Nanomaterials

18 pages, 4855 KiB

Open AccessArticle

Enhanced Tribological Properties of Vulcanized Natural Rubber Composites by Applications of Carbon Nanotube: A Molecular Dynamics Study

by Fei Teng, Jian Wu, Benlong Su and Youshan Wang

Nanomaterials 2021, 11(9), 2464; https://doi.org/10.3390/nano11092464 - 21 Sep 2021

Cited by 19 | Viewed by 3634

Abstract

Tribological properties of tread rubber is a key problem for the safety and durability of large aircraft tires. So, new molecular models of carbon nanotube (CNT) reinforced vulcanized natural rubber (VNR) composites have been developed to study the enhanced tribological properties and reveal [...] Read more.

Tribological properties of tread rubber is a key problem for the safety and durability of large aircraft tires. So, new molecular models of carbon nanotube (CNT) reinforced vulcanized natural rubber (VNR) composites have been developed to study the enhanced tribological properties and reveal the reinforced mechanism. Firstly, the dynamic process of the CNT agglomeration is discussed from the perspectives of fractional free volume (FFV) and binding energy. Then, a combined explanation of mechanical and interfacial properties is given to reveal the CNT-reinforced mechanism of the coefficient of friction (COF). Results indicate that the bulk, shear and Young’s modulus increase with the increasement of CNT, which are increasement of 19.13%, 21.11% and 26.89% in 15 wt.% CNT/VNR composite compared to VNR; the predicted results are consistent with the existing experimental conclusions, which can be used to reveal the CNT-reinforced mechanism of the rubber materials at atomic scale. It can also guide the design of rubber material prescription for aircraft tire. The molecular dynamics study provides a theoretical basis for the design and preparation of high wear resistance of tread rubber materials. Full article

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

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9 pages, 14958 KiB

Open AccessArticle

Angstrom-Scale Active Width Control of Nano Slits for Variable Plasmonic Cavity

by Dukhyung Lee, Dohee Lee, Hyeong Seok Yun and Dai-Sik Kim

Nanomaterials 2021, 11(9), 2463; https://doi.org/10.3390/nano11092463 - 21 Sep 2021

Cited by 3 | Viewed by 2651

Abstract

Nanogap slits can operate as a plasmonic Fabry–Perot cavity in the visible and infrared ranges due to the gap plasmon with an increased wavenumber. Although the properties of gap plasmon are highly dependent on the gap width, active width tuning of the plasmonic [...] Read more.

Nanogap slits can operate as a plasmonic Fabry–Perot cavity in the visible and infrared ranges due to the gap plasmon with an increased wavenumber. Although the properties of gap plasmon are highly dependent on the gap width, active width tuning of the plasmonic cavity over the wafer length scale was barely realized. Recently, the fabrication of nanogap slits on a flexible substrate was demonstrated to show that the width can be adjusted by bending the flexible substrate. In this work, by conducting finite element method (FEM) simulation, we investigated the structural deformation of nanogap slit arrays on an outer bent polydimethylsiloxane (PDMS) substrate and the change of the optical properties. We found that the tensile deformation is concentrated in the vicinity of the gap bottom to widen the gap width proportionally to the substrate curvature. The width widening leads to resonance blueshift and field enhancement decrease. Displacement ratio ((width change)/(supporting stage translation)), which was identified to be proportional to the substrate thickness and slit period, is on the order of 10⁻⁵ enabling angstrom-scale width control. This low displacement ratio comparable to a mechanically controllable break junction highlights the great potential of nanogap slit structures on a flexible substrate, particularly in quantum plasmonics. Full article

(This article belongs to the Special Issue Nano-Optics: Novel Research on Theory and Applications)

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11 pages, 3341 KiB

Open AccessArticle

Stable Fluorescence of Eu³⁺ Complex Nanostructures Beneath a Protein Skin for Potential Biometric Recognition

by Yue Zhao, Ziyu Yao, Christopher D. Snow, Yanan Xu, Yao Wang, Dan Xiu, Laurence A. Belfiore and Jianguo Tang

Nanomaterials 2021, 11(9), 2462; https://doi.org/10.3390/nano11092462 - 21 Sep 2021

Cited by 8 | Viewed by 2461

Abstract

We designed and realized highly fluorescent nanostructures composed of Eu³⁺ complexes under a protein coating. The nanostructured material, confirmed by photo-induced force microscopy (PiFM), includes a bottom fluorescent layer and an upper protein layer. The bottom fluorescent layer includes Eu³⁺ that [...] Read more.

We designed and realized highly fluorescent nanostructures composed of Eu³⁺ complexes under a protein coating. The nanostructured material, confirmed by photo-induced force microscopy (PiFM), includes a bottom fluorescent layer and an upper protein layer. The bottom fluorescent layer includes Eu³⁺ that is coordinated by 1,10-phenanthroline (Phen) and oleic acid (O). The complete complexes (OEu³⁺Phen) formed higher-order structures with diameter 40–150 nm. Distinctive nanoscale striations reminiscent of fingerprints were observed with a high-resolution transmission electron microscope (HRTEM). Stable fluorescence was increased by the addition of Eu³⁺ coordinated by Phen and 2-thenoyltrifluoroacetone (TTA), and confirmed by fluorescence spectroscopy. A satisfactory result was the observation of red Eu³⁺ complex emission through a protein coating layer with a fluorescence microscope. Lanthanide nanostructures of these types might ultimately prove useful for biometric applications in the context of human and non-human tissues. The significant innovations of this work include: (1) the structural set-up of the fluorescence image embedded under protein “skin”; and (2) dual confirmations of nanotopography and unique nanofingerprints under PiFM and under TEM, respectively. Full article

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17 pages, 7891 KiB

Open AccessArticle

Structural and Magnetic Properties of Co_0.5Ni_0.5Ga_0.01Gd_0.01Fe_1.98O₄/ZnFe₂O₄ Spinel Ferrite Nanocomposites: Comparative Study between Sol-Gel and Pulsed Laser Ablation in Liquid Approaches

by Munirah A. Almessiere, Sadik Güner, Yassine Slimani, Mohammed Hassan, Abdulhadi Baykal, Mohammed Ashraf Gondal, Umair Baig, Sergei V. Trukhanov and Alex V. Trukhanov

Nanomaterials 2021, 11(9), 2461; https://doi.org/10.3390/nano11092461 - 21 Sep 2021

Cited by 66 | Viewed by 3549

Abstract

In this study, the samples of the ZnFe₂O₄ (ZFO) spinel ferrites nanoparticles (SFNPs), Co_0.5Ni_0.5Ga_0.01Gd_0.01Fe_1.98O₄ (CNGaGdFO) SFNPs and (Co_0.5Ni_0.5Ga_0.01Gd_0.01Fe_1.98O₄ [...] Read more.

In this study, the samples of the ZnFe₂O₄ (ZFO) spinel ferrites nanoparticles (SFNPs), Co_0.5Ni_0.5Ga_0.01Gd_0.01Fe_1.98O₄ (CNGaGdFO) SFNPs and (Co_0.5Ni_0.5Ga_0.01Gd_0.01Fe_1.98O₄)_x/(ZnFe₂O₄)_y (x:y = 1:1, 1:2, 1:3, 2:1, 3:1 and 4:1) (CNGaGdFO)_x/(ZFO)_y spinel ferrite nanocomposites (NC) have been synthesized by both sol-gel and Green pulsed laser ablation in liquid (PLAL) approaches. All products were characterized by X-ray powder diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), elemental mappings and energy dispersive X-ray spectroscopy (EDX). It was objected to tune the magnetic properties of a soft spinel ferrite material with a softer one by mixing them with different fractions. Some key findings are as follows. M-H investigations revealed the exhibition of ferrimagnetic phases for all synthesized samples (except ZnFe₂O₄) that were synthesized by sol-gel or PLAL methods at both 300 K and 10 K. ZnFe₂O₄ ferrite NPs exhibits almost paramagnetic feature at 300 K and glass-like phase at very low temperatures below 19.23 K. At RT analyses, maximum saturation magnetization (M_S) of 66.53 emu/g belongs to nanocomposite samples that was synthesized by sol-gel method and x:y ratio of 1:3. At 10 K analyses, M_S,_max = 118.71 emu/g belongs to same nanocomposite samples with ratio of 1:3. Maximum coercivities are 625 Oe belonging to CNGaGdFO and 3564 Oe belonging to NC sample that was obtained by sol-gel route having the 3:1 ratio. Squareness ratio (SQRs = M_r/M_S) of NC sample (sol-gel, 4:1 ratio) is 0.371 as maximum and other samples have much lower values until a minimum of 0.121 (laser, 3:1) assign the multi-domain wall structure for all samples at 300 K. At 10 K data, just CNGaGdFO has 0.495 SQR value assigning single domain nature. The maximum values of effective crystal anisotropy constant (K_eff) are 5.92 × 10⁴ Erg/g and 2.4 × 10⁵ Erg/g belonging to CNGaGdFO at 300 K and 10 K, respectively. Further, this sample has an internal anisotropy field H_a of 1953 Oe as largest at 300 K. At 10 K another sample (sol-gel, 3:1 ratio) has H_a,max of 11138 Oe which can also be classified as a soft magnetic material similar to other samples. Briefly, most magnetic parameters of NCs that were synthesized by sol-gel route are stronger than magnetic parameters of the NCs that were synthesized by PLAL at both temperatures. Some NC samples were observed to have stronger magnetic data as compared to magnetic parameters of Co_0.5Ni_0.5Ga_0.01Gd_0.01Fe_1.98O₄ NPs at 10 K. Full article

(This article belongs to the Special Issue Oxide Magnetics)

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14 pages, 28597 KiB

Open AccessArticle

Plasmon-Enhanced Photoresponse of Self-Powered Si Nanoholes Photodetector by Metal Nanowires

by Pericle Varasteanu, Antonio Radoi, Oana Tutunaru, Anton Ficai, Razvan Pascu, Mihaela Kusko and Iuliana Mihalache

Nanomaterials 2021, 11(9), 2460; https://doi.org/10.3390/nano11092460 - 21 Sep 2021

Cited by 7 | Viewed by 3071

Abstract

In this work, we report the development of self-powered photodetectors that integrate silicon nanoholes (SiNHs) and four different types of metal nanowires (AgNWs, AuNWs, NiNWs, PtNWs) applied on the SiNHs’ surface using the solution processing method. The effectiveness of the proposed architectures is [...] Read more.

In this work, we report the development of self-powered photodetectors that integrate silicon nanoholes (SiNHs) and four different types of metal nanowires (AgNWs, AuNWs, NiNWs, PtNWs) applied on the SiNHs’ surface using the solution processing method. The effectiveness of the proposed architectures is evidenced through extensive experimental and simulation analysis. The AgNWs/SiNHs device showed the highest photo-to-dark current ratio of 2.1 × 10⁻⁴, responsivity of 30 mA/W and detectivity of 2 × 10¹¹ Jones along with the lowest noise equivalent power (NEP) parameter of 2.4 × 10⁻¹² WHz^−1/2 in the blue light region. Compared to the bare SiNHs device, the AuNWs/SiNHs device had significantly enhanced responsivity up to 15 mA/W, especially in the red and near-infrared spectral region. Intensity-modulated photovoltage spectroscopy (IMVS) measurements revealed that the AgNWs/SiNHs device generated the longest charge carrier lifetime at 470 nm, whereas the AuNWs/SiNHs showed the slowest recombination rate at 627 nm. Furthermore, numerical simulation confirmed the local field enhancement effects at the MeNWs and SiNHs interface. The study demonstrates a cost-efficient and scalable strategy to combine the superior light harvesting properties of SiNHs with the plasmonic absorption of metallic nanowires (MeNWs) towards enhanced sensitivity and spectral-selective photodetection induced by the local surface plasmon resonance effects. Full article

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

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11 pages, 5984 KiB

Open AccessArticle

Nitrogen-Containing Gas Sensing Properties of 2-D Ti₂N and Its Derivative Nanosheets: Electronic Structures Insight

by Hongni Zhang, Wenzheng Du, Jianjun Zhang, Rajeev Ahuja and Zhao Qian

Nanomaterials 2021, 11(9), 2459; https://doi.org/10.3390/nano11092459 - 21 Sep 2021

Cited by 6 | Viewed by 2865

Abstract

In this work, the potentials of two-dimensional Ti₂N and its derivative nanosheets Ti₂NT₂(T=O, F, OH) for some harmful nitrogen-containing gas (NCG) adsorption and sensing applications have been unveiled based on the quantum-mechanical Density Functional Theory calculations. It [...] Read more.

In this work, the potentials of two-dimensional Ti₂N and its derivative nanosheets Ti₂NT₂(T=O, F, OH) for some harmful nitrogen-containing gas (NCG) adsorption and sensing applications have been unveiled based on the quantum-mechanical Density Functional Theory calculations. It is found that the interactions between pure Ti₂N and NCGs (including NO, NO₂, and NH₃ in this study) are very strong, in which NO and NO₂ can even be dissociated, and this would poison the substrate of Ti₂N monolayer and affect the stability of the sensing material. For the monolayer of Ti₂NT₂(T=O, F, OH) that is terminated by functional groups on surface, the adsorption energies of NCGs are greatly reduced, and a large amount of charges are transferred to the functional group, which is beneficial to the reversibility of the sensing material. The significant changes in work function imply the good sensitivity of the above mentioned materials. In addition, the fast response time further consolidates the prospect of two-dimensional Ti₂NT₂ as efficient NCGs’ sensing materials. This theoretical study would supply physical insight into the NCGs’ sensing mechanism of Ti₂N based nanosheets and help experimentalists to design better 2-D materials for gas adsorption or sensing applications. Full article

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

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12 pages, 26162 KiB

Open AccessArticle

Carbon and Neon Ion Bombardment Induced Smoothing and Surface Relaxation of Titania Nanotubes

by Astrid Kupferer, Michael Mensing, Jan Lehnert, Stephan Mändl and Stefan G. Mayr

Nanomaterials 2021, 11(9), 2458; https://doi.org/10.3390/nano11092458 - 21 Sep 2021

Cited by 3 | Viewed by 2486

Abstract

Titania nanotube arrays with their enormous surface area are the subject of much attention in diverse fields of research. In the present work, we show that not only 60 keV and 150 keV ion bombardment of amorphous titania nanotube arrays yields defect creation [...] Read more.

Titania nanotube arrays with their enormous surface area are the subject of much attention in diverse fields of research. In the present work, we show that not only 60 keV and 150 keV ion bombardment of amorphous titania nanotube arrays yields defect creation within the tube walls, but it also changes the surface morphology: the surface relaxes and smoothens in accordance with a curvature-driven surface material’s transport mechanism, which is mediated by radiation-induced viscous flow or radiation-enhanced surface diffusion, while the nanotubes act as additional sinks for the particle surface currents. These effects occur independently of the ion species: both carbon and neon ion bombardments result in comparable surface relaxation responses initiated by an ion energy of 60 keV at a fluence of 1 × 10

^{16}

ions/cm

^{2}

. Using atomic force microscopy and contact angle measurements, we thoroughly study the relaxation effects on the surface topography and surface free energy, respectively. Moreover, surface relaxation is accompanied by further amorphization in surface-near regions and a reduction in the mass density, as demonstrated by Raman spectroscopy and X-ray reflectivity. Since ion bombardment can be performed on global and local scales, it constitutes a versatile tool to achieve well-defined and tunable topographies and distinct surface characteristics. Hence, different types of nanotube arrays can be modified for various applications. Full article

(This article belongs to the Special Issue Growth, Characterization and Applications of Nanotubes)

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13 pages, 3454 KiB

Open AccessArticle

Photoacoustic Properties of Polypyrrole Nanoparticles

by Peter Keša, Monika Paúrová, Michal Babič, Tomáš Heizer, Petr Matouš, Karolína Turnovcová, Dana Mareková, Luděk Šefc and Vít Herynek

Nanomaterials 2021, 11(9), 2457; https://doi.org/10.3390/nano11092457 - 21 Sep 2021

Cited by 10 | Viewed by 2858

Abstract

Photoacoustic imaging, an emerging modality, provides supplemental information to ultrasound imaging. We investigated the properties of polypyrrole nanoparticles, which considerably enhance contrast in photoacoustic images, in relation to the synthesis procedure and to their size. We prepared polypyrrole nanoparticles by water-based redox precipitation [...] Read more.

Photoacoustic imaging, an emerging modality, provides supplemental information to ultrasound imaging. We investigated the properties of polypyrrole nanoparticles, which considerably enhance contrast in photoacoustic images, in relation to the synthesis procedure and to their size. We prepared polypyrrole nanoparticles by water-based redox precipitation polymerization in the presence of ammonium persulphate (ratio nPy:nOxi 1:0.5, 1:1, 1:2, 1:3, 1:5) or iron(III) chloride (nPy:nOxi 1:2.3) acting as an oxidant. To stabilize growing nanoparticles, non-ionic polyvinylpyrrolidone was used. The nanoparticles were characterized and tested as a photoacoustic contrast agent in vitro on an imaging platform combining ultrasound and photoacoustic imaging. High photoacoustic signals were obtained with lower ratios of the oxidant (nPy:nAPS ≥ 1:2), which corresponded to higher number of conjugated bonds in the polymer. The increasing portion of oxidized structures probably shifted the absorption spectra towards shorter wavelengths. A strong photoacoustic signal dependence on the nanoparticle size was revealed; the signal linearly increased with particle surface. Coated nanoparticles were also tested in vivo on a mouse model. To conclude, polypyrrole nanoparticles represent a promising contrast agent for photoacoustic imaging. Variations in the preparation result in varying photoacoustic properties related to their structure and allow to optimize the nanoparticles for in vivo imaging. Full article

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16 pages, 4448 KiB

Open AccessArticle

3D Printed Multi-Functional Scaffolds Based on Poly(ε-Caprolactone) and Hydroxyapatite Composites

by Fan Liu, Honglei Kang, Zhiwei Liu, Siyang Jin, Guoping Yan, Yunlong Sun, Feng Li, Haifei Zhan and Yuantong Gu

Nanomaterials 2021, 11(9), 2456; https://doi.org/10.3390/nano11092456 - 21 Sep 2021

Cited by 19 | Viewed by 2991

Abstract

3D Printed biodegradable polymeric scaffolds are critical to repair a bone defect, which can provide the individual porous and network microenvironments for cell attachment and bone tissue regeneration. Biodegradable PCL/HA composites were prepared with the blending of poly(ε-caprolactone) (PCL) and hydroxyapatite nanoparticles (HA). [...] Read more.

3D Printed biodegradable polymeric scaffolds are critical to repair a bone defect, which can provide the individual porous and network microenvironments for cell attachment and bone tissue regeneration. Biodegradable PCL/HA composites were prepared with the blending of poly(ε-caprolactone) (PCL) and hydroxyapatite nanoparticles (HA). Subsequently, the PCL/HA scaffolds were produced by the melting deposition-forming method using PCL/HA composites as the raw materials in this work. Through a serial of in vitro assessments, it was found that the PCL/HA composites possessed good biodegradability, low cell cytotoxicity, and good biocompatibility, which can improve the cell proliferation of osteoblast cells MC3T3-E1. Meanwhile, in vivo experiments were carried out for the rats with skull defects and rabbits with bone defects. It was observed that the PCL/HA scaffolds allowed the adhesion and penetration of bone cells, which enabled the growth of bone cells and bone tissue regeneration. With a composite design to load an anticancer drug (doxorubicin, DOX) and achieve sustained drug release performance, the multifunctional 3D printed PCL/HA/DOX scaffolds can enhance bone repair and be expected to inhibit probably the tumor cells after malignant bone tumor resection. Therefore, this work signifies that PCL/HA composites can be used as the potential biodegradable scaffolds for bone repairing. Full article

(This article belongs to the Special Issue Nanomechanics and Plasticity)

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15 pages, 5683 KiB

Open AccessArticle

Cytostatic and Cytotoxic Effects of Hollow-Shell Mesoporous Silica Nanoparticles Containing Magnetic Iron Oxide

by Manuel Pérez-Garnes, Victoria Morales, Raul Sanz and Rafael A. García-Muñoz

Nanomaterials 2021, 11(9), 2455; https://doi.org/10.3390/nano11092455 - 21 Sep 2021

Cited by 15 | Viewed by 3157

Abstract

Among the different types of nanoparticles used in biomedical applications, Fe nanoparticles and mesoporous siliceous materials have been extensively investigated because of their possible theranostic applications. Here, we present hollow-shell mesoporous silica nanoparticles that encapsulate iron oxide and that are prepared using a [...] Read more.

Among the different types of nanoparticles used in biomedical applications, Fe nanoparticles and mesoporous siliceous materials have been extensively investigated because of their possible theranostic applications. Here, we present hollow-shell mesoporous silica nanoparticles that encapsulate iron oxide and that are prepared using a drug-structure-directing agent concept (DSDA), composed of the model drug tryptophan modified by carbon aliphatic hydrocarbon chains. The modified tryptophan can behave as an organic template that allows directing the hollow-shell mesoporous silica framework, as a result of its micellisation and subsequent assembly of the silica around it. The one-pot synthesis procedure facilitates the incorporation of hydrophobically stabilised iron oxide nanoparticles into the hollow internal silica cavities, with the model drug tryptophan in the shell pores, thus enabling the incorporation of different functionalities into the all-in-one nanoparticles named mesoporous silica nanoparticles containing magnetic iron oxide (Fe₃O₄@MSNs). Additionally, the drug loading capability and the release of tryptophan from the silica nanoparticles were examined, as well as the cytostaticity and cytotoxicity of the Fe₃O₄@MSNs in different colon cancer cell lines. The results indicate that Fe₃O₄@MSNs have great potential for drug loading and drug delivery into specific target cells, thereby overcoming the limitations associated with conventional drug formulations, which are unable to selectively reach the sites of interest. Full article

(This article belongs to the Special Issue Silica Nanoparticles as Safety Nanocarriers)

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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 57 | Viewed by 5032

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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19 pages, 6311 KiB

Open AccessArticle

Iron Oxide/Polymer Core–Shell Nanomaterials with Star-like Behavior

by Virginie Vergnat, Benoît Heinrich, Michel Rawiso, René Muller, Geneviève Pourroy and Patrick Masson

Nanomaterials 2021, 11(9), 2453; https://doi.org/10.3390/nano11092453 - 21 Sep 2021

Cited by 4 | Viewed by 2979

Abstract

Embedding nanoparticles (NPs) with organic shells is a way to control their aggregation behavior. Using polymers allows reaching relatively high shell thicknesses but suffers from the difficulty of obtaining regular hybrid objects at gram scale. Here, we describe a three-step synthesis in which [...] Read more.

Embedding nanoparticles (NPs) with organic shells is a way to control their aggregation behavior. Using polymers allows reaching relatively high shell thicknesses but suffers from the difficulty of obtaining regular hybrid objects at gram scale. Here, we describe a three-step synthesis in which multi-gram NP batches are first obtained by thermal decomposition, prior to their covalent grafting by an atom transfer radical polymerization (ATRP) initiator and to the controlled growing of the polymer shell. Specifically, non-aggregated iron oxide NPs with a core principally composed of γ-Fe₂O₃ (maghemite) and either polystyrene (PS) or polymethyl methacrylate (PMMA) shell were elaborated. The oxide cores of about 13 nm diameter were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). After the polymerization, the overall diameter reached 60 nm, as shown by small-angle neutron scattering (SANS). The behavior in solution as well as rheological properties in the molten state of the polymeric shell resemble those of star polymers. Strategies to further improve the screening of NP cores with the polymer shells are discussed. Full article

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20 pages, 12615 KiB

Open AccessArticle

Hydroxyapatite-Based Solution as Adjunct Treatment for Biofilm Management: An In Situ Study

by Cíntia M. G. Nobre, Belinda König, Norbert Pütz and Matthias Hannig

Nanomaterials 2021, 11(9), 2452; https://doi.org/10.3390/nano11092452 - 21 Sep 2021

Cited by 11 | Viewed by 2336

Abstract

Synthetic hydroxyapatite-based solution is a bioinspired material that may present anti-adhesive properties, restraining the dental biofilm formation without causing adverse effects. This in situ study aims to evaluate the effects of three different hydroxyapatite (HAP) watery solutions as a mouthwash against biofilm adhesion [...] Read more.

Synthetic hydroxyapatite-based solution is a bioinspired material that may present anti-adhesive properties, restraining the dental biofilm formation without causing adverse effects. This in situ study aims to evaluate the effects of three different hydroxyapatite (HAP) watery solutions as a mouthwash against biofilm adhesion on different dental material surfaces under oral conditions. Hence, four volunteers carried maxillary splints containing enamel, titanium, ceramics, and polymethyl-methacrylate resin (PMMA) samples. Three HAP watery solutions (5%) were prepared with HAP particles presenting different shapes and sizes (HAP I, HAP II, HAP III). During 24 h, the volunteers rinsed two times with one of the following selected tested solution: HAP I, HAP II, HAP III, water, or chlorhexidine 0.2% (CHX). The first rinse was performed 3 min after pellicle formation; the second rinse occurred after a 12 h interval. The surface analysis was performed by scanning electron microscopy (SEM), fluorescence microscopy (FM), and transmission electron microscopy (TEM). Statistical and microscopic analysis showed that most samples treated with any HAP solution revealed reduced biofilm coverage presenting comparable results to CHX treated samples, however without altering the microorganisms’ viability. In conclusion, the results of this investigation showed that a pure hydroxyapatite-based mouthrinse could be a promising bioinspired adjunct solution for biofilm management. Full article

(This article belongs to the Special Issue Nanomaterials and Microorganisms)

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7 pages, 1530 KiB

Open AccessArticle

Deformation Twinning Induced High Tensile Ductility of a Gradient Nanograined Cu-Based Alloy

by Junjie Wang and Nairong Tao

Nanomaterials 2021, 11(9), 2451; https://doi.org/10.3390/nano11092451 - 20 Sep 2021

Cited by 1 | Viewed by 1999

Abstract

We investigated the tensile properties of gradient nanograined Cu and CuAl samples prepared by plastic deformation. Tensile tests showed that the gradient nanograined Cu-4.5Al sample exhibits a uniform elongation of ~22% without any cracks, while the uniform elongation of the gradient nanograined Cu [...] Read more.

We investigated the tensile properties of gradient nanograined Cu and CuAl samples prepared by plastic deformation. Tensile tests showed that the gradient nanograined Cu-4.5Al sample exhibits a uniform elongation of ~22% without any cracks, while the uniform elongation of the gradient nanograined Cu sample is only ~18%. Numerous mechanical twinning retards the softening of the nanograins and accommodates a high tensile ductility in the gradient nanograined Cu-4.5Al sample. This work indicates that mechanical twinning is a potential deformation mechanism to achieve high tensile ductility of nanograined materials. Full article

(This article belongs to the Special Issue Gradient Nanograined Materials)

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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 2 | Viewed by 3173

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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23 pages, 3002 KiB

Open AccessReview

Recent Advances in Gadolinium Based Contrast Agents for Bioimaging Applications

by Atiya Fatima, Md. Wasi Ahmad, Abdullah Khamis Ali Al Saidi, Arup Choudhury, Yongmin Chang and Gang Ho Lee

Nanomaterials 2021, 11(9), 2449; https://doi.org/10.3390/nano11092449 - 20 Sep 2021

Cited by 45 | Viewed by 6295

Abstract

Gadolinium (Gd) based contrast agents (CAs) (Gd-CAs) represent one of the most advanced developments in the application of Gd for magnetic resonance imaging (MRI). Current challenges with existing CAs generated an urgent requirement to develop multimodal CAs with good biocompatibility, low toxicity, and [...] Read more.

Gadolinium (Gd) based contrast agents (CAs) (Gd-CAs) represent one of the most advanced developments in the application of Gd for magnetic resonance imaging (MRI). Current challenges with existing CAs generated an urgent requirement to develop multimodal CAs with good biocompatibility, low toxicity, and prolonged circulation time. This review discussed the Gd-CAs used in bioimaging applications, addressing their advantages and limitations. Future research is required to establish the safety, efficacy and theragnostic capabilities of Gd-CAs. Nevertheless, these Gd-CAs offer extraordinary potential as imaging CAs and promise to benefit bioimaging applications significantly. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Bioimaging)

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14 pages, 20538 KiB

Open AccessArticle

Ultrasound-Assisted Synthesis of Luminescent Micro- and Nanocrystalline Eu-Based MOFs as Luminescent Probes for Heavy Metal Ions

by Stefaniia S. Kolesnik, Viktor G. Nosov, Ilya E. Kolesnikov, Evgenia M. Khairullina, Ilya I. Tumkin, Aleksandra A. Vidyakina, Alevtina A. Sysoeva, Mikhail N. Ryazantsev, Maxim S. Panov, Vasiliy D. Khripun, Nikita A. Bogachev, Mikhail Yu. Skripkin and Andrey S. Mereshchenko

Nanomaterials 2021, 11(9), 2448; https://doi.org/10.3390/nano11092448 - 20 Sep 2021

Cited by 10 | Viewed by 4382

Abstract

The luminescent coarse-, micro- and nanocrystalline europium(III) terephthalate tetrahydrate (Eu₂bdc₃·4H₂O) metal-organic frameworks were synthesized by the ultrasound-assisted wet-chemical method. Electron micrographs show that the europium(III) terephthalate microparticles are 7 μm long leaf-like plates. According to the dynamic [...] Read more.

The luminescent coarse-, micro- and nanocrystalline europium(III) terephthalate tetrahydrate (Eu₂bdc₃·4H₂O) metal-organic frameworks were synthesized by the ultrasound-assisted wet-chemical method. Electron micrographs show that the europium(III) terephthalate microparticles are 7 μm long leaf-like plates. According to the dynamic light scattering technique, the average size of the Eu₂bdc₃·4H₂O nanoparticles is equal to about 8 ± 2 nm. Thereby, the reported Eu₂bdc₃·4H₂O nanoparticles are the smallest nanosized rare-earth-based MOF crystals, to the best of our knowledge. The synthesized materials demonstrate red emission due to the ⁵D₀–⁷F_J transitions of Eu³⁺ upon 250 nm excitation into ¹ππ* state of the terephthalate ion. Size reduction results in broadened emission bands, an increase in the non-radiative rate constants and a decrease in both the quantum efficiency of the ⁵D₀ level and Eu³⁺ and the luminescence quantum yields. Cu²⁺, Cr³⁺, and Fe³⁺ ions efficiently and selectively quench the luminescence of nanocrystalline europium(III) terephthalate, which makes it a prospective material for luminescent probes to monitor these ions in waste and drinking water. Full article

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

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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 7 | Viewed by 2885

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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14 pages, 2846 KiB

Open AccessArticle

Aptasensor for the Detection of Mycobacterium tuberculosis in Sputum Utilising CFP10-ESAT6 Protein as a Selective Biomarker

by Umi Zulaikha Mohd Azmi, Nor Azah Yusof, Jaafar Abdullah, Faruq Mohammad, Shahrul Ainliah Alang Ahmad, Siti Suraiya, Nurul Hanun Ahmad Raston, Fatin Nabilah Mohd Faudzi, Sachin K. Khiste and Hamad A. Al-Lohedan

Nanomaterials 2021, 11(9), 2446; https://doi.org/10.3390/nano11092446 - 20 Sep 2021

Cited by 13 | Viewed by 4309

Abstract

A portable electrochemical aptamer-antibody based sandwich biosensor has been designed and successfully developed using an aptamer bioreceptor immobilized onto a screen-printed electrode surface for Mycobacterium tuberculosis (M. tuberculosis) detection in clinical sputum samples. In the sensing strategy, a CFP10-ESAT6 binding aptamer [...] Read more.

A portable electrochemical aptamer-antibody based sandwich biosensor has been designed and successfully developed using an aptamer bioreceptor immobilized onto a screen-printed electrode surface for Mycobacterium tuberculosis (M. tuberculosis) detection in clinical sputum samples. In the sensing strategy, a CFP10-ESAT6 binding aptamer was immobilized onto a graphene/polyaniline (GP/PANI)-modified gold working electrode by covalent binding via glutaraldehyde linkage. Upon interaction with the CFP10-ESAT6 antigen target, the aptamer will capture the target where the nano-labelled Fe₃O₄/Au MNPs conjugated antibody is used to complete the sandwich format and enhance the signal produced from the aptamer–antigen interaction. Using this strategy, the detection of CFP10-ESAT6 antigen was conducted in the concentration range of 5 to 500 ng/mL. From the analysis, the detection limit was found to be 1.5 ng/mL, thereby demonstrating the efficiency of the aptamer as a bioreceptor. The specificity study was carried out using bovine serum albumin (BSA), MPT64, and human serum, and the result demonstrated good specificity that is 7% higher than the antibody–antigen interaction reported in a previous study. The fabricated aptasensor for M. tuberculosis analysis shows good reproducibility with an relative standard deviation (RSD) of 2.5%. Further analysis of M. tuberculosis in sputum samples have shown good correlation with the culture method with 100% specificity and sensitivity, thus making the aptasensor a promising candidate for M. tuberculosis detection considering its high specificity and sensitivity with clinical samples. Full article

(This article belongs to the Special Issue Functional Nanohybrid Material for Electrochemical Sensor Development)

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15 pages, 6204 KiB

Open AccessArticle

Mechanical Properties and Characterization of Epoxy Composites Containing Highly Entangled As-Received and Acid Treated Carbon Nanotubes

by Aaron S. Krieg, Julia A. King, Gregory M. Odegard, Timothy R. Leftwich, Leif K. Odegard, Paul D. Fraley, Ibrahim Miskioglu, Claire Jolowsky, Matthew Lundblad, Jin Gyu Park and Richard Liang

Nanomaterials 2021, 11(9), 2445; https://doi.org/10.3390/nano11092445 - 19 Sep 2021

Cited by 13 | Viewed by 3127

Abstract

Huntsman–Merrimack MIRALON^® carbon nanotubes (CNTs) are a novel, highly entangled, commercially available, and scalable format of nanotubes. As-received and acid-treated CNTs were added to aerospace grade epoxy (CYCOM^® 977-3), and the composites were characterized. The epoxy resin is expected to infiltrate [...] Read more.

Huntsman–Merrimack MIRALON^® carbon nanotubes (CNTs) are a novel, highly entangled, commercially available, and scalable format of nanotubes. As-received and acid-treated CNTs were added to aerospace grade epoxy (CYCOM^® 977-3), and the composites were characterized. The epoxy resin is expected to infiltrate the network of the CNTs and could improve mechanical properties. Epoxy composites were tested for flexural and viscoelastic properties and the as-received and acid treated CNTs were characterized using Field-Emission Scanning and Transmission Electron Microscopy, X-Ray Photoelectron Spectroscopy, and Thermogravimetric Analysis. Composites containing 0.4 wt% as-received CNTs showed an increase in flexural strength, from 136.9 MPa for neat epoxy to 147.5 MPa. In addition, the flexural modulus increased from 3.88 GPa for the neat epoxy to 4.24 GPa and 4.49 GPa for the 2.0 wt% and 3.0 wt% as-received CNT/epoxy composites, respectively. FE-SEM micrographs indicated good dispersion of the CNTs in the as-received CNT/epoxy composites and the 10 M nitric acid 6 h treatment at 120 °C CNT/epoxy composites. CNTs treated with 10 M nitric acid for 6 h at 120 °C added oxygen containing functional groups (C–O, C=O, and O=C–O) and removed iron catalyst present on the as-received CNTs, but the flexural properties were not improved compared to the as-received CNT/epoxy composites. Full article

(This article belongs to the Special Issue Design, Analysis, Manufacture and Testing of Nanocomposites)

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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 2908

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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14 pages, 2278 KiB

Open AccessArticle

Nanostructures for Achieving Selective Properties of a Thermophotovoltaic Emitter

by Lucie Šimonová, Milan Matějka, Alexandr Knápek, Tomáš Králík, Zuzana Pokorná, Filip Mika, Tomáš Fořt, Ondřej Man, Pavel Škarvada, Alexandr Otáhal and Pavel Čudek

Nanomaterials 2021, 11(9), 2443; https://doi.org/10.3390/nano11092443 - 19 Sep 2021

Cited by 1 | Viewed by 2153

Abstract

This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop [...] Read more.

This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop a new method to create very fine structures beyond the conventional standard (nanostructures), which will increase the emissivity of the base material for it to match the needs of a selective emitter for the VIS and NIR region. Available methods were used to create the nanostructures, from which we eliminated all unsuitable methods; for the selected method, we established the optimal procedure and parameters for their creation. The development of the emitter nanostructures included the necessary substrate pretreatments, where great emphasis was placed on material purity and surface roughness. Tungsten was purposely chosen as the main material for the formation of the nanostructures; we verified the effect of the formed structure on the resulting emissivity. This work presents a new method for the formation of nanostructures, which are not commonly formed in such fineness; by this, it opens the way to new possibilities for achieving the desired selectivity of the thermophotovoltaic emitter. Full article

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15 pages, 5589 KiB

Open AccessArticle

Influence of Terbium Ions and Their Concentration on the Photoluminescence Properties of Hydroxyapatite for Biomedical Applications

by Andrei Viorel Paduraru, Ovidiu Oprea, Adina Magdalena Musuc, Bogdan Stefan Vasile, Florin Iordache and Ecaterina Andronescu

Nanomaterials 2021, 11(9), 2442; https://doi.org/10.3390/nano11092442 - 19 Sep 2021

Cited by 16 | Viewed by 3244

Abstract

A new generation of biomaterials with terbium-doped hydroxyapatite was obtained using a coprecipitation method. The synthesis of new materials with luminescent properties represents a challenging but important contribution due to their potential applications in biomedical science. The main objective of this study was [...] Read more.

A new generation of biomaterials with terbium-doped hydroxyapatite was obtained using a coprecipitation method. The synthesis of new materials with luminescent properties represents a challenging but important contribution due to their potential applications in biomedical science. The main objective of this study was to revel the influence of terbium ions on the design and structure of hydroxyapatite. Different concentrations of terbium, described by the chemical formula Ca_10−xTb_x(PO₄)₆(OH)₂, where x is in the range of 0 to 1, were considered. The consequence of ion concentration on hydroxyapatite morphology was also investigated. The morphology and structure, as well as the optical properties, of the obtained nanomaterials were characterized using X-ray powder diffraction analysis (XRD), Fourier Transform Infrared spectrometry (FTIR), SEM and TEM microscopy, UV-Vis and photoluminescence spectroscopies. The measurements revealed that terbium ions were integrated into the structure of hydroxyapatite within certain compositional limits. The biocompatibility and cytotoxicity of the obtained powders evaluated using MTT assay, oxidative stress assessment and fluorescent microscopy revealed the ability of the synthesized nanomaterials to be used for biological system imaging. Full article

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20 pages, 4821 KiB

Open AccessArticle

Fabrication and Application of Zeolite/Acanthophora Spicifera Nanoporous Composite for Adsorption of Congo Red Dye from Wastewater

by Ahmed Hamd, Asmaa Ragab Dryaz, Mohamed Shaban, Hamad AlMohamadi, Khulood A. Abu Al-Ola, Nofal Khamis Soliman and Sayed A. Ahmed

Nanomaterials 2021, 11(9), 2441; https://doi.org/10.3390/nano11092441 - 19 Sep 2021

Cited by 26 | Viewed by 2807

Abstract

Systematic investigations involving laboratory, analytical, and field trials were carried out to obtain the most efficient adsorbent for the removal of congo red (CR) dye from industrial effluent. Modification of the zeolite (Z) by the Acanthophora Spicifera algae (AS; marine algae) was evaluated [...] Read more.

Systematic investigations involving laboratory, analytical, and field trials were carried out to obtain the most efficient adsorbent for the removal of congo red (CR) dye from industrial effluent. Modification of the zeolite (Z) by the Acanthophora Spicifera algae (AS; marine algae) was evaluated in terms of adsorption capability of the zeolite to remove CR dye from aqueous solution. The zeolite/algae composite (ZAS) was fabricated using the wet impregnation technique. The AS, Z, and the synthesized ZAS composite were analyzed utilizing various characterization techniques. The newly synthesized ZAS composite has an adsorption capacity that is significantly higher than that of Z and AS, particularly at low CR concentrations. Batch experiments were carried out to explore the effects of different experimental factors, as well as the dye adsorption isotherms and kinetics. Owing to the presence of intermolecular interactions, the computational analysis showed that the adsorption of the CR molecule on zeolite surfaces is exothermic, energetically favorable, and spontaneous. Furthermore, growing the zeolite surface area has no discernible effect on the adsorption energies in all configurations. The ZAS composite may be used as a low-cost substitute adsorbent for the removal of anionic dyes from industrial wastewater at lower dye concentrations, according to the experimental results. Adsorption of CR dye onto Z, AS, and ZAS adsorbents was adequately explained by pseudo-second-order kinetics and the Langmuir isotherm. The sorption mechanism was also evaluated using Weber’s intra-particle diffusion module. Finally, field testing revealed that the newly synthesized adsorbent was 98.0% efficient at extracting dyes from industrial wastewater, proving the foundation of modern eco-friendly materials that aid in the reuse of industrial wastewater. Full article

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

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12 pages, 4096 KiB

Open AccessArticle

Metal-Free Phosphated Mesoporous SiO₂ as Catalyst for the Low-Temperature Conversion of SO₂ to H₂S in Hydrogen

by Xinnan Lu, Safa Gaber, Mark A. Baker, Steven J. Hinder and Kyriaki Polychronopoulou

Nanomaterials 2021, 11(9), 2440; https://doi.org/10.3390/nano11092440 - 18 Sep 2021

Cited by 1 | Viewed by 1925

Abstract

Highly active metal-free mesoporous phosphated silica was synthesized by a two-step process and used as a SO₂ hydrogenation catalyst. With the assistance of a microwave, MCM-41 was obtained within a 10 min heating process at 180 °C, then a low ratio of [...] Read more.

Highly active metal-free mesoporous phosphated silica was synthesized by a two-step process and used as a SO₂ hydrogenation catalyst. With the assistance of a microwave, MCM-41 was obtained within a 10 min heating process at 180 °C, then a low ratio of P precursor was incorporated into the mesoporous silica matrix by a phosphorization step, which was accomplished in oleylamine with trioctylphosphine at 350 °C for 2 h. For benchmarking, the SiO₂ sample without P precursor insertion and the sample with P precursor insertion into the calcined SiO₂ were also prepared. From the microstructural analysis, it was found that the presence of CTAB surfactant was important for the incorporation of active P species, thus forming a highly dispersed, ultrafine (uf) phosphate silica, (Si-P) catalyst. The above approach led to the promising catalytic performance of uf-P@meso-SiO₂ in the selective hydrogenation of SO₂ to H₂S; the latter reaction is very important in sulfur-containing gas purification. In particular, uf-P@meso-SiO₂ exhibited activity at the temperature range between 150 and 280 °C, especially SO₂ conversion of 94% and H₂S selectivity of 52% at 220 °C. The importance of the CTAB surfactant can be found in stabilizing the high dispersion of ultrafine P-related species (phosphates). Intrinsic characteristics of the materials were studied using XRD, FTIR, EDX, N₂ adsorption/desorption, TEM, and XPS to reveal the structure of the above catalysts. Full article

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21 pages, 6763 KiB

Open AccessArticle

Radiation Synthesis of Selenium Nanoparticles Capped with β-Glucan and Its Immunostimulant Activity in Cytoxan-Induced Immunosuppressed Mice

by Nguyen Thi Dung, Tran Duc Trong, Nguyen Thanh Vu, Nguyen Trong Binh, Tran Thi Le Minh and Le Quang Luan

Nanomaterials 2021, 11(9), 2439; https://doi.org/10.3390/nano11092439 - 18 Sep 2021

Cited by 9 | Viewed by 3133

Abstract

Selenium nanoparticles (SeNPs) with diameters from 64.8 to 110.1 nm were successfully synthesized by γ-irradiation of solutions containing Se⁴⁺ and water-soluble yeast β-glucan. The size and size distribution of SeNPs were analyzed by dynamic light scattering (DLS). Analytical X-ray diffraction (XRD) [...] Read more.

Selenium nanoparticles (SeNPs) with diameters from 64.8 to 110.1 nm were successfully synthesized by γ-irradiation of solutions containing Se⁴⁺ and water-soluble yeast β-glucan. The size and size distribution of SeNPs were analyzed by dynamic light scattering (DLS). Analytical X-ray diffraction (XRD) pattern results confirmed the crystal structure of the Se nanoparticles and Fourier transform infrared (FTIR) spectroscopy revealed that β-glucan could interact with SeNPs through steric (Se…O) linkages leading to a homogeneous and translucent solution state for 60 days without any precipitates. In vivo tests in cytoxan-induced immunosuppressed mice revealed that the daily supplementation of SeNPs/β-glucan at concentrations of 6 mg per kg body weight of tested mice significantly stimulated the generation of cellular immune factors (white blood cells, neutrophil, lymphocyte, B cells, CD4+ cells, CD34+ cells and natural killer cells) and humoral immune indexes (IgM, IgG, TNF-α, IFN-γ and IL-2) in peripheral blood, bone marrow and spleen of the immunosuppressed mice. The obtained results indicated that radiation-synthesized SeNPs/β-glucan may be a candidate for further evaluation as an agent for the prevention of immunosuppression in chemotherapy. Full article

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16 pages, 2546 KiB

Open AccessArticle

Chitosan-Coated PLGA Nanoparticles Loaded with Peganum harmala Alkaloids with Promising Antibacterial and Wound Healing Activities

by Hassan Mohamed El-Said Azzazy, Sherif Ashraf Fahmy, Noha Khalil Mahdy, Meselhy Ragab Meselhy and Udo Bakowsky

Nanomaterials 2021, 11(9), 2438; https://doi.org/10.3390/nano11092438 - 18 Sep 2021

Cited by 41 | Viewed by 4507

Abstract

Wound healing is a major healthcare concern, and complicated wounds may lead to severe outcomes such as septicemia and amputations. To date, management choices are limited, which warrants the search for new potent wound healing agents. Natural products loaded in poly (lactic-co-glycolic acid) [...] Read more.

Wound healing is a major healthcare concern, and complicated wounds may lead to severe outcomes such as septicemia and amputations. To date, management choices are limited, which warrants the search for new potent wound healing agents. Natural products loaded in poly (lactic-co-glycolic acid) (PLGA) coated with chitosan (CS) constitute a promising antibacterial wound healing formulation. In this work, harmala alkaloid-rich fraction (HARF) loaded into PLGA nanoparticles coated with chitosan (H/CS/PLGA NPs) were designed using the emulsion-solvent evaporation method. Optimization of the formulation variables (HARF: PLGA and CS: PLGA weight ratios, sonication time) was performed using the 3³ Box–Behnken design (BBD). The optimal NPs were characterized using transmission electron microscopy (TEM) and Attenuated Total Reflection Fourier-Transformed Infrared Spectroscopy (ATR-FTIR). The prepared NPs had an average particle size of 202.27 ± 2.44 nm, a PDI of 0.23 ± 0.01, a zeta potential of 9.22 ± 0.94 mV, and an entrapment efficiency of 86.77 ± 4.18%. In vitro drug release experiments showed a biphasic pattern where an initial burst of 82.50 ± 0.20% took place in the first 2 h, which increased to 87.50 ± 0.50% over 72 h. The designed optimal H/CS/PLGA NPs exerted high antibacterial activity against Staphylococcus aureus and Escherichia coli (MIC of 0.125 and 0.06 mg/mL, respectively) compared to unloaded HARF (MIC of 0.50 mg/mL). The prepared nanoparticles were found to be biocompatible when tested on human skin fibroblasts. Moreover, the wound closure percentage after 24 h of applying H/CS/PLGA NPs was found to be 94.4 ± 8.0%, compared to free HARF and blank NPs (68.20 ± 5.10 and 50.50 ± 9.40%, respectively). In conclusion, the three components of the developed nanoformulation (PLGA, chitosan, and HARF) have synergistic antibacterial and wound healing properties for the management of infected wounds. Full article

(This article belongs to the Special Issue Functional Polymeric Nanoparticles)

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12 pages, 3531 KiB

Open AccessArticle

Gradient Enhanced Strain Hardening and Tensile Deformability in a Gradient-Nanostructured Ni Alloy

by Xinlai An, Weikang Bao, Zuhe Zhang, Zhouwen Jiang, Shengyun Yuan, Zesheng You and Yong Zhang

Nanomaterials 2021, 11(9), 2437; https://doi.org/10.3390/nano11092437 - 18 Sep 2021

Cited by 4 | Viewed by 2306

Abstract

Gradient-nanostructured material is an emerging category of material with spatial gradients in microstructural features. The incompatibility between gradient nanostructures (GNS) in the surface layer and coarse-grained (CG) core and their roles in extra strengthening and strain hardening have been well elucidated. Nevertheless, whether [...] Read more.

Gradient-nanostructured material is an emerging category of material with spatial gradients in microstructural features. The incompatibility between gradient nanostructures (GNS) in the surface layer and coarse-grained (CG) core and their roles in extra strengthening and strain hardening have been well elucidated. Nevertheless, whether similar mechanisms exist within the GNS is not clear yet. Here, interactions between nanostructured layers constituting the GNS in a Ni alloy processed by surface mechanical rolling treatment were investigated by performing unique microtension tests on the whole GNS and three subdivided nanostructured layers at specific depths, respectively. The isolated nanograined layer at the topmost surface shows the highest strength but a brittle nature. With increasing depths, isolated layers exhibit lower strength but enhanced tensile plasticity. The GNS sample’s behavior complied more with the soft isolated layer at the inner side of GNS. Furthermore, an extra strain hardening was found in the GNS sample, leading to a greater uniform elongation (>3%) as compared to all of three constituent nanostructured layers. This extra strain hardening could be ascribed to the effects of the strain gradients arising from the incompatibility associated with the depth-dependent mechanical performance of various nanostructured layers. Full article

(This article belongs to the Special Issue Gradient Nanograined Materials)

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11 pages, 3909 KiB

Open AccessArticle

One-Pot Synthesis of Chlorophyll-Assisted Exfoliated MoS₂/WS₂ Heterostructures via Liquid-Phase Exfoliation Method for Photocatalytic Hydrogen Production

by I-Wen P. Chen, Yan-Ming Lai and Wei-Sheng Liao

Nanomaterials 2021, 11(9), 2436; https://doi.org/10.3390/nano11092436 - 18 Sep 2021

Cited by 9 | Viewed by 2919

Abstract

Developing strategies for producing hydrogen economically and in greener ways is still an unaccomplished goal. Photoelectrochemical (PEC) water splitting using photoelectrodes under neutral electrolyte conditions provides possibly one of the greenest routes to produce hydrogen. Here, we demonstrate that chlorophyll extracts can be [...] Read more.

Developing strategies for producing hydrogen economically and in greener ways is still an unaccomplished goal. Photoelectrochemical (PEC) water splitting using photoelectrodes under neutral electrolyte conditions provides possibly one of the greenest routes to produce hydrogen. Here, we demonstrate that chlorophyll extracts can be used as an efficient exfoliant to exfoliate bulk MoS₂ and WS₂ to form a thin layer of a MoS₂/WS₂ heterostructure. Thin films of solution-processed MoS₂ and WS₂ nanosheets display photocurrent densities of −1 and −5 mA/cm², respectively, and hydrogen evolution under simulated solar irradiation. The exfoliated WS₂ is significantly more efficient than the exfoliated MoS₂; however, the MoS₂/WS₂ heterostructure results in a 2500% increase in photocurrent densities compared to the individual constituents and over 12 h of PEC durability under a neutral electrolyte. Surprisingly, in real seawater, the MoS₂/WS₂ heterostructure exhibits stable hydrogen production after solar illumination for 12 h. The synthesis method showed, for the first time, how the MoS₂/WS₂ heterostructure can be used to produce hydrogen effectively. Our findings highlight the prospects for this heterostructure, which could be coupled with various processes towards improving PEC efficiency and applications. Full article

(This article belongs to the Special Issue Transition Metal Dichalcogenides: From Fundamentals to Nanoelectronics)

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18 pages, 4934 KiB

Open AccessArticle

Low-Energy Electron Inelastic Mean Free Path of Graphene Measured by a Time-of-Flight Spectrometer

by Ivo Konvalina, Benjamin Daniel, Martin Zouhar, Aleš Paták, Ilona Müllerová, Luděk Frank, Jakub Piňos, Lukáš Průcha, Tomáš Radlička, Wolfgang S. M. Werner and Eliška Materna Mikmeková

Nanomaterials 2021, 11(9), 2435; https://doi.org/10.3390/nano11092435 - 18 Sep 2021

Cited by 8 | Viewed by 3200

Abstract

The detailed examination of electron scattering in solids is of crucial importance for the theory of solid-state physics, as well as for the development and diagnostics of novel materials, particularly those for micro- and nanoelectronics. Among others, an important parameter of electron scattering [...] Read more.

The detailed examination of electron scattering in solids is of crucial importance for the theory of solid-state physics, as well as for the development and diagnostics of novel materials, particularly those for micro- and nanoelectronics. Among others, an important parameter of electron scattering is the inelastic mean free path (IMFP) of electrons both in bulk materials and in thin films, including 2D crystals. The amount of IMFP data available is still not sufficient, especially for very slow electrons and for 2D crystals. This situation motivated the present study, which summarizes pilot experiments for graphene on a new device intended to acquire electron energy-loss spectra (EELS) for low landing energies. Thanks to its unique properties, such as electrical conductivity and transparency, graphene is an ideal candidate for study at very low energies in the transmission mode of an electron microscope. The EELS are acquired by means of the very low-energy electron microspectroscopy of 2D crystals, using a dedicated ultra-high vacuum scanning low-energy electron microscope equipped with a time-of-flight (ToF) velocity analyzer. In order to verify our pilot results, we also simulate the EELS by means of density functional theory (DFT) and the many-body perturbation theory. Additional DFT calculations, providing both the total density of states and the band structure, illustrate the graphene loss features. We utilize the experimental EELS data to derive IMFP values using the so-called log-ratio method. Full article

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

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