Nanomaterials

13 pages, 5916 KiB

Open AccessEditor’s ChoiceArticle

Inhibition of SARS-CoV-2 Alpha Variant and Murine Noroviruses on Copper-Silver Nanocomposite Surfaces

by Dina A. Mosselhy, Lauri Kareinen, Ilkka Kivistö, Jenni Virtanen, Emil Loikkanen, Yanling Ge, Leena Maunula and Tarja Sironen

Nanomaterials 2022, 12(7), 1037; https://doi.org/10.3390/nano12071037 - 22 Mar 2022

Cited by 6 | Viewed by 3184

Abstract

With the continued scenario of the COVID-19 pandemic, the world is still seeking out-of-the-box solutions to break its transmission cycle and contain the pandemic. There are different transmission routes for viruses, including indirect transmission via surfaces. To this end, we used two relevant [...] Read more.

With the continued scenario of the COVID-19 pandemic, the world is still seeking out-of-the-box solutions to break its transmission cycle and contain the pandemic. There are different transmission routes for viruses, including indirect transmission via surfaces. To this end, we used two relevant viruses in our study. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the pandemic and human norovirus (HuNV), both known to be transmitted via surfaces. Several nanoformulations have shown attempts to inhibit SARS-CoV-2 and other viruses. However, a rigorous, similar inactivation scheme to inactivate the cords of two tedious viruses (SARS-CoV-2 Alpha variant and HuNV) is lacking. The present study demonstrates the inactivation of the SARS-CoV-2 Alpha variant and the decrease in the murine norovirus (MNV, a surrogate to HuNV) load after only one minute of contact to surfaces including copper–silver (Cu–Ag) nanocomposites. We thoroughly examined the physicochemical characteristics of such plated surfaces using diverse microscopy tools and found that Cu was the dominanting element in the tested three different surfaces (~56, ~59, and ~48 wt%, respectively), hence likely playing the major role of Alpha and MNV inactivation followed by the Ag content (~28, ~13, and ~11 wt%, respectively). These findings suggest that the administration of such surfaces within highly congested places (e.g., schools, public transportations, public toilets, and hospital and live-stock reservoirs) could break the SARS-CoV-2 and HuNV transmission. We suggest such an administration after an in-depth examination of the in vitro (especially on skin cells) and in vivo toxicity of the nanocomposite formulations and surfaces while also standardizing the physicochemical parameters, testing protocols, and animal models. Full article

(This article belongs to the Special Issue Recent Research on Nanostructured Biomedicine: Clinical Potential and Safety)

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8 pages, 4345 KiB

Open AccessEditor’s ChoiceArticle

Scalable Production of High-Quality Silver Nanowires via Continuous-Flow Droplet Synthesis

by Jianming Yu, Lijie Yang, Jing Jiang, Xunyi Dong, Zhiyang Cui, Chao Wang and Zhenda Lu

Nanomaterials 2022, 12(6), 1018; https://doi.org/10.3390/nano12061018 - 21 Mar 2022

Cited by 10 | Viewed by 3768

Abstract

Silver nanowires (Ag NWs) have shown great potential in next-generation flexible displays, due to their superior electronic, optical, and mechanical properties. However, as with most nanomaterials, a limited production capacity and poor reproduction quality, based on the batch reaction, largely hinder their application. [...] Read more.

Silver nanowires (Ag NWs) have shown great potential in next-generation flexible displays, due to their superior electronic, optical, and mechanical properties. However, as with most nanomaterials, a limited production capacity and poor reproduction quality, based on the batch reaction, largely hinder their application. Here, we applied continuous-flow synthesis for the scalable and high-quality production of Ag NWs, and built a pilot-scale line for kilogram-level per day production. In addition, we found that trace quantities of water could generate sufficient vapor as a spacer under high temperature to efficiently prevent the back-flow or mixed-flow of the reaction solution. With an optimized synthetic formula, a mass production of pure Ag NWs of 36.5 g/h was achieved by a multiple-channel, continuous-flow reactor. Full article

(This article belongs to the Topic Synthesis and Applications of Nanowires)

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22 pages, 4921 KiB

Open AccessEditor’s ChoiceArticle

Majorana Anyon Composites in Magneto-Photoluminescence Spectra of Natural Quantum Hall Puddles

by Alexander M. Mintairov, Dmitrii V. Lebedev, Alexey S. Vlasov and Steven A. Blundell

Nanomaterials 2022, 12(6), 1016; https://doi.org/10.3390/nano12061016 - 20 Mar 2022

Cited by 3 | Viewed by 2682

Abstract

In magneto-photoluminescence (magneto-PL) spectra of quasi two-dimensional islands (quantum dots) having seven electrons and Wigner–Seitz radius r_s~1.5, we revealed a suppression of magnetic field (B) dispersion, paramagnetic shifts, and jumps of the energy of the emission components for filling [...] Read more.

In magneto-photoluminescence (magneto-PL) spectra of quasi two-dimensional islands (quantum dots) having seven electrons and Wigner–Seitz radius r_s~1.5, we revealed a suppression of magnetic field (B) dispersion, paramagnetic shifts, and jumps of the energy of the emission components for filling factors ν > 1 (B < 10 T). Additionally, we observed B-hysteresis of the jumps and a dependence of all these anomalous features on r_s. Using a theoretical description of the magneto-PL spectra and an analysis of the electronic structure of these dots based on the single-particle Fock–Darwin spectrum and many-particle configuration-interaction calculations, we show that these observations can be described by the r_s-dependent formation of the anyon (magneto-electron) composites (ACs) involving single-particle states having non-zero angular momentum and that the anyon states observed involve Majorana modes (MMs), including zero-B modes having an equal number of vortexes and anti-vortexes, which can be considered as Majorana anyons. We show that the paramagnetic shift corresponds to a destruction of the equilibrium self-formed ν~5/2 AC by the external magnetic field and that the jumps and their hysteresis can be described in terms of Majorana qubit states controlled by B and r_s. Our results show a critical role of quantum confinement in the formation of magneto-electrons and implies the liquid-crystal nature of fractional quantum Hall effect states, the Majorana anyon origin of the states having even ν, i.e., composite fermions, which provide new opportunities for topological quantum computing. Full article

(This article belongs to the Special Issue Quantum Dots)

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14 pages, 3551 KiB

Open AccessEditor’s ChoiceArticle

Widely Tuneable Composition and Crystallinity of Graded Na_1+xTaO_3±δ Thin Films Fabricated by Chemical Beam Vapor Deposition

by Corrado Garlisi, Petru Lunca Popa, Kevin Menguelti, Vincent Rogé, Marc Michel, Christèle Vergne, Jérôme Guillot, Estelle Wagner, William Maudez, Giacomo Benvenuti, Bianca Rita Pistillo and Emanuele Barborini

Nanomaterials 2022, 12(6), 1012; https://doi.org/10.3390/nano12061012 - 19 Mar 2022

Cited by 3 | Viewed by 2247

Abstract

Combinatorial approach has been widely recognized as a powerful strategy to develop new-higher performance materials and shed the light on the stoichiometry-dependent properties of known systems. Herein, we take advantage of the unique features of chemical beam vapor deposition to fabricate compositionally graded [...] Read more.

Combinatorial approach has been widely recognized as a powerful strategy to develop new-higher performance materials and shed the light on the stoichiometry-dependent properties of known systems. Herein, we take advantage of the unique features of chemical beam vapor deposition to fabricate compositionally graded Na_1+xTaO_3±δ thin films with −0.6 < x < 0.5. Such a varied composition was enabled by the ability of the employed technique to deliver and combine an extensive range of precursors flows over the same deposition area. The film growth occurred in a complex process, where precursor absolute flows, flow ratios, and substrate temperature played a role. The deviation of the measured Na/Ta ratios from those predicted by flow simulations suggests that a chemical-reaction limited regime underlies the growth mechanism and highlights the importance of the Ta precursor in assisting the decomposition of the Na one. The crystallinity was observed to be strongly dependent on its stoichiometry. High under-stoichiometries (e.g., Na_0.5TaO_3−δ) compared to NaTaO₃ were detrimental for the formation of a perovskite framework, owing to the excessive amount of sodium vacancies and oxygen vacancies. Conversely, a well-crystallized orthorhombic perovskite structure peculiar of NaTaO₃ was observed from mildly under-stoichiometric (e.g., Na_0.9TaO_3−δ) to highly over-stoichiometric (e.g., Na_1.5TaO_3+δ) compositions. Full article

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8 pages, 1982 KiB

Open AccessEditor’s ChoiceArticle

Area-Selective, In-Situ Growth of Pd-Modified ZnO Nanowires on MEMS Hydrogen Sensors

by Jiahao Hu, Tao Zhang, Ying Chen, Pengcheng Xu, Dan Zheng and Xinxin Li

Nanomaterials 2022, 12(6), 1001; https://doi.org/10.3390/nano12061001 - 18 Mar 2022

Cited by 15 | Viewed by 3282

Abstract

Nanomaterials are widely utilized as sensing materials in semiconductor gas sensors. As sensor sizes continue to shrink, it becomes increasingly challenging to construct micro-scale sensing materials on a micro-sensor with good uniformity and stability. Therefore, in-situ growth with a desired pattern in the [...] Read more.

Nanomaterials are widely utilized as sensing materials in semiconductor gas sensors. As sensor sizes continue to shrink, it becomes increasingly challenging to construct micro-scale sensing materials on a micro-sensor with good uniformity and stability. Therefore, in-situ growth with a desired pattern in the tiny sensing area of a microsensor is highly demanded. In this work, we combine area-selective seed layer formation and hydrothermal growth for the in-situ growth of ZnO nanowires (NWs) on Micro-electromechanical Systems (MEMS)-based micro-hotplate gas sensors. The results show that the ZnO NWs are densely grown in the sensing area. With Pd nano-particles’ modification of the ZnO NWs, the sensor is used for hydrogen (H₂) detection. The sensors with Pd-ZnO NWs show good repeatability as well as a reversible and uniform response to 2.5 ppm–200 ppm H₂. Our approach offers a technical route for designing various kinds of gas sensors. Full article

(This article belongs to the Special Issue Advanced Nanomaterials and Nanodevices for VOCs Gas Sensor)

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15 pages, 3098 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Large-Scale MOCVD Deposition of Nanostructured TiO₂ on Stainless Steel Woven: A Systematic Investigation of Photoactivity as a Function of Film Thickness

by Alessandro Galenda, Marta Maria Natile and Naida El Habra

Nanomaterials 2022, 12(6), 992; https://doi.org/10.3390/nano12060992 - 17 Mar 2022

Cited by 7 | Viewed by 2126

Abstract

Heterogeneous photocatalysis is considered as one of the most appealing options for the treatment of organic pollutants in water. However, its definitive translation into industrial practice is still very limited because of both the complexity of large-scale production of catalysts and the problems [...] Read more.

Heterogeneous photocatalysis is considered as one of the most appealing options for the treatment of organic pollutants in water. However, its definitive translation into industrial practice is still very limited because of both the complexity of large-scale production of catalysts and the problems involved in handling the powder-based photocatalysts in the industrial plants. Here, we demonstrate that the MOCVD approach can be successfully used to prepare large-scale supported catalysts with a good photocatalytic activity towards dye degradation. The photocatalyst consisted of nanostructured TiO₂ thin film deposited on a stainless steel mesh substrate. The film thickness, the morphological features, and the crystallographic properties of the different portions of the sample were correlated to the position in the reactor chamber and the reaction conditions. The photocatalytic activity was evaluated according to the international standard test ISO 10678:2010 based on methylene blue degradation. The photocatalytic activity is essentially constant (P_MB over 40 µmol·m⁻²·h⁻¹) throughout the film, except for the portion of sample placed at the very end of the reactor chamber, where the TiO₂ film is too thin to react properly. It was assessed that a minimum film thickness of 250–300 nm is necessary to reach the maximum photocatalytic performance. Full article

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

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17 pages, 3233 KiB

Open AccessEditor’s ChoiceArticle

Enhancement of Gas Barrier Properties and Durability of Poly(butylene succinate-co-butylene adipate)-Based Nanocomposites for Food Packaging Applications

by Astrid E. Delorme, Tanja Radusin, Petri Myllytie, Vincent Verney and Haroutioun Askanian

Nanomaterials 2022, 12(6), 978; https://doi.org/10.3390/nano12060978 - 16 Mar 2022

Cited by 19 | Viewed by 3442

Abstract

Poly(butylene succinate-co-butylene adipate) (PBSA)-based materials are receiving growing attention in the packaging industry for their promising biodegradability. However, poor gas barrier properties and low durability of biodegradable polymers, such as PBSA, have limited their wide-spread use in food packaging applications. Here we report [...] Read more.

Poly(butylene succinate-co-butylene adipate) (PBSA)-based materials are receiving growing attention in the packaging industry for their promising biodegradability. However, poor gas barrier properties and low durability of biodegradable polymers, such as PBSA, have limited their wide-spread use in food packaging applications. Here we report a scalable solution to improve gas barrier properties and stabilize PBSA against photo-aging, with minimal modifications to the biodegradable polymer backbone by using a commercially available and biocompatible layered double hydroxide (LDH) filler. We investigate and compare the mechanical, gas barrier, and photoaging properties of PBSA and PBSA-LDH nanocomposite films produced on a pilot scale. An increase in rigidity in the nanocomposite was observed upon addition of LDH fillers to neat PBSA, which direct the application of neat PBSA and PBSA-LDH nanocomposite to different food packaging applications. The addition of LDH fillers into neat PBSA improves the oxygen and water vapour barriers for the PBSA based nanocomposites, which increases the attractiveness of PBSA material in food packaging applications. Through changes in the viscoelastic behaviour, we observe an improved photo-durability of photoaged PBSA-LDH nanocomposites compared to neat PBSA. It is clear from our studies that the presence of LDH enhances the lifetime durability and modulates the photodegradation rate of the elaborated biocomposites. Full article

(This article belongs to the Special Issue Nanocomposites for Food Packaging)

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10 pages, 6817 KiB

Open AccessEditor’s ChoiceArticle

2D KBr/Graphene Heterostructures—Influence on Work Function and Friction

by Zhao Liu, Antoine Hinaut, Stefan Peeters, Sebastian Scherb, Ernst Meyer, Maria Clelia Righi and Thilo Glatzel

Nanomaterials 2022, 12(6), 968; https://doi.org/10.3390/nano12060968 - 15 Mar 2022

Cited by 3 | Viewed by 3032

Abstract

The intercalation of graphene is an effective approach to modify the electronic properties of two-dimensional heterostructures for attractive phenomena and applications. In this work, we characterize the growth and surface properties of ionic KBr layers altered by graphene using ultra-high vacuum atomic force [...] Read more.

The intercalation of graphene is an effective approach to modify the electronic properties of two-dimensional heterostructures for attractive phenomena and applications. In this work, we characterize the growth and surface properties of ionic KBr layers altered by graphene using ultra-high vacuum atomic force microscopy at room temperature. We observed a strong rippling of the KBr islands on Ir(111), which is induced by a specific layer reconstruction but disappears when graphene is introduced in between. The latter causes a consistent change in both the work function and the frictional forces measured by Kelvin probe force microscopy and frictional force microscopy, respectively. Systematic density functional theory calculations of the different systems show that the change in work function is induced by the formation of a surface dipole moment while the friction force is dominated by adhesion forces. Full article

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

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10 pages, 4852 KiB

Open AccessEditor’s ChoiceArticle

Manufacturing of Textured Bulk Fe-SmCo₅ Magnets by Severe Plastic Deformation

by Lukas Weissitsch, Martin Stückler, Stefan Wurster, Juraj Todt, Peter Knoll, Heinz Krenn, Reinhard Pippan and Andrea Bachmaier

Nanomaterials 2022, 12(6), 963; https://doi.org/10.3390/nano12060963 - 14 Mar 2022

Cited by 11 | Viewed by 2973

Abstract

Exchange-coupling between soft- and hard-magnetic phases plays an important role in the engineering of novel magnetic materials. To achieve exchange coupling, a two-phase microstructure is necessary. This interface effect is further enhanced if both phase dimensions are reduced to the nanometer scale. At [...] Read more.

Exchange-coupling between soft- and hard-magnetic phases plays an important role in the engineering of novel magnetic materials. To achieve exchange coupling, a two-phase microstructure is necessary. This interface effect is further enhanced if both phase dimensions are reduced to the nanometer scale. At the same time, it is challenging to obtain large sample dimensions. In this study, powder blends and ball-milled powder blends of Fe-SmCo₅ are consolidated and are deformed by high-pressure torsion (HPT), as this technique allows us to produce bulk magnetic materials of reasonable sizes. Additionally, the effect of severe deformation by ball-milling and severe plastic deformation by HPT on exchange coupling in Fe-SmCo₅ composites is investigated. Due to the applied shear deformation, it is possible to obtain a texture in both phases, resulting in an anisotropic magnetic behavior and an improved magnetic performance. Full article

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17 pages, 8945 KiB

Open AccessEditor’s ChoiceArticle

Metallic Effects on p-Hydroxyphenyl Porphyrin Thin-Film-Based Planar Optical Waveguide Gas Sensor: Experimental and Computational Studies

by Nuerguli Kari, Marco Zannotti, Rita Giovannetti, David Řeha, Babak Minofar, Shawket Abliz and Abliz Yimit

Nanomaterials 2022, 12(6), 944; https://doi.org/10.3390/nano12060944 - 13 Mar 2022

Cited by 12 | Viewed by 3560

Abstract

Metal effects on the gas sensing behavior of metal complexes of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) thin film was investigated in terms of detecting NO₂ gas by the planar optical waveguide. For this purpose, several THPP and metal complexes were synthesized with different central metal [...] Read more.

Metal effects on the gas sensing behavior of metal complexes of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) thin film was investigated in terms of detecting NO₂ gas by the planar optical waveguide. For this purpose, several THPP and metal complexes were synthesized with different central metal ions: Co(II), Ni(II), Cu(II), and Zn(II). Planar optical gas sensors were fabricated with the metalloporphyrins deposited on K⁺ ion-exchanged soda-lime glass substrate with the spin coating method serving as host matrices for gas interaction. All of the THPP complex’s films were fully characterized by UV-Vis, IR and XPS spectroscopy, and the laser light source wavelength was selected at 520 and 670 nm. The results of the planar optical waveguide sensor show that the Zn–THPP complex exhibits the strongest response with the lowest detectable gas concentration of NO₂ gas for both 520 nm and 670 nm. The Ni–THPP and Co–THPP complexes display good efficiency in the detection of NO₂, while, on the other hand, Cu–THPP shows a very low interaction with NO₂ gas, with only 50 ppm and 200 ppm detectable gas concentration for 520 nm and 670 nm, respectively. In addition, molecular dynamic simulations and quantum mechanical calculations were performed, proving to be coherent with the experimental results. Full article

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

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13 pages, 10186 KiB

Open AccessEditor’s ChoiceArticle

New Insights into the Magnetic Properties of CoFe₂O₄@SiO₂@Au Magnetoplasmonic Nanoparticles

by Rareș Bortnic, Adam Szatmari, Gabriela Souca, Răzvan Hirian, Roxana Dudric, Lucian Barbu-Tudoran, Valentin Toma, Rareș Știufiuc, Romulus Tetean and Emil Burzo

Nanomaterials 2022, 12(6), 942; https://doi.org/10.3390/nano12060942 - 12 Mar 2022

Cited by 10 | Viewed by 4444

Abstract

We report the successful synthesis and a complete magnetic characterization of CoFe₂O₄@SiO₂@Au magnetoplasmonic nanoparticles. The CoFe₂O₄ magnetic nanoparticles were prepared using the hydrothermal method. A subsequent SiO₂ shell followed by a plasmonic Au [...] Read more.

We report the successful synthesis and a complete magnetic characterization of CoFe₂O₄@SiO₂@Au magnetoplasmonic nanoparticles. The CoFe₂O₄ magnetic nanoparticles were prepared using the hydrothermal method. A subsequent SiO₂ shell followed by a plasmonic Au shell were deposited on the magnetic core creating magnetoplasmonic nanoparticles with a core–shell architecture. A spin-glass-type magnetism was shown at the surface of the CoFe₂O₄ nanograins. Depending on the external magnetic field, two types of spin-glass were identified and analyzed in correlation with the exchange field acting on octahedral and tetrahedral iron sites. The magnetization per formula unit of the CoFe₂O₄ core is not changed in the case of CoFe₂O₄@SiO₂@Au nanocomposites. The gold nanoparticles creating the plasmonic shell show a giant diamagnetic susceptibility, dependent on their crystallite sizes. Full article

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

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22 pages, 6395 KiB

Open AccessEditor’s ChoiceArticle

Long-Term Aging of Concentrated Aqueous Graphene Oxide Suspensions Seen by Rheology and Raman Spectroscopy

by Benjámin Gyarmati, Shereen Farah, Attila Farkas, György Sáfrán, Loredana Mirela Voelker-Pop and Krisztina László

Nanomaterials 2022, 12(6), 916; https://doi.org/10.3390/nano12060916 - 10 Mar 2022

Cited by 8 | Viewed by 3173

Abstract

Today, graphene oxide (GO) has gained well-deserved recognition, with its applications continuing to increase. Much of the processing of GO-based devices occurs in a dispersed form, which explains the commercialization of GO suspensions. Aging of these suspensions can, however, affect the shelf life [...] Read more.

Today, graphene oxide (GO) has gained well-deserved recognition, with its applications continuing to increase. Much of the processing of GO-based devices occurs in a dispersed form, which explains the commercialization of GO suspensions. Aging of these suspensions can, however, affect the shelf life and thus their application potential. Aging of GO preparations is often acknowledged, but no longer-term systematic study has been reported on the alteration of GO suspensions. This paper investigates high-concentration (10 mg/mL) aqueous GO suspensions over a 2-year time scale. In addition to steady shear tests, the dynamic behavior of the suspensions was studied in more detail by transient shear and frequency sweep measurements. Both the viscosity and the dynamic moduli increased with age, particularly within the first year. The results of the complementary Raman spectroscopic studies indicate that the change in the rheological behavior with aging results from a slow oxidation process occurring in the highly acidic aqueous medium during the relatively long-term storage. The (over)oxidized layers peel off spontaneously or are removed by high shear stress, resulting in increased viscosity, as it was corroborated by XRD and XPS. Full article

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

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14 pages, 3439 KiB

Open AccessEditor’s ChoiceArticle

Investigation of the Shadow Effect in Focused Ion Beam Induced Deposition

by Chen Fang and Yan Xing

Nanomaterials 2022, 12(6), 905; https://doi.org/10.3390/nano12060905 - 9 Mar 2022

Cited by 2 | Viewed by 2957

Abstract

Due to the precursor gas flow in the focused ion beam induced deposition process, a shadow effect appears behind the shading structures. This article carries out experiments with phenanthrene as the precursor gas and establishes a numerical model to define the shadow area [...] Read more.

Due to the precursor gas flow in the focused ion beam induced deposition process, a shadow effect appears behind the shading structures. This article carries out experiments with phenanthrene as the precursor gas and establishes a numerical model to define the shadow area and estimate the intensity of the shadow effect, considering the morphology of shading structure, the beam shift, and the nozzle parameters. Within the shadow area, the precursor molecule adsorption contribution is estimated by calculating the fraction of precursor gas flow in a specific direction. Finally, the number of precursor molecules within the beam impact area influenced by the shadow effect is obtained, emphasizing the important role of gas surface diffusion. The adsorption contribution within the shadow area differs a lot while deposited structures are similar in height. The error between the simulation and the experimental results is about 5%, verifying the accuracy of the proposed model. Full article

(This article belongs to the Section Nanofabrication and Nanomanufacturing)

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13 pages, 2115 KiB

Open AccessEditor’s ChoiceArticle

An Insight into the Role of Reactant Structure Effect in Pd/C Catalysed Aldehyde Hydrogenation

by Marta Stucchi, Francesca Vasile, Stefano Cattaneo, Alberto Villa, Alessandro Chieregato, Bart D. Vandegehuchte and Laura Prati

Nanomaterials 2022, 12(6), 908; https://doi.org/10.3390/nano12060908 - 9 Mar 2022

Cited by 6 | Viewed by 2712

Abstract

The different activity of a 1% Pd/carbon catalyst towards aromatic and aliphatic aldehydes hydrogenation has been explored by ¹³C NMR relaxation. The ratio between T1 relaxation times of adsorbed (ads) and free diffusing (bulk) molecules (T1_ads/T1_bulk) can be [...] Read more.

The different activity of a 1% Pd/carbon catalyst towards aromatic and aliphatic aldehydes hydrogenation has been explored by ¹³C NMR relaxation. The ratio between T1 relaxation times of adsorbed (ads) and free diffusing (bulk) molecules (T1_ads/T1_bulk) can be used as an indicator of the relative strength of interaction between the reactant and the catalytic surface, where the lower the T1_ads/T1_bulk, the higher the adsorption strength. It can be seen that 1% Pd/carbon showed a reverse catalytic behaviour towards benzaldehyde and octanal hydrogenation, which can be explained by analysing the T1 relaxation times related to each substrate in the presence of the catalyst. Comparing and correlating the different T1_ads/T1_bulk values, we were able to prove that the different catalytic results mainly depend on the contrasting adsorption behaviour of substrates on the catalyst. Moreover, the role of the solvent has been disclosed, as NMR results revealed that the adsorption of the reactants was strongly affected by the choice of solvent, which is revealed to be critical in modulating catalytic activity. As a consequence, T1_ads/T1_bulk measurements can provide a guide to the selection of appropriate reaction conditions for improving catalytic activity. Full article

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11 pages, 6463 KiB

Open AccessEditor’s ChoiceArticle

The Positive Temperature Coefficient of Resistivity in BiFeO₃ Films

by Qianqian Yang, Xiaolei Wang, Kaihua Yang, Jinxiang Deng, Ruijuan Nie, Qingsong Deng, Xuegang Chen, Hongwei Yang, Kailin Xu and Furen Wang

Nanomaterials 2022, 12(6), 892; https://doi.org/10.3390/nano12060892 - 8 Mar 2022

Cited by 6 | Viewed by 2667

Abstract

The use of lead-free ceramic film materials with positive temperature coefficient of resistivity (PTCR) is widespread in temperature heaters and sensors in micro-electromechanical systems. In this research, the out of plane transport properties of the BiFeO₃ (BFO) films have been studied. Surprisingly, [...] Read more.

The use of lead-free ceramic film materials with positive temperature coefficient of resistivity (PTCR) is widespread in temperature heaters and sensors in micro-electromechanical systems. In this research, the out of plane transport properties of the BiFeO₃ (BFO) films have been studied. Surprisingly, PTCR was found in the BFO ceramic films due to the strongly correlated interaction between the multiferroic material BFO and the superconductor YBCO perovskite oxides. To our knowledge, this is the first report on the PTCR effect of BFO films. The BFO/YBCO interface and the bulk conductivity of BFO are important for the PTCR effect, as they make it possible to compare the transport properties of Au/BFO/YBCO- and YBCO/BFO/YBCO-type structures. PTCR was observed in Au/BFO/YBCO at a bias voltage of more than 2 V, but not in the YBCO/BFO/YBCO, even with a 40 V bias voltage. PTCR was found after BFO breakdown of a YBCO/BFO/YBCO capacitor. This indicated that the conductivity of BFO is critical for PTCR. The dependence of PTCR on the superconducting transition temperature illustrates that a cooper-pair can be injected into BFO. Our work presents a method by which to produce a lead-free ceramic film material with PTCR. Full article

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11 pages, 3270 KiB

Open AccessEditor’s ChoiceArticle

Physicochemical Characterization and Antibacterial Properties of Carbon Dots from Two Mediterranean Olive Solid Waste Cultivars

by Giuseppe Nocito, Emanuele Luigi Sciuto, Domenico Franco, Francesco Nastasi, Luca Pulvirenti, Salvatore Petralia, Corrado Spinella, Giovanna Calabrese, Salvatore Guglielmino and Sabrina Conoci

Nanomaterials 2022, 12(5), 885; https://doi.org/10.3390/nano12050885 - 7 Mar 2022

Cited by 22 | Viewed by 3074

Abstract

Carbon nanomaterials have shown great potential in several fields, including biosensing, bioimaging, drug delivery, energy, catalysis, diagnostics, and nanomedicine. Recently, a new class of carbon nanomaterials, carbon dots (CDs), have attracted much attention due to their easy and inexpensive synthesis from a wide [...] Read more.

Carbon nanomaterials have shown great potential in several fields, including biosensing, bioimaging, drug delivery, energy, catalysis, diagnostics, and nanomedicine. Recently, a new class of carbon nanomaterials, carbon dots (CDs), have attracted much attention due to their easy and inexpensive synthesis from a wide range of precursors and fascinating physical, chemical, and biological properties. In this work we have developed CDs derived from olive solid wastes of two Mediterranean regions, Puglia (CDs_P) and Calabria (CDs_C) and evaluated them in terms of their physicochemical properties and antibacterial activity against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). Results show the nanosystems have a quasi-spherical shape of 12–18 nm in size for CDs_P and 15–20 nm in size for CDs_C. UV–Vis characterization indicates a broad absorption band with two main peaks at about 270 nm and 300 nm, respectively, attributed to the π-π* and n-π* transitions of the CDs, respectively. Both samples show photoluminescence (PL) spectra excitation-dependent with a maximum at λ_em = 420 nm (λ_exc = 300 nm) for CDs_P and a red-shifted at λ_em = 445 nm (λ_exc = 300 nm) for CDs_C. Band gaps values of ≈ 1.48 eV for CDs_P and ≈ 1.53 eV for CDs_C are in agreement with semiconductor behaviour. ζ potential measures show very negative values for CDs_C compared to CDs_P (three times higher, −38 mV vs. −18 mV at pH = 7). The evaluation of the antibacterial properties highlights that both CDs have higher antibacterial activity towards Gram-positive than to Gram-negative bacteria. In addition, CDs_C exhibit bactericidal behaviour at concentrations of 360, 240, and 120 µg/mL, while lesser activity was found for CDs_P (bacterial cell reduction of only 30% at the highest concentration of 360 µg/mL). This finding was correlated to the higher surface charge of CDs_C compared to CDs_P. Further investigations are in progress to confirm this hypothesis and to gain insight on the antibacterial mechanism of both cultivars. Full article

(This article belongs to the Topic Advances and Applications of Carbon Nanotubes)

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16 pages, 3509 KiB

Open AccessEditor’s ChoiceArticle

Tunable Electronic Properties of Few-Layer Tellurene under In-Plane and Out-of-Plane Uniaxial Strain

by Genwang Wang, Ye Ding, Yanchao Guan, Yang Wang and Lijun Yang

Nanomaterials 2022, 12(5), 875; https://doi.org/10.3390/nano12050875 - 6 Mar 2022

Cited by 6 | Viewed by 3198

Abstract

Strain engineering is a promising and fascinating approach to tailoring the electrical and optical properties of 2D materials, which is of great importance for fabricating excellent nano-devices. Although previous theoretical works have proved that the monolayer tellurene has desirable mechanical properties with the [...] Read more.

Strain engineering is a promising and fascinating approach to tailoring the electrical and optical properties of 2D materials, which is of great importance for fabricating excellent nano-devices. Although previous theoretical works have proved that the monolayer tellurene has desirable mechanical properties with the capability of withstanding large deformation and the tunable band gap and mobility conductance induced by in-plane strain, the effects of in-plane and out-of-plane strains on the properties of few-layer tellurene in different phases should be explored deeply. In this paper, calculations based on first-principles density functional theory were performed to predict the variation in crystal structures and electronic properties of few-layer tellurene, including the α and β phases. The analyses of mechanical properties show that few-layer α-Te can be more easily deformed in the armchair direction than β-Te owing to its lower Young’s modulus and Poisson’s ratio. The α-Te can be converted to β-Te by in-plane compressive strain. The variations in band structures indicate that the uniaxial strain can tune the band structures and even induce the semiconductor-to-metal transition in both few-layer α-Te and β-Te. Moreover, the compressive strain in the zigzag direction is the most feasible scheme due to the lower transition strain. In addition, few-layer β-Te is more easily converted to metal especially for the thicker flakes considering its smaller band gap. Hence, the strain-induced tunable electronic properties and semiconductor-to-metal transition of tellurene provide a theoretical foundation for fabricating metal–semiconductor junctions and corresponding nano-devices. Full article

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13 pages, 2326 KiB

Open AccessEditor’s ChoiceArticle

Merging Porphyrins with Gold Nanorods: Self Assembly Construct to High Fluorescent Polyelectrolyte Microcapsules

by Vanda Vaz Serra, Sofia G. Serra, Mariana C. S. Vallejo, Pedro M. R. Paulo, Nuno M. M. Moura, David Botequim, Maria Graça P. M. S. Neves and Sílvia M. B. Costa

Nanomaterials 2022, 12(5), 872; https://doi.org/10.3390/nano12050872 - 5 Mar 2022

Cited by 4 | Viewed by 3374

Abstract

Dual probe porphyrin-gold nanorod polyelectrolyte microcapsules were developed to explore the enhancing effects of a plasmonic interface of self-assembled gold nanoparticles in the fluorescence emission from porphyrins loaded into the capsules’ core. An analysis of fluorescence lifetime imaging microscopy (FLIM) data reports a [...] Read more.

Dual probe porphyrin-gold nanorod polyelectrolyte microcapsules were developed to explore the enhancing effects of a plasmonic interface of self-assembled gold nanoparticles in the fluorescence emission from porphyrins loaded into the capsules’ core. An analysis of fluorescence lifetime imaging microscopy (FLIM) data reports a notable 10⁵–10⁶-fold increase in the maximum detected photon rates from diffraction-limited spots and an overall six-fold increase in fluorescence as averaged over the whole microcapsule area. Large emission enhancements were correlated with decreases in fluorescence lifetimes. The microcapsule’s design proved effective in achieving high fluorescent hybrids and may shed light on new possibilities for advanced materials imaging applications. Full article

(This article belongs to the Topic Synthesis, Properties and Applications of Fluorescent Nanomaterials)

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17 pages, 4618 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Facile Synthesis of Sustainable Biomass-Derived Porous Biochars as Promising Electrode Materials for High-Performance Supercapacitor Applications

by Ravi Moreno Araujo Pinheiro Lima, Glaydson Simões dos Reis, Mikael Thyrel, Jose Jarib Alcaraz-Espinoza, Sylvia H. Larsson and Helinando Pequeno de Oliveira

Nanomaterials 2022, 12(5), 866; https://doi.org/10.3390/nano12050866 - 4 Mar 2022

Cited by 46 | Viewed by 4406

Abstract

Preparing sustainable and highly efficient biochars as electrodes remains a challenge for building green energy storage devices. In this study, efficient carbon electrodes for supercapacitors were prepared via a facile and sustainable single-step pyrolysis method using spruce bark as a biomass precursor. Herein, [...] Read more.

Preparing sustainable and highly efficient biochars as electrodes remains a challenge for building green energy storage devices. In this study, efficient carbon electrodes for supercapacitors were prepared via a facile and sustainable single-step pyrolysis method using spruce bark as a biomass precursor. Herein, biochars activated by KOH and ZnCl₂ are explored as templates to be applied to prepare electrodes for supercapacitors. The physical and chemical properties of biochars for application as supercapacitors electrodes were strongly affected by factors such as the nature of the activators and the meso/microporosity, which is a critical condition that affects the internal resistance and diffusive conditions for the charge accumulation process in a real supercapacitor. Results confirmed a lower internal resistance and higher phase angle for devices prepared with ZnCl₂ in association with a higher mesoporosity degree and distribution of Zn residues into the matrix. The ZnCl₂-activated biochar electrodes’ areal capacitance reached values of 342 mF cm⁻² due to the interaction of electrical double-layer capacitance/pseudocapacitance mechanisms in a matrix that favors hydrophilic interactions and the permeation of electrolytes into the pores. The results obtained in this work strongly suggest that the spruce bark can be considered a high-efficiency precursor for biobased electrode preparation to be employed in SCs. Full article

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16 pages, 5713 KiB

Open AccessEditor’s ChoiceArticle

Development of Gold Nanoparticle-Based SERS Substrates on TiO₂-Coating to Reduce the Coffee Ring Effect

by René Breuch, Daniel Klein, Cassandra Moers, Eleni Siefke, Claudia Wickleder and Peter Kaul

Nanomaterials 2022, 12(5), 860; https://doi.org/10.3390/nano12050860 - 3 Mar 2022

Cited by 7 | Viewed by 3842

Abstract

Hydrophilic surface-enhanced Raman spectroscopy (SERS) substrates were prepared by a combination of TiO₂-coatings of aluminium plates through a direct titanium tetraisopropoxide (TTIP) coating and drop coated by synthesised gold nanoparticles (AuNPs). Differences between the wettability of the untreated substrates, the slowly [...] Read more.

Hydrophilic surface-enhanced Raman spectroscopy (SERS) substrates were prepared by a combination of TiO₂-coatings of aluminium plates through a direct titanium tetraisopropoxide (TTIP) coating and drop coated by synthesised gold nanoparticles (AuNPs). Differences between the wettability of the untreated substrates, the slowly dried Ti(OH)₄ substrates and calcinated as well as plasma treated TiO₂ substrates were analysed by water contact angle (WCA) measurements. The hydrophilic behaviour of the developed substrates helped to improve the distribution of the AuNPs, which reflects in overall higher lateral SERS enhancement. Surface enhancement of the substrates was tested with target molecule rhodamine 6G (R6G) and a fibre-coupled 638 nm Raman spectrometer. Additionally, the morphology of the substrates was characterised using scanning electron microscopy (SEM) and Raman microscopy. The studies showed a reduced influence of the coffee ring effect on the particle distribution, resulting in a more broadly distributed edge region, which increased the spatial reproducibility of the measured SERS signal in the surface-enhanced Raman mapping measurements on mm scale. Full article

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10 pages, 1250 KiB

Open AccessEditor’s ChoiceArticle

Potential of TiN/GaN Heterostructures for Hot Carrier Generation and Collection

by Blake S. Simpkins, Sergey I. Maximenko and Olga Baturina

Nanomaterials 2022, 12(5), 837; https://doi.org/10.3390/nano12050837 - 2 Mar 2022

Cited by 4 | Viewed by 2640

Abstract

Herein, we find that TiN sputter-deposited on GaN displayed the desired optical properties for plasmonic applications. While this is a positive result indicating the possible use of p- or n-type GaN as a collector of plasmonically generated hot carriers, the interfacial properties differed [...] Read more.

Herein, we find that TiN sputter-deposited on GaN displayed the desired optical properties for plasmonic applications. While this is a positive result indicating the possible use of p- or n-type GaN as a collector of plasmonically generated hot carriers, the interfacial properties differed considerably depending on doping conditions. On p-type GaN, a distinct Schottky barrier was formed with a barrier height of ~0.56 eV, which will enable effective separation of photogenerated electrons and holes, a typical approach used to extend their lifetimes. On the other hand, no transport barrier was found for TiN on n-type GaN. While the lack of spontaneous carrier separation in this system will likely reduce unprompted hot carrier collection efficiencies, it enables a bias-dependent response whereby charges of the desired type (e.g., electrons) could be directed into the semiconductor or sequestered in the plasmonic material. The specific application of interest would determine which of these conditions is most desirable. Full article

(This article belongs to the Special Issue Nanophotonics for Light-Matter Interaction)

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25 pages, 3119 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Theoretical Development of Thermal Atomic Layer Deposition: A Review

by Mina Shahmohammadi, Rajib Mukherjee, Cortino Sukotjo, Urmila M. Diwekar and Christos G. Takoudis

Nanomaterials 2022, 12(5), 831; https://doi.org/10.3390/nano12050831 - 1 Mar 2022

Cited by 34 | Viewed by 9417

Abstract

Atomic layer deposition (ALD) is a vapor-phase deposition technique that has attracted increasing attention from both experimentalists and theoreticians in the last few decades. ALD is well-known to produce conformal, uniform, and pinhole-free thin films across the surface of substrates. Due to these [...] Read more.

Atomic layer deposition (ALD) is a vapor-phase deposition technique that has attracted increasing attention from both experimentalists and theoreticians in the last few decades. ALD is well-known to produce conformal, uniform, and pinhole-free thin films across the surface of substrates. Due to these advantages, ALD has found many engineering and biomedical applications. However, drawbacks of ALD should be considered. For example, the reaction mechanisms cannot be thoroughly understood through experiments. Moreover, ALD conditions such as materials, pulse and purge durations, and temperature should be optimized for every experiment. It is practically impossible to perform many experiments to find materials and deposition conditions that achieve a thin film with desired applications. Additionally, only existing materials can be tested experimentally, which are often expensive and hazardous, and their use should be minimized. To overcome ALD limitations, theoretical methods are beneficial and essential complements to experimental data. Recently, theoretical approaches have been reported to model, predict, and optimize different ALD aspects, such as materials, mechanisms, and deposition characteristics. Those methods can be validated using a different theoretical approach or a few knowledge-based experiments. This review focuses on recent computational advances in thermal ALD and discusses how theoretical methods can make experiments more efficient. Full article

(This article belongs to the Section Theory and Simulation of Nanostructures)

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23 pages, 5175 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Strain Engineering: A Pathway for Tunable Functionalities of Perovskite Metal Oxide Films

by Samyak Dhole, Aiping Chen, Wanyi Nie, Baeho Park and Quanxi Jia

Nanomaterials 2022, 12(5), 835; https://doi.org/10.3390/nano12050835 - 1 Mar 2022

Cited by 32 | Viewed by 6171

Abstract

Perovskite offers a framework that boasts various functionalities and physical properties of interest such as ferroelectricity, magnetic orderings, multiferroicity, superconductivity, semiconductor, and optoelectronic properties owing to their rich compositional diversity. These properties are also uniquely tied to their crystal distortion which is directly [...] Read more.

Perovskite offers a framework that boasts various functionalities and physical properties of interest such as ferroelectricity, magnetic orderings, multiferroicity, superconductivity, semiconductor, and optoelectronic properties owing to their rich compositional diversity. These properties are also uniquely tied to their crystal distortion which is directly affected by lattice strain. Therefore, many important properties of perovskite can be further tuned through strain engineering which can be accomplished by chemical doping or simply element substitution, interface engineering in epitaxial thin films, and special architectures such as nanocomposites. In this review, we focus on and highlight the structure–property relationships of perovskite metal oxide films and elucidate the principles to manipulate the functionalities through different modalities of strain engineering approaches. Full article

(This article belongs to the Special Issue Structure, Properties and Applications of Nanocrystalline Thin Films)

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15 pages, 4189 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Degradation of Tetracycline Hydrochloride by Cu-Doped MIL-101(Fe) Loaded Diatomite Heterogeneous Fenton Catalyst

by Kang-Ping Cui, Yu-Ying He, Kai-Jie Xu, Yu Zhang, Chang-Bin Chen, Zheng-Jiang Xu and Xing Chen

Nanomaterials 2022, 12(5), 811; https://doi.org/10.3390/nano12050811 - 28 Feb 2022

Cited by 37 | Viewed by 4749

Abstract

In this work, the combination of high surface area diatomite with Fe and Cu bimetallic MOF material catalysts (Fe_0.25Cu_0.75(BDC)@DE) were synthesized by traditional solvothermal method, and exhibited efficient degradation performance to tetracycline hydrochloride (TC). The degradation results showed: Within [...] Read more.

In this work, the combination of high surface area diatomite with Fe and Cu bimetallic MOF material catalysts (Fe_0.25Cu_0.75(BDC)@DE) were synthesized by traditional solvothermal method, and exhibited efficient degradation performance to tetracycline hydrochloride (TC). The degradation results showed: Within 120 min, about 93% of TC was degraded under the optimal conditions. From the physical–chemical characterization, it can be seen that Fe and Cu play crucial roles in the reduction of Fe³⁺ because of their synergistic effect. The synergistic effect can not only increase the generation of hydroxyl radicals (•OH), but also improve the degradation efficiency of TC. The Lewis acid property of Cu achieved the pH range of reaction system has been expanded, and it made the material degrade well under both neutral and acidic conditions. Loading into diatomite can reduce agglomeration and metal ion leaching, thus the novel catalysts exhibited low metal ion leaching. This catalyst has good structural stability, and less loss of performance after five reaction cycles, and the degradation efficiency of the material still reached 81.8%. High performance liquid chromatography–mass spectrometry was used to analyze the degradation intermediates of TC, it provided a deep insight of the mechanism and degradation pathway of TC by bimetallic MOFs. This allows us to gain a deeper understanding of the catalytic mechanism and degradation pathway of TC degradation by bimetallic MOFS catalysts. This work has not only achieved important progress in developing high-performance catalysts for TC degradation, but has also provided useful information for the development of MOF-based catalysts for rapid environmental remediation. Full article

(This article belongs to the Section Environmental Nanoscience and Nanotechnology)

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14 pages, 3259 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Dispersion and Orientation on Polyamide-6 Cellulose Nanocomposites Manufactured through Liquid-Assisted Extrusion

by Luísa Rosenstock Völtz, Shiyu Geng, Anita Teleman and Kristiina Oksman

Nanomaterials 2022, 12(5), 818; https://doi.org/10.3390/nano12050818 - 28 Feb 2022

Cited by 8 | Viewed by 2605

Abstract

In this study, the possibility of adding nanocellulose and its dispersion to polyamide 6 (PA6), a polymer with a high melting temperature, is investigated using melt extrusion. The main challenges of the extrusion of these materials are achieving a homogeneous dispersion and avoiding [...] Read more.

In this study, the possibility of adding nanocellulose and its dispersion to polyamide 6 (PA6), a polymer with a high melting temperature, is investigated using melt extrusion. The main challenges of the extrusion of these materials are achieving a homogeneous dispersion and avoiding the thermal degradation of nanocellulose. These challenges are overcome by using an aqueous suspension of never-dried nanocellulose, which is pumped into the molten polymer without any chemical modification or drying. Furthermore, polyethylene glycol is tested as a dispersant for nanocellulose. The dispersion, thermal degradation, and mechanical and viscoelastic properties of the nanocomposites are studied. The results show that the dispersant has a positive impact on the dispersion of nanocellulose and that the liquid-assisted melt compounding does not cause the degradation of nanocellulose. The addition of only 0.5 wt.% nanocellulose increases the stiffness of the neat polyamide 6 from 2 to 2.3 GPa and shifts the tan δ peak toward higher temperatures, indicating an interaction between PA6 and nanocellulose. The addition of the dispersant decreases the strength and modulus but has a significant effect on the elongation and toughness. To further enhance the mechanical properties of the nanocomposites, solid-state drawing is used to create an oriented structure in the polymer and nanocomposites. The orientation greatly improves its mechanical properties, and the oriented nanocomposite with polyethylene glycol as dispersant exhibits the best alignment and properties: with orientation, the strength increases from 52 to 221 MPa, modulus from 1.4 to 2.8 GPa, and toughness 30 to 33 MJ m⁻³ in a draw ratio of 2.5. This study shows that nanocellulose can be added to PA6 by liquid-assisted extrusion with good dispersion and without degradation and that the orientation of the structure is a highly-effective method for producing thermoplastic nanocomposites with excellent mechanical properties. Full article

(This article belongs to the Special Issue Preparation, Characterization and Industrial Application of Nanocellulose)

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12 pages, 4031 KiB

Open AccessEditor’s ChoiceArticle

Explorations on Growth of Blue-Green-Yellow-Red InGaN Quantum Dots by Plasma-Assisted Molecular Beam Epitaxy

by Xue Zhang, Zhiwei Xing, Wenxian Yang, Haibing Qiu, Ying Gu, Yuta Suzuki, Sakuya Kaneko, Yuki Matsuda, Shinji Izumi, Yuichi Nakamura, Yong Cai, Lifeng Bian, Shulong Lu and Atsushi Tackeuchi

Nanomaterials 2022, 12(5), 800; https://doi.org/10.3390/nano12050800 - 26 Feb 2022

Cited by 6 | Viewed by 2937

Abstract

Self-assembled growth of blue-green-yellow-red InGaN quantum dots (QDs) on GaN templates using plasma-assisted molecular beam epitaxy were investigated. We concluded that growth conditions, including small N₂ flow and high growth temperature are beneficial to the formation of InGaN QDs and improve the [...] Read more.

Self-assembled growth of blue-green-yellow-red InGaN quantum dots (QDs) on GaN templates using plasma-assisted molecular beam epitaxy were investigated. We concluded that growth conditions, including small N₂ flow and high growth temperature are beneficial to the formation of InGaN QDs and improve the crystal quality. The lower In/Ga flux ratio and lower growth temperature are favorable for the formation of QDs of long emission wavelength. Moreover, the nitrogen modulation epitaxy method can extend the wavelength of QDs from green to red. As a result, visible light emissions from 460 nm to 622 nm have been achieved. Furthermore, a 505 nm green light-emitting diode (LED) based on InGaN/GaN MQDs was prepared. The LED has a low external quantum efficiency of 0.14% and shows an efficiency droop with increasing injection current. However, electroluminescence spectra exhibited a strong wavelength stability, with a negligible shift of less than 1.0 nm as injection current density increased from 8 A/cm² to 160 A/cm², owing to the screening of polarization-related electric field in QDs. Full article

(This article belongs to the Special Issue Molecular Beam Epitaxy Growth of Quantum Wires and Quantum Dots)

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10 pages, 3476 KiB

Open AccessEditor’s ChoiceArticle

Coronene and Phthalocyanine Trapping Efficiency of a Two-Dimensional Kagomé Host-Nanoarchitecture

by Yi Wang, Xinrui Miao, Wenli Deng, Romain Brisse, Bruno Jousselme and Fabien Silly

Nanomaterials 2022, 12(5), 775; https://doi.org/10.3390/nano12050775 - 25 Feb 2022

Cited by 9 | Viewed by 2480

Abstract

The trapping of coronene and zinc phthalocyanine (ZnPc) molecules at low concentration by a two-dimensional self-assembled nanoarchitecture of a push–pull dye is investigated using scanning tunneling microscopy (STM) at the liquid–solid interface. The push–pull molecules adopt an L-shaped conformation and self-assemble on a [...] Read more.

The trapping of coronene and zinc phthalocyanine (ZnPc) molecules at low concentration by a two-dimensional self-assembled nanoarchitecture of a push–pull dye is investigated using scanning tunneling microscopy (STM) at the liquid–solid interface. The push–pull molecules adopt an L-shaped conformation and self-assemble on a graphite surface into a hydrogen-bonded Kagomé network with porous hexagonal cavities. This porous host-structure is used to trap coronene and ZnPc guest molecules. STM images reveal that only 11% of the Kagomé network cavities are filled with coronene molecules. In addition, these guest molecules are not locked in the host-network and are desorbing from the surface. In contrast, STM results reveal that the occupancy of the Kagomé cavities by ZnPc evolves linearly with time until 95% are occupied and that the host structure cavities are all occupied after few hours. Full article

(This article belongs to the Special Issue Novel Self-Assembled Organic Nanoarchitectures Stabilized by Selective and Directional Interactions Engineering and Properties)

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25 pages, 1824 KiB

Open AccessEditor’s ChoiceReview

Magnetic Nanoparticles in Bone Tissue Engineering

by Akshith Dasari, Jingyi Xue and Sanjukta Deb

Nanomaterials 2022, 12(5), 757; https://doi.org/10.3390/nano12050757 - 24 Feb 2022

Cited by 62 | Viewed by 9151

Abstract

Large bone defects with limited intrinsic regenerative potential represent a major surgical challenge and are associated with a high socio-economic burden and severe reduction in the quality of life. Tissue engineering approaches offer the possibility to induce new functional bone regeneration, with the [...] Read more.

Large bone defects with limited intrinsic regenerative potential represent a major surgical challenge and are associated with a high socio-economic burden and severe reduction in the quality of life. Tissue engineering approaches offer the possibility to induce new functional bone regeneration, with the biomimetic scaffold serving as a bridge to create a microenvironment that enables a regenerative niche at the site of damage. Magnetic nanoparticles have emerged as a potential tool in bone tissue engineering that leverages the inherent magnetism of magnetic nano particles in cellular microenvironments providing direction in enhancing the osteoinductive, osteoconductive and angiogenic properties in the design of scaffolds. There are conflicting opinions and reports on the role of MNPs on these scaffolds, such as the true role of magnetism, the application of external magnetic fields in combination with MNPs, remote delivery of biomechanical stimuli in-vivo and magnetically controlled cell retention or bioactive agent delivery in promoting osteogenesis and angiogenesis. In this review, we focus on the role of magnetic nanoparticles for bone-tissue-engineering applications in both disease modelling and treatment of injuries and disease. We highlight the materials-design pathway from implementation strategy through the selection of materials and fabrication methods to evaluation. We discuss the advances in this field and unmet needs, current challenges in the development of ideal materials for bone-tissue regeneration and emerging strategies in the field. Full article

(This article belongs to the Special Issue Nanomaterials in Dentistry)

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11 pages, 1205 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Tempranillo Grape Extract in Transfersomes: A Nanoproduct with Antioxidant Activity

by Carlos Asensio-Regalado, Rosa María Alonso-Salces, Blanca Gallo, Luis A. Berrueta, Benedetta Era, Francesca Pintus and Carla Caddeo

Nanomaterials 2022, 12(5), 746; https://doi.org/10.3390/nano12050746 - 23 Feb 2022

Cited by 7 | Viewed by 2690

Abstract

Polyphenols are gaining increasing interest due to their beneficial properties to human health. Grape pomace, the by-product of wine production, is a source of these bioactive compounds. An extract from Tempranillo grape pomace was obtained and characterized qualitatively and quantitatively. The major components [...] Read more.

Polyphenols are gaining increasing interest due to their beneficial properties to human health. Grape pomace, the by-product of wine production, is a source of these bioactive compounds. An extract from Tempranillo grape pomace was obtained and characterized qualitatively and quantitatively. The major components found were anthocyanins, flavan-3-ols, and flavonols. To improve the bioavailability of these compounds, the extract was formulated in phospholipid vesicles, namely transfersomes. Spherical unilamellar vesicles around 100 nm each were obtained. The antioxidant activity of both the extract and the transfersomes was evaluated by using colorimetric assays (i.e., DPPH, FRAP, and Folin–Ciocalteu). The cells’ viability and the antioxidant activity were assessed in keratinocytes. The results showed that the extract and the transfersomes had no cytotoxic effects and exerted remarkable antioxidant activity, which was more evident in a vesicle formulation. These findings highlighted the potential of the Tempranillo grape pomace extract and the efficacy of the incorporation into phospholipid vesicles. Full article

(This article belongs to the Special Issue Nanotechnologies and Natural Compounds: Current Trends and Applications)

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11 pages, 3838 KiB

Open AccessEditor’s ChoiceArticle

Enhancing the Electrochemical Performance of Ni-Rich LiNi_0.88Co_0.09Al_0.03O₂ Cathodes through Tungsten-Doping for Lithium-Ion Batteries

by Rui Zhang, Hengrui Qiu and Youxiang Zhang

Nanomaterials 2022, 12(5), 729; https://doi.org/10.3390/nano12050729 - 22 Feb 2022

Cited by 11 | Viewed by 3295

Abstract

The tungsten-doped (0.5 and 1.0 mol%) LiNi_0.88Co_0.09Al_0.03O₂ (NCA) cathode materials are manufactured to systematically examine the stabilizing effect of W-doping. The 1.0 mol% W-doped LiNi_0.88Co_0.09Al_0.03O₂ (W1.0-NCA) cathodes deliver 173.5 [...] Read more.

The tungsten-doped (0.5 and 1.0 mol%) LiNi_0.88Co_0.09Al_0.03O₂ (NCA) cathode materials are manufactured to systematically examine the stabilizing effect of W-doping. The 1.0 mol% W-doped LiNi_0.88Co_0.09Al_0.03O₂ (W1.0-NCA) cathodes deliver 173.5 mAh g⁻¹ even after 100 cycles at 1 C, which is 95.2% of the initial capacity. While the capacity retention of NCA cathodes cycled in identical conditions is 86.3%. The optimal performances of the W1.0-NCA could be ascribed to the suppression of impendence increase and the decrease in anisotropic volume change, as well as preventing the collapse of structures during cycling. These findings demonstrate that the W-doping considerably enhances the electrochemical performance of NCA, which has potential applications in the development of Ni-rich layered cathode materials that can display high capacity with superior cycling stability. Full article

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15 pages, 7420 KiB

Open AccessEditor’s ChoiceArticle

Joining of Ti6Al4V to Al₂O₃ Using Nanomultilayers

by Marcionilo Silva, Jr., Ana Sofia Ramos, Maria Teresa Vieira and Sónia Simões

Nanomaterials 2022, 12(4), 706; https://doi.org/10.3390/nano12040706 - 21 Feb 2022

Cited by 4 | Viewed by 2432

Abstract

Diffusion bonding of Ti6Al4V to Al₂O₃ using Ni/Ti reactive nanomultilayers as interlayer material was investigated. For this purpose, Ni/Ti multilayer thin films with 12, 25, and 60 nm modulation periods (bilayer thickness) were deposited by d.c. magnetron sputtering onto the [...] Read more.

Diffusion bonding of Ti6Al4V to Al₂O₃ using Ni/Ti reactive nanomultilayers as interlayer material was investigated. For this purpose, Ni/Ti multilayer thin films with 12, 25, and 60 nm modulation periods (bilayer thickness) were deposited by d.c. magnetron sputtering onto the base materials’ surface. The joints were processed at 750 and 800 °C with a dwell time of 60 min and under a pressure of 5 MPa. Microstructural characterization of the interfaces was conducted by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). The mechanical characterization of the joints was performed by nanoindentation, and hardness and reduced Young’s modulus distribution maps were obtained across the interfaces. The joints processed at 800 °C using the three modulation periods were successful, showing the feasibility of using these nanolayered films to improve the diffusion bonding of dissimilar materials. Using modulation periods of 25 and 60 nm, it was also possible to reduce the bonding temperature to 750 °C and obtain a sound interface. The interfaces are mainly composed of NiTi and NiTi₂ phases. The nanoindentation experiments revealed that the hardness and reduced Young’s modulus at the interfaces reflect the observed microstructure. Full article

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13 pages, 4691 KiB

Open AccessEditor’s ChoiceArticle

Laser-Induced Morphological and Structural Changes of Cesium Lead Bromide Nanocrystals

by Athanasia Kostopoulou, Konstantinos Brintakis, Maria Sygletou, Kyriaki Savva, Nikolaos Livakas, Michaila Akathi Pantelaiou, Zhiya Dang, Alexandros Lappas, Liberato Manna and Emmanuel Stratakis

Nanomaterials 2022, 12(4), 703; https://doi.org/10.3390/nano12040703 - 20 Feb 2022

Cited by 7 | Viewed by 3721

Abstract

Metal halide perovskite nanocrystals, an emerging class of materials for advanced photonic and optoelectronic applications, are mainly fabricated with colloidal chemistry routes. On the quest for new properties according to application needs, new perovskite systems of various morphologies and levels of doping and [...] Read more.

Metal halide perovskite nanocrystals, an emerging class of materials for advanced photonic and optoelectronic applications, are mainly fabricated with colloidal chemistry routes. On the quest for new properties according to application needs, new perovskite systems of various morphologies and levels of doping and alloying have been developed, often also involving post-synthesis reactions. Recently, laser irradiation in liquids has been utilized as a fast method to synthesize or transform materials and interesting laser-induced transformations on nanocrystals were induced. These studies in general have been limited to small nanocrystals (~15 nm). In the case of halide perovskites, fragmentation or anion exchange have been observed in such laser-based processes, but no crystal structure transformations were actually observed or deliberately studied. Nanocrystals are more sensitive to light exposure compared to the corresponding bulk crystals. Additional factors, such as size, morphology, the presence of impurities, and others, can intricately affect the photon absorption and heat dissipation in nanocrystal suspensions during laser irradiation. All these factors can play an important role in the final morphologies and in the time required for these transformations to unfold. In the present work, we have employed a 513 nm femtosecond (fs) laser to induce different transformations in large nanocrystals, in which two phases coexist in the same particle (Cs₄PbBr₆/CsPbBr₃ nanohexagons of ~100 nm), dispersed in dichlorobenzene. These transformations include: (i) the exfoliation of the primary nanohexagons and partial anion exchange; (ii) fragmentation in smaller nanocubes and partial anion exchange; (iii) side-by-side-oriented attachment, fusion, and formation of nanoplatelets and complete anion exchange; (iv) side-by-side attachment, fusion, and formation of nanosheets. Partial or complete Br-Cl anion exchange in the above transformations was triggered by the partial degradation of dichlorobenzene. In addition to the detailed analysis of the various nanocrystal morphologies observed in the various transformations, the structure–photoluminescence relationships for the different samples were analyzed and discussed. Full article

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27 pages, 7692 KiB

Open AccessEditor’s ChoiceReview

Light-Driven Charge Transport and Optical Sensing in Molecular Junctions

by Chaolong Tang, Mehrdad Shiri, Haixin Zhang, Ridwan Tobi Ayinla and Kun Wang

Nanomaterials 2022, 12(4), 698; https://doi.org/10.3390/nano12040698 - 19 Feb 2022

Cited by 16 | Viewed by 6058

Abstract

Probing charge and energy transport in molecular junctions (MJs) has not only enabled a fundamental understanding of quantum transport at the atomic and molecular scale, but it also holds significant promise for the development of molecular-scale electronic devices. Recent years have witnessed a [...] Read more.

Probing charge and energy transport in molecular junctions (MJs) has not only enabled a fundamental understanding of quantum transport at the atomic and molecular scale, but it also holds significant promise for the development of molecular-scale electronic devices. Recent years have witnessed a rapidly growing interest in understanding light-matter interactions in illuminated MJs. These studies have profoundly deepened our knowledge of the structure–property relations of various molecular materials and paved critical pathways towards utilizing single molecules in future optoelectronics applications. In this article, we survey recent progress in investigating light-driven charge transport in MJs, including junctions composed of a single molecule and self-assembled monolayers (SAMs) of molecules, and new opportunities in optical sensing at the single-molecule level. We focus our attention on describing the experimental design, key phenomena, and the underlying mechanisms. Specifically, topics presented include light-assisted charge transport, photoswitch, and photoemission in MJs. Emerging Raman sensing in MJs is also discussed. Finally, outstanding challenges are explored, and future perspectives in the field are provided. Full article

(This article belongs to the Special Issue Molecular Electronics: Challenges and Opportunities)

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10 pages, 2144 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparative Behavior of Viscose-Based Supercapacitor Electrodes Activated by KOH, H₂O, and CO₂

by Stefan Breitenbach, Jiri Duchoslav, Andrei Ionut Mardare, Christoph Unterweger, David Stifter, Achim Walter Hassel and Christian Fürst

Nanomaterials 2022, 12(4), 677; https://doi.org/10.3390/nano12040677 - 18 Feb 2022

Cited by 10 | Viewed by 2316

Abstract

Activated carbons derived from viscose fibers were prepared using potassium hydroxide, carbon dioxide, or water vapor as activation agents. The produced activated carbon fibers were analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy, and their porosity (specific surface area, total pore [...] Read more.

Activated carbons derived from viscose fibers were prepared using potassium hydroxide, carbon dioxide, or water vapor as activation agents. The produced activated carbon fibers were analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy, and their porosity (specific surface area, total pore volume, and pore size distribution) was calculated employing physisorption experiments. Activated carbon fibers with a specific surface area of more than 2500 m² g⁻¹ were obtained by each of the three methods. Afterwards, the suitability of these materials as electrodes for electrochemical double-layer capacitors (supercapacitors) was investigated using cyclic voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. By combining CO₂ and H₂O activation, activated carbon fibers of high purity and excellent electrochemical performance could be obtained. A specific capacitance per electrode of up to 180 F g⁻¹ was found. In addition, an energy density per double-layer capacitor of 42 W h kg⁻¹ was achieved. These results demonstrate the outstanding electrochemical properties of viscose-based activated carbon fibers for use as electrode materials in energy storage devices such as supercapacitors. Full article

(This article belongs to the Special Issue Properties and Applications of Film Capacitor)

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18 pages, 5490 KiB

Open AccessEditor’s ChoiceArticle

Carbon Dots/Iron Oxide Nanoparticles with Tuneable Composition and Properties

by Joanna D. Stachowska, Monika B. Gamża, Claire Mellor, Ella N. Gibbons, Marta J. Krysmann, Antonios Kelarakis, Elżbieta Gumieniczek-Chłopek, Tomasz Strączek, Czesław Kapusta and Anna Szwajca

Nanomaterials 2022, 12(4), 674; https://doi.org/10.3390/nano12040674 - 17 Feb 2022

Cited by 12 | Viewed by 4044

Abstract

We present a simple strategy to generate a family of carbon dots/iron oxide nanoparticles (C/Fe-NPs) that relies on the thermal decomposition of iron (III) acetylacetonate in the presence of a highly fluorescent carbon-rich precursor (derived via thermal treatment of ethanolamine and citric acid [...] Read more.

We present a simple strategy to generate a family of carbon dots/iron oxide nanoparticles (C/Fe-NPs) that relies on the thermal decomposition of iron (III) acetylacetonate in the presence of a highly fluorescent carbon-rich precursor (derived via thermal treatment of ethanolamine and citric acid at 180 °C), while polyethylene glycol serves as the passivation agent. By varying the molar ratio of the reactants, a series of C/Fe-NPs have been synthesized with tuneable elemental composition in terms of C, H, O, N and Fe. The quantum yield is enhanced from 6 to 9% as the carbon content increases from 27 to 36 wt%, while the room temperature saturation magnetization is improved from 4.1 to 17.7 emu/g as the iron content is enriched from 17 to 31 wt%. In addition, the C/Fe-NPs show excellent antimicrobial properties, minimal cytotoxicity and demonstrate promising bioimaging capabilities, thus showing great potential for the development of advanced diagnostic tools. Full article

(This article belongs to the Special Issue Carbon Dots: Structure, Properties and Emerging Applications)

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12 pages, 3589 KiB

Open AccessEditor’s ChoiceArticle

The Potential for the Direct and Alternating Current-Driven Electrospinning of Polyamides

by Pavel Holec, Radek Jirkovec, Tomáš Kalous, Ondřej Baťka, Jiří Brožek and Jiří Chvojka

Nanomaterials 2022, 12(4), 665; https://doi.org/10.3390/nano12040665 - 16 Feb 2022

Cited by 9 | Viewed by 3099

Abstract

The paper provides a description of the potential for the direct current- and alternating current-driven electrospinning of various linear aliphatic polyamides (PA). Sets with increasing concentrations of selected PAs were dissolved in a mixture of formic acid and dichloromethane at a weight ratio [...] Read more.

The paper provides a description of the potential for the direct current- and alternating current-driven electrospinning of various linear aliphatic polyamides (PA). Sets with increasing concentrations of selected PAs were dissolved in a mixture of formic acid and dichloromethane at a weight ratio of 1:1 and spun using a bar electrode applying direct and alternating high voltage. The solubility and spinnability of the polyamides were investigated and scanning electron microscopy (SEM) images were acquired of the resulting nanofiber layers. The various defects of the spun fibers and their diameters were detected and subsequently measured. Moreover, the dynamic viscosity and conductivity were also subjected to detailed investigation. The most suitable concentrations for each of the PAs were determined according to previous findings, and the solutions were spun using a Nanospider^TM device at the larger scale. The fiber diameters of these samples were also measured. Finally, the surface energy of the fiber layers produced by the Nanospider^TM device was measured aimed at selecting a suitable PA for a particular application. Full article

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16 pages, 2149 KiB

Open AccessEditor’s ChoiceArticle

Water Uptake in Epoxy Ionic Liquid Free Film Polymer by Gravimetric Analysis and Comparison with Nondestructive Dielectric Analysis

by Lucas Ollivier-Lamarque, Sébastien Livi, Tetsuya Uchimoto and Nicolas Mary

Nanomaterials 2022, 12(4), 651; https://doi.org/10.3390/nano12040651 - 15 Feb 2022

Cited by 6 | Viewed by 2432

Abstract

Due to their high surface coverage, good adhesion to metal surfaces, and their excellent corrosion resistance, epoxy thermosets are widely used as protective coatings. However, anticorrosion protection of these coatings can be improved against water uptake and can be tuned by changing the [...] Read more.

Due to their high surface coverage, good adhesion to metal surfaces, and their excellent corrosion resistance, epoxy thermosets are widely used as protective coatings. However, anticorrosion protection of these coatings can be improved against water uptake and can be tuned by changing the chemical nature of the curing agents. In this work, a comparative study has been performed on the water uptake of an epoxy–amine based on bisphenol A diglycidyl ether (DGEBA) cured with an aliphatic amine and the same epoxy initiated with a phosphonium ionic liquid (IL). Thus, the epoxy networks were immersed in saline water solution in a controlled temperature environment. Gravimetric and electric impedance measurements were carried out for a maximum of 3 months. Results were analyzed in order to assess the water diffusion coefficients and water saturation limits. Two models, the Brasher–Kingsbury and a novel mixing rule, were applied on permittivity values. Results highlighted that epoxy–ionic liquid systems are less sensitive to water uptake than conventional epoxy–amine networks. Due to their higher hydrophobic properties the water diffusion coefficient of epoxy–ionic liquid systems are two times less compared to epoxy–amine samples and the water saturation limit is more than four times less. The analysis also shows that the novel mixing rule model proposed here is prone to better estimate the water uptake with accuracy from electrical impedance measurements. Full article

(This article belongs to the Special Issue Ionic Interfaces in Smart Polymer Materials)

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25 pages, 5125 KiB

Open AccessEditor’s ChoiceReview

Instantaneous Property Prediction and Inverse Design of Plasmonic Nanostructures Using Machine Learning: Current Applications and Future Directions

by Xinkai Xu, Dipesh Aggarwal and Karthik Shankar

Nanomaterials 2022, 12(4), 633; https://doi.org/10.3390/nano12040633 - 14 Feb 2022

Cited by 16 | Viewed by 4700

Abstract

Advances in plasmonic materials and devices have given rise to a variety of applications in photocatalysis, microscopy, nanophotonics, and metastructures. With the advent of computing power and artificial neural networks, the characterization and design process of plasmonic nanostructures can be significantly accelerated using [...] Read more.

Advances in plasmonic materials and devices have given rise to a variety of applications in photocatalysis, microscopy, nanophotonics, and metastructures. With the advent of computing power and artificial neural networks, the characterization and design process of plasmonic nanostructures can be significantly accelerated using machine learning as opposed to conventional FDTD simulations. The machine learning (ML) based methods can not only perform with high accuracy and return optical spectra and optimal design parameters, but also maintain a stable high computing efficiency without being affected by the structural complexity. This work reviews the prominent ML methods involved in forward simulation and inverse design of plasmonic nanomaterials, such as Convolutional Neural Networks, Generative Adversarial Networks, Genetic Algorithms and Encoder–Decoder Networks. Moreover, we acknowledge the current limitations of ML methods in the context of plasmonics and provide perspectives on future research directions. Full article

(This article belongs to the Special Issue Optical Resonators: Advanced Platform for Sensing Applications)

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15 pages, 7537 KiB

Open AccessEditor’s ChoiceArticle

Implementation of Ambipolar Polysilicon Thin-Film Transistors with Nickel Silicide Schottky Junctions by Low-Thermal-Budget Microwave Annealing

by Jin-Gi Min, Dong-Hee Lee, Yeong-Ung Kim and Won-Ju Cho

Nanomaterials 2022, 12(4), 628; https://doi.org/10.3390/nano12040628 - 13 Feb 2022

Cited by 5 | Viewed by 3320

Abstract

In this study, the efficient fabrication of nickel silicide (NiSi_x) Schottky barrier thin-film transistors (SB-TFTs) via microwave annealing (MWA) technology is proposed, and complementary metal-oxide-semiconductor (CMOS) inverters are implemented in a simplified process using ambipolar transistor properties. To validate the efficacy [...] Read more.

In this study, the efficient fabrication of nickel silicide (NiSi_x) Schottky barrier thin-film transistors (SB-TFTs) via microwave annealing (MWA) technology is proposed, and complementary metal-oxide-semiconductor (CMOS) inverters are implemented in a simplified process using ambipolar transistor properties. To validate the efficacy of the NiSi_x formation process by MWA, NiSi_x is also prepared via the conventional rapid thermal annealing (RTA) process. The Rs of the MWA NiSi_x decreases with increasing microwave power, and becomes saturated at 600 W, thus showing lower resistance than the 500 °C RTA NiSi_x. Further, SB-diodes formed on n-type and p-type bulk silicon are found to have optimal rectification characteristics at 600 W microwave power, and exhibit superior characteristics to the RTA SB-diodes. Evaluation of the electrical properties of NiSi_x SB-TFTs on excimer-laser-annealed (ELA) poly-Si substrates indicates that the MWA NiSi_x junction exhibits better ambipolar operation and transistor performance, along with improved stability. Furthermore, CMOS inverters, constructed using the ambipolar SB-TFTs, exhibit better voltage transfer characteristics, voltage gains, and dynamic inverting behavior by incorporating the MWA NiSi_x source-and-drain (S/D) junctions. Therefore, MWA is an effective process for silicide formation, and ambipolar SB-TFTs using MWA NiSi_x junctions provide a promising future for CMOS technology. Full article

(This article belongs to the Special Issue The Application of Microwave-Assisted Technology in Nanomaterials)

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14 pages, 4148 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Biomimetic 2D Nanostructures through Irradiation of Stainless Steel Surfaces with Double Femtosecond Pulses

by Matina Vlahou, Fotis Fraggelakis, Phanee Manganas, George D. Tsibidis, Anthi Ranella and Emmanuel Stratakis

Nanomaterials 2022, 12(4), 623; https://doi.org/10.3390/nano12040623 - 12 Feb 2022

Cited by 7 | Viewed by 2577

Abstract

Femtosecond laser induced changes on the topography of stainless steel with double pulses is investigated to reveal the role of parameters such as the fluence, the energy dose and the interpulse delay on the features of the produced patterns. Our results indicate that [...] Read more.

Femtosecond laser induced changes on the topography of stainless steel with double pulses is investigated to reveal the role of parameters such as the fluence, the energy dose and the interpulse delay on the features of the produced patterns. Our results indicate that short pulse separation (Δτ = 5 ps) favors the formation of 2D Low Spatially Frequency Laser Induced Periodic Surface Structures (LSFL) while longer interpulse delays (Δτ = 20 ps) lead to 2D High Spatially Frequency LIPSS (HSFL). The detailed investigation is complemented with an analysis of the produced surface patterns and characterization of their wetting and cell-adhesion properties. A correlation between the surface roughness and the contact angle is presented which confirms that topographies of variable roughness and complexity exhibit different wetting properties. Furthermore, our analysis indicates that patterns with different spatial characteristics demonstrate variable cell adhesion response which suggests that the methodology can be used as a strategy towards the fabrication of tailored surfaces for the development of functional implants. Full article

(This article belongs to the Special Issue Nanopatterning of Bionic Materials)

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12 pages, 2502 KiB

Open AccessEditor’s ChoiceArticle

Effects of the Operating Ambiance and Active Layer Treatments on the Performance of Magnesium Fluoride Based Bipolar RRAM

by Nayan C. Das, Minjae Kim, Dong-uk Kwak, Jarnardhanan R. Rani, Sung-Min Hong and Jae-Hyung Jang

Nanomaterials 2022, 12(4), 605; https://doi.org/10.3390/nano12040605 - 11 Feb 2022

Cited by 3 | Viewed by 2699

Abstract

This study investigates switching characteristics of the magnesium fluoride (MgF_x)-based bipolar resistive random-access memory (RRAM) devices at different operating ambiances (open-air and vacuum). Operating ambiances alter the elemental composition of the amorphous MgF_x active layer and Ti/MgF_x interface region, [...] Read more.

This study investigates switching characteristics of the magnesium fluoride (MgF_x)-based bipolar resistive random-access memory (RRAM) devices at different operating ambiances (open-air and vacuum). Operating ambiances alter the elemental composition of the amorphous MgF_x active layer and Ti/MgF_x interface region, which affects the overall device performance. The experimental results indicate that filament type resistive switching takes place at the interface of Ti/MgF_x and trap-controlled space charge limited conduction (SCLC) mechanisms is dominant in both the low and high resistance states in the bulk MgF_x layer. RRAM device performances at different operating ambiances are also altered by MgF_x active layer treatments (air exposure and annealing). Devices show the better uniformity, stability, and a higher on/off current ratio in vacuum compared to an open-air environment. The Ti/MgF_x/Pt memory devices have great potential for future vacuum electronic applications. Full article

(This article belongs to the Special Issue Nanomaterials for Electron Devices)

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11 pages, 11166 KiB

Open AccessEditor’s ChoiceArticle

Comprehensive Characterization of Structural, Electrical, and Mechanical Properties of Carbon Nanotube Yarns Produced by Various Spinning Methods

by Takayuki Watanabe, Satoshi Yamazaki, Satoshi Yamashita, Takumi Inaba, Shun Muroga, Takahiro Morimoto, Kazufumi Kobashi and Toshiya Okazaki

Nanomaterials 2022, 12(4), 593; https://doi.org/10.3390/nano12040593 - 10 Feb 2022

Cited by 17 | Viewed by 4523

Abstract

A comprehensive characterization of various carbon nanotube (CNT) yarns provides insight for producing high-performance CNT yarns as well as a useful guide to select the proper yarn for a specific application. Herein we systematically investigate the correlations between the physical properties of six [...] Read more.

A comprehensive characterization of various carbon nanotube (CNT) yarns provides insight for producing high-performance CNT yarns as well as a useful guide to select the proper yarn for a specific application. Herein we systematically investigate the correlations between the physical properties of six CNT yarns produced by three spinning methods, and their structures and the properties of the constituent CNTs. The electrical conductivity increases in all yarns regardless of the spinning method as the effective length of the constituent CNTs and the density of the yarns increase. On the other hand, the tensile strength shows a much stronger dependence on the packing density of the yarns than the CNT effective length, indicating the relative importance of the interfacial interaction. The contribution of each physical parameter to the yarn properties are quantitatively analyzed by partial least square regression. Full article

(This article belongs to the Topic Advances and Applications of Carbon Nanotubes)

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18 pages, 487 KiB

Open AccessEditor’s ChoiceArticle

Relation between Charging Times and Storage Properties of Nanoporous Supercapacitors

by Timur Aslyamov, Konstantin Sinkov and Iskander Akhatov

Nanomaterials 2022, 12(4), 587; https://doi.org/10.3390/nano12040587 - 9 Feb 2022

Cited by 20 | Viewed by 2709

Abstract

An optimal combination of power and energy characteristics is beneficial for the further progress of supercapacitors-based technologies. We develop a nanoscale dynamic electrolyte model, which describes both static capacitance and the time-dependent charging process, including the initial square-root dependency and two subsequent exponential [...] Read more.

An optimal combination of power and energy characteristics is beneficial for the further progress of supercapacitors-based technologies. We develop a nanoscale dynamic electrolyte model, which describes both static capacitance and the time-dependent charging process, including the initial square-root dependency and two subsequent exponential trends. The observed charging time corresponds to one of the relaxation times of the exponential regimes and significantly depends on the pore size. Additionally, we find analytical expressions providing relations of the time scales to the electrode’s parameters, applied potential, and the final state of the confined electrolyte. Our numerical results for the charging regimes agree with published computer simulations, and estimations of the charging times coincide with the experimental values. Full article

(This article belongs to the Topic Electromaterials for Environment & Energy)

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14 pages, 4461 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of Spherical Nanoparticle Hybrids via Aerosol Thiol-Ene Photopolymerization and Their Bioconjugation

by Narmin Suvarli, Max Frentzel, Jürgen Hubbuch, Iris Perner-Nochta and Michael Wörner

Nanomaterials 2022, 12(3), 577; https://doi.org/10.3390/nano12030577 - 8 Feb 2022

Cited by 6 | Viewed by 2949

Abstract

Hybrid nanomaterials possess the properties of both organic and inorganic components and find applications in various fields of research and technology. In this study, aerosol photopolymerization is used in combination with thiol-ene chemistry to produce silver poly(thio-ether) hybrid nanospheres. In aerosol photopolymerization, a [...] Read more.

Hybrid nanomaterials possess the properties of both organic and inorganic components and find applications in various fields of research and technology. In this study, aerosol photopolymerization is used in combination with thiol-ene chemistry to produce silver poly(thio-ether) hybrid nanospheres. In aerosol photopolymerization, a spray solution of monomers is atomized, forming a droplet aerosol, which then polymerizes, producing spherical polymer nanoparticles. To produce silver poly(thio-ether) hybrids, silver nanoparticles were introduced to the spray solution. Diverse methods of stabilization were used to produce stable dispersions of silver nanoparticles to prevent their agglomeration before the photopolymerization process. Successfully stabilized silver nanoparticle dispersion in the spray solution subsequently formed nanocomposites with non-agglomerated silver nanoparticles inside the polymer matrix. Nanocomposite particles were analyzed via scanning and transmission electron microscopy to study the degree of agglomeration of silver nanoparticles and their location inside the polymer spheres. The nanoparticle hybrids were then introduced onto various biofunctionalization reactions. A two-step bioconjugation process was developed involving the hybrid nanoparticles: (1) conjugation of (biotin)-maleimide to thiol-groups on the polymer network of the hybrids, and (2) biotin-streptavidin binding. The biofunctionalization with gold-nanoparticle-conjugates was carried out to confirm the reactivity of -SH groups on each conjugation step. Fluorescence-labeled biomolecules were conjugated to the spherical nanoparticle hybrids (applying the two-step bioconjugation process) verified by Fluorescence Spectroscopy and Fluorescence Microscopy. The presented research offers an effective method of synthesis of smart systems that can further be used in biosensors and various other biomedical applications. Full article

(This article belongs to the Section Nanocomposite Materials)

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16 pages, 1339 KiB

Open AccessEditor’s ChoiceArticle

Influence of Pre-Dispersion Media on the Batch Reactor Dissolution Behavior of Al₂O₃ Coated TiO₂ (NM-104) and Two ZnO (NM-110 and NM-111) Nanomaterials in Biologically Relevant Test Media

by Else Holmfred, Jens J. Sloth, Katrin Loeschner and Keld Alstrup Jensen

Nanomaterials 2022, 12(3), 566; https://doi.org/10.3390/nano12030566 - 7 Feb 2022

Cited by 4 | Viewed by 2595

Abstract

Dissolution plays an important role on pulmonary toxicity of nanomaterials (NMs). The influence of contextual parameters on the results from dissolution testing needs to be identified to improve the generation of relevant and comparable data. This study investigated how pre-dispersions made in water, [...] Read more.

Dissolution plays an important role on pulmonary toxicity of nanomaterials (NMs). The influence of contextual parameters on the results from dissolution testing needs to be identified to improve the generation of relevant and comparable data. This study investigated how pre-dispersions made in water, low-calcium Gamble’s solution, phagolysosomal simulant fluid (PSF), and 0.05% bovine serum albumin (BSA) affected the dissolution of the Al₂O₃ coating on poorly soluble TiO₂ also coated with glycerine (NM-104) and rapidly dissolving uncoated (NM-110) and triethoxycaprylsilane-coated ZnO (NM-111) NMs. Dissolution tests were undertaken and controlled in a stirred batch reactor using low-calcium Gamble’s solution and phagolysosomal simulant fluid a surrogate for the lung-lining and macrophage phagolysosomal fluid, respectively. Pre-dispersion in 0.05% BSA-water showed a significant delay or decrease in the dissolution of Al₂O₃ after testing in both low-calcium Gamble’s solution and PSF. Furthermore, use of the 0.05% BSA pre-dispersion medium influenced the dissolution of ZnO (NM-110) in PSF and ZnO (NM-111) in low-calcium Gamble’s solution and PSF. We hypothesize that BSA forms a protective coating on the particles, which delays or lowers the short-term dissolution of the materials used in this study. Consequently, the type of pre-dispersion medium can affect the results in short-term dissolution testing. Full article

(This article belongs to the Special Issue Engineered Nanomaterials Exposure and Risk Assessment: Occupational Health and Safety)

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20 pages, 5637 KiB

Open AccessEditor’s ChoiceArticle

New Epoxy Thermosets Organic-Inorganic Hybrid Nanomaterials Derived from Imidazolium Ionic Liquid Monomers and POSS^®Ph

by Houssém Chabane, Sébastien Livi, Jannick Duchet-Rumeau and Jean-François Gérard

Nanomaterials 2022, 12(3), 550; https://doi.org/10.3390/nano12030550 - 6 Feb 2022

Cited by 2 | Viewed by 2799

Abstract

New epoxy-amine networks issue from epoxydized imidazolium ionic liquid monomers (ILMs) and isophorone diamine (IPD) were modified for the first time by incorporating unmodified trisilanol phenyl POSS^® (POSS^®Ph-triol) and two ionic liquid-modified POSS^®Ph (IL-g-POSS^®Ph) having chloride (Cl [...] Read more.

New epoxy-amine networks issue from epoxydized imidazolium ionic liquid monomers (ILMs) and isophorone diamine (IPD) were modified for the first time by incorporating unmodified trisilanol phenyl POSS^® (POSS^®Ph-triol) and two ionic liquid-modified POSS^®Ph (IL-g-POSS^®Ph) having chloride (Cl⁻) and bis-trifluoromethanesulfonimidate (NTf₂⁻) counter anions. Then, 5 wt.% of unmodified and IL-modified POSS^®Ph were introduced in order to develop new solid electrolytes. First, a homogeneous dispersion of the POSS^®Ph aggregates (diameters from 80 to 400 nm) into epoxy networks was observed. As a consequence, ILM/IPD networks with glass transition temperatures between 45 and 71 °C combined with an enhancement of the thermal stability (>380 °C) were prepared. Moreover, a significant increase of the hydrophobic character and high oil repellency of the network surfaces were obtained by using IL-g-POSS^®Ph (19–20 mJ.m⁻²), opening up promising prospects for surface coating applications. Finally, these new epoxy networks exhibited outstanding high ionic conductivities (from 3.4 × 10⁻⁸ to 6.8 × 10⁻² S.m⁻¹) combined with an increase in permitivity. Full article

(This article belongs to the Special Issue Ionic Interfaces in Smart Polymer Materials)

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14 pages, 2615 KiB

Open AccessEditor’s ChoiceArticle

Carbon Dots with an Emission in the Near Infrared Produced from Organic Dyes in Porous Silica Microsphere Templates

by Evgeniia A. Stepanidenko, Ivan D. Skurlov, Pavel D. Khavlyuk, Dmitry A. Onishchuk, Aleksandra V. Koroleva, Evgeniy V. Zhizhin, Irina A. Arefina, Dmitry A. Kurdyukov, Daniil A. Eurov, Valery G. Golubev, Alexander V. Baranov, Anatoly V. Fedorov, Elena V. Ushakova and Andrey L. Rogach

Nanomaterials 2022, 12(3), 543; https://doi.org/10.3390/nano12030543 - 5 Feb 2022

Cited by 27 | Viewed by 5609

Abstract

Carbon dots (CDs) with an emission in the near infrared spectral region are attractive due to their promising applications in bio-related areas, while their fabrication still remains a challenging task. Herein, we developed a template-assisted method using porous silica microspheres for the formation [...] Read more.

Carbon dots (CDs) with an emission in the near infrared spectral region are attractive due to their promising applications in bio-related areas, while their fabrication still remains a challenging task. Herein, we developed a template-assisted method using porous silica microspheres for the formation of CDs with optical transitions in the near infrared. Two organic dyes, Rhodamine 6G and IR1061 with emission in the yellow and near infrared spectral regions, respectively, were used as precursors for CDs. Correlation of morphology and chemical composition with optical properties of obtained CDs revealed the origin of their emission, which is related to the CDs’ core optical transitions and dye-derivatives within CDs. By varying annealing temperature, different kinds of optical centers as derivatives of organic dyes are formed in the microsphere’s pores. The template-assisted method allows us to synthesize CDs with an emission peaked at 1085 nm and photoluminescence quantum yield of 0.2%, which is the highest value reported so far for CDs emitting at wavelengths longer than 1050 nm. Full article

(This article belongs to the Special Issue Luminescent Colloidal Nanocrystals)

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16 pages, 6190 KiB

Open AccessEditor’s ChoiceArticle

Reinforcing Poly(methyl methacrylate) with Bacterial Cellulose Nanofibers Chemically Modified with Methacryolyl Groups

by Hiroyuki Kono, Haruto Tsujisaki and Kenji Tajima

Nanomaterials 2022, 12(3), 537; https://doi.org/10.3390/nano12030537 - 4 Feb 2022

Cited by 15 | Viewed by 3717

Abstract

Nanofibrillated bacterial cellulose (NFBC), a type of cellulose nanofiber biosynthesized by Gluconacetobacter sp., has extremely long (i.e., high-aspect-ratio) fibers that are expected to be useful as nanofillers for fiber-reinforced composite resins. In this study, we investigated a composite of NFBC and poly(methyl methacrylate) [...] Read more.

Nanofibrillated bacterial cellulose (NFBC), a type of cellulose nanofiber biosynthesized by Gluconacetobacter sp., has extremely long (i.e., high-aspect-ratio) fibers that are expected to be useful as nanofillers for fiber-reinforced composite resins. In this study, we investigated a composite of NFBC and poly(methyl methacrylate) (PMMA), a highly transparent resin, with the aim of improving the mechanical properties of the latter. The abundant hydroxyl groups on the NFBC surface were silylated using 3-(methacryloyloxy)propyltrimethoxysilane (MPTMS), a silane coupling agent bearing a methacryloyl group as the organic functional group. The surface-modified NFBC was homogeneously dispersed in chloroform, mixed with neat PMMA, and converted into PMMA composites using a simple solvent-casting method. The tensile strength and Young’s modulus of the composite increased by factors of 1.6 and 1.8, respectively, when only 0.10 wt% of the surface-modified NFBC was added, without sacrificing the maximum elongation rate. In addition, the composite maintained the high transparency of PMMA, highlighting that the addition of MPTMS-modified NFBC easily reinforce PMMA. Furthermore, interactions involving the organic functional groups of MPTMS were found to be very important for reinforcing PMMA. Full article

(This article belongs to the Special Issue Preparation, Characterization and Industrial Application of Nanocellulose)

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11 pages, 871 KiB

Open AccessEditor’s ChoiceArticle

Hybrid Polyethylene Glycol/Sodium Metaphosphate Composites Prepared via Coacervation

by Bruno Poletto Rodrigues, Guilherme Nunes Braga Maurício de Macedo, Yang Xia, Andrea Balducci and Lothar Wondraczek

Nanomaterials 2022, 12(3), 528; https://doi.org/10.3390/nano12030528 - 3 Feb 2022

Viewed by 2249

Abstract

We report on the fabrication and characterization of homogeneous, monophasic sodium metaphosphate and polyethylene glycol hybrid composites achieved via coacervation in aqueous solution. After separation and drying, an amorphous plastic solid is formed, composed mostly of hydrated sodium phosphate moieties amalgamated with polyethylene [...] Read more.

We report on the fabrication and characterization of homogeneous, monophasic sodium metaphosphate and polyethylene glycol hybrid composites achieved via coacervation in aqueous solution. After separation and drying, an amorphous plastic solid is formed, composed mostly of hydrated sodium phosphate moieties amalgamated with polyethylene glycol chains. These composites are largely X-ray amorphous and can contain up to 8 weight percent of polymer. Impedance spectroscopic measurements reveal DC conductivity values of 12 μS/m at room temperature, an enhancement of three orders of magnitude when compared to glassy sodium metaphosphate, and the presence of the polyethylene glycol is reflected in the equivalent circuit and ionic hopping analyses. Full article

(This article belongs to the Section Nanocomposite Materials)

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14 pages, 5828 KiB

Open AccessEditor’s ChoiceArticle

Increasing Magnetic Anisotropy in Bimetallic Nanoislands Grown on fcc(111) Metal Surfaces

by Sergio Vlaic, Dimitris Mousadakos, Safia Ouazi, Stefano Rusponi and Harald Brune

Nanomaterials 2022, 12(3), 518; https://doi.org/10.3390/nano12030518 - 2 Feb 2022

Cited by 2 | Viewed by 2113

Abstract

The magnetic properties and the atomic scale morphology of bimetallic two-dimensional nanoislands, epitaxially grown on fcc(111) metal surfaces, have been studied by means of Magneto-Optical Kerr Effect and Scanning Tunneling Microscopy. We investigate the effect on blocking temperature of one-dimensional interlines appearing in [...] Read more.

The magnetic properties and the atomic scale morphology of bimetallic two-dimensional nanoislands, epitaxially grown on fcc(111) metal surfaces, have been studied by means of Magneto-Optical Kerr Effect and Scanning Tunneling Microscopy. We investigate the effect on blocking temperature of one-dimensional interlines appearing in core-shell structures, of two-dimensional interfaces created by capping, and of random alloying. The islands are grown on Pt(111) and contain a Co-core, surrounded by Ag, Rh, and Pd shells, or capped by Pd. The largest effect is obtained by Pd capping, increasing the blocking temperature by a factor of three compared to pure Co islands. In addition, for Co-core Fe-shell and Co-core Fe_xCo_1−x-shell islands, self-assembled into well ordered superlattices on Au(11,12,12) vicinal surfaces, we find a strong enhancement of the blocking temperature compared to pure Co islands of the same size. These ultra-high-density (15 Tdots/in²) superlattices of CoFe nanodots, only 500 atoms in size, have blocking temperature exceeding 100 K. Our findings open new possibilities to tailor the magnetic properties of nanoislands. Full article

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

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