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Nanomaterials, Volume 11, Issue 6 (June 2021) – 273 articles

Cover Story (view full-size image): The paper presents an approach to recycling coffee waste to graphene quantum dots (GQDs) as an environmentally friendly nanodrug candidate. Consistent with previous findings on carbon fiber-derived GQDs, coffee-bean-derived GQDs elicit similar effectiveness against abnormal α-synuclein fibrillation in Parkinson’s disease and ensuing subcellular damages, including the loss of neurons. The finding illustrates a potential approach to converting such waste materials into novel nanomedicine. View this paper
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Review
Carbon-Based Nanofluids and Their Advances towards Heat Transfer Applications—A Review
Nanomaterials 2021, 11(6), 1628; https://doi.org/10.3390/nano11061628 - 21 Jun 2021
Cited by 17 | Viewed by 1685
Abstract
Nanofluids have opened the doors towards the enhancement of many of today’s existing thermal applications performance. This is because these advanced working fluids exhibit exceptional thermophysical properties, and thus making them excellent candidates for replacing conventional working fluids. On the other hand, nanomaterials [...] Read more.
Nanofluids have opened the doors towards the enhancement of many of today’s existing thermal applications performance. This is because these advanced working fluids exhibit exceptional thermophysical properties, and thus making them excellent candidates for replacing conventional working fluids. On the other hand, nanomaterials of carbon-base were proven throughout the literature to have the highest thermal conductivity among all other types of nanoscaled materials. Therefore, when these materials are homogeneously dispersed in a base fluid, the resulting suspension will theoretically attain orders of magnitude higher effective thermal conductivity than its counterpart. Despite this fact, there are still some challenges that are associated with these types of fluids. The main obstacle is the dispersion stability of the nanomaterials, which can lead the attractive properties of the nanofluid to degrade with time, up to the point where they lose their effectiveness. For such reason, this work has been devoted towards providing a systematic review on nanofluids of carbon-base, precisely; carbon nanotubes, graphene, and nanodiamonds, and their employment in thermal systems commonly used in the energy sectors. Firstly, this work reviews the synthesis approaches of the carbon-based feedstock. Then, it explains the different nanofluids fabrication methods. The dispersion stability is also discussed in terms of measuring techniques, enhancement methods, and its effect on the suspension thermophysical properties. The study summarizes the development in the correlations used to predict the thermophysical properties of the dispersion. Furthermore, it assesses the influence of these advanced working fluids on parabolic trough solar collectors, nuclear reactor systems, and air conditioning and refrigeration systems. Lastly, the current gap in scientific knowledge is provided to set up future research directions. Full article
(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)
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Article
Hollow Silica Particles: A Novel Strategy for Cost Reduction
Nanomaterials 2021, 11(6), 1627; https://doi.org/10.3390/nano11061627 - 21 Jun 2021
Cited by 1 | Viewed by 1029
Abstract
Thermal insulation materials are highly sought after for applications such as building envelopes, refrigerators, cryogenic fuel storage chambers, and water supply piping. However, current insulation materials either do not provide sufficient insulation or are costly. A new class of insulation materials, hollow silica [...] Read more.
Thermal insulation materials are highly sought after for applications such as building envelopes, refrigerators, cryogenic fuel storage chambers, and water supply piping. However, current insulation materials either do not provide sufficient insulation or are costly. A new class of insulation materials, hollow silica particles, has attracted tremendous attention due to its potential to provide a very high degree of thermal insulation. However, current synthesis strategies provide hollow silica particles at very low yields and at high cost, thus, making the particles unsuitable for real-world applications. In the present work, a synthesis process that produces hollow silica particles at very high yields and at a lower cost is presented. The effect of an infrared heat absorber, carbon black, on the thermal conductivity of hollow silica particles is also investigated and it is inferred that a carbon black–hollow silica particle mixture can be a better insulating material than hollow silica particles alone. Full article
(This article belongs to the Special Issue Thermal Transport in Nanoscale)
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Article
High-Resolution Two-Dimensional Imaging of the 4H-SiC MOSFET Channel by Scanning Capacitance Microscopy
Nanomaterials 2021, 11(6), 1626; https://doi.org/10.3390/nano11061626 - 21 Jun 2021
Cited by 2 | Viewed by 886
Abstract
In this paper, a two-dimensional (2D) planar scanning capacitance microscopy (SCM) method is used to visualize with a high spatial resolution the channel region of large-area 4H-SiC power MOSFETs and estimate the homogeneity of the channel length over the whole device perimeter. The [...] Read more.
In this paper, a two-dimensional (2D) planar scanning capacitance microscopy (SCM) method is used to visualize with a high spatial resolution the channel region of large-area 4H-SiC power MOSFETs and estimate the homogeneity of the channel length over the whole device perimeter. The method enabled visualizing the fluctuations of the channel geometry occurring under different processing conditions. Moreover, the impact of the ion implantation parameters on the channel could be elucidated. Full article
(This article belongs to the Special Issue Nanotechnology for Electronic Materials and Devices)
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Article
Determination of the Concentration of Ultrafine Aerosol Using an Ionization Sensor
Nanomaterials 2021, 11(6), 1625; https://doi.org/10.3390/nano11061625 - 21 Jun 2021
Viewed by 786
Abstract
As public awareness of the threats related to ultrafine aerosols increases, there is a growing need for inexpensive, real-time exposure assessment devices. In this work, the well-established technology used in the smoke detector with a radioactive source was tested in laboratory conditions to [...] Read more.
As public awareness of the threats related to ultrafine aerosols increases, there is a growing need for inexpensive, real-time exposure assessment devices. In this work, the well-established technology used in the smoke detector with a radioactive source was tested in laboratory conditions to check its suitability for determining the number concentration of the ultrafine aerosol. It has been shown that the sensor output changes linearly with the change of diesel soot concentration in the range up to 8.3 × 105 particles cm−3. The sensor has also been shown to be able to detect rapid changes in aerosol concentration. Empirical equations describing the influence of air velocity, temperature, relative humidity, and pressure on the sensor output were determined. The collected results confirm that the ionization sensor can be used to assess ultrafine aerosol exposure, although additional engineering work is required to increase the resolution of the output signal measurement and to compensate for the effects of weather conditions. The presented method can be used for concentration monitoring and risk assessment in environmental engineering, materials engineering, cosmetics industry, textiles, sports, chemical, mining, energy, etc. Full article
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Article
Microstructure Evolution and Mechanical Properties of Austenite Stainless Steel with Gradient Twinned Structure by Surface Mechanical Attrition Treatment
Nanomaterials 2021, 11(6), 1624; https://doi.org/10.3390/nano11061624 - 21 Jun 2021
Cited by 5 | Viewed by 961
Abstract
Gradient structures in engineering materials produce an impressive synergy of strength and plasticity, thereafter, have recently attracted extensive attention in the material families. Gradient structured stainless steels (SS) were prepared by surface mechanical attrition treatment (SMAT) with different impacting velocities. The microstructures of [...] Read more.
Gradient structures in engineering materials produce an impressive synergy of strength and plasticity, thereafter, have recently attracted extensive attention in the material families. Gradient structured stainless steels (SS) were prepared by surface mechanical attrition treatment (SMAT) with different impacting velocities. The microstructures of the treated samples are characterized by gradient twin fraction and phase constituents. Quantitative relations of gradient microstructure with impacting time and mechanical properties are analyzed according to the observations of SEM, TEM, XRD, and tests of mechanical property. The processed SSs exhibited to be simultaneously stiff, strong, and ductile, which can be attributed to the co-operation of the different spatial distributions of multi-scaled structures. The formation of gradient twinned structure is resolved and the strengthening by gradient structure is explored. Full article
(This article belongs to the Special Issue Gradient Nanograined Materials)
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Article
Beyond Charge Transfer: The Impact of Auger Recombination and FRET on PL Quenching in an rGO-QDs System
Nanomaterials 2021, 11(6), 1623; https://doi.org/10.3390/nano11061623 - 21 Jun 2021
Viewed by 860
Abstract
PL intensity quenching and the PL lifetime reduction of fluorophores located close to graphene derivatives are generally explained by charge and energy transfer processes. Analyzing the PL from PbS QDs in rGO/QD systems, we observed a substantial reduction in average PL lifetimes with [...] Read more.
PL intensity quenching and the PL lifetime reduction of fluorophores located close to graphene derivatives are generally explained by charge and energy transfer processes. Analyzing the PL from PbS QDs in rGO/QD systems, we observed a substantial reduction in average PL lifetimes with an increase in rGO content that cannot be interpreted solely by these two processes. To explain the PL lifetime dependence on the rGO/QD component ratio, we propose a model based on the Auger recombination of excitations involving excess holes left in the QDs after the charge transfer process. To validate the model, we conducted additional experiments involving the external engineering of free charge carriers, which confirmed the role of excess holes as the main QD PL quenching source. A mathematical simulation of the model demonstrated that the energy transfer between neighboring QDs must also be considered to explain the experimental data carefully. Together, Auger recombination and energy transfer simulation offers us an excellent fit for the average PL lifetime dependence on the component ratio of the rGO/QD system. Full article
(This article belongs to the Special Issue Luminescent Colloidal Nanocrystals)
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Article
Evaluation of Autogenous Healing in Flexural Mortar Members by Chloride Ion Penetration Resistance
Nanomaterials 2021, 11(6), 1622; https://doi.org/10.3390/nano11061622 - 21 Jun 2021
Cited by 2 | Viewed by 827
Abstract
In this study, we investigated the effects of mineral admixtures on the autogenous healing of flexural mortar members through a chloride ion penetration test. The mineral admixtures used were ground granulated blast-furnace slag (GGBS), fly ash, silica fume (SF), clinker binder, and clinker [...] Read more.
In this study, we investigated the effects of mineral admixtures on the autogenous healing of flexural mortar members through a chloride ion penetration test. The mineral admixtures used were ground granulated blast-furnace slag (GGBS), fly ash, silica fume (SF), clinker binder, and clinker sand. Through a four-point bending test, a crack of approximately 100 μm was induced at the bottom of the flexural mortar member, and the chloride ion penetration depth through the crack was measured to evaluate the self-healing performance. Additionally, we analyzed the correlation between the self-healing performances, which was measured through water flow and water absorption tests. The experimental results showed that the chloride ion penetration depth decreased due to crack healing, and the self-healing performance of the GGBS and SF was the highest. It was found that the subtle change in the self-healing performance was more accurately evaluated by the chloride ion penetration test. Full article
(This article belongs to the Special Issue Smart Cementitious Materials for Sustainable Building Engineering)
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Article
Plasmon-Enhanced Antibacterial Activity of Chiral Gold Nanoparticles and In Vivo Therapeutic Effect
Nanomaterials 2021, 11(6), 1621; https://doi.org/10.3390/nano11061621 - 21 Jun 2021
Cited by 3 | Viewed by 973
Abstract
d-cysteine (d-cys) has been demonstrated to possess an extraordinary antibacterial activity because of its unique steric configuration. However, inefficient antibacterial properties seriously hinder its wide applications. Here, cysteine-functionalized gold nanoparticles (d-/l-Au NPs) were prepared by loading [...] Read more.
d-cysteine (d-cys) has been demonstrated to possess an extraordinary antibacterial activity because of its unique steric configuration. However, inefficient antibacterial properties seriously hinder its wide applications. Here, cysteine-functionalized gold nanoparticles (d-/l-Au NPs) were prepared by loading d-/l-cysteine on the surface of gold nanoparticles for the effective inhibition of Escherichia coli (E. coli) in vitro and in vivo, and the effects on the intestinal microflora in mice were explored during the treatment of E. coli infection in the gut. We found that the antibacterial activity of d-/l-Au NPs was more than 2–3 times higher than pure d-cysteine, l-cysteine and Au NPs. Compared with l-Au NPs, d-Au NPs showed the stronger antibacterial activity, which was related to its unique steric configuration. Chiral Au NPs showed stronger destructive effects on cell membrane compared to other groups, which further leads to the leakage of the cytoplasm and bacterial cell death. The in vivo antibacterial experiment illustrated that d-Au NPs displayed impressive antibacterial activity in the treatment of E. coli-infected mice comparable to kanamycin, whereas they could not affect the balance of intestinal microflora. This work is of great significance in the development of an effective chiral antibacterial agent. Full article
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Article
Ultra-Low Percolation Threshold Induced by Thermal Treatments in Co-Continuous Blend-Based PP/PS/MWCNTs Nanocomposites
Nanomaterials 2021, 11(6), 1620; https://doi.org/10.3390/nano11061620 - 21 Jun 2021
Cited by 1 | Viewed by 903
Abstract
The effect of the crystallization of polypropylene (PP) forming an immiscible polymer blend with polystyrene (PS) containing conductive multi-wall carbon nanotubes (MWCNTs) on its electrical conductivity and electrical percolation threshold (PT) was investigated in this work. PP/PS/MWCNTs composites with a co-continuous morphology and [...] Read more.
The effect of the crystallization of polypropylene (PP) forming an immiscible polymer blend with polystyrene (PS) containing conductive multi-wall carbon nanotubes (MWCNTs) on its electrical conductivity and electrical percolation threshold (PT) was investigated in this work. PP/PS/MWCNTs composites with a co-continuous morphology and a concentration of MWCNTs ranging from 0 to 2 wt.% were obtained. The PT was greatly reduced by a two-step approach. First, a 50% reduction in the PT was achieved by using the effect of double percolation in the blend system compared to PP/MWCNTs. Second, with the additional thermal treatments, referred to as slow-cooling treatment (with the cooling rate 0.5 °C/min), and isothermal treatment (at 135 °C for 15 min), ultra-low PT values were achieved for the PP/PS/MWCNTs system. A 0.06 wt.% of MWCNTs was attained upon the use of the slow-cooling treatment and 0.08 wt.% of MWCNTs upon the isothermal treatment. This reduction is attributed to PP crystals’ volume exclusion, with no alteration in the blend morphology. Full article
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Article
Strong Dipole-Quadrupole-Exciton Coupling Realized in a Gold Nanorod Dimer Placed on a Two-Dimensional Material
Nanomaterials 2021, 11(6), 1619; https://doi.org/10.3390/nano11061619 - 20 Jun 2021
Viewed by 1064
Abstract
Simple systems in which strong coupling of different excitations can be easily realized are highly important, not only for fundamental research but also for practical applications. Here, we proposed a T-shaped gold nanorod (GNR) dimer composed of a long GNR and a short [...] Read more.
Simple systems in which strong coupling of different excitations can be easily realized are highly important, not only for fundamental research but also for practical applications. Here, we proposed a T-shaped gold nanorod (GNR) dimer composed of a long GNR and a short GNR perpendicular to each other and revealed that the dark quadrupole mode of the long GNR can be activated by utilizing the dipole mode excited in the short GNR. It was found that the strong coupling between the dipole and quadrupole modes can be achieved by exciting the T-shaped GNR dimer with a plane wave. Then, we demonstrated the realization of strong dipole–quadrupole–exciton coupling by placing a T-shaped GNR on a tungsten disulfide (WS2) monolayer, which leads to a Rabi splitting as large as ~299 meV. It was confirmed that the simulation results can be well fitted by using a Hamiltonian based on the coupled harmonic oscillator model and the coupling strengths for dipole–quadrupole, dipole–exciton and quadrupole–exciton can be extracted from the fitting results. Our findings open new horizons for realizing strong plasmon–exciton coupling in simple systems and pave the way for constructing novel plasmonic devices for practical applications. Full article
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Article
Resolving Site-Specific Energy Levels of Small-Molecule Donor-Acceptor Heterostructures Close to Metal Contacts
Nanomaterials 2021, 11(6), 1618; https://doi.org/10.3390/nano11061618 - 20 Jun 2021
Viewed by 1392
Abstract
The active material of optoelectronic devices must accommodate for contacts which serve to collect or inject the charge carriers. It is the purpose of this work to find out to which extent properties of organic optoelectronic layers change close to metal contacts compared [...] Read more.
The active material of optoelectronic devices must accommodate for contacts which serve to collect or inject the charge carriers. It is the purpose of this work to find out to which extent properties of organic optoelectronic layers change close to metal contacts compared to known properties of bulk materials. Bottom-up fabrication capabilities of model interfaces under ultrahigh vacuum and single-atom low temperature (LT)-STM spectroscopy with density functional theory (DFT) calculations are used to detect the spatial modifications of electronic states such as frontier-orbitals at interfaces. The system under consideration is made of a silver substrate covered with a blend of C60 and ZnPc molecules of a few monolayers. When C60 and ZnPc are separately adsorbed on Ag(111), they show distinct spectroscopic features in STM. However, when C60 is added to the ZnPc monolayer, it shows scanning tunneling spectra similar to ZnPc, revealing a strong interaction of C60 with the ZnPc induced by the substrate. DFT calculations on a model complex confirm the strong hybridization of C60 with ZnPc layer upon adsorption on Ag(111), thus highlighting the role of boundary layers where the donor-acceptor character is strongly perturbed. The calculation also reveals a significant charge transfer from the Ag to the complex that is likely responsible for a downward shift of the molecular LUMO in agreement with the experiment. Full article
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Bead-Immobilized Multimodal Molecular Beacon-Equipped DNA Machinery for Specific RNA Target Detection: A Prototypical Molecular Nanobiosensor
Nanomaterials 2021, 11(6), 1617; https://doi.org/10.3390/nano11061617 - 20 Jun 2021
Viewed by 1090
Abstract
A variety of nanostructured diagnostic tools have been developed for the precise detection of known genetic variants. Molecular beacon systems are very promising tools due to their specific selectivity coupled with relatively lower cost and time requirements than existing molecular detection tools such [...] Read more.
A variety of nanostructured diagnostic tools have been developed for the precise detection of known genetic variants. Molecular beacon systems are very promising tools due to their specific selectivity coupled with relatively lower cost and time requirements than existing molecular detection tools such as next generation sequencing or real-time PCR (polymerase chain reaction). However, they are prone to errors induced by secondary structure responses to environmental fluctuations, such as temperature and pH. Herein, we report a temperature-insensitive, bead-immobilized, molecular beacon-equipped novel DNA nanostructure for detection of cancer miRNA variants with the consideration of thermodynamics. This system consists of three parts: a molecular beacon for cancer-specific RNA capture, a stem body as a core template, and a single bead for solid-support. This DNA system was selectively bound to nanosized beads using avidin–biotin chemistry. Synthetic DNA nanostructures, designed based on the principle of fluorescence-resonance enhanced transfer, were effectively applied for in vitro cancer-specific RNA detection. Several parameters were optimized for higher performance, with a focus on thermodynamic stability. Theoretical issues regarding the secondary structure of a single molecular beacon and its combinatory forms were also studied. This study provides design guidelines for new sensing systems of miRNA variation for next-generation biotechnological applications. Full article
(This article belongs to the Special Issue Biomedical Applications of Nano-Base Composites)
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Article
Effects of Electrospinning Parameters on the Microstructure of PVP/TiO2 Nanofibers
Nanomaterials 2021, 11(6), 1616; https://doi.org/10.3390/nano11061616 - 20 Jun 2021
Cited by 2 | Viewed by 1085
Abstract
Titanium dioxide has excellent chemical, electrical, and optical properties, as well as good chemical stability. For that reason, it is widely used in many fields of study and industry, such as photocatalysts, organic solar cells, sensors, dental implants, and other applications. Many nanostructures [...] Read more.
Titanium dioxide has excellent chemical, electrical, and optical properties, as well as good chemical stability. For that reason, it is widely used in many fields of study and industry, such as photocatalysts, organic solar cells, sensors, dental implants, and other applications. Many nanostructures of TiO2 have been reported, and electrospinning is an efficient practical technique that has a low cost and high efficiency. In various studies on improving performance, the researchers created nanofibers with suitable microstructures by changing various properties and the many process parameters that can be controlled. In this study, PVP/TiO2 nanofibers were fabricated by the electrospinning process. The diameters of the nanofibers were controlled by various parameters. To understand the effects on the diameter of the nanofibers, various process parameters were controlled: the molecular weight and concentration of the polymers, deionized water, applied voltage, fluid velocity, and concentration of titanium precursor. The average diameter of the PVP nanofibers was controlled in a range of 42.3 nm to 633.0 nm. The average diameter of the PVP/TiO2 nanofibers was also controlled in a range of 63.5 nm to 186.0 nm after heat treatment. Full article
(This article belongs to the Special Issue Semiconductor-Based Nanomaterials for Photocatalytic Applications)
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Article
Morphology and Mechanical Properties of Fossil Diatom Frustules from Genera of Ellerbeckia and Melosira
Nanomaterials 2021, 11(6), 1615; https://doi.org/10.3390/nano11061615 - 20 Jun 2021
Viewed by 852
Abstract
Fossil frustules of Ellerbeckia and Melosira were studied using laboratory-based nano X-ray tomography (nano-XCT), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Three-dimensional (3D) morphology characterization using nondestructive nano-XCT reveals the continuous connection of fultoportulae, tube processes and protrusions. The study confirms [...] Read more.
Fossil frustules of Ellerbeckia and Melosira were studied using laboratory-based nano X-ray tomography (nano-XCT), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Three-dimensional (3D) morphology characterization using nondestructive nano-XCT reveals the continuous connection of fultoportulae, tube processes and protrusions. The study confirms that Ellerbeckia is different from Melosira. Both genera reveal heavily silicified frustules with valve faces linking together and forming cylindrical chains. For this cylindrical architecture of both genera, valve face thickness, mantle wall thickness and copulae thickness change with the cylindrical diameter. Furthermore, EDS reveals that these fossil frustules contain Si and O only, with no other elements in the percentage concentration range. Nanopores with a diameter of approximately 15 nm were detected inside the biosilica of both genera using TEM. In situ micromechanical experiments with uniaxial loading were carried out within the nano-XCT on these fossil frustules to determine the maximal loading force under compression and to describe the fracture behavior. The fracture force of both genera is correlated to the dimension of the fossil frustules. The results from in situ mechanical tests show that the crack initiation starts either at very thin features or at linking structures of the frustules. Full article
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Article
Optimization of Microalga Chlorella vulgaris Magnetic Harvesting
Nanomaterials 2021, 11(6), 1614; https://doi.org/10.3390/nano11061614 - 20 Jun 2021
Cited by 3 | Viewed by 1019
Abstract
Harvesting of microalgae is a crucial step in microalgae-based mass production of different high value-added products. In the present work, magnetic harvesting of Chlorella vulgaris was investigated using microwave-synthesized naked magnetite (Fe3O4) particles with an average crystallite diameter of [...] Read more.
Harvesting of microalgae is a crucial step in microalgae-based mass production of different high value-added products. In the present work, magnetic harvesting of Chlorella vulgaris was investigated using microwave-synthesized naked magnetite (Fe3O4) particles with an average crystallite diameter of 20 nm. Optimization of the most important parameters of the magnetic harvesting process, namely pH, mass ratio (mr) of magnetite particles to biomass (g/g), and agitation speed (rpm) of the C. vulgaris biomass–Fe3O4 particles mixture, was performed using the response surface methodology (RSM) statistical tool. Harvesting efficiencies higher than 99% were obtained for pH 3.0 and mixing speed greater or equal to 350 rpm. Recovery of magnetic particles via detachment was shown to be feasible and the recovery particles could be reused at least five times with high harvesting efficiency. Consequently, the described harvesting approach of C. vulgaris cells leads to an efficient, simple, and quick process, that does not impair the quality of the harvested biomass. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical and Biotechnological Applications)
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Article
Engineering the Composition of Microfibers to Enhance the Remodeling of a Cell-Free Vascular Graft
Nanomaterials 2021, 11(6), 1613; https://doi.org/10.3390/nano11061613 - 20 Jun 2021
Cited by 3 | Viewed by 985
Abstract
The remodeling of vascular grafts is critical for blood vessel regeneration. However, most scaffold materials have limited cell infiltration. In this study, we designed and fabricated a scaffold that incorporates a fast-degrading polymer polydioxanone (PDO) into the microfibrous structure by means of electrospinning [...] Read more.
The remodeling of vascular grafts is critical for blood vessel regeneration. However, most scaffold materials have limited cell infiltration. In this study, we designed and fabricated a scaffold that incorporates a fast-degrading polymer polydioxanone (PDO) into the microfibrous structure by means of electrospinning technology. Blending PDO with base polymer decreases the density of electrospun microfibers yet did not compromise the mechanical and structural properties of the scaffold, and effectively enhanced cell infiltration. We then used this technique to fabricate a tubular scaffold with heparin conjugated to the surface to suppress thrombosis, and the construct was implanted into the carotid artery as a vascular graft in animal studies. This graft significantly promoted cell infiltration, and the biochemical cues such as immobilized stromal cell-derived factor-1α further enhanced cell recruitment and the long-term patency of the grafts. This work provides an approach to optimize the microfeatures of vascular grafts, and will have broad applications in scaffold design and fabrication for regenerative engineering. Full article
(This article belongs to the Special Issue Biocompatibility of Nanomaterials)
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Article
Interfacial Effects and the Nano-Scale Disruption in Adsorbed-Layer of Acrylate Polymer-Tween 80 Fabricated Steroid-Bearing Emulsions: A Rheological Study of Supramolecular Materials
Nanomaterials 2021, 11(6), 1612; https://doi.org/10.3390/nano11061612 - 19 Jun 2021
Viewed by 1040
Abstract
The effect of polymer adsorption on the stability and viable shelf life of 55 μm diameter oil-in-water (O/W) emulsions containing the steroid, betamethasone 21-phosphate was investigated. Two acrylate polymers, Carbopol® 971P and 974P, were added in the role of emulsion stabilizers to [...] Read more.
The effect of polymer adsorption on the stability and viable shelf life of 55 μm diameter oil-in-water (O/W) emulsions containing the steroid, betamethasone 21-phosphate was investigated. Two acrylate polymers, Carbopol® 971P and 974P, were added in the role of emulsion stabilizers to a model system, representing a non-ionic low molecular weight surfactant-stabilized emulsion (topically applied medicinal cream). For the purposes of this study the dosage of the viscosifier was maintained below 1% w/v and consequently, the consistency of the emulsion was measured in the diluted form. One of the polymers was responsible for elevated degrees of droplet creaming and coalescence and this was closely linked to its surface tension lowering capacity. This lowering was seen at 62 mN/m compared to the routine values at equivalent concentrations of 68 mN/m and 35 mN/m for the betamethasone drug and non-ionic surfactant-Tween 80, respectively. The same polymer also demonstrated a predisposition to form low-micron and greater sized aggregates of nanoparticles that led to extensive flocculation and the formation of a sedimentary precipitate, formed from an amalgam of the components found in the creamed droplet layer. Full article
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Article
Nanoscale Strontium-Substituted Hydroxyapatite Pastes and Gels for Bone Tissue Regeneration
Nanomaterials 2021, 11(6), 1611; https://doi.org/10.3390/nano11061611 - 19 Jun 2021
Cited by 4 | Viewed by 1247
Abstract
Injectable nanoscale hydroxyapatite (nHA) systems are highly promising biomaterials to address clinical needs in bone tissue regeneration, due to their excellent biocompatibility, bioinspired nature, and ability to be delivered in a minimally invasive manner. Bulk strontium-substituted hydroxyapatite (SrHA) is reported to encourage bone [...] Read more.
Injectable nanoscale hydroxyapatite (nHA) systems are highly promising biomaterials to address clinical needs in bone tissue regeneration, due to their excellent biocompatibility, bioinspired nature, and ability to be delivered in a minimally invasive manner. Bulk strontium-substituted hydroxyapatite (SrHA) is reported to encourage bone tissue growth by stimulating bone deposition and reducing bone resorption, but there are no detailed reports describing the preparation of a systematic substitution up to 100% at the nanoscale. The aim of this work was therefore to fabricate systematic series (0–100 atomic% Sr) of SrHA pastes and gels using two different rapid-mixing methodological approaches, wet precipitation and sol-gel. The full range of nanoscale SrHA materials were successfully prepared using both methods, with a measured substitution very close to the calculated amounts. As anticipated, the SrHA samples showed increased radiopacity, a beneficial property to aid in vivo or clinical monitoring of the material in situ over time. For indirect methods, the greatest cell viabilities were observed for the 100% substituted SrHA paste and gel, while direct viability results were most likely influenced by material disaggregation in the tissue culture media. It was concluded that nanoscale SrHAs were superior biomaterials for applications in bone surgery, due to increased radiopacity and improved biocompatibility. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)
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Structural Transitions and Stability of FAPbI3 and MAPbI3: The Role of Interstitial Water
Nanomaterials 2021, 11(6), 1610; https://doi.org/10.3390/nano11061610 - 18 Jun 2021
Cited by 1 | Viewed by 1136
Abstract
We studied the influence of water on the structural stability and transformations of MAPI and FAPI by anelastic and dielectric spectroscopies under various temperature and H2O partial pressure protocols. Before discussing the new results in terms of interstitial water in MAPI [...] Read more.
We studied the influence of water on the structural stability and transformations of MAPI and FAPI by anelastic and dielectric spectroscopies under various temperature and H2O partial pressure protocols. Before discussing the new results in terms of interstitial water in MAPI and FAPI, the literature is briefly reviewed, in search of other studies and evidences on interstitial water in hybrid halide perovskites. In hydrated MAPI, the elastic anomaly between the cubic α and tetragonal β phases may be depressed by more than 50%, demonstrating that there are H2O molecules dispersed in the perovskite lattice in interstitial form, that hinder the long range tilting of the PbI6 octahedra. Instead, in FAPI, interstitial water accelerates in both senses the reconstructive transformations between 3D α and 1D δ phases, which is useful during the crystallization of the α phase. On the other hand, the interstitial H2O molecules increase the effective size of the MA and FA cations to which are bonded, shifting the thermodynamic equilibrium from the compact perovskite structure to the open δ and hydrated phases of loosely bonded chains of PbI6 octahedra. For this reason, when fabricating devices based on hybrid metal-organic halide perovskites, it is important to reduce the content of interstitial water as much as possible before encapsulation. Full article
(This article belongs to the Special Issue Mesoporous Materials and Nanoscale Phenomena in Hybrid Photovoltaics)
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Article
Fabrication of Reusable Carboxymethyl Cellulose/Graphene Oxide Composite Aerogel with Large Surface Area for Adsorption of Methylene Blue
Nanomaterials 2021, 11(6), 1609; https://doi.org/10.3390/nano11061609 - 18 Jun 2021
Cited by 9 | Viewed by 1183
Abstract
A highly efficient adsorbent for methylene blue (MB) adsorption was developed by combination of carboxymethyl cellulose (CMC) and graphene oxide (GO) via a simple one-step hydrothermal method. The as-synthesized CMC/GO composite aerogel has a mesoporous structure with an average pore diameter of 30 [...] Read more.
A highly efficient adsorbent for methylene blue (MB) adsorption was developed by combination of carboxymethyl cellulose (CMC) and graphene oxide (GO) via a simple one-step hydrothermal method. The as-synthesized CMC/GO composite aerogel has a mesoporous structure with an average pore diameter of 30 nm and a high specific surface area of 800.85 m2·g−1. Moreover, the CMC/GO composite aerogel demonstrates a significant selectivity for the dye adsorption, especially for MB, where its adsorption capacity can reach 244.99 mg·g−1 with an excellent recyclability for more than nine times. Thus, the prepared CMC/GO composite aerogel would be an effective adsorbent for dyes adsorption, owing to the merits of high efficiency, reusability, and eco-friendliness. Full article
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Article
Spiky Gold Nanoparticles for the Photothermal Eradication of Colon Cancer Cells
Nanomaterials 2021, 11(6), 1608; https://doi.org/10.3390/nano11061608 - 18 Jun 2021
Cited by 2 | Viewed by 1413
Abstract
Colorectal cancer (CRC) is a widespread and lethal disease. Relapses of the disease and metastasis are very common in instances of CRC, so adjuvant therapies have a crucial role in its treatment. Systemic toxic effects and the development of resistance during therapy limit [...] Read more.
Colorectal cancer (CRC) is a widespread and lethal disease. Relapses of the disease and metastasis are very common in instances of CRC, so adjuvant therapies have a crucial role in its treatment. Systemic toxic effects and the development of resistance during therapy limit the long-term efficacy of existing adjuvant therapeutic approaches. Consequently, the search for alternative strategies is necessary. Photothermal therapy (PTT) represents an innovative treatment for cancer with great potential. Here, we synthesize branched gold nanoparticles (BGNPs) as attractive agents for the photothermal eradication of colon cancer cells. By controlling the NP growth process, large absorption in the first NIR biological window was obtained. The FBS dispersed BGNPs are stable in physiological-like environments and show an extremely efficient light-to-heat conversion capability when irradiated with an 808-nm laser. Sequential cycles of heating and cooling do not affect the BGNP stability. The uptake of BGNPs in colon cancer cells was confirmed using flow cytometry and confocal microscopy, exploiting their intrinsic optical properties. In dark conditions, BGNPs are fully biocompatible and do not compromise cell viability, while an almost complete eradication of colon cancer cells was observed upon incubation with BGNPs and irradiation with an 808-nm laser source. The PTT treatment is characterized by an extremely rapid onset of action that leads to cell membrane rupture by induced hyperthermia, which is the trigger that promotes cancer cell death. Full article
(This article belongs to the Special Issue Application of Nanomaterials in Biomedical Imaging and Cancer Therapy)
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Article
Reducing Defects in Organic-Lead Halide Perovskite Film by Delayed Thermal Annealing Combined with KI/I2 for Efficient Perovskite Solar Cells
Nanomaterials 2021, 11(6), 1607; https://doi.org/10.3390/nano11061607 - 18 Jun 2021
Cited by 3 | Viewed by 1131
Abstract
This study improved quality of CH3NH3PbI3 (MAPbI3) perovskite films by delaying thermal annealing in the spin coating process and introducing KI and I2 to prepare MAPbI3 films that were low in defects for high-efficiency [...] Read more.
This study improved quality of CH3NH3PbI3 (MAPbI3) perovskite films by delaying thermal annealing in the spin coating process and introducing KI and I2 to prepare MAPbI3 films that were low in defects for high-efficiency perovskite solar cells. The influences of delayed thermal annealing time after coating the MAPbI3 perovskite layer on the crystallized perovskite, the morphology control of MAPbI3 films, and the photoelectric conversion efficiency of solar cells were investigated. The optimal delayed thermal annealing time was found to be 60 min at room temperature. The effect of KI/I2 additives on the growth of MAPbI3 films and the corresponding optimal delayed thermal annealing time were further investigated. The addition of KI/I2 can improve perovskite crystallinity, and the conductivity and carrier mobility of MAPbI3 films. Under optimized conditions, the photoelectric conversion efficiency of MAPbI3 perovskite solar cells can reach 19.36% under standard AM1.5G solar illumination of 100 mW/cm2. Full article
(This article belongs to the Special Issue Applications of Metal Halide Perovskites in Optoelectronic Devices)
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Article
Effects of UV Irradiation and Storage on the Performance of Inverted Red Quantum-Dot Light-Emitting Diodes
Nanomaterials 2021, 11(6), 1606; https://doi.org/10.3390/nano11061606 - 18 Jun 2021
Cited by 1 | Viewed by 969
Abstract
We report the effects of ultraviolet (UV) irradiation and storage on the performance of ZnO-based inverted quantum-dot light-emitting diodes (QLEDs). The effects of UV irradiation on the electrical properties of ZnO nanoparticles (NPs) were investigated. We demonstrate that the charge balance was enhanced [...] Read more.
We report the effects of ultraviolet (UV) irradiation and storage on the performance of ZnO-based inverted quantum-dot light-emitting diodes (QLEDs). The effects of UV irradiation on the electrical properties of ZnO nanoparticles (NPs) were investigated. We demonstrate that the charge balance was enhanced by improving the electron injection. The maximum external quantum efficiency (EQE) and power efficiency (PE) of QLEDs were increased by 26% and 143% after UV irradiation for 15 min. In addition, we investigated the storage stabilities of the inverted QLEDs. During the storage period, the electron current from ZnO gradually decreased, causing a reduction in the device current. However, the QLEDs demonstrated improvements in maximum EQE by 20.7% after two days of storage. Our analysis indicates that the suppression of exciton quenching at the interface of ZnO and quantum dots (QDs) during the storage period could result in the enhancement of EQE. This study provides a comprehension of the generally neglected factors, which could be conducive to the realization of high-efficiency and highly storage-stable practical applications. Full article
(This article belongs to the Special Issue Nanomaterials for Printed Displays)
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Article
Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles
Nanomaterials 2021, 11(6), 1605; https://doi.org/10.3390/nano11061605 - 18 Jun 2021
Cited by 2 | Viewed by 926
Abstract
Gold nanoparticles (~10 nm) were deposited on titanium dioxide nanoparticles (~21 nm) and the material obtained was characterized using IR, UV-Vis, N2 adsorption–desorption isotherm, DLS, EDS (EDX), TEM, XPS, and XRD techniques. It was found that the methylene blue dye is degraded [...] Read more.
Gold nanoparticles (~10 nm) were deposited on titanium dioxide nanoparticles (~21 nm) and the material obtained was characterized using IR, UV-Vis, N2 adsorption–desorption isotherm, DLS, EDS (EDX), TEM, XPS, and XRD techniques. It was found that the methylene blue dye is degraded in the presence of this material when using hydrogen peroxide as the oxidant. Tests were performed at 2, 4, 6, and 24 h, with hydrogen peroxide contents varying from 1 to 5 mg/mL. Longer exposure time and a higher content of oxidant led to the degradation of methylene blue dye at up to 90%. The material can be reused several times with no loss of activity. Full article
(This article belongs to the Special Issue Structure, Synthesis and Applications of TiO2-Based Nanomaterials)
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Article
Quantitative Assessment of Trout Fish Spoilage with a Single Nanowire Gas Sensor in a Thermal Gradient
Nanomaterials 2021, 11(6), 1604; https://doi.org/10.3390/nano11061604 - 18 Jun 2021
Cited by 7 | Viewed by 1027
Abstract
The response of a single tin oxide nanowire was collected at different temperatures to create a virtual array of sensors working as a nano-electronic nose. The single nanowire, acting as a chemiresistor, was first tested with pure ammonia and then used to determine [...] Read more.
The response of a single tin oxide nanowire was collected at different temperatures to create a virtual array of sensors working as a nano-electronic nose. The single nanowire, acting as a chemiresistor, was first tested with pure ammonia and then used to determine the freshness status of trout fish (Oncorhynchus mykiss) in a rapid and non-invasive way. The gas sensor reacts to total volatile basic nitrogen, detecting the freshness status of the fish samples in less than 30 s. The sensor response at different temperatures correlates well with the total viable count (TVC), demonstrating that it is a good (albeit indirect) way of measuring the bacterial population in the sample. The nano-electronic nose is not only able to classify the samples according to their degree of freshness but also to quantitatively estimate the concentration of microorganisms present. The system was tested with samples stored at different temperatures and classified them perfectly (100%), estimating their log(TVC) with an error lower than 5%. Full article
(This article belongs to the Special Issue Nanostructured Materials for Gas Sensor Applications)
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Article
Using Graphene-Based Composite Materials to Boost Anti-Corrosion and Infrared-Stealth Performance of Epoxy Coatings
Nanomaterials 2021, 11(6), 1603; https://doi.org/10.3390/nano11061603 - 18 Jun 2021
Viewed by 1113
Abstract
Corrosion prevention and infrared (IR) stealth are conflicting goals. While graphene nanosheets (GN) provide an excellent physical barrier against corrosive agent diffusion, thus lowering the permeability of anti-corrosion coatings, they have the side-effect of decreasing IR stealth. In this work, the anti-corrosion properties [...] Read more.
Corrosion prevention and infrared (IR) stealth are conflicting goals. While graphene nanosheets (GN) provide an excellent physical barrier against corrosive agent diffusion, thus lowering the permeability of anti-corrosion coatings, they have the side-effect of decreasing IR stealth. In this work, the anti-corrosion properties of 100-μm-thick composite epoxy coatings with various concentrations (0.01–1 wt.%) of GN fillers thermally reduced at different temperatures (300 °C, 700 °C, 1100 °C) are first compared. The performance was characterized by potentiodynamic polarization scanning, electrochemical impedance spectroscopy, water contact angle and salt spray tests. The corrosion resistance for coatings was found to be optimum at a very low filler concentration (0.05 wt.%). The corrosion current density was 4.57 × 10−11 A/cm2 for GN reduced at 1100 °C, showing no degradation after 500 h of salt-spray testing: a significant improvement over the anti-corrosion behavior of epoxy coatings. Further, to suppress the high IR thermal signature of GN and epoxy, Al was added to the optimized composite at different concentrations. The increased IR emissivity due to GN was not only eliminated but was in fact reduced relative to the pure epoxy. These optimized coatings of Al-GN-epoxy not only exhibited greatly reduced IR emissivity but also showed no sign of corrosion after 500 h of salt spray test. Full article
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Article
Twisting of a Pristine α-Fe Nanowire: From Wild Dislocation Avalanches to Mild Local Amorphization
Nanomaterials 2021, 11(6), 1602; https://doi.org/10.3390/nano11061602 - 18 Jun 2021
Cited by 2 | Viewed by 759
Abstract
The torsion of pristine α-Fe nanowires was studied by molecular dynamics simulations. Torsion-induced plastic deformation in pristine nanowires is divided into two regimes. Under weak torsion, plastic deformation leads to dislocation nucleation and propagation. Twisting-induced dislocations are mainly 12<111> screw dislocations [...] Read more.
The torsion of pristine α-Fe nanowires was studied by molecular dynamics simulations. Torsion-induced plastic deformation in pristine nanowires is divided into two regimes. Under weak torsion, plastic deformation leads to dislocation nucleation and propagation. Twisting-induced dislocations are mainly 12<111> screw dislocations in a <112>-oriented nanowire. The nucleation and propagation of these dislocations were found to form avalanches which generate the emission of energy jerks. Their probability distribution function (PDF) showed power laws with mixing between different energy exponents. The mixing stemmed from simultaneous axial and radial dislocation movements. The power-law distribution indicated strongly correlated ‘wild’ dislocation dynamics. At the end of this regime, the dislocation pattern was frozen, and further twisting of the nanowire did not change the dislocation pattern. Instead, it induced local amorphization at the grip points at the ends of the sample. This “melting” generated highly dampened, mild avalanches. We compared the deformation mechanisms of twinned and pristine α-Fe nanowires under torsion. Full article
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Article
Electrospun Nanostructured Membrane Engineering Using Reverse Osmosis Recycled Modules: Membrane Distillation Application
Nanomaterials 2021, 11(6), 1601; https://doi.org/10.3390/nano11061601 - 18 Jun 2021
Cited by 1 | Viewed by 864
Abstract
As a consequence of the increase in reverse osmosis (RO) desalination plants, the number of discarded RO modules for 2020 was estimated to be 14.8 million annually. Currently, these discarded modules are disposed of in nearby landfills generating high volumes of waste. In [...] Read more.
As a consequence of the increase in reverse osmosis (RO) desalination plants, the number of discarded RO modules for 2020 was estimated to be 14.8 million annually. Currently, these discarded modules are disposed of in nearby landfills generating high volumes of waste. In order to extend their useful life, in this research study, we propose recycling and reusing the internal components of the discarded RO modules, membranes and spacers, in membrane engineering for membrane distillation (MD) technology. After passive cleaning with a sodium hypochlorite aqueous solution, these recycled components were reused as support for polyvinylidene fluoride nanofibrous membranes prepared by electrospinning technique. The prepared membranes were characterized by different techniques and, finally, tested in desalination of high saline solutions (brines) by direct contact membrane distillation (DCMD). The effect of the electrospinning time, which is the same as the thickness of the nanofibrous layer, was studied in order to optimize the permeate flux together with the salt rejection factor and to obtain robust membranes with stable DCMD desalination performance. When the recycled RO membrane or the permeate spacer were used as supports with 60 min electrospinning time, good permeate fluxes were achieved, 43.2 and 18.1 kg m−2 h−1, respectively; with very high salt rejection factors, greater than 99.99%. These results are reasonably competitive compared to other supported and unsupported MD nanofibrous membranes. In contrast, when using the feed spacer as support, inhomogeneous structures were observed on the electrospun nanofibrous layer due to the special characteristics of this spacer resulting in low salt rejection factors and mechanical properties of the electrospun nanofibrous membrane. Full article
(This article belongs to the Special Issue Progress in Electrospun Nanofibers and Nanocomposites)
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Article
The Influence of a Knitted Hydrophilic Prosthesis of Blood Vessels on the Activation of Coagulation System—In Vitro Study
Nanomaterials 2021, 11(6), 1600; https://doi.org/10.3390/nano11061600 - 18 Jun 2021
Viewed by 739
Abstract
The replacement of affected blood vessels of the polymer material can cause imbalances in the blood haemostatic system. Changes in blood after the implantation of vascular grafts depend not only on the chemical composition but also on the degree of surface wettability. The [...] Read more.
The replacement of affected blood vessels of the polymer material can cause imbalances in the blood haemostatic system. Changes in blood after the implantation of vascular grafts depend not only on the chemical composition but also on the degree of surface wettability. The Dallon® H unsealed hydrophilic knitted vascular prosthesis double velour was assessed at work and compare with hydrophobic vascular prosthesis Dallon®. Spectrophotometric studies were performed in the infrared and differential scanning calorimetry, which confirmed the effectiveness of the process of modifying vascular prostheses. Determination of the parameters of coagulation time of blood after contact in vitro with Dallon® H vascular prosthesis was also carried out. Prolongation of activated thromboplastin time, decreased activity of factor XII, IX and VIII, were observed. The prolonged thrombin and fibrinogen were reduced in the initial period of the experiment. The activity of plasminogen and antithrombin III and protein C were at the level of control value. The observed changes in the values of determined parameters blood coagulation do not exceed the range of referential values for those indexes. The observed changes are the result of considerable blood absorptiveness by the prosthesis of blood vessels and their sealing. Full article
(This article belongs to the Special Issue Advanced Materials for Bio-Related Applications)
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Review
Nanomaterial Databases: Data Sources for Promoting Design and Risk Assessment of Nanomaterials
Nanomaterials 2021, 11(6), 1599; https://doi.org/10.3390/nano11061599 - 18 Jun 2021
Cited by 9 | Viewed by 1150
Abstract
Nanomaterials have drawn increasing attention due to their tunable and enhanced physicochemical and biological performance compared to their conventional bulk materials. Owing to the rapid expansion of the nano-industry, large amounts of data regarding the synthesis, physicochemical properties, and bioactivities of nanomaterials have [...] Read more.
Nanomaterials have drawn increasing attention due to their tunable and enhanced physicochemical and biological performance compared to their conventional bulk materials. Owing to the rapid expansion of the nano-industry, large amounts of data regarding the synthesis, physicochemical properties, and bioactivities of nanomaterials have been generated. These data are a great asset to the scientific community. However, the data are on diverse aspects of nanomaterials and in different sources and formats. To help utilize these data, various databases on specific information of nanomaterials such as physicochemical characterization, biomedicine, and nano-safety have been developed and made available online. Understanding the structure, function, and available data in these databases is needed for scientists to select appropriate databases and retrieve specific information for research on nanomaterials. However, to our knowledge, there is no study to systematically compare these databases to facilitate their utilization in the field of nanomaterials. Therefore, we reviewed and compared eight widely used databases of nanomaterials, aiming to provide the nanoscience community with valuable information about the specific content and function of these databases. We also discuss the pros and cons of these databases, thus enabling more efficient and convenient utilization. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)
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