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Nanomaterials, Volume 9, Issue 12 (December 2019) – 153 articles

Cover Story (view full-size image): BiSI nanorod-based films were fabricated at a low temperature of 200 °C via two-step solution method which consists of Bi2S3 formation and its conversion to BiSI. Their structure, absorption, and morphology were successfully controlled by tuning key experimental parameters, such as the Bi:S molar ratio and the number of repetitions of each step. In addition, the electronic structure was investigated and discussed for solar cell applications. Our work is expected to contribute to fabricating environment-friendly photovoltaic materials and developing related solar cells. View this paper.
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Open AccessArticle
Solid-State Solar Energy Conversion from WO3 Nano and Microstructures with Charge Transportation and Light-Scattering Characteristics
Nanomaterials 2019, 9(12), 1797; https://doi.org/10.3390/nano9121797 - 17 Dec 2019
Cited by 5 | Viewed by 971
Abstract
Solar energy conversion devices composed of highly crystalline gel polymers with disk-WO3 nanostructure and plate-WO3 microstructures (D-WO3 and P-WO3, respectively) exhibited higher power conversion efficiency than those with a gel electrolyte. In this study, D-WO3 and P-WO [...] Read more.
Solar energy conversion devices composed of highly crystalline gel polymers with disk-WO3 nanostructure and plate-WO3 microstructures (D-WO3 and P-WO3, respectively) exhibited higher power conversion efficiency than those with a gel electrolyte. In this study, D-WO3 and P-WO3 were prepared using a hydrothermal process and their structural and morphological features were investigated for application in solar energy conversion devices. The P-WO3 solid-state electrolyte significantly enhanced the cell performance owing to its charge transportation and light-scattering characteristics. The P-WO3 solid-state electrolyte showed a power conversion efficiency of 6.3%, which is higher than those of the gel (4.2%) and D-WO3 solid-state (5.5%) electrolytes. The electro-chemical impedance spectroscopy (EIS), intensity-modulated voltage spectroscopy (IMVS), diffuse reflectance, and incident photon-to-current conversion efficiency (IPCE) analysis results showed that the P-WO3 solid-state electrolyte showed improved charge transportation and light scattering, and hence enhanced the cell performance. Full article
(This article belongs to the Special Issue Metal-Oxide Nanomaterials for Energy Application)
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Open AccessArticle
Gram-Scale Synthesis of Bimetallic ZIFs and Their Thermal Conversion to Nanoporous Carbon Materials
Nanomaterials 2019, 9(12), 1796; https://doi.org/10.3390/nano9121796 - 17 Dec 2019
Cited by 5 | Viewed by 911
Abstract
The hybrid metal-organic frameworks (MOFs) with different Zn2+/Co2+ ratios are synthesized at room temperature with deionized water as the solvent. This use of deionized water can increase the yield of hybrid MOFs (up to 65–70%). After the pyrolysis, the obtained [...] Read more.
The hybrid metal-organic frameworks (MOFs) with different Zn2+/Co2+ ratios are synthesized at room temperature with deionized water as the solvent. This use of deionized water can increase the yield of hybrid MOFs (up to 65–70%). After the pyrolysis, the obtained nanoporous carbons (NPCs) show a decrease in the surface area, in which the highest surface area is 655 m2 g−1. The as-prepared NPCs are subjected to activation with KOH in order to increase their surface area and convert cobalt nanoparticles (Co NPs) to Co oxides. These activated carbons are applied to electrical double-layer capacitors (EDLCs) and pseudocapacitors due to the presence of CoO and Co3O4 nanoparticles in the carbon framework, leading to significantly enhanced specific capacitance as compared to that of pristine NPCs. This synthetic method can be utilized in future research to enhance pseudocapacitance further while maintaining the maximum surface area of the carbon materials. Full article
(This article belongs to the Special Issue Nanospace Materials)
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Open AccessArticle
Electrodeposition of Ti-Doped Hierarchically Mesoporous Silica Microspheres/Tungsten Oxide Nanocrystallines Hybrid Films and Their Electrochromic Performance
Nanomaterials 2019, 9(12), 1795; https://doi.org/10.3390/nano9121795 - 17 Dec 2019
Cited by 3 | Viewed by 834
Abstract
In this paper, a novel Ti-doped hierarchically mesoporous silica microspheres/tungsten oxide (THMS/WO3) hybrid film was prepared by simultaneous electrodeposition of Ti-doped hierarchically mesoporous silica microspheres (THMSs) and WO3 nanocrystallines onto the fluoride doped tin dioxide (FTO) coated glass substrate. It [...] Read more.
In this paper, a novel Ti-doped hierarchically mesoporous silica microspheres/tungsten oxide (THMS/WO3) hybrid film was prepared by simultaneous electrodeposition of Ti-doped hierarchically mesoporous silica microspheres (THMSs) and WO3 nanocrystallines onto the fluoride doped tin dioxide (FTO) coated glass substrate. It is demonstrated that the incorporation of THMSs resulted in the hybrid film with improved electrochromic property. Besides, the content of THMSs plays an important role on the electrochromic property of the hybrid film. An excellent electrochromic THMS/WO3 hybrid film with good optical modulation (52.00% at 700 nm), high coloration efficiency (88.84 cm2 C−1 at 700 nm), and superior cycling stability can be prepared by keeping the weight ratio of Na2WO4·2H2O (precursor of WO3):THMSs at 15:1. The outstanding electrochromic performances of the THMS/WO3 hybrid film were mainly attributed to the porous structure, which facilitates the charge-transfer, promotes the electrolyte infiltration and alleviates the expansion of the film during Li+ insertion. This kind of porous THMS/WO3 hybrid film is promising for a wide range of applications in smart homes, green buildings, airplanes, and automobiles. Full article
(This article belongs to the Section Nanocomposite Materials)
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Open AccessArticle
Dewetted Gold Nanostructures onto Exfoliated Graphene Paper as High Efficient Glucose Sensor
Nanomaterials 2019, 9(12), 1794; https://doi.org/10.3390/nano9121794 - 16 Dec 2019
Viewed by 726
Abstract
Non-enzymatic electrochemical glucose sensing was obtained by gold nanostructures on graphene paper, produced by laser or thermal dewetting of 1.6 and 8 nm-thick Au layers, respectively. Nanosecond laser annealing produces spherical nanoparticles (AuNPs) through the molten-phase dewetting of the gold layer and simultaneous [...] Read more.
Non-enzymatic electrochemical glucose sensing was obtained by gold nanostructures on graphene paper, produced by laser or thermal dewetting of 1.6 and 8 nm-thick Au layers, respectively. Nanosecond laser annealing produces spherical nanoparticles (AuNPs) through the molten-phase dewetting of the gold layer and simultaneous exfoliation of the graphene paper. The resulting composite electrodes were characterized by X-ray photoelectron spectroscopy, cyclic voltammetry, scanning electron microscopy, micro Raman spectroscopy and Rutherford back-scattering spectrometry. Laser dewetted electrode presents graphene nanoplatelets covered by spherical AuNPs. The sizes of AuNPs are in the range of 10–150 nm. A chemical shift in the XPS Au4f core-level of 0.25–0.3 eV suggests the occurrence of AuNPs oxidation, which are characterized by high stability under the electrochemical test. Thermal dewetting leads to electrodes characterized by faceted not oxidized gold structures. Glucose was detected in alkali media at potential of 0.15–0.17 V vs. saturated calomel electrode (SCE), in the concentration range of 2.5μM−30 mM, exploiting the peak corresponding to the oxidation of two electrons. Sensitivity of 1240 µA mM−1 cm−2, detection limit of 2.5 μM and quantifications limit of 20 μM were obtained with 8 nm gold equivalent thickness. The analytical performances are very promising and comparable to the actual state of art concerning gold based electrodes. Full article
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Open AccessArticle
Trastuzumab-Targeted Biodegradable Nanoparticles for Enhanced Delivery of Dasatinib in HER2+ Metastasic Breast Cancer
Nanomaterials 2019, 9(12), 1793; https://doi.org/10.3390/nano9121793 - 16 Dec 2019
Cited by 7 | Viewed by 982
Abstract
Dasatinib (DAS) is a multikinase inhibitor that acts on several signaling kinases. DAS is used as a second-line treatment for chronic accelerated myeloid and Philadelphia chromosome-positive acute lymphoblastic leukemia. The therapeutic potential of DAS in other solid tumours is under evaluation. As for [...] Read more.
Dasatinib (DAS) is a multikinase inhibitor that acts on several signaling kinases. DAS is used as a second-line treatment for chronic accelerated myeloid and Philadelphia chromosome-positive acute lymphoblastic leukemia. The therapeutic potential of DAS in other solid tumours is under evaluation. As for many other compounds, an improvement in their pharmacokinetic and delivery properties would potential augment the efficacy. Antibody-targeted biodegradable nanoparticles can be useful in targeted cancer therapy. DAS has shown activity in human epidermal growth factor receptor 2 (HER2) positive tumors, so conjugation of this compound with the anti-HER2 antibody trastuzumab (TAB) with the use of nanocarriers could improve its efficacy. TAB-targeted DAS-loaded nanoparticles were generated by nanotechnology. The guided nanocarriers enhanced in vitro cytotoxicity of DAS against HER2 human breast cancer cell lines. Cellular mechanistic, release studies and nanoparticles stability were undertaken to provide evidences for positioning DAS-loaded TAB-targeted nanoparticles as a potential strategy for further development in HER2-overexpressing breast cancer therapy. Full article
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Open AccessArticle
Advanced Surface Probing Using a Dual-Mode NSOM–AFM Silicon-Based Photosensor
Nanomaterials 2019, 9(12), 1792; https://doi.org/10.3390/nano9121792 - 16 Dec 2019
Cited by 1 | Viewed by 736
Abstract
A feasibility analysis is performed for the development and integration of a near-field scanning optical microscope (NSOM) tip–photodetector operating in the visible wavelength domain of an atomic force microscope (AFM) cantilever, involving simulation, processing, and measurement. The new tip–photodetector consists of a platinum–silicon [...] Read more.
A feasibility analysis is performed for the development and integration of a near-field scanning optical microscope (NSOM) tip–photodetector operating in the visible wavelength domain of an atomic force microscope (AFM) cantilever, involving simulation, processing, and measurement. The new tip–photodetector consists of a platinum–silicon truncated conical photodetector sharing a subwavelength aperture, and processing uses advanced nanotechnology tools on a commercial silicon cantilever. Such a combined device enables a dual-mode usage of both AFM and NSOM measurements when collecting the reflected light directly from the scanned surface, while having a more efficient light collection process. In addition to its quite simple fabrication process, it is demonstrated that the AFM tip on which the photodetector is processed remains operational (i.e., the AFM imaging capability is not altered by the process). The AFM–NSOM capability of the processed tip is presented, and preliminary results show that AFM capability is not significantly affected and there is an improvement in surface characterization in the scanning proof of concept. Full article
(This article belongs to the Special Issue Nano Fabrications of Solid-State Sensors and Sensor Systems)
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Open AccessReview
Recent Advances in Magnetite Nanoparticle Functionalization for Nanomedicine
Nanomaterials 2019, 9(12), 1791; https://doi.org/10.3390/nano9121791 - 16 Dec 2019
Cited by 15 | Viewed by 1143
Abstract
Functionalization of nanomaterials can enhance and modulate their properties and behaviour, enabling characteristics suitable for medical applications. Magnetite (Fe3O4) nanoparticles are one of the most popular types of nanomaterials used in this field, and many technologies being already translated [...] Read more.
Functionalization of nanomaterials can enhance and modulate their properties and behaviour, enabling characteristics suitable for medical applications. Magnetite (Fe3O4) nanoparticles are one of the most popular types of nanomaterials used in this field, and many technologies being already translated in clinical practice. This article makes a summary of the surface modification and functionalization approaches presented lately in the scientific literature for improving or modulating magnetite nanoparticles for their applications in nanomedicine. Full article
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Open AccessArticle
Multifunctional Nanostructures and Nanopocket Particles Fabricated by Nanoimprint Lithography
Nanomaterials 2019, 9(12), 1790; https://doi.org/10.3390/nano9121790 - 16 Dec 2019
Viewed by 882
Abstract
Nanostructured surfaces and nanoparticles are already widely employed in many different fields of research, and there is an ever-growing demand for reliable, reproducible and scalable nanofabrication methods. This is especially valid for multifunctional nanomaterials with physical properties that are tailored for specific applications. [...] Read more.
Nanostructured surfaces and nanoparticles are already widely employed in many different fields of research, and there is an ever-growing demand for reliable, reproducible and scalable nanofabrication methods. This is especially valid for multifunctional nanomaterials with physical properties that are tailored for specific applications. Here, we report on the fabrication of two types of nanomaterials. Specifically, we present surfaces comprising a highly uniform array of elliptical pillars as well as nanoparticles with the shape of nanopockets, possessing nano-cavities. The structures are fabricated by nanoimprint lithography, physical and wet-chemical etching and sputter deposition of thin films of various materials to achieve a multifunctional nanomaterial with defined optical and magnetic properties. We show that the nanopockets can be transferred to solution, yielding a nanoparticle dispersion. All fabrication steps are carefully characterized by microscopic and optical methods. Additionally, we show optical simulation results that are in good agreement with the experimentally obtained data. Thus, this versatile method allows to fabricate nanomaterials with specific tailor-made physical properties that can be designed by modelling prior to the actual fabrication process. Finally, we discuss possible application areas of these nanomaterials, which range from biology and medicine to electronics, photovoltaics and photocatalysis. Full article
(This article belongs to the Section Synthesis, Interfaces and Nanostructures)
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Open AccessReview
The Fabrication of Micro/Nano Structures by Laser Machining
Nanomaterials 2019, 9(12), 1789; https://doi.org/10.3390/nano9121789 - 16 Dec 2019
Cited by 4 | Viewed by 1704
Abstract
Micro/nano structures have unique optical, electrical, magnetic, and thermal properties. Studies on the preparation of micro/nano structures are of considerable research value and broad development prospects. Several micro/nano structure preparation techniques have already been developed, such as photolithography, electron beam lithography, focused ion [...] Read more.
Micro/nano structures have unique optical, electrical, magnetic, and thermal properties. Studies on the preparation of micro/nano structures are of considerable research value and broad development prospects. Several micro/nano structure preparation techniques have already been developed, such as photolithography, electron beam lithography, focused ion beam techniques, nanoimprint techniques. However, the available geometries directly implemented by those means are limited to the 2D mode. Laser machining, a new technology for micro/nano structural preparation, has received great attention in recent years for its wide application to almost all types of materials through a scalable, one-step method, and its unique 3D processing capabilities, high manufacturing resolution and high designability. In addition, micro/nano structures prepared by laser machining have a wide range of applications in photonics, Surface plasma resonance, optoelectronics, biochemical sensing, micro/nanofluidics, photofluidics, biomedical, and associated fields. In this paper, updated achievements of laser-assisted fabrication of micro/nano structures are reviewed and summarized. It focuses on the researchers’ findings, and analyzes materials, morphology, possible applications and laser machining of micro/nano structures in detail. Seven kinds of materials are generalized, including metal, organics or polymers, semiconductors, glass, oxides, carbon materials, and piezoelectric materials. In the end, further prospects to the future of laser machining are proposed. Full article
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Open AccessArticle
Second Harmonic Generation for Moisture Monitoring in Dimethoxyethane at a Gold-Solvent Interface Using Plasmonic Structures
Nanomaterials 2019, 9(12), 1788; https://doi.org/10.3390/nano9121788 - 16 Dec 2019
Viewed by 601
Abstract
Second harmonic generation (SHG) is forbidden from most bulk metals because metals are characterized by centrosymmetric symmetry. Adsorption or desorption of molecules at the metal interface can break the symmetry and lead to SHG responses. Yet, the response is relatively low, and minute [...] Read more.
Second harmonic generation (SHG) is forbidden from most bulk metals because metals are characterized by centrosymmetric symmetry. Adsorption or desorption of molecules at the metal interface can break the symmetry and lead to SHG responses. Yet, the response is relatively low, and minute changes occurring at the interface, especially at solid/liquid interfaces, like in battery electrodes are difficult to assess. Herein, we use a plasmonic structure milled in a gold electrode to increase the overall SHG signal from the interface and gain information about small changes occurring at the interface. Using a specific homebuilt cell, we monitor changes at the liquid/electrode interface. Specifically, traces of water in dimethoxyethane (DME) have been detected following changes in the SHG responses from the plasmonic structures. We propose that by plasmonic structures this technique can be used for assessing minute changes occurring at solid/liquid interfaces such as battery electrodes. Full article
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Open AccessCommunication
Facile Synthesis of Triphenylamine Based Hyperbranched Polymer for Organic Field Effect Transistors
Nanomaterials 2019, 9(12), 1787; https://doi.org/10.3390/nano9121787 - 16 Dec 2019
Cited by 2 | Viewed by 866
Abstract
In this study, we reported the synthesis and characterization of a novel hyperbranched polymer (HBPs) tris[(4-phenyl)amino-alt-4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b’]dithiophene] (PTPABDT) composed of benzo[1,2-b:4,5-b’]dithiophene (BDT) and triphenyleamine (TPA) constituent subunits by A3 + B2 type Stille’s reaction. An estimated optical band gap [...] Read more.
In this study, we reported the synthesis and characterization of a novel hyperbranched polymer (HBPs) tris[(4-phenyl)amino-alt-4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b’]dithiophene] (PTPABDT) composed of benzo[1,2-b:4,5-b’]dithiophene (BDT) and triphenyleamine (TPA) constituent subunits by A3 + B2 type Stille’s reaction. An estimated optical band gap of 1.69 eV with HOMO and LUMO levels of −5.29 eV and −3.60 eV, respectively, as well as a high thermal stability up to 398 °C were characterized for the synthesized polymer. PTPABDT fabricated as an encapsulated top gate/bottom contact (TGBC), organic field effect transistors (OFET) exhibited a p-type behavior with maximum field-effect mobility (µmax) and an on/off ratio of 1.22 × 10−3 cm2 V−1 s−1 and 7.47 × 102, respectively. Full article
(This article belongs to the Section Nanocomposite Materials)
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Open AccessArticle
Adsorptive and Reductive Removal of Chlorophenol from Wastewater by Biomass-Derived Mesoporous Carbon-Supported Sulfide Nanoscale Zerovalent Iron
Nanomaterials 2019, 9(12), 1786; https://doi.org/10.3390/nano9121786 - 16 Dec 2019
Cited by 4 | Viewed by 633
Abstract
Chlorinated compounds in a water environment pose serious threats to humanity. A nanoscale zerovalent iron (nZVI) has desirable properties for water dichlorination, but its reactivity is still limited by agglomeration and oxidation. In this study, the mesoporous carbon (MC) derived from biomass waste [...] Read more.
Chlorinated compounds in a water environment pose serious threats to humanity. A nanoscale zerovalent iron (nZVI) has desirable properties for water dichlorination, but its reactivity is still limited by agglomeration and oxidation. In this study, the mesoporous carbon (MC) derived from biomass waste was prepared for immobilizing nZVI, and the [email protected] was further modified by sulfur ([email protected]) to relieve surface oxidation. The synergistic effect between nZVI and surface modification, the reaction conditions and the removal mechanism were investigated systematically. The characterization results showed nZVI was successfully loaded on the surface of MC, and the aggregation of nZVI was prevented. Moreover, sulfidation modification resulted in the formation of FeS on the surface of nZVI, which effectively alleviated surface oxidation of nZVI and promoted the electron transfer. Batch experiments demonstrated [email protected] had greatly enhanced reactivity towards 2,4,6-trichlorphenol (TCP) as compared to MC and nZVI, and the removal rate could reach 100%, which was mainly attributed to the significant synergistic effect of MC immobilization and sulfidation modification. Furthermore, the TCP removal process was well described by a Langmuir adsorption model and pseudo-second-order model. The possible mechanism for enhanced removal of TCP is the fast adsorption onto [email protected] and effective reduction by S-nZVI. Therefore, with excellent reducing activity and antioxidation, [email protected] has the potential as a pollutant treatment. Full article
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Open AccessArticle
High-Efficiency Production of Large-Size Few-Layer Graphene Platelets via Pulsed Discharge of Graphite Strips
Nanomaterials 2019, 9(12), 1785; https://doi.org/10.3390/nano9121785 - 16 Dec 2019
Cited by 1 | Viewed by 720
Abstract
The synthesis of large-size graphene materials is still a central focus of research into additional potential applications in various areas. In this study, large-size graphene platelets were successfully produced by pulsed discharge of loose graphite strips with a dimension of 2 mm × [...] Read more.
The synthesis of large-size graphene materials is still a central focus of research into additional potential applications in various areas. In this study, large-size graphene platelets were successfully produced by pulsed discharge of loose graphite strips with a dimension of 2 mm × 0.5 mm × 80 mm in distilled water. The graphite strips were made by pressing and cutting well-oriented expanded graphite paper. The recovered samples were characterized by various techniques, including TEM, SEM, optical microscopy (OM), atomic force microscopy (AFM), XRD and Raman spectroscopy. Highly crystalline graphene platelets with a lateral dimension of 100–200 μm were identified. The high yield of recovered graphene platelets is in a range of 90–95%. The results also indicate that increasing charging voltage improves the yield of graphene platelets and decreases the number of graphitic layers in produced graphene platelets. The formation mechanism of graphene platelets was discussed. This study provides a one-step cost-effective route to prepare highly crystalline graphene platelets with a sub-millimeter lateral size. Full article
(This article belongs to the Special Issue 2D Materials and Their Heterostructures and Superlattices)
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Open AccessArticle
The Flexible Lubrication Performance of Graphene Used in Diamond Interface as a Solid Lubricant: First-Principles Calculations
Nanomaterials 2019, 9(12), 1784; https://doi.org/10.3390/nano9121784 - 16 Dec 2019
Viewed by 634
Abstract
The interfacial friction performances of graphene covered and hydrogen-terminated diamond surfaces were investigated comparatively by first-principles calculations within density functional theory (DFT). Both systems exhibit similar excellent lubricating effects under small load, but the graphene covered interface presents small friction than that of [...] Read more.
The interfacial friction performances of graphene covered and hydrogen-terminated diamond surfaces were investigated comparatively by first-principles calculations within density functional theory (DFT). Both systems exhibit similar excellent lubricating effects under small load, but the graphene covered interface presents small friction than that of hydrogenated system for the larger load. The calculated interfacial friction between two sheets of graphene covered diamond surface increases slowly than that of hydrogenated system in a wide range of pressure scale, and the friction difference between the two systems increases with increasing external pressure, indicating that graphene has flexible lubricating properties with high load-carrying capacity. This behavior can be attributed to the large interlayer space and a more uniform interlayer charge distribution of graphene covered diamond interface. Our investigations suggest that graphene is a promising candidate as solid lubricate used in diamond film, and are helpful for the understanding of interfacial friction properties of diamond film. Full article
(This article belongs to the Section Nanocomposite Materials)
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Open AccessArticle
Ferroelectric Diode Effect with Temperature Stability of Double Perovskite Bi2NiMnO6 Thin Films
Nanomaterials 2019, 9(12), 1783; https://doi.org/10.3390/nano9121783 - 15 Dec 2019
Cited by 1 | Viewed by 743
Abstract
Double perovskite Bi2NiMnO6 (BNMO) thin films grown on p-Si (100) substrates with LaNiO3 (LNO) buffer layers were fabricated using chemical solution deposition. The crystal structure, surface topography, surface chemical state, ferroelectric, and current-voltage characteristics of BNMO thin films were [...] Read more.
Double perovskite Bi2NiMnO6 (BNMO) thin films grown on p-Si (100) substrates with LaNiO3 (LNO) buffer layers were fabricated using chemical solution deposition. The crystal structure, surface topography, surface chemical state, ferroelectric, and current-voltage characteristics of BNMO thin films were investigated. The results show that the nanocrystalline BNMO thin films on p-Si substrates without and with LNO buffer layer are monoclinic phase, which have antiferroelectric-like properties. The composition and chemical state of BNMO thin films were characterized by X-ray photoelectron spectroscopy. In the whole electrical property testing process, when the BNMO/p-Si heterojunction changed into a BNMO/LNO/p-Si heterojunction, the diode behavior of a single diode changing into two tail to tail diodes was observed. The conduction mechanism and temperature stability were also discussed. Full article
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Open AccessArticle
Fabrication and Characterization of Electrospun Aligned Porous PAN/Graphene Composite Nanofibers
Nanomaterials 2019, 9(12), 1782; https://doi.org/10.3390/nano9121782 - 15 Dec 2019
Cited by 4 | Viewed by 771
Abstract
A modified parallel electrode method (MPEM), conducted by placing a positively charged ring between the needle and the paralleled electrode collector, was presented to fabricate aligned polyacrylonitrile/graphene (PAN/Gr) composite nanofibers (CNFs) with nanopores in an electrospinning progress. Two kinds of solvents and one [...] Read more.
A modified parallel electrode method (MPEM), conducted by placing a positively charged ring between the needle and the paralleled electrode collector, was presented to fabricate aligned polyacrylonitrile/graphene (PAN/Gr) composite nanofibers (CNFs) with nanopores in an electrospinning progress. Two kinds of solvents and one kind of nanoparticle were used to generate pores on composite nanofibers. The spinning parameters, such as the concentration of solute and solvent, spinning voltage and spinning distance were discussed, and the optimal parameters were determined. Characterizations of the aligned CNFs with nanopores were investigated by scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), high-resistance meter, and other methods. The results showed that graphene (Gr) nanoparticles were successfully introduced into aligned CNFs with nanopores and almost aligned along the axis of the CNFs. The MPEM method could make hydrophobic materials more hydrophobic, and improve the alignment degree and conductive properties of electrospun-aligned CNFs with nanopores. Moreover, the carbonized CNFs with nanopores, used as an electrode material, had a smaller charge-transfer resistance, suggesting potential application in electrochemical areas and electron devices. Full article
(This article belongs to the Section Nanocomposite Materials)
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Open AccessArticle
Nanostructured Cu2O Synthesized via Bipolar Electrochemistry
Nanomaterials 2019, 9(12), 1781; https://doi.org/10.3390/nano9121781 - 15 Dec 2019
Viewed by 1081
Abstract
Cuprous oxide (Cu2O) was synthesized for the first time via an open bipolar electrochemistry (BPE) approach and characterized in parallel with the commercially available material. As compared to the reference, Cu2O formed through a BPE reaction demonstrated a decrease [...] Read more.
Cuprous oxide (Cu2O) was synthesized for the first time via an open bipolar electrochemistry (BPE) approach and characterized in parallel with the commercially available material. As compared to the reference, Cu2O formed through a BPE reaction demonstrated a decrease in particle size; an increase in photocurrent; more efficient light scavenging; and structure-correlated changes in the flat band potential and charge carrier concentration. More importantly, as-synthesized oxides were all phase-pure, defect-free, and had an average crystallite size of 20 nm. Ultimately, this study demonstrates the impact of reaction conditions (e.g., applied potential, reaction time) on structure, morphology, surface chemistry, and photo-electrochemical activity of semiconducting oxides, and at the same time, the ability to maintain a green synthetic protocol and potentially create a scalable product. In the proposed BPE synthesis, we introduced a common food supplement (potassium gluconate) as a reducing and complexing agent, and as an electrolyte, allowing us to replace the more harmful reactants that are conventionally used in Cu2O production. In addition, in the BPE process very corrosive reactants, such as hydroxides and metal precursors (required for synthesis of oxides), are generated in situ in stoichiometric quantity, providing an alternative methodology to generate various nanostructured materials in high yields under mild conditions. Full article
(This article belongs to the Section Synthesis, Interfaces and Nanostructures)
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Open AccessArticle
Vibration Analysis of Fluid Conveying Carbon Nanotubes Based on Nonlocal Timoshenko Beam Theory by Spectral Element Method
Nanomaterials 2019, 9(12), 1780; https://doi.org/10.3390/nano9121780 - 14 Dec 2019
Cited by 1 | Viewed by 735
Abstract
In this work, we applied the spectral element method (SEM) to analyze the dynamic characteristics of fluid conveying single-walled carbon nanotubes (SWCNTs). First, the dynamic equations for fluid conveying SWCNTs were deduced based on the nonlocal Timoshenko beam theory. Then, the spectral element [...] Read more.
In this work, we applied the spectral element method (SEM) to analyze the dynamic characteristics of fluid conveying single-walled carbon nanotubes (SWCNTs). First, the dynamic equations for fluid conveying SWCNTs were deduced based on the nonlocal Timoshenko beam theory. Then, the spectral element formulation was established for a free/forced vibration analysis of fluid conveying SWCNTs by introducing discrete Fourier transform. Furthermore, the proposed method was validated using several comparison examples. Finally, the natural frequencies and dynamic responses of a simply-supported fluid conveying SWCNTs were calculated by the SEM, considering different internal fluid velocities and small-scale parameters (SSPs). The effects of fluid velocity and SSPs on the dynamic characteristics of SWCNTs conveying fluid were revealed by the numerical results. Compared with other methods, the SEM shows high accuracy and efficiency. Full article
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Open AccessArticle
Shape-Controlled Synthesis of Copper Indium Sulfide Nanostructures: Flowers, Platelets and Spheres
Nanomaterials 2019, 9(12), 1779; https://doi.org/10.3390/nano9121779 - 14 Dec 2019
Cited by 1 | Viewed by 796
Abstract
Colloidal semiconductor nanostructures have been widely investigated for several applications, which rely not only on their size but also on shape control. CuInS2 (often abbreviated as CIS) nanostructures have been considered as candidates for solar energy conversion. In this work, three-dimensional (3D) [...] Read more.
Colloidal semiconductor nanostructures have been widely investigated for several applications, which rely not only on their size but also on shape control. CuInS2 (often abbreviated as CIS) nanostructures have been considered as candidates for solar energy conversion. In this work, three-dimensional (3D) colloidal CIS nanoflowers and nanospheres and two-dimensional (2D) nanoplatelets were selectively synthesized by changing the amount of a sulfur precursor (tert-dodecanethiol) serving both as a sulfur source and as a co-ligand. Monodisperse CIS nanoflowers (~15 nm) were formed via the aggregation of smaller CIS nanoparticles when the amount of tert-dodecanethiol used in reaction was low enough, which changed towards the formation of larger (70 nm) CIS nanospheres when it significantly increased. Both of these structures crystallized in a chalcopyrite CIS phase. Using an intermediate amount of tert-dodecanethiol, 2D nanoplatelets were obtained, 90 nm in length, 25 nm in width and the thickness of a few nanometers along the a-axis of the wurtzite CIS phase. Based on a series of experiments which employed mixtures of tert-dodecanethiol and 1-dodecanethiol, a ligand-controlled mechanism is proposed to explain the manifold range of the resulting shapes and crystal phases of CIS nanostructures. Full article
(This article belongs to the Section Synthesis, Interfaces and Nanostructures)
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Open AccessArticle
Inapparent Strengthening Effect of Twin Interface in Cu/Pd Multilayered Films with a Large Lattice Mismatch
Nanomaterials 2019, 9(12), 1778; https://doi.org/10.3390/nano9121778 - 13 Dec 2019
Cited by 3 | Viewed by 661
Abstract
It has been found that there are two kinds of interfaces in a Cu/Pd multilayered film, namely, cube-on-cube and twin. However, the effects of the interfacial structure and modulation period on the mechanical properties of a Cu/Pd multilayered film remain unclear. In this [...] Read more.
It has been found that there are two kinds of interfaces in a Cu/Pd multilayered film, namely, cube-on-cube and twin. However, the effects of the interfacial structure and modulation period on the mechanical properties of a Cu/Pd multilayered film remain unclear. In this work, molecular dynamics simulations of Cu/Pd multilayered film with different interfaces and modulation periods under in-plane tension are performed to investigate the effects of the interfacial structure and modulation period. The interface misfit dislocation net exhibits a periodic triangular distribution, while the residual internal stress can be released through the bending of dislocation lines. With the increase of the modulation period, the maximum stress shows an upward trend, while the flow stress declines. It was found that the maximum stress and flow stress of the sample with a cube-on-cube interface is higher than that of the sample with a twin interface, which is different from the traditional cognition. This unusual phenomenon is mainly attributed to the discontinuity and unevenness of the twin boundaries caused by the extremely severe lattice mismatch. Full article
(This article belongs to the Section Synthesis, Interfaces and Nanostructures)
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Open AccessArticle
Enhanced Antifungal Activities of Eugenol-Entrapped Casein Nanoparticles against Anthracnose in Postharvest Fruits
Nanomaterials 2019, 9(12), 1777; https://doi.org/10.3390/nano9121777 - 13 Dec 2019
Cited by 2 | Viewed by 757
Abstract
This study aims to improve the antifungal effects of eugenol through low-energy self-assembly fabrication and optimization of eugenol-casein nanoparticles (EC-NPs). Optimized EC-NPs (eugenol/casein ratio of 1:5) were obtained with a mean size of 307.4 ± 2.5 nm and entrapment efficiency of 86.3% ± [...] Read more.
This study aims to improve the antifungal effects of eugenol through low-energy self-assembly fabrication and optimization of eugenol-casein nanoparticles (EC-NPs). Optimized EC-NPs (eugenol/casein ratio of 1:5) were obtained with a mean size of 307.4 ± 2.5 nm and entrapment efficiency of 86.3% ± 0.2%, and showed high stability under incubated at 20 and 37 °C for 48 h. EC-NPs exhibited satisfactory sustained-release effect at 20 °C or 37 °C, with remaining eugenols amounts of 79.51% and 53.41% after 72 h incubation, respectively, which were significantly higher than that of native eugenol (only 26.40% and 19.82% after the first 12 h). EC-NPs exhibited a greater antifungal activity (>95.7%) against spore germination of fungus that was greater than that of native eugenol, showed 100% inhibition of the anthracnose incidence in postharvest pear after 7 d. EC-NPs is potential as an environmental-friendly preservatives in the food industry. Full article
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Open AccessArticle
Nitriding an Oxygen-Doped Nanocarbonaceous Sorbent Synthesized via Solution Plasma Process for Improving CO2 Adsorption Capacity
Nanomaterials 2019, 9(12), 1776; https://doi.org/10.3390/nano9121776 - 13 Dec 2019
Viewed by 711
Abstract
The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800 °C for 2 h to yield [...] Read more.
The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800 °C for 2 h to yield NCn and NOCn, respectively, for carbon dioxide (CO2) adsorption. The NOCn exhibited the highest specific surface area (~570 m2 g−1) and highest CO2 adsorption capacity (1.63 mmol g−1 at 25 °C) among the synthesized samples. The primary nitrogen species on the surface of NOCn were pyridinic-N and pyrrolic-N. The synergistic effect of microporosity and nitrogen functionality on the NOCn surface played an essential role in CO2 adsorption enhancement. From the thermodynamic viewpoint, the CO2 adsorption on NOCn was physisorption, exothermic, and spontaneous. The NOCn showed a more negative enthalpy of adsorption, indicating its stronger interaction for CO2 on the surface, and hence, the higher adsorption capacity. The CO2 adsorption on NOCn over the whole pressure range at 25–55 °C best fitted the Toth model, suggesting monolayer adsorption on the heterogeneous surface. In addition, NOCn expressed a higher selective CO2 adsorption than Cn and so was a good candidate for multicycle adsorption. Full article
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Open AccessReview
Limitations of Recent Studies Dealing with the Antibacterial Properties of Silver Nanoparticles: Fact and Opinion
Nanomaterials 2019, 9(12), 1775; https://doi.org/10.3390/nano9121775 - 13 Dec 2019
Cited by 9 | Viewed by 930
Abstract
Due to the constant increase in the number of infectious diseases and the concomitant lack of treatment available, metallic nanoparticles (e.g., silver nanoparticles) have been of particular interest in the last decades. Indeed, several studies suggest that silver nanoparticles have valuable antimicrobial activities, [...] Read more.
Due to the constant increase in the number of infectious diseases and the concomitant lack of treatment available, metallic nanoparticles (e.g., silver nanoparticles) have been of particular interest in the last decades. Indeed, several studies suggest that silver nanoparticles have valuable antimicrobial activities, especially against bacteria, which may lead us to think that these nanoparticles may one day be an attractive therapeutic option for the treatment of bacterial infections. Unfortunately, when we look a little closer to these studies, we can see a very great heterogeneity (e.g., in the study design, in the synthetic process of nanoparticles, in the methods that explore the antibacterial properties of nanoparticles and in the bacteria chosen) making cross-interpretation between these studies impossible, and significantly limiting the interest of silver nanoparticles as promising antibacterial agents. We have selected forty-nine international publications published since 2015, and propose to discuss, not the results obtained, but precisely the different methodologies developed in these publications. Through this discussion, we highlighted the aspects to improve, or at least to homogenize, in order to definitively establish the interest of silver nanoparticles as valuable antibacterial agents. Full article
(This article belongs to the Special Issue Antibacterial Activity of Nanoparticles)
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Open AccessArticle
Facile Synthesis of Triangular and Hexagonal Anionic Gold Nanoparticles and Evaluation of Their Cytotoxicity
Nanomaterials 2019, 9(12), 1774; https://doi.org/10.3390/nano9121774 - 12 Dec 2019
Cited by 3 | Viewed by 799
Abstract
Comprehension of the shape-dependent properties of gold nanoparticles (AuNPs) could benefit the advancements in cellular uptake efficiency. Spherical AuNPs have generally been used for drug delivery, and recent research has indicated that the cellular uptake of triangular AuNPs was higher than that of [...] Read more.
Comprehension of the shape-dependent properties of gold nanoparticles (AuNPs) could benefit the advancements in cellular uptake efficiency. Spherical AuNPs have generally been used for drug delivery, and recent research has indicated that the cellular uptake of triangular AuNPs was higher than that of spherical ones. Previous reports have also revealed that chemically synthesized AuNPs were cytotoxic. Therefore, we have developed a facile, cost-effective, and environmentally friendly method for synthesizing triangular and hexagonal anionic AuNPs. The zeta potential of the synthesized AuNPs was negative, which indicated that their surface could be easily functionalized with positively charged molecules to upload drugs or biomolecules. Transmission electron microscopy (TEM) images illustrated that the largest particle size of the synthesized quasi-hexagonal AuNPs was 61 nm. The TEM images also illustrated that two types of equilateral-triangular AuNPs were synthesized: One featured sharp and the other rounded corners. The sides of the smallest and largest triangular AuNPs were 23 and 178 nm, respectively. Energy-dispersive X-ray spectra of the green-synthesized AuNPs indicated that they consisted entirely of elemental Au. The cytotoxicity of the green-synthesized AuNPs was evaluated using 3T3-L1 adipocytes. Using cell viability data, we determined that the green-synthesized AuNPs did not exhibit any cytotoxic effects on 3T3-L1 adipocytes. Full article
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Open AccessArticle
Shape-Stabilized Phase Change Materials for Solar Energy Storage: MgO and Mg(OH)2 Mixed with Polyethylene Glycol
Nanomaterials 2019, 9(12), 1773; https://doi.org/10.3390/nano9121773 - 12 Dec 2019
Cited by 2 | Viewed by 958
Abstract
Heat energy storage systems were fabricated with the impregnation method using MgO and Mg(OH)2 as supporting materials and polyethylene glycol (PEG-6000) as the functional phase. MgO and Mg(OH)2 were synthesized from the salt Mg(NO3)·6H2O by performing hydrothermal [...] Read more.
Heat energy storage systems were fabricated with the impregnation method using MgO and Mg(OH)2 as supporting materials and polyethylene glycol (PEG-6000) as the functional phase. MgO and Mg(OH)2 were synthesized from the salt Mg(NO3)·6H2O by performing hydrothermal reactions with various precipitating agents. The precipitating agents were NaOH, KOH, NH3, NH3 with pamoic acid (PA), or (NH4)2CO3. The result shows that the selection of the precipitating agent has a significant impact on the crystallite structure, size, and shape of the final products. Of the precipitating agents tested, only NaOH and NH3 with PA produce single-phase Mg(OH)2 as the as-synthesized product. Pore size distribution analyses revealed that the surfaces of the as-synthesized MgO have a slit-like pore structure with a broad-type pore size distribution, whereas the as-synthesized Mg(OH)2 has a mesoporous structure with a narrow pore size distribution. This structure enhances the latent heat of the phase change material (PCM) as well as super cooling mitigation. The PEG/Mg(OH)2 PCM also exhibits reproducible behavior over a large number of thermal cycles. Both MgO and Mg(OH)2 matrices prevent the leakage of liquid PEG during the phase transition in phase change materials (PCMs). However, MgO/PEG has a low impregnation ratio and efficiency, with a low thermal storage capability. This is due to the large pore diameter, which does not allow MgO to retain a larger amount of PEG. The latent heat values of PEG-1000/PEG-6000 blends with MgO and Mg(OH)2 were also determined with a view to extending the application of the PCMs to energy storage over wider temperature ranges. Full article
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Open AccessArticle
Ionic Liquid-Modulated Synthesis of Porous Worm-Like Gold with Strong SERS Response and Superior Catalytic Activities
Nanomaterials 2019, 9(12), 1772; https://doi.org/10.3390/nano9121772 - 12 Dec 2019
Cited by 1 | Viewed by 695
Abstract
Porous gold with well-defined shape and size have aroused extensive research enthusiasm due to their prominent properties in various applications. However, it is still a great challenge to explore a simple, green, and low-cost route to fabricate porous gold with a “clean” surface. [...] Read more.
Porous gold with well-defined shape and size have aroused extensive research enthusiasm due to their prominent properties in various applications. However, it is still a great challenge to explore a simple, green, and low-cost route to fabricate porous gold with a “clean” surface. In this work, porous worm-like Au has been easily synthesized in a one-step procedure from aqueous solution at room temperature under the action of ionic liquid tetrapropylammonium glycine ([N3333][Gly]). It is shown that the as-prepared porous worm-like Au has the length from 0.3 to 0.6 μm and the width of approximately 100–150 nm, and it is composed of lots of small nanoparticles about 6–12 nm in diameter. With rhodamine 6G (R6G) as a probe molecule, porous worm-like Au displays remarkable surface enhanced Raman scattering (SERS) sensitivity (detection limit is lower than 10−13 M), and extremely high reproducibility (average relative standard deviations is less than 2%). At the same time, owing to significantly high specific surface area, various pore sizes and plenty of crystal defects, porous worm-like Au also exhibits excellent catalytic performance in the reduction of nitroaromatics, such as p-nitrophenol and p-nitroaniline, which can be completely converted within only 100 s and 150 s, respectively. It is expected that the as-prepared porous worm-like Au with porous and self-supported structures will also present the encouraging advances in electrocatalysis, sensing, and many others. Full article
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Open AccessArticle
Self-Filtering Monochromatic Infrared Detectors Based on Bi2Se3 (Sb2Te3)/Silicon Heterojunctions
Nanomaterials 2019, 9(12), 1771; https://doi.org/10.3390/nano9121771 - 12 Dec 2019
Viewed by 726
Abstract
This paper focuses on the photoelectric properties of heterostructures formed by surface-modified Si (111) and hexagonal, quintuple-layered selenides (Bi2Se3 and Sb2Te3). It was shown that H-passivated Si (111) can form robust Schottky junctions with either Bi [...] Read more.
This paper focuses on the photoelectric properties of heterostructures formed by surface-modified Si (111) and hexagonal, quintuple-layered selenides (Bi2Se3 and Sb2Te3). It was shown that H-passivated Si (111) can form robust Schottky junctions with either Bi2Se3 or Sb2Te3. When back illuminated (i.e., light incident towards the Si side of the junction), both the Bi2Se3/Si and Sb2Te3/Si junctions exhibited significant photovoltaic response at 1030 nm, which is right within the near-infrared (NIR) light wavelength range. A maximum external quantum efficiency of 14.7% with a detection response time of 2 ms for Bi2Se3/Si junction, and of 15.5% with a 0.8 ms response time for the Sb2Te3/Si junction, were achieved. Therefore, utilizing Si constituents as high-pass filters, the Bi2Se3 (Sb2Te3)/Si heterojunctions can serve as monochromatic NIR photodetectors. Full article
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Open AccessArticle
N-Doped Modified Graphene/Fe2O3 Nanocomposites as High-Performance Anode Material for Sodium Ion Storage
Nanomaterials 2019, 9(12), 1770; https://doi.org/10.3390/nano9121770 - 12 Dec 2019
Cited by 1 | Viewed by 799
Abstract
Sodium-ion storage devices have received widespread attention because of their abundant sodium resources, low cost and high energy density, which verges on lithium-ion storage devices. Electrochemical redox reactions of metal oxides offer a new approach to construct high-capacity anodes for sodium-ion storage devices. [...] Read more.
Sodium-ion storage devices have received widespread attention because of their abundant sodium resources, low cost and high energy density, which verges on lithium-ion storage devices. Electrochemical redox reactions of metal oxides offer a new approach to construct high-capacity anodes for sodium-ion storage devices. However, the poor rate performance, low Coulombic efficiency, and undesirable cycle stability of the redox conversion anodes remain a huge challenge for the practical application of sodium ion energy storage devices due to sluggish kinetics and irreversible structural change of most conversion anodes during cycling. Herein, a nitrogen-doping graphene/Fe2O3 (N-GF-300) composite material was successfully prepared as a sodium-ion storage anode for sodium ion batteries and sodium ion supercapacitors through a water bath and an annealing process, where Fe2O3 nanoparticles with a homogenous size of about 30 nm were uniformly anchored on the graphene nanosheets. The nitrogen-doping graphene structure enhanced the connection between Fe2O3 nanoparticles with graphene nanosheets to improve electrical conductivity and buffer the volume change of the material for high capacity and stable cycle performance. The N-GF-300 anode material delivered a high reversible discharge capacity of 638 mAh g−1 at a current density of 0.1 A g−1 and retained 428.3 mAh g−1 at 0.5 A g−1 after 100 cycles, indicating a strong cyclability of the SIBs. The asymmetrical N-GF-300//graphene SIC exhibited a high energy density and power density with 58 Wh kg−1 at 1365 W kg−1 in organic solution. The experimental results from this work clearly illustrate that the nitrogen-doping graphene/Fe2O3 composite material N-GF-300 is a potential feasibility for sodium-ion storage devices, which further reveals that the nitrogen doping approach is an effective technique for modifying carbon matrix composites for high reaction kinetics during cycles in sodium-ion storage devices and even other electrochemical storage devices. Full article
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Open AccessArticle
Comparison of Different Approaches to Surface Functionalization of Biodegradable Polycaprolactone Scaffolds
Nanomaterials 2019, 9(12), 1769; https://doi.org/10.3390/nano9121769 - 12 Dec 2019
Cited by 9 | Viewed by 1043
Abstract
Due to their good mechanical stability compared to gelatin, collagen or polyethylene glycol nanofibers and slow degradation rate, biodegradable poly-ε-caprolactone (PCL) nanofibers are promising material as scaffolds for bone and soft-tissue engineering. Here, PCL nanofibers were prepared by the electrospinning method and then [...] Read more.
Due to their good mechanical stability compared to gelatin, collagen or polyethylene glycol nanofibers and slow degradation rate, biodegradable poly-ε-caprolactone (PCL) nanofibers are promising material as scaffolds for bone and soft-tissue engineering. Here, PCL nanofibers were prepared by the electrospinning method and then subjected to surface functionalization aimed at improving their biocompatibility and bioactivity. For surface modification, two approaches were used: (i) COOH-containing polymer was deposited on the PCL surface using atmospheric pressure plasma copolymerization of CO2 and C2H4, and (ii) PCL nanofibers were coated with multifunctional bioactive nanostructured TiCaPCON film by magnetron sputtering of TiC–CaO–Ti3POx target. To evaluate bone regeneration ability in vitro, the surface-modified PCL nanofibers were immersed in simulated body fluid (SBF, 1×) for 21 days. The results obtained indicate different osteoblastic and epithelial cell response depending on the modification method. The TiCaPCON-coated PCL nanofibers exhibited enhanced adhesion and proliferation of MC3T3-E1 cells, promoted the formation of Ca-based mineralized layer in SBF and, therefore, can be considered as promising material for bone tissue regeneration. The PCL–COOH nanofibers demonstrated improved adhesion and proliferation of IAR-2 cells, which shows their high potential for skin reparation and wound dressing. Full article
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Open AccessArticle
Design and Simulation of a Multi-Sheet Beam Terahertz Radiation Source Based on Carbon-Nanotube Cold Cathode
Nanomaterials 2019, 9(12), 1768; https://doi.org/10.3390/nano9121768 - 12 Dec 2019
Cited by 2 | Viewed by 967
Abstract
Carbon nanotube (CNT) cold cathodes are proving to be compelling candidates for miniaturized terahertz (THz) vacuum electronic devices (VEDs) owning to their superior field-emission (FE) characteristics. Here, we report on the development of a multi-sheet beam CNT cold cathode electron optical system with [...] Read more.
Carbon nanotube (CNT) cold cathodes are proving to be compelling candidates for miniaturized terahertz (THz) vacuum electronic devices (VEDs) owning to their superior field-emission (FE) characteristics. Here, we report on the development of a multi-sheet beam CNT cold cathode electron optical system with concurrently high beam current and high current density. The microscopic FE characteristics of the CNT film emitter is captured through the development of an empirically derived macroscopic simulation model which is used to provide representative emission performance. Through parametrically optimized macroscale simulations, a five-sheet-beam triode electron gun has been designed, and has been shown to emit up to 95 mA at 3.2 kV. Through careful engineering of the electron gun geometric parameters, a low-voltage compact THz radiation source operating in high-order TM 5 , 1 mode is investigated to improve output power and suppress mode competition. Particle in cell (PIC) simulations show the average output power is 33 W at 0.1 THz, and the beam–wave interaction efficiency is approximately 10%. Full article
(This article belongs to the Special Issue Electronics, Electromagnetism and Applications of Nanomaterials)
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