Nanomaterials

13 pages, 1263 KiB

Open AccessEditor’s ChoiceArticle

Nanoparticle Size Threshold for Magnetic Agglomeration and Associated Hyperthermia Performance

by David Serantes and Daniel Baldomir

Nanomaterials 2021, 11(11), 2786; https://doi.org/10.3390/nano11112786 - 21 Oct 2021

Cited by 20 | Viewed by 2851

The likelihood of magnetic nanoparticles to agglomerate is usually estimated through the ratio between magnetic dipole-dipole and thermal energies, thus neglecting the fact that, depending on the magnitude of the magnetic anisotropy constant (K), the particle moment may fluctuate internally and [...] Read more.

The likelihood of magnetic nanoparticles to agglomerate is usually estimated through the ratio between magnetic dipole-dipole and thermal energies, thus neglecting the fact that, depending on the magnitude of the magnetic anisotropy constant (K), the particle moment may fluctuate internally and thus undermine the agglomeration process. Based on the comparison between the involved timescales, we study in this work how the threshold size for magnetic agglomeration (

d_{a g g l}

) varies depending on the K value. Our results suggest that small variations in K-due to, e.g., shape contribution, might shift

d_{a g g l}

by a few nm. A comparison with the usual superparamagnetism estimation is provided, as well as with the energy competition approach. In addition, based on the key role of the anisotropy in the hyperthermia performance, we also analyse the associated heating capability, as non-agglomerated particles would be of high interest for the application. Full article

(This article belongs to the Special Issue Interactions Effects in Nanoscaled Magnetic Assemblies)

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11 pages, 3134 KiB

Open AccessEditor’s ChoiceArticle

Sensing Performance of Thermal Electronic Noses: A Comparison between ZnO and SnO₂ Nanowires

by Matteo Tonezzer, Cristina Armellini and Laura Toniutti

Nanomaterials 2021, 11(11), 2773; https://doi.org/10.3390/nano11112773 - 20 Oct 2021

Cited by 6 | Viewed by 2156

Abstract

In recent times, an increasing number of applications in different fields need gas sensors that are miniaturized but also capable of distinguishing different gases and volatiles. Thermal electronic noses are new devices that meet this need, but their performance is still under study. [...] Read more.

In recent times, an increasing number of applications in different fields need gas sensors that are miniaturized but also capable of distinguishing different gases and volatiles. Thermal electronic noses are new devices that meet this need, but their performance is still under study. In this work, we compare the performance of two thermal electronic noses based on SnO₂ and ZnO nanowires. Using five different target gases (acetone, ammonia, ethanol, hydrogen and nitrogen dioxide), we investigated the ability of the systems to distinguish individual gases and estimate their concentration. SnO₂ nanowires proved to be more suitable for this purpose with a detection limit of 32 parts per billion, an always correct classification (100%) and a mean absolute error of 7 parts per million. Full article

(This article belongs to the Special Issue Nanostructured Gas Sensors Synthesis and Applications)

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22 pages, 3142 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 12 | Viewed by 4421

Abstract

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

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

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

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16 pages, 4289 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 3 | Viewed by 3011

Abstract

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

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

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

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35 pages, 5713 KiB

Open AccessEditor’s ChoiceReview

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

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

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

Cited by 61 | Viewed by 10948

Abstract

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

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

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

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17 pages, 7497 KiB

Open AccessEditor’s ChoiceArticle

Promising Bialkali Bismuthides Cs(Na, K)₂Bi for High-Performance Nanoscale Electromechanical Devices: Prediction of Mechanical and Anisotropic Elastic Properties under Hydrostatic Tension and Compression and Tunable Auxetic Properties

by Shahram Yalameha, Zahra Nourbakhsh, Ali Ramazani and Daryoosh Vashaee

Nanomaterials 2021, 11(10), 2739; https://doi.org/10.3390/nano11102739 - 16 Oct 2021

Cited by 8 | Viewed by 2399

Abstract

Using first-principles calculations, we predict highly stable cubic bialkali bismuthides Cs(Na, K)₂Bi with several technologically important mechanical and anisotropic elastic properties. We investigate the mechanical and anisotropic elastic properties under hydrostatic tension and compression. At zero pressure, CsK₂Bi is [...] Read more.

Using first-principles calculations, we predict highly stable cubic bialkali bismuthides Cs(Na, K)₂Bi with several technologically important mechanical and anisotropic elastic properties. We investigate the mechanical and anisotropic elastic properties under hydrostatic tension and compression. At zero pressure, CsK₂Bi is characterized by elastic anisotropy with maximum and minimum stiffness along the directions of [111] and [100], respectively. Unlike CsK₂Bi, CsNa₂Bi exhibits almost isotropic elastic behavior at zero pressure. We found that hydrostatic tension and compression change the isotropic and anisotropic mechanical responses of these compounds. Moreover, the auxetic nature of the CsK₂Bi compound is tunable under pressure. This compound transforms into a material with a positive Poisson’s ratio under hydrostatic compression, while it holds a large negative Poisson’s ratio of about −0.45 along the [111] direction under hydrostatic tension. An auxetic nature is not observed in CsNa₂Bi, and Poisson’s ratio shows completely isotropic behavior under hydrostatic compression. A directional elastic wave velocity analysis shows that hydrostatic pressure effectively changes the propagation pattern of the elastic waves of both compounds and switches the directions of propagation. Cohesive energy, phonon dispersion, and Born–Huang conditions show that these compounds are thermodynamically, mechanically, and dynamically stable, confirming the practical feasibility of their synthesis. The identified mechanisms for controlling the auxetic and anisotropic elastic behavior of these compounds offer a vital feature for designing and developing high-performance nanoscale electromechanical devices. Full article

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13 pages, 1490 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Gold Nanorods Conjugated with Synthetic Glycopolymers Using an Analytical Approach Based on spICP-SFMS and EAF4-MALS

by Milica Velimirovic, Alessia Pancaro, Robert Mildner, Panagiotis G. Georgiou, Kristof Tirez, Inge Nelissen, Christoph Johann, Matthew I. Gibson and Frank Vanhaecke

Nanomaterials 2021, 11(10), 2720; https://doi.org/10.3390/nano11102720 - 15 Oct 2021

Cited by 4 | Viewed by 3033

Abstract

A new comprehensive analytical approach based on single-particle inductively coupled plasma-sector field mass spectrometry (spICP-SFMS) and electrical asymmetric-flow field-flow-fractionation combined with multi-angle light scattering detection (EAF4-MALS) has been examined for the characterization of galactosamine-terminated poly(N-hydroxyethyl acrylamide)-coated gold nanorods (GNRs) in two different degrees [...] Read more.

A new comprehensive analytical approach based on single-particle inductively coupled plasma-sector field mass spectrometry (spICP-SFMS) and electrical asymmetric-flow field-flow-fractionation combined with multi-angle light scattering detection (EAF4-MALS) has been examined for the characterization of galactosamine-terminated poly(N-hydroxyethyl acrylamide)-coated gold nanorods (GNRs) in two different degrees of polymerization (DP) by tuning the feed ratio (short: DP 35; long: DP 60). spICP-SFMS provided information on the particle number concentration, size and size distribution of the GNRs, and was found to be useful as an orthogonal method for fast characterization of GNRs. Glycoconjugated GNRs were separated and characterized via EAF4-MALS in terms of their size and charge and compared to the bare GNRs. In contrast to spICP-SFMS, EAF4-MALS was also able of providing an estimate of the thickness of the glycopolymer coating on the GNRs surface. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Online Conference on Nanomaterials)

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15 pages, 1947 KiB

Open AccessEditor’s ChoiceArticle

Use of Carbon Nanoparticles to Improve Soil Fertility, Crop Growth and Nutrient Uptake by Corn (Zea mays L.)

by Fengliang Zhao, Xiaoping Xin, Yune Cao, Dan Su, Puhui Ji, Zhiqiang Zhu and Zhenli He

Nanomaterials 2021, 11(10), 2717; https://doi.org/10.3390/nano11102717 - 14 Oct 2021

Cited by 101 | Viewed by 5212

Abstract

The use of carbon nanoparticles (CNPs) as a fertilizer synergist to enhance crop growth has attracted increasing interest. However, current understanding about plant growth and soil response to CNPs is limited. In the present study, we investigated the effects of CNPs at different [...] Read more.

The use of carbon nanoparticles (CNPs) as a fertilizer synergist to enhance crop growth has attracted increasing interest. However, current understanding about plant growth and soil response to CNPs is limited. In the present study, we investigated the effects of CNPs at different application rates on soil properties, the plant growth and nutrient use efficiency (NUE) of corn (Zea mays L.) in two agricultural soils (Spodosol and Alfisol). The results showed that CNPs affected corn growth in a dose-dependent manner, augmenting and retarding growth at low and at high concentrations, respectively. The amendment at the optimal rate of 200 mg CNPs kg⁻¹ significantly enhanced corn growth as indicated by improved plant height, biomass yield, nutrient uptake and nutrient use efficiency, which could be explained by the higher availability of phosphorus and nitrogen in the amended soils. The application of CNPs largely stimulated soil urease activity irrespectively of soil types. However, the responses of dehydrogenase and phosphatase to CNPs were dose dependent; their activity significantly increased with the increasing application rates of CNPs up to 200 mg kg⁻¹ but declined at higher rates (>400 mg kg⁻¹). These findings have important implications in the field application of CNPs for enhancing nutrient use efficiency and crop production in tropical/subtropical regions. Full article

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16 pages, 5503 KiB

Open AccessEditor’s ChoiceArticle

Mesoporous Zn/MgO Hexagonal Nano-Plates as a Catalyst for Camelina Oil Biodiesel Synthesis

by Lai-Fan Man, Tsz-Lung Kwong, Wing-Tak Wong and Ka-Fu Yung

Nanomaterials 2021, 11(10), 2690; https://doi.org/10.3390/nano11102690 - 13 Oct 2021

Cited by 6 | Viewed by 2528

Abstract

A novel mesoporous Zn/MgO hexagonal-nano-plate catalyst was synthesized by a simple template-free hydrothermal method and applied in the base-catalyzed transesterification of Camelina oil for biodiesel synthesis. The Zn/MgO catalyst calcinated at 873 K exhibited the highest catalytic activity with a yield of 88.7%. [...] Read more.

A novel mesoporous Zn/MgO hexagonal-nano-plate catalyst was synthesized by a simple template-free hydrothermal method and applied in the base-catalyzed transesterification of Camelina oil for biodiesel synthesis. The Zn/MgO catalyst calcinated at 873 K exhibited the highest catalytic activity with a yield of 88.7%. This catalytic reaction was performed using 3% w/w of the catalyst with a methanol-to-oil molar ratio of 24:1 at 393 K in 8 h. The excellent catalytic performance is possibly attributed to its favorable textural features with relatively high surface area (69.1 m² g⁻¹) and appropriate size of the mesopores (10.4 nm). In addition, the as-synthesized catalyst demonstrated a greater basic sites density than single mesoporous MgO, which might have been promoted by the addition of Zn, leading to a synergetic interaction that enhanced its catalytic activity. This catalytic system demonstrated high stability for five catalytic runs and catalytic activity with over 84% yield. Full article

(This article belongs to the Special Issue Nanotechnologies and Nanomaterials: Selected Papers from CCMR)

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11 pages, 2949 KiB

Open AccessEditor’s ChoiceArticle

Ammonium Ion Enhanced V₂O₅-WO₃/TiO₂ Catalysts for Selective Catalytic Reduction with Ammonia

by Min Seong Lee, Sun-I Kim, Bora Jeong, Jin-Woo Park, Taehyo Kim, Jung Woo Lee, Gibum Kwon and Duck Hyun Lee

Nanomaterials 2021, 11(10), 2677; https://doi.org/10.3390/nano11102677 - 12 Oct 2021

Cited by 12 | Viewed by 2943

Abstract

Selective catalytic reduction (SCR) is the most efficient NO_X removal technology, and the vanadium-based catalyst is mainly used in SCR technology. The vanadium-based catalyst showed higher NO_X removal performance in the high-temperature range but catalytic efficiency decreased at lower temperatures, following [...] Read more.

Selective catalytic reduction (SCR) is the most efficient NO_X removal technology, and the vanadium-based catalyst is mainly used in SCR technology. The vanadium-based catalyst showed higher NO_X removal performance in the high-temperature range but catalytic efficiency decreased at lower temperatures, following exposure to SO_X because of the generation of ammonium sulfate on the catalyst surface. To overcome these limitations, we coated an NH₄⁺ layer on a vanadium-based catalyst. After silane coating the V₂O₅-WO₃/TiO₂ catalyst by vapor evaporation, the silanized catalyst was heat treated under NH₃ gas. By decomposing the silane on the surface, an NH₄⁺ layer was formed on the catalyst surface through a substitution reaction. We observed high NO_X removal efficiency over a wide temperature range by coating an NH₄⁺ layer on a vanadium-based catalyst. This layer shows high proton conductivity, which leads to the reduction of vanadium oxides and tungsten oxide; additionally, the NO_X removal performance was improved over a wide temperature range. These findings provide a new mothed to develop SCR catalyst with high efficiency at a wide temperature range. Full article

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

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16 pages, 1985 KiB

Open AccessEditor’s ChoiceArticle

New Insights into the Reactivity of Detonation Nanodiamonds during the First Stages of Graphitization

by Florent Ducrozet, Hugues A. Girard, Jocelyne Leroy, Eric Larquet, Ileana Florea, Emilie Brun, Cécile Sicard-Roselli and Jean-Charles Arnault

Nanomaterials 2021, 11(10), 2671; https://doi.org/10.3390/nano11102671 - 11 Oct 2021

Cited by 9 | Viewed by 2671

Abstract

The present study aims to compare the early stages of graphitization of the same DND source for two annealing atmospheres (primary vacuum, argon at atmospheric pressure) in an identical set-up. DND samples are finely characterized by a combination of complementary techniques (FTIR, Raman, [...] Read more.

The present study aims to compare the early stages of graphitization of the same DND source for two annealing atmospheres (primary vacuum, argon at atmospheric pressure) in an identical set-up. DND samples are finely characterized by a combination of complementary techniques (FTIR, Raman, XPS, HR-TEM) to highlight the induced modifications for temperature up to 1100 °C. The annealing atmosphere has a significant impact on the graphitization kinetics with a higher fraction of sp²-C formed under vacuum compared to argon for the same temperature. Whatever the annealing atmosphere, carbon hydrogen bonds are created at the DND surface during annealing according to FTIR. A “nano effect”, specific to the <10 nm size of DND, exalts the extreme surface chemistry in XPS analysis. According to HR-TEM images, the graphitization is limited to the first outer shell even for DND annealed at 1100 °C under vacuum. Full article

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11 pages, 3510 KiB

Open AccessEditor’s ChoiceArticle

Physical Surface Modification of Carbon-Nanotube/Polydimethylsiloxane Composite Electrodes for High-Sensitivity DNA Detection

by Junga Moon, Huaide Jiang and Eun-Cheol Lee

Nanomaterials 2021, 11(10), 2661; https://doi.org/10.3390/nano11102661 - 10 Oct 2021

Cited by 7 | Viewed by 2724

Abstract

The chemical modification of electrode surfaces has attracted significant attention for lowering the limit of detection or for improving the recognition of biomolecules; however, the chemical processes are complex, dangerous, and difficult to control. Therefore, instead of the chemical process, we physically modified [...] Read more.

The chemical modification of electrode surfaces has attracted significant attention for lowering the limit of detection or for improving the recognition of biomolecules; however, the chemical processes are complex, dangerous, and difficult to control. Therefore, instead of the chemical process, we physically modified the surface of carbon-nanotube/polydimethylsiloxane composite electrodes by dip coating them with functionalized multi-walled carbon nanotubes (F-MWCNTs). These electrodes are used as working electrodes in electrochemistry, where they act as a recognition layer for sequence-specific DNA sensing through π–π interactions. The F-MWCNT-modified electrodes showed a limit of detection of 19.9 fM, which was 1250 times lower than that of pristine carbon/polydimethylsiloxane electrodes in a previous study, with a broad linear range of 1–1000 pM. The physically modified electrode was very stable during the electrode regeneration process after DNA detection. Our method paves the way for utilizing physical modification to significantly lower the limit of detection of a biosensor system as an alternative to chemical processes. Full article

(This article belongs to the Special Issue Novel Structural and Functional Material Properties Enabled by Nanocomposite Design)

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26 pages, 727 KiB

Open AccessEditor’s ChoiceReview

Nanotechnology Innovations to Enhance the Therapeutic Efficacy of Quercetin

by Rúben G. R. Pinheiro, Marina Pinheiro and Ana Rute Neves

Nanomaterials 2021, 11(10), 2658; https://doi.org/10.3390/nano11102658 - 9 Oct 2021

Cited by 54 | Viewed by 5862

Abstract

Quercetin is a flavonol present in many vegetables and fruits. Generally, quercetin can be found in aglycone and glycoside forms, mainly in leaves. The absorption of this compound occurs in the large and small intestine, where it suffers glucuronidation, sulfidation, and methylation to [...] Read more.

Quercetin is a flavonol present in many vegetables and fruits. Generally, quercetin can be found in aglycone and glycoside forms, mainly in leaves. The absorption of this compound occurs in the large and small intestine, where it suffers glucuronidation, sulfidation, and methylation to improve hydrophilicity. After metabolization, which occurs mainly in the gut, it is distributed throughout the whole organism and is excreted by feces, urine, and exhalation of carbon dioxide. Despite its in vitro cytotoxicity effects, in vivo studies with animal models ensure its safety. This compound can protect against cancer, cardiovascular diseases, chronic inflammation, oxidative stress, and neurodegenerative diseases due to its radical scavenging and anti-inflammatory properties. However, its poor bioavailability dampens the potential beneficial effects of this flavonoid. In that sense, many types of nanocarriers have been developed to improve quercetin solubility, as well as to design tissue-specific delivery systems. All these studies manage to improve the bioavailability of quercetin, allowing it to increase its concentration in the desired places. Collectively, quercetin can become a promising compound if nanotechnology is employed as a tool to enhance its therapeutic efficacy. Full article

(This article belongs to the Special Issue Nanoparticles for Medical Applications: Progress in Surface Modification)

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17 pages, 6354 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Layered-Double-Hydroxides Based Noble Metal Nanoparticles Efficient Electrocatalysts

by Zexuan Zhang, Peilong Li, Xin Zhang, Cun Hu, Yuwen Li, Bin Yu, Ning Zeng, Chao Lv, Jiangfeng Song and Mingcan Li

Nanomaterials 2021, 11(10), 2644; https://doi.org/10.3390/nano11102644 - 8 Oct 2021

Cited by 27 | Viewed by 4838

Abstract

With the energy crisis and environmental pollution becoming more and more serious, it is urgent to develop renewable and clean energy. Hydrogen production from electrolyzed water is of great significance to solve the energy crisis and environmental problems in the future. Recently, layered [...] Read more.

With the energy crisis and environmental pollution becoming more and more serious, it is urgent to develop renewable and clean energy. Hydrogen production from electrolyzed water is of great significance to solve the energy crisis and environmental problems in the future. Recently, layered double hydroxides (LDHs) materials have been widely studied in the electrocatalysis field, due to their unique layered structure, tunable metal species and highly dispersed active sites. Moreover, the LDHs supporting noble metal catalysts obtained through the topotactic transformation of LDHs precursors significantly reduce the energy barrier of electrolyzing water, showing remarkable catalytic activity, good conductivity and excellent durability. In this review, we give an overview of recent advances on LDHs supporting noble metal catalysts, from a brief introduction, to their preparation and modification methods, to an overview of their application in the electrocatalysis field, as well as the challenges and outlooks in this promising field on the basis of current development. Full article

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47 pages, 3065 KiB

Open AccessEditor’s ChoiceReview

Advances in Non-Animal Testing Approaches towards Accelerated Clinical Translation of Novel Nanotheranostic Therapeutics for Central Nervous System Disorders

by Mark J. Lynch and Oliviero L. Gobbo

Nanomaterials 2021, 11(10), 2632; https://doi.org/10.3390/nano11102632 - 7 Oct 2021

Cited by 12 | Viewed by 4812

Abstract

Nanotheranostics constitute a novel drug delivery system approach to improving systemic, brain-targeted delivery of diagnostic imaging agents and pharmacological moieties in one rational carrier platform. While there have been notable successes in this field, currently, the clinical translation of such delivery systems for [...] Read more.

Nanotheranostics constitute a novel drug delivery system approach to improving systemic, brain-targeted delivery of diagnostic imaging agents and pharmacological moieties in one rational carrier platform. While there have been notable successes in this field, currently, the clinical translation of such delivery systems for the treatment of neurological disorders has been limited by the inadequacy of correlating in vitro and in vivo data on blood–brain barrier (BBB) permeation and biocompatibility of nanomaterials. This review aims to identify the most contemporary non-invasive approaches for BBB crossing using nanotheranostics as a novel drug delivery strategy and current non-animal-based models for assessing the safety and efficiency of such formulations. This review will also address current and future directions of select in vitro models for reducing the cumbersome and laborious mandate for testing exclusively in animals. It is hoped these non-animal-based modelling approaches will facilitate researchers in optimising promising multifunctional nanocarriers with a view to accelerating clinical testing and authorisation applications. By rational design and appropriate selection of characterised and validated models, ranging from monolayer cell cultures to organ-on-chip microfluidics, promising nanotheranostic particles with modular and rational design can be screened in high-throughput models with robust predictive power. Thus, this article serves to highlight abbreviated research and development possibilities with clinical translational relevance for developing novel nanomaterial-based neuropharmaceuticals for therapy in CNS disorders. By generating predictive data for prospective nanomedicines using validated in vitro models for supporting clinical applications in lieu of requiring extensive use of in vivo animal models that have notable limitations, it is hoped that there will be a burgeoning in the nanotherapy of CNS disorders by virtue of accelerated lead identification through screening, optimisation through rational design for brain-targeted delivery across the BBB and clinical testing and approval using fewer animals. Additionally, by using models with tissue of human origin, reproducible therapeutically relevant nanomedicine delivery and individualised therapy can be realised. Full article

(This article belongs to the Special Issue Nanobiotechnology for Drug Delivery System)

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20 pages, 3969 KiB

Open AccessEditor’s ChoiceArticle

Ingested Engineered Nanomaterials Affect the Expression of Mucin Genes—An In Vitro-In Vivo Comparison

by Gerrit Bredeck, Angela A. M. Kämpfer, Adriana Sofranko, Tina Wahle, Veronika Büttner, Catrin Albrecht and Roel P. F. Schins

Nanomaterials 2021, 11(10), 2621; https://doi.org/10.3390/nano11102621 - 6 Oct 2021

Cited by 5 | Viewed by 3086

Abstract

The increasing use of engineered nanomaterials (ENM) in food has fueled the development of intestinal in vitro models for toxicity testing. However, ENM effects on intestinal mucus have barely been addressed, although its crucial role for intestinal health is evident. We investigated the [...] Read more.

The increasing use of engineered nanomaterials (ENM) in food has fueled the development of intestinal in vitro models for toxicity testing. However, ENM effects on intestinal mucus have barely been addressed, although its crucial role for intestinal health is evident. We investigated the effects of ENM on mucin expression and aimed to evaluate the suitability of four in vitro models of increasing complexity compared to a mouse model exposed through feed pellets. We assessed the gene expression of the mucins MUC1, MUC2, MUC5AC, MUC13 and MUC20 and the chemokine interleukin-8 in pre-confluent and confluent HT29-MTX-E12 cells, in stable and inflamed triple cultures of Caco-2, HT29-MTX-E12 and THP-1 cells, and in the ileum of mice following exposure to TiO₂, Ag, CeO₂ or SiO₂. All ENM had shared and specific effects. CeO₂ downregulated MUC1 in confluent E12 cells and in mice. Ag induced downregulation of Muc2 in mice. Overall, the in vivo data were consistent with the findings in the stable triple cultures and the confluent HT29-MTX-E12 cells but not in pre-confluent cells, indicating the higher relevance of advanced models for hazard assessment. The effects on MUC1 and MUC2 suggest that specific ENM may lead to an elevated susceptibility towards intestinal infections and inflammations. Full article

(This article belongs to the Special Issue Advances in Toxicity of Nanoparticles)

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18 pages, 7082 KiB

Open AccessEditor’s ChoiceArticle

Highly Efficient and Controllable Methodology of the Cd_0.25Zn_0.75Se/ZnS Core/Shell Quantum Dots Synthesis

by Liudmila Loghina, Maksym Chylii, Anastasia Kaderavkova, Stanislav Slang, Petr Svec, Jhonatan Rodriguez Pereira, Bozena Frumarova, Miroslav Cieslar and Miroslav Vlcek

Nanomaterials 2021, 11(10), 2616; https://doi.org/10.3390/nano11102616 - 5 Oct 2021

Cited by 5 | Viewed by 2361

Abstract

The surface of any binary or multi-component nanocrystal has imperfections and defects. The number of surface defects depends both on the nature of the nanomaterial and on the method of its preparation. One of the possibilities to confine the number of surface defects [...] Read more.

The surface of any binary or multi-component nanocrystal has imperfections and defects. The number of surface defects depends both on the nature of the nanomaterial and on the method of its preparation. One of the possibilities to confine the number of surface defects is the epitaxial growth of the shell, which leads to a change in the physical properties while maintaining the morphology of the core. To form a shell of the desired thickness, an accurate calculation of the amount of its precursors is substantial to avoid the appearance of individual crystals consisting of the shell material. This study aimed to develop an effective calculation method for the theoretical amount of precursors required for the formation of a ZnS shell on the surface of a Cd_0.25Zn_0.75Se core, followed by the practical implementation of theoretical calculations and characterization of the prepared nanomaterials. This method allows the complete control of the masses and volumes of the initial reagents, which will in turn prevent undesirable nucleation of nuclei consisting of the shell material. In the synthesis of Cd_0.25Zn_0.75Se/ZnS core/shell quantum dots (QDs), the sources of chalcogens were substituted seleno- and thioureas, which are capable of not only supplanting modern toxic sources of sulfur and selenium but also allowing one to perform the controlled synthesis of highly photoluminescent QDs with a low number of surface defects. The result of this shell overcoating method was an impetuous augmentation in the photoluminescence quantum yield (PL QY up to 83%), uniformity in size and shape, and a high yield of nanomaterials. The developed synthetic technique of core/shell QDs provides a controlled growth of the shell on the core surface, which makes it possible to transfer this method to an industrial scale. Full article

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20 pages, 5542 KiB

Open AccessEditor’s ChoiceArticle

Thermophysical Properties of NH₃/IL+ Carbon Nanomaterial Solutions

by Gabriela Huminic and Angel Huminic

Nanomaterials 2021, 11(10), 2612; https://doi.org/10.3390/nano11102612 - 4 Oct 2021

Cited by 2 | Viewed by 1847

Abstract

This study proposes the use of new working fluids, refrigerant/IL+ carbon nanomaterials (CNMs), in absorption systems as an alternative to conventional working fluids. In this regard, the thermophysical properties of ammonia and carbon nanomaterials (graphene and single-wall carbon nanotubes) dispersed into [B_MIM [...] Read more.

This study proposes the use of new working fluids, refrigerant/IL+ carbon nanomaterials (CNMs), in absorption systems as an alternative to conventional working fluids. In this regard, the thermophysical properties of ammonia and carbon nanomaterials (graphene and single-wall carbon nanotubes) dispersed into [B_MIM]BF₄ ionic liquid are theoretically investigated. The thermophysical properties of NH₃/IL+ CNMs solutions are computed for weight fractions of NH₃ in the range of 0.018–0.404 and temperatures between 293 and 388 K. In addition, two weight fractions of CNMs are considered: 0.005 and 0.01, respectively. Our results indicate that by adding a small amount of nanomaterial to the ionic liquid, the solution’s thermal conductivity is enhanced, while its viscosity and specific heat are reduced. Correlations of the thermal conductivity, viscosity, specific heat, and density of the NH₃/IL+ CNMs solutions are proposed. Full article

(This article belongs to the Special Issue Thermophysical Properties of Nanocolloids and Their Potential Applications)

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15 pages, 2602 KiB

Open AccessEditor’s ChoiceArticle

Facile and Sensitive Detection of Nitrogen-Containing Organic Bases with Near Infrared C-Dots Derived Assays

by Chunyu Ji, Yiqun Zhou, Wenquan Shi, Jiajia Wu, Qiurui Han, Tianshu Zhao, Roger M. Leblanc and Zhili Peng

Nanomaterials 2021, 11(10), 2607; https://doi.org/10.3390/nano11102607 - 3 Oct 2021

Cited by 10 | Viewed by 2681

Abstract

In this article, we have designed both colorimetric (including solution and test paper type) and spectral sensors (including UV-vis and PL type) for the quick and sensitive detection of general nitrogen-containing organic bases (NCOBs); the limit of detection could reach as low as [...] Read more.

In this article, we have designed both colorimetric (including solution and test paper type) and spectral sensors (including UV-vis and PL type) for the quick and sensitive detection of general nitrogen-containing organic bases (NCOBs); the limit of detection could reach as low as 0.50 nM. NCOBs included 11 examples, covering aliphatic and aromatic amines, five- and six-membered heterocyclics, fused-ring heterocyclics, amino acids, and antibiotics. Furthermore, the assays demonstrated high reliability in sensing NCOBs and excellent ability to distinguish NCOBs from oxygen and sulfur containing organics. The assays developed could find important applications for the detection of NCOBs in the fields of biomedicine, chemistry, and agriculture. Full article

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

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21 pages, 7068 KiB

Open AccessEditor’s ChoiceArticle

How to Make a Cocktail of Palladium Catalysts with Cola and Alcohol: Heteroatom Doping vs. Nanoscale Morphology of Carbon Supports

by Evgeniy O. Pentsak, Alexey S. Galushko, Vera A. Cherepanova and Valentine P. Ananikov

Nanomaterials 2021, 11(10), 2599; https://doi.org/10.3390/nano11102599 - 2 Oct 2021

Cited by 10 | Viewed by 3445

Abstract

Sparkling drinks such as cola can be considered an affordable and inexpensive starting material consisting of carbohydrates and sulfur- and nitrogen-containing organic substances in phosphoric acid, which makes them an excellent precursor for the production of heteroatom-doped carbon materials. In this study, heteroatom-doped [...] Read more.

Sparkling drinks such as cola can be considered an affordable and inexpensive starting material consisting of carbohydrates and sulfur- and nitrogen-containing organic substances in phosphoric acid, which makes them an excellent precursor for the production of heteroatom-doped carbon materials. In this study, heteroatom-doped carbon materials were successfully prepared in a quick and simple manner using direct carbonization of regular cola and diet cola. The low content of carbon in diet cola allowed reaching a higher level of phosphorus in the prepared carbon material, as well as obtaining additional doping with nitrogen and sulfur due to the presence of sweeteners and caffeine. Effects of carbon support doping with phosphorus, nitrogen and sulfur, as well as of changes in textural properties by ball milling, on the catalytic activity of palladium catalysts were investigated in the Suzuki–Miyaura and Mizoroki–Heck reactions. Contributions of the heteroatom doping and specific surface area of the carbon supports to the increased activity of supported catalysts were discussed. Additionally, the possibility of these reactions to proceed in 40% potable ethanol was studied. Moreover, transformation of various palladium particles (complexes and nanoparticles) in the reaction medium was detected by mass spectrometry and transmission electron microscopy, which evidenced the formation of a cocktail of catalysts in a commercial 40% ethanol/water solution. Full article

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23 pages, 4062 KiB

Open AccessEditor’s ChoiceArticle

Revealing the Effect of Synthesis Conditions on the Structural, Optical, and Antibacterial Properties of Cerium Oxide Nanoparticles

by Nicusor Fifere, Anton Airinei, Marius Dobromir, Liviu Sacarescu and Simona I. Dunca

Nanomaterials 2021, 11(10), 2596; https://doi.org/10.3390/nano11102596 - 1 Oct 2021

Cited by 39 | Viewed by 3702

Abstract

Cerium oxide nanoparticles were prepared by a precipitation method using Ce(IV) sulphate as precursor dispersed in glycerol with varying synthesis parameters such as temperature or precipitating agent. The structural and morphological characteristics of the obtained nanoparticles were investigated by X-ray diffraction, transmission electron [...] Read more.

Cerium oxide nanoparticles were prepared by a precipitation method using Ce(IV) sulphate as precursor dispersed in glycerol with varying synthesis parameters such as temperature or precipitating agent. The structural and morphological characteristics of the obtained nanoparticles were investigated by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy. The crystallite size of the nanoparticles varied between 13 and 17 nm. The presence of Ce³⁺ and Ce⁴⁺ was proved by XPS data in the CeO₂ samples and the conservation of the fluorite structure was evinced by X-ray diffractograms with a contraction of the lattice parameter, regardless of the size of the nanoparticle. From diffuse reflectance spectra, two band gap energy values for the direct transition were observed. Depending on the synthesis condition, the red shift of gap energy and the blue shift of Urbach energy with increasing content of Ce³⁺ were ascertained. The antibacterial tests revealed that the cerium oxide nanoparticles show good antimicrobial activity towards the common pathogens Escherichia coli and Staphylococcus aureus. Full article

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22 pages, 4205 KiB

Open AccessEditor’s ChoiceArticle

Facile In Situ Synthesis of ZnO Flower-like Hierarchical Nanostructures by the Microwave Irradiation Method for Multifunctional Textile Coatings

by Maria Antonia Tănase, Andreia Cristina Soare, Petruţa Oancea, Adina Răducan, Cătălin Ionuţ Mihăescu, Elvira Alexandrescu, Cristian Petcu, Lia Mara Diţu, Marilena Ferbinteanu, Bogdan Cojocaru and Ludmila Otilia Cinteza

Nanomaterials 2021, 11(10), 2574; https://doi.org/10.3390/nano11102574 - 30 Sep 2021

Cited by 19 | Viewed by 3801

Abstract

ZnO nanoparticle-based multifunctional coatings were prepared by a simple, time-saving microwave method. Arginine and ammonia were used as precipitation agents, and zinc acetate dehydrate was used as a zinc precursor. Under the optimized conditions, flower-like morphologies of ZnO aggregates were obtained. The prepared [...] Read more.

ZnO nanoparticle-based multifunctional coatings were prepared by a simple, time-saving microwave method. Arginine and ammonia were used as precipitation agents, and zinc acetate dehydrate was used as a zinc precursor. Under the optimized conditions, flower-like morphologies of ZnO aggregates were obtained. The prepared nanopowders were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and UV/Visible spectroscopy. The developed in situ synthesis with microwave irradiation enabled significant ZnO nanoparticle deposition on cotton fabrics, without additional steps. The functionalized textiles were tested as a photocatalyst in methylene blue (MB) photodegradation and showed good self-cleaning and UV-blocking properties. The coated cotton fabrics exhibited good antibacterial properties against common microbial trains (Staphylococcus aureus, Escherichia coli, and Candida albicans), together with self-cleaning and photocatalytic efficiency in organic dye degradation. The proposed microwave-assisted in situ synthesis of ZnO nanocoatings on textiles shows high potential as a rapid, efficient, environmentally friendly, and scalable method to fabricate functional fabrics. Full article

(This article belongs to the Special Issue Microwave Technology and Nanomaterials: Synthesis and Application)

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16 pages, 5974 KiB

Open AccessEditor’s ChoiceArticle

Monolayer-Scale GaN/AlN Multiple Quantum Wells for High Power e-Beam Pumped UV-Emitters in the 240–270 nm Spectral Range

by Valentin Jmerik, Dmitrii Nechaev, Kseniya Orekhova, Nikita Prasolov, Vladimir Kozlovsky, Dmitry Sviridov, Mikhail Zverev, Nikita Gamov, Lars Grieger, Yixin Wang, Tao Wang, Xinqiang Wang and Sergey Ivanov

Nanomaterials 2021, 11(10), 2553; https://doi.org/10.3390/nano11102553 - 29 Sep 2021

Cited by 14 | Viewed by 3432

Abstract

Monolayer (ML)-scale GaN/AlN multiple quantum well (MQW) structures for electron-beam-pumped ultraviolet (UV) emitters are grown on c-sapphire substrates by using plasma-assisted molecular beam epitaxy under controllable metal-rich conditions, which provides the spiral growth of densely packed atomically smooth hillocks without metal droplets. [...] Read more.

Monolayer (ML)-scale GaN/AlN multiple quantum well (MQW) structures for electron-beam-pumped ultraviolet (UV) emitters are grown on c-sapphire substrates by using plasma-assisted molecular beam epitaxy under controllable metal-rich conditions, which provides the spiral growth of densely packed atomically smooth hillocks without metal droplets. These structures have ML-stepped terrace-like surface topology in the entire QW thickness range from 0.75–7 ML and absence of stress at the well thickness below 2 ML. Satisfactory quantum confinement and mitigating the quantum-confined Stark effect in the stress-free MQW structures enable one to achieve the relatively bright UV cathodoluminescence with a narrow-line (~15 nm) in the sub-250-nm spectral range. The structures with many QWs (up to 400) exhibit the output optical power of ~1 W at 240 nm, when pumped by a standard thermionic-cathode (LaB₆) electron gun at an electron energy of 20 keV and a current of 65 mA. This power is increased up to 11.8 W at an average excitation energy of 5 µJ per pulse, generated by the electron gun with a ferroelectric plasma cathode at an electron-beam energy of 12.5 keV and a current of 450 mA. Full article

(This article belongs to the Special Issue Semiconductor Heterostructures (with Quantum Wells, Quantum Dots and Superlattices))

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15 pages, 2334 KiB

Open AccessEditor’s ChoiceArticle

Evaporation of Methylammonium Iodide in Thermal Deposition of MAPbI₃

by Ke Wang, Benjamin Ecker, Jinsong Huang and Yongli Gao

Nanomaterials 2021, 11(10), 2532; https://doi.org/10.3390/nano11102532 - 28 Sep 2021

Cited by 9 | Viewed by 3586

Abstract

Thermal evaporation is an important technique for fabricating methylammonium lead iodide (MAPbI₃), but the process is complicated by the need to co-evaporate methylammonium iodide (MAI) and PbI₂. In this work, the effect of water vapor during the thermal deposition [...] Read more.

Thermal evaporation is an important technique for fabricating methylammonium lead iodide (MAPbI₃), but the process is complicated by the need to co-evaporate methylammonium iodide (MAI) and PbI₂. In this work, the effect of water vapor during the thermal deposition of MAPbI₃ was investigated under high vacuum. The evaporation process was monitored with a residual gas analyzer (RGA), and the film quality was examined with X-ray photoelectron spectroscopy (XPS). The investigations showed that during evaporation, MAI decomposed while PbI₂ evaporated as a whole compound. It was found that the residual water vapor reacted with one of the MAI-dissociated products. The higher iodine ratio suggests that the real MAI flux was higher than the reading from the QCM. The XPS analysis demonstrated that the residual water vapor may alter the elemental ratios of C, N, and I in thermally deposited MAPbI₃. Morphologic properties were investigated with atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). It was observed that a sample grown with high water vapor pressure had a roughened surface and poor film quality. Therefore, an evaporation environment with water vapor pressure below 10⁻⁸ Torr is needed to fabricate high quality perovskite films. Full article

(This article belongs to the Special Issue Hybrid Perovskite Thin Film)

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11 pages, 12378 KiB

Open AccessEditor’s ChoiceArticle

Hydroxyapatite Particles from Simulated Body Fluids with Different pH and Their Effects on Mesenchymal Stem Cells

by Hiroki Miyajima, Hiroki Touji and Kazutoshi Iijima

Nanomaterials 2021, 11(10), 2517; https://doi.org/10.3390/nano11102517 - 27 Sep 2021

Cited by 21 | Viewed by 3517

Abstract

Bone-like hydroxyapatite (HAp) has been prepared by biomimetic synthesis using simulated body fluid (SBF), mimicking inorganic ion concentrations in human plasma, or 1.5SBF that has 1.5-times higher ion concentrations than SBF. In this study, the controllable preparations of HAp particles from 1.5SBF with [...] Read more.

Bone-like hydroxyapatite (HAp) has been prepared by biomimetic synthesis using simulated body fluid (SBF), mimicking inorganic ion concentrations in human plasma, or 1.5SBF that has 1.5-times higher ion concentrations than SBF. In this study, the controllable preparations of HAp particles from 1.5SBF with different pH values were examined. The particles obtained as precipitates from 1.5SBF showed different morphologies and crystallinities depending on the pH of 1.5SBF. Micro-sized particles at pH 7.4 of 1.5SBF had a higher Ca/P ratio and crystallinity as compared with nano-sized particles at pH 8.0 and pH 8.4 of 1.5SBF. However, a mixture of micro-sized and nano-sized particles was obtained from pH 7.7 of 1.5SBF. When Ca²⁺ concentrations in 1.5SBF during mineralization were monitored, the concentration at pH 7.4 drastically decreased from 12 to 24 h. At higher pH, such as 8.0 and 8.4, the Ca²⁺ concentrations decreased during pH adjustment and slightly decreased even after 48 h. In this investigation at pH 7.7, the Ca²⁺ concentrations were higher than pH 8.0 and 8.4.Additionally, cytotoxicity of the obtained precipitates to mesenchymal stem cells was lower than that of synthetic HAp. Controllable preparation HAp particles from SBF has potential applications in the construction of building components of cell scaffolds. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Biomedical Applications of Nanomaterials)

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17 pages, 6491 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Electronic Transport Mechanisms Correlated to Structural Properties of a Reduced Graphene Oxide Sponge

by Nicola Pinto, Benjamin McNaughton, Marco Minicucci, Milorad V. Milošević and Andrea Perali

Nanomaterials 2021, 11(10), 2503; https://doi.org/10.3390/nano11102503 - 26 Sep 2021

Cited by 1 | Viewed by 2748

Abstract

We report morpho-structural properties and charge conduction mechanisms of a foamy “graphene sponge”, having a density as low as ≈0.07 kg/m

^{3}

and a carbon to oxygen ratio C:O ≃ 13:1. The spongy texture analysed by scanning electron microscopy is made of irregularly-shaped [...] Read more.

We report morpho-structural properties and charge conduction mechanisms of a foamy “graphene sponge”, having a density as low as ≈0.07 kg/m

^{3}

and a carbon to oxygen ratio C:O ≃ 13:1. The spongy texture analysed by scanning electron microscopy is made of irregularly-shaped millimetres-sized small flakes, containing small crystallites with a typical size of ≃16.3 nm. A defect density as high as ≃2.6 × 10

^{11}

cm

^{- 2}

has been estimated by the Raman intensity of D and G peaks, dominating the spectrum from room temperature down to ≃153 K. Despite the high C:O ratio, the graphene sponge exhibits an insulating electrical behavior, with a raise of the resistance value at ≃6 K up to 5 orders of magnitude with respect to the room temperature value. A variable range hopping (VRH) conduction, with a strong 2D character, dominates the charge carriers transport, from 300 K down to 20 K. At T < 20 K, graphene sponge resistance tends to saturate, suggesting a temperature-independent quantum tunnelling. The 2D-VRH conduction originates from structural disorder and is consistent with hopping of charge carriers between

s p^{2}

defects in the plane, where

s p^{3}

clusters related to oxygen functional groups act as potential barriers. Full article

(This article belongs to the Special Issue Carbon-Based Materials: Growth, Characterization, and Applications)

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20 pages, 10527 KiB

Open AccessEditor’s ChoiceArticle

Flower-Like Dual-Defective Z-Scheme Heterojunction g-C₃N₄/ZnIn₂S₄ High-Efficiency Photocatalytic Hydrogen Evolution and Degradation of Mixed Pollutants

by Linlin Hou, Zhiliang Wu, Chun Jin, Wei Li, Qiuming Wei, Yasi Chen and Teng Wang

Nanomaterials 2021, 11(10), 2483; https://doi.org/10.3390/nano11102483 - 24 Sep 2021

Cited by 20 | Viewed by 3922

Abstract

Graphitic carbon nitride (g-C₃N₄) with a porous nano-structure, nitrogen vacancies, and oxygen-doping was prepared by the calcination method. Then, it was combined with ZnIn₂S₄ nanosheets containing zinc vacancies to construct a three-dimensional (3D) flower-like Z-scheme heterojunction [...] Read more.

Graphitic carbon nitride (g-C₃N₄) with a porous nano-structure, nitrogen vacancies, and oxygen-doping was prepared by the calcination method. Then, it was combined with ZnIn₂S₄ nanosheets containing zinc vacancies to construct a three-dimensional (3D) flower-like Z-scheme heterojunction (pCN-N/ZIS-Z), which was used for photocatalytic hydrogen evolution and the degradation of mixed pollutants. The constructed Z-scheme heterojunction improved the efficiency of photogenerated charges separation and migration, and the large surface area and porous characteristics provided more active sites. Doping and defect engineering can change the bandgap structure to improve the utilization of visible light, and can also capture photogenerated electrons to inhibit recombination, so as to promote the use of photogenerated electron-hole pairs in the photocatalytic redox process. Heterojunction and defect engineering synergized to form a continuous and efficient conductive operation framework, which achieves the hydrogen production of pCN-N/ZIS-Z (9189.8 µmol·h⁻¹·g⁻¹) at 58.9 times that of g-C₃N₄ (155.9 µmol·h⁻¹·g⁻¹), and the degradation rates of methyl orange and metronidazole in the mixed solution were 98.7% and 92.5%, respectively. Our research provides potential ideas for constructing a green and environmentally friendly Z-scheme heterojunction catalyst based on defect engineering to address the energy crisis and environmental restoration. Full article

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11 pages, 3656 KiB

Open AccessEditor’s ChoiceArticle

Molecular Junctions Enhancing Thermal Transport within Graphene Polymer Nanocomposite: A Molecular Dynamics Study

by Alessandro Di Pierro, Bohayra Mortazavi and Alberto Fina

Nanomaterials 2021, 11(10), 2480; https://doi.org/10.3390/nano11102480 - 23 Sep 2021

Cited by 3 | Viewed by 2783

Abstract

Thermal conductivity of polymer-based (nano)composites is typically limited by thermal resistances occurring at the interfaces between the polymer matrix and the conductive particles as well as between particles themselves. In this work, the adoption of molecular junctions between thermally conductive graphene foils is [...] Read more.

Thermal conductivity of polymer-based (nano)composites is typically limited by thermal resistances occurring at the interfaces between the polymer matrix and the conductive particles as well as between particles themselves. In this work, the adoption of molecular junctions between thermally conductive graphene foils is addressed, aiming at the reduction of the thermal boundary resistance and eventually lead to an efficient percolation network within the polymer nanocomposite. This system was computationally investigated at the atomistic scale, using classical Molecular Dynamics, applied the first time to the investigation of heat transfer trough molecular junctions within a realistic environment for a polymer nanocomposite. A series of Molecular Dynamics simulations were conducted to investigate the thermal transport efficiency of molecular junctions in polymer tight contact, to quantify the contribution of molecular junctions when graphene and the molecular junctions are surrounded by polydimethylsiloxane (PDMS) molecules. A strong dependence of the thermal conductance was found in PDMS/graphene model, with best performances obtained with short and conformationally rigid molecular junctions. Furthermore, the adoption of the molecular linkers was found to contribute additionally to the thermal transport provided by the surrounding polymer matrix, demonstrating the possibility of exploiting molecular junctions in composite materials. Full article

(This article belongs to the Special Issue Thermal Transport in Nanoscale)

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10 pages, 1965 KiB

Open AccessEditor’s ChoiceArticle

Effects of Nanoplastics on the Dinoflagellate Amphidinium carterae Hulburt from the Perspectives of Algal Growth, Oxidative Stress and Hemolysin Production

by Su-Chun Wang, Fei-Fei Liu, Tian-Yuan Huang, Jin-Lin Fan, Zhi-Yin Gao and Guang-Zhou Liu

Nanomaterials 2021, 11(10), 2471; https://doi.org/10.3390/nano11102471 - 22 Sep 2021

Cited by 17 | Viewed by 3490

Abstract

Recently, the effects of nanoplastics (NPs) on aquatic organisms have attracted much attention; however, research on the toxicity of NPs to microalgae has been insufficient. In the present study, the effects of polystyrene nanoplastics (nano-PS, 50 nm) on growth inhibition, chlorophyll content, oxidative [...] Read more.

Recently, the effects of nanoplastics (NPs) on aquatic organisms have attracted much attention; however, research on the toxicity of NPs to microalgae has been insufficient. In the present study, the effects of polystyrene nanoplastics (nano-PS, 50 nm) on growth inhibition, chlorophyll content, oxidative stress, and algal toxin production of the marine toxigenic dinoflagellate Amphidinium carterae Hulburt were investigated. Chlorophyll synthesis was promoted by nano-PS on day 2 but was inhibited on day 4; high concentrations of nano-PS (≥50 mg/L) significantly inhibited the growth of A. carterae. Moreover, despite the combined effect of superoxide dismutase (SOD) and glutathione (GSH), high reactive oxygen species (ROS) level and malondialdehyde (MDA) content were still induced by nano-PS (≥50 mg/L), indicating severe lipid peroxidation. In addition, the contents of extracellular and intracellular hemolytic toxins in nano-PS groups were significantly higher than those in control groups on days 2 and 8, except that those of extracellular hemolytic toxins in the 100 mg/L nano-PS group decreased on day 8 because of severe adsorption of hemolytic toxins to the nano-PS. Hence, the effects of nano-PS on A. carterae are closely linked to nano-PS concentration and surface properties and exposure time. These findings provide a deep understanding of the complex effects of NPs on toxigenic microalgae and present valuable data for assessing their environmental risks. Full article

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

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22 pages, 13774 KiB

Open AccessEditor’s ChoiceReview

Current Knowledge of Silver and Gold Nanoparticles in Laboratory Research—Application, Toxicity, Cellular Uptake

by Patrycja Talarska, Maciej Boruczkowski and Jakub Żurawski

Nanomaterials 2021, 11(9), 2454; https://doi.org/10.3390/nano11092454 - 21 Sep 2021

Cited by 78 | Viewed by 6272

Abstract

Silver and gold nanoparticles can be found in a range of household products related to almost every area of life, including patches, bandages, paints, sportswear, personal care products, food storage equipment, cosmetics, disinfectants, etc. Their confirmed ability to enter the organism through respiratory [...] Read more.

Silver and gold nanoparticles can be found in a range of household products related to almost every area of life, including patches, bandages, paints, sportswear, personal care products, food storage equipment, cosmetics, disinfectants, etc. Their confirmed ability to enter the organism through respiratory and digestive systems, skin, and crossing the blood–brain barrier raises questions of their potential effect on cell function. Therefore, this manuscript aimed to summarize recent reports concerning the influence of variables such as size, shape, concentration, type of coating, or incubation time, on effects of gold and silver nanoparticles on cultured cell lines. Due to the increasingly common use of AgNP and AuNP in multiple branches of the industry, further studies on the effects of nanoparticles on different types of cells and the general natural environment are needed to enable their long-term use. However, some environmentally friendly solutions to chemically synthesized nanoparticles are also investigated, such as plant-based synthesis methods. Full article

(This article belongs to the Special Issue Cytotoxicity and Genotoxicity of Nanoparticles)

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12 pages, 2302 KiB

Open AccessEditor’s ChoiceArticle

Preparation of Network-Structured Carbon Nanofiber Mats Based on PAN Blends Using Electrospinning and Hot-Pressing Methods for Supercapacitor Applications

by Min-Jung Ma, Jae-Gyoung Seong, Sivaprakasam Radhakrishnan, Tae-Hoon Ko and Byoung-Suhk Kim

Nanomaterials 2021, 11(9), 2447; https://doi.org/10.3390/nano11092447 - 20 Sep 2021

Cited by 9 | Viewed by 3261

Abstract

In this work, we prepared network-structured carbon nanofibers using polyacrylonitrile blends (PAN150 and PAN85) with different molecular weights (150,000 and 85,000 g mol⁻¹) as precursors through electrospinning/hot-pressing methods and stabilization/carbonization processes. The obtained PAN150/PAN85 polymer nanofibers (PNFs; PNF-73, PNF-64 and PNF-55) [...] Read more.

In this work, we prepared network-structured carbon nanofibers using polyacrylonitrile blends (PAN150 and PAN85) with different molecular weights (150,000 and 85,000 g mol⁻¹) as precursors through electrospinning/hot-pressing methods and stabilization/carbonization processes. The obtained PAN150/PAN85 polymer nanofibers (PNFs; PNF-73, PNF-64 and PNF-55) with different weight ratios of 70/30, 60/40 and 50/50 (w/w) provided good mechanical and electrochemical properties due to the formation of physically bonded network structures between the blended PAN nanofibers during the hot-processing/stabilization processes. The resulting carbonized PNFs (cPNFs; cPNF-73, cPNF-64, and cPNF-55) were utilized as anode materials for supercapacitor applications. cPNF-73 exhibited a good specific capacitance of 689 F g⁻¹ at 1 A g⁻¹ in a three-electrode set-up compared to cPNF-64 (588 F g⁻¹ at 1 A g⁻¹) and cPNF-55 (343 F g⁻¹ at 1 A g⁻¹). In addition, an asymmetric hybrid cPNF-73//NiCo₂O₄ supercapacitor device also showed a good specific capacitance of 428 F g⁻¹ at 1 A g⁻¹ compared to cPNF-64 (400 F g⁻¹ at 1 A g⁻¹) and cPNF-55 (315 F g⁻¹ at 1 A g⁻¹). The cPNF-73-based device showed a good energy density of 1.74 W h kg⁻¹ (0.38 W kg⁻¹) as well as an excellent cyclic stability (83%) even after 2000 continuous charge–discharge cycles at a current density of 2 A g⁻¹. Full article

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

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10 pages, 3676 KiB

Open AccessEditor’s ChoiceArticle

Fast Fabrication of Solid-State Nanopores for DNA Molecule Analysis

by Yin Zhang, Dexian Ma, Zengdao Gu, Lijian Zhan and Jingjie Sha

Nanomaterials 2021, 11(9), 2450; https://doi.org/10.3390/nano11092450 - 20 Sep 2021

Cited by 3 | Viewed by 3875

Abstract

Solid-state nanopores have been developed as a prominent tool for single molecule analysis in versatile applications. Although controlled dielectric breakdown (CDB) is the most accessible method for a single nanopore fabrication, it is still necessary to improve the fabrication efficiency and avoid the [...] Read more.

Solid-state nanopores have been developed as a prominent tool for single molecule analysis in versatile applications. Although controlled dielectric breakdown (CDB) is the most accessible method for a single nanopore fabrication, it is still necessary to improve the fabrication efficiency and avoid the generation of multiple nanopores. In this work, we treated the SiNx membranes in the air–plasma before the CDB process, which shortened the time-to-pore-formation by orders of magnitude. λ-DNA translocation experiments validated the functionality of the pore and substantiated the presence of only a single pore on the membrane. Our fabricated pore could also be successfully used to detect short single-stranded DNA (ssDNA) fragments. Using to ionic current signals, ssDNA fragments with different lengths could be clearly distinguished. These results will provide a valuable reference for the nanopore fabrication and DNA analysis. Full article

(This article belongs to the Special Issue New Trends of Bio- and Chemo- Sensors with Nanomaterials)

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9 pages, 1701 KiB

Open AccessEditor’s ChoiceArticle

Modulation of Conductivity and Contact Resistance of RuO₂ Nanosheets via Metal Nano-Particles Surface Decoration

by Jongwon Kim, Seonhye Youn, Ju Young Baek, Dong Hwan Kim, Sumin Kim, Wooyoung Lee, Hee Jung Park, Juyoung Kim, Dong Won Chun, Sang-Shik Park, Jong Wook Roh and Jeongmin Kim

Nanomaterials 2021, 11(9), 2444; https://doi.org/10.3390/nano11092444 - 19 Sep 2021

Cited by 4 | Viewed by 3379

Abstract

We studied the variation in electrical conductivity of exfoliated RuO₂ nanosheets and the modulation in the contact resistance of individual nanosheet devices using charge transfer doping effects based on surface metal nanoparticle decorations. The electrical conductivity in the monolayer and bilayer RuO [...] Read more.

We studied the variation in electrical conductivity of exfoliated RuO₂ nanosheets and the modulation in the contact resistance of individual nanosheet devices using charge transfer doping effects based on surface metal nanoparticle decorations. The electrical conductivity in the monolayer and bilayer RuO₂ nanosheets gradually increased due to the surface decoration of Cu, and subsequently Ag, nanoparticles. We obtained contact resistances between the nanosheet and electrodes using the four-point and two-point probe techniques. Moreover, the contact resistances decreased during the surface decoration processes. We established that the surface decoration of metal nanoparticles is a suitable method for external contact engineering and the modulation of the internal properties of nanomaterials. Full article

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

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20 pages, 14189 KiB

Open AccessEditor’s ChoiceArticle

Phase Behavior and Composition Distribution of Multiphase Hydrocarbon Binary Mixtures in Heterogeneous Nanopores: A Molecular Dynamics Simulation Study

by Deraldo de Carvalho Jacobina de Andrade and Bahareh Nojabaei

Nanomaterials 2021, 11(9), 2431; https://doi.org/10.3390/nano11092431 - 18 Sep 2021

Cited by 7 | Viewed by 2808

Abstract

In this study, molecular dynamics (MD) simulation is used to investigate the phase behavior and composition distribution of an ethane/heptane binary mixture in heterogeneous oil-wet graphite nanopores with pore size distribution. The pore network system consists of two different setups of connected bulk [...] Read more.

In this study, molecular dynamics (MD) simulation is used to investigate the phase behavior and composition distribution of an ethane/heptane binary mixture in heterogeneous oil-wet graphite nanopores with pore size distribution. The pore network system consists of two different setups of connected bulk and a 5-nm pore in the middle; and the bulk connected to 5-nm and 2-nm pores. Our results show that nanopore confinement influences the phase equilibrium of the multicomponent hydrocarbon mixtures and this effect is stronger for smaller pores. We recognized multiple adsorbed layers of hydrocarbon molecules near the pore surface. However, for smaller pores, adsorption is dominant so that, for the 2-nm pore, most of the hydrocarbon molecules are in the adsorbed phase. The MD simulation results revealed that the overall composition of the hydrocarbon mixture is a function of pore size. This has major implications for macro-scale unconventional reservoir simulation, as it suggests that heterogenous shale nanopores would host fluids with different compositions depending on the pore size. The results of this paper suggest that modifications should be made to the calculation of overall composition of reservoir fluids in shale nanopores, as using only one overall composition for the entire heterogenous reservoir can result in significant error in recovery estimations. Full article

(This article belongs to the Special Issue Confinement Effect on the Stability of Different Molecular Species inside Nanostructures)

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14 pages, 33641 KiB

Open AccessEditor’s ChoiceArticle

A Novel Carbon-Assisted Chemical Vapor Deposition Growth of Large-Area Uniform Monolayer MoS₂ and WS₂

by Jeonghwan Bae and Youngdong Yoo

Nanomaterials 2021, 11(9), 2423; https://doi.org/10.3390/nano11092423 - 17 Sep 2021

Cited by 12 | Viewed by 4925

Abstract

Monolayer MoS₂ can be used for various applications such as flexible optoelectronics and electronics due to its exceptional optical and electronic properties. For these applications, large-area synthesis of high-quality monolayer MoS₂ is highly desirable. However, the conventional chemical vapor deposition (CVD) [...] Read more.

Monolayer MoS₂ can be used for various applications such as flexible optoelectronics and electronics due to its exceptional optical and electronic properties. For these applications, large-area synthesis of high-quality monolayer MoS₂ is highly desirable. However, the conventional chemical vapor deposition (CVD) method using MoO₃ and S powder has shown limitations in synthesizing high-quality monolayer MoS₂ over a large area on a substrate. In this study, we present a novel carbon cloth-assisted CVD method for large-area uniform synthesis of high-quality monolayer MoS₂. While the conventional CVD method produces thick MoS₂ films in the center of the substrate and forms MoS₂ monolayers at the edge of the thick MoS₂ films, our carbon cloth-assisted CVD method uniformly grows high-quality monolayer MoS₂ in the center of the substrate. The as-synthesized monolayer MoS₂ was characterized in detail by Raman/photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy. We reveal the growth process of monolayer MoS₂ initiated from MoS₂ seeds by synthesizing monolayer MoS₂ with varying reaction times. In addition, we show that the CVD method employing carbon powder also produces uniform monolayer MoS₂ without forming thick MoS₂ films in the center of the substrate. This confirms that the large-area growth of monolayer MoS₂ using the carbon cloth-assisted CVD method is mainly due to reducing properties of the carbon material, rather than the effect of covering the carbon cloth. Furthermore, we demonstrate that our carbon cloth-assisted CVD method is generally applicable to large-area uniform synthesis of other monolayer transition metal dichalcogenides, including monolayer WS₂. Full article

(This article belongs to the Special Issue New Growth Mechanisms for Synthesizing Various Novel Nanostructures)

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13 pages, 2214 KiB

Open AccessEditor’s ChoiceArticle

Improved Sensitivity of Surface-Enhanced Raman Scattering with Gold Nanoparticles-Insulator-Metal Sandwich Layers on Flat Sapphire Substrate

by Wenbing Li, Xin Tong, Zhuo Yang, Jiali Zhang, Bo Liu and Chao Ping Chen

Nanomaterials 2021, 11(9), 2416; https://doi.org/10.3390/nano11092416 - 16 Sep 2021

Cited by 1 | Viewed by 3817

Abstract

Surface-enhanced Raman scattering (SERS) as a high sensitivity analytical method for molecule detection has attracted much attention in recent research. In this work, we demonstrated an improved SERS substrate, which has the gold nanoparticles randomly distributed on a SiO₂ interception layer over [...] Read more.

Surface-enhanced Raman scattering (SERS) as a high sensitivity analytical method for molecule detection has attracted much attention in recent research. In this work, we demonstrated an improved SERS substrate, which has the gold nanoparticles randomly distributed on a SiO₂ interception layer over a gold thin film layer on the flat sapphire substrate (AuNP/SiO₂/Au/Sapphire), over the dispersed gold nanoparticles on a silicon substrate (AuNP/Si), for detection of R6G (1 × 10⁻⁶ M) in a Raman microscope. The fabrication of sandwich layers on top of the sapphire substrate involves evaporation of a gold mirror as thick as 100 nm, plasma enhanced chemical vapor deposition of the silica insulator layer 10 nm thick, and evaporation of a thin gold layer 10 nm thick for forming gold nanoparticles. For comparison, a gold thin film with a thickness of 5 nm and 10 nm was evaporated on a silicon substrate, respectively (AuNP/Si), as the reference SERS substrates in the experiment. The AuNP/SiO₂/Au/Sapphire substrate demonstrated improved sensitivity in detection of molecules in Raman microscopy, which can enable the molecules to be recognizable at a low laser power as 8.5 × 10⁻³ mW, 0.017 mW, 0.085 mW, and 0.17 mW for ultrashort exposure time. The simulation of AuNP/SiO₂/Au/Sapphire substrate and AuNP/Si substrate, based on the finite-difference time-domain (FDTD) method, explained the improved sensitivity for detection of R6G molecules from the view of classical electromagnetics, and it suggested the optimized size for the gold nanoparticles and the optimized laser wavelength for Raman microscopy for further research. Full article

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17 pages, 4983 KiB

Open AccessEditor’s ChoiceArticle

Acetone-Sensitive Thin Films Comprising Coal Fly Ash Na-X Zeolites and Sol–Gel Nb₂O₅ Matrix

by Katerina Lazarova, Silviya Boycheva, Marina Vasileva, Denitza Zgureva-Filipova, Biliana Georgieva and Tsvetanka Babeva

Nanomaterials 2021, 11(9), 2399; https://doi.org/10.3390/nano11092399 - 15 Sep 2021

Viewed by 2262

Abstract

In this study, thin composite films of a sol–gel Nb₂O₅ matrix doped with coal fly ash Na-X zeolites were deposited by the spin-coating method. Fly ash of lignite coal collected from the electrostatic precipitators of one of the biggest TPPs [...] Read more.

In this study, thin composite films of a sol–gel Nb₂O₅ matrix doped with coal fly ash Na-X zeolites were deposited by the spin-coating method. Fly ash of lignite coal collected from the electrostatic precipitators of one of the biggest TPPs in Bulgaria was used as a raw material for obtaining zeolites. Zeolite Na-X was synthesized by ultrasonic-assisted double stage fusion-hydrothermal alkaline conversion of coal fly ash. In order to improve the optical quality and sensing properties of the deposited thin films, synthesized zeolites were wet-milled for 60, 120, and 540 s prior to film deposition. The surface morphology of zeolite powders was studied both by scanning electron microscopy and transmission electron microscopy, while their porosity was investigated by N₂-physisorption. Refractive index, extinction coefficient, and thickness of the films were determined through fitting of their reflectance spectra. The sensing ability of thin films towards acetone vapors was tested by measuring the reflectance spectra prior to and during exposure to the analyte, and the change in the reflection coefficient ∆R of the films was calculated. The influence of milling time of zeolites on the sensing and optical properties of the films was assumed and confirmed. Full article

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16 pages, 2695 KiB

Open AccessEditor’s ChoiceArticle

Fluorinated Boron-Based Anions for Higher Voltage Li Metal Battery Electrolytes

by Jonathan Clarke-Hannaford, Michael Breedon, Thomas Rüther and Michelle J. S. Spencer

Nanomaterials 2021, 11(9), 2391; https://doi.org/10.3390/nano11092391 - 14 Sep 2021

Cited by 7 | Viewed by 3874

Abstract

Lithium metal batteries (LMBs) require an electrolyte with high ionic conductivity as well as high thermal and electrochemical stability that can maintain a stable solid electrolyte interphase (SEI) layer on the lithium metal anode surface. The borate anions tetrakis(trifluoromethyl)borate ([B(CF₃)₄ [...] Read more.

Lithium metal batteries (LMBs) require an electrolyte with high ionic conductivity as well as high thermal and electrochemical stability that can maintain a stable solid electrolyte interphase (SEI) layer on the lithium metal anode surface. The borate anions tetrakis(trifluoromethyl)borate ([B(CF₃)₄]⁻), pentafluoroethyltrifluoroborate ([(C₂F₅)BF₃]⁻), and pentafluoroethyldifluorocyanoborate ([(C₂F₅)BF₂(CN)]⁻) have shown excellent physicochemical properties and electrochemical stability windows; however, the suitability of these anions as high-voltage LMB electrolytes components that can stabilise the Li anode is yet to be determined. In this work, density functional theory calculations show high reductive stability limits and low anion–cation interaction strengths for Li[B(CF₃)₄], Li[(C₂F₅)BF₃], and Li[(C₂F₅)BF₂(CN)] that surpass popular sulfonamide salts. Specifically, Li[B(CF₃)₄] has a calculated oxidative stability limit of 7.12 V vs. Li⁺/Li⁰ which is significantly higher than the other borate and sulfonamide salts (≤6.41 V vs. Li⁺/Li⁰). Using ab initio molecular dynamics simulations, this study is the first to show that these borate anions can form an advantageous LiF-rich SEI layer on the Li anode at room (298 K) and elevated (358 K) temperatures. The interaction of the borate anions, particularly [B(CF₃)₄]⁻, with the Li⁺ and Li anode, suggests they are suitable inclusions in high-voltage LMB electrolytes that can stabilise the Li anode surface and provide enhanced ionic conductivity. Full article

(This article belongs to the Special Issue Advanced Materials for Lithium (and Post-Lithium) Batteries)

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22 pages, 9225 KiB

Open AccessEditor’s ChoiceArticle

Antibacterial Biodegradable Films Based on Alginate with Silver Nanoparticles and Lemongrass Essential Oil–Innovative Packaging for Cheese

by Ludmila Motelica, Denisa Ficai, Ovidiu-Cristian Oprea, Anton Ficai, Vladimir-Lucian Ene, Bogdan-Stefan Vasile, Ecaterina Andronescu and Alina-Maria Holban

Nanomaterials 2021, 11(9), 2377; https://doi.org/10.3390/nano11092377 - 13 Sep 2021

Cited by 110 | Viewed by 7014

Abstract

Replacing the petroleum-based materials in the food industry is one of the main objectives of the scientists and decision makers worldwide. Biodegradable packaging will help diminish the environmental impact of human activity. Improving such biodegradable packaging materials by adding antimicrobial activity will not [...] Read more.

Replacing the petroleum-based materials in the food industry is one of the main objectives of the scientists and decision makers worldwide. Biodegradable packaging will help diminish the environmental impact of human activity. Improving such biodegradable packaging materials by adding antimicrobial activity will not only extend the shelf life of foodstuff, but will also eliminate some health hazards associated with food borne diseases, and by diminishing the food spoilage will decrease the food waste. The objective of this research was to obtain innovative antibacterial films based on a biodegradable polymer, namely alginate. Films were characterized by environmental scanning electron microscopy (ESEM), Fourier-transform infrared spectroscopy (FTIR) and microscopy, complex thermal analysis (TG-DSC-FTIR), UV-Vis and fluorescence spectroscopy. Water vapor permeability and swelling behavior were also determined. As antimicrobial agents, we used silver spherical nanoparticles (Ag NPs) and lemongrass essential oil (LGO), which were found to act in a synergic way. The obtained films exhibited strong antibacterial activity against tested strains, two Gram-positive (Bacillus cereus and Staphylococcus aureus) and two Gram-negative (Escherichia coli and Salmonella Typhi). Best results were obtained against Bacillus cereus. The tests indicate that the antimicrobial films can be used as packaging, preserving the color, surface texture, and softness of cheese for 14 days. At the same time, the color of the films changed (darkened) as a function of temperature and light presence, a feature that can be used to monitor the storage conditions for sensitive food. Full article

(This article belongs to the Special Issue Food Packaging Bionanocomposites)

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14 pages, 3048 KiB

Open AccessEditor’s ChoiceArticle

Amino-Functionalized Fe₃O₄@SiO₂ Core-Shell Magnetic Nanoparticles for Dye Adsorption

by Chun-Rong Lin, Oxana S. Ivanova, Dmitry A. Petrov, Alexey E. Sokolov, Ying-Zhen Chen, Marina A. Gerasimova, Sergey M. Zharkov, Yaw-Teng Tseng, Nicolay P. Shestakov and Irina S. Edelman

Nanomaterials 2021, 11(9), 2371; https://doi.org/10.3390/nano11092371 - 12 Sep 2021

Cited by 33 | Viewed by 4625

Abstract

Fe₃O₄@SiO₂ core-shell nanoparticles (NPs) were synthesized with the co-precipitation method and functionalized with NH₂ amino-groups. The nanoparticles were characterized by X-ray, FT-IR spectroscopy, transmission electron microscopy, selected area electron diffraction, and vibrating sample magnetometry. The magnetic core [...] Read more.

Fe₃O₄@SiO₂ core-shell nanoparticles (NPs) were synthesized with the co-precipitation method and functionalized with NH₂ amino-groups. The nanoparticles were characterized by X-ray, FT-IR spectroscopy, transmission electron microscopy, selected area electron diffraction, and vibrating sample magnetometry. The magnetic core of all the nanoparticles was shown to be nanocrystalline with the crystal parameters corresponding only to the Fe₃O₄ phase covered with a homogeneous amorphous silica (SiO₂) shell of about 6 nm in thickness. The FT-IR spectra confirmed the appearance of chemical bonds at amino functionalization. The magnetic measurements revealed unusually high saturation magnetization of the initial Fe₃O₄ nanoparticles, which was presumably associated with the deviations in the Fe ion distribution between the tetrahedral and octahedral positions in the nanocrystals as compared to the bulk stoichiometric magnetite. The fluorescent spectrum of eosin Y-doped NPs dispersed in water solution was obtained and a red shift and line broadening (in comparison with the dye molecules being free in water) were revealed and explained. Most attention was paid to the adsorption properties of the nanoparticles with respect to three dyes: methylene blue, Congo red, and eosin Y. The kinetic data showed that the adsorption processes were associated with the pseudo-second order mechanism for all three dyes. The equilibrium data were more compatible with the Langmuir isotherm and the maximum adsorption capacity was reached for Congo red. Full article

(This article belongs to the Section Nanocomposite Materials)

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24 pages, 17456 KiB

Open AccessEditor’s ChoiceReview

3D-Printable Nanocellulose-Based Functional Materials: Fundamentals and Applications

by Abraham Samuel Finny, Oluwatosin Popoola and Silvana Andreescu

Nanomaterials 2021, 11(9), 2358; https://doi.org/10.3390/nano11092358 - 11 Sep 2021

Cited by 45 | Viewed by 7907

Abstract

Nanomaterials obtained from sustainable and natural sources have seen tremendous growth in recent times due to increasing interest in utilizing readily and widely available resources. Nanocellulose materials extracted from renewable biomasses hold great promise for increasing the sustainability of conventional materials in various [...] Read more.

Nanomaterials obtained from sustainable and natural sources have seen tremendous growth in recent times due to increasing interest in utilizing readily and widely available resources. Nanocellulose materials extracted from renewable biomasses hold great promise for increasing the sustainability of conventional materials in various applications owing to their biocompatibility, mechanical properties, ease of functionalization, and high abundance. Nanocellulose can be used to reinforce mechanical strength, impart antimicrobial activity, provide lighter, biodegradable, and more robust materials for packaging, and produce photochromic and electrochromic devices. While the fabrication and properties of nanocellulose are generally well established, their implementation in novel products and applications requires surface modification, assembly, and manufacturability to enable rapid tooling and scalable production. Additive manufacturing techniques such as 3D printing can improve functionality and enhance the ability to customize products while reducing fabrication time and wastage of materials. This review article provides an overview of nanocellulose as a sustainable material, covering the different properties, preparation methods, printability and strategies to functionalize nanocellulose into 3D-printed constructs. The applications of 3D-printed nanocellulose composites in food, environmental, and energy devices are outlined, and an overview of challenges and opportunities is provided. Full article

(This article belongs to the Special Issue Synthesis, Applications and Biological Impact of Nanocellulose)

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20 pages, 3950 KiB

Open AccessEditor’s ChoiceReview

Influence of Titanium Dioxide Nanoparticles on Human Health and the Environment

by Mohammad Mamunur Rashid, Petra Forte Tavčer and Brigita Tomšič

Nanomaterials 2021, 11(9), 2354; https://doi.org/10.3390/nano11092354 - 10 Sep 2021

Cited by 127 | Viewed by 8960

Abstract

Nanotechnology has enabled tremendous breakthroughs in the development of materials and, nowadays, is well established in various economic fields. Among the various nanomaterials, TiO₂ nanoparticles (NPs) occupy a special position, as they are distinguished by their high availability, high photocatalytic activity, and [...] Read more.

Nanotechnology has enabled tremendous breakthroughs in the development of materials and, nowadays, is well established in various economic fields. Among the various nanomaterials, TiO₂ nanoparticles (NPs) occupy a special position, as they are distinguished by their high availability, high photocatalytic activity, and favorable price, which make them useful in the production of paints, plastics, paper, cosmetics, food, furniture, etc. In textiles, TiO₂ NPs are widely used in chemical finishing processes to impart various protective functional properties to the fibers for the production of high-tech textile products with high added value. Such applications contribute to the overall consumption of TiO₂ NPs, which gives rise to reasonable considerations about the impact of TiO₂ NPs on human health and the environment, and debates regarding whether the extent of the benefits gained from the use of TiO₂ NPs justifies the potential risks. In this study, different TiO₂ NPs exposure modes are discussed, and their toxicity mechanisms—evaluated in various in vitro and in vivo studies—are briefly described, considering the molecular interactions with human health and the environment. In addition, in the conclusion of this study, the toxicity and biocompatibility of TiO₂ NPs are discussed, along with relevant risk management strategies. Full article

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12 pages, 1191 KiB

Open AccessEditor’s ChoiceArticle

Solid State Photoreduction of Silver on Mesoporous Silica to Enhance Antifungal Activity

by Giulia Quaglia, Valeria Ambrogi, Donatella Pietrella, Morena Nocchetti and Loredana Latterini

Nanomaterials 2021, 11(9), 2340; https://doi.org/10.3390/nano11092340 - 9 Sep 2021

Cited by 7 | Viewed by 2915

Abstract

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag⁰ nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO₃, is irradiated at 366 nm, [...] Read more.

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag⁰ nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO₃, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag⁰ nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag⁰. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver–silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity. Full article

(This article belongs to the Special Issue Metallic and Metal Oxide Nanoparticles and Their Applications)

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72 pages, 3944 KiB

Open AccessEditor’s ChoiceReview

Iron Oxide Nanoparticles in Regenerative Medicine and Tissue Engineering

by Ralf P. Friedrich, Iwona Cicha and Christoph Alexiou

Nanomaterials 2021, 11(9), 2337; https://doi.org/10.3390/nano11092337 - 8 Sep 2021

Cited by 95 | Viewed by 10547

Abstract

In recent years, many promising nanotechnological approaches to biomedical research have been developed in order to increase implementation of regenerative medicine and tissue engineering in clinical practice. In the meantime, the use of nanomaterials for the regeneration of diseased or injured tissues is [...] Read more.

In recent years, many promising nanotechnological approaches to biomedical research have been developed in order to increase implementation of regenerative medicine and tissue engineering in clinical practice. In the meantime, the use of nanomaterials for the regeneration of diseased or injured tissues is considered advantageous in most areas of medicine. In particular, for the treatment of cardiovascular, osteochondral and neurological defects, but also for the recovery of functions of other organs such as kidney, liver, pancreas, bladder, urethra and for wound healing, nanomaterials are increasingly being developed that serve as scaffolds, mimic the extracellular matrix and promote adhesion or differentiation of cells. This review focuses on the latest developments in regenerative medicine, in which iron oxide nanoparticles (IONPs) play a crucial role for tissue engineering and cell therapy. IONPs are not only enabling the use of non-invasive observation methods to monitor the therapy, but can also accelerate and enhance regeneration, either thanks to their inherent magnetic properties or by functionalization with bioactive or therapeutic compounds, such as drugs, enzymes and growth factors. In addition, the presence of magnetic fields can direct IONP-labeled cells specifically to the site of action or induce cell differentiation into a specific cell type through mechanotransduction. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Tissue Engineering Applications)

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15 pages, 5121 KiB

Open AccessEditor’s ChoiceArticle

Pd-C Catalytic Thin Films Prepared by Magnetron Sputtering for the Decomposition of Formic Acid

by Gisela Mariana Arzac, Asunción Fernández, Vanda Godinho, Dirk Hufschmidt, Maria Carmen Jiménez de Haro, Beatriz Medrán and Olga Montes

Nanomaterials 2021, 11(9), 2326; https://doi.org/10.3390/nano11092326 - 7 Sep 2021

Cited by 5 | Viewed by 3147

Abstract

Formic acid is an advantageous liquid organic hydrogen carrier. It is relatively nontoxic and can be synthesized by the reaction of CO₂ with sustainable hydrogen or by biomass decomposition. As an alternative to more widely studied powdery catalysts, supported Pd-C catalytic thin [...] Read more.

Formic acid is an advantageous liquid organic hydrogen carrier. It is relatively nontoxic and can be synthesized by the reaction of CO₂ with sustainable hydrogen or by biomass decomposition. As an alternative to more widely studied powdery catalysts, supported Pd-C catalytic thin films with controlled nanostructure and compositions were newly prepared in this work by magnetron sputtering on structured supports and tested for the formic acid decomposition reaction. A two-magnetron configuration (carbon and tailored Pd-C targets) was used to achieve a reduction in Pd consumption and high catalyst surface roughness and dispersion by increasing the carbon content. Activity and durability tests were carried out for the gas phase formic acid decomposition reaction on SiC foam monoliths coated with the Pd-C films and the effects of column width, surface roughness and thermal pre-reduction time were investigated. Activity of 5.04 mol_H2·g_Pd⁻¹·h⁻¹ and 92% selectivity to the dehydrogenation reaction were achieved at 300 °C for the catalyst with a lower column width and higher carbon content and surface roughness. It was also found that deactivation occurs when Pd is sintered due to the elimination of carbon and/or the segregation and agglomeration of Pd upon cycling. Magnetron sputtering deposition appears as a promising and scalable route for the one-step preparation of Pd-C catalytic films by overcoming the different deposition characteristics of Pd and C with an appropriate experimental design. Full article

(This article belongs to the Special Issue Nanostructures for Surfaces, Catalysis and Sensing)

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15 pages, 1636 KiB

Open AccessEditor’s ChoiceArticle

Bayesian Data Assimilation of Temperature Dependence of Solid–Liquid Interfacial Properties of Nickel

by Yuhi Nagatsuma, Munekazu Ohno, Tomohiro Takaki and Yasushi Shibuta

Nanomaterials 2021, 11(9), 2308; https://doi.org/10.3390/nano11092308 - 6 Sep 2021

Cited by 17 | Viewed by 3723

Abstract

Temperature dependence of solid–liquid interfacial properties during crystal growth in nickel was investigated by ensemble Kalman filter (EnKF)-based data assimilation, in which the phase-field simulation was combined with atomic configurations of molecular dynamics (MD) simulation. Negative temperature dependence was found in the solid–liquid [...] Read more.

Temperature dependence of solid–liquid interfacial properties during crystal growth in nickel was investigated by ensemble Kalman filter (EnKF)-based data assimilation, in which the phase-field simulation was combined with atomic configurations of molecular dynamics (MD) simulation. Negative temperature dependence was found in the solid–liquid interfacial energy, the kinetic coefficient, and their anisotropy parameters from simultaneous estimation of four parameters. On the other hand, it is difficult to obtain a concrete value for the anisotropy parameter of solid–liquid interfacial energy since this factor is less influential for the MD simulation of crystal growth at high undercooling temperatures. The present study is significant in shedding light on the high potential of Bayesian data assimilation as a novel methodology of parameter estimation of practical materials an out of equilibrium condition. Full article

(This article belongs to the Special Issue Thermal, Mechanical and Radiation Stability of Nanostructured Metals)

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18 pages, 3993 KiB

Open AccessEditor’s ChoiceArticle

Marble Waste Sludges as Effective Nanomaterials for Cu (II) Adsorption in Aqueous Media

by Ventura Castillo Ramos, José Rivera Utrilla, Antonio Ruiz Sánchez, María Victoria López Ramón and Manuel Sánchez Polo

Nanomaterials 2021, 11(9), 2305; https://doi.org/10.3390/nano11092305 - 5 Sep 2021

Cited by 15 | Viewed by 2614

Abstract

This study evaluated the waste generated by a Spanish marble-producing company as adsorbent for the removal of copper (Cu [II]) from aqueous media. Six marble waste sludge samples were studied, and the following operational parameters were analyzed in discontinuous regime, including pollutant concentration, [...] Read more.

This study evaluated the waste generated by a Spanish marble-producing company as adsorbent for the removal of copper (Cu [II]) from aqueous media. Six marble waste sludge samples were studied, and the following operational parameters were analyzed in discontinuous regime, including pollutant concentration, pH, temperature, nature of aqueous medium, and ionic strength. The applicability of the adsorbent material was assessed with experiments in both continuous and discontinuous regimes under close-to-real-life conditions. A pseudo-second order model yielded a better fit to the kinetic data. Application of the intraparticle diffusion model revealed two well-differentiated adsorption stages, in which the external material transfer is negligible and intraparticle diffusion is the controlling stage. The equilibrium study was better fitted to a Freundlich-type isotherm, predicting elevated maximum adsorption values (22.7 mg g⁻¹) at a relatively low initial Cu (II) concentration (25 ppm), yielding a highly favorable chemisorption process (n >> 1). X-ray fluorescence study identified calcite (CaCO₃) as the main component of marble waste sludges. According to X-ray diffraction analysis, Cu (II) ion adsorption occurred by intercalation of the metallic cation between CaCO₃ layers and by the formation of surface complexes such as CaCO₃ and Cu₂(CO₃)(OH)₂. Cu (II) was more effectively removed at medium pH, lower temperature, and lower ionic strength of the aqueous medium. The salinity and dissolved organic matter in surface, ground-, and waste-waters negatively affected the Cu (II) removal process in both continuous and discontinuous regimes by competing for active adsorption sites. These findings demonstrate the applicability and effectiveness of marble-derived waste sludges as low-cost and readily available adsorbents for the treatment of waters polluted by Cu (II) under close-to-real-life conditions. Full article

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19 pages, 1126 KiB

Open AccessEditor’s ChoiceArticle

MHD Williamson Nanofluid Flow over a Slender Elastic Sheet of Irregular Thickness in the Presence of Bioconvection

by Fuzhang Wang, Muhammad Imran Asjad, Saif Ur Rehman, Bagh Ali, Sajjad Hussain, Tuan Nguyen Gia and Taseer Muhammad

Nanomaterials 2021, 11(9), 2297; https://doi.org/10.3390/nano11092297 - 3 Sep 2021

Cited by 58 | Viewed by 3416

Abstract

Bioconvection phenomena for MHD Williamson nanofluid flow over an extending sheet of irregular thickness are investigated theoretically, and non-uniform viscosity and thermal conductivity depending on temperature are taken into account. The magnetic field of uniform strength creates a magnetohydrodynamics effect. The basic formulation [...] Read more.

Bioconvection phenomena for MHD Williamson nanofluid flow over an extending sheet of irregular thickness are investigated theoretically, and non-uniform viscosity and thermal conductivity depending on temperature are taken into account. The magnetic field of uniform strength creates a magnetohydrodynamics effect. The basic formulation of the model developed in partial differential equations which are later transmuted into ordinary differential equations by employing similarity variables. To elucidate the influences of controlling parameters on dependent quantities of physical significance, a computational procedure based on the Runge–Kutta method along shooting technique is coded in MATLAB platform. This is a widely used procedure for the solution of such problems because it is efficient with fifth-order accuracy and cost-effectiveness. The enumeration of the results reveals that Williamson fluid parameter

λ

, variable viscosity parameter

Λ_{μ}

and wall thickness parameter

ς

impart reciprocally decreasing effect on fluid velocity whereas these parameters directly enhance the fluid temperature. The fluid temperature is also improved with Brownian motion parameter

N b

and thermophoresis parameter

N t

. The boosted value of Brownian motion

N b

and Lewis number

L e

reduce the concentration of nanoparticles. The higher inputs of Peclet number

P e

and bioconvection Lewis number

L b

decline the bioconvection distribution. The velocity of non-Newtonian (Williamson nanofluid) is less than the viscous nanofluid but temperature behaves oppositely. Full article

(This article belongs to the Special Issue New Frontiers in Nanofluids)

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9 pages, 2035 KiB

Open AccessEditor’s ChoiceCommunication

Structural Insight into La_0.5Ca_0.5Mn_0.5Co_0.5O₃ Decomposition in the Methane Combustion Process

by Olga Nikolaeva, Aleksandr Kapishnikov and Evgeny Gerasimov

Nanomaterials 2021, 11(9), 2283; https://doi.org/10.3390/nano11092283 - 2 Sep 2021

Cited by 3 | Viewed by 1892

Abstract

Perovskite-like solid solution La_0.5Ca_0.5Mn_0.5Co_0.5O₃ was tested during the total methane combustion reaction. During the reaction, there is a noticeable decrease in methane conversion, the rate of catalyst deactivation increasing with an increase in temperature. [...] Read more.

Perovskite-like solid solution La_0.5Ca_0.5Mn_0.5Co_0.5O₃ was tested during the total methane combustion reaction. During the reaction, there is a noticeable decrease in methane conversion, the rate of catalyst deactivation increasing with an increase in temperature. The in situ XRD and HRTEM methods show that the observed deactivation occurs as a result of the segregation of calcite and cobalt oxide particles on the perovskite surface. According to the TGA, the observed drop in catalytic activity is also associated with a large loss of oxygen from the perovskite structure. Full article

(This article belongs to the Special Issue Synthesis of Nanocomposites and Catalysis Applications)

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17 pages, 37615 KiB

Open AccessEditor’s ChoiceArticle

Flexible Layered-Graphene Charge Modulation for Highly Stable Triboelectric Nanogenerator

by Mamina Sahoo, Sz-Nian Lai, Jyh-Ming Wu, Ming-Chung Wu and Chao-Sung Lai

Nanomaterials 2021, 11(9), 2276; https://doi.org/10.3390/nano11092276 - 1 Sep 2021

Cited by 20 | Viewed by 4339

Abstract

The continuous quest to enhance the output performance of triboelectric nanogenerators (TENGs) based on the surface charge density of the tribolayer has motivated researchers to harvest mechanical energy efficiently. Most of the previous work focused on the enhancement of negative triboelectric charges. The [...] Read more.

The continuous quest to enhance the output performance of triboelectric nanogenerators (TENGs) based on the surface charge density of the tribolayer has motivated researchers to harvest mechanical energy efficiently. Most of the previous work focused on the enhancement of negative triboelectric charges. The enhancement of charge density over positive tribolayer has been less investigated. In this work, we developed a layer-by-layer assembled multilayer graphene-based TENG to enhance the charge density by creatively introducing a charge trapping layer (CTL) Al₂O₃ in between the positive triboelectric layer and conducting electrode to construct an attractive flexible TENG. Based on the experimental results, the optimized three layers of graphene TENG (3L-Gr-TENG) with CTL showed a 30-fold enhancement in output power compared to its counterpart, 3L-Gr-TENG without CTL. This remarkably enhanced performance can be ascribed to the synergistic effect between the optimized graphene layers with high dielectric CTL. Moreover, the device exhibited outstanding stability after continuous operation of >2000 cycles. Additionally, the device was capable of powering 20 green LEDs and sufficient to power an electronic timer with rectifying circuits. This research provides a new insight to improve the charge density of Gr-TENGs as energy harvesters for next-generation flexible electronics. Full article

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

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