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Nanomaterials
Volume 9
Issue 5
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Nanomaterials, Volume 9, Issue 5 (May 2019) – 148 articles

Cover Story (view full-size image): The self-assembly of block copolymers in aqueous solution is an important field in modern polymer science that has been extended to double hydrophilic block copolymers (DHBC) recently. We report self-assembly of a DHBC by utilizing a linear-brush polymer, namely poly(N-vinylpyrrolidone)-b-poly(oligo(ethylene glycol) methyl ether methacrylate). Moreover, non-covalent crosslinking is performed with tannic acid, which improves self-assembly and stabilizes the aggregates. The presence of aggregates is studied via cryogenic scanning electron microscopy, dynamic light scattering and analytical ultracentrifugation before and after crosslinking, clearly revealing polymer assemblies. In summary, completely hydrophilic self-assembled structures are formed in solution from fully biocompatible entities. View this paper.
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16 pages, 2306 KiB  
Article
Enzymatic Formation of Polyaniline, Polypyrrole, and Polythiophene Nanoparticles with Embedded Glucose Oxidase
by Natalija German, Anton Popov, Almira Ramanaviciene and Arunas Ramanavicius
Nanomaterials 2019, 9(5), 806; https://doi.org/10.3390/nano9050806 - 27 May 2019
Cited by 35 | Viewed by 3777
Abstract
Polyaniline (PANI), polypyrrole (Ppy), and polythiophene (PTh) composite nanoparticles with embedded glucose oxidase (GOx) were formed by enzymatic polymerization of corresponding monomers (aniline, pyrrole, and thiophene). The influence of monomers concentration, the pH of solution, and the ratio of enzyme/substrate on the formation [...] Read more.
Polyaniline (PANI), polypyrrole (Ppy), and polythiophene (PTh) composite nanoparticles with embedded glucose oxidase (GOx) were formed by enzymatic polymerization of corresponding monomers (aniline, pyrrole, and thiophene). The influence of monomers concentration, the pH of solution, and the ratio of enzyme/substrate on the formation of PANI/GOx, Ppy/GOx, and PTh/GOx composite nanoparticles were spectrophotometrically investigated. The highest formation rate of PANI-, Ppy-, and PTh-based nanoparticles with embedded GOx was observed in the sodium acetate buffer solution, pH 6.0. The increase of optical absorbance at λmax = 440 nm, λmax = 460 nm, and λmax = 450 nm was exploited for the monitoring of PANI/GOx, Ppy/GOx and PTh/GOx formation, respectively. It was determined that the highest polymerization rate of PANI/GOx, Ppy/GOx, and PTh/GOx composite nanoparticles was achieved in solution containing 0.75 mg mL−1 of GOx and 0.05 mol L−1 of glucose. The influence of the enzymatic polymerization duration on the formation of PANI/GOx and Ppy/GOx composite nanoparticles was spectrophotometrically investigated. The most optimal duration for the enzymatic synthesis of PANI/GOx and Ppy/GOx composite nanoparticles was in the range of 48–96 h. It was determined that the diameter of formed PANI/GOx and Ppy/GOx composite nanoparticles depends on the duration of polymerization using dynamic light scattering technique (DLS), and it was in the range of 41–167 nm and 65–122 nm, when polymerization lasted from 16 to 120 h. Full article
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16 pages, 2408 KiB  
Article
Electrospinning of Cellulose Nanocrystal-Filled Poly (Vinyl Alcohol) Solutions: Material Property Assessment
by J. Elliott Sanders, Yousoo Han, Todd S. Rushing and Douglas J. Gardner
Nanomaterials 2019, 9(5), 805; https://doi.org/10.3390/nano9050805 - 27 May 2019
Cited by 27 | Viewed by 5117
Abstract
Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared using the electrospinning method. PVA/CNC mats were reinforced with weight concentrations of 0, 20 and 50% CNC (w/w) relative to PVA. Scanning electron microscopy was used [...] Read more.
Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared using the electrospinning method. PVA/CNC mats were reinforced with weight concentrations of 0, 20 and 50% CNC (w/w) relative to PVA. Scanning electron microscopy was used to measure the fiber diameter, which ranged from 377 to 416 nm. Thermogravimetric analysis (TGA) confirmed the presence of CNC fibers in the mat fibers which were not visible by scanning electron microscope (SEM). Mechanical testing was conducted using ASTM D 638 on each sample group at 10 mm min−1. Neat PVA and PVA/CNC mats were heat treated at 170 °C for 2h hours, and the morphological structure was maintained with some fiber diameter reduction. Mechanical property results after heat treatment showed a decrease in tensile strength, an increase in tensile stiffness and a decrease in strain to yield (%). This effect was attributable to enhanced diffusion bonding of the mat fiber intersections. The CNC fibers also increased mat stiffness, and reduced strain to yield in non-treated mats. The use of CNCs show potential for compounding into bulk polymer composites as a reinforcement filler, and also show promise for chemical crosslinking attributable to the –OH groups on both the PVA, in addition to esterification of the vinyl group, and CNC. Full article
(This article belongs to the Special Issue Nanocelluloses: Synthesis, Modification and Applications)
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12 pages, 1908 KiB  
Article
Modification of the Raman Spectra in Graphene-Based Nanofluids and Its Correlation with Thermal Properties
by María del Rocío Rodríguez-Laguna, Pedro Gómez-Romero, Clivia M. Sotomayor Torres and Emigdio Chavez-Angel
Nanomaterials 2019, 9(5), 804; https://doi.org/10.3390/nano9050804 - 26 May 2019
Cited by 17 | Viewed by 4354
Abstract
It is well known that by dispersing nanoparticles in a fluid, the thermal conductivity of the resulting nanofluid tends to increase with the concentration of nanoparticles. However, it is not clear what the mechanism behind this phenomenon is. Raman spectroscopy is a characterization [...] Read more.
It is well known that by dispersing nanoparticles in a fluid, the thermal conductivity of the resulting nanofluid tends to increase with the concentration of nanoparticles. However, it is not clear what the mechanism behind this phenomenon is. Raman spectroscopy is a characterization technique connecting the molecular and macroscopic world, and therefore, it can unravel the puzzling effect exerted by the nanomaterial on the fluid. In this work, we report on a comparative study on the thermal conductivity, vibrational spectra and viscosity of graphene nanofluids based on three different amides: N, N-dimethylacetamide (DMAc); N, N-dimethylformamide (DMF); and N-methyl-2-pyrrolidinone (NMP). A set of concentrations of highly stable surfactant-free graphene nanofluids developed in-house was prepared and characterized. A correlation between the modification of the vibrational spectra of the fluids and an increase in their thermal conductivity in the presence of graphene was confirmed. Furthermore, an explanation of the non-modification of the thermal conductivity in graphene-NMP nanofluids is given based on its structure and a peculiar arrangement of the fluid. Full article
(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)
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13 pages, 2892 KiB  
Article
The Effect of Tissue-Mimicking Phantom Compressibility on Magnetic Hyperthermia
by Katarzyna Kaczmarek, Radosław Mrówczyński, Tomasz Hornowski, Rafał Bielas and Arkadiusz Józefczak
Nanomaterials 2019, 9(5), 803; https://doi.org/10.3390/nano9050803 - 25 May 2019
Cited by 29 | Viewed by 4334
Abstract
During hyperthermia, magnetite nanoparticles placed in an AC magnetic field become a source of heat. It has been shown that in fluid suspensions, magnetic particles move freely and generate heat easily. However, in tissues of different mechanical properties, nanoparticle movement is limited and [...] Read more.
During hyperthermia, magnetite nanoparticles placed in an AC magnetic field become a source of heat. It has been shown that in fluid suspensions, magnetic particles move freely and generate heat easily. However, in tissues of different mechanical properties, nanoparticle movement is limited and leads to a small temperature rise in tissue. Therefore, it is crucial to conduct magnetic hyperthermia experiments in similar conditions to the human body. The effect of tissue-mimicking phantom compressibility on the effectiveness of magnetic hyperthermia was investigated on agar phantoms. Single and cluster nanoparticles were synthesized and used as magnetic materials. The prepared magnetic materials were characterized by transmission electron microscopy (TEM), and zeta potential measurements. Results show that tissue-mimicking phantom compressibility decreases with the concentration of agar. Moreover, the lower the compressibility, the lower the thermal effect of magnetic hyperthermia. Specific absorption rate (SAR) values also proved our assumption that tissue-mimicking phantom compressibility affects magnetic losses in the alternating magnetic field (AMF). Full article
(This article belongs to the Special Issue Functional Nanoparticles for Experimental Therapy and Clinical Trial)
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20 pages, 10687 KiB  
Article
In vivo Efficacy and Safety Evaluation of Lactosyl-β-cyclodextrin as a Therapeutic Agent for Hepatomegaly in Niemann-Pick Type C Disease
by Yuki Maeda, Keiichi Motoyama, Rena Nishiyama, Taishi Higashi, Risako Onodera, Hideaki Nakamura, Toru Takeo, Naomi Nakagata, Yusei Yamada, Yoichi Ishitsuka, Yuki Kondo, Tetsumi Irie, Takumi Era and Hidetoshi Arima
Nanomaterials 2019, 9(5), 802; https://doi.org/10.3390/nano9050802 - 25 May 2019
Cited by 13 | Viewed by 4421
Abstract
Niemann-Pick type C disease (NPC) is a fatal, autosomal recessive disorder, which causes excessive accumulation of free cholesterol in endolysosomes, resulting in progressive hepatomegaly and neurodegeneration. Currently, 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) is used at a high dose for the treatment of NPC, risking lung toxicity [...] Read more.
Niemann-Pick type C disease (NPC) is a fatal, autosomal recessive disorder, which causes excessive accumulation of free cholesterol in endolysosomes, resulting in progressive hepatomegaly and neurodegeneration. Currently, 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) is used at a high dose for the treatment of NPC, risking lung toxicity and hearing loss during treatment. One method to reduce the required dose of HP-β-CyD for the treatment of hepatomegaly is to actively deliver β-cyclodextrin (β-CyD) to hepatocytes. Previously, we synthesized lactosyl-β-CyD (Lac-β-CyD) and demonstrated that it lowers cholesterol in NPC model liver cells. In the present study, we studied the efficacy and safety of Lac-β-CyD treatment of hepatomegaly in Npc1−/− mice. After subcutaneous administration, Lac-β-CyD accumulated in the liver and reduced hepatomegaly with greater efficacy than HP-β-CyD. In addition, subcutaneous administration of a very high dose of Lac-β-CyD was less toxic to the lungs than HP-β-CyD. Notably, the accumulation of intracellular free cholesterol in endolysosomes of NPC-like liver cells was significantly lower after administration of Lac-β-CyD than after treatment with HP-β-CyD. In conclusion, these results suggest that Lac-β-CyD is a candidate for the effective treatment of hepatomegaly in NPC. Full article
(This article belongs to the Special Issue Nanoconstructs Based on Cyclodextrins)
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11 pages, 1507 KiB  
Article
Gaseous Products Evolution Analyses for Catalytic Decomposition of AP by Graphene-Based Additives
by Shuwen Chen, Ting An, Yi Gao, Jie-Yao Lyu, De-Yun Tang, Xue-Xue Zhang, Fengqi Zhao and Qi-Long Yan
Nanomaterials 2019, 9(5), 801; https://doi.org/10.3390/nano9050801 - 24 May 2019
Cited by 26 | Viewed by 4194
Abstract
A quantitative evaluation method has been developed to study the effects of nanoadditives on thermal decomposition mechanisms of energetic compounds using the conventional thermogravimetry coupled with mass spectrometry (TG/MS) technique. The decomposition of ammonium perchlorate (AP) under the effect of several energetic catalysts [...] Read more.
A quantitative evaluation method has been developed to study the effects of nanoadditives on thermal decomposition mechanisms of energetic compounds using the conventional thermogravimetry coupled with mass spectrometry (TG/MS) technique. The decomposition of ammonium perchlorate (AP) under the effect of several energetic catalysts has been investigated as a demonstration. In particular, these catalysts are transition metal (Cu2+, Co2+ and Ni2+) complexes of triaminoguanidine (TAG), using graphene oxide (GO) as dopant. They have been well-compared in terms of their catalytic effects on the concentration of the released gaseous products of AP. These detailed quantitative analyses of the gaseous products of AP provide a proof that the proton transfer between ∙O and O2 determines the catalytic decomposition pathways, which largely depend on the type of reactive centers of the catalysts. This quantitative method could be applied to evaluate the catalytic effects of any other additives on the thermal decomposition of various energetic compounds. Full article
(This article belongs to the Special Issue Nanoenergetic Materials: Preparation, Properties, and Applications)
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15 pages, 3905 KiB  
Article
Hydrophobization of Tobacco Mosaic Virus to Control the Mineralization of Organic Templates
by Petia Atanasova, Vladimir Atanasov, Lisa Wittum, Alexander Southan, Eunjin Choi, Christina Wege, Jochen Kerres, Sabine Eiben and Joachim Bill
Nanomaterials 2019, 9(5), 800; https://doi.org/10.3390/nano9050800 - 24 May 2019
Cited by 6 | Viewed by 3814
Abstract
The robust, anisotropic tobacco mosaic virus (TMV) provides a monodisperse particle size and defined surface chemistry. Owing to these properties, it became an excellent bio-template for the synthesis of diverse nanostructured organic/inorganic functional materials. For selective mineralization of the bio-template, specific functional groups [...] Read more.
The robust, anisotropic tobacco mosaic virus (TMV) provides a monodisperse particle size and defined surface chemistry. Owing to these properties, it became an excellent bio-template for the synthesis of diverse nanostructured organic/inorganic functional materials. For selective mineralization of the bio-template, specific functional groups were introduced by means of different genetically encoded amino acids or peptide sequences into the polar virus surface. An alternative approach for TMV surface functionalization is chemical coupling of organic molecules. To achieve mineralization control in this work, we developed a synthetic strategy to manipulate the surface hydrophilicity of the virus through covalent coupling of polymer molecules. Three different types of polymers, namely the perfluorinated (poly(pentafluorostyrene) (PFS)), the thermo-responsive poly(propylene glycol) acrylate (PPGA), and the block-copolymer polyethylene-block-poly(ethylene glycol) were examined. We have demonstrated that covalent attachment of hydrophobic polymer molecules with proper features retains the integrity of the virus structure. In addition, it was found that the degree of the virus hydrophobicity, examined via a ZnS mineralization test, could be tuned by the polymer properties. Full article
(This article belongs to the Special Issue Virus-Based Nanomaterials and Nanostructures)
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13 pages, 5245 KiB  
Article
Low-Power Graphene/ZnO Schottky UV Photodiodes with Enhanced Lateral Schottky Barrier Homogeneity
by Youngmin Lee, Deuk Young Kim and Sejoon Lee
Nanomaterials 2019, 9(5), 799; https://doi.org/10.3390/nano9050799 - 24 May 2019
Cited by 21 | Viewed by 4496
Abstract
The low-power, high-performance graphene/ZnO Schottky photodiodes were demonstrated through the direct sputter-growth of ZnO onto the thermally-cleaned graphene/SiO2/Si substrate at room temperature. Prior to the growth of ZnO, a thermal treatment of the graphene surface was performed at 280 °C for [...] Read more.
The low-power, high-performance graphene/ZnO Schottky photodiodes were demonstrated through the direct sputter-growth of ZnO onto the thermally-cleaned graphene/SiO2/Si substrate at room temperature. Prior to the growth of ZnO, a thermal treatment of the graphene surface was performed at 280 °C for 10 min in a vacuum to desorb chemical residues that may serve as trap sites at the interface between graphene and ZnO. The device clearly showed a rectifying behavior with the Schottky barrier of ≈0.61 eV and an ideality factor of 1.16. Under UV illumination, the device exhibited the excellent photoresponse characteristics in both forward and reverse bias regions. When illuminating UV light with the optical power density of 0.62 mW/cm2, the device revealed a high on/off current ratio of >103 even at a low bias voltage of 0.1 V. For the transient characteristics upon switching of UV light pulses, the device represented a fast and stable photoresponse (i.e., rise time: 0.16 s, decay time: 0.19 s). From the temperature-dependent current–voltage characteristics, such an outstanding photoresponse characteristic was found to arise from the enhanced Schottky barrier homogeneity via the thermal treatment of the graphene surface. The results suggest that the ZnO/graphene Schottky diode holds promise for the application in high-performance low-power UV photodetectors. Full article
(This article belongs to the Special Issue Graphene-Based Nanostructures and Optoelectronic Applications)
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9 pages, 3504 KiB  
Article
Interfacial Engineering of Graphene Nanosheets at MgO Particles for Thermal Conductivity Enhancement of Polymer Composites
by Wu Pan, Miaomiao He, Li Zhang, Yi Hou and Chen Chen
Nanomaterials 2019, 9(5), 798; https://doi.org/10.3390/nano9050798 - 24 May 2019
Cited by 7 | Viewed by 3020
Abstract
An important task in facilitating the development of thermally conducting graphene/polymer nanocomposites is to suppress the intrinsically strong intersheet π-π stacking of graphene, and thereby to improve the exfoliation and dispersion of graphene in the matrix. Here, a pre-programmed intercalation approach to realize [...] Read more.
An important task in facilitating the development of thermally conducting graphene/polymer nanocomposites is to suppress the intrinsically strong intersheet π-π stacking of graphene, and thereby to improve the exfoliation and dispersion of graphene in the matrix. Here, a pre-programmed intercalation approach to realize the in situ growth of graphene nanosheets at the inorganic template is demonstrated. Specifically, microsized MgO granules with controlled geometrical size were synthesized using a precipitation method, allowing the simultaneous realization of high surface activity. In the presence of a carbon and nitrogen source, the MgO granules were ready to induce the formation of graphene nanosheets (G@MgO), which allowed for the creation of tenacious linkages between graphene and template. More importantly, the incorporation of G@MgO into polymer composites largely pushed up the thermal conductivity, climbing from 0.39 W/m∙K for pristine polyethylene to 8.64 W/m∙K for polyethylene/G@MgO (60/40). This was accompanied by the simultaneous promotion of mechanical properties (tensile strength of around 30 MPa until 40 wt % addition of G@MgO), in contrast to the noteworthy decline of tensile strength for MgO-filled composites with over 20 wt.% fillers. Full article
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13 pages, 2957 KiB  
Article
Facile and Controllable Fabrication of Protein-Only Nanoparticles through Photo-Induced Crosslinking of Albumin and Their Application as DOX Carriers
by Xiangyu Long, Jun Ren, Chao Zhang, Fangling Ji and Lingyun Jia
Nanomaterials 2019, 9(5), 797; https://doi.org/10.3390/nano9050797 - 24 May 2019
Cited by 4 | Viewed by 4190
Abstract
Protein-based nanoparticles, as an alternative to conventional polymer-based nanoparticles, offer great advantages in biomedical applications owing to their functional and biocompatible characteristics. However, the route of fabrication towards protein-based nanoparticles faces substantial challenges, including limitations in size control and unavoidable usage of toxic [...] Read more.
Protein-based nanoparticles, as an alternative to conventional polymer-based nanoparticles, offer great advantages in biomedical applications owing to their functional and biocompatible characteristics. However, the route of fabrication towards protein-based nanoparticles faces substantial challenges, including limitations in size control and unavoidable usage of toxic crosslinkers or organic solvents, which may raise safety concerns related to products and their degradation components. In the present study, a photo-induced crosslinking approach was developed to prepare stable, size-controlled protein-only nanoparticles. The facile one-step reaction irradiated by visible light enables the formation of monodispersed bovine serum albumin nanoparticles (BSA NPs) within several minutes through a tyrosine photo-redox reaction, requiring no cross-linking agents. The size of the BSA NPs could be precisely manipulated (from 20 to 100 nm) by controlling the duration time of illumination. The resultant BSA NPs exhibited spherical morphology, and the α-helix structure in BSA was preserved. Further study demonstrated that the 35 nm doxorubicin (DOX)-loaded BSA NPs achieved a drug loading content of 6.3%, encapsulation efficiency of 70.7%, and a controlled release profile with responsivity to both pH and reducing conditions. Importantly, the in vitro drug delivery experiment demonstrated efficient cellular internalizations of the DOX-loaded BSA NPs and inhibitory activities on MCF-7 and HeLa cells. This method shows the promise of being a platform for the green synthesis of protein-only nanoparticles for biomedical applications. Full article
(This article belongs to the Special Issue Protein Nanostructures for Biomedical Applications)
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10 pages, 3194 KiB  
Article
Interlayer Difference of Bilayer-Stacked MoS2 Structure: Probing by Photoluminescence and Raman Spectroscopy
by Xiangzhe Zhang, Renyan Zhang, Xiaoming Zheng, Yi Zhang, Xueao Zhang, Chuyun Deng, Shiqiao Qin and Hang Yang
Nanomaterials 2019, 9(5), 796; https://doi.org/10.3390/nano9050796 - 24 May 2019
Cited by 9 | Viewed by 4461
Abstract
This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer [...] Read more.
This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer of BSS demonstrates PL redshift, Raman E 2 g 1 mode redshift, and lower PL intensity. Spatial inhomogeneity of PL and Raman are also observed in the BSS. Based on theoretical analysis, these exotic effects can be attributed to substrate-coupling-induced strain and doping. Our findings provide pertinent insight into film–substrate interaction, and are of great significance to researches on bilayer-stacked structures including twisted bilayer structure, Van der Waals hetero- and homo-structure. Full article
(This article belongs to the Special Issue Preparation and Properties of 2D Materials)
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20 pages, 3333 KiB  
Article
Influence of Preparation Procedure on Physicochemical and Antibacterial Properties of Titanate Nanotubes Modified with Silver
by Manu Jose, Paulina Sienkiewicz, Karolina Szymańska, Dominika Darowna, Dariusz Moszyński, Zofia Lendzion-Bieluń, Kacper Szymański and Sylwia Mozia
Nanomaterials 2019, 9(5), 795; https://doi.org/10.3390/nano9050795 - 23 May 2019
Cited by 22 | Viewed by 3925
Abstract
Silver nanoparticles (NPs) are effective antibacterial agents; however, aggregation of NPs and uncontrolled release of Ag+ affect their efficiency and may pose a risk to the environment. To overcome these disadvantages, immobilization of Ag onto titanate nanotubes (TNTs) was investigated. This paper [...] Read more.
Silver nanoparticles (NPs) are effective antibacterial agents; however, aggregation of NPs and uncontrolled release of Ag+ affect their efficiency and may pose a risk to the environment. To overcome these disadvantages, immobilization of Ag onto titanate nanotubes (TNTs) was investigated. This paper describes the physicochemical and antibacterial properties of silver incorporated titanate nanotubes (Ag/TNTs) prepared using five procedures and containing different Ag amounts (0.11–30.85 wt.%). The methods were (i) sol-gel followed by a hydrothermal process; (ii) photodeposition under ambient conditions; (iii) photodeposition under an inert atmosphere; (iv) NaBH4 reduction; and (v) electroless deposition after activation of TNTs with Sn2+. Depending on the synthesis procedure, the presence of metallic Ag NPs, AgO or AgCl was observed. The electroless method led to an additional deposition of SnO2 NPs. The antibacterial properties of Ag/TNTs were analyzed as a function of Ag content and released against Escherichia coli and Staphylococcus epidermidis. The best bactericidal properties exhibited Ag/TNTs prepared through the photodeposition process due to the higher interaction of exposed Ag NPs with bacteria. An increase of Ag loading resulted in improvement of antibacterial activity of Ag/TNTs although no direct correlation between silver content or release and inhibition of bacterial growth was found. Full article
(This article belongs to the Special Issue Recent Progress in Antimicrobial Nanomaterials)
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15 pages, 3345 KiB  
Article
Orange/Red Photoluminescence Enhancement Upon SF6 Plasma Treatment of Vertically Aligned ZnO Nanorods
by Amine Achour, Mohammad Islam, Sorin Vizireanu, Iftikhar Ahmad, Muhammad Aftab Akram, Khalid Saeed, Gheorghe Dinescu and Jean-Jacques Pireaux
Nanomaterials 2019, 9(5), 794; https://doi.org/10.3390/nano9050794 - 23 May 2019
Cited by 20 | Viewed by 3956
Abstract
Although the origin and possible mechanisms for green and yellow emission from different zinc oxide (ZnO) forms have been extensively investigated, the same for red/orange PL emission from ZnO nanorods (nR) remains largely unaddressed. In this work, vertically aligned zinc oxide nanorods arrays [...] Read more.
Although the origin and possible mechanisms for green and yellow emission from different zinc oxide (ZnO) forms have been extensively investigated, the same for red/orange PL emission from ZnO nanorods (nR) remains largely unaddressed. In this work, vertically aligned zinc oxide nanorods arrays (ZnO nR) were produced using hydrothermal process followed by plasma treatment in argon/sulfur hexafluoride (Ar/SF6) gas mixture for different time. The annealed samples were highly crystalline with ~45 nm crystallite size, (002) preferred orientation, and a relatively low strain value of 1.45 × 10−3, as determined from X-ray diffraction pattern. As compared to as-deposited ZnO nR, the plasma treatment under certain conditions demonstrated enhancement in the room temperature photoluminescence (PL) emission intensity, in the visible orange/red spectral regime, by a factor of 2. The PL intensity enhancement induced by SF6 plasma treatment may be attributed to surface chemistry modification as confirmed by X-ray photoelectron spectroscopy (XPS) studies. Several factors including presence of hydroxyl group on the ZnO surface, increased oxygen level in the ZnO lattice (OL), generation of F–OH and F–Zn bonds and passivation of surface states and bulk defects are considered to be active towards red/orange emission in the PL spectrum. The PL spectra were deconvoluted into component Gaussian sub-peaks representing transitions from conduction-band minimum (CBM) to oxygen interstitials (Oi) and CBM to oxygen vacancies (VO) with corresponding photon energies of 2.21 and 1.90 eV, respectively. The optimum plasma treatment route for ZnO nanostructures with resulting enhancement in the PL emission offers strong potential for photonic applications such as visible wavelength phosphors. Full article
(This article belongs to the Special Issue Functional Nanostructures for Sensors, Optoelectronic Devices and Drug Delivery)
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9 pages, 2463 KiB  
Article
Nano Hard Carbon Anodes for Sodium-Ion Batteries
by Dae-Yeong Kim, Dong-Hyun Kim, Soo-Hyun Kim, Eun-Kyung Lee, Sang-Kyun Park, Ji-Woong Lee, Yong-Sup Yun, Si-Young Choi and Jun Kang
Nanomaterials 2019, 9(5), 793; https://doi.org/10.3390/nano9050793 - 23 May 2019
Cited by 28 | Viewed by 6870
Abstract
A hindrance to the practical use of sodium-ion batteries is the lack of adequate anode materials. By utilizing the co-intercalation reaction, graphite, which is the most common anode material of lithium-ion batteries, was used for storing sodium ion. However, its performance, such as [...] Read more.
A hindrance to the practical use of sodium-ion batteries is the lack of adequate anode materials. By utilizing the co-intercalation reaction, graphite, which is the most common anode material of lithium-ion batteries, was used for storing sodium ion. However, its performance, such as reversible capacity and coulombic efficiency, remains unsatisfactory for practical needs. Therefore, to overcome these drawbacks, a new carbon material was synthesized so that co-intercalation could occur efficiently. This carbon material has the same morphology as carbon black; that is, it has a wide pathway due to a turbostratic structure, and a short pathway due to small primary particles that allows the co-intercalation reaction to occur efficiently. Additionally, due to the numerous voids present in the inner amorphous structure, the sodium storage capacity was greatly increased. Furthermore, owing to the coarse co-intercalation reaction due to the surface pore structure, the formation of solid-electrolyte interphase was greatly suppressed and the first cycle coulombic efficiency reached 80%. This study shows that the carbon material alone can be used to design good electrode materials for sodium-ion batteries without the use of next-generation materials. Full article
(This article belongs to the Special Issue Nano Carbon for Batteries Applications)
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16 pages, 2364 KiB  
Article
Interaction between Copper Oxide Nanoparticles and Amino Acids: Influence on the Antibacterial Activity
by Elena Badetti, Loris Calgaro, Laura Falchi, Alessandro Bonetto, Cinzia Bettiol, Benedetta Leonetti, Emmanuele Ambrosi, Elisabetta Zendri and Antonio Marcomini
Nanomaterials 2019, 9(5), 792; https://doi.org/10.3390/nano9050792 - 23 May 2019
Cited by 37 | Viewed by 4924
Abstract
The increasing concern about antibiotic-resistance has led to the search for alternative antimicrobial agents. In this effort, different metal oxide nanomaterials are currently under investigation, in order to assess their effectiveness, safety and mode of action. This study focused on CuO nanoparticles (CuO [...] Read more.
The increasing concern about antibiotic-resistance has led to the search for alternative antimicrobial agents. In this effort, different metal oxide nanomaterials are currently under investigation, in order to assess their effectiveness, safety and mode of action. This study focused on CuO nanoparticles (CuO NPs) and was aimed at evaluating how the properties and the antimicrobial activity of these nanomaterials may be affected by the interaction with ligands present in biological and environmental media. Ligands can attach to the surface of particles and/or contribute to their dissolution through ligand-assisted ion release and the formation of complexes with copper ions. Eight natural amino acids (L-Arg, L-Asp, L-Glu, L-Cys, L-Val, L-Leu, L-Phe, L-Tyr) were chosen as model molecules to investigate these interactions and the toxicity of the obtained materials against the Gram-positive bacterium Staphylococcus epidermidis ATCC 35984. A different behavior from pristine CuO NPs was observed, depending on the aminoacidic side chain. These results were supported by physico-chemical and colloidal characterization carried out by means of Fourier-Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric Analysis (TGA), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and light scattering techniques (Dynamic Light Scattering (DLS), Electrophoretic Light Scattering (ELS) and Centrifugal Separation Analysis (CSA). Full article
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13 pages, 2962 KiB  
Article
Efficient Light Management in a Monolithic Tandem Perovskite/Silicon Solar Cell by Using a Hybrid Metasurface
by Mahmoud H. Elshorbagy, Braulio García-Cámara, Eduardo López-Fraguas and Ricardo Vergaz
Nanomaterials 2019, 9(5), 791; https://doi.org/10.3390/nano9050791 - 23 May 2019
Cited by 15 | Viewed by 4185
Abstract
Solar energy is now dealing with the challenge of overcoming the Shockley–Queisser limit of single bandgap solar cells. Multilayer solar cells are a promising solution as the so-called third generation of solar cells. The combination of materials with different bandgap energies in multijunction [...] Read more.
Solar energy is now dealing with the challenge of overcoming the Shockley–Queisser limit of single bandgap solar cells. Multilayer solar cells are a promising solution as the so-called third generation of solar cells. The combination of materials with different bandgap energies in multijunction cells enables power conversion efficiencies up to 30% at reasonable costs. However, interfaces between different layers are critical due to optical losses. In this work, we propose a hybrid metasurface in a monolithic perovskite-silicon solar cell. The design takes advantage of light management to optimize the absorption in the perovskite, as well as an efficient light guiding towards the silicon subcell. Furthermore, we have also included the effect of a textured back contact. The optimum proposal provides an enhancement of the matched short-circuit current density of a 20.5% respect to the used planar reference. Full article
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13 pages, 3565 KiB  
Article
CuO/ZnO Heterojunction Nanorod Arrays Prepared by Photochemical Method with Improved UV Detecting Performance
by Jieni Li, Tingting Zhao, Mandar M. Shirolkar, Ming Li, Haiqian Wang and Henan Li
Nanomaterials 2019, 9(5), 790; https://doi.org/10.3390/nano9050790 - 23 May 2019
Cited by 22 | Viewed by 4213
Abstract
CuO/ZnO heterojunction nanorod arrays were synthesized using a facile photochemical deposition strategy. The morphology of CuO was related to the concentration of Cu2+ in the Cu(NO3)2 solution, UV illumination time, and the air annealing temperature. A possible reaction mechanism [...] Read more.
CuO/ZnO heterojunction nanorod arrays were synthesized using a facile photochemical deposition strategy. The morphology of CuO was related to the concentration of Cu2+ in the Cu(NO3)2 solution, UV illumination time, and the air annealing temperature. A possible reaction mechanism was proposed. In the photochemical deposition process, the OH− was generated in the vicinity of the ZnO nanorod arrays and reacted with Cu2+ and NO3− in the solution to form Cu2(NO3)(OH)3/ZnO heterojunction nanorod arrays firstly, which were converted into CuO/ZnO heterojunction nanorod arrays completely after air annealing at a low temperature. The fabricated CuO/ZnO heterojunction nanorod arrays exhibits a well-defined rectifying characteristic and an improved photo-response performance compared with pure ZnO nanorod arrays. Full article
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10 pages, 3752 KiB  
Article
Nonlinear Absorption Properties of Cr2Ge2Te6 and Its Application as an Ultra-Fast Optical Modulator
by Peng-fei Ma, Wei Lin, Hua-nian Zhang, Shan-hui Xu and Zhong-min Yang
Nanomaterials 2019, 9(5), 789; https://doi.org/10.3390/nano9050789 - 23 May 2019
Cited by 27 | Viewed by 3689
Abstract
In this manuscript, the nonlinear absorption properties of Cr2Ge2Te6 and its application in ultra-fast optical modulation are investigated. Typical parameters, namely, nonlinear absorption coefficient (β), saturation intensity, and modulation depth are measured to be ~1.66 × 10−9 [...] Read more.
In this manuscript, the nonlinear absorption properties of Cr2Ge2Te6 and its application in ultra-fast optical modulation are investigated. Typical parameters, namely, nonlinear absorption coefficient (β), saturation intensity, and modulation depth are measured to be ~1.66 × 10−9 m/W, 15.3 MW/cm2, and 5.8%, respectively. To investigate the feasibility of using the Cr2Ge2Te6 as an ultra-fast optical modulator, a ring-cavity passively mode-locked Er-doped fiber laser has been constructed. The output power/pulse, duration/pulse, and repetition rate/signal-to-noise ratios for the stable mode-locked operation are 2.88 mW/881 fs/19.33 MHz/48 dB, respectively, which proves that the Cr2Ge2Te6 has outstanding nonlinear optical properties and advantages in performing as an ultra-fast optical modulator. Further, the experimental results provide valuable references and open new avenues for developing two-dimensional, material-based, ultra-fast optical modulators and advanced photonic devices based on Cr2Ge2Te6. Full article
(This article belongs to the Special Issue Non-Linear Optical Effects in Nanomaterials)
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24 pages, 6705 KiB  
Article
A Promising Nano-Insulating-Oil for Industrial Application: Electrical Properties and Modification Mechanism
by Jiaqi Chen, Potao Sun, Wenxia Sima, Qianqiu Shao, Lian Ye and Chuang Li
Nanomaterials 2019, 9(5), 788; https://doi.org/10.3390/nano9050788 - 23 May 2019
Cited by 37 | Viewed by 3625
Abstract
Despite being discovered more than 20 years ago, nanofluids still cannot be used in the power industry. The fundamental reason is that nano-insulating oil has poor stability, and its electrical performance decreases under negative impulse voltage. We found that C60 nanoparticles can [...] Read more.
Despite being discovered more than 20 years ago, nanofluids still cannot be used in the power industry. The fundamental reason is that nano-insulating oil has poor stability, and its electrical performance decreases under negative impulse voltage. We found that C60 nanoparticles can maintain long-term stability in insulating oil without surface modification. C60 has strong electronegativity and photon absorption ability, which can comprehensively improve the electrical performance of insulating oil. This finding has great significance for the industrial application of nano-insulating oil. In this study, six concentrations of nano-C60 modified insulating oil (CMIO) were prepared, and their breakdown strength and dielectric properties were tested. The thermally stimulated current (TSC) curves of fresh oil (FO) and CMIO were experimentally determined. The test results indicate that C60 nanoparticles can simultaneously improve the positive and negative lightning impulse and power frequency breakdown voltage of insulating oil, while hardly increasing dielectric loss. At 150 mg/L, the positive and negative lightning impulse breakdown voltages of CMIO increased by 7.51% and 8.33%, respectively, compared with those of FO. The AC average breakdown voltage reached its peak (18.0% higher compared with FO) at a CMIO concentration of 200 mg/L. Based on the test results and the special properties of C60, we believe that changes in the trap parameters, the strong electron capture ability of C60, and the absorption capacity of C60 for photons enhanced the breakdown performance of insulating oil by C60 nanoparticles. Full article
(This article belongs to the Special Issue Advances in Nanofluids)
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23 pages, 4793 KiB  
Article
Cytotoxicity and Transcriptomic Analyses of Biogenic Palladium Nanoparticles in Human Ovarian Cancer Cells (SKOV3)
by Sangiliyandi Gurunathan, Muhammad Qasim, Chan Hyeok Park, Muhammad Arsalan Iqbal, Hyunjin Yoo, Jeong Ho Hwang, Sang Jun Uhm, Hyuk Song, Chankyu Park, Youngsok Choi, Jin-Hoi Kim and Kwonho Hong
Nanomaterials 2019, 9(5), 787; https://doi.org/10.3390/nano9050787 - 22 May 2019
Cited by 38 | Viewed by 4561
Abstract
Ovarian cancer incidence continues to increase at an alarming rate. Although various therapeutic approaches exist for ovarian cancer, they have limitations, including undesired side effects. Therefore, nanoparticle (NP)-mediated therapy may be a viable, biocompatible, and suitable alternative. To the best of our knowledge, [...] Read more.
Ovarian cancer incidence continues to increase at an alarming rate. Although various therapeutic approaches exist for ovarian cancer, they have limitations, including undesired side effects. Therefore, nanoparticle (NP)-mediated therapy may be a viable, biocompatible, and suitable alternative. To the best of our knowledge, no comprehensive analysis has been undertaken on the cytotoxicity and cellular pathways involved in ovarian cancer cells, particularly SKOV3 cells. Here, we investigated the effect of palladium NPs (PdNPs) and the molecular mechanisms and cellular pathways involved in ovarian cancer. We assayed cell viability, proliferation, cytotoxicity, oxidative stress, DNA damage, and apoptosis and performed an RNA-Seq analysis. The results showed that PdNPs elicited concentration-dependent decreases in cell viability and proliferation and induced increasing cytotoxicity at increasing concentrations, as determined by leakage of lactate dehydrogenase, increased levels of reactive oxygen species and malondialdehyde, and decreased levels of antioxidants like glutathione and superoxide dismutase. Furthermore, our study revealed that PdNPs induce mitochondrial dysfunction by altering mitochondrial membrane potential, reducing adenosine triphosphate levels, inducing DNA damage, and activating caspase 3, all of which significantly induced apoptosis in SKOV3 cells following PdNPs treatment. Gene ontology (GO) term analysis of PdNPs-exposed SKOV3 cells showed various dysregulated pathways, particularly nucleosome assembly, telomere organization, and rDNA chromatin silencing. When genes downregulated by PdNPs were applied to GO term enrichment analysis, nucleosome assembly was the top-ranked biological pathway. We also provide evidence for an association between PdNPs exposure and multiple layers of epigenetic transcriptional control and establish a molecular basis for NP-mediated apoptosis. These findings provide a foundation, potential targets, and novel insights into the mechanism underlying toxicity and pathways in SKOV3 cells, and open new avenues to identify novel targets for ovarian cancer treatment. Full article
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19 pages, 32449 KiB  
Article
Performance of Polyester-Based Electrospun Scaffolds under In Vitro Hydrolytic Conditions: From Short-Term to Long-Term Applications
by Oscar Gil-Castell, José David Badia, Jordi Bou and Amparo Ribes-Greus
Nanomaterials 2019, 9(5), 786; https://doi.org/10.3390/nano9050786 - 22 May 2019
Cited by 16 | Viewed by 3366
Abstract
The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were [...] Read more.
The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °C. The scaffolds for short-time applications were PLGA and PDO, in which the molar mass diminished down to 20% in a 20–30 days lifespan. While PDO developed crystallinity that prevented the geometry of the fibres, those of PLGA coalesced and collapsed. The scaffolds for long-term applications were PCL and PHB, in which the molar mass followed a progressive decrease, reaching values of 10% for PCL and almost 50% for PHB after 650 days of immersion. This resistant pattern was mainly ascribed to the stability of the crystalline domains of the fibres, in which the diameters remained almost unaffected. From the perspective of an adequate balance between the durability and degradation, this study may serve technologists as a reference point to design polyester-based scaffolds for biomedical applications. Full article
(This article belongs to the Special Issue Potential of Electrospun Nanofibrous Devices: Design and Validation under a Multiapplication Perspective)
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12 pages, 5518 KiB  
Article
Magnetic Nanoparticles Functionalized Few-Mode-Fiber-Based Plasmonic Vector Magnetometer
by Yaofei Chen, Weiting Sun, Yaxin Zhang, Guishi Liu, Yunhan Luo, Jiangli Dong, Yongchun Zhong, Wenguo Zhu, Jianhui Yu and Zhe Chen
Nanomaterials 2019, 9(5), 785; https://doi.org/10.3390/nano9050785 - 22 May 2019
Cited by 42 | Viewed by 3862
Abstract
In this work, we demonstrate a highly-sensitive vector magnetometer based on a few-mode-fiber-based surface plasmon resonance (SPR) sensor functionalized by magnetic nanoparticles (MNPs) in liquid. To fabricate the sensor, a few-mode fiber is side-polished and coated with a gold film, forming an SPR [...] Read more.
In this work, we demonstrate a highly-sensitive vector magnetometer based on a few-mode-fiber-based surface plasmon resonance (SPR) sensor functionalized by magnetic nanoparticles (MNPs) in liquid. To fabricate the sensor, a few-mode fiber is side-polished and coated with a gold film, forming an SPR sensor that is highly sensitive to the surrounding refractive index. The vector magnetometer operates based on the mechanism whereby the intensity and orientation of an external magnetic field alters the anisotropic aggregation of the MNPs and thus the refractive index around the fiber SPR device. This, in turn, shifts the resonance wavelength of the surface plasmon. Experimental results show the proposed sensor is very sensitive to magnetic-field intensity and orientation (0.692 nm/Oe and −11.917 nm/°, respectively). These remarkable sensitivities to both magnetic-field intensity and orientation mean that the proposed sensor can be used in applications to detect weak magnetic-field vectors. Full article
(This article belongs to the Special Issue Applications and Properties of Magnetic Nanoparticles)
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11 pages, 2496 KiB  
Article
The Characteristics of Transparent Non-Volatile Memory Devices Employing Si-Rich SiOX as a Charge Trapping Layer and Indium-Tin-Zinc-Oxide
by Joong-Hyun Park, Myung-Hun Shin and Jun-Sin Yi
Nanomaterials 2019, 9(5), 784; https://doi.org/10.3390/nano9050784 - 22 May 2019
Cited by 12 | Viewed by 3620
Abstract
We fabricated the transparent non-volatile memory (NVM) of a bottom gate thin film transistor (TFT) for the integrated logic devices of display applications. The NVM TFT utilized indium–tin–zinc–oxide (ITZO) as an active channel layer and multi-oxide structure of SiO2 (blocking layer)/Si-rich SiO [...] Read more.
We fabricated the transparent non-volatile memory (NVM) of a bottom gate thin film transistor (TFT) for the integrated logic devices of display applications. The NVM TFT utilized indium–tin–zinc–oxide (ITZO) as an active channel layer and multi-oxide structure of SiO2 (blocking layer)/Si-rich SiOX (charge trapping layer)/SiOXNY (tunneling layer) as a gate insulator. The insulators were deposited using inductive coupled plasma chemical vapor deposition, and during the deposition, the trap states of the Si-rich SiOx charge trapping layer could be controlled to widen the memory window with the gas ratio (GR) of SiH4:N2O, which was confirmed by fourier transform infrared spectroscopy (FT-IR). We fabricated the metal–insulator–silicon (MIS) capacitors of the insulator structures on n-type Si substrate and demonstrated that the hysteresis capacitive curves of the MIS capacitors were a function of sweep voltage and trap density (or GR). At the GR6 (SiH4:N2O = 30:5), the MIS capacitor exhibited the widest memory window; the flat band voltage (ΔVFB) shifts of 4.45 V was obtained at the sweep voltage of ±11 V for 10 s, and it was expected to maintain ~71% of the initial value after 10 years. Using the Si-rich SiOX charge trapping layer deposited at the GR6 condition, we fabricated a bottom gate ITZO NVM TFT showing excellent drain current to gate voltage transfer characteristics. The field-effect mobility of 27.2 cm2/Vs, threshold voltage of 0.15 V, subthreshold swing of 0.17 V/dec, and on/off current ratio of 7.57 × 107 were obtained at the initial sweep of the devices. As an NVM, ΔVFB was shifted by 2.08 V in the programing mode with a positive gate voltage pulse of 11 V and 1 μs. The ΔVFB was returned to the pristine condition with a negative voltage pulse of −1 V and 1 μs under a 400–700 nm light illumination of ~10 mWcm−2 in erasing mode, when the light excites the electrons to escape from the charge trapping layer. Using this operation condition, ~90% (1.87 V) of initial ΔVFB (2.08 V) was expected to be retained over 10 years. The developed transparent NVM using Si-rich SiOx and ITZO can be a promising candidate for future display devices integrating logic devices on panels. Full article
(This article belongs to the Special Issue Nanomaterials for the Advanced Manufacturing of Electronic Devices)
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14 pages, 3325 KiB  
Article
Novel Quasi-Solid-State Electrolytes based on Electrospun Poly(vinylidene fluoride) Fiber Membranes for Highly Efficient and Stable Dye-Sensitized Solar Cells
by Fan Cheng, Ying Ou, Guoliang Liu, Li Zhao, Binghai Dong, Shimin Wang and Sheng Wen
Nanomaterials 2019, 9(5), 783; https://doi.org/10.3390/nano9050783 - 22 May 2019
Cited by 19 | Viewed by 3953
Abstract
To obtain new highly efficient and stable quasi-solid dye-sensitized solar cells (QS-DSSCs) that can meet the requirements for the large-scale commercial application of solar cells, we have developed a novel quasi-solid-state electrolyte, based on an electrospun polyvinylidene fluoride (PVDF) membrane. The structure and [...] Read more.
To obtain new highly efficient and stable quasi-solid dye-sensitized solar cells (QS-DSSCs) that can meet the requirements for the large-scale commercial application of solar cells, we have developed a novel quasi-solid-state electrolyte, based on an electrospun polyvinylidene fluoride (PVDF) membrane. The structure and properties of electrospun PVDF membranes were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), thermogravimetric (TG), and mechanical testing. The results indicate that the electrospun PVDF membrane has a three-dimensional network structure with extremely high porosity, which not only acts as a barrier to prevent electrolyte leakage but also provides a channel for the transmission of ions in the electrolyte, thereby effectively guaranteeing the high photoelectric conversion efficiency of the cells. The membrane was observed to withstand the conditions of hot-press (110 °C), and exhibited good thermal stability and mechanical strength, which are critical for the long-term stability and safety of the cells. The photovoltaic characteristics and stabilities of QS-DSSCs were compared with DSSCs based on an ionic liquid electrolyte (L-DSSC). QS-DSSCs with an 80 μm thick nanofiber electrolyte membrane showed a conversion efficiency of 8.63%, whereas an identical cell based on the corresponding ionic liquid electrolyte showed an efficiency of 9.30%. The stability test showed that, under indoor and outdoor conditions, after 390 h, the L-DSSCs failed. Meanwhile, the QS-DSSCs also maintained 84% and 77% of the original efficiency. The results show that, compared to the liquid electrolyte, the design of the quasi-solid electrolytes based on electrospun PVDF nanofiber membrane not only demonstrates the high conversion efficiency of DSSCs but also enhances the stability of the DSSCs, which provides the possibility for the fabrication of solar cells with higher efficiency and stability. Full article
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10 pages, 2065 KiB  
Article
Formation of Fe-Te Nanostructures during in Situ Fe Heavy Doping of Bi2Te3
by Jing Liang, Xiong Yao, Yu Jun Zhang, Fei Chen, Yuanzhen Chen and Iam Keong Sou
Nanomaterials 2019, 9(5), 782; https://doi.org/10.3390/nano9050782 - 22 May 2019
Cited by 3 | Viewed by 3584
Abstract
To study the in situ doping effect upon monotonically increasing dopant concentration, a Bi2Te3 layer doped with Fe up to ~6.9% along the growth direction was fabricated by the molecular beam epitaxy (MBE) technique. Its resistance versus temperature curve displays [...] Read more.
To study the in situ doping effect upon monotonically increasing dopant concentration, a Bi2Te3 layer doped with Fe up to ~6.9% along the growth direction was fabricated by the molecular beam epitaxy (MBE) technique. Its resistance versus temperature curve displays a superconductivity transition at about 12.3 K. Detailed structural and chemical analysis via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS) reveal that this layer consists of two types of unexpected Fe-Te nanostructures: one is FeTe thin layer formed near the surface, and the other is FeTe2 nanorod embedded in the Bi2Te3 layer. Based on the results of further electrical and magnetotransport studies, it is likely that the observed superconductivity originates from the interface between the FeTe nanostructure and the neighboring Bi2Te3 layer. We have addressed the formation mechanisms of the observed nanostructures, which is attributed to the strong reaction between Fe and Te atoms during the growth process. The findings of this study also provide an unusual approach to synthesizing nanostructures via heavy doping if the dopant element is strongly reactive with an element in the host matrix. Full article
(This article belongs to the Special Issue Novel Synthesis Strategies and Phenomena in Low-Dimensional Structures Like Nanowires and Thin Films)
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13 pages, 4543 KiB  
Article
Plasmon Sensitized Heterojunction 2D Ultrathin Ag/AgI-δ-Bi2O3 for Enhanced Photocatalytic Nitrogen Fixation
by Xiaoming Gao, Yanyan Shang, Kailong Gao and Feng Fu
Nanomaterials 2019, 9(5), 781; https://doi.org/10.3390/nano9050781 - 22 May 2019
Cited by 24 | Viewed by 3869
Abstract
A novel 2D ultrathin Ag/AgI-δ-Bi2O3 photocatalyst was constructed by a facile hydrothermal and in situ photodeposition method, which presented a uniform nanosheet structure with an average height of 6 nm. Its composition, morphology and light-harvesting properties were characterized by X-ray [...] Read more.
A novel 2D ultrathin Ag/AgI-δ-Bi2O3 photocatalyst was constructed by a facile hydrothermal and in situ photodeposition method, which presented a uniform nanosheet structure with an average height of 6 nm. Its composition, morphology and light-harvesting properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectrophotometer (UV–vis) and photoluminescence (PL) measurements in detail. The Ag/AgI-δ-Bi2O3 nanocomposites showed an excellent photocatalytic nitrogen fixation performance of 420 μmol L−1 g−1 h−1 in water without any sacrificial agent. The introduction of Ag/AgI nanoparticles caused the morphology modification of δ-Bi2O3, a higher concentration of oxygen vacancy, and the construction of a plasmon sensitized heterojunction, resulting in enhanced light absorption, improved separation efficiency of charge carriers and strong N2 absorption and activation ability, which are responsible for the superior photocatalytic performance of Ag/AgI-δ-Bi2O3. Full article
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8 pages, 1708 KiB  
Article
Silver Nanoparticles on Cellulose Surfaces: Quantitative Measurements
by Ana Patrícia Carapeto, Ana Maria Ferraria and Ana Maria Botelho do Rego
Nanomaterials 2019, 9(5), 780; https://doi.org/10.3390/nano9050780 - 22 May 2019
Cited by 10 | Viewed by 3264
Abstract
In this work, cellulose films pre-activated with carbonyldiimidazole (CDI) and grafted with 1,6-hexanediamine, were decorated with silver nanoparticles (AgNPs). The generation of AgNPs was followed by quartz crystal microbalance (QCM). The obtained films were characterized by X-Ray Photoelectron Spectroscopy (XPS) and imaged by [...] Read more.
In this work, cellulose films pre-activated with carbonyldiimidazole (CDI) and grafted with 1,6-hexanediamine, were decorated with silver nanoparticles (AgNPs). The generation of AgNPs was followed by quartz crystal microbalance (QCM). The obtained films were characterized by X-Ray Photoelectron Spectroscopy (XPS) and imaged by atomic force microscopy (AFM). XPS confirmed the synthesis in situ of AgNPs on the film attesting their oxidation state. The results from the three techniques were compared showing how sound the quantitative treatment of the results issued from these techniques can be. The main objective of this work is exactly to show that the quantitative exploration of the results of different characterization techniques can and should be practiced systematically instead of just comparing them qualitatively. Full article
(This article belongs to the Special Issue Functionalizing of Cellulose or Chitosan Surfaces with Metallic Nanoparticles)
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12 pages, 3216 KiB  
Article
A Sensitive Piezoresistive Tactile Sensor Combining Two Microstructures
by Xuguang Sun, Jianhai Sun, Shuaikang Zheng, Chunkai Wang, Wenshuo Tan, Jingong Zhang, Chunxiu Liu, Chang Liu, Tong Li, Zhimei Qi and Ning Xue
Nanomaterials 2019, 9(5), 779; https://doi.org/10.3390/nano9050779 - 21 May 2019
Cited by 24 | Viewed by 3605
Abstract
A tactile sensor is an indispensable component for electronic skin, mimicking the sensing function of organism skin. Various sensing materials and microstructures have been adopted in the fabrication of tactile sensors. Herein, we propose a highly sensitive flexible tactile sensor composed of nanocomposites [...] Read more.
A tactile sensor is an indispensable component for electronic skin, mimicking the sensing function of organism skin. Various sensing materials and microstructures have been adopted in the fabrication of tactile sensors. Herein, we propose a highly sensitive flexible tactile sensor composed of nanocomposites with pyramid and irregularly rough microstructures and implement a comparison of piezoresistive properties of nanocomposites with varying weight proportions of multi-wall nanotubes and carbon black particles. In addition to the simple and low-cost fabrication method, the tactile sensor can reach high sensitivity of 3.2 kPa−1 in the range of <1 kPa and fast dynamic response of 217 ms (loading) and 81 ms (recovery) at 40 kPa pressure. Moreover, body movement monitoring applications have been carried out utilizing the flexible tactile sensor. A sound monitoring application further indicates the potential for applications in electronic skin, human–computer interaction, and physiological detection. Full article
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9 pages, 3242 KiB  
Article
Self-Powered Flexible Blood Oxygen Monitoring System Based on a Triboelectric Nanogenerator
by Huamin Chen, Yun Xu, Jiushuang Zhang, Weitong Wu and Guofeng Song
Nanomaterials 2019, 9(5), 778; https://doi.org/10.3390/nano9050778 - 21 May 2019
Cited by 19 | Viewed by 3744
Abstract
Flexible optoelectronics based on inorganic functional components have attracted worldwide attention due to their inherent advantages. However, the power supply problem presents a significant obstacle to the commercialization of wearable optoelectronics. Triboelectric nanogenerator (TENG) technology has the potential to realize self-powered applications compared [...] Read more.
Flexible optoelectronics based on inorganic functional components have attracted worldwide attention due to their inherent advantages. However, the power supply problem presents a significant obstacle to the commercialization of wearable optoelectronics. Triboelectric nanogenerator (TENG) technology has the potential to realize self-powered applications compared to the conventional charging technologies. Herein, a flexible self-powered blood oxygen monitoring system based on TENG was first demonstrated. The flexibility of the TENG is mainly due to the inherent properties of polydimethylsiloxane (PDMS) and the continuously undulating surface of crumpled gold (Au) and the rough surface on the electrode and PDMS effectively increased the output performance. The output voltage, output current density, and power density were 75.3 V, 7.4 μA, and 0.2 mW/cm2, respectively. By etching the sacrificial layer, we then derived a flexible blood oxygen and pulse detector without any obvious performance degradation. Powered by the TENG, the detector is mounted onto the thumbnail, from where it detects a stable photoplethysmography (PPG) signal which can be used to calculate the oxyhemoglobin saturation and pulse rate. This self-powered system provides a new way to sustainably monitor physiological parameters, which paves the way for development of wearable electronics and battery-free systems. Full article
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11 pages, 3957 KiB  
Article
Design and Regulation of Novel MnFe2O4@C Nanowires as High Performance Electrode for Supercapacitor
by Lei Geng, Fengfeng Yan, Chenhao Dong and Cuihua An
Nanomaterials 2019, 9(5), 777; https://doi.org/10.3390/nano9050777 - 21 May 2019
Cited by 38 | Viewed by 4017
Abstract
Bimetallic oxides have been considered as potential candidates for supercapacitors due to their relatively high electric conductivity, abundant redox reactions and cheapness. However, nanoparticle aggregation and huge volume variation during charging-discharging procedures make it hard for them to be applied widely. In this [...] Read more.
Bimetallic oxides have been considered as potential candidates for supercapacitors due to their relatively high electric conductivity, abundant redox reactions and cheapness. However, nanoparticle aggregation and huge volume variation during charging-discharging procedures make it hard for them to be applied widely. In this work, one-dimensional (1D) MnFe2O4@C nanowires were in-situ synthesized via a simply modified micro-emulsion technique, followed by thermal treatment. The novel 1D and core-shell architecture, and in-situ carbon coating promote its electric conductivity and porous feature. Due to these advantages, the MnFe2O4@C electrode exhibits a high specific capacitance of 824 F·g−1 at 0.1 A·g−1 and remains 476 F·g−1 at 5 A·g−1. After 10,000 cycles, the capacitance retention of the MnFe2O4@C electrode is up to 93.9%, suggesting its excellent long-term cycling stability. After assembling with activated carbon (AC) to form a MnFe2O4@C//AC device, the energy density of this MnFe2O4@C//AC device is 27 W·h·kg−1 at a power density of 290 W·kg−1, and remains at a 10 W·h·kg−1 energy density at a high power density of 9300 W·kg−1. Full article
(This article belongs to the Special Issue Novel Synthesis Strategies and Phenomena in Low-Dimensional Structures Like Nanowires and Thin Films)
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