Nanomaterials

9 pages, 1824 KiB

Open AccessArticle

Metal Slot Color Filter Based on Thin Air Slots on Silver Block Array

by Youngsoo Kim, Kihwan Moon, Young Jin Lee, Seokhyeon Hong and Soon-Hong Kwon

Nanomaterials 2019, 9(6), 912; https://doi.org/10.3390/nano9060912 - 25 Jun 2019

Viewed by 3392

The human eye perceives the color of visible light depending on the spectrum of the incident light. Hence, the ability of color expression is very important in display devices. For practical applications, the transmitted color filter requires high transmittance and vivid colors, covering [...] Read more.

The human eye perceives the color of visible light depending on the spectrum of the incident light. Hence, the ability of color expression is very important in display devices. For practical applications, the transmitted color filter requires high transmittance and vivid colors, covering full standard default color spaces (sRGB). In this paper, we propose a color filter with a silver block array on a silica substrate structure with nanoscale air slots where strong transmission is observed through the slots between silver blocks. We investigated the transmitted color by simulating the transmission spectra as functions of various structure parameters. The proposed structure with an extremely small pixel size of less than 300 nm covers 90% of sRGB color depending on the structure and has a narrow angular distribution of transmitted light. Full article

(This article belongs to the Special Issue Plasmonic Nanostructures and Related Applications)

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10 pages, 1349 KiB

Open AccessArticle

A Model for Non-Arrhenius Ionic Conductivity

by Masaru Aniya and Masahiro Ikeda

Nanomaterials 2019, 9(6), 911; https://doi.org/10.3390/nano9060911 - 24 Jun 2019

Cited by 14 | Viewed by 4379

Abstract

Non-Arrhenius ionic conductivity is observed in various solid electrolytes. The behavior is intriguing, because it limits the magnitude of ionic conductivity at high temperatures. Understanding the nature of this behavior is of fundamental interest and deserves attention. In the present study, the temperature [...] Read more.

Non-Arrhenius ionic conductivity is observed in various solid electrolytes. The behavior is intriguing, because it limits the magnitude of ionic conductivity at high temperatures. Understanding the nature of this behavior is of fundamental interest and deserves attention. In the present study, the temperature dependence of the ionic conductivity in solids and liquids is analyzed using the Bond Strength–Coordination Number Fluctuation (BSCNF) model developed by ourselves. It is shown that our model describes well the temperature dependence of ionic conductivity that varies from Arrhenius to non-Arrhenius-type behavior. According to our model, the non-Arrhenius behavior is controlled by the degree of binding energy fluctuation between the mobile species and the surroundings. A brief discussion on a possible size effect in non-Arrhenius behavior is also given. Within the available data, the BSCNF model suggests that the size effect in the degree of the non-Arrhenius mass transport behavior in a poly (methyl ethyl ether)/polystyrene (PVME/PS) blend is different from that in a-polystyrene and polyamide copolymer PA66/6I. Full article

(This article belongs to the Special Issue Nanotechnologies and Nanomaterials: Selected Papers from CCMR 2019)

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23 pages, 8241 KiB

Open AccessReview

A Review on Catalytic Nanomaterials for Volatile Organic Compounds VOC Removal and Their Applications for Healthy Buildings

by Kwok Wei Shah and Wenxin Li

Nanomaterials 2019, 9(6), 910; https://doi.org/10.3390/nano9060910 - 23 Jun 2019

Cited by 74 | Viewed by 8685

Abstract

In order to improve the indoor air quality, volatile organic compounds (VOCs) can be removed via an efficient approach by using catalysts. This review proposed a comprehensive summary of various nanomaterials for thermal/photo-catalytic removal of VOCs. These representative materials are mainly categorized as [...] Read more.

In order to improve the indoor air quality, volatile organic compounds (VOCs) can be removed via an efficient approach by using catalysts. This review proposed a comprehensive summary of various nanomaterials for thermal/photo-catalytic removal of VOCs. These representative materials are mainly categorized as carbon-based and metallic oxides materials, and their morphologies, synthesis techniques, and performances have been explained in detail. To improve the indoor and outdoor air quality, the catalytic nanomaterials can be utilized for emerging building applications such as VOC-reduction coatings, paints, air filters, and construction materials. Due to the characteristics of low cost, non-toxic and high chemical stability, metallic oxides such as TiO₂ and ZnO have been widely investigated for decades and dominate the application market of VOC-removal catalyst in buildings. Since other catalysts also showed brilliant performance and have been theoretically researched, they can be potential candidates for applications in future healthy buildings. This review will contribute to further knowledge and greater potential applications of promising VOC-reducing catalytic nanomaterials on healthier buildings for a better indoor and outdoor environment well-being. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Pollutant Gases Reduction and Abatement)

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0 pages, 3021 KiB

Open AccessArticle

RETRACTED: Amelioration of Experimentally Induced Arthritis by Reducing Reactive Oxygen Species Production through the Intra-Articular Injection of Water-Soluble Fullerenol

by Wen-Shuo Kuo, Chia-Tse Weng, Jian-Hua Chen, Chao-Liang Wu, Ai-Li Shiau, Jeng-Long Hsieh, Edmund Cheung So, Po-Ting Wu and Shih-Yao Chen

Nanomaterials 2019, 9(6), 909; https://doi.org/10.3390/nano9060909 - 23 Jun 2019

Cited by 8 | Viewed by 4165 | Retraction

Abstract

Accumulated evidence suggests a pathogenic role of reactive oxygen species (ROS) in perpetually rheumatoid joints. Therefore, the application of radical scavengers for reducing the accumulation of ROS is beneficial for patients with rheumatoid arthritis (RA). We synthesized water-soluble fullerenols that could inhibit the [...] Read more.

Accumulated evidence suggests a pathogenic role of reactive oxygen species (ROS) in perpetually rheumatoid joints. Therefore, the application of radical scavengers for reducing the accumulation of ROS is beneficial for patients with rheumatoid arthritis (RA). We synthesized water-soluble fullerenols that could inhibit the production of ROS and applied intra-articular (i.a.) injection in an experimental arthritis model to examine the anti-arthritic effect of the synthesized compound. RAW 264.7 cells were used to examine the activity of the synthesized fullerenol. Collagen-induced arthritis (CIA) was induced in Sprague–Dawley rats by injecting their joints with fullerenol. The therapeutic effects were evaluated using the articular index as well as radiological and histological scores. Dose-dependent suppression of nitric oxide (NO) production caused by the fullerenol was demonstrated in the RAW 264.7 cell culture, thus confirming the ability of fullerenol to reduce ROS production. In the fullerenol-injected joints, articular indexes, synovial expression of ROS, histological and radiological scores, pannus formation, and erosion of cartilage and bone were all reduced. Moreover, interleukin (IL)-1β and vascular endothelial growth factor (VEGF) levels were reduced, and fewer von Willebrand factor (vWF)-stained areas were identified in the fullerenol-treated joints than in control joints. The i.a. injection of fullerenol for reducing ROS production can ameliorate arthritis in joints by suppressing pro-inflammatory cytokine production and the angiogenesis process. Thus, the i.a. injection of fullerenol for reducing the production of ROS can be used as a pharmacological approach for RA patients. Full article

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12 pages, 3182 KiB

Open AccessArticle

MAPbI₃ Incorporated with Carboxyl Group Chelated Titania for Planar Perovskite Solar Cells in Low-Temperature Process

by Pei-Shan Li, Rathinam Balamurugan, Bo-Tau Liu, Rong-Ho Lee and Hsueh-Tao Chou

Nanomaterials 2019, 9(6), 908; https://doi.org/10.3390/nano9060908 - 23 Jun 2019

Cited by 11 | Viewed by 3952

Abstract

Low-temperature, solution-processed, highly efficient hybrid organic/inorganic perovskite planar heterojunction solar cells were fabricated by incorporating reactive crystalline titania (h-TAc) into MAPbI₃ layers. The h-TAc was prepared by the sol-gel reaction at low temperature followed by solvothermal treatment. The photoelectrical properties of the [...] Read more.

Low-temperature, solution-processed, highly efficient hybrid organic/inorganic perovskite planar heterojunction solar cells were fabricated by incorporating reactive crystalline titania (h-TAc) into MAPbI₃ layers. The h-TAc was prepared by the sol-gel reaction at low temperature followed by solvothermal treatment. The photoelectrical properties of the solar cells with h-TAc were analyzed. The incorporation with 0.85-wt% h-TAc showed the highest power conversion efficiency (PCE, 15.9%), increasing 69% compared to the pristine cell. The enhancement arose from large-grained microstructures, leading to a low rate of charge recombination. The carboxyl groups chelated on the surface of h-TAc revealed a strong attraction to lead ions, which are significantly helpful to MAPbI₃ crystal growth. Full article

(This article belongs to the Special Issue Synthesis and Applications of Nanomaterials Based on Perovskites)

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13 pages, 5358 KiB

Open AccessArticle

Engineering the Dimensional Interface of BiVO₄-2D Reduced Graphene Oxide (RGO) Nanocomposite for Enhanced Visible Light Photocatalytic Performance

by Jing Sun, Chunxiao Wang, Tingting Shen, Hongchen Song, Danqi Li, Rusong Zhao and Xikui Wang

Nanomaterials 2019, 9(6), 907; https://doi.org/10.3390/nano9060907 - 21 Jun 2019

Cited by 28 | Viewed by 4345

Abstract

Graphene as a two-dimensional (2D) nanoplatform is beneficial for assembling a 2D heterojunction photocatalytic system to promote electron transfer in semiconductor composites. Here a BiVO₄ nanosheets/reduced graphene oxide (RGO) based 2D-2D heterojunction photocatalytic system as well as 0D-2D BiVO₄ nanoparticles/RGO and [...] Read more.

Graphene as a two-dimensional (2D) nanoplatform is beneficial for assembling a 2D heterojunction photocatalytic system to promote electron transfer in semiconductor composites. Here a BiVO₄ nanosheets/reduced graphene oxide (RGO) based 2D-2D heterojunction photocatalytic system as well as 0D-2D BiVO₄ nanoparticles/RGO and 1D-2D BiVO₄ nanotubes/RGO nanocomposites are fabricated by a feasible solvothermal process. During the synthesis; the growth of BiVO₄ and the intimate interfacial contact between BiVO₄ and RGO occur simultaneously. Compared to 0D-2D and 1D-2D heterojunctions, the resulting 2D-2D BiVO₄ nanosheets/RGO composites yield superior chemical coupling; leading to exhibit higher photocatalytic activity toward the degradation of acetaminophen under visible light irradiation. Photoluminescence (PL) and photocurrent experiments revealed that the apparent electron transfer rate in 2D-2D BiVO₄ nanosheets/RGO composites is faster than that in 0D-2D BiVO₄ nanoparticles/RGO composites. The experimental findings presented here clearly demonstrate that the 2D-2D heterojunction interface can highlight the optoelectronic coupling between nanomaterials and promote the electron–hole separation. This study will motivate new developments in dimensionality factors on designing the heterojunction photocatalysts and promote their photodegradation photocatalytic application in environmental issues. Full article

(This article belongs to the Special Issue Nanocomposites for Environmental and Energy Applications)

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15 pages, 7082 KiB

Open AccessArticle

Molybdenum Disulfide Quantum Dots Prepared by Bipolar-Electrode Electrochemical Scissoring

by Yang Li, Xiaoxia Wang, Mengli Liu, Heng Luo, Lianwen Deng, Lei Huang, Shuang Wei, Congli Zhou and Yuanhong Xu

Nanomaterials 2019, 9(6), 906; https://doi.org/10.3390/nano9060906 - 21 Jun 2019

Cited by 16 | Viewed by 4000

Abstract

A convenient bipolar-electrode (BPE) electrochemical method was engineered to produce molybdenum disulfide (MoS₂) quantum dots (QDs) using pure phosphate buffer (PBS) as the electrolyte and the MoS₂ powder as the precursor. Meanwhile, the corresponding by-product precipitate was studied, in which [...] Read more.

A convenient bipolar-electrode (BPE) electrochemical method was engineered to produce molybdenum disulfide (MoS₂) quantum dots (QDs) using pure phosphate buffer (PBS) as the electrolyte and the MoS₂ powder as the precursor. Meanwhile, the corresponding by-product precipitate was studied, in which MoS₂ nanosheets were observed. The BPE design would not be restricted by the shape and size of the MoS₂ precursor. It could lead to the defect generation and 2H → 1T phase variation of the MoS₂, resulting in the formation of nanosheets and finally the QDs. The as-prepared MoS₂ QDs exhibited high photoluminescence (PL) quantum yield of 13.9% and average lateral size of 4.4 ± 0.2 nm, respectively. Their excellent PL property, low cytotoxicity, and good aqueous dispersion offer promising applicability in PL staining and cell imaging. Meanwhile, the as-obtained byproduct containing the nanosheets could be used as an effective electromagnetic wave (EMW) absorber. The minimum reflection loss (RL) value was −54.13 dB at the thickness of 3.3 mm. The corresponding bandwidth with efficient attenuation (<−10 dB) was up to 7.04 GHz (8.8–15.84 GHz). The as-obtained EMW performance was far superior over most previously reported MoS₂-based nanomaterials. Full article

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11 pages, 2395 KiB

Open AccessArticle

Influences of Ga Doping on Crystal Structure and Polarimetric Pattern of SHG in ZnO Nanofilms

by Hua Long, Ammar Ayesh Habeeb, Dickson Mwenda Kinyua, Kai Wang, Bing Wang and Peixiang Lu

Nanomaterials 2019, 9(6), 905; https://doi.org/10.3390/nano9060905 - 21 Jun 2019

Cited by 8 | Viewed by 3936

Abstract

The second-harmonic generation (SHG) in gallium doped ZnO (GZO) nanofilms was studied. The Ga doping in GZO nanofilms influenced the crystal structure of the films, which affected SHG characteristics of the nanofilms. In our experiments, a strong SHG response was obtained in GZO [...] Read more.

The second-harmonic generation (SHG) in gallium doped ZnO (GZO) nanofilms was studied. The Ga doping in GZO nanofilms influenced the crystal structure of the films, which affected SHG characteristics of the nanofilms. In our experiments, a strong SHG response was obtained in GZO nanofilms, which was excited by 790 nm femtosecond laser. It was observed that the Ga doping concentrations affected, not only the intensity, but also the polarimetric pattern of SHG in GZO nanofilms. For 5.0% doped GZO films, the SHG intensity increased about 70%. The intensity ratio of SHG between the incident light polarization angle of 90° and 0°changed with the Ga doping concentrations. It showed the most significant increase for 7.3% doped GZO films, with an increased ratio of c/a crystal constants. This result was attributed to the differences of the ratios of d₃₃/d₃₁ (the second-order nonlinear susceptibility components) induced by the crystal distortion. The results are helpful to investigate nanofilms doping levels and crystal distortion by SHG microscopy, which is a non-destructive and sensitive method. Full article

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

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12 pages, 4477 KiB

Open AccessArticle

Optoelectronic and Electrothermal Properties of Transparent Conductive Silver Nanowires Films

by Yuehui Wang, Dexi Du, Xing Yang, Xianfeng Zhang and Yuzhen Zhao

Nanomaterials 2019, 9(6), 904; https://doi.org/10.3390/nano9060904 - 21 Jun 2019

Cited by 27 | Viewed by 4497

Abstract

Silver nanowires (AgNWs) show promise for fabricating flexible transparent conductors owing to their excellent conductivity, high transparency, and good mechanical properties. Here, we present the fabrication of transparent films composed of AgNWs with diameters of 20–30 nm and lengths of 25–30 μm on [...] Read more.

Silver nanowires (AgNWs) show promise for fabricating flexible transparent conductors owing to their excellent conductivity, high transparency, and good mechanical properties. Here, we present the fabrication of transparent films composed of AgNWs with diameters of 20–30 nm and lengths of 25–30 μm on polyethylene terephthalate substrates and glass slides substrates using the Meyer rod method. We systematically investigated the films’ optoelectronic and electrothermal properties. The morphology remained intact when heated at 25–150 °C and the AgNWs film showed high conductivity (17.6–14.3 Ω∙sq⁻¹), excellent transmittance (93.9–91.8%) and low surface roughness values (11.2–14.7 nm). When used as a heater, the transparent AgNW conductive film showed rapid heating at low input voltages owing to a uniform heat distribution across the whole substrate surface. Additionally, the conductivity of the film decreased with increasing bending cycle numbers; however, the film still exhibited a good conductivity and heating performances after repeated bending. Full article

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13 pages, 5949 KiB

Open AccessArticle

Evolution of Hair Treatment and Care: Prospects of Nanotube-Based Formulations

by Ana Cláudia Santos, Abhishek Panchal, Naureen Rahman, Miguel Pereira-Silva, Irina Pereira, Francisco Veiga and Yuri Lvov

Nanomaterials 2019, 9(6), 903; https://doi.org/10.3390/nano9060903 - 21 Jun 2019

Cited by 46 | Viewed by 7239

Abstract

A new approach for hair treatment through coating with nanotubes loaded with drugs or dyes for coloring is suggested. This coating is produced by nanotube self-assembly, resulting in stable 2–3 µm thick layers. For medical treatment such formulations allow for sustained long-lasting drug [...] Read more.

A new approach for hair treatment through coating with nanotubes loaded with drugs or dyes for coloring is suggested. This coating is produced by nanotube self-assembly, resulting in stable 2–3 µm thick layers. For medical treatment such formulations allow for sustained long-lasting drug delivery directly on the hair surface, also enhanced in the cuticle openings. For coloring, this process allows avoiding a direct hair contact with dye encased inside the clay nanotubes and provides a possibility to load water insoluble dyes from an organic solvent, store the formulation for a long time in dried form, and then apply to hair as an aqueous nanotube suspension. The described technique works with human and other mammal hairs and halloysite nanoclay coating is resilient against multiple shampoo washing. The most promising, halloysite tubule clay, is a biocompatible natural material which may be loaded with basic red, blue, and yellow dyes for optimized hair color, and also with drugs (e.g., antilice care-permethrin) to enhance the treatment efficiency with sustained release. This functionalized nanotube coating may have applications in human medical and beauty formulations, as well as veterinary applications. Full article

(This article belongs to the Special Issue Nanotubes for Health, Environment and Cultural Heritages)

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18 pages, 3955 KiB

Open AccessArticle

Elucidating the Chemistry behind the Reduction of Graphene Oxide Using a Green Approach with Polydopamine

by Cláudia Silva, Frank Simon, Peter Friedel, Petra Pötschke and Cordelia Zimmerer

Nanomaterials 2019, 9(6), 902; https://doi.org/10.3390/nano9060902 - 21 Jun 2019

Cited by 46 | Viewed by 5207

Abstract

A new approach using X-ray photoelectron spectroscopy (XPS) was employed to give insight into the reduction of graphene oxide (GO) using a green approach with polydopamine (PDA). In this approach, the number of carbon atoms bonded to OH and to nitrogen in PDA [...] Read more.

A new approach using X-ray photoelectron spectroscopy (XPS) was employed to give insight into the reduction of graphene oxide (GO) using a green approach with polydopamine (PDA). In this approach, the number of carbon atoms bonded to OH and to nitrogen in PDA is considered and compared to the total intensity of the signal resulting from OH groups in polydopamine-reduced graphene oxide (PDA-GO) to show the reduction. For this purpose, GO and PDA-GO with different times of reduction were prepared and characterized by Raman Spectroscopy and XPS. The PDA layer was removed to prepare reduced graphene oxide (RGO) and the effect of all chemical treatments on the thermal and electrical properties of the materials was studied. The results show that the complete reduction of the OH groups in GO occurred after 180 min of reaction. It was also concluded that Raman spectroscopy is not well suited to determine if the reduction and restoration of the sp² structure occurred. Moreover, a significant change in the thermal stability was not observed with the chemical treatments. Finally, the electrical powder conductivity decreased after reduction with PDA, increasing again after its removal. Full article

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

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17 pages, 8412 KiB

Open AccessArticle

Removal of Phenolic Compounds from Water Using Copper Ferrite Nanosphere Composites as Fenton Catalysts

by Carlos Moreno-Castilla, María Victoria López-Ramón, María Ángeles Fontecha-Cámara, Miguel A. Álvarez and Lucía Mateus

Nanomaterials 2019, 9(6), 901; https://doi.org/10.3390/nano9060901 - 20 Jun 2019

Cited by 25 | Viewed by 5665

Abstract

Copper ferrites containing Cu⁺ ions can be highly active heterogeneous Fenton catalysts due to synergic effects between Fe and Cu ions. Therefore, a method of copper ferrite nanosphere (CFNS) synthesis was selected that also permits the formation of cuprite, obtaining a CFNS [...] Read more.

Copper ferrites containing Cu⁺ ions can be highly active heterogeneous Fenton catalysts due to synergic effects between Fe and Cu ions. Therefore, a method of copper ferrite nanosphere (CFNS) synthesis was selected that also permits the formation of cuprite, obtaining a CFNS composite that was subsequently calcined up to 400 °C. Composites were tested as Fenton catalysts in the mineralization of phenol (PHE), p-nitrophenol (PNP) and p-aminophenol (PAP). Catalysts were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and magnetic measurements. Degradation of all phenols was practically complete at 95% total organic carbon (TOC) removal. Catalytic activity increased in the order PHE < PNP < PAP and decreased when the calcination temperature was raised; this order depended on the electronic effects of the substituents of phenols. The as-prepared CFNS showed the highest catalytic activity due to the presence of cubic copper ferrite and cuprite. The Cu⁺ surface concentration decreased after calcination at 200 °C, diminishing the catalytic activity. Cuprite alone showed a lower activity than the CFNS composite and the homogeneous Fenton reaction had almost no influence on its overall activity. CFNS activity decreased with its reutilization due to the disappearance of the cuprite phase. Degradation pathways are proposed for the phenols. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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13 pages, 5383 KiB

Open AccessArticle

Heterostructured NiO/ZnO Nanorod Arrays with Significantly Enhanced H₂S Sensing Performance

by Dongyi Ao, Zhijie Li, Yongqing Fu, Yongliang Tang, Shengnan Yan and Xiaotao Zu

Nanomaterials 2019, 9(6), 900; https://doi.org/10.3390/nano9060900 - 20 Jun 2019

Cited by 47 | Viewed by 5194

Abstract

H₂S gas sensors were fabricated using p-n heterojunctions of NiO/ZnO, in which the ZnO nanorod arrays were wrapped with NiO nanosheets via a hydrothermal synthesis method. When the H₂S gas molecules were adsorbed and then oxidized on the ZnO [...] Read more.

H₂S gas sensors were fabricated using p-n heterojunctions of NiO/ZnO, in which the ZnO nanorod arrays were wrapped with NiO nanosheets via a hydrothermal synthesis method. When the H₂S gas molecules were adsorbed and then oxidized on the ZnO surfaces, the free electrons were released. The increase in the electron concentration on the ZnO boosts the transport speed of the electrons on both sides of the NiO/ZnO p-n junction, which significantly improved the sensing performance and selectivity for H₂S detection, if compared with sensors using the pure ZnO nanorod arrays. The response to 20 ppm of H₂S was 21.3 at 160 °C for the heterostructured NiO/ZnO sensor, and the limit of detection was 0.1 ppm. We found that when the sensor was exposed to H₂S at an operating temperature below 160 °C, the resistance of the sensor significantly decreased, indicating its n-type semiconductor nature, whereas when the operating temperature was above 160 °C, the resistance significantly increased, indicating its p-type semiconductor nature. The sensing mechanism of the NiO/ZnO heterostructured H₂S gas sensor was discussed in detail. Full article

(This article belongs to the Special Issue Gas Sensors and Semiconductor Nanotechnology)

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9 pages, 1378 KiB

Open AccessArticle

Increasing Silver Nanowire Network Stability through Small Molecule Passivation

by Alexandra Madeira, Marie Plissonneau, Laurent Servant, Irene A. Goldthorpe and Mona Tréguer-Delapierre

Nanomaterials 2019, 9(6), 899; https://doi.org/10.3390/nano9060899 - 20 Jun 2019

Cited by 30 | Viewed by 4289

Abstract

Silver nanowire (AgNW) transparent electrodes show promise as an alternative to indium tin oxide (ITO). However, these nanowire electrodes degrade in air, leading to significant resistance increases. We show that passivating the nanowire surfaces with small organic molecules of 11-mercaptoundecanoic acid (MUA) does [...] Read more.

Silver nanowire (AgNW) transparent electrodes show promise as an alternative to indium tin oxide (ITO). However, these nanowire electrodes degrade in air, leading to significant resistance increases. We show that passivating the nanowire surfaces with small organic molecules of 11-mercaptoundecanoic acid (MUA) does not affect electrode transparency contrary to typical passivation films, and is inexpensive and simple to deposit. The sheet resistance of a 32 nm diameter silver nanowire network coated with MUA increases by only 12% over 120 days when exposed to atmospheric conditions but kept in the dark. The increase is larger when exposed to daylight (588%), but is still nearly two orders of magnitude lower than the resistance increase of unpassivated networks. The difference between the experiments performed under daylight versus the dark exemplifies the importance of testing passivation materials under light exposure. Full article

(This article belongs to the Special Issue Nanoscale Surface Engineering)

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21 pages, 2902 KiB

Open AccessArticle

Corona Isolation Method Matters: Capillary Electrophoresis Mass Spectrometry Based Comparison of Protein Corona Compositions Following On-Particle versus In-Solution or In-Gel Digestion

by Klaus Faserl, Andrew J. Chetwynd, Iseult Lynch, James A. Thorn and Herbert H. Lindner

Nanomaterials 2019, 9(6), 898; https://doi.org/10.3390/nano9060898 - 20 Jun 2019

Cited by 42 | Viewed by 6712

Abstract

Increased understanding of the role of the nanomaterial protein corona in driving nanomaterial uptake into, and impacts on, cells and organisms, and the consequent need for characterization of the corona, has led to a flourishing of methods for isolation and analysis of the [...] Read more.

Increased understanding of the role of the nanomaterial protein corona in driving nanomaterial uptake into, and impacts on, cells and organisms, and the consequent need for characterization of the corona, has led to a flourishing of methods for isolation and analysis of the constituent proteins over the past decade. However, despite over 700 corona studies to date, very little is understood in terms of which methods provide the most precise and comprehensive characterization of the corona. With the increasing importance of the modeling of corona formation and its correlation with biological impacts, it is timely to properly characterize and validate the isolation approaches used to determine the protein corona. The current work introduces Capillary Electrophoresis with Electro Spray Ionization Mass Spectrometry (CESI-MS) as a novel method for protein corona characterizations and develops an on-particle tryptic digestion method, comparing peptide solubilization solutions and characterizing the recovery of proteins from the nanomaterial surface. The CESI-MS was compared to the gold standard nano-LC-MS for corona analysis and maintained a high degree of reproducibility, while increasing throughput by >3-fold. The on-particle digestion is compared to an in-solution digestion and an in-gel digestion of the protein corona. Interestingly, a range of different protein classes were found to be recovered to greater or lesser extents among the different methods. Apolipoproteins were detected at lower concentrations when a surfactant was used to solubilize peptides, whereas immunoglobulins in general have a high affinity for nanomaterials, and thus show lower recovery using on-particle digestion. The optimized on-particle digestion was validated using 6 nanomaterials and proved capable of recovering in excess of 97% of the protein corona. These are important factors to consider when designing corona studies and modeling corona formation and impacts, highlighting the significance of a comprehensive validation of nanomaterial corona analysis methods. Full article

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13 pages, 1306 KiB

Open AccessArticle

Laser-Fabricated Reduced Graphene Oxide Memristors

by Francisco J. Romero, Alejandro Toral-Lopez, Akiko Ohata, Diego P. Morales, Francisco G. Ruiz, Andres Godoy and Noel Rodriguez

Nanomaterials 2019, 9(6), 897; https://doi.org/10.3390/nano9060897 - 19 Jun 2019

Cited by 56 | Viewed by 10831

Abstract

Finding an inexpensive and scalable method for the mass production of memristors will be one of the key aspects for their implementation in end-user computing applications. Herein, we report pioneering research on the fabrication of laser-lithographed graphene oxide memristors. The devices have been [...] Read more.

Finding an inexpensive and scalable method for the mass production of memristors will be one of the key aspects for their implementation in end-user computing applications. Herein, we report pioneering research on the fabrication of laser-lithographed graphene oxide memristors. The devices have been surface-fabricated through a graphene oxide coating on a polyethylene terephthalate substrate followed by a localized laser-assisted photo-thermal partial reduction. When the laser fluence is appropriately tuned during the fabrication process, the devices present a characteristic pinched closed-loop in the current-voltage relation revealing the unique fingerprint of the memristive hysteresis. Combined structural and electrical experiments have been conducted to characterize the raw material and the devices that aim to establish a path for optimization. Electrical measurements have demonstrated a clear distinction between the resistive states, as well as stable memory performance, indicating the potential of laser-fabricated graphene oxide memristors in resistive switching applications. Full article

(This article belongs to the Special Issue Laser Induced Nanomaterials)

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15 pages, 3911 KiB

Open AccessArticle

Activated Carbons from Thermoplastic Precursors and Their Energy Storage Applications

by Hye-Min Lee, Kwan-Woo Kim, Young-Kwon Park, Kay-Hyeok An, Soo-Jin Park and Byung-Joo Kim

Nanomaterials 2019, 9(6), 896; https://doi.org/10.3390/nano9060896 - 19 Jun 2019

Cited by 11 | Viewed by 3874

Abstract

In this study, low-density polyethylene (LDPE)-derived activated carbons (PE-AC) were prepared as electrode materials for an electric double-layer capacitor (EDLC) by techniques of cross-linking, carbonization, and subsequent activation under various conditions. The surface morphologies and structural characteristics of the PE-AC were observed by [...] Read more.

In this study, low-density polyethylene (LDPE)-derived activated carbons (PE-AC) were prepared as electrode materials for an electric double-layer capacitor (EDLC) by techniques of cross-linking, carbonization, and subsequent activation under various conditions. The surface morphologies and structural characteristics of the PE-AC were observed by field-emission scanning electron microscope, Cs-corrected field-emission transmission electron microscope, and X-ray diffraction analysis, respectively. The nitrogen adsorption isotherm-desorption characteristics were confirmed by Brunauer–Emmett–Teller, nonlocal density functional theory, and Barrett–Joyner–Halenda equations at 77 K. The results showed that the specific surface area and total pore volume of the activated samples increased with increasing the activation time. The specific surface area, the total pore volume, and mesopore volume of the PE-AC were found to be increased finally to 1600 m²/g, 0.86 cm³/g, and 0.3 cm³/g, respectively. The PE-AC also exhibited a high mesopore volume ratio of 35%. This mesopore-rich characteristic of the activated carbon from the LDPE is considered to be originated from the cross-linking density and crystallinity of precursor polymer. The high specific surface area and mesopore volume of the PE-AC led to their excellent performance as EDLC electrodes, including a specific capacitance of 112 F/g. Full article

(This article belongs to the Special Issue Innovative Advanced Materials for Energy Storage and Beyond: Synthesis, Characterization and Applications)

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15 pages, 3682 KiB

Open AccessFeature PaperArticle

Quality Improvement of Few-Layers Defective Graphene from Biomass and Application for H₂ Generation

by Jinbao He, Aicha Anouar, Ana Primo and Hermenegildo García

Nanomaterials 2019, 9(6), 895; https://doi.org/10.3390/nano9060895 - 19 Jun 2019

Cited by 31 | Viewed by 3551

Abstract

Pyrolysis of filmogenic natural polymers gives rise to the formation of films of few-layers defective, undoped, and doped graphenes with low electrical conductivity (3000 to 5000 Ω/sq). For the sake of valorization of biomass wastes, it would be of interest to decrease the [...] Read more.

Pyrolysis of filmogenic natural polymers gives rise to the formation of films of few-layers defective, undoped, and doped graphenes with low electrical conductivity (3000 to 5000 Ω/sq). For the sake of valorization of biomass wastes, it would be of interest to decrease the density of structural defects in order to increase the conductivity of the resulting few-layers graphene samples. In the present study, analytical and spectroscopic evidence is provided showing that by performing the pyrolysis at the optimal temperature (1100 °C), under a low percentage of H₂, a significant decrease in the density of defects related to the presence of residual oxygen can be achieved. This improvement in the quality of the resulting few-layers defective graphene is reflected in a decrease by a factor of about 3 or 5 for alginic acid and chitosan, respectively, of the electrical resistance. Under optimal conditions, few-layers defective graphene films with a resistance of 1000 Ω /sq were achieved. The electrode made of high-quality graphene prepared at 1100 °C under Ar/H₂ achieved a H₂ production of 3.62 µmol with a positive applied bias of 1.1 V under LED illumination for 16 h. Full article

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22 pages, 8568 KiB

Open AccessArticle

Unveiling Signatures of Topological Phases in Open Kitaev Chains and Ladders

by Alfonso Maiellaro, Francesco Romeo, Carmine Antonio Perroni, Vittorio Cataudella and Roberta Citro

Nanomaterials 2019, 9(6), 894; https://doi.org/10.3390/nano9060894 - 18 Jun 2019

Cited by 17 | Viewed by 4433

Abstract

In this work, the general problem of the characterization of the topological phase of an open quantum system is addressed. In particular, we study the topological properties of Kitaev chains and ladders under the perturbing effect of a current flux injected into the [...] Read more.

In this work, the general problem of the characterization of the topological phase of an open quantum system is addressed. In particular, we study the topological properties of Kitaev chains and ladders under the perturbing effect of a current flux injected into the system using an external normal lead and derived from it via a superconducting electrode. After discussing the topological phase diagram of the isolated systems, using a scattering technique within the Bogoliubov–de Gennes formulation, we analyze the differential conductance properties of these topological devices as a function of all relevant model parameters. The relevant problem of implementing local spectroscopic measurements to characterize topological systems is also addressed by studying the system electrical response as a function of the position and the distance of the normal electrode (tip). The results show how the signatures of topological order affect the electrical response of the analyzed systems, a subset of which being robust also against the effects of a moderate amount of disorder. The analysis of the internal modes of the nanodevices demonstrates that topological protection can be lost when quantum states of an initially isolated topological system are hybridized with those of the external reservoirs. The conclusions of this work could be useful in understanding the topological phases of nanowire-based mesoscopic devices. Full article

(This article belongs to the Special Issue Emergent Quantum Phenomena in Low-Dimensional Heterostructures: From Theory to Devices)

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12 pages, 1596 KiB

Open AccessArticle

Density Gradient Selection of Colloidal Silver Nanotriangles for Assembling Dye-Particle Plasmophores

by Rui Oliveira-Silva, Mariana Sousa-Jerónimo, David Botequim, Nuno J. O. Silva, Duarte M. F. Prazeres and Pedro M. R. Paulo

Nanomaterials 2019, 9(6), 893; https://doi.org/10.3390/nano9060893 - 18 Jun 2019

Cited by 5 | Viewed by 4836

Abstract

A simple method based on sucrose density gradient centrifugation is proposed here for the fractionation of colloidal silver nanotriangles. This method afforded particle fractions with surface plasmon resonances, spanning from red to infrared spectral ranges that could be used to tune optical properties [...] Read more.

A simple method based on sucrose density gradient centrifugation is proposed here for the fractionation of colloidal silver nanotriangles. This method afforded particle fractions with surface plasmon resonances, spanning from red to infrared spectral ranges that could be used to tune optical properties for plasmonic applications. This feature was exemplified by selecting silver nanotriangle samples with spectral overlap with Atto-655 dye’s absorption and emission in order to assemble dye-particle plasmophores. The emission brightness of an individual plasmophore, as characterized by fluorescence correlation spectroscopy, is at least 1000-fold more intense than that of a single Atto-655 dye label, which renders them as promising platforms for the development of fluorescence-based nanosensors. Full article

(This article belongs to the Special Issue Fluorescence Nanoprobes: From Synthesis to Applications)

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14 pages, 3156 KiB

Open AccessArticle

Cu-Doped Porous Carbon Derived from Heavy Metal-Contaminated Sewage Sludge for High-Performance Supercapacitor Electrode Materials

by Zhouliang Tan, Feng Yu, Liu Liu, Xin Jia, Yin Lv, Long Chen, Yisheng Xu, Yulin Shi and Xuhong Guo

Nanomaterials 2019, 9(6), 892; https://doi.org/10.3390/nano9060892 - 17 Jun 2019

Cited by 15 | Viewed by 3931

Abstract

In this paper, we report a complete solution for enhanced sludge treatment involving the removal of toxic metal (Cu(II)) from waste waters, subsequent pyrolytic conversion of these sludge to Cu-doped porous carbon, and their application in energy storage systems. The morphology, composition, and [...] Read more.

In this paper, we report a complete solution for enhanced sludge treatment involving the removal of toxic metal (Cu(II)) from waste waters, subsequent pyrolytic conversion of these sludge to Cu-doped porous carbon, and their application in energy storage systems. The morphology, composition, and pore structure of the resultant Cu-doped porous carbon could be readily modulated by varying the flocculation capacity of Cu(II). The results demonstrated that it exhibited outstanding performance for supercapacitor electrode applications. The Cu(II) removal efficiency has been evaluated and compared to the possible energy benefits. The flocculant dosage up to 200 mg·L⁻¹ was an equilibrium point existing between environmental impact and energy, at which more than 99% Cu(II) removal efficiency was achieved, while the resulting annealed product showed a high specific capacity (389.9·F·g⁻¹ at 1·A·g⁻¹) and good cycling stability (4% loss after 2500 cycles) as an electrode material for supercapacitors. Full article

(This article belongs to the Special Issue Nanocomposites for Environmental and Energy Applications)

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16 pages, 1434 KiB

Open AccessArticle

Multisensory System Used for the Analysis of the Water in the Lower Area of River Danube

by Constantin Apetrei, Catalina Iticescu and Lucian Puiu Georgescu

Nanomaterials 2019, 9(6), 891; https://doi.org/10.3390/nano9060891 - 17 Jun 2019

Cited by 14 | Viewed by 3442

Abstract

The present paper describes the development of a multisensory system for the analysis of the natural water in the Danube, water collected in the neighboring area of Galati City. The multisensory system consists of a sensor array made up of six screen-printed sensors [...] Read more.

The present paper describes the development of a multisensory system for the analysis of the natural water in the Danube, water collected in the neighboring area of Galati City. The multisensory system consists of a sensor array made up of six screen-printed sensors based on electroactive compounds (Cobalt phthalocyanine, Meldola’s Blue, Prussian Blue) and nanomaterials (Multi-Walled Carbon Nanotubes, Multi-Walled Graphene, Gold Nanoparticles). The measurements with the sensors array were performed by using cyclic voltammetry. The cyclic voltammograms recorded in the Danube natural water show redox processes related to the electrochemical activity of the compounds in the water samples or of the electro-active compounds in the sensors detector element. These processes are strongly influenced by the composition and physico-chemical properties of the water samples, such as the ionic strength or the pH. The multivariate data analysis was performed by using the principal component analysis (PCA) and the discriminant factor analysis (DFA), the water samples being discriminated according to the collection point. In order to confirm the observed classes, the partial least squares discriminant analysis (PLS-DA) method was used. The classification of the samples according to the collection point could be made accurately and with very few errors. The correlations established between the voltammetric data and the results of the physico-chemical analyses by using the PLS1 method were very good, the correlation coefficients exceeding 0.9. Moreover, the predictive capacity of the multisensory system is very good, the differences between the measured and the predicted values being less than 3%. The multisensory system based on voltammetric sensors and on multivariate data analysis methods is a viable and useful tool for natural water analysis. Full article

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23 pages, 9060 KiB

Open AccessArticle

Preparation, Characterization and Adsorption Potential of Grainy Halloysite-CNT Composites for Anthracene Removal from Aqueous Solution

by Gabriela Kamińska, Mariusz Dudziak, Edyta Kudlek and Jolanta Bohdziewicz

Nanomaterials 2019, 9(6), 890; https://doi.org/10.3390/nano9060890 - 17 Jun 2019

Cited by 23 | Viewed by 4148

Abstract

Grainy Hal-CNT composites were prepared from powder halloysite nanoclay (Hal) and carbon nanotubes (CNTs). The effect of the amount and type of CNTs, as well as calcination temperature on morphology and properties of Hal-CNT composites and their adsorption capacity of anthracene (ANT), were [...] Read more.

Grainy Hal-CNT composites were prepared from powder halloysite nanoclay (Hal) and carbon nanotubes (CNTs). The effect of the amount and type of CNTs, as well as calcination temperature on morphology and properties of Hal-CNT composites and their adsorption capacity of anthracene (ANT), were studied. The surface topography of granules was heterogenous, with cracks and channels created during granulation of powder clay and CNTs. In FTIR, spectra were exhibited only in the bands arising from halloysite, due to its dominance in the granules. The increase in the heating temperature to 550 °C resulted in mesoporosity/macroporosity of the granules, the lowest specific surface area (SSA) and poorest adsorption potential. Overall, SSA of all Hal-CNT composites were higher than raw Hal, and by itself, heated halloysite. The larger amount of CNTs enhanced adsorption kinetics due to the more external adsorption sites. The equilibrium was established with the contact time of approximately 30 min for the sample Hal-SWCNT 85:15, while the samples with loading 96:4, it was 60–90 min. Adsorption isotherms for ANT showed L1 type, which is representative for the sorbents with limited adsorption capacity. The Langmuir model described the adsorption process, suggesting a monolayer covering. The sample Hal-SWCNT 85:15 exhibited the highest adsorption capacity of ANT, due to its highest SSA and microporous character. Full article

(This article belongs to the Special Issue Carbon-Based Nanostructures and Nanocomposites for Health and Environmental Applications)

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11 pages, 3113 KiB

Open AccessArticle

Influence of the Sulfur Content Catalyst on the Packing Density of Carbon Nanotube Forests

by Sook Young Moon, In Ji Kang, Seung Min Kim and Woo Sik Kim

Nanomaterials 2019, 9(6), 889; https://doi.org/10.3390/nano9060889 - 17 Jun 2019

Cited by 4 | Viewed by 3421

Abstract

For the fabrication of high-performance carbon nanotube (CNT) composites with practical applicability, the development of new methods for the controlled growth of high-aspect-ratio CNTs still constitutes a challenge. With the aim of gaining a deeper understanding of the catalytic CNT growth, in this [...] Read more.

For the fabrication of high-performance carbon nanotube (CNT) composites with practical applicability, the development of new methods for the controlled growth of high-aspect-ratio CNTs still constitutes a challenge. With the aim of gaining a deeper understanding of the catalytic CNT growth, in this study, the effect of the catalyst composition is investigated using different mixtures of Fe₂(SO₄)₃ and FeCl₂ as catalysts. The relationship between the catalyst chemical state and the growth behavior of CNT forests is demonstrated by evaluating the alignment, diameter, length, and areal density of the CNT forests. When the Fe₂(SO₄)₃ content is increased, the area density, the I_G/I_D ratio, and the crystallite size of the CNTs increase. Additionally, the obtained CNT forests exhibit good spinnability with increasing the sulfur content. Full article

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23 pages, 6462 KiB

Open AccessArticle

NanoTiO₂ Sunscreen Does Not Prevent Systemic Oxidative Stress Caused by UV Radiation and a Minor Amount of NanoTiO₂ is Absorbed in Humans

by Daniela Pelclova, Tomas Navratil, Tereza Kacerova, Blanka Zamostna, Zdenka Fenclova, Stepanka Vlckova and Petr Kacer

Nanomaterials 2019, 9(6), 888; https://doi.org/10.3390/nano9060888 - 17 Jun 2019

Cited by 36 | Viewed by 6897

Abstract

The present pilot study tested the efficiency of nanoTiO₂ sunscreen to prevent the oxidative stress/inflammation caused by ultraviolet (UV) radiation using biomarkers in subjects’ blood, urine, and exhaled breath condensate (EBC). In addition, the skin absorption of nanoTiO₂ was studied. Six [...] Read more.

The present pilot study tested the efficiency of nanoTiO₂ sunscreen to prevent the oxidative stress/inflammation caused by ultraviolet (UV) radiation using biomarkers in subjects’ blood, urine, and exhaled breath condensate (EBC). In addition, the skin absorption of nanoTiO₂ was studied. Six identical subjects participated in three tests: (A) nanoTiO₂ sunscreen, (B) UV radiation, and (C) sunscreen + UV. The first samples were collected before the test and the second after sunscreen application and/or UV exposure. On day 4, the third samples were collected, and the sunscreen was washed off, and the fourth samples were collected on day 11. The following biomarkers were measured: malondialdehyde, 4-hydroxy-trans-hexenal, 4-hydroxy-trans-nonenal, aldehydes C6-C12, 8-iso-Prostaglandin F2α, o-tyrosine, 3-chlorotyrosine, 3-nitrotyrosine, 8-hydroxy-2-deoxyguanosine, 8-hydroxyguanosine, 5-hydroxymethyl uracil, and leukotrienes, using liquid chromatography-electrospray ionisation-tandem mass spectrometry. Titania was measured using inductively coupled plasma mass spectrometry and TiO₂ nanoparticles by transmission and scanning electron microscopy. Sunscreen alone did not elevate the markers, but UV increased the biomarkers in the plasma, urine, and EBC. The sunscreen prevented skin redness, however it did not inhibit the elevation of oxidative stress/inflammatory markers. Titania and nanoTiO₂ particles were found in the plasma and urine (but not in the EBC) in all sunscreen users, suggesting their skin absorption. Full article

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15 pages, 2306 KiB

Open AccessArticle

Characterizing the Cellular Response to Nitrogen-Doped Carbon Nanocups

by Amber S. Griffith, Thomas D. Zhang, Seth C. Burkert, Zelal Adiguzel, Ceyda Acilan, Alexander Star and William S. Saunders

Nanomaterials 2019, 9(6), 887; https://doi.org/10.3390/nano9060887 - 16 Jun 2019

Cited by 4 | Viewed by 5062

Abstract

Carbon nanomaterials, specifically, carbon nanotubes (CNTs) have many potential applications in biology and medicine. Currently, this material has not reached its full potential for application due to the potential toxicity to mammalian cells, and the incomplete understanding of how CNTs interface with cells. [...] Read more.

Carbon nanomaterials, specifically, carbon nanotubes (CNTs) have many potential applications in biology and medicine. Currently, this material has not reached its full potential for application due to the potential toxicity to mammalian cells, and the incomplete understanding of how CNTs interface with cells. The chemical composition and structural features of CNTs have been shown to directly affect their biological compatibility. The incorporation of nitrogen dopants to the graphitic lattice of CNTs results in a unique cup shaped morphology and minimal cytotoxicity in comparison to its undoped counterpart. In this study, we investigate how uniquely shaped nitrogen-doped carbon nanocups (NCNCs) interface with HeLa cells, a cervical cancer epithelial cultured cell line, and RPE-1 cells, an immortalized cultured epithelial cell line. We determined that NCNCs do not elicit a cytotoxic response in cells, and that they are uptaken via endocytosis. We have conjugated fluorescently tagged antibodies to NCNCs and shown that the protein-conjugated material is also capable of entering cells. This primes NCNCs to be a good candidate for subsequent protein modifications and applications in biological systems. Full article

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9 pages, 11963 KiB

Open AccessCommunication

PMMA-ITO Composite Formation via Electrostatic Assembly Method for Infra-Red Filtering

by Wai Kian Tan, Atsushi Yokoi, Go Kawamura, Atsunori Matsuda and Hiroyuki Muto

Nanomaterials 2019, 9(6), 886; https://doi.org/10.3390/nano9060886 - 14 Jun 2019

Cited by 23 | Viewed by 4794

Abstract

Formation of functional composite materials with desired properties is important for advanced application development. However, formation of a homogenous composite material via conventional mixing methods still remains a challenge due to agglomeration. Therefore, this work reports and demonstrates the formation of a homogeneous [...] Read more.

Formation of functional composite materials with desired properties is important for advanced application development. However, formation of a homogenous composite material via conventional mixing methods still remains a challenge due to agglomeration. Therefore, this work reports and demonstrates the formation of a homogeneous poly(methylmethacrylate) (PMMA)-indium tin oxide (ITO) composite with high visible light transparency (up to 90%) with an excellent shielding effect of infra-red (IR) via a facile electrostatic assembly method. This PMMA-ITO composite with good transparency and an IR shielding effect has good potential to be used in the automobile industry for vehicle windscreens as well as in heat preservation or preventive technology. The IR shielding rate is demonstrated to be controllable by changing the amount of ITO nanoparticles additive. This finding would provide a platform for development of IR optical related polymeric composite materials. Full article

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16 pages, 1732 KiB

Open AccessArticle

Soliton Fractional Charges in Graphene Nanoribbon and Polyacetylene: Similarities and Differences

by S.-R. Eric Yang

Nanomaterials 2019, 9(6), 885; https://doi.org/10.3390/nano9060885 - 14 Jun 2019

Cited by 19 | Viewed by 4701

Abstract

An introductory overview of current research developments regarding solitons and fractional boundary charges in graphene nanoribbons is presented. Graphene nanoribbons and polyacetylene have chiral symmetry and share numerous similar properties, e.g., the bulk-edge correspondence between the Zak phase and the existence of edge [...] Read more.

An introductory overview of current research developments regarding solitons and fractional boundary charges in graphene nanoribbons is presented. Graphene nanoribbons and polyacetylene have chiral symmetry and share numerous similar properties, e.g., the bulk-edge correspondence between the Zak phase and the existence of edge states, along with the presence of chiral boundary states, which are important for charge fractionalization. In polyacetylene, a fermion mass potential in the Dirac equation produces an excitation gap, and a twist in this scalar potential produces a zero-energy chiral soliton. Similarly, in a gapful armchair graphene nanoribbon, a distortion in the chiral gauge field can produce soliton states. In polyacetylene, a soliton is bound to a domain wall connecting two different dimerized phases. In graphene nanoribbons, a domain-wall soliton connects two topological zigzag edges with different chiralities. However, such a soliton does not display spin-charge separation. The existence of a soliton in finite-length polyacetylene can induce formation of fractional charges on the opposite ends. In contrast, for gapful graphene nanoribbons, the antiferromagnetic coupling between the opposite zigzag edges induces integer boundary charges. The presence of disorder in graphene nanoribbons partly mitigates antiferromagnetic coupling effect. Hence, the average edge charge of gap states with energies within a small interval is

e / 2

, with significant charge fluctuations. However, midgap states exhibit a well-defined charge fractionalization between the opposite zigzag edges in the weak-disorder regime. Numerous occupied soliton states in a disorder-free and doped zigzag graphene nanoribbon form a solitonic phase. Full article

(This article belongs to the Special Issue Nanotechnologies and Nanomaterials: Selected Papers from CCMR 2019)

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19 pages, 774 KiB

Open AccessFeature PaperReview

Ocular Drug Delivery: A Special Focus on the Thermosensitive Approach

by Simona Sapino, Daniela Chirio, Elena Peira, Elena Abellán Rubio, Valentina Brunella, Sushilkumar A. Jadhav, Giulia Chindamo and Marina Gallarate

Nanomaterials 2019, 9(6), 884; https://doi.org/10.3390/nano9060884 - 14 Jun 2019

Cited by 43 | Viewed by 6348

Abstract

The bioavailability of ophthalmic therapeutics is reduced because of the presence of physiological barriers whose primary function is to hinder the entry of exogenous agents, therefore also decreasing the bioavailability of locally administered drugs. Consequently, repeated ocular administrations are required. Hence, the development [...] Read more.

The bioavailability of ophthalmic therapeutics is reduced because of the presence of physiological barriers whose primary function is to hinder the entry of exogenous agents, therefore also decreasing the bioavailability of locally administered drugs. Consequently, repeated ocular administrations are required. Hence, the development of drug delivery systems that ensure suitable drug concentration for prolonged times in different ocular tissues is certainly of great importance. This objective can be partially achieved using thermosensitive drug delivery systems that, owing to their ability of changing their state in response to temperature variations, from room to body temperature, may increase drug bioavailability. In the case of topical instillation, in situ forming gels increase pre-corneal drug residence time as a consequence of their enhanced adhesion to the corneal surface. Otherwise, in the case of intraocular and periocular, i.e., subconjunctival, retrobulbar, peribulbar administration, among others, they have the undoubted advantage of being easily injectable and, owing to their sudden thickening at body temperature, have the ability to form an in situ drug reservoir. As a result, the frequency of administration can be reduced, also favoring the patient’s adhesion to therapy. In the main section of this review, we discuss some of the most common treatment options for ocular diseases, with a special focus on posterior segment treatments, and summarize the most recent improvement deriving from thermosensitive drug delivery strategies. Aside from this, an additional section describes the most widespread in vitro models employed to evaluate the functionality of novel ophthalmic drug delivery systems. Full article

(This article belongs to the Special Issue Advanced Nanosystems for Ophthalmic Administration)

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11 pages, 1869 KiB

Open AccessArticle

Ethanol-Quenching Introduced Oxygen Vacancies in Strontium Titanate Surface and the Enhanced Photocatalytic Activity

by Yang Xiao, Shihao Chen, Yinhai Wang, Zhengfa Hu, Hui Zhao and Wei Xie

Nanomaterials 2019, 9(6), 883; https://doi.org/10.3390/nano9060883 - 14 Jun 2019

Cited by 6 | Viewed by 3428

Abstract

Modification of the surface properties of SrTiO₃ crystals by regulating the reaction environment in order to improve the photocatalytic activity has been widely studied. However, the development of a facile, effective, and universal method to improve the photocatalytic activity of these crystals [...] Read more.

Modification of the surface properties of SrTiO₃ crystals by regulating the reaction environment in order to improve the photocatalytic activity has been widely studied. However, the development of a facile, effective, and universal method to improve the photocatalytic activity of these crystals remains an enormous challenge. We have developed a simple method to modify the surface environment of SrTiO₃ by ethanol quenching, which results in enhanced UV, visible and infrared light absorption and photocatalytic performance. The SrTiO₃ nanocrystals were preheated to 800 °C and immediately quenched by submersion in ethanol. X-ray diffraction patterns, electron paramagnetic resonance spectra, and X-ray photoelectron spectra indicated that upon rapid ethanol quenching, the interaction between hot SrTiO₃ and ethanol led to the introduction of a high concentration of oxygen vacancies on the surface of the SrTiO₃ lattice. Consequently, to maintain the regional charge balance of SrTiO₃, Sr²⁺ could be substituted for Ti⁴⁺. Moreover, oxygen vacancies induced localized states into the band gap of the modified SrTiO₃ and acted as photoinduced charge traps, thus promoting the photocatalytic activity. The improved photocatalytic performance of the modified SrTiO₃ was demonstrated by using it for the decomposition of rhodamine B and production of H₂ from water under visible or solar light. Full article

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