of Nanofibrous Membrane and Its Applications in Air Filtration: A Review

by Chenxin Lyu, Peng Zhao, Jun Xie, Shuyuan Dong, Jiawei Liu, Chengchen Rao and Jianzhong Fu

Nanomaterials 2021, 11(6), 1501; https://doi.org/10.3390/nano11061501 - 6 Jun 2021

Cited by 103 | Viewed by 9279

Abstract

Air pollution caused by particulate matter and toxic gases is violating individual’s health and safety. Nanofibrous membrane, being a reliable filter medium for particulate matter, has been extensively studied and applied in the field of air purification. Among the different fabrication approaches of [...] Read more.

Air pollution caused by particulate matter and toxic gases is violating individual’s health and safety. Nanofibrous membrane, being a reliable filter medium for particulate matter, has been extensively studied and applied in the field of air purification. Among the different fabrication approaches of nanofibrous membrane, electrospinning is considered as the most favorable and effective due to its advantages of controllable process, high production efficiency, and low cost. The electrospun membranes, made of different materials and unique structures, exhibit good PM2.5 filtration performance and multi-functions, and are used as masks and filters against PM2.5. This review presents a brief overview of electrospinning techniques, different structures of electrospun nanofibrous membranes, unique characteristics and functions of the fabricated membranes, and summarization of the outdoor and indoor applications in PM filtration. Full article

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14 pages, 2272 KiB

Open AccessEditor’s ChoiceArticle

Simultaneous Detection of Inflammatory Biomarkers by SERS Nanotag-Based Lateral Flow Assay with Portable Cloud Raman Spectrometer

by Yang Li, Xiaojia Liu, Jiuchuan Guo, Yueting Zhang, Jinhong Guo, Xinggui Wu, Bo Wang and Xing Ma

Nanomaterials 2021, 11(6), 1496; https://doi.org/10.3390/nano11061496 - 5 Jun 2021

Cited by 36 | Viewed by 4791

Abstract

Inflammatory biomarkers are closely related to infectious diseases. However, traditional clinical tests of laboratory inspection are unable to achieve rapid and accurate detection of these biomarkers on-site due to shortcomings such as complex experimental operation, expensive equipment, and long test time. Herein, we [...] Read more.

Inflammatory biomarkers are closely related to infectious diseases. However, traditional clinical tests of laboratory inspection are unable to achieve rapid and accurate detection of these biomarkers on-site due to shortcomings such as complex experimental operation, expensive equipment, and long test time. Herein, we proposed a lateral flow assay (LFA) strip based on surface-enhanced Raman scattering (SERS) nanotags (SERS-LFA strips) for the simultaneous and quantitative detection of dual infection biomarkers, serum amyloid A (SAA) and C-reactive protein (CRP), respectively. In practice, mesoporous silica (mSiO₂)-coated Au nanoparticles (Au NPs) were used as the SERS substrate. Mercaptobenzoic acid (MBA) was embedded in the internal gap between Au NPs and the mSiO₂ shell to prepare Au^MBA@mSiO₂ NPs, onto which SAA and CRP antibodies were modified to prepare two Au^MBA@mSiO₂ SERS nanotags. The Raman intensities of the test and control lines were simultaneously identified for the qualitative detection of SAA and CRP, with limits of detection (LODs) as low as 0.1 and 0.05 ng/mL for SAA and CRP, respectively. Finally, aiming at point-of-care testing (POCT) applications, we used a smartphone-based portable Raman spectrometer to quantitatively analyze the SERS-LFA strips. The Raman signal could still be accurately detected when the concentration of SAA and CRP was 10 ng/mL, which is lower than the LOD required in clinical practice for most diseases. Therefore, taking into account its simple operation and short analysis time, by using a portable Raman spectrometer which can be equipped with a 5G cloud-based healthcare management system, the current strategy based on SERS-LFA provides the potential for the quick and on-site diagnosis of infectious diseases such as sepsis, which is of great significance for medical guidance on the treatment of widely spread infection-related diseases in remote areas that lack well-developed medical resources. Full article

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

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11 pages, 4616 KiB

Open AccessEditor’s ChoiceArticle

Room-Temperature Solution-Processed 0D/1D Bilayer Electrodes for Translucent CsPbBr₃ Perovskite Photovoltaics

by Bhaskar Parida, Saemon Yoon and Dong-Won Kang

Nanomaterials 2021, 11(6), 1489; https://doi.org/10.3390/nano11061489 - 4 Jun 2021

Cited by 6 | Viewed by 3222

Abstract

Materials and processing of transparent electrodes (TEs) are key factors to creating high-performance translucent perovskite solar cells. To date, sputtered indium tin oxide (ITO) has been a general option for a rear TE of translucent solar cells. However, it requires a rather high [...] Read more.

Materials and processing of transparent electrodes (TEs) are key factors to creating high-performance translucent perovskite solar cells. To date, sputtered indium tin oxide (ITO) has been a general option for a rear TE of translucent solar cells. However, it requires a rather high cost due to vacuum process and also typically causes plasma damage to the underlying layer. Therefore, we introduced TE based on ITO nanoparticles (ITO-NPs) by solution processing in ambient air without any heat treatment. As it reveals insufficient conductivity, Ag nanowires (Ag-NWs) are additionally coated. The ITO-NPs/Ag-NW (0D/1D) bilayer TE exhibits a better figure of merit than sputtered ITO. After constructing CsPbBr₃ perovskite solar cells, the device with 0D/1D TE offers similar average visible transmission with the cells with sputtered ITO. More interestingly, the power conversion efficiency of 0D/1D TE device was 5.64%, which outperforms the cell (4.14%) made with sputtered-ITO. These impressive findings could open up a new pathway for the development of low-cost, translucent solar cells with quick processing under ambient air at room temperature. Full article

(This article belongs to the Special Issue Perovskite Nanostructures: From Material Design to Applications)

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17 pages, 3370 KiB

Open AccessEditor’s ChoiceArticle

Polyhydroxyalkanoate Nanoparticles for Pulmonary Drug Delivery: Interaction with Lung Surfactant

by Olga Cañadas, Andrea García-García, M. Auxiliadora Prieto and Jesús Pérez-Gil

Nanomaterials 2021, 11(6), 1482; https://doi.org/10.3390/nano11061482 - 3 Jun 2021

Cited by 25 | Viewed by 4019

Abstract

Polyhydroxyalkanoates (PHA) are polyesters produced intracellularly by many bacterial species as energy storage materials, which are used in biomedical applications, including drug delivery systems, due to their biocompatibility and biodegradability. In this study, we evaluated the potential application of this nanomaterial as a [...] Read more.

Polyhydroxyalkanoates (PHA) are polyesters produced intracellularly by many bacterial species as energy storage materials, which are used in biomedical applications, including drug delivery systems, due to their biocompatibility and biodegradability. In this study, we evaluated the potential application of this nanomaterial as a basis of inhaled drug delivery systems. To that end, we assessed the possible interaction between PHA nanoparticles (NPs) and pulmonary surfactant using dynamic light scattering, Langmuir balances, and epifluorescence microscopy. Our results demonstrate that NPs deposited onto preformed monolayers of DPPC or DPPC/POPG bind these surfactant lipids. This interaction facilitated the translocation of the nanomaterial towards the aqueous subphase, with the subsequent loss of lipid from the interface. NPs that remained at the interface associated with liquid expanded (LE)/tilted condensed (TC) phase boundaries, decreasing the size of condensed domains and promoting the intermixing of TC and LE phases at submicroscopic scale. This provided the stability necessary for attaining high surface pressures upon compression, countering the destabilization induced by lipid loss. These effects were observed only for high NP loads, suggesting a limit for the use of these NPs in pulmonary drug delivery. Full article

(This article belongs to the Special Issue Design, Development, and Production of Nanocarriers and Nanovehicles)

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13 pages, 9733 KiB

Open AccessEditor’s ChoiceArticle

Contact Guidance Effect and Prevention of Microfouling on a Beta Titanium Alloy Surface Structured by Electron-Beam Technology

by Sara Ferraris, Fernando Warchomicka, Jacopo Barberi, Andrea Cochis, Alessandro Calogero Scalia and Silvia Spriano

Nanomaterials 2021, 11(6), 1474; https://doi.org/10.3390/nano11061474 - 2 Jun 2021

Cited by 14 | Viewed by 3361

Abstract

Nano- and micro-structuring of implantable materials constitute a promising approach to introduce mechanical contact guidance effect, drive cells colonization, as well as to prevent bacteria adhesion and biofilm aggregation, through antifouling topography. Accordingly, this paper aims to extend the application of e-beam surface [...] Read more.

Nano- and micro-structuring of implantable materials constitute a promising approach to introduce mechanical contact guidance effect, drive cells colonization, as well as to prevent bacteria adhesion and biofilm aggregation, through antifouling topography. Accordingly, this paper aims to extend the application of e-beam surface texturing and nano-structuring to the beta titanium alloys, which are of great interest for biomedical implants because of the low Young modulus and the reduction of the stress shielding effect. The paper shows that surface texturing on the micro-scale (micro-grooves) is functional to a contact guidance effect on gingival fibroblasts. Moreover, nano-structuring, derived from the e-beam surface treatment, is effective to prevent microfouling. In fact, human fibroblasts were cultivated directly onto grooved specimens showing to sense the surface micro-structure thus spreading following the grooves’ orientation. Moreover, Staphylococcus aureus colonies adhesion was prevented by the nano-topographies in comparison to the mirror-polished control, thus demonstrating promising antifouling properties. Furthermore, the research goes into detail to understand the mechanism of microfouling prevention due to nano-topography and microstructure. Full article

(This article belongs to the Special Issue Nanotechnology and Additive Manufacturing for Hard Tissue Regeneration)

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18 pages, 1755 KiB

Open AccessEditor’s ChoiceArticle

Soft, Formstable (Co)Polyester Blend Elastomers

by Axel T. Neffe, Victor Izraylit, Paul J. Hommes-Schattmann and Andreas Lendlein

Nanomaterials 2021, 11(6), 1472; https://doi.org/10.3390/nano11061472 - 1 Jun 2021

Cited by 5 | Viewed by 4229

Abstract

High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which [...] Read more.

High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which are applied as single components in implants. By careful controlling of the copolymer composition and sequence structure of poly[(L-lactide)-co-(ε-caprolactone)], it is possible to prepare hyperelastic polymer blends formed through stereocomplexation by adding poly(D-lactide) (PDLA). Low glass transition temperature T_g ≤ 0 °C of the mixed amorphous phase contributes to the low Young’s modulus E. The formation of stereocomplexes is shown in DSC by melting transitions T_m > 190 °C and in WAXS by distinct scattering maxima at 2θ = 12° and 21°. Tensile testing demonstrated that the blends are soft (E = 12–80 MPa) and show an excellent hyperelastic recovery R_rec = 66–85% while having high elongation at break ε_b up to >1000%. These properties of the blends are attained only when the copolymer has 56–62 wt% lactide content, a weight average molar mass >140 kg·mol⁻¹, and number average lactide sequence length ≥4.8, while the blend is formed with a content of 5–10 wt% of PDLA. The devised strategy to identify a suitable copolymer for stereocomplexation and blend formation is transferable to further polymer systems and will support the development of thermoplastic elastomers suitable for medical applications. Full article

(This article belongs to the Special Issue Bio-Inspired Functional Nanomaterials)

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13 pages, 2167 KiB

Open AccessEditor’s ChoiceArticle

Lead-Free Cesium Titanium Bromide Double Perovskite Nanocrystals

by G. Krishnamurthy Grandhi, Anastasia Matuhina, Maning Liu, Shambhavee Annurakshita, Harri Ali-Löytty, Godofredo Bautista and Paola Vivo

Nanomaterials 2021, 11(6), 1458; https://doi.org/10.3390/nano11061458 - 31 May 2021

Cited by 51 | Viewed by 7210

Abstract

Double perovskites are a promising family of lead-free materials that not only replace lead but also enable new optoelectronic applications beyond photovoltaics. Recently, a titanium (Ti)-based vacancy-ordered double perovskite, Cs₂TiBr₆, has been reported as an example of truly sustainable [...] Read more.

Double perovskites are a promising family of lead-free materials that not only replace lead but also enable new optoelectronic applications beyond photovoltaics. Recently, a titanium (Ti)-based vacancy-ordered double perovskite, Cs₂TiBr₆, has been reported as an example of truly sustainable and earth-abundant perovskite with controversial results in terms of photoluminescence and environmental stability. Our work looks at this material from a new perspective, i.e., at the nanoscale. We demonstrate the first colloidal synthesis of Cs₂TiX₆ nanocrystals (X = Br, Cl) and observe tunable morphology and size of the nanocrystals according to the set reaction temperature. The Cs₂TiBr₆ nanocrystals synthesized at 185 °C show a bandgap of 1.9 eV and are relatively stable up to 8 weeks in suspensions. However, they do not display notable photoluminescence. The centrosymmetric crystal structure of Cs₂TiBr₆ suggests that this material could enable third-harmonic generation (THG) responses. Indeed, we provide a clear evidence of THG signals detected by the THG microscopy technique. As only a few THG-active halide perovskite materials are known to date and they are all lead-based, our findings promote future research on Cs₂TiBr₆ as well as on other lead-free double perovskites, with stronger focus on currently unexplored nonlinear optical applications. Full article

(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials Based on Perovskites)

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12 pages, 2174 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Catalyst Crystallinity on V-Based Selective Catalytic Reduction with Ammonia

by Min Seong Lee, Sun-I Kim, Myeung-jin Lee, Bora Ye, Taehyo Kim, Hong-Dae Kim, Jung Woo Lee and Duck Hyun Lee

Nanomaterials 2021, 11(6), 1452; https://doi.org/10.3390/nano11061452 - 30 May 2021

Cited by 14 | Viewed by 3668

Abstract

In this study, we synthesized V₂O₅-WO₃/TiO₂ catalysts with different crystallinities via one-sided and isotropic heating methods. We then investigated the effects of the catalysts’ crystallinity on their acidity, surface species, and catalytic performance through various analysis [...] Read more.

In this study, we synthesized V₂O₅-WO₃/TiO₂ catalysts with different crystallinities via one-sided and isotropic heating methods. We then investigated the effects of the catalysts’ crystallinity on their acidity, surface species, and catalytic performance through various analysis techniques and a fixed-bed reactor experiment. The isotropic heating method produced crystalline V₂O₅ and WO₃, increasing the availability of both Brønsted and Lewis acid sites, while the one-sided method produced amorphous V₂O₅ and WO₃. The crystalline structure of the two species significantly enhanced NO₂ formation, causing more rapid selective catalytic reduction (SCR) reactions and greater catalyst reducibility for NO_X decomposition. This improved NO_X removal efficiency and N₂ selectivity for a wider temperature range of 200 °C–450 °C. Additionally, the synthesized, crystalline catalysts exhibited good resistance to SO₂, which is common in industrial flue gases. Through the results reported herein, this study may contribute to future studies on SCR catalysts and other catalyst systems. Full article

(This article belongs to the Special Issue Nanomaterials for Energy Conversion and Catalytic Applications)

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24 pages, 3673 KiB

Open AccessEditor’s ChoiceArticle

Carbon-Supported Trimetallic Catalysts (PdAuNi/C) for Borohydride Oxidation Reaction

by Ahmed M. A. ElSheikh, Gordana Backović, Raisa C. P. Oliveira, César A. C. Sequeira, James McGregor, Biljana Šljukić and Diogo M. F. Santos

Nanomaterials 2021, 11(6), 1441; https://doi.org/10.3390/nano11061441 - 29 May 2021

Cited by 10 | Viewed by 3621

Abstract

The synthesis of palladium-based trimetallic catalysts via a facile and scalable synthesis procedure was shown to yield highly promising materials for borohydride-based fuel cells, which are attractive for use in compact environments. This, thereby, provides a route to more environmentally friendly energy storage [...] Read more.

The synthesis of palladium-based trimetallic catalysts via a facile and scalable synthesis procedure was shown to yield highly promising materials for borohydride-based fuel cells, which are attractive for use in compact environments. This, thereby, provides a route to more environmentally friendly energy storage and generation systems. Carbon-supported trimetallic catalysts were herein prepared by three different routes: using a NaBH₄-ethylene glycol complex (PdAuNi/C_SBEG), a NaBH₄-2-propanol complex (PdAuNi/C_SBIPA), and a three-step route (PdAuNi/C_3-step). Notably, PdAuNi/C_SBIPA yielded highly dispersed trimetallic alloy particles, as determined by XRD, EDX, ICP-OES, XPS, and TEM. The activity of the catalysts for borohydride oxidation reaction was assessed by cyclic voltammetry and RDE-based procedures, with results referenced to a Pd/C catalyst. A number of exchanged electrons close to eight was obtained for PdAuNi/C_3-step and PdAuNi/C_SBIPA (7.4 and 7.1, respectively), while the others, PdAuNi/C_SBEG and Pd/C_SBIPA, presented lower values, 2.8 and 1.2, respectively. A direct borohydride-peroxide fuel cell employing PdAuNi/C_SBIPA catalyst in the anode attained a power density of 47.5 mW cm⁻² at room temperature, while the elevation of temperature to 75 °C led to an approximately four-fold increase in power density to 175 mW cm⁻². Trimetallic catalysts prepared via this synthesis route have significant potential for future development. Full article

(This article belongs to the Special Issue Nanoalloy Electrocatalysts for Electrochemical Devices)

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8 pages, 1746 KiB

Open AccessEditor’s ChoiceArticle

Funneling Spontaneous Emission into Waveguides via Epsilon-Near-Zero Metamaterials

by M. Channab, C. F. Pirri and A. Angelini

Nanomaterials 2021, 11(6), 1410; https://doi.org/10.3390/nano11061410 - 27 May 2021

Cited by 2 | Viewed by 3109

Abstract

In this work, we discuss the use of epsilon-near-zero (ENZ) metamaterials to efficiently couple light radiated by a dipolar source to an in-plane waveguide. We exploit both enhanced and directional emission provided by ENZ metamaterials to optimize the injection of light into the [...] Read more.

In this work, we discuss the use of epsilon-near-zero (ENZ) metamaterials to efficiently couple light radiated by a dipolar source to an in-plane waveguide. We exploit both enhanced and directional emission provided by ENZ metamaterials to optimize the injection of light into the waveguide by tuning the metal fill factor. We show that a net increase in intensity injected into the waveguide with respect to the total power radiated by the isolated dipole can be achieved in experimentally feasible conditions. We think the proposed system may open up new opportunities for several optical applications and integrated technologies, especially for those limited by outcoupling efficiency and emission rate. Full article

(This article belongs to the Special Issue Nanophotonic and Optical Nanomaterials)

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18 pages, 5209 KiB

Open AccessEditor’s ChoiceArticle

Fabrication, Microstructure and Colloidal Stability of Humic Acids Loaded Fe₃O₄/APTES Nanosorbents for Environmental Applications

by Lyubov Bondarenko, Erzsébet Illés, Etelka Tombácz, Gulzhian Dzhardimalieva, Nina Golubeva, Olga Tushavina, Yasuhisa Adachi and Kamila Kydralieva

Nanomaterials 2021, 11(6), 1418; https://doi.org/10.3390/nano11061418 - 27 May 2021

Cited by 26 | Viewed by 5169

Abstract

Nowadays, numerous researches are being performed to formulate nontoxic multifunctional magnetic materials possessing both high colloidal stability and magnetization, but there is a demand in the prediction of chemical and colloidal stability in water solutions. Herein, a series of silica-coated magnetite nanoparticles (MNPs) [...] Read more.

Nowadays, numerous researches are being performed to formulate nontoxic multifunctional magnetic materials possessing both high colloidal stability and magnetization, but there is a demand in the prediction of chemical and colloidal stability in water solutions. Herein, a series of silica-coated magnetite nanoparticles (MNPs) has been synthesized via the sol-gel method with and without establishing an inert atmosphere, and then it was tested in terms of humic acids (HA) loading applied as a multifunctional coating agent. The influence of ambient conditions on the microstructure, colloidal stability and HA loading of different silica-coated MNPs has been established. The XRD patterns show that the content of stoichiometric Fe₃O₄ decreases from 78.8% to 42.4% at inert and ambient atmosphere synthesis, respectively. The most striking observation was the shift of the MNPs isoelectric point from pH ~7 to 3, with an increasing HA reaching up to the reversal of the zeta potential sign as it was covered completely by HA molecules. The zeta potential data of MNPs can be used to predict the loading capacity for HA polyanions. The data help to understand the way for materials’ development with the complexation ability of humic acids and with the insolubility of silica gel to pave the way to develop a novel, efficient and magnetically separable adsorbent for contaminant removal. Full article

(This article belongs to the Special Issue Iron Oxide Nanomaterials)

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15 pages, 5552 KiB

Open AccessEditor’s ChoiceArticle

Investigation on Ge_0.8Si_0.2-Selective Atomic Layer Wet-Etching of Ge for Vertical Gate-All-Around Nanodevice

by Lu Xie, Huilong Zhu, Yongkui Zhang, Xuezheng Ai, Junjie Li, Guilei Wang, Anyan Du, Zhenzhen Kong, Qi Wang, Shunshun Lu, Chen Li, Yangyang Li, Weixing Huang and Henry H. Radamson

Nanomaterials 2021, 11(6), 1408; https://doi.org/10.3390/nano11061408 - 26 May 2021

Cited by 7 | Viewed by 4793

Abstract

For the formation of nano-scale Ge channels in vertical Gate-all-around field-effect transistors (vGAAFETs), the selective isotropic etching of Ge selective to Ge_0.8Si_0.2 was considered. In this work, a dual-selective atomic layer etching (ALE), including Ge_0.8Si_0.2-selective etching [...] Read more.

For the formation of nano-scale Ge channels in vertical Gate-all-around field-effect transistors (vGAAFETs), the selective isotropic etching of Ge selective to Ge_0.8Si_0.2 was considered. In this work, a dual-selective atomic layer etching (ALE), including Ge_0.8Si_0.2-selective etching of Ge and crystal-orientation selectivity of Ge oxidation, has been developed to control the etch rate and the size of the Ge nanowires. The ALE of Ge in p⁺-Ge_0.8Si_0.2/Ge stacks with 70% HNO₃ as oxidizer and deionized (DI) water as oxide-removal was investigated in detail. The saturated relative etched amount per cycle (REPC) and selectivity at different HNO₃ temperatures between Ge and p⁺-Ge_0.8Si_0.2 were obtained. In p⁺-Ge_0.8Si_0.2/Ge stacks with (110) sidewalls, the REPC of Ge was 3.1 nm and the saturated etching selectivity was 6.5 at HNO₃ temperature of 20 °C. The etch rate and the selectivity were affected by HNO₃ temperatures. As the HNO₃ temperature decreased to 10 °C, the REPC of Ge was decreased to 2 nm and the selectivity remained at about 7.4. Finally, the application of ALE in the formation of Ge nanowires in vGAAFETs was demonstrated where the preliminary I_d–V_ds output characteristic curves of Ge vGAAFET were provided. Full article

(This article belongs to the Special Issue Silicon Nanodevices)

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13 pages, 2477 KiB

Open AccessEditor’s ChoiceArticle

Dielectric Imaging of Fixed HeLa Cells by In-Liquid Scanning Dielectric Force Volume Microscopy

by Martí Checa, Ruben Millan-Solsona, Adrianna Glinkowska Mares, Silvia Pujals and Gabriel Gomila

Nanomaterials 2021, 11(6), 1402; https://doi.org/10.3390/nano11061402 - 25 May 2021

Cited by 7 | Viewed by 5441

Abstract

Mapping the dielectric properties of cells with nanoscale spatial resolution can be an important tool in nanomedicine and nanotoxicity analysis, which can complement structural and mechanical nanoscale measurements. Recently we have shown that dielectric constant maps can be obtained on dried fixed cells [...] Read more.

Mapping the dielectric properties of cells with nanoscale spatial resolution can be an important tool in nanomedicine and nanotoxicity analysis, which can complement structural and mechanical nanoscale measurements. Recently we have shown that dielectric constant maps can be obtained on dried fixed cells in air environment by means of scanning dielectric force volume microscopy. Here, we demonstrate that such measurements can also be performed in the much more challenging case of fixed cells in liquid environment. Performing the measurements in liquid media contributes to preserve better the structure of the fixed cells, while also enabling accessing the local dielectric properties under fully hydrated conditions. The results shown in this work pave the way to address the nanoscale dielectric imaging of living cells, for which still further developments are required, as discussed here. Full article

(This article belongs to the Special Issue Microscopy for Nanomedicine Research)

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7 pages, 1773 KiB

Open AccessEditor’s ChoiceArticle

Single-Pixel Photon-Counting Imaging Based on Dual-Comb Interferometry

by Huiqin Hu, Xinyi Ren, Zhaoyang Wen, Xingtong Li, Yan Liang, Ming Yan and E Wu

Nanomaterials 2021, 11(6), 1379; https://doi.org/10.3390/nano11061379 - 24 May 2021

Cited by 8 | Viewed by 3599

Abstract

We propose and experimentally demonstrate single-pixel photon counting imaging based on dual-comb interferometry at 1550 nm. Different from traditional dual-comb imaging, this approach enables imaging at the photon-counting regime by using single-photon detectors combined with a time-correlated single-photon counter to record the returning [...] Read more.

We propose and experimentally demonstrate single-pixel photon counting imaging based on dual-comb interferometry at 1550 nm. Different from traditional dual-comb imaging, this approach enables imaging at the photon-counting regime by using single-photon detectors combined with a time-correlated single-photon counter to record the returning photons. The illumination power is as low as 14 pW, corresponding to 2.2 × 10⁻³ photons/pulse. The lateral resolution is about 50 μm. This technique paves the way for applying dual-comb in remote sensing and imaging. Full article

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

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7 pages, 1673 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Enantioselective Self-Assembled Nanofibrillar Network with Glutamide-Based Organogelator

by Nao Nagatomo, Hisashi Oishi, Yutaka Kuwahara, Makoto Takafuji, Reiko Oda, Taisuke Hamada and Hirotaka Ihara

Nanomaterials 2021, 11(6), 1376; https://doi.org/10.3390/nano11061376 - 23 May 2021

Viewed by 2455

Abstract

A chiral molecular gelation system, as a chiral host, was used to effectively realize enantioselectivity using the simple carboxylic acid functional group. For this purpose, an L-glutamic-acid-based lipidic amphiphile (G-CA) with a carboxylic head group was selected and its responsiveness to [...] Read more.

A chiral molecular gelation system, as a chiral host, was used to effectively realize enantioselectivity using the simple carboxylic acid functional group. For this purpose, an L-glutamic-acid-based lipidic amphiphile (G-CA) with a carboxylic head group was selected and its responsiveness to cationic guest molecules was investigated. The dispersion morphology of G-CA in its solution state was examined by confocal and transmission electron microscopies, while interactions between the G-CA, as the host system, and guest molecules were evaluated by UV-visible, circular dichroism, and fluorescence spectroscopies. As a result, enantioselectivity was effectively induced when G-CA formed highly ordered aggregates that provide negatively charged surfaces in which carboxyl groups are assembled in highly ordered states, and when the two cationic groups of the guest molecule are attached to this surface through multiple interactions. Full article

(This article belongs to the Special Issue Self-Assembled Nanostructures for Molecular Recognition)

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11 pages, 12987 KiB

Open AccessEditor’s ChoiceArticle

Creation of Negatively Charged Boron Vacancies in Hexagonal Boron Nitride Crystal by Electron Irradiation and Mechanism of Inhomogeneous Broadening of Boron Vacancy-Related Spin Resonance Lines

by Fadis F. Murzakhanov, Boris V. Yavkin, Georgiy V. Mamin, Sergei B. Orlinskii, Ivan E. Mumdzhi, Irina N. Gracheva, Bulat F. Gabbasov, Alexander N. Smirnov, Valery Yu. Davydov and Victor A. Soltamov

Nanomaterials 2021, 11(6), 1373; https://doi.org/10.3390/nano11061373 - 22 May 2021

Cited by 42 | Viewed by 6185

Abstract

Optically addressable high-spin states (S ≥ 1) of defects in semiconductors are the basis for the development of solid-state quantum technologies. Recently, one such defect has been found in hexagonal boron nitride (hBN) and identified as a negatively charged boron vacancy ( [...] Read more.

Optically addressable high-spin states (S ≥ 1) of defects in semiconductors are the basis for the development of solid-state quantum technologies. Recently, one such defect has been found in hexagonal boron nitride (hBN) and identified as a negatively charged boron vacancy (

V_{B}^{-}

). To explore and utilize the properties of this defect, one needs to design a robust way for its creation in an hBN crystal. We investigate the possibility of creating

V_{B}^{-}

centers in an hBN single crystal by means of irradiation with a high-energy (E = 2 MeV) electron flux. Optical excitation of the irradiated sample induces fluorescence in the near-infrared range together with the electron spin resonance (ESR) spectrum of the triplet centers with a zero-field splitting value of D = 3.6 GHz, manifesting an optically induced population inversion of the ground state spin sublevels. These observations are the signatures of the

V_{B}^{-}

centers and demonstrate that electron irradiation can be reliably used to create these centers in hBN. Exploration of the

V_{B}^{-}

spin resonance line shape allowed us to establish the source of the line broadening, which occurs due to the slight deviation in orientation of the two-dimensional B-N atomic plains being exactly parallel relative to each other. The results of the analysis of the broadening mechanism can be used for the crystalline quality control of the 2D materials, using the

V_{B}^{-}

spin embedded in the hBN as a probe. Full article

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21 pages, 4891 KiB

Open AccessEditor’s ChoiceArticle

Influence of Physicochemical Characteristics and Stability of Gold and Silver Nanoparticles on Biological Effects and Translocation across an Intestinal Barrier—A Case Study from In Vitro to In Silico

by Yvonne Kohl, Michelle Hesler, Roland Drexel, Lukas Kovar, Stephan Dähnhardt-Pfeiffer, Dominik Selzer, Sylvia Wagner, Thorsten Lehr, Hagen von Briesen and Florian Meier

Nanomaterials 2021, 11(6), 1358; https://doi.org/10.3390/nano11061358 - 21 May 2021

Cited by 10 | Viewed by 3519

Abstract

A better understanding of their interaction with cell-based tissue is a fundamental prerequisite towards the safe production and application of engineered nanomaterials. Quantitative experimental data on the correlation between physicochemical characteristics and the interaction and transport of engineered nanomaterials across biological barriers, in [...] Read more.

A better understanding of their interaction with cell-based tissue is a fundamental prerequisite towards the safe production and application of engineered nanomaterials. Quantitative experimental data on the correlation between physicochemical characteristics and the interaction and transport of engineered nanomaterials across biological barriers, in particular, is still scarce, thus hampering the development of effective predictive non-testing strategies. Against this background, the presented study investigated the translocation of gold and silver nanoparticles across the gastrointestinal barrier along with related biological effects using an in vitro 3D-triple co-culture cell model. Standardized in vitro assays and quantitative polymerase chain reaction showed no significant influence of the applied nanoparticles on both cell viability and generation of reactive oxygen species. Transmission electron microscopy indicated an intact cell barrier during the translocation study. Single particle ICP-MS revealed a time-dependent increase of translocated nanoparticles independent of their size, shape, surface charge, and stability in cell culture medium. This quantitative data provided the experimental basis for the successful mathematical description of the nanoparticle transport kinetics using a non-linear mixed effects modeling approach. The results of this study may serve as a basis for the development of predictive tools for improved risk assessment of engineered nanomaterials in the future. Full article

(This article belongs to the Special Issue Safety and Biocompatibility of Metallic Nanoparticles)

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24 pages, 4445 KiB

Open AccessEditor’s ChoiceArticle

Hyaluronic Acid-Based Nanocapsules as Efficient Delivery Systems of Garlic Oil Active Components with Anticancer Activity

by Małgorzata Janik-Hazuka, Kamil Kamiński, Marta Kaczor-Kamińska, Joanna Szafraniec-Szczęsny, Aleksandra Kmak, Hassan Kassassir, Cezary Watała, Maria Wróbel and Szczepan Zapotoczny

Nanomaterials 2021, 11(5), 1354; https://doi.org/10.3390/nano11051354 - 20 May 2021

Cited by 18 | Viewed by 4832

Abstract

Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are garlic oil compounds exhibiting beneficial healthy properties including anticancer action. However, these compounds are sparingly water-soluble with a limited stability that may imply damage to blood vessels or cells after administration. Thus, their encapsulation in [...] Read more.

Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are garlic oil compounds exhibiting beneficial healthy properties including anticancer action. However, these compounds are sparingly water-soluble with a limited stability that may imply damage to blood vessels or cells after administration. Thus, their encapsulation in the oil-core nanocapsules based on a derivative of hyaluronic acid was investigated here as a way of protecting against oxidation and undesired interactions with blood and digestive track components. The nuclear magnetic resonance (¹H NMR) technique was used to follow the oxidation processes. It was proved that the shell of the capsule acts as a barrier limiting the sulfur oxidation, enhancing the stability of C=C bonds in DADS and DATS. Moreover, it was shown that the encapsulation inhibited the lysis of the red blood cell membrane (mainly for DADS) and interactions with serum or digestive track components. Importantly, the biological functions and anticancer activity of DADS and DATS were preserved after encapsulation. Additionally, the nanocapsule formulations affected the migration of neoplastic cells—a desirable preliminary observation concerning the inhibition of migration. The proposed route of administration of these garlic extract components would enable reaching their higher concentrations in blood, longer circulation in a bloodstream, and thus, imply a better therapeutic effect. Full article

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

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15 pages, 5297 KiB

Open AccessEditor’s ChoiceArticle

Hydrous Hydrazine Decomposition for Hydrogen Production Using of Ir/CeO₂: Effect of Reaction Parameters on the Activity

by Davide Motta, Ilaria Barlocco, Silvio Bellomi, Alberto Villa and Nikolaos Dimitratos

Nanomaterials 2021, 11(5), 1340; https://doi.org/10.3390/nano11051340 - 19 May 2021

Cited by 27 | Viewed by 3854

Abstract

In the present work, an Ir/CeO₂ catalyst was prepared by the deposition–precipitation method and tested in the decomposition of hydrazine hydrate to hydrogen, which is very important in the development of hydrogen storage materials for fuel cells. The catalyst was characterised using [...] Read more.

In the present work, an Ir/CeO₂ catalyst was prepared by the deposition–precipitation method and tested in the decomposition of hydrazine hydrate to hydrogen, which is very important in the development of hydrogen storage materials for fuel cells. The catalyst was characterised using different techniques, i.e., X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with X-ray detector (EDX) and inductively coupled plasma—mass spectroscopy (ICP-MS). The effect of reaction conditions on the activity and selectivity of the material was evaluated in this study, modifying parameters such as temperature, the mass of the catalyst, stirring speed and concentration of base in order to find the optimal conditions of reaction, which allow performing the test in a kinetically limited regime. Full article

(This article belongs to the Section Energy and Catalysis)

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13 pages, 2725 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Visualization of Insecticides and Fungicides within Fruits and Vegetables Using Gold Nanoparticle-Immersed Paper Imprinting Mass Spectrometry Imaging

by Run Qin, Ping Li, Mingyi Du, Lianlian Ma, Yudi Huang, Zhibin Yin, Yue Zhang, Dong Chen, Hanhong Xu and Xinzhou Wu

Nanomaterials 2021, 11(5), 1327; https://doi.org/10.3390/nano11051327 - 18 May 2021

Cited by 24 | Viewed by 4226

Abstract

Food safety issues caused by pesticide residue have exerted far-reaching impacts on human daily life, yet the available detection methods normally focus on surface residue rather than pesticide penetration to the internal area of foods. Herein, we demonstrated gold nanoparticle (AuNP)-immersed paper imprinting [...] Read more.

Food safety issues caused by pesticide residue have exerted far-reaching impacts on human daily life, yet the available detection methods normally focus on surface residue rather than pesticide penetration to the internal area of foods. Herein, we demonstrated gold nanoparticle (AuNP)-immersed paper imprinting mass spectrometry imaging (MSI) for monitoring pesticide migration behaviors in various fruits and vegetables (i.e., apple, cucumber, pepper, plum, carrot, and strawberry). By manually stamping food tissues onto AuNP-immersed paper, this method affords the spatiotemporal visualization of insecticides and fungicides within fruits and vegetables, avoiding tedious and time-consuming sample preparation. Using the established MSI platform, we can track the migration of insecticides and fungicides into the inner region of foods. The results revealed that both the octanol-water partition coefficient of pesticides and water content of garden stuffs could influence the discrepancy in the migration speed of pesticides into food kernels. Taken together, this nanopaper imprinting MSI is poised to be a powerful tool because of its simplicity, rapidity, and easy operation, offering the potential to facilitate further applications in food analysis. Moreover, new perspectives are given to provide guidelines for the rational design of novel pesticide candidates, reducing the risk of food safety issues caused by pesticide residue. Full article

(This article belongs to the Special Issue Advances in Food Nanotechnology)

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10 pages, 4283 KiB

Open AccessEditor’s ChoiceArticle

Lattice-Match Stabilization and Magnetic Properties of Metastable Epitaxial Permalloy-Disilicide Nanostructures on a Vicinal Si(111) Substrate

by Anjan Bhukta, Dror Horvitz, Amit Kohn and Ilan Goldfarb

Nanomaterials 2021, 11(5), 1310; https://doi.org/10.3390/nano11051310 - 16 May 2021

Cited by 1 | Viewed by 2871

Abstract

We report the epitaxial formation of metastable γ-(Fe_xNi_1−x)Si₂ nanostructure arrays resulting from the reaction of Ni₈₀Fe₂₀ permalloy with vicinal Si(111) surface atoms. We then explore the effect of structure and composition on the nanostructure’s magnetic [...] Read more.

We report the epitaxial formation of metastable γ-(Fe_xNi_1−x)Si₂ nanostructure arrays resulting from the reaction of Ni₈₀Fe₂₀ permalloy with vicinal Si(111) surface atoms. We then explore the effect of structure and composition on the nanostructure’s magnetic properties. The low-temperature annealing (T < 600 °C) of a pre-deposited permalloy film led to solid-phase epitaxial nucleation of compact disk-shaped island nanostructures decorating <110> ledges of the stepped surface, with either (2

\times

2) or (

\sqrt{3} \times \sqrt{3}

) R30° reconstructed flat top faces. High resolution scanning transmission electron microscopy analysis demonstrated fully coherent epitaxy of the islands with respect to the substrate, consistent with a well-matched CaF₂-prototype structure associated with γ-FeSi₂, along perfect atomically sharp interfaces. Energy dispersive spectroscopy detected ternary composition of the islands, with Fe and Ni atoms confined to the islands, and no trace of segregation. Our magnetometry measurements revealed the superparamagnetic behavior of the silicide islands, with a blocking temperature around 30 K, reflecting the size, shape, and dilute arrangement of the islands in the assembly. Full article

(This article belongs to the Special Issue Epitaxial Self-Assembly of Magnetic Nanostructures)

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