Nanomaterials

14 pages, 3886 KiB

Open AccessArticle

Synthesis of Au@Pt Core—Shell Nanoparticles as Efficient Electrocatalyst for Methanol Electro-Oxidation

by América Higareda, Siva Kumar-Krishnan, Amado F. García-Ruiz, José Maya-Cornejo, José L. Lopez-Miranda, Daniel Bahena, Gerardo Rosas, Ramiro Pérez and Rodrigo Esparza

Nanomaterials 2019, 9(11), 1644; https://doi.org/10.3390/nano9111644 - 19 Nov 2019

Cited by 24 | Viewed by 6671

Abstract

Bimetallic Au@Pt nanoparticles (NPs) with Pt monolayer shell are of much interest for applications in heterogeneous catalysts because of enhanced catalytic activity and very low Pt-utilization. However, precisely controlled synthesis with uniform Pt-monolayers and stability on the AuNPs seeds remain elusive. Herein, we [...] Read more.

Bimetallic Au@Pt nanoparticles (NPs) with Pt monolayer shell are of much interest for applications in heterogeneous catalysts because of enhanced catalytic activity and very low Pt-utilization. However, precisely controlled synthesis with uniform Pt-monolayers and stability on the AuNPs seeds remain elusive. Herein, we report the controlled deposition of Pt-monolayer onto uniform AuNPs seeds to obtain Au@Pt core–shell NPs and their Pt-coverage dependent electrocatalytic activity for methanol electro-oxidation. The atomic ratio between Au/Pt was effectively tuned by varying the precursor solution ratio in the reaction solution. The morphology and atomic structure of the Au@Pt NPs were analyzed by high-resolution scanning transmission electron microcopy (HR-STEM) and X-ray diffraction (XRD) techniques. The results demonstrated that the Au@Pt core–shell NPs with Pt-shell thickness (atomic ratio 1:2) exhibit higher electrocatalytic activity for methanol electro-oxidation reaction, whereas higher and lower Pt ratios showed less overall catalytic performance. Such higher catalytic performance of Au@Pt NPs (1:2) can be attributed to the weakened CO binding on the Pt/monolayers surface. Our present synthesis strategy and optimization of the catalytic activity of Au@Pt core–shell NPs catalysts provide promising approach to rationally design highly active catalysts with less Pt-usage for high performance electrocatalysts for applications in fuel cells. Full article

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(a) UV–vis absorption spectra and (b) fourth-derivative absorption spectra of the obtained Au, Pt and Au@Pt NPs with different nominal compositions. The inset in <a href="#nanomaterials-09-01644-f001" class="html-fig">Figure 1</a>a shows a photograph of the corresponding samples. Full article ">Figure 2
(a) XRD patterns of Au@Pt NPs with (1:1), (1:2), and (1:3) composition;(b) (111) reflections of Au and Pt structures; and (c) elemental composition of Au and Pt. Full article ">Figure 3
BF-STEM images, size distribution histograms and EDS spectrum of Au@Pt NPs supported on carbon black Vulcan XC-72R with different nominal atomic compositions: (a) (1:1), (b) (1:2), and (c) (1:3). Full article ">Figure 4
High-resolution HAADF-STEM images with their FFT of (a) AuNPs and(b) Au@Pt (1:3) NPs, and SAED patterns of (c) AuNPs and (d) AuPt (1:3) NPs. Full article ">Figure 5
(a) HAADF-STEM image, (b) EDS line-scan profile of Au@Pt (1:1) NPs, (c) HAADF-STEM image, (d) EDS line-scan profile, and (e) EDS elemental mappings of Au@Pt (1:3) NPs. Green represents Au component and red represents Pt component. Full article ">Figure 6
Voltammograms (CVs) of carbon supported Au@Pt/C NPs catalysts with different nominal compositions and Pt/C commercial in a 0.3 M aqueous solution of KOH at a scan rate of 50 mVs−1. Full article ">Figure 7
CV profiles of the catalysts for methanol oxidation reaction. CV curves for (a) Au@Pt/C NPs with different nominal compositions and (b) commercial Pt/C electrocatalysts and Au@Pt/C (1:2) NPs in 0.3 M KOH + 1 M MeOH mixed solution at a sweep rate of 20 mVs−1. Full article ">

15 pages, 3577 KiB

Open AccessArticle

Enhanced Visible-Light Photocatalytic Activity of Ag QDs Anchored on CeO₂ Nanosheets with a Carbon Coating

by Xiaogang Zheng, Qian Chen, Sihao Lv, Xiaojin Fu, Jing Wen and Xinhui Liu

Nanomaterials 2019, 9(11), 1643; https://doi.org/10.3390/nano9111643 - 19 Nov 2019

Cited by 29 | Viewed by 3874

Abstract

Ag quantum dots (QDs) anchored on CeO₂ nanosheets with a carbon coating (Ag/CeO₂@C) (composites) were prepared via an in situ reduction approach for the photocatalytic degradation of Cr(VI) and tetracycline hydrochloride (TCH) in the visible-light region. The photocatalytic activity of [...] Read more.

Ag quantum dots (QDs) anchored on CeO₂ nanosheets with a carbon coating (Ag/CeO₂@C) (composites) were prepared via an in situ reduction approach for the photocatalytic degradation of Cr(VI) and tetracycline hydrochloride (TCH) in the visible-light region. The photocatalytic activity of Ag/CeO₂@C was greatly affected by carbon content, Ag-doping content, Cr(VI) concentration, pH value, and inorganic ions. Enhanced photocatalytic activity was obtained by Ag/CeO₂@C (compared to CeO₂ and CeO₂@C), of which 3-Ag/CeO₂@C-2 with an Ag-doping content of 5.41% presented the best removal efficiency and the most superior stability after five cycles. ·O₂⁻ and ·OH radicals were crucial for the photocatalytic capacity of 3-Ag/CeO₂@C-2. The combined effect of the surface plasma resonance (SPR) of Ag QDs, an electron trapper of carbon shells, and the redox activity of the Ce(III)/Ce(IV) coupling induced efficient charge transfer and separation, suppressing the recombination of electron–hole pairs. Full article

(This article belongs to the Special Issue Photocatalytic Nanomaterials)

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10 pages, 1545 KiB

Open AccessCommunication

Methane-Mediated Vapor Transport Growth of Monolayer WSe₂ Crystals

by Hyeon-Sik Jang, Jae-Young Lim, Seog-Gyun Kang, Sang-Hwa Hyun, Sana Sandhu, Seok-Kyun Son, Jae-Hyun Lee and Dongmok Whang

Nanomaterials 2019, 9(11), 1642; https://doi.org/10.3390/nano9111642 - 19 Nov 2019

Cited by 5 | Viewed by 4743

Abstract

The electrical and optical properties of semiconducting transition metal dichalcogenides (TMDs) can be tuned by controlling their composition and the number of layers they have. Among various TMDs, the monolayer WSe₂ has a direct bandgap of 1.65 eV and exhibits p-type or [...] Read more.

The electrical and optical properties of semiconducting transition metal dichalcogenides (TMDs) can be tuned by controlling their composition and the number of layers they have. Among various TMDs, the monolayer WSe₂ has a direct bandgap of 1.65 eV and exhibits p-type or bipolar behavior, depending on the type of contact metal. Despite these promising properties, a lack of efficient large-area production methods for high-quality, uniform WSe₂ hinders its practical device applications. Various methods have been investigated for the synthesis of large-area monolayer WSe₂, but the difficulty of precisely controlling solid-state TMD precursors (WO₃, MoO₃, Se, and S powders) is a major obstacle to the synthesis of uniform TMD layers. In this work, we outline our success in growing large-area, high-quality, monolayered WSe₂ by utilizing methane (CH₄) gas with precisely controlled pressure as a promoter. When compared to the catalytic growth of monolayered WSe₂ without a gas-phase promoter, the catalytic growth of the monolayered WSe₂ with a CH₄ promoter reduced the nucleation density to 1/1000 and increased the grain size of monolayer WSe₂ up to 100 ?m. The significant improvement in the optical properties of the resulting WSe₂ indicates that CH₄ is a suitable candidate as a promoter for the synthesis of TMD materials, because it allows accurate gas control. Full article

(This article belongs to the Section Nanocomposite Materials)

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The schematic illustration of methane-mediated WSe2 synthesis. (a) Sketch of homemade tube-type chemical vapor deposition (CVD) setup. (b) Schematic image of WSe2 crystal growth by vapor-solid transport mechanism and its growth morphology difference between (c) without and (d) with methane (CH4) gas. Full article ">Figure 2
Size control of the WSe2 domain by tuning the methane carrier gas ratio. Typical SEM images of WSe2 grains synthesized on a SiO2/Si substrate with a flow of (a) CH4:Ar = 0:200, (b) CH4:Ar = 50:150, (c) CH4:Ar = 100:100, and (d) CH4:Ar = 150:50 sccm. (e) Edge length (black) and nucleation density (blue) of WSe2 domains as a function of the CH4 gas ratio. The error bars represent the edge length variations of WSe2 domains obtained at the same CH4 gas flow. Full article ">Figure 3
Raman and photoluminescence (PL) investigation of the synthesized WSe2 according to the catalytic effects of methane. Raman mapping results of (a) CH4:Ar = 150:50 sccm, (b) Ar gas only as carrier gas, and (c) representative Raman spectrum of each mapping result. PL mapping results of (d) CH4:Ar = 150:50 sccm, (e) Ar gas only as carrier gas, And (f) representative PL spectrum of each mapping result. Raman and PL results were obtained from a micro-Raman instrument with a wavelength of 532 nm laser. Inset is an OM image corresponding to each mapping region. Full article ">Figure 4
(a) Atomice force microscopy (AFM) image of the synthesized monolayer WSe2. The inset graph is the height profile corresponding to the blue dot line. (b) Surface potential mapping image of WSe2 by Kelvin probe force microscopy (KPFM). The inset graph is the surface potential profile corresponding to the white dot line. X-ray photoelectron spectroscopy (XPS) analysis of (c) W-4f and (d) Se-3d of synthesized WSe2. Full article ">

13 pages, 4057 KiB

Open AccessArticle

Antireflection Enhancement by Composite Nanoporous Zeolite 3A–Carbon Thin Film

by Maksym Stetsenko, Salvatore A. Pullano, Tetiana Margitych, Lidia Maksimenko, Ali Hassan, Serhii Kryvyi, Rui Hu, Chun Huang, Roman Ziniuk, Sergii Golovynskyi, Ivan Babichuk, Βaikui Li, Junle Qu and Antonino S. Fiorillo

Nanomaterials 2019, 9(11), 1641; https://doi.org/10.3390/nano9111641 - 19 Nov 2019

Cited by 15 | Viewed by 3771

Abstract

A straightforward and effective spin-coating technique at 120 °C was investigated for the deposition of a thin nanoporous layer with antireflection properties onto glass and indium tin oxide (ITO) coated glass. A mixture of zeolite 3A powder and high iodine value vegetable oil [...] Read more.

A straightforward and effective spin-coating technique at 120 °C was investigated for the deposition of a thin nanoporous layer with antireflection properties onto glass and indium tin oxide (ITO) coated glass. A mixture of zeolite 3A powder and high iodine value vegetable oil was deposited, creating a carbonic paste with embedded nanoporous grains. Experimental results evidenced excellent broadband antireflection over the visible-near-infrared wavelength range (450–850 nm), with a diffuse reflectance value of 1.67% and 1.79%. Structural and optical characteristics stabilized over time. The results are promising for the accessible and cost-effective fabrication of an antireflective surface for optoelectronic devices. Full article

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(a) Stages of the zeolite 3A deposition onto substrates. SEM surface morphologies for the samples deposited on (b) glass (scale bar 50 μm) and (c) ITO/glass (scale bar 10 μm). Full article ">Figure 2
XRD patterns of (a) the ITO/glass, (b) zeolite/glass, and (c) zeolite/ITO/glass samples along with (d) an SEM cross-section of the zeolite/glass. Full article ">Figure 3
Raman spectra of the zeolite 3A—carbon layers (λEx = 532.5 nm): (a) laser power of 45 mW, (b) laser power—15 mW. Full article ">Figure 4
Spectra of (a) specular and diffuse reflectance and (b) extinction for the glass, nanofilms ITO, zeolite/glass, and zeolite/ITO/glass. Full article ">Figure 5
Polarization spectral characteristics of the zeolite 3A–carbon coatings: (a) amplitude and (b) phase anisotropy. Full article ">Figure 6
Excitation–emission two-dimensional plots for the zeolite 3A–carbon layers on glass and ITO/glass. Full article ">Figure 7
Fluorescence microscopy images of the zeolite/glass and zeolite/ITO/glass under blue (a), green (b) and UV excitations (c,d). The images (a–c) were obtained through the band-pass filters of different wavelengths; the images (d) were captured within visible range (scale bar—100μm). Full article ">Figure 8
Fluorescence decays of (a) the zeolite/glass and (b) zeolite/ITO/glass (λEx = 370 nm, λEm = 470 nm). Full article ">

9 pages, 1268 KiB

Open AccessArticle

Direct Observation of Monolayer MoS₂ Prepared by CVD Using In-Situ Differential Reflectance Spectroscopy

by Yina Wang, Lei Zhang, Chenhui Su, Hang Xiao, Shanshan Lv, Faye Zhang, Qingmei Sui, Lei Jia and Mingshun Jiang

Nanomaterials 2019, 9(11), 1640; https://doi.org/10.3390/nano9111640 - 19 Nov 2019

Cited by 22 | Viewed by 5286

Abstract

The in-situ observation is of great significance to the study of the growth mechanism and controllability of two-dimensional transition metal dichalcogenides (TMDCs). Here, the differential reflectance spectroscopy (DRS) was performed to monitor the growth of molybdenum disulfide (MoS₂) on a SiO [...] Read more.

The in-situ observation is of great significance to the study of the growth mechanism and controllability of two-dimensional transition metal dichalcogenides (TMDCs). Here, the differential reflectance spectroscopy (DRS) was performed to monitor the growth of molybdenum disulfide (MoS₂) on a SiO₂/Si substrate prepared by chemical vapor deposition (CVD). A home-built in-situ DRS setup was applied to monitor the growth of MoS₂ in-situ. The formation and evolution of monolayer MoS₂ are revealed by differential reflectance (DR) spectra. The morphology, vibration mode, absorption characteristics and thickness of monolayer MoS₂ have been confirmed by optical microscopy, Raman spectroscopy, ex-situ DR spectra, and atomic force microscopy (AFM) respectively. The results demonstrated that DRS was a powerful tool for in-situ observations and has great potential for growth mechanism and controllability of TMDCs prepared by CVD. To the best of the authors’ knowledge, it was the first report in which the CVD growth of two-dimensional TMDCs has been investigated in-situ by reflectance spectroscopy. Full article

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Scheme of the in-situ experiment device. Full article ">Figure 2
(a) Optical images of MoS2 thin films (front) and independent triangular crystals (back) on two different regions of the same SiO2/Si substrate; (b) Raman spectra of MoS2 films and independent triangular crystals; (c) Ex-situ differential reflectance spectroscopy (DRS) obtained on an optical platform at room temperature; (d) The height profile of MoS2. The inset shows an atomic force microscopy (AFM) image. The black solid line is the measurement route of a probe. The darker region is the area without MoS2, which marked with white dashed lines. Full article ">Figure 3
(a) The temperature curves of temperature-zone І (black line) and ІІ (red line) during the chemical vapor deposition (CVD) growth, respectively. The preparation process is divided into the stage І, stage ІІ, and stage ІІІ. (b) In-situ differential reflectance (DR) spectra recorded in the stage ІІ during CVD preparation of monolayer MoS2 on a SiO2/Si substrate. The time interval between successive spectra is 120 s. The black arrow indicates the direction of spectral change at 1.83 eV. (c) In-situ DR spectra recorded in the stage ІІІ. The temperature interval is 40 °C and the temperature range is 730–50 °C. The black arrow indicates the direction of temperature reduction. (d) The increment of DR spectra during the stage ІІІ. (e) The intensities of DR signals at 1.83 eV and 1.99 eV as a function of time, respectively. Full article ">

8 pages, 3032 KiB

Open AccessArticle

Influence of Annealing Temperature on Weak-Cavity Top-Emission Red Quantum Dot Light Emitting Diode

by Chun-Yu Lee, Ya-Pei Kuo, Peng-Yu Chen, Hsieh-Hsing Lu and Ming Yi Lin

Nanomaterials 2019, 9(11), 1639; https://doi.org/10.3390/nano9111639 - 19 Nov 2019

Cited by 14 | Viewed by 4441

Abstract

In this report, we show that the annealing temperature in QDs/Mg-doped ZnO film plays a very important role in determining QLEDs performance. Measurements of capacitance and single carrier device reveal that the change of the device efficiency with different annealing temperatures is related [...] Read more.

In this report, we show that the annealing temperature in QDs/Mg-doped ZnO film plays a very important role in determining QLEDs performance. Measurements of capacitance and single carrier device reveal that the change of the device efficiency with different annealing temperatures is related to the balance of both electron and hole injection. A comparison of annealing temperatures shows that the best performance is demonstrated with 150 °C-annealing temperature. With the improved charge injection and charge balance, a maximum current efficiency of 24.81 cd/A and external quantum efficiency (EQE) of 20.09% are achievable in our red top-emission QLEDs with weak microcavity structure. Full article

(This article belongs to the Special Issue Quantum Dots and Micro-LED Display)

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10 pages, 3311 KiB

Open AccessArticle

V₃S₄ Nanosheets Anchored on N, S Co-Doped Graphene with Pseudocapacitive Effect for Fast and Durable Lithium Storage

by Naiteng Wu, Di Miao, Xinliang Zhou, Lilei Zhang, Guilong Liu, Donglei Guo and Xianming Liu

Nanomaterials 2019, 9(11), 1638; https://doi.org/10.3390/nano9111638 - 18 Nov 2019

Cited by 22 | Viewed by 3671

Abstract

Construction of a suitable hybrid structure has been considered an important approach to address the defects of metal sulfide anode materials. V₃S₄ nanosheets anchored on an N, S co-coped graphene (VS/NSG) aerogel were successfully fabricated by an efficient self-assembled strategy. [...] Read more.

Construction of a suitable hybrid structure has been considered an important approach to address the defects of metal sulfide anode materials. V₃S₄ nanosheets anchored on an N, S co-coped graphene (VS/NSG) aerogel were successfully fabricated by an efficient self-assembled strategy. During the heat treatment process, decomposition, sulfuration and N, S co-doping occurred. This hybrid structure was not only endowed with an enhanced capability to buffer the volume expansion, but also improved electron conductivity as a result of the conductive network that had been constructed. The dominating pseudocapacitive contribution (57.78% at 1 mV s⁻¹) enhanced the electrochemical performance effectively. When serving as anode material for lithium ion batteries, VS/NSG exhibits excellent lithium storage properties, including high rate capacity (480 and 330 mAh g⁻¹ at 5 and 10 A g⁻¹, respectively) and stable cyclic performance (692 mAh g⁻¹ after 400 cycles at 2 A g⁻¹). Full article

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(a) Schematic illustration of preparation process of VS/NSG; (b) XRD pattern of as-prepared VS/NSG; (c) the structure of V3S4 along the c-axis. Full article ">Figure 2
(a,b) SEM images of as-prepared VS/NSG at different magnifications; (c,d) TEM image, HRTEM image, and FFT patterns in the marked white box of VS/NSG. Full article ">Figure 3
XPS survey (a) V 2p, (b) S 2p, (c) N 1s, and (d) C 1s of as-prepared VS/NSG. Full article ">Figure 4
(a) The initial discharge–charge curves of VS/NSG at 0.05 A g−1; (b) CV curves of VS/NSG at a scan rate of 0.1 mV s−1; and (c) the cyclic stability and (d) rate capability of VS/NSG electrode. Full article ">Figure 5
Kinetic analyses of VS/NSG electrode. (a) CV curves at different scanning rates; (b) log(i) vs. log (v) plots at different peaks; (c) capacitive contribution (blue region) to the charge storage at 1 mV s−1; (d) the contribution ratio of pseudocapacitive and diffusion-controlled current at different scanning rates. Full article ">

13 pages, 3716 KiB

Open AccessArticle

DOPO-Functionalized Molybdenum Disulfide and its Impact on the Thermal Properties of Polyethylene and Poly(Lactic Acid) Composites

by Karolina Wenelska, Piotr Homa, Stefan Popovic, Klaudia Maslana and Ewa Mijowska

Nanomaterials 2019, 9(11), 1637; https://doi.org/10.3390/nano9111637 - 18 Nov 2019

Cited by 7 | Viewed by 2708

Abstract

The fabrication of conventional or biodegradable polymers with improved thermal and fire-resistant properties is an important task for their successful application in various branches of the industry. In this work, few-layered molybdenum disulfide was functionalized with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and introduced into polyethylene and poly(lactic [...] Read more.

The fabrication of conventional or biodegradable polymers with improved thermal and fire-resistant properties is an important task for their successful application in various branches of the industry. In this work, few-layered molybdenum disulfide was functionalized with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and introduced into polyethylene and poly(lactic acid) matrixes. The obtained polyethylene composite samples displayed improved thermal stability, significant reduction in CO emissions, improved fire-resistant properties, and over 100% increases in thermal conductivity. Poly(lactic acid) composites displayed less impressive results, but have managed to improve some values, such as CO emissions, peak heat release rate, and total heat release in comparison to pristine polymer. Full article

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Transmission electron microscopy (TEM) (A) and atomic force microscopy (AFM) (B) images, along with AFM height profiles (C) of few-layered MoS2. Full article ">Figure 2
Raman spectroscopy of bulk and few-layered MoS2. Full article ">Figure 3
TEM images of MoS2/Ni2O3 nanoparticles (A–C). Full article ">Figure 4
TEM (A–C) and SEM (D–F) images of MoS2/Ni2O3/DOPO nanoparticles. Full article ">Figure 5
TGA curves of PE (A) and PLA (B) composites compared to pristine polymers. Full article ">Figure 6
CO emissions of PE and PLA composites compared to pristine polymers. Full article ">Figure 7
Examples of heat release rate (HRR) curves obtained for PE (A) and PLA (B) composites compared to pristine polymers. Full article ">

10 pages, 2603 KiB

Open AccessArticle

One-Step Hydrothermal Synthesis of P25 @ Few Layered MoS₂ Nanosheets toward Enhanced Bi-catalytic Activities: Photocatalysis and Electrocatalysis

by Fang Zhou, Zhiguang Zhang, Zhihua Wang, Yajing Wang, Liping Xu, Qiang Wang and Wenjun Liu

Nanomaterials 2019, 9(11), 1636; https://doi.org/10.3390/nano9111636 - 18 Nov 2019

Cited by 8 | Viewed by 3123

Abstract

P25 loaded few layered molybdenum disulfide (MoS₂) nanosheets (P25@MoS₂) are successfully synthesized through a facile one-step hydrothermal process. The bi-catalytic activities, i.e., photocatalytic and electrocatalytic activities, of the as-prepared nanomaterials have been investigated. For the as-prepared products, the photocatalytic [...] Read more.

P25 loaded few layered molybdenum disulfide (MoS₂) nanosheets (P25@MoS₂) are successfully synthesized through a facile one-step hydrothermal process. The bi-catalytic activities, i.e., photocatalytic and electrocatalytic activities, of the as-prepared nanomaterials have been investigated. For the as-prepared products, the photocatalytic performances were investigated by degrading simulated pollutant under sunlight irradiation, and the hydrogen evolution reaction evaluated the electrocatalytic performances. The results indicate that P25@MoS₂ possesses excellent activities in both photocatalysis and electrocatalysis. The presence of MoS₂ broadens the light absorption range of P25 and improves the separation and transformation efficiency of photogenerated carriers, thus improving its photocatalytic performance. The existence of P25 inhibits the aggregation of MoS₂ to form more dispersed MoS₂ nanosheets with only few layers increasing its active sites. Thereby, the electrocatalytic performance is heightened. The excellent multifunction makes the as-prepared P25@MoS₂ a promising material in the fields of environment and energy. Full article

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X-ray diffraction (XRD) patterns of pure P25, PM21, PM11, PM12, and molybdenum disulfide (MoS2). Full article ">Figure 2
(a) Field emission scanning electron microscopy (FESEM) image of pure MoS2. (b) Low and (c) high magnification FESEM images of PM11 respectively. (d) Transmission electron microscope (TEM) image of PM11. (e,f) High resolution transmission electron microscope (HRTEM) images of PM11 corresponding to the selected areas in (d). Full article ">Figure 3
High-resolution X-ray photoelectron spectra (XPS) spectra of PM11: (a) Ti 2p, (b) O 1s, (c) Mo 3d, and (d) S 2p. Full article ">Figure 4
(a) UV-Vis diffuse reflectance spectra and (b) PL spectra of P25, MoS2, PM21, PM11, and PM12. Full article ">Figure 5
(a) The curves of C/C0 vs. time for photodegrading rhodamine B (RhB). (b) The degradation efficiency in recycling of PM11. Full article ">Figure 6
(a) Polarization curves and (b) corresponding Tafel plots. Full article ">

12 pages, 5522 KiB

Open AccessArticle

Synthesis of Mn_0.5Zn_0.5Sm_xEu_xFe_1.8?2xO₄ Nanoparticles via the Hydrothermal Approach Induced Anti-Cancer and Anti-Bacterial Activities

by Sultan Akhtar, Suriya Rehman, Munirah A. Almessiere, Firdos Alam Khan, Yassine Slimani and Abdulhadi Baykal

Nanomaterials 2019, 9(11), 1635; https://doi.org/10.3390/nano9111635 - 18 Nov 2019

Cited by 64 | Viewed by 4224

Abstract

Manganese metallic nanoparticles are attractive materials for various biological and medical applications. In the present study, we synthesized unique Mn_0.5Zn_0.5Sm_xEu_xFe_1.8−2xO₄ (0.01 ≤ x ≤ 0.05) nanoparticles (NPs) by using the hydrothermal approach. [...] Read more.

Manganese metallic nanoparticles are attractive materials for various biological and medical applications. In the present study, we synthesized unique Mn_0.5Zn_0.5Sm_xEu_xFe_1.8−2xO₄ (0.01 ≤ x ≤ 0.05) nanoparticles (NPs) by using the hydrothermal approach. The structure and surface morphology of the products were determined by X-ray powder diffraction (XRD), transmission electron and scanning electron microcopies (TEM and SEM), along with energy dispersive X-ray spectroscopy (EDX). We evaluated the impact of Mn_0.5Zn_0.5Sm_xEu_xFe_1.8−2xO₄ NPs on both human embryonic stem cells (HEK-293) (normal cells) and human colon carcinoma cells (HCT-116) (cancerous cells). We found that post-48 h of treatment of all products showed a significant decline in the cancer cell population as revealed by microscopically and the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium (MTT) assay. The inhibitory concentration (IC₅₀) values of the products ranged between 0.75 and 2.25 µg/mL. When tested on normal and healthy cells (HEK-293), we found that the treatment of products did not produce any effects on the normal cells, which suggests that all products selectively targeted the cancerous cells. The anti-bacterial properties of the samples were also evaluated by Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays, which showed that products also inhibited the bacterial growth. Full article

(This article belongs to the Special Issue Functional Nanomagnetics and Magneto-Optical Nanomaterials)

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XRD powder patterns of Mn0.5Zn0.5EuxSmxFe1.5−2xO4 (0.01 ≤ x ≤ 0.05) NPs. Full article ">Figure 2
SEM of Mn0.5Zn0.5EuxSmxFe1.5−2xO4 for x = 0.01, 0.03, and 0.05 and EDX x = 0.03 NPs. Full article ">Figure 3
TEM of Mn0.5Zn0.5EuxSmxFe1.5−2xO4 (x = 0.03 and 0.05) NPs. Full article ">Figure 4
Cancer cells stained with 4′,6-diamidino-2-phenylindole (DAPI). HCT-116 cells treated with Mn0.5Zn0.5SmxEuxFe1.8−2xO4 (0.01 ≤ x ≤ 0.05) NPs for 48 h. (A) is control without treatment, (B) treated with Mn0.5Zn0.5SmxEuxFe1.8−2xO4 NPs for x = 0.01 concentration (2.35 µg/mL), and (C) treated with Mn0.5Zn0.5SmxEuxFe1.8−2xO4 NPs for x = 0.05 concentration (2.33 µg/mL). Arrows in B and C indicate the loss of nuclear staining. 200× magnifications. Full article ">Figure 5
MIC/MBC of Mn0.5Zn0.5SmxEuxFe1.8−2xO4 (0.01 ≤ x ≤ 0.05) against (A) E. coli (B) S. aureus. Full article ">Figure 6
SEM micrographs of Mn0.5Zn0.5SmxEuxFe1.8−2xO4 (0.01 ≤ x ≤ 0.05) NPs treated (I) E. coli, (II) S. aureus. (a) untreated cells (control), (b) x = 0.01, (c) 0.02, (d) 0.03, (e) 0.04, and (f) 0.05. Full article ">

12 pages, 4014 KiB

Open AccessArticle

Reveal the Deformation Mechanism of (110) Silicon from Cryogenic Temperature to Elevated Temperature by Molecular Dynamics Simulation

by Jing Han, Yuanming Song, Wei Tang, Cong Wang, Liang Fang, Hua Zhu, Jiyun Zhao and Jiapeng Sun

Nanomaterials 2019, 9(11), 1632; https://doi.org/10.3390/nano9111632 - 18 Nov 2019

Cited by 12 | Viewed by 2954

Abstract

Silicon undergoes a brittle-to-ductile transition as its characteristic dimension reduces from macroscale to nanoscale. The thorough understanding of the plastic deformation mechanism of silicon at the nanoscale is still challenging, although it is essential for developing Si-based micro/nanoelectromechanical systems (MEMS/NEMS). Given the wide [...] Read more.

Silicon undergoes a brittle-to-ductile transition as its characteristic dimension reduces from macroscale to nanoscale. The thorough understanding of the plastic deformation mechanism of silicon at the nanoscale is still challenging, although it is essential for developing Si-based micro/nanoelectromechanical systems (MEMS/NEMS). Given the wide application of silicon in extreme conditions, it is, therefore, highly desirable to reveal the nanomechanical behavior of silicon from cryogenic temperature to elevated temperature. In this paper, large-scale molecular dynamics (MD) simulations were performed to reveal the spherical nanoindentation response and plastic deformation mechanism of (110)Si at the temperature range of 0.5 K to 573 K. Special attention was paid to the effect of temperature. Multiple pop-ins detected in load/pressure-indentation strain curves are impacted by temperature. Four featured structures induced by nanoindentation, including high-pressure phases, extrusion of α-Si, dislocations, and crack, are observed at all temperatures, consistent with experiment results. The detailed structure evolution of silicon was revealed at the atomic scale and its dependence on temperature was analyzed. Furthermore, structure changes were correlated with pop-ins in load/pressure-indentation strain curves. These results may advance our understanding of the mechanical properties of silicon. Full article

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14 pages, 8387 KiB

Open AccessArticle

Heteroepitaxial Growth of High-Quality and Crack-Free AlN Film on Sapphire Substrate with Nanometer-Scale-Thick AlN Nucleation Layer for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

by Jie Zhao, Hongpo Hu, Yu Lei, Hui Wan, Liyan Gong and Shengjun Zhou

Nanomaterials 2019, 9(11), 1634; https://doi.org/10.3390/nano9111634 - 17 Nov 2019

Cited by 15 | Viewed by 4162

Abstract

High-quality and crack-free aluminum nitride (AlN) film on sapphire substrate is the foundation for high-efficiency aluminum gallium nitride (AlGaN)-based deep ultraviolet light-emitting diodes (DUV LEDs). We reported the growth of high-quality and crack-free AlN film on sapphire substrate with a nanometer-scale-thick AlN nucleation [...] Read more.

High-quality and crack-free aluminum nitride (AlN) film on sapphire substrate is the foundation for high-efficiency aluminum gallium nitride (AlGaN)-based deep ultraviolet light-emitting diodes (DUV LEDs). We reported the growth of high-quality and crack-free AlN film on sapphire substrate with a nanometer-scale-thick AlN nucleation layer (NL). Three kinds of nanometer-scale-thick AlN NLs, including in situ low-temperature AlN (LT-AlN) NL, oxygen-undoped ex situ sputtered AlN NL, and oxygen-doped ex situ sputtered AlN NL, were prepared for epitaxial growth of AlN films on sapphire substrates. The influence of nanoscale AlN NL thickness on the optical transmittance, strain state, surface morphology, and threading dislocation (TD) density of the grown AlN film on sapphire substrate were carefully investigated. The average optical transmittance of AlN film on sapphire substrate with oxygen-doped sputtered AlN NL was higher than that of AlN films on sapphire substrates with LT-AlN NL and oxygen-undoped sputtered AlN NL in the 200–270 nm wavelength region. However, the AlN film on sapphire substrate with oxygen-undoped sputtered AlN NL had the lowest TD density among AlN films on sapphire substrates. The AlN film on sapphire substrate with the optimum thickness of sputtered AlN NL showed weak tensile stress, a crack-free surface, and low TD density. Furthermore, a 270-nm AlGaN-based DUV LED was grown on the high-quality and crack-free AlN film. We believe that our results offer a promising and practical route for obtaining high-quality and crack-free AlN film for DUV LED. Full article

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11 pages, 4613 KiB

Open AccessArticle

The Growth of Graphene on Ni–Cu Alloy Thin Films at a Low Temperature and Its Carbon Diffusion Mechanism

by Yibo Dong, Sheng Guo, Huahai Mao, Chen Xu, Yiyang Xie, Chuantong Cheng, Xurui Mao, Jun Deng, Guanzhong Pan and Jie Sun

Nanomaterials 2019, 9(11), 1633; https://doi.org/10.3390/nano9111633 - 17 Nov 2019

Cited by 11 | Viewed by 3816

Abstract

Carbon solid solubility in metals is an important factor affecting uniform graphene growth by chemical vapor deposition (CVD) at high temperatures. At low temperatures, however, it was found that the carbon diffusion rate (CDR) on the metal catalyst surface has a greater impact [...] Read more.

Carbon solid solubility in metals is an important factor affecting uniform graphene growth by chemical vapor deposition (CVD) at high temperatures. At low temperatures, however, it was found that the carbon diffusion rate (CDR) on the metal catalyst surface has a greater impact on the number and uniformity of graphene layers compared with that of the carbon solid solubility. The CDR decreases rapidly with decreasing temperatures, resulting in inhomogeneous and multilayer graphene. In the present work, a Ni–Cu alloy sacrificial layer was used as the catalyst based on the following properties. Cu was selected to increase the CDR, while Ni was used to provide high catalytic activity. By plasma-enhanced CVD, graphene was grown on the surface of Ni–Cu alloy under low pressure using methane as the carbon source. The optimal composition of the Ni–Cu alloy, 1:2, was selected through experiments. In addition, the plasma power was optimized to improve the graphene quality. On the basis of the parameter optimization, together with our previously-reported, in-situ, sacrificial metal-layer etching technique, relatively homogeneous wafer-size patterned graphene was obtained directly on a 2-inch SiO₂/Si substrate at a low temperature (~600 °C). Full article

(This article belongs to the Section Nanocomposite Materials)

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(a)–(e) The Raman spectra and corresponding optical images of the graphene on SiO2/Si substrates catalyzed by Ni–Cu alloys with different compositions (Ni:Cu = 1:10 (a), 1:3 (b), 1:2 (c), 1:1 (d) and 2:1 (e), respectively). Full article ">Figure 2
(a,c,e) The AFM, optical and SEM images of the graphene grown on the Ni1Cu3 alloy, respectively. (b,d,f) The AFM, optical and SEM images of the graphene grown on the Ni2Cu1 alloy, respectively. (g,h) The diffusion mechanism of carbon atoms on Cu and Ni surfaces, respectively. Full article ">Figure 3
Theoretically determined tracer diffusivity (10-12 m2/s) for (a) the bulk diffusion rate of carbon atoms in alloys with different Ni–Cu ratios at 600 °C. (b) The bulk diffusion rate of carbon atoms in alloys with different Ni–Cu ratios at 600 °C and 800 °C. Full article ">Figure 4
(a) Raman spectra of the graphene grown with and without plasma at 600 °C. (b) Raman spectra of the graphene grown with different plasma powers. (c) The photograph of the growth chamber. (d) The photograph taken during the growth process. Full article ">Figure 5
(a–d) Schematic illustration of the etching process of our in-situ, transfer-free growth method. (a) After the graphene growth, PMMA coating is spun on the sample surface. (b) When the sample is immersed in the metal etchant, the etchant can efficiently penetrate through the molecular gap of PMMA and the grain boundary of the graphene to achieve the metal etching. (c,d) After the metal is completely etched away, the PMMA/graphene films will fall on the substrate. (e,f) Wafer-level graphene growth. The photograph of the sample before (e) and after (f) the metal sacrificial layer etching. (g) An optical image of the graphene at 1000× magnification. (h,i) Raman mapping of the D/G and G/2D ratios of the graphene over 50 × 50 μm. Full article ">

20 pages, 1506 KiB

Open AccessReview

Metal Oxide Nanoparticles in Therapeutic Regulation of Macrophage Functions

by Marina S. Dukhinova, Artur. Y. Prilepskii, Alexander A. Shtil and Vladimir V. Vinogradov

Nanomaterials 2019, 9(11), 1631; https://doi.org/10.3390/nano9111631 - 16 Nov 2019

Cited by 61 | Viewed by 8636

Abstract

Macrophages are components of the innate immune system that control a plethora of biological processes. Macrophages can be activated towards pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes depending on the cue; however, polarization may be altered in bacterial and viral infections, cancer, or autoimmune [...] Read more.

Macrophages are components of the innate immune system that control a plethora of biological processes. Macrophages can be activated towards pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes depending on the cue; however, polarization may be altered in bacterial and viral infections, cancer, or autoimmune diseases. Metal (zinc, iron, titanium, copper, etc.) oxide nanoparticles are widely used in therapeutic applications as drugs, nanocarriers, and diagnostic tools. Macrophages can recognize and engulf nanoparticles, while the influence of macrophage-nanoparticle interaction on cell polarization remains unclear. In this review, we summarize the molecular mechanisms that drive macrophage activation phenotypes and functions upon interaction with nanoparticles in an inflammatory microenvironment. The manifold effects of metal oxide nanoparticles on macrophages depend on the type of metal and the route of synthesis. While largely considered as drug transporters, metal oxide nanoparticles nevertheless have an immunotherapeutic potential, as they can evoke pro- or anti-inflammatory effects on macrophages and become essential for macrophage profiling in cancer, wound healing, infections, and autoimmunity. Full article

(This article belongs to the Special Issue Immune Responses to Nanomaterials for Biomedical Applications)

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Macrophage polarization: M1 (classical, pro-inflammatory) and M2 (alternative, anti-inflammatory). M1 polarization can be triggered by lipopolysaccharides (LPS) and/or interferon gamma (INFγ). M1 macrophages express high CD80 and MHCII and produce pro-inflammatory cytokines to stimulate the innate and adaptive immune activity of monocytes, neutrophils, T- and B-lymphocytes. M2 cells are characterized by surface markers Ym1, CD206, and mannose receptor, as well as by cytokines that have a potential for immunosuppression and tissue regeneration. Tumor-associated macrophages develop an M2 phenotype and promote the immune escape of tumor cells. Full article ">Figure 2
Systemic and local routes of NPs delivery and distribution. (A). At the systemic level, NPs can enter the organism with water/food/drug uptake or i.v. injections. Local contact with NPs occurs from skin contact, inhalation, and tumor therapy. Eventually, NPs are distributed throughout the organism in a cell free form or can be phagocytized. (B). When the phagocytized NPs are moving with the blood flow, they are accumulated in the heart. Air NPs primarily interact with alveolar MФs. Inhaled and injected NPs can penetrate the blood-brain barrier where they contact with microglia. The ultimate destinations of NPs are the liver and the spleen. Full article ">Figure 3
Molecular mechanisms of pro- and anti-inflammatory effects of NPs on MФs. NPs interact with cell surface receptors and can enter the cells via endocytosis/pinocytosis. (A). Pro-inflammatory signaling of NPs activates Toll-like (TLRs), Fcγ, and SR-A1 and MARCO scavenger receptor pathways with involved downstream MAPK/mTOR cascades and transcription factors STATs, NFkB and IRFs. NPs stimulate cytokine production and release, inflammasome formation, and phagocytic activity, thereby prompting M1 polarization. The immunostimulatory effect of NPs re-shapes the immunosuppressive microenvironment and boosts up antimicrobial or anticancer immunity. (B). The anti-inflammatory activity of NPs is applied to M1 committed MФs, as in chronic inflammatory disorders, autoimmunity, and neurodegeneration. NPs activate transcription factor PPARγ and arginase 1 to inhibit pro-inflammatory NFκB, modulate Jak/STAT pathway, and limit inflammation. Full article ">

15 pages, 4412 KiB

Open AccessFeature PaperArticle

Fractal Silver Dendrites as 3D SERS Platform for Highly Sensitive Detection of Biomolecules in Hydration Conditions

by Maria José Lo Faro, Cristiano D’Andrea, Antonio Alessio Leonardi, Dario Morganti, Alessia Irrera and Barbara Fazio

Nanomaterials 2019, 9(11), 1630; https://doi.org/10.3390/nano9111630 - 16 Nov 2019

Cited by 33 | Viewed by 4852

Abstract

In this paper, we report on the realization of a highly sensitive and low cost 3D surface-enhanced Raman scattering (SERS) platform. The structural features of the Ag dendrite network that characterize the SERS material were exploited, attesting a remarked self-similarity and scale invariance [...] Read more.

In this paper, we report on the realization of a highly sensitive and low cost 3D surface-enhanced Raman scattering (SERS) platform. The structural features of the Ag dendrite network that characterize the SERS material were exploited, attesting a remarked self-similarity and scale invariance over a broad range of length scales that are typical of fractal systems. Additional structural and optical investigations confirmed the purity of the metal network, which was characterized by low oxygen contamination and by broad optical resonances introduced by the fractal behavior. The SERS performances of the 3D fractal Ag dendrites were tested for the detection of lysozyme as probe molecule, attesting an enhancement factor of ~2.4 × 10⁶. Experimental results assessed the dendrite material as a suitable SERS detection platform for biomolecules investigations in hydration conditions. Full article

(This article belongs to the Special Issue Nanomaterials Based on IV-Group Semiconductors)

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Ag dendrite synthesis. Schematic depicting the growth of Ag dendrites from (a) the dissolution of AgNO3 salts in a HF/H2O solvent, leading to the formation of Ag nanoparticles that subsequently precipitate onto the Si bulk. (b) Ag dendrites were developed by further incorporating the Ag+ ions onto the initial seeds. (c) Cross-section SEM microscopy of the produced carpet of Ag dendrites onto the Si bulk. Full article ">Figure 2
Fractal Ag dendrites: Schematic and plan view scanning electron microscopies of Ag dendrites acquired at three different magnification scales of (a–c) in order to test the scale invariance of the fractal. Full article ">Figure 3
Compositional characterization. Energy dispersive X-ray spectroscopy (EDX) compositional maps of the (b) Si (in green), (c) Ag (in blue) and (d) O (in red) X-ray signals in comparison to (a) the SEM cross-section of stored Ag dendrites. (e) The EDX elemental profiles acquired for Si, Ag and O X-ray emission lines along the green line reported in (a) are also shown. Full article ">Figure 4
Ag plasmon resonance. Apparent absorbance spectra of the Ag reference film [<a href="#B55-nanomaterials-09-01630" class="html-bibr">55</a>,<a href="#B56-nanomaterials-09-01630" class="html-bibr">56</a>] (red spectrum) and Ag fractal dendrites (blue spectrum) obtained from the reflectance spectra carried out with an integrating sphere. Full article ">Figure 5
Surface-enhanced Raman scattering (SERS) performance of Ag dendrites. (a) Comparison between the Raman spectra of the lysozyme dry powder (red line), the pure phosphate buffer saline (PBS) solution (dark yellow line), and lysozyme in the PBS solution at 10 mM (black line). Notice that for these latter two spectra performed onto liquid samples, we used glass microcells as holders. (b) shows the Raman spectrum acquired on the bare Ag dendrites, while the blue spectrum in (c) shows the SERS response of 10−5 M of lysozyme onto the Ag dendrite platform. For all the spectra, we used the same 100× microscope objective with an integration time of 30 s. We used a laser power of 4.5 mW for the Raman spectra in (a,b) and 45 μW in the spectrum shown in (c). Full article ">Figure 6
SERS signal from lysozyme target protein (Lyz) hydration region. (a) SERS spectra of lysozyme (10−5 M) measured on three different samples, as representative for the ensemble of measurements, presented in the low and high frequency regions. (b) Enhancement factors measured on the three spectra reported in (a) for the phenylalanine (Phe) peaks at 1006 and 1031 cm−1. The magenta line and dashed rectangle indicate the enhancement factors (EFs) calculated average value. For all the SERS spectra in (a), we used the same 100× microscope objective with an integration time of 30 s and a laser power of 45 μW. Full article ">Figure 6 Cont.
SERS signal from lysozyme target protein (Lyz) hydration region. (a) SERS spectra of lysozyme (10−5 M) measured on three different samples, as representative for the ensemble of measurements, presented in the low and high frequency regions. (b) Enhancement factors measured on the three spectra reported in (a) for the phenylalanine (Phe) peaks at 1006 and 1031 cm−1. The magenta line and dashed rectangle indicate the enhancement factors (EFs) calculated average value. For all the SERS spectra in (a), we used the same 100× microscope objective with an integration time of 30 s and a laser power of 45 μW. Full article ">Figure 7
SERS signal from Lyz in the hydration region. Highlight of the SERS fingerprint of lysozyme onto Ag dendrites (in red) versus the lysozyme powder Raman spectrum (in black) in the water hydration region. For a better comparison, the spectra of the PBS solution drop casted onto the Ag dendrites (in blue), the water drop casted onto the Ag dendrites (in green), and liquid water are also presented (dark yellow). For all the spectra, we used the same 100× microscope objective with an integration time of 30 s, while we adopted a laser power of 4.5 mW for the Raman spectra and a laser power of 45 μW for the SERS one (red line in (a)). For the spectrum measured of the liquid sample (dark yellow line in (b)), we used glass microcells as sample holders. Full article ">

21 pages, 547 KiB

Open AccessReview

Application of Polyphenol-Loaded Nanoparticles in Food Industry

by Danijel D. Milinčić, Dušanka A. Popović, Steva M. Lević, Aleksandar Ž. Kostić, Živoslav Lj. Tešić, Viktor A. Nedović and Mirjana B. Pešić

Nanomaterials 2019, 9(11), 1629; https://doi.org/10.3390/nano9111629 - 16 Nov 2019

Cited by 112 | Viewed by 8513

Abstract

Nanotechnology is an emerging field of science, and nanotechnological concepts have been intensively studied for potential applications in the food industry. Nanoparticles (with dimensions ranging from one to several hundred nanometers) have specific characteristics and better functionality, thanks to their size and other [...] Read more.

Nanotechnology is an emerging field of science, and nanotechnological concepts have been intensively studied for potential applications in the food industry. Nanoparticles (with dimensions ranging from one to several hundred nanometers) have specific characteristics and better functionality, thanks to their size and other physicochemical properties. Polyphenols are recognized as active compounds that have several putative beneficial properties, including antioxidant, antimicrobial, and anticancer activity. However, the use of polyphenols as functional food ingredients faces numerous challenges, such as their poor stability, solubility, and bioavailability. These difficulties could be solved relatively easily by the application of encapsulation. The objective of this review is to present the most recent accomplishments in the usage of polyphenol-loaded nanoparticles in food science. Nanoparticles loaded with polyphenols and their applications as active ingredients for improving physicochemical and functional properties of food, or as components of active packaging materials, were critically reviewed. Potential adverse effects of polyphenol-loaded nanomaterials are also discussed. Full article

(This article belongs to the Special Issue Nanotechnology in Agriculture and Food Industry)

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13 pages, 4101 KiB

Open AccessArticle

Effect of Heterointerface on NO₂ Sensing Properties of In-Situ Formed TiO₂ QDs-Decorated NiO Nanosheets

by Congyi Wu, Jian Zhang, Xiaoxia Wang, Changsheng Xie, Songxin Shi and Dawen Zeng

Nanomaterials 2019, 9(11), 1628; https://doi.org/10.3390/nano9111628 - 16 Nov 2019

Cited by 13 | Viewed by 3030

Abstract

In this work, TiO₂ QDs-modified NiO nanosheets were employed to improve the room temperature NO₂ sensing properties of NiO. The gas sensing studies showed that the response of nanocomposites with the optimal ratio to 60 ppm NO₂ was nearly 10 [...] Read more.

In this work, TiO₂ QDs-modified NiO nanosheets were employed to improve the room temperature NO₂ sensing properties of NiO. The gas sensing studies showed that the response of nanocomposites with the optimal ratio to 60 ppm NO₂ was nearly 10 times larger than that of bare NiO, exhibiting a potential application in gas sensing. Considering the commonly reported immature mechanism that the effective charge transfer between two phases contributes to an enhanced sensitivity, the QDs sensitization mechanism was further detailed by designing a series of contrast experiments. First, the important role of the QDs size effect was revealed by comparing the little enhanced sensitivity of TiO₂ particle-modified NiO with the largely enhanced sensitivity of TiO₂ QDs-NiO. Second, and more importantly, direct evidence of the heterointerface charge transfer efficiency was detailed by the extracted interface bond (Ti-O-Ni) using XPS peak fitting. This work can thus provide guidelines to design more QDs-modified nanocomposites with higher sensitivity for practical applications. Full article

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(a) Dynamic sensitivity–recovery curves and (b) responses of the bare NiO nanosheets and the NiO nanosheets modified with different quantities of TiO2 QDs to different concentrations of NO2 at room temperature; (c) Responses of NiO nanosheets modified with different sizes of TiO2 nanoparticle to 60 ppm NO2 at room temperature. Full article ">Figure 2
TEM images of (a) bare NiO nanosheets, and (b) bare TiO2 QDs. Low- and high-magnification images of (c,d) TiO2QDs-NiO, (e) TiO215-NiO, and (f) TiO230-NiO. Full article ">Figure 3
(a) The UPS spectra of TiO2 QDs; (b) The XPS spectrum of TiO2 QDs; (c) The plot of (αhυ)2 against photon energy (hυ) for TiO2 QDs; (d) The corresponding energy band structure of TiO2 QDs based on the UPS, XPS, and UV-vis results. Full article ">Figure 4
(a) Ni 2p spectra of the bare NiO and the TiO2QDs-NiO nanohybrids. (b) With the increase of the TiO2 QDs content, a comparison between the variation of the responses to 60 ppm NO2 and the variation of the binding energy shift values is shown. (c) Ni 2p spectra of the bare NiO and the 5TiO2QDs-NiO, 20TiO215-NiO, and 50TiO230-NiO. (d) With the increase of the TiO2 nanoparticle size, a comparison between the variation of the maximum responses to 60 ppm NO2 and the variation of the binding energy shift values is shown. (e) O 1s spectra of the 5TiO2QDs-NiO. (f) With the increase of the TiO2 QDs content, a comparison between the variation of the responses to 60 ppm NO2 and the variation of the peak area ratio of Ni-O-Ti is shown. Full article ">Figure 5
(a) The energy band diagram of the as-prepared samples, before and after contact. (b) The schematic of the interfacial interaction between the TiO2-NiO2 nanohybrids structure and NO2 molecules. (c) Comparison of the surface band bending between NiO nanosheets, large TiO2 nanoparticle-modified NiO nanosheets, and TiO2 QDs-modified NiO nanosheets. Full article ">

13 pages, 5054 KiB

Open AccessArticle

Optimizing the Interface between Hole Transporting Material and Nanocomposite for Highly Efficient Perovskite Solar Cells

by Zeinab Safari, Mahmood Borhani Zarandi, Antonella Giuri, Francesco Bisconti, Sonia Carallo, Andrea Listorti, Carola Esposito Corcione, Mohamad Reza Nateghi, Aurora Rizzo and Silvia Colella

Nanomaterials 2019, 9(11), 1627; https://doi.org/10.3390/nano9111627 - 16 Nov 2019

Cited by 26 | Viewed by 6246

Abstract

The performances of organometallic halide perovskite-based solar cells severely depend on the device architecture and the interface between each layer included in the device stack. In particular, the interface between the charge transporting layer and the perovskite film is crucial, since it represents [...] Read more.

The performances of organometallic halide perovskite-based solar cells severely depend on the device architecture and the interface between each layer included in the device stack. In particular, the interface between the charge transporting layer and the perovskite film is crucial, since it represents both the substrate where the perovskite polycrystalline film grows, thus directly influencing the active layer morphology, and an important site for electrical charge extraction and/or recombination. Here, we focus on engineering the interface between a perovskite-polymer nanocomposite, recently developed by our group, and different commonly employed polymeric hole transporters, namely PEDOT: PSS [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)], PEDOT, PTAA [poly(bis 4-phenyl}{2,4,6-trimethylphenyl}amine)], Poly-TPD [Poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)-benzidine] Poly-TPD, in inverted planar perovskite solar cell architecture. The results show that when Poly-TPD is used as the hole transfer material, perovskite film morphology improved, suggesting an improvement in the interface between Poly-TPD and perovskite active layer. We additionally investigate the effect of the Molecular Weight (MW) of Poly-TPD on the performance of perovskite solar cells. By increasing the MW, the photovoltaic performances of the cells are enhanced, reaching power conversion efficiency as high as 16.3%. Full article

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20 pages, 2963 KiB

Open AccessArticle

Development of Superparamagnetic Nanoparticles Coated with Polyacrylic Acid and Aluminum Hydroxide as an Efficient Contrast Agent for Multimodal Imaging

by Manuel Antonio González-Gómez, Sarah Belderbos, Susana Yañez-Vilar, Yolanda Piñeiro, Frederik Cleeren, Guy Bormans, Christophe M. Deroose, Willy Gsell, Uwe Himmelreich and José Rivas

Nanomaterials 2019, 9(11), 1626; https://doi.org/10.3390/nano9111626 - 15 Nov 2019

Cited by 73 | Viewed by 5592

Abstract

Early diagnosis of disease and follow-up of therapy is of vital importance for appropriate patient management since it allows rapid treatment, thereby reducing mortality and improving health and quality of life with lower expenditure for health care systems. New approaches include nanomedicine-based diagnosis [...] Read more.

Early diagnosis of disease and follow-up of therapy is of vital importance for appropriate patient management since it allows rapid treatment, thereby reducing mortality and improving health and quality of life with lower expenditure for health care systems. New approaches include nanomedicine-based diagnosis combined with therapy. Nanoparticles (NPs), as contrast agents for in vivo diagnosis, have the advantage of combining several imaging agents that are visible using different modalities, thereby achieving high spatial resolution, high sensitivity, high specificity, morphological, and functional information. In this work, we present the development of aluminum hydroxide nanostructures embedded with polyacrylic acid (PAA) coated iron oxide superparamagnetic nanoparticles, Fe₃O₄@Al(OH)₃, synthesized by a two-step co-precipitation and forced hydrolysis method, their physicochemical characterization and first biomedical studies as dual magnetic resonance imaging (MRI)/positron emission tomography (PET) contrast agents for cell imaging. The so-prepared NPs are size-controlled, with diameters below 250 nm, completely and homogeneously coated with an Al(OH)₃ phase over the magnetite cores, superparamagnetic with high saturation magnetization value (Ms = 63 emu/g-Fe₃O₄), and porous at the surface with a chemical affinity for fluoride ion adsorption. The suitability as MRI and PET contrast agents was tested showing high transversal relaxivity (r₂) (83.6 mM⁻¹ s⁻¹) and rapid uptake of ¹⁸F-labeled fluoride ions as a PET tracer. The loading stability with ¹⁸F-fluoride was tested in longitudinal experiments using water, buffer, and cell culture media. Even though the stability of the ¹⁸F-label varied, it remained stable under all conditions. A first in vivo experiment indicates the suitability of Fe₃O₄@Al(OH)₃ nanoparticles as a dual contrast agent for sensitive short-term (PET) and high-resolution long-term imaging (MRI). Full article

(This article belongs to the Special Issue Frontiers in Nanomaterials for Clinical Imaging and Selective Therapy)

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24 pages, 6498 KiB

Open AccessArticle

Polymer Membranes Sonocoated and Electrosprayed with Nano-Hydroxyapatite for Periodontal Tissues Regeneration

by Julia Higuchi, Giuseppino Fortunato, Bartosz Woźniak, Agnieszka Chodara, Sebastian Domaschke, Sylwia Męczyńska-Wielgosz, Marcin Kruszewski, Alex Dommann and Witold Łojkowski

Nanomaterials 2019, 9(11), 1625; https://doi.org/10.3390/nano9111625 - 15 Nov 2019

Cited by 40 | Viewed by 4721

Abstract

Diseases of periodontal tissues are a considerable clinical problem, connected with inflammatory processes and bone loss. The healing process often requires reconstruction of lost bone in the periodontal area. For that purpose, various membranes are used to prevent ingrowth of epithelium in the [...] Read more.

Diseases of periodontal tissues are a considerable clinical problem, connected with inflammatory processes and bone loss. The healing process often requires reconstruction of lost bone in the periodontal area. For that purpose, various membranes are used to prevent ingrowth of epithelium in the tissue defect and enhance bone regeneration. Currently-used membranes are mainly non-resorbable or are derived from animal tissues. Thus, there is an urgent need for non-animal-derived bioresorbable membranes with tuned resorption rates and porosity optimized for the circulation of body nutrients. We demonstrate membranes produced by the electrospinning of biodegradable polymers (PDLLA/PLGA) coated with nanohydroxyapatite (nHA). The nHA coating was made using two methods: sonocoating and electrospraying of nHA suspensions. In a simulated degradation study, for electrosprayed membranes, short-term calcium release was observed, followed by hydrolytic degradation. Sonocoating produced a well-adhering nHA layer with full coverage of the fibers. The layer slowed the polymer degradation and increased the membrane wettability. Due to gradual release of calcium ions the degradation-associated acidity of the polymer was neutralized. The sonocoated membranes exhibited good cellular metabolic activity responses against MG-63 and BJ cells. The collected results suggest their potential use in Guided Tissue Regeneration (GTR) and Guided Bone Regeneration (GBR) periodontal procedures. Full article

(This article belongs to the Special Issue Nanomaterials and Nanotechnology in Dentistry)

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12 pages, 4343 KiB

Open AccessArticle

A Facile, One-Step Synthesis of Silicon/Silicon Carbide/Carbon Nanotube Nanocomposite as a Cycling-Stable Anode for Lithium Ion Batteries

by Yi Zhang, Kai Hu, Yunlei Zhou, Yingbin Xia, Nengfei Yu, Guanglei Wu, Yusong Zhu, Yuping Wu and Haibo Huang

Nanomaterials 2019, 9(11), 1624; https://doi.org/10.3390/nano9111624 - 15 Nov 2019

Cited by 49 | Viewed by 6533

Abstract

Silicon/carbon nanotube (Si/CNTs) nanocomposite is a promising anode material for lithium ion batteries (LIBs). Challenges related to the tricky synthesis process, as well as the weak interaction between Si and CNTs, hinder practical applications. To address these issues, a facile, one-step method to [...] Read more.

Silicon/carbon nanotube (Si/CNTs) nanocomposite is a promising anode material for lithium ion batteries (LIBs). Challenges related to the tricky synthesis process, as well as the weak interaction between Si and CNTs, hinder practical applications. To address these issues, a facile, one-step method to synthesize Si/CNTs nanocomposite by using silica (SiO₂) as a reactant via a magnesium reduction process was developed. In this synthesis, the heat released enables the as-obtained Si to react with CNTs in the interfacial region to form silicon carbide (SiC). By virtue of the unique structure composed of Si nanoparticles strongly anchored to conductive CNTs network with stable Si–C chemical bonding, the Si/SiC/CNT nanocomposite delivers a stable capacity of ~1100 mAh g⁻¹ and a capacity retention of about 83.8% after 200 cycles at a current density of 100 mA g⁻¹. Our studies may provide a convenient strategy for the preparation of the Si/C anode of LIBs. Full article

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17 pages, 3721 KiB

Open AccessArticle

Synergistical Use of Electrostatic and Hydrophobic Interactions for the Synthesis of a New Class of Multifunctional Nanohybrids: Plasmonic Magneto-Liposomes

by Gabriela Fabiola Știufiuc, Ștefan Nițică, Valentin Toma, Cristian Iacoviță, Dietrich Zahn, Romulus Tetean, Emil Burzo, Constantin Mihai Lucaciu and Rareș Ionuț Știufiuc

Nanomaterials 2019, 9(11), 1623; https://doi.org/10.3390/nano9111623 - 15 Nov 2019

Cited by 8 | Viewed by 2834

Abstract

By carefully controlling the electrostatic interactions between cationic liposomes, which already incorporate magnetic nanoparticles in the bilayers, and anionic gold nanoparticles, a new class of versatile multifunctional nanohybrids (plasmonic magneto-liposomes) that could have a major impact in drug delivery and controlled release applications [...] Read more.

By carefully controlling the electrostatic interactions between cationic liposomes, which already incorporate magnetic nanoparticles in the bilayers, and anionic gold nanoparticles, a new class of versatile multifunctional nanohybrids (plasmonic magneto-liposomes) that could have a major impact in drug delivery and controlled release applications has been synthesized. The experimental results confirmed the successful synthesis of hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) and polyethylene glycol functionalized (PEGylated) gold nanoparticles (AuNPs). The SPIONs were incorporated in the liposomal lipidic bilayers, thus promoting the formation of cationic magnetoliposomes. Different concentrations of SPIONs were loaded in the membrane. The cationic magnetoliposomes were decorated with anionic PEGylated gold nanoparticles using electrostatic interactions. The successful incorporation of SPIONs together with the modifications they generate in the bilayer were analyzed using Raman spectroscopy. The plasmonic properties of the multifunctional nanohybrids were investigated using UV-Vis absorption and (surface-enhanced) Raman spectroscopy. Their hyperthermic properties were recorded at different frequencies and magnetic field intensities. After the synthesis, the nanosystems were extensively characterized in order to properly evaluate their potential use in drug delivery applications and controlled release as a result of the interaction with an external stimulus, such as an NIR laser or alternating magnetic field. Full article

(This article belongs to the Special Issue Multifunctional Magnetic Nanomaterials for Molecular Imaging and Therapy)

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19 pages, 5162 KiB

Open AccessArticle

Preparation of Anisotropic Aerogels with Pristine Graphene by Heat Flow and Study of Their Effects on Heat Transfer in Paraffin

by Jinhui Huang, Buning Zhang, Ming He, Xue Huang, Guoqiang Yin and Yingde Cui

Nanomaterials 2019, 9(11), 1622; https://doi.org/10.3390/nano9111622 - 15 Nov 2019

Cited by 3 | Viewed by 2925

Abstract

In this study, anisotropic graphene/graphene oxide (GO) aerogels (AGAs) were obtained by freeze-drying after direct participation of pristine graphene in the self-assembly of anisotropic gel by the heat flow method. After vacuum microwave treatment, the physical, chemical and structural characteristics of the AGAs [...] Read more.

In this study, anisotropic graphene/graphene oxide (GO) aerogels (AGAs) were obtained by freeze-drying after direct participation of pristine graphene in the self-assembly of anisotropic gel by the heat flow method. After vacuum microwave treatment, the physical, chemical and structural characteristics of the AGAs were investigated. The results show that AGAs, in which the internal graphene sheets are parallel to the heat flow direction, are successfully prepared. After microwave treatment, the amount of oxygen and nitrogen reduces significantly and the sp2 domain increases. However, at the same time, many fragments and holes are generated in the graphene sheets. The effects of AGAs on the phase transition of paraffin is studied, and the results show that the melting enthalpy, solidification enthalpy and initial melting temperature of AGA/paraffin composites decreases as the GO content in the AGAs increases, whereas the melting range, solidifying range and subcooling degree increases. The highest axial thermal conductivity of the AGA/paraffin composite is 1.45 W/(mK), and the thermal conductivity enhancement efficiency is 884% (AGA content was 0.53 vol %). Compared with previously investigated, similar AGA/paraffin composites, the aerogels fabricated in this study have the obvious advantages of a simple fabrication process, a low cost and a high thermal conductivity enhancement efficiency. These aerogels possess the potential for application in phase-change energy storage (PES), thermal energy management and other fields. Full article

(This article belongs to the Special Issue Synthesis and Applications of Graphite Oxide and Graphene Oxide Nanocomposites)

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15 pages, 4644 KiB

Open AccessArticle

Complexes Formed by Hydrophobic Interaction between Ag-Nanospheres and Adsorbents for the Detection of Methyl Salicylate VOC

by Jinhyuk Park, J. Alex Thomasson, Sandun Fernando, Kyung-Min Lee and Timothy J. Herrman

Nanomaterials 2019, 9(11), 1621; https://doi.org/10.3390/nano9111621 - 15 Nov 2019

Cited by 7 | Viewed by 3414

Abstract

Surface-enhanced Raman spectroscopy (SERS) has been widely investigated in many applications. However, only little work has been done on using SERS for the detection of volatile organic compounds (VOCs), primarily due to the challenges associated with fabricating SERS substrates with sufficient hotspots for [...] Read more.

Surface-enhanced Raman spectroscopy (SERS) has been widely investigated in many applications. However, only little work has been done on using SERS for the detection of volatile organic compounds (VOCs), primarily due to the challenges associated with fabricating SERS substrates with sufficient hotspots for signal enhancement and with the surface interfacially compatible for the VOCs. This study investigated the phase transfer of Ag-nanospheres (AgNSs) from the aqueous phase to the non-aqueous phase by electrostatic interaction induced by cationic surfactants, and the feasibility of the transferred AgNSs as SERS substrates for the determination of methyl salicylate VOC. Results indicated that one of three cationic surfactants, tetraoctylammonium bromide (TOAB) dissolved in organic solvent showed successful phase transfer of the AgNSs confirmed by several characterization analyses. The complex formed by hydrophobic interaction between the transferred AgNSs and Tenax-TA adsorbent polymer was able to be utilized as a SERS substrate, and the volatile of methyl salicylate could be easily determined from SERS measurements at 4 h static volatile collection. Therefore, the proposed new techniques can be effectively employed to areas where many VOCs relevant to food and agriculture need to be analyzed. Full article

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12 pages, 3793 KiB

Open AccessArticle

Reconfigurable Local Photoluminescence of Atomically-Thin Semiconductors via Ferroelectric-Assisted Effects

by Changhyun Ko

Nanomaterials 2019, 9(11), 1620; https://doi.org/10.3390/nano9111620 - 15 Nov 2019

Cited by 3 | Viewed by 3196

Abstract

Combining a pair of materials of different structural dimensions and functional properties into a hybrid material system may realize unprecedented multi-functional device applications. Especially, two-dimensional (2D) materials are suitable for being incorporated into the heterostructures due to their colossal area-to-volume ratio, excellent flexibility, [...] Read more.

Combining a pair of materials of different structural dimensions and functional properties into a hybrid material system may realize unprecedented multi-functional device applications. Especially, two-dimensional (2D) materials are suitable for being incorporated into the heterostructures due to their colossal area-to-volume ratio, excellent flexibility, and high sensitivity to interfacial and surface interactions. Semiconducting molybdenum disulfide (MoS₂), one of the well-studied layered materials, has a direct band gap as one molecular layer and hence, is expected to be one of the promising key materials for next-generation optoelectronics. Here, using lateral 2D/3D heterostructures composed of MoS₂ monolayers and nanoscale inorganic ferroelectric thin films, reversibly tunable photoluminescence has been demonstrated at the microscale to be over 200% upon ferroelectric polarization reversal by using nanoscale conductive atomic force microscopy tips. Also, significant ferroelectric-assisted modulation in electrical properties has been achieved from field-effect transistor devices based on the 2D/3D heterostructrues. Moreover, it was also shown that the MoS₂ monolayer can be an effective electric field barrier in spite of its sub-nanometer thickness. These results would be of close relevance to exploring novel applications in the fields of optoelectronics and sensor technology. Full article

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

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ML-MoS2/PZT heterostructure preparation and optical characterization. Optical microscopy images of (a) as-grown ML-MoS2 flakes on a SiO2/Si substrate and (b) a representative ML-MoS2 flake wet-transferred on a PZT thin film surface. (c) PL and (d) Raman spectra measured from the ML-MoS2 flake displayed in (a) and the bare PZT surface as a reference. Full article ">Figure 2
Schematic of the poling process on AFM. (a) Up-polarized (P↑) and (b) down-polarized (P↓) states are achieved when a PZT thin films are applied by negative and positive VP above the threshold voltage for polarization reversal using a conductive AFM tip, respectively. During the poling process, a metallic SRO layer is grounded electrically. Full article ">Figure 3
Poling effects on the ML-MoS2/PZT heterostructure. (a) Optical microscopy (OM) image of a ML-MoS2 flake with a scale bar which works for all the other images. PFM images of (b) the ML-MoS2 flake on the PZT thin film whose left and right half areas are polarized in the P↑ and P↓ states by the poling process with the VP of −12 V and +12 V, respectively, and (c) vice versa. (d) Topography AFM image of the ML-MoS2 flake simultaneously obtained with the PFM image including the representative height profile for the corresponding green line, verifying the thickness of ML-MoS2 flake. PL peak area maps of the identical ML-MoS2 flake in (e–g) were scanned before poling and after the poling processes of (b,c), in order. (h–j) PL peak position maps displayed in the same sequence as in (e–g). (k) PL spectra measured from the spots of P↑ and P↓ regions marked in (f) along with that of the bare PZT as a reference. X and X− denote the emissions of neutral and negatively-charged excitons, respectively. Full article ">Figure 4
Electrical back-gated experiments on the ML-MoS2/PZT heterostructures. (a) Optical microscopy image of a ML-MoS2 sheet with a metal electrode. (b) Schematics of back-gating experiment. In this experiment, no voltage is applied between the source and drain. (c–f) Set of images of the PL peak area measured after back gating with VG of −5 V, +5 V, +10 V, and again −5 V in order. (g–j) The set of images of PL peak position measured in a series in the same order of (c–f). Full article ">Figure 5
Electrical transport characterization of the ML-MoS2/PZT heterostructures. (a) Optical microscopy image and (b) topography AFM image of a device with a channel based on two ML-MoS2 sheets and metal electrodes on a PZT thin film. PL peak area maps of (c,d) were scanned after the poling process with VP of −12 V and +12 V, respectively. (e) Device schematics for FET measurements with the circuit. (f) FET characteristic curves of drain current (ID) vs. gate voltage (VG) measured at the source-drain voltage (VSD) of 1.0 V in the P↑ and P↓ states, respectively. The leakage current (IG) vs. VG are also plotted as dashed lines for both states. Note that the absolute values were taken for ID and IG. Full article ">Figure 6
The ultrathin electric field shield. PFM images of a ML-MoS2 flake on a BFO thin film scanned (a) as-prepared before poling and after poling with the VP of (b) +8 V and (c) +10 V, respectively. Up to VP of +8 V, the area of the BFO thin film beneath the ML-MoS2 flake was not poled well, indicating that a ML-MoS2 flake prevents field penetration into the BFO thin film. Full article ">

19 pages, 5025 KiB

Open AccessArticle

Ullmann Reactions of Carbon Nanotubes—Advantageous and Unexplored Functionalization toward Tunable Surface Chemistry

by Anna Kolanowska, Anna Wioleta Kuziel, Rafał Grzegorz Jędrysiak, Maciej Krzywiecki, Emil Korczeniewski, Marek Wiśniewski, Artur Piotr Terzyk and Sławomir Boncel

Nanomaterials 2019, 9(11), 1619; https://doi.org/10.3390/nano9111619 - 15 Nov 2019

Cited by 11 | Viewed by 4438

Abstract

We demonstrate Ullmann-type reactions as novel and advantageous functionalization of carbon nanotubes (CNTs) toward tunable surface chemistry. The functionalization routes comprise O-, N-, and C-arylation of chlorinated CNTs. We confirm the versatility and efficiency of the reaction allowing functionalization degrees [...] Read more.

We demonstrate Ullmann-type reactions as novel and advantageous functionalization of carbon nanotubes (CNTs) toward tunable surface chemistry. The functionalization routes comprise O-, N-, and C-arylation of chlorinated CNTs. We confirm the versatility and efficiency of the reaction allowing functionalization degrees up to 3.5 mmol g⁻¹ by applying both various nanotube substrates, i.e., single-wall (SWCNTs) and multi-wall CNTs (MWCNTs) of various chirality, geometry, and morphology as well as diverse Ullmann-type reagents: phenol, aniline, and iodobenzene. The reactivity of nanotubes was correlatable with the nanotube diameter and morphology revealing SWCNTs as the most reactive representatives. We have determined the optimized conditions of this two-step synthetic protocol as: (1) chlorination using iodine trichloride (ICl₃), and (2) Ullmann-type reaction in the presence of: copper(I) iodide (CuI), 1,10-phenanthroline as chelating agent and caesium carbonate (Cs₂CO₃) as base. We have analyzed functionalized CNTs using a variety of techniques, i.e., scanning and transmission electron microscopy, energy dispersive spectroscopy, thermogravimetry, comprehensive Raman spectroscopy, and X-ray photoelectron spectroscopy. The analyses confirmed the purely covalent nature of those modifications at all stages. Eventually, we have proved the elaborated protocol as exceptionally tunable since it enabled us: (a) to synthesize superhydrophilic films from—the intrinsically hydrophobic—vertically aligned MWCNT arrays and (b) to produce printable highly electroconductive pastes of enhanced characteristics—as compared for non-modified and otherwise modified MWCNTs—for textronics. Full article

(This article belongs to the Special Issue Carbon Nanotube: Synthesis, Characteristics and Applications)

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24 pages, 8437 KiB

Open AccessArticle

Hall Amplifier Nanoscale Device (HAND): Modeling, Simulations and Feasibility Analysis for THz Sensor

by Avi Karsenty and Raz Mottes

Nanomaterials 2019, 9(11), 1618; https://doi.org/10.3390/nano9111618 - 14 Nov 2019

Cited by 4 | Viewed by 3732

Abstract

HAND (Hall Amplifier Nanoscale Device), a new nano-metric device, was designed, simulated, and modeled for feasibility analysis, with the challenge of combining a well-known macro effect into the nanoscale world. HAND is based on the well-known Hall Effect, and it may enable circuitry [...] Read more.

HAND (Hall Amplifier Nanoscale Device), a new nano-metric device, was designed, simulated, and modeled for feasibility analysis, with the challenge of combining a well-known macro effect into the nanoscale world. HAND is based on the well-known Hall Effect, and it may enable circuitry working at very high frequencies (tens of Tera-Hertz). The architecture, design, and simulations were performed while using Comsol Multi-Physics Package Software. Complementary accurate analytical models were developed to support the understanding of the device functionality, including treatment of specific phenomena, such as heat transfer, and mega-magnet feasibility inside integrated circuits. This new device, combining both the Hall Effect and nanoscale dimensions, holds the potential to change the computing rates in the microelectronics circuitry world, and can serve as a game changer. Full article

(This article belongs to the Special Issue Nano Fabrications of Solid-State Sensors and Sensor Systems)

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15 pages, 5705 KiB

Open AccessArticle

Influence of Nanoscale Textured Surfaces and Subsurface Defects on Friction Behaviors by Molecular Dynamics Simulation

by Ruiting Tong, Zefen Quan, Yangdong Zhao, Bin Han and Geng Liu

Nanomaterials 2019, 9(11), 1617; https://doi.org/10.3390/nano9111617 - 14 Nov 2019

Cited by 13 | Viewed by 3053

Abstract

In nanomaterials, the surface or the subsurface structures influence the friction behaviors greatly. In this work, nanoscale friction behaviors between a rigid cylinder tip and a single crystal copper substrate are studied by molecular dynamics simulation. Nanoscale textured surfaces are modeled on the [...] Read more.

In nanomaterials, the surface or the subsurface structures influence the friction behaviors greatly. In this work, nanoscale friction behaviors between a rigid cylinder tip and a single crystal copper substrate are studied by molecular dynamics simulation. Nanoscale textured surfaces are modeled on the surface of the substrate to represent the surface structures, and the spacings between textures are seen as defects on the surface. Nano-defects are prepared at the subsurface of the substrate. The effects of depth, orientation, width and shape of textured surfaces on the average friction forces are investigated, and the influence of subsurface defects in the substrate is also studied. Compared with the smooth surface, textured surfaces can improve friction behaviors effectively. The textured surfaces with a greater depth or smaller width lead to lower friction forces. The surface with 45° texture orientation produces the lowest average friction force among all the orientations. The influence of the shape is slight, and the v-shape shows a lower average friction force. Besides, the subsurface defects in the substrate make the sliding process unstable and the influence of subsurface defects on friction forces is sensitive to their positions. Full article

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17 pages, 2865 KiB

Open AccessArticle

Nanoparticulate Metal Oxide Top Electrode Interface Modification Improves the Thermal Stability of Inverted Perovskite Photovoltaics

by Ioannis T. Papadas, Fedros Galatopoulos, Gerasimos S. Armatas, Nir Tessler and Stelios A. Choulis

Nanomaterials 2019, 9(11), 1616; https://doi.org/10.3390/nano9111616 - 14 Nov 2019

Cited by 15 | Viewed by 4077

Abstract

Solution processed γ-Fe₂O₃ nanoparticles via the solvothermal colloidal synthesis in conjunction with ligand-exchange method are used for interface modification of the top electrode in inverted perovskite solar cells. In comparison to more conventional top electrodes such as PC(70)BM/Al and PC(70)BM/AZO/Al, [...] Read more.

Solution processed γ-Fe₂O₃ nanoparticles via the solvothermal colloidal synthesis in conjunction with ligand-exchange method are used for interface modification of the top electrode in inverted perovskite solar cells. In comparison to more conventional top electrodes such as PC(70)BM/Al and PC(70)BM/AZO/Al, we show that incorporation of a γ-Fe₂O₃ provides an alternative solution processed top electrode (PC(70)BM/γ-Fe₂O₃/Al) that not only results in comparable power conversion efficiencies but also improved thermal stability of inverted perovskite photovoltaics. The origin of improved stability of inverted perovskite solar cells incorporating PC(70)BM/ γ-Fe₂O₃/Al under accelerated heat lifetime conditions is attributed to the acidic surface nature of γ-Fe₂O₃ and reduced charge trapped density within PC(70)BM/ γ-Fe₂O₃/Al top electrode interfaces. Full article

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Schematic illustration of the ligand exchange method for the preparation of BF4−-capped γ-Fe2O3 NPs. Full article ">Figure 2
(a) Typical TEM image, (b) SAED pattern, (c) XRD pattern of γ-Fe2O3 NPs. The standard pattern of maghemite phase, γ-Fe2O3, (JCPDS No. 39-1346) is also illustrated for collation (magenta bars) and (d) UV-Vis diffuse reflectance spectra versus energy (hv) for the γ-Fe2O3 NPs. Full article ">Figure 3
(a) Room-temperature PL emission spectra of the γ-Fe2O3 NPs. PL measurement was performed on γ-Fe2O3 films on the glass substrate at an excitation wavelength of 550 nm. (b) Mott-Schottky plot of the inverse square space-charge capacitance (1/CSC2) as a function of applied voltage (E) relative to the redox potential of Ag/AgCl (3 M KCl) for the γ-Fe2O3 NPs ETL. Full article ">Figure 4
(a) Schematic representation of the device structure used and (b) the corresponding energy level diagram under study. Full article ">Figure 5
Normalized (a) Voc, (b) Jsc, (c) FF and (d) PCE for three different top electrodes: PC(70)BM/Al, PC(70)BM/AZO/Al, PC(70)BM/γ-Fe2O3/Al. Full article ">Figure 6
(a) Illuminated J-V characteristics and (b) dark J-V characteristics, respectively. Full article ">Figure 7
(a) Mott Schottky measurements of fresh devices at f = 100 kHz and f = 500 Hz and (b) fresh and aged devices at f = 5 kHz. Full article ">

11 pages, 3674 KiB

Open AccessArticle

Fabrication of Cu₂ZnSnS₄ Thin Films from Ball-Milled Nanoparticle inks under Various Annealing Temperatures

by Xianfeng Zhang, Engang Fu, Maoxi Zheng and Yuehui Wang

Nanomaterials 2019, 9(11), 1615; https://doi.org/10.3390/nano9111615 - 14 Nov 2019

Cited by 7 | Viewed by 2940

Abstract

Cu₂ZnSnS₄ (CZTS) has been recognized as a promising thin-film absorber material of chalcopyrite-related solar cells. A two-stage method for fabricating CZTS films using CZTS nanoparticles was developed. Nanocrystal inks fabricated by a ball-milling method was utilized to °C deposit CZTS [...] Read more.

Cu₂ZnSnS₄ (CZTS) has been recognized as a promising thin-film absorber material of chalcopyrite-related solar cells. A two-stage method for fabricating CZTS films using CZTS nanoparticles was developed. Nanocrystal inks fabricated by a ball-milling method was utilized to °C deposit CZTS precursors by spin-coating approach. The CZTS precursors were annealed in the sulfur atmosphere under different annealing temperatures ranging from 550 °C to 650 °C. Influences of annealing temperature on grain growth, composition, crystallinity, and photovoltaic properties of CZTS films were characterized. With the increase of annealing temperature, grain growth was enhanced, while the sulfur atomic ratio fist increased then decreased. The crystallinity of the films was significantly improved after the annealing, and the obvious peak of the secondary phase of ZnS, were observed from the X-ray diffraction results, when the annealing temperature increased to 625 °C. However, the secondary phase was not detected from the surface Raman spectrum. Through comparing the Raman spectrum of different areas of the CZTS film, secondary phases of ZnS and SnS were observed, indicating the decomposition of CZTS films, due to the high temperature. The highest conversion efficiency of 7.5% was obtained when the annealing temperature was 600 °C. Full article

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