Nanomaterials

15 pages, 3779 KiB

Open AccessArticle

Anchoring Gated Mesoporous Silica Particles to Ethylene Vinyl Alcohol Films for Smart Packaging Applications

by Virginia Muriel-Galet, Édgar Pérez-Esteve, María Ruiz-Rico, Ramón Martínez-Máñez, José Manuel Barat, Pilar Hernández-Muñoz and Rafael Gavara

Nanomaterials 2018, 8(10), 865; https://doi.org/10.3390/nano8100865 - 22 Oct 2018

Cited by 7 | Viewed by 4577

Abstract

This work is a proof of concept for the design of active packaging materials based on the anchorage of gated mesoporous silica particles with a pH triggering mechanism to a packaging film surface. Mesoporous silica micro- and nanoparticles were loaded with rhodamine B [...] Read more.

This work is a proof of concept for the design of active packaging materials based on the anchorage of gated mesoporous silica particles with a pH triggering mechanism to a packaging film surface. Mesoporous silica micro- and nanoparticles were loaded with rhodamine B and functionalized with N-(3-trimethoxysilylpropyl)diethylenetriamine. This simple system allows regulation of cargo delivery as a function of the pH of the environment. In parallel, poly(ethylene-co-vinyl alcohol) films, EVOH 32 and EVOH 44, were ultraviolet (UV) irradiated to convert hydroxyl moieties of the polymer chains into –COOH functional groups. The highest COOH surface concentration was obtained for EVOH 32 after 15 min of UV irradiation. Anchoring of the gated mesoporous particles to the films was carried out successfully at pH 3 and pH 5. Mesoporous particles were distributed homogeneously throughout the film surface and in greater concentration for the EVOH 32 films. Films with the anchored particles were exposed to two liquid media simulating acidic food and neutral food. The films released the cargo at neutral pH but kept the dye locked at acidic pH. The best results were obtained for EVOH 32 irradiated for 15 min, treated for particle attachment at pH 3, and with mesoporous silica nanoparticles. This opens the possibility of designing active materials loaded with antimicrobials, antioxidants, or aromatic compounds, which are released when the pH of the product approaches neutrality, as occurs, for instance, with the release of biogenic amines from fresh food products. Full article

(This article belongs to the Special Issue Food Packaging Based on Nanomaterials)

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10 pages, 1826 KiB

Open AccessArticle

Investigation of the Microstructures of Graphene Quantum Dots (GQDs) by Surface-Enhanced Raman Spectroscopy

by Junxiao Wu, Peijie Wang, Fuhe Wang and Yan Fang

Nanomaterials 2018, 8(10), 864; https://doi.org/10.3390/nano8100864 - 22 Oct 2018

Cited by 93 | Viewed by 7213

Abstract

Photoluminescence (PL) is the most significant feature of graphene quantum dots (GQDs). However, the PL mechanism in GQDs has been debated due to the fact that the microstructures, such as edge and in-plane defects that are critical for PL emission, have not been [...] Read more.

Photoluminescence (PL) is the most significant feature of graphene quantum dots (GQDs). However, the PL mechanism in GQDs has been debated due to the fact that the microstructures, such as edge and in-plane defects that are critical for PL emission, have not been convincingly identified due to the lack of effective detection methods. Conventional measures such as high-resolution transmission electron microscopy and infrared spectroscopy only show some localized lattice fringes of GQDs and the structures of some substituents, which have little significance in terms of thoroughly understanding the PL effect. Here, surface-enhanced Raman spectroscopy (SERS) was introduced as a highly sensitive surface technique to study the microstructures of GQDs. Pure GQDs were prepared by laser ablating and cutting highly oriented pyrolytic graphite (HOPG) parallel to the graphite layers. Consequently, abundant SERS signals of the GQDs were obtained on an Ag electrode in an electrochemical environment for the first time. The results convincingly and experimentally characterized the typical and detailed features of GQDs, such as the crystallinity of sp² hexagons, the quantum confinement effect, various defects on the edges, sp³-like defects and disorders on the basal planes, and passivated structures on the periphery and surface of the GQDs. This work demonstrates that SERS is thus by far the most effective technique for probing the microstructures of GQDs. Full article

(This article belongs to the Special Issue Surface Enhanced Raman Spectroscopy in Nano-World)

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11 pages, 3326 KiB

Open AccessArticle

Sacrificial Core-Based Electrospinning: A Facile and Versatile Approach to Fabricate Devices for Potential Cell and Tissue Encapsulation Applications

by Naresh Kasoju, Julian George, Hua Ye and Zhanfeng Cui

Nanomaterials 2018, 8(10), 863; https://doi.org/10.3390/nano8100863 - 21 Oct 2018

Cited by 13 | Viewed by 3892

Abstract

Electrospinning uses an electric field to produce fine fibers of nano and micron scale diameters from polymer solutions. Despite innovation in jet initiation, jet path control and fiber collection, it is common to only fabricate planar and tubular-shaped electrospun products. For applications that [...] Read more.

Electrospinning uses an electric field to produce fine fibers of nano and micron scale diameters from polymer solutions. Despite innovation in jet initiation, jet path control and fiber collection, it is common to only fabricate planar and tubular-shaped electrospun products. For applications that encapsulate cells and tissues inside a porous container, it is useful to develop biocompatible hollow core-containing devices. To this end, by introducing a 3D-printed framework containing a sodium chloride pellet (sacrificial core) as the collector and through post-electrospinning dissolution of the sacrificial core, we demonstrate that hollow core containing polyamide 66 (nylon 66) devices can be easily fabricated for use as cell encapsulation systems. ATR-FTIR and TG/DTA studies were used to verify that the bulk properties of the electrospun device were not altered by contact with the salt pellet during fiber collection. Protein diffusion investigations demonstrated that the capsule allowed free diffusion of model biomolecules (insulin, albumin and Ig G). Cell encapsulation studies with model cell types (fibroblasts and lymphocytes) revealed that the capsule supports the viability of encapsulated cells inside the capsule whilst compartmentalizing immune cells outside of the capsule. Taken together, the use of a salt pellet as a sacrificial core within a 3D printed framework to support fiber collection, as well as the ability to easily remove this core using aqueous dissolution, results in a biocompatible device that can be tailored for use in cell and tissue encapsulation applications. Full article

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

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28 pages, 13716 KiB

Open AccessArticle

Laser Alloying Advantages by Dry Coating Metallic Powder Mixtures with SiO_x Nanoparticles

by Michael C. H. Karg, Michael Rasch, Konstantin Schmidt, Sophia A. E. Spitzer, Till F. Karsten, Daniel Schlaug, Cosmin-Rudolf Biaciu, Andrey I. Gorunov and Michael Schmidt

Nanomaterials 2018, 8(10), 862; https://doi.org/10.3390/nano8100862 - 21 Oct 2018

Cited by 14 | Viewed by 6206

Abstract

Up to now, minimizing segregation of free-flowing, microscale metal powder mixtures driven by different mass density is an open challenge. In this work, effects of particle size variation on homogeneity of Al-Cu mixtures, with a density ratio of 3.3, are examined. Dry coating [...] Read more.

Up to now, minimizing segregation of free-flowing, microscale metal powder mixtures driven by different mass density is an open challenge. In this work, effects of particle size variation on homogeneity of Al-Cu mixtures, with a density ratio of 3.3, are examined. Dry coating Al particles with 0.3 wt% fumed silica SiO_x nanoparticles significantly decreases interparticle attraction. This enlarges the range of free-flowing Al particle sizes to < 20 µm. Powder mixture homogeneity is examined optically in vibrated bulk powder and thinly spread layers. From various powder mixtures, solid samples are built layer by layer with the Additive Manufacturing (3D printing) technology Laser Beam Melting in metal powder bed (LBM). Chemical homogeneity of solids is evaluated via energy-dispersive X-ray spectroscopy, backscattered electron microscopy, metallographic analysis and tensile tests. Persistent homogeneity of Al-Cu powder mixtures and LBM solids is found only with particles < 20 µm dry coated with SiO_x nanoparticles. Observed segregation phenomena are explained with a decrease in particle mobility at increasing local concentration and the decreasing effectiveness of mass in smaller particles. The main effects are based on geometry, so they are expected to be transferrable to other nanoparticles, alloying components and powder bed technologies, e.g., binder jetting. Full article

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11 pages, 16194 KiB

Open AccessArticle

From Hollow to Solid Carbon Spheres: Time-Dependent Facile Synthesis

by Wojciech Kukułka, Karolina Wenelska, Martyna Baca, Xuecheng Chen and Ewa Mijowska

Nanomaterials 2018, 8(10), 861; https://doi.org/10.3390/nano8100861 - 20 Oct 2018

Cited by 23 | Viewed by 6365

Abstract

Here, we report a facile route for obtaining carbon spheres with fully tunable shell thickness. Using a hard template in chemical vapor deposition (CVD), hollow carbon spheres, solid carbon spheres, and intermediate structures can be obtained with optimized process time. The resulting carbon [...] Read more.

Here, we report a facile route for obtaining carbon spheres with fully tunable shell thickness. Using a hard template in chemical vapor deposition (CVD), hollow carbon spheres, solid carbon spheres, and intermediate structures can be obtained with optimized process time. The resulting carbon spheres with particle diameters of ~400 nm, as well as a controllable shell thickness from 0 to 70 nm, had high Brunauer–Emmett–Teller (BET) specific surface area (up to 344.8 m²·g⁻¹) and pore volume (up to 0.248 cm³·g⁻¹). The sphere formation mechanism is also proposed. This simple and reproducible technique can deliver carbon materials for various applications, e.g., energy storage and conversion, adsorption, catalytic, biomedical, and environmental applications. Full article

(This article belongs to the Special Issue Green Synthesis of Nanomaterials)

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15 pages, 4646 KiB

Open AccessArticle

Antibacterial and Bioactive Surface Modifications of Titanium Implants by PCL/TiO₂ Nanocomposite Coatings

by A. Sandeep Kranthi Kiran, T.S. Sampath Kumar, Rutvi Sanghavi, Mukesh Doble and Seeram Ramakrishna

Nanomaterials 2018, 8(10), 860; https://doi.org/10.3390/nano8100860 - 20 Oct 2018

Cited by 73 | Viewed by 6384

Abstract

Surface modification of biomedical implants is an established strategy to improve tissue regeneration, osseointegration and also to minimize the bacterial accumulation. In the present study, electrospun poly(ε-caprolactone)/titania (PCL/TiO₂) nanocomposite coatings were developed on commercially pure titanium (cpTi) substrates for an improved [...] Read more.

Surface modification of biomedical implants is an established strategy to improve tissue regeneration, osseointegration and also to minimize the bacterial accumulation. In the present study, electrospun poly(ε-caprolactone)/titania (PCL/TiO₂) nanocomposite coatings were developed on commercially pure titanium (cpTi) substrates for an improved biological and antibacterial properties for bone tissue engineering. TiO₂ nanoparticles in various amounts (2, 5, and 7 wt %) were incorporated into a biodegradable PCL matrix to form a homogeneous solution. Further, PCL/TiO₂ coatings on cpTi were obtained by electrospinning of PCL/TiO₂ solution onto the substrate. The resulted coatings were structurally characterized and inspected by employing scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Given the potential biological applications of PCL/TiO₂ coated cpTi substrates, the apatite-forming capacity was examined by immersing in simulated body fluid (SBF) for upto 21 days. Biocompatibility has been evaluated through adhesion/proliferation of hFOB osteoblast cell lines and cytotoxicity by MTT assay. Antimicrobial activity of PCL/TiO₂ nanocomposites has been tested using UV light against gram-positive Staphylococcus aureus (S.aureus). The resulting surface displays good bioactive properties against osteoblast cell lines with increased viability of 40% at day 3 and superior antibacterial property against S.aureus with a significant reduction of bacteria to almost 76%. Surface modification by PCL/TiO₂ nanocomposites makes a viable approach for improving dual properties, i.e., biological and antibacterial properties on titanium implants which might be used to prevent implant-associated infections and promoting cell attachment of orthopedic devices at the same time. Full article

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

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14 pages, 2313 KiB

Open AccessArticle

Ultrasonic Irradiation Coupled with Microwave Treatment for Eco-friendly Process of Isolating Bacterial Cellulose Nanocrystals

by Endarto Yudo Wardhono, Hadi Wahyudi, Sri Agustina, François Oudet, Mekro Permana Pinem, Danièle Clausse, Khashayar Saleh and Erwann Guénin

Nanomaterials 2018, 8(10), 859; https://doi.org/10.3390/nano8100859 - 20 Oct 2018

Cited by 26 | Viewed by 4908

Abstract

The isolation of crystalline regions from fibers cellulose via the hydrolysis route generally requires corrosive chemicals, high-energy demands, and long reaction times, resulting in high economic costs and environmental impact. From this basis, this work seeks to develop environment-friendly processes for the production [...] Read more.

The isolation of crystalline regions from fibers cellulose via the hydrolysis route generally requires corrosive chemicals, high-energy demands, and long reaction times, resulting in high economic costs and environmental impact. From this basis, this work seeks to develop environment-friendly processes for the production of Bacterial Cellulose Nanocrystals (BC-NC). To overcome the aforementioned issues, this study proposes a fast, highly-efficient and eco-friendly method for the isolation of cellulose nanocrystals from Bacterial Cellulose, BC. A two-step processes is considered: (1) partial depolymerization of Bacterial Cellulose (DP-BC) under ultrasonic conditions; (2) extraction of crystalline regions (BC-NC) by treatment with diluted HCl catalyzed by metal chlorides (MnCl₂ and FeCl₃.6H₂O) under microwave irradiation. The effect of ultrasonic time and reactant and catalyst concentrations on the index crystallinity (CrI), chemical structure, thermal properties, and surface morphology of DP-BC and BC-NC were evaluated. The results indicated that the ultrasonic treatment induced depolymerization of BC characterized by an increase of the CrI. The microwave assisted by MnCl₂-catalyzed mild acid hydrolysis enhanced the removal of the amorphous regions, yielding BC-NC. A chemical structure analysis demonstrated that the chemical structures of DP-BC and BC-NC remained unchanged after the ultrasonic treatment and MnCl₂-catalyzed acid hydrolysis process. Full article

(This article belongs to the Special Issue Nanomaterials to Enhance Food Quality, Safety, and Health Impact)

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14 pages, 3906 KiB

Open AccessArticle

Dispersion of Multi-Walled Carbon Nanotubes Stabilized by Humic Acid in Sustainable Cement Composites

by Yuan Gao, Hongwen Jing, Mingrui Du and Weiqiang Chen

Nanomaterials 2018, 8(10), 858; https://doi.org/10.3390/nano8100858 - 20 Oct 2018

Cited by 28 | Viewed by 5132

Abstract

Multi-walled carbon nanotubes (MWCNTs) are promising nanoreinforcing materials for cement-based composites due to their superior material properties. Dispersion of MWCNTs is key for achieving the most effective way of enhancing efficiency, which is challenging in an alkaline cementitious environment. In this study, humic [...] Read more.

Multi-walled carbon nanotubes (MWCNTs) are promising nanoreinforcing materials for cement-based composites due to their superior material properties. Dispersion of MWCNTs is key for achieving the most effective way of enhancing efficiency, which is challenging in an alkaline cementitious environment. In this study, humic acid (HA) was used to stabilize the degree of dispersion of MWCNTs in an alkaline environment. The efficiency of HA in stabilizing MWCNT dispersion in cement composites was characterized using an ultraviolet spectrophotometer. The influences of HA on the workability and mechanical properties of ordinary Portland cement (OPC) reinforced with MWCNTs were evaluated, and the results revealed that the addition of HA can improve the stability of MWCNT dispersion in an alkaline environment. A concentration of 0.12 wt.% HA/S added to MWCNT suspensions was found to perform the best for improving the dispersion of MWCNTs. The addition of HA results in a decreased workability of the OPC pastes but has little influence on the strength performance. HA can affect the mechanical properties of OPC reinforced with MWCNTs by influencing the dispersion degree of the MWCNTs. An optimum range of HA (0.05–0.10 wt.%) is required to achieve the optimum reinforcing efficiency of MWCNTs. Full article

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18 pages, 5393 KiB

Open AccessArticle

Antagonistic Effect of Azoxystrobin Poly (Lactic Acid) Microspheres with Controllable Particle Size on Colletotrichum higginsianum Sacc

by Junwei Yao, Bo Cui, Xiang Zhao, Heng Zhi, Zhanghua Zeng, Yan Wang, Changjiao Sun, Guoqiang Liu, Jinming Gao and Haixin Cui

Nanomaterials 2018, 8(10), 857; https://doi.org/10.3390/nano8100857 - 19 Oct 2018

Cited by 21 | Viewed by 4064

Abstract

Size-controlled azoxystrobin-poly (lactic acid) microspheres (MS) were prepared by an oil/water emulsion solvent evaporation approach. The hydrated mean particle sizes of the MS1, MS2, and MS3 aqueous dispersions were 130.9 nm, 353.4 nm, and 3078.0 nm, respectively. The drug loading and encapsulation efficiency [...] Read more.

Size-controlled azoxystrobin-poly (lactic acid) microspheres (MS) were prepared by an oil/water emulsion solvent evaporation approach. The hydrated mean particle sizes of the MS1, MS2, and MS3 aqueous dispersions were 130.9 nm, 353.4 nm, and 3078.0 nm, respectively. The drug loading and encapsulation efficiency of the azoxystrobin microspheres had a positive relationship with particle size. However, the release rate and percentage of cumulative release were inversely related to particle size. The smaller-sized microspheres had a greater potential to access the target mitochondria. As a result, the more severe oxidative damage of Colletotrichum higginsianum Sacc and higher antagonistic activity were induced by the smaller particle size of azoxystrobin microspheres. The 50% lethal concentrations against Colletotrichum higginsianum Sacc of MS1, MS2, and MS3 were 2.0386 μg/mL, 12.7246 μg/mL, and 21.2905 μg/mL, respectively. These findings reveal that particle size is a critical factor in increasing the bioavailability of insoluble fungicide. Full article

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16 pages, 13777 KiB

Open AccessArticle

Molecular Dynamics Simulation on B3-GaN Thin Films under Nanoindentation

by Chen Chen, Haitao Li, Henggao Xiang and Xianghe Peng

Nanomaterials 2018, 8(10), 856; https://doi.org/10.3390/nano8100856 - 19 Oct 2018

Cited by 25 | Viewed by 4168

Abstract

The B3-GaN thin film was investigated by performing large-scale molecular dynamics (MD) simulation of nanoindentation. Its plastic behavior and the corresponding mechanism were studied. Based on the analysis on indentation curve, dislocation density, and orientation dependence, it was found that the indentation depths [...] Read more.

The B3-GaN thin film was investigated by performing large-scale molecular dynamics (MD) simulation of nanoindentation. Its plastic behavior and the corresponding mechanism were studied. Based on the analysis on indentation curve, dislocation density, and orientation dependence, it was found that the indentation depths of inceptive plasticity on (001), (110), and (111) planes were consistent with the Schmid law. The microstructure evolutions during the nanoindentation under different conditions were focused, and two formation mechanisms of prismatic loop were proposed. The “lasso”-like mechanism was similar to that in the previous research, where a shear loop can translate into a prismatic loop by cross-slip; and the extended “lasso”-like mechanism was not found to be reported. Our simulation showed that the two screw components of a shear loop will glide on another loop until they encounter each other and eventually produce a prismatic dislocation loop. Full article

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13 pages, 2453 KiB

Open AccessArticle

Green Synthesis of Hydrophobic Magnetite Nanoparticles Coated with Plant Extract and Their Application as Petroleum Oil Spill Collectors

by Mahmood M. S. Abdullah, Ayman M. Atta, Hamad A. Allohedan, Hamad Z. Alkhathlan, M. Khan and Abdelrahman O. Ezzat

Nanomaterials 2018, 8(10), 855; https://doi.org/10.3390/nano8100855 - 19 Oct 2018

Cited by 49 | Viewed by 4548

Abstract

In this study, an easy, rapid and eco-friendly method was used successfully to synthesize the magnetite nanoparticles (MNPs). In order to fine-tune the synthesized MNPs for the collection of heavy crude oil spills, the particles’ surface was modified with green hydrophobic biocomponents that [...] Read more.

In this study, an easy, rapid and eco-friendly method was used successfully to synthesize the magnetite nanoparticles (MNPs). In order to fine-tune the synthesized MNPs for the collection of heavy crude oil spills, the particles’ surface was modified with green hydrophobic biocomponents that were extracted from Anthemis pseudocotula (AP). The surface modified reaction carried with that of the MNPs in the presence of n-hexane extract (APH) resulted in the formation of APH-MNPs, while in the presence of chloroform extract (APC), resulted in APC-MNPs formation. The as-formed MNPs were thoroughly characterized using transmittance electron microscopy, X-ray powder diffraction, vibrating sample magnetometer and thermogravimetric analysis. The efficiency of the surface-modified MNPs for the collection of oil spills in the presence of an external magnetic field was evaluated by taking different ratios of MNPs:crude oil. From the analysis of the results, we found that the APH-MNPs particles have higher efficiency in the collection of heavy crude oil than the corresponding APC-MNPs. Full article

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13 pages, 5245 KiB

Open AccessArticle

Dopamine Assisted One-Step Pyrolysis of Glucose for the Preparation of Porous Carbon with A High Surface Area

by Hanbo Xiao, Cheng-an Tao, Yujiao Li, Xianzhe Chen, Jian Huang and Jianfang Wang

Nanomaterials 2018, 8(10), 854; https://doi.org/10.3390/nano8100854 - 19 Oct 2018

Cited by 13 | Viewed by 5155

Abstract

Herein, a facile dopamine assisted one-pot synthesis approach is proposed for the preparation of porous carbon with a specific surface area (SSA) up to 2593 m²/g through the direct pyrolysis of a mixture of glucose, NH₄Cl, and dopamine hydrochloride [...] Read more.

Herein, a facile dopamine assisted one-pot synthesis approach is proposed for the preparation of porous carbon with a specific surface area (SSA) up to 2593 m²/g through the direct pyrolysis of a mixture of glucose, NH₄Cl, and dopamine hydrochloride (DAH). The glucose is adopted as the carbon source and foaming agent, NH₄Cl is used as the blowing agent, and DAH is served as collaborative carbon precursor as well as the nitrogen source for the first time. The effect of dopamine on the component, structure, and SSA of the as-prepared porous carbon materials are systematically studied. The moderate addition of dopamine, which influences the condensation and polymerization of glucose, matches better with ammonium salt decomposition. The SSA of porous carbon increases first and then decreases with the increasing amount of dopamine. In our case, the porous carbon produced with 5 wt% dopamine (PC-5) achieves the maximum SSA of up to 2593 m²/g. Accordingly, it also shows the greatest electrochemical performance. The PC-5 shows a capacitance of 96.7 F/g calculated from the discharge curve at 1 A/g. It also has a good capacitive rate capacity, the specific capacitance can still maintain 80%, even at a high current density of 10 A/g. Moreover, PC-5 exhibits a good cycling stability of 98.1% capacitive retention after 1000 cycles. The proposed method may show promising prospects for preparing porous carbon materials as advanced energy storage materials, storage, and catalyst supports. Full article

(This article belongs to the Special Issue Nanostructured Porous Carbon based 3D Architectures)

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16 pages, 3245 KiB

Open AccessArticle

Stereoselective Double Reduction of 3-Methyl-2-cyclohexenone, by Use of Palladium and Platinum Nanoparticles, in Tandem with Alcohol Dehydrogenase

by Francesca Coccia, Lucia Tonucci, Piero Del Boccio, Stefano Caporali, Frank Hollmann and Nicola D’Alessandro

Nanomaterials 2018, 8(10), 853; https://doi.org/10.3390/nano8100853 - 19 Oct 2018

Cited by 9 | Viewed by 3361

Abstract

The combination of metal nanoparticles (Pd or Pt NPs) with NAD-dependent thermostable alcohol dehydrogenase (TADH) resulted in the one-flask catalytic double reduction of 3-methyl-2-cyclohexenone to 3-(1S,3S)-methylcyclohexanol. In this article, some assumptions about the interactions between a chemocatalyst and a biocatalyst have been proposed. [...] Read more.

The combination of metal nanoparticles (Pd or Pt NPs) with NAD-dependent thermostable alcohol dehydrogenase (TADH) resulted in the one-flask catalytic double reduction of 3-methyl-2-cyclohexenone to 3-(1S,3S)-methylcyclohexanol. In this article, some assumptions about the interactions between a chemocatalyst and a biocatalyst have been proposed. It was demonstrated that the size of the NPs was the critical parameter for the mutual inhibition: the bigger the NPs, the more harmful for the enzyme they were, even if the NPs themselves were only moderately inactivated. Conversely, the smaller the NPs, the more minimal the TADH denaturation, although they were dramatically inhibited. Resuming, the chemocatalysts were very sensitive to deactivation, which was not related to the amount of enzyme used, while the inhibition of the biocatalyst can be strongly reduced by minimizing the NPs/TADH ratio used to catalyze the reaction. Among some methods to avoid direct binding of NPs with TADH, we found that using large Pd NPs and protecting their surfaces with a silica shell, the overall yield of 3-(1S,3S)-methylcyclohexanol was maximized (36%). Full article

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

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14 pages, 1477 KiB

Open AccessArticle

Designed Functional Dispersion for Insulin Protection from Pepsin Degradation and Skeletal Muscle Cell Proliferation: In Silico and In Vitro Study

by Veera C. S. R. Chittepu, Poonam Kalhotra, Tzayhri Gallardo-Velázquez, Raúl René Robles-de la Torre and Guillermo Osorio-Revilla

Nanomaterials 2018, 8(10), 852; https://doi.org/10.3390/nano8100852 - 19 Oct 2018

Cited by 2 | Viewed by 4494

Abstract

Functionalized single-walled carbon nanotubes with polyethylene glycol (PEGylated SWCNTs) are a promising nanomaterial that recently has emerged as the most attractive “cargo” to deliver chemicals, peptides, DNA and RNAs into cells. Insulin therapy is a recommended therapy to treat diabetes mellitus despite its [...] Read more.

Functionalized single-walled carbon nanotubes with polyethylene glycol (PEGylated SWCNTs) are a promising nanomaterial that recently has emerged as the most attractive “cargo” to deliver chemicals, peptides, DNA and RNAs into cells. Insulin therapy is a recommended therapy to treat diabetes mellitus despite its side effects. Recently, functional dispersion made up of bioactive peptides, bioactive compounds and functionalized carbon nanomaterials such as PEGylated SWCNTs have proved to possess promising applications in nanomedicine. In the present study, molecular modeling simulations are utilized to assist in designing insulin hormone-PEGylated SWCNT composites, also called functional dispersion; to achieve this experimentally, an ultrasonication tool was utilized. Enzymatic degradation assay revealed that the designed functional dispersion protects about 70% of free insulin from pepsin. In addition, sulforhodamine B (SRB) assay, the quantification of insulin and glucose levels in differentiated skeletal muscle cell supernatants, reveals that functional dispersion regulates glucose and insulin levels to promote skeletal muscle cell proliferation. These findings offer new perspectives for designed functional dispersion, as potential pharmaceutical preparations to improve insulin therapy and promote skeletal muscle cell health. Full article

(This article belongs to the Special Issue Macromolecules and Nanomaterials: Their Impact on Nanomedicine)

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16 pages, 1592 KiB

Open AccessReview

Two-Dimensional Nanomaterials for Gas Sensing Applications: The Role of Theoretical Calculations

by Yamei Zeng, Shiwei Lin, Ding Gu and Xiaogan Li

Nanomaterials 2018, 8(10), 851; https://doi.org/10.3390/nano8100851 - 19 Oct 2018

Cited by 100 | Viewed by 6597

Abstract

Two-dimensional (2D) nanomaterials have attracted a large amount of attention regarding gas sensing applications, because of their high surface-to-volume ratio and unique chemical or physical gas adsorption capabilities. As an important research method, theoretical calculations have been massively applied in predicting the potentially [...] Read more.

Two-dimensional (2D) nanomaterials have attracted a large amount of attention regarding gas sensing applications, because of their high surface-to-volume ratio and unique chemical or physical gas adsorption capabilities. As an important research method, theoretical calculations have been massively applied in predicting the potentially excellent gas sensing properties of these 2D nanomaterials. In this review, we discuss the contributions of theoretical calculations in the study of the gas sensing properties of 2D nanomaterials. Firstly, we elaborate on the gas sensing mechanisms of 2D layered nanomaterials, such as the traditional charge transfer mechanism, and a standard for distinguishing between physical and chemical adsorption, from the perspective of theoretical calculations. Then, we describe how to conduct a theoretical analysis to explain or predict the gas sensing properties of 2D nanomaterials. Thirdly, we discuss three important methods that have been applied in order to improve the gas sensing properties, that is, defect functionalization (vacancy, edge, grain boundary, and doping), heterojunctions, and electric fields. Among these strategies, theoretical calculations play a very important role in explaining the mechanisms underlying the enhanced gas sensing properties. Finally, we summarize both the advantages and limitations of the theoretical calculations, and present perspectives for further research on the 2D nanomaterials-based gas sensors. Full article

(This article belongs to the Special Issue Development of Semiconductor Nanomaterials for Gas Sensors)

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11 pages, 2353 KiB

Open AccessFeature PaperArticle

Magnetic Nanoparticles Create Hot Spots in Polymer Matrix for Controlled Drug Release

by Esther Cazares-Cortes, Maria Nerantzaki, Jérôme Fresnais, Claire Wilhelm, Nébéwia Griffete and Christine Ménager

Nanomaterials 2018, 8(10), 850; https://doi.org/10.3390/nano8100850 - 18 Oct 2018

Cited by 35 | Viewed by 5848

Abstract

Herein, original magnetic drug delivery nanomaterials for cancer therapy are developed and compared, with the purpose to show active control over drug release by using an alternative magnetic field (AMF). The rationale is to combine polymers and superparamagnetic nanoparticles to trigger such drug [...] Read more.

Herein, original magnetic drug delivery nanomaterials for cancer therapy are developed and compared, with the purpose to show active control over drug release by using an alternative magnetic field (AMF). The rationale is to combine polymers and superparamagnetic nanoparticles to trigger such drug release under AMF. Two magnetic nanosystems are thus presented: magnetic nanogels made of thermosensitive and biocompatible polymers and core-shell nanoparticles with a magnetic core and a molecularly imprinted polymer as shell. Both encapsulate doxorubicin (DOX) and the DOX controlled release was investigated in vitro and in cells under AMF excitation. It confirms that the local heat profile at the vicinity of the iron oxide core can be used for the DOX controlled release. It also shows that both nanosystems help delivering more DOX inside the cells compared to internalization of free DOX. Finally, the DOX intracellular release could be remotely triggered under AMF, in athermal conditions, thus enhancing DOX cytotoxicity. Full article

(This article belongs to the Special Issue Magnetic Nanoparticles in Biological Applications)

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14 pages, 4125 KiB

Open AccessArticle

Boron Nitride as a Novel Support for Highly Stable Palladium Nanocatalysts by Atomic Layer Deposition

by Matthieu Weber, Cassandre Lamboux, Bruno Navarra, Philippe Miele, Sandrine Zanna, Maxime E. Dufond, Lionel Santinacci and Mikhael Bechelany

Nanomaterials 2018, 8(10), 849; https://doi.org/10.3390/nano8100849 - 18 Oct 2018

Cited by 23 | Viewed by 5007

Abstract

The ability to prepare controllable nanocatalysts is of great interest for many chemical industries. Atomic layer deposition (ALD) is a vapor phase technique enabling the synthesis of conformal thin films and nanoparticles (NPs) on high surface area supports and has become an attractive [...] Read more.

The ability to prepare controllable nanocatalysts is of great interest for many chemical industries. Atomic layer deposition (ALD) is a vapor phase technique enabling the synthesis of conformal thin films and nanoparticles (NPs) on high surface area supports and has become an attractive new route to tailor supported metallic NPs. Virtually all the studies reported, focused on Pd NPs deposited on carbon and oxide surfaces. It is, however, important to focus on emerging catalyst supports such as boron nitride materials, which apart from possessing high thermal and chemical stability, also hold great promises for nanocatalysis applications. Herein, the synthesis of Pd NPs on boron nitride (BN) film substrates is demonstrated entirely by ALD for the first time. X-ray photoelectron spectroscopy indicated that stoichiometric BN formed as the main phase, with a small amount of BN_xO_y, and that the Pd particles synthesized were metallic. Using extensive transmission electron microscopy analysis, we study the evolution of the highly dispersed NPs as a function of the number of ALD cycles, and the thermal stability of the ALD-prepared Pd/BN catalysts up to 750 °C. The growth and coalescence mechanisms observed are discussed and compared with Pd NPs grown on other surfaces. The results show that the nanostructures of the BN/Pd NPs were relatively stable up to 500 °C. Consequent merging has been observed when annealing the samples at 750 °C, as the NPs’ average diameter increased from 8.3 ± 1.2 nm to 31 ± 4 nm. The results presented open up exciting new opportunities in the field of catalysis. Full article

(This article belongs to the Special Issue Design of Nanostructured Materials by Atomic Layer Deposition and Its Applications)

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17 pages, 5373 KiB

Open AccessArticle

Rebuilding the Strain Hardening at a Large Strain in Twinned Au Nanowires

by Jiapeng Sun, Jing Han, Zhenquan Yang, Huan Liu, Dan Song, Aibin Ma and Liang Fang

Nanomaterials 2018, 8(10), 848; https://doi.org/10.3390/nano8100848 - 18 Oct 2018

Cited by 7 | Viewed by 3111

Abstract

Metallic nanowires usually exhibit ultrahigh strength but low tensile ductility, owing to their limited strain hardening capability. Here, our larger scale molecular dynamics simulations demonstrated that we could rebuild the highly desirable strain hardening behavior at a large strain (0.21 to 0.31) in [...] Read more.

Metallic nanowires usually exhibit ultrahigh strength but low tensile ductility, owing to their limited strain hardening capability. Here, our larger scale molecular dynamics simulations demonstrated that we could rebuild the highly desirable strain hardening behavior at a large strain (0.21 to 0.31) in twinned Au nanowires by changing twin orientation, which strongly contrasts with the strain hardening at the incipient plastic deformation in low stacking-fault energy metals nanowires. Because of this strain hardening, an improved ductility is achieved. With the change of twin orientation, a competing effect between partial dislocation propagation and twin migration is observed in nanowires with slant twin boundaries. When twin migration gains the upper hand, the strain hardening occurs. Otherwise, the strain softening occurs. As the twin orientation increases from 0° to 90°, the dominating deformation mechanism shifts from slip-twin boundary interaction to dislocation slip, twin migration, and slip transmission in sequence. Our work could not only deepen our understanding of the mechanical behavior and deformation mechanism of twinned Au nanowires, but also provide new insights into enhancing the strength and ductility of nanowires by engineering the nanoscale twins. Full article

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15 pages, 2963 KiB

Open AccessArticle

Temoporfin-in-Cyclodextrin-in-Liposome—A New Approach for Anticancer Drug Delivery: The Optimization of Composition

by Ilya Yakavets, Henri-Pierre Lassalle, Dietrich Scheglmann, Arno Wiehe, Vladimir Zorin and Lina Bezdetnaya

Nanomaterials 2018, 8(10), 847; https://doi.org/10.3390/nano8100847 - 18 Oct 2018

Cited by 32 | Viewed by 5496

Abstract

The main goal of this study was to use hybrid delivery system for effective transportation of temoporfin (meta-tetrakis(3-hydroxyphenyl)chlorin, mTHPC) to target tissue. We suggested to couple two independent delivery systems (liposomes and inclusion complexes) to achieve drug-in-cyclodextrin-in-liposome (DCL) nanoconstructs. We further [...] Read more.

The main goal of this study was to use hybrid delivery system for effective transportation of temoporfin (meta-tetrakis(3-hydroxyphenyl)chlorin, mTHPC) to target tissue. We suggested to couple two independent delivery systems (liposomes and inclusion complexes) to achieve drug-in-cyclodextrin-in-liposome (DCL) nanoconstructs. We further optimized the composition of DCLs, aiming to alter in a more favorable way a distribution of temoporfin in tumor tissue. We have prepared DCLs with different compositions varying the concentration of mTHPC and the type of β-cyclodextrin (β-CD) derivatives (Hydroxypropyl-, Methyl- and Trimethyl-β-CD). DCLs were prepared by thin-hydration technique and mTHPC/β-CD complexes were added at hydration step. The size was about 135 nm with the surface charge of (−38 mV). We have demonstrated that DCLs are stable and almost all mTHPC is bound to β-CDs in the inner aqueous liposome core. Among all tested DCLs, trimethyl-β-CD-based DCL demonstrated a homogenous accumulation of mTHPC across tumor spheroid volume, thus supposing optimal mTHPC distribution. Full article

(This article belongs to the Special Issue Nanomaterials for Photothermal/Photodynamic Therapy)

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16 pages, 3878 KiB

Open AccessArticle

Physicochemical Characterization of FRET-Labelled Chitosan Nanocapsules and Model Degradation Studies

by Stefan Hoffmann, Christian Gorzelanny, Bruno Moerschbacher and Francisco M. Goycoolea

Nanomaterials 2018, 8(10), 846; https://doi.org/10.3390/nano8100846 - 17 Oct 2018

Cited by 13 | Viewed by 4859

Abstract

Sub-micron o/w emulsions coated with chitosan have been used for drug delivery, quorum sensing inhibition, and vaccine development. To study interactions with biological systems, nanocapsules have been fluorescently labelled in previous works, but it is often difficult to distinguish the released label from [...] Read more.

Sub-micron o/w emulsions coated with chitosan have been used for drug delivery, quorum sensing inhibition, and vaccine development. To study interactions with biological systems, nanocapsules have been fluorescently labelled in previous works, but it is often difficult to distinguish the released label from intact nanocapsules. In this study, we present advanced-labelling strategies based on Förster Resonance Energy Transfer (FRET) measurements for chitosan-coated nanocapsules and investigate their dissolution and degradation. We used FRET measurements of nanocapsules loaded with equimolar concentrations of two fluorescent dyes in their oily core and correlated them with dynamic light scattering (DLS) count rate measurement and absorbance measurements during their disintegration by dissolution. Using count rate measurements, we also investigated the enzymatic degradation of nanocapsules using pancreatin and how protein corona formation influences their degradation. Of note, nanocapsules dissolved in ethanol, while FRET decreased simultaneously with count rate, and absorbance was caused by nanocapsule turbidity, indicating increased distance between dye molecules after their release. Nanocapsules were degradable by pancreatin in a dose-dependent manner, and showed a delayed enzymatic degradation after protein corona formation. We present here novel labelling strategies for nanocapsules that allow us to judge their status and an in vitro method to study nanocapsule degradation and the influence of surface characteristics. Full article

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10 pages, 2761 KiB

Open AccessArticle

An Eight-Channel C-Band Demux Based on Multicore Photonic Crystal Fiber

by Dror Malka and Gilad Katz

Nanomaterials 2018, 8(10), 845; https://doi.org/10.3390/nano8100845 - 17 Oct 2018

Cited by 37 | Viewed by 4205

Abstract

A novel eight-channel demux device based on multicore photonic crystal fiber (PCF) structures that operate in the C-band range (1530–1565 nm) has been demonstrated. The PCF demux design is based on replacing some air-hole areas with lithium niobate and silicon nitride materials over [...] Read more.

A novel eight-channel demux device based on multicore photonic crystal fiber (PCF) structures that operate in the C-band range (1530–1565 nm) has been demonstrated. The PCF demux design is based on replacing some air-hole areas with lithium niobate and silicon nitride materials over the PCF axis alongside with the appropriate optimizations of the PCF structure. The beam propagation method (BPM) combined with Matlab codes was used to model the demux device and optimize the geometrical parameters of the PCF structure. The simulation results showed that the eight-channel demux can be demultiplexing after light propagation of 5 cm with a large bandwidth (4.03–4.69 nm) and cross-talk (−16.88 to −15.93 dB). Thus, the proposed device has great potential to be integrated into dense wavelength division multiplexing (DWDM) technology for increasing performances in networking systems. Full article

(This article belongs to the Special Issue Synthesis and Modification of Nanostructured Thin Films)

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10 pages, 3170 KiB

Open AccessCommunication

Green Preparation of High Yield Fluorescent Graphene Quantum Dots from Coal-Tar-Pitch by Mild Oxidation

by Quanrun Liu, Jingjie Zhang, He He, Guangxu Huang, Baolin Xing, Jianbo Jia and Chuanxiang Zhang

Nanomaterials 2018, 8(10), 844; https://doi.org/10.3390/nano8100844 - 17 Oct 2018

Cited by 76 | Viewed by 7737

Abstract

Coal tar pitch (CTP), a by-product of coking industry, has a unique molecule structure comprising an aromatic nucleus and several side chains bonding on this graphene-like nucleus, which is very similar to the structure of graphene quantum dots (GQDs). Based on this perception, [...] Read more.

Coal tar pitch (CTP), a by-product of coking industry, has a unique molecule structure comprising an aromatic nucleus and several side chains bonding on this graphene-like nucleus, which is very similar to the structure of graphene quantum dots (GQDs). Based on this perception, we develop a facile approach to convert CTP to GQDs only by oxidation with hydrogen peroxide under mild conditions. One to three graphene layers, monodisperse GQDs with a narrow size distribution of 1.7 ± 0.4 nm, are obtained at high yield (more than 80 wt. %) from CTP. The as-produced GQDs are highly soluble and strongly fluorescent in aqueous solution. This simple strategy provides a feasible route towards the commercial synthesis of GQDs for its cheap material source, green reagent, mild condition, and high yield. Full article

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12 pages, 25599 KiB

Open AccessArticle

Direct Exfoliation of Natural SiO₂-Containing Molybdenite in Isopropanol: A Cost Efficient Solution for Large-Scale Production of MoS₂ Nanosheetes

by Wenyan Zhao, Tao Jiang, Yujie Shan, Hongrui Ding, Junxian Shi, Haibin Chu and Anhuai Lu

Nanomaterials 2018, 8(10), 843; https://doi.org/10.3390/nano8100843 - 17 Oct 2018

Cited by 11 | Viewed by 4788

Abstract

The cost-effective exfoliation of layered materials such as transition metal dichalcogenides into mono- or few- layers is of significant interest for various applications. This paper reports the preparation of few-layered MoS₂ from natural SiO₂-containing molybdenite by exfoliation in isopropanol (IPA) [...] Read more.

The cost-effective exfoliation of layered materials such as transition metal dichalcogenides into mono- or few- layers is of significant interest for various applications. This paper reports the preparation of few-layered MoS₂ from natural SiO₂-containing molybdenite by exfoliation in isopropanol (IPA) under mild ultrasonic conditions. One- to six-layer MoS₂ nanosheets with dimensions in the range of 50-200 nm are obtained. By contrast, MoS₂ quantum dots along with nanosheets are produced using N-methyl-pyrrolidone (NMP) and an aqueous solution of poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) (P123) as exfoliation solutions. Compared with molybdenite, commercial bulk MoS₂ cannot be exfoliated to nanosheets under the same experimental conditions. In the exfoliation process of the mineral, SiO₂ associated in molybdenite plays the role of similar superfine ball milling, which significantly enhances the exfoliation efficiency. This work demonstrates that isopropanol can be used to exfoliate natural molybdenite under mild conditions to produce nanosheets, which facilitates the preparation of highly concentrated MoS₂ dispersions or MoS₂ in powder form due to the volatility of the solvent. Such exfoliated MoS₂ nanosheets exhibit excellent photoconductivity under visible light. Hence, the direct mild exfoliation method of unrefined natural molybdenite provides a solution for low-cost and convenient production of few-layered MoS₂ which is appealing for industrial applications. Full article

(This article belongs to the Special Issue Preparation and Properties of 2D Materials)

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15 pages, 4604 KiB

Open AccessArticle

One-Step Synthesis Heterostructured g-C₃N₄/TiO₂ Composite for Rapid Degradation of Pollutants in Utilizing Visible Light

by Hui Liu, Zhi-Guang Zhang, Hong-Wei He, Xiao-Xiong Wang, Jun Zhang, Qian-Qian Zhang, Yan-Fu Tong, Hong-Ling Liu, Seeram Ramakrishna, Shi-Ying Yan and Yun-Ze Long

Nanomaterials 2018, 8(10), 842; https://doi.org/10.3390/nano8100842 - 16 Oct 2018

Cited by 61 | Viewed by 5904

Abstract

To meet the urgent need of society for advanced photocatalytic materials, novel visible light driven heterostructured composite was constructed based on graphitic carbon nitride (g-C₃N₄) and fibrous TiO₂. The g-C₃N₄/TiO₂ (CNT) composite [...] Read more.

To meet the urgent need of society for advanced photocatalytic materials, novel visible light driven heterostructured composite was constructed based on graphitic carbon nitride (g-C₃N₄) and fibrous TiO₂. The g-C₃N₄/TiO₂ (CNT) composite was prepared through electrospinning technology and followed calcination process. The state of the g-C₃N₄ and fibrous TiO₂ was tightly coupled. The photocatalytic performance was measured by degrading the Rhodamine B. Compared to commercial TiO₂ (P25^®) and electrospun TiO₂ nanofibers, the photocatalytic performance of CNT composite was higher than them. The formation of CNT heterostructures and the enlarged specific surface area enhanced the photocatalytic performance, suppressing the recombination rate of photogenerated carriers while broadening the absorption range of light spectrum. Our studies have demonstrated that heterostructured CNT composite with an appropriate proportion can rational use of visible light and can significantly promote the photogenerated charges transferred at the contact interface between g-C₃N₄ and TiO₂. Full article

(This article belongs to the Special Issue Advances in Heterocatalysis by Nanomaterials)

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10 pages, 1431 KiB

Open AccessLetter

Micelle-Assisted Strategy for the Direct Synthesis of Large-Sized Mesoporous Platinum Catalysts by Vapor Infiltration of a Reducing Agent

by Yunqi Li, Yuwei Liu, Yusuke Yamauchi, Yusuf Valentino Kaneti, Saad M. Alsheri, Tansir Ahamad, Norah Alhokbany, Jeonghun Kim, Katsuhiko Ariga, Ning Wu and Jun Xu

Nanomaterials 2018, 8(10), 841; https://doi.org/10.3390/nano8100841 - 16 Oct 2018

Cited by 4 | Viewed by 3707

Abstract

Stable polymeric micelles have been demonstrated to serve as suitable templates for creating mesoporous metals. Herein, we report the utilization of a core-shell-corona type triblock copolymer of poly(styrene-b-2-vinylpyridine-b-ethylene oxide) and H₂PtCl₆·H₂O to synthesize [...] Read more.

Stable polymeric micelles have been demonstrated to serve as suitable templates for creating mesoporous metals. Herein, we report the utilization of a core-shell-corona type triblock copolymer of poly(styrene-b-2-vinylpyridine-b-ethylene oxide) and H₂PtCl₆·H₂O to synthesize large-sized mesoporous Pt particles. After formation of micelles with metal ions, the reduction process has been carried out by vapor infiltration of a reducing agent, 4-(Dimethylamino)benzaldehyde. Following the removal of the pore-directing agent under the optimized temperature, mesoporous Pt particles with an average pore size of 15 nm and surface area of 12.6 m²·g⁻¹ are achieved. More importantly, the resulting mesoporous Pt particles exhibit superior electrocatalytic activity compared to commercially available Pt black. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Nanoporous Functional Materials)

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19 pages, 3591 KiB

Open AccessArticle

Synthetic Bio-Graphene Based Nanomaterials through Different Iron Catalysts

by Qiangu Yan, Jinghao Li, Xuefeng Zhang, Jilei Zhang and Zhiyong Cai

Nanomaterials 2018, 8(10), 840; https://doi.org/10.3390/nano8100840 - 16 Oct 2018

Cited by 22 | Viewed by 5324

Abstract

Kraft lignin was catalytically graphitized to graphene-based nanostructures at 1000 °C under argon atmosphere with four iron catalysts, iron(III) nitrate (Fe-N); iron(II) chloride (Fe-Cl₂); iron(III) chloride (Fe-Cl₃); and iron(II) sulfate (Fe-S). The catalytic decomposition process of iron-promoted lignin materials [...] Read more.

Kraft lignin was catalytically graphitized to graphene-based nanostructures at 1000 °C under argon atmosphere with four iron catalysts, iron(III) nitrate (Fe-N); iron(II) chloride (Fe-Cl₂); iron(III) chloride (Fe-Cl₃); and iron(II) sulfate (Fe-S). The catalytic decomposition process of iron-promoted lignin materials was examined using thermalgravimetric analysis and temperature-programmed decomposition methods. The crystal structure, morphology and surface area of produced materials were characterized by means of X-ray diffraction, Raman, scanning electron microscopy, high resolution transmission electron microscopy and N₂ adsorption−desorption techniques. Experimental results indicated that iron nitrate catalyst had better iron dispersion three other iron salts. Iron nitrate was the most active catalyst among four iron salts. The low activity of iron in iron chloride-promoted samples was because the residual chlorine over iron surfaces prevent iron interaction with lignin functional groups. Full article

(This article belongs to the Special Issue Graphite, Graphene, Advanced Carbon Materials and Nanostructured Carbon-Based Composites and Selected Papers from Carbon 2018)

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14 pages, 3569 KiB

Open AccessArticle

Effects of Copper Oxide Nanoparticles on Paddy Soil Properties and Components

by Jiyan Shi, Jien Ye, Huaxiang Fang, Shu Zhang and Chen Xu

Nanomaterials 2018, 8(10), 839; https://doi.org/10.3390/nano8100839 - 16 Oct 2018

Cited by 59 | Viewed by 4784

Abstract

The wide use of metal-based nanoparticles (MNPs) will inevitably lead to their release into soil, and consequently affect the quality and ecological functions of soil environments. In this study, two paddy soils with different properties were exposed to CuO NPs to evaluate the [...] Read more.

The wide use of metal-based nanoparticles (MNPs) will inevitably lead to their release into soil, and consequently affect the quality and ecological functions of soil environments. In this study, two paddy soils with different properties were exposed to CuO NPs to evaluate the transformation of CuO NPs and their effects on soil properties and components. The results of single chemical extraction and X-ray absorption fine structure analysis showed that CuO NPs could release Cu ions once being applied into the flooding paddy soil and then progress toward the more stable forms (Cu₂S and Cu(OH)₂). CuO NPs could change the soil properties by increasing the pH and Eh of the lower organic matter-soil rather than those of the higher organic matter-soil. Furthermore, we found that the 1000 mg/kg CuO NPs could accelerate the degradation or mineralization of the organic matter, as well as the Fe reduction process, by increasing the Fe(II) content by 293% after flooding for 60 days in the lower organic matter soil. The microbial biomass in both soils was severely inhibited by CuO NPs and the organic matter could partly mitigate the negative effects of CuO NPs. Full article

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24 pages, 2767 KiB

Open AccessArticle

Radiation and Energetic Analysis of Nanofluid Based Volumetric Absorbers for Concentrated Solar Power

by Jan Rudolf Eggers, Eckart Matthias Lange and Stephan Kabelac

Nanomaterials 2018, 8(10), 838; https://doi.org/10.3390/nano8100838 - 16 Oct 2018

Cited by 8 | Viewed by 3730

Abstract

Recently, several publications gave attention to nanofluid based solar absorber systems in which the solar radiation energy is directly absorbed in the volume of the fluid. This idea could provide advantages over conventionally used surface absorbers regarding the optical and thermal efficiency. For [...] Read more.

Recently, several publications gave attention to nanofluid based solar absorber systems in which the solar radiation energy is directly absorbed in the volume of the fluid. This idea could provide advantages over conventionally used surface absorbers regarding the optical and thermal efficiency. For the evaluation of this concept, a numerical approach is introduced and validated in this contribution. The results show that the optical efficiency of a volumetric absorber strongly depends on the scattering behavior of the nanofluid and can reach competitive values only if the particle size distribution is narrow and small. If this is achieved, the surface temperature and therefore the heat loss can be lowered significantly. Furthermore, the surface absorber requires very high Reynolds numbers to transfer the absorbed energy into the working fluid and avoid overheating of the absorber tube. This demand of pumping power can be reduced significantly using the concept of volumetric absorption. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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12 pages, 1470 KiB

Open AccessArticle

New Antioxidant Multilayer Packaging with Nanoselenium to Enhance the Shelf-Life of Market Food Products

by Paula Vera, Elena Canellas and Cristina Nerín

Nanomaterials 2018, 8(10), 837; https://doi.org/10.3390/nano8100837 - 16 Oct 2018

Cited by 45 | Viewed by 5358

Abstract

A flexible multilayer with selenium nanoparticles incorporated has been used to build an antioxidant packaging. The oxidation of hazelnuts, walnuts, and potato chips was tested at laboratory scale. Hexanal released by the nuts, fatty acids oxidation study, TBARS (thiobarbituric acid reactive substances), and [...] Read more.

A flexible multilayer with selenium nanoparticles incorporated has been used to build an antioxidant packaging. The oxidation of hazelnuts, walnuts, and potato chips was tested at laboratory scale. Hexanal released by the nuts, fatty acids oxidation study, TBARS (thiobarbituric acid reactive substances), and tasting were compared to study the oxidation of foods packaged with this antioxidant packaging. Finally, TBARS method in combination with tasting were selected due to their simplicity and accuracy. It was found that hazelnuts packaged in nanoSe active bags released around 20% less malonaldehyde (MDA) than the blanks. In the case of the walnuts, the active ones released 25% less MDA than the blanks. As for potato chips, the improvement was around 22%. Finally, an industrial study was done. Cooked ham, chicken, and a ready-to-eat vegetable mixture seasoned with butter were industrially packaged with the new antioxidant material and improvements higher than 25% were obtained. Full article

(This article belongs to the Special Issue Nanomaterials to Enhance Food Quality, Safety, and Health Impact)

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12 pages, 2654 KiB

Open AccessArticle

Ultra-Thin Platinum Deposits by Surface-Limited Redox Replacement of Tellurium

by Fatima Haidar, Mathieu Maas, Andrea Piarristeguy, Annie Pradel, Sara Cavaliere and Marie-Christine Record

Nanomaterials 2018, 8(10), 836; https://doi.org/10.3390/nano8100836 - 15 Oct 2018

Cited by 3 | Viewed by 5660

Abstract

Platinum is the most employed electrocatalyst for the reactions taking place in energy converters, such as the oxygen reduction reaction in proton exchange membrane fuel cells, despite being a very low abundant element in the earth’s crust and thus extremely expensive. The search [...] Read more.

Platinum is the most employed electrocatalyst for the reactions taking place in energy converters, such as the oxygen reduction reaction in proton exchange membrane fuel cells, despite being a very low abundant element in the earth’s crust and thus extremely expensive. The search for more active electrocatalysts with ultra-low Pt loading is thus a very active field of investigation. Here, surface-limited redox replacement (SLRR) that utilizes the monolayer-limited nature of underpotential deposition (UPD) was used to prepare ultrathin deposits of Pt, using Te as sacrificial metal. Cyclic voltammetry and anodic potentiodynamic scanning experiments have been performed to determine the optimal deposition conditions. Physicochemical and electrochemical characterization of the deposited Pt was carried out. The deposit comprises a series of contiguous Pt islands that form along the grain interfaces of the Au substrate. The electrochemical surface area (ECSA) of the Pt deposit obtained after 5 replacements, estimated to be 18 m²/g, is in agreement with the ECSA of extended surface catalysts on flat surfaces. Full article

(This article belongs to the Special Issue Design and Development of Nanostructured Thin Films)

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