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13 pages, 7080 KiB

Open AccessArticle

Plastic Deformation Behavior of Bi-Crystal Magnesium Nanopillars with a {1012} Twin Boundary under Compression: Molecular Dynamics Simulations

by Xiaoyue Yang, Shuang Xu and Qingjia Chi

Materials 2019, 12(5), 750; https://doi.org/10.3390/ma12050750 - 05 Mar 2019

Cited by 3 | Viewed by 3338

Abstract

In this study, molecular dynamics simulations were performed to study the uniaxial compression deformation of bi-crystal magnesium nanopillars with a

{10 \bar{1} 2}

twin boundary (TB). The generation and evolution process of internal defects of magnesium nanopillars were analyzed in [...] Read more.

In this study, molecular dynamics simulations were performed to study the uniaxial compression deformation of bi-crystal magnesium nanopillars with a

{10 \bar{1} 2}

twin boundary (TB). The generation and evolution process of internal defects of magnesium nanopillars were analyzed in detail. Simulation results showed that the initial deformation mechanism was mainly caused by the migration of the twin boundary, and the transformation of TB into (basal/prismatic) B/P interface was observed. After that, basal slip as well as pyramidal slip nucleated during the plastic deformation process. Moreover, a competition mechanism between twin boundary migration and basal slip was found. Basal slip can inhibit the migration of the twin boundary, and

{10 \bar{1} 1} ⟨ 10 \bar{1} 2 ⟩

twins appear at a certain high strain level (

ε

= 0.104). In addition, Schmid factor (SF) analysis was conducted to understand the activations of deformation modes. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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14 pages, 6393 KiB

Open AccessArticle

Rapid Growth of TiO₂ Nanoflowers via Low-Temperature Solution Process: Photovoltaic and Sensing Applications

by M. Shaheer Akhtar, Ahmad Umar, Swati Sood, InSung Jung, H. H. Hegazy and H. Algarni

Materials 2019, 12(4), 566; https://doi.org/10.3390/ma12040566 - 14 Feb 2019

Cited by 23 | Viewed by 3532

Abstract

This paper reports the rapid synthesis, characterization, and photovoltaic and sensing applications of TiO₂ nanoflowers prepared by a facile low-temperature solution process. The morphological characterizations clearly reveal the high-density growth of a three-dimensional flower-shaped structure composed of small petal-like rods. The detailed [...] Read more.

This paper reports the rapid synthesis, characterization, and photovoltaic and sensing applications of TiO₂ nanoflowers prepared by a facile low-temperature solution process. The morphological characterizations clearly reveal the high-density growth of a three-dimensional flower-shaped structure composed of small petal-like rods. The detailed properties confirmed that the synthesized nanoflowers exhibited high crystallinity with anatase phase and possessed an energy bandgap of 3.2 eV. The synthesized TiO₂ nanoflowers were utilized as photo-anode and electron-mediating materials to fabricate dye-sensitized solar cell (DSSC) and liquid nitroaniline sensor applications. The fabricated DSSC demonstrated a moderate conversion efficiency of ~3.64% with a maximum incident photon to current efficiency (IPCE) of ~41% at 540 nm. The fabricated liquid nitroaniline sensor demonstrated a good sensitivity of ~268.9 μA mM⁻¹ cm⁻² with a low detection limit of 1.05 mM in a short response time of 10 s. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 3162 KiB

Open AccessArticle

Green Biosynthesis of Silver Nanoparticles Using Eriobotrya japonica (Thunb.) Leaf Extract for Reductive Catalysis

by Chen Yu, Jingchun Tang, Xiaomei Liu, Xinwei Ren, Meinan Zhen and Lan Wang

Materials 2019, 12(1), 189; https://doi.org/10.3390/ma12010189 - 08 Jan 2019

Cited by 94 | Viewed by 7978

Abstract

This article reports on silver nanoparticles (AgNPs) that were green-synthesized by using Eriobotrya japonica (Thunb.) leaf extract and their use for the catalytic degradation of reactive dyes. The properties of biogenic AgNPs were characterized using UV-vis absorption spectroscopy, field emission scanning electron microscope [...] Read more.

This article reports on silver nanoparticles (AgNPs) that were green-synthesized by using Eriobotrya japonica (Thunb.) leaf extract and their use for the catalytic degradation of reactive dyes. The properties of biogenic AgNPs were characterized using UV-vis absorption spectroscopy, field emission scanning electron microscope (FESEM), X-ray powder diffraction (XRD), transmission electron microscope (TEM), Fourier transforming infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED) analysis. The UV-vis spectroscopy and X-ray analyses confirmed the formation of AgNPs and showed the strong absorbance around 467 nm with surface plasmon resonance (SPR). The mean diameter of biogenic AgNPs at room (20 °C), moderate (50 °C), and high temperatures (80 °C) were 9.26 ± 2.72, 13.09 ± 3.66, and 17.28 ± 5.78 nm, respectively. The reaction temperature had significant impacts on the sizes of synthesized AgNPs. The higher the synthesis temperature, the larger size and the lower catalysis activity for reductive decomposition of reactive dyes via NaBH₄. The results supported a bio-green approach for developing AgNPs with a small size and stable degradation activity of reactive dyes over 92% in 30 min by using Eriobotrya japonica (Thunb.) leaf extract at pH 7, 20 °C, and 1:10 ratio of silver nitrate added to the leaf extract. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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10 pages, 2156 KiB

Open AccessArticle

Bifunction-Integrated Dielectric Nanolayers of Fluoropolymers with Electrowetting Effects

by Hao Wu, Hao Li, Ahmad Umar, Yao Wang and Guofu Zhou

Materials 2018, 11(12), 2474; https://doi.org/10.3390/ma11122474 - 05 Dec 2018

Cited by 4 | Viewed by 3398

Abstract

Fluoropolymers play an essential role in electrowetting (EW) systems. However, no fluoropolymer possesses the desirable properties of both hydrophobicity and dielectric strength. In this study, for the first time, we report the integration of two representative fluoropolymers—namely, Teflon AF (AF 1600X) and Cytop [...] Read more.

Fluoropolymers play an essential role in electrowetting (EW) systems. However, no fluoropolymer possesses the desirable properties of both hydrophobicity and dielectric strength. In this study, for the first time, we report the integration of two representative fluoropolymers—namely, Teflon AF (AF 1600X) and Cytop (Cytop 809A)—into one bifunctionalized dielectric nanolayer. Within this nanolayer, both the superior hydrophobicity of Teflon AF and the excellent dielectric strength of Cytop were able to be retained. Each composed of a 0.5 μm Cytop bottom layer and a 0.06 μm Teflon AF top layer, the fabricated composite nanolayers showed a high withstand voltage of ~70 V (a dielectric strength of 125 V/μm) and a high water contact angle of ~120°. The electrowetting and dielectric properties of various film thicknesses were also systemically investigated. Through detailed study, it was observed that the thicker Teflon AF top layers produced no obvious enhancement of the Cytop/Teflon AF stack. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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10 pages, 2723 KiB

Open AccessArticle

Ultralow Interlayer Friction of Layered Electride Ca₂N: A Potential Two-Dimensional Solid Lubricant Material

by Jianjun Wang, Lin Li, Ziting Shen, Peng Guo, Meng Li, Bin Zhao, Lili Fang and Linfeng Yang

Materials 2018, 11(12), 2462; https://doi.org/10.3390/ma11122462 - 04 Dec 2018

Cited by 15 | Viewed by 3317

Abstract

Dispersion-corrected density functional theory (DFT) calculations reveal that the layered electride of dicalcium nitride (Ca₂N) exhibits stronger interlayer binding interactions but lower interlayer friction behavior than that of traditional layered lubricants weakly bonded by van der Waals (vdW) interactions, such as [...] Read more.

Dispersion-corrected density functional theory (DFT) calculations reveal that the layered electride of dicalcium nitride (Ca₂N) exhibits stronger interlayer binding interactions but lower interlayer friction behavior than that of traditional layered lubricants weakly bonded by van der Waals (vdW) interactions, such as graphite, h-BN, and MoS₂. These results are attributed to the two-dimensional (2D) homogeneous conduction electrons distribution in the middle of the interlayer space of Ca₂N, which yields a smooth sliding barrier and hence ultralow friction behavior. The interesting results obtained in this study have not only broadened the scope of 2D solid lubricants but also enriched the physical understanding of ultralow friction mechanism for 2D systems. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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11 pages, 1914 KiB

Open AccessArticle

Hydrothermally Synthesized Mg-Based Spinel Nanoferrites: Phase Formation and Study on Magnetic Features and Microwave Characteristics

by Chien-Yie Tsay, Yi-Chun Chiu and Chien-Ming Lei

Materials 2018, 11(11), 2274; https://doi.org/10.3390/ma11112274 - 14 Nov 2018

Cited by 20 | Viewed by 4583

Abstract

Three kinds of magnesium-based spinel nanoferrites with the chemical formulas of MgFe₂O₄ (Mg ferrite), Mg_0.9Mn_0.1Fe₂O₄ (Mg-Mn ferrite), and Mg_0.9Mn_0.1In_0.1Fe_1.9O₄ (Mg-Mn-In ferrite) were synthesized by [...] Read more.

Three kinds of magnesium-based spinel nanoferrites with the chemical formulas of MgFe₂O₄ (Mg ferrite), Mg_0.9Mn_0.1Fe₂O₄ (Mg-Mn ferrite), and Mg_0.9Mn_0.1In_0.1Fe_1.9O₄ (Mg-Mn-In ferrite) were synthesized by hydrothermal route. We report the composition-dependent magnetic parameters and microwave properties of Mg-based ferrite nanoparticles. XRD results revealed that the Mg-based ferrite nanoparticles exhibited a cubic spinel structure and had an average nanocrystallite size in the range of 5.8–2.6 nm. Raman spectroscopy analysis confirmed the formation of cubic-spinel phase Mg-based nanoferrites. The room-temperature magnetization measurements indicated that the Mg ferrite nanoparticles had superparamagnetic behavior; whereas the Mg-Mn and Mg-Mn-In ferrite nanoparticles exhibited a paramagnetic nature. The microwave properties of obtained ferrite nanoparticles were studied by alternating current (AC) magnetic susceptibility measurement and electron paramagnetic resonance (EPR) spectroscopy. It was found that the un-substituted Mg ferrite sample exhibited microwave characteristics better than those of the Mn substituted and Mn-In co-substituted Mg ferrite samples. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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16 pages, 6426 KiB

Open AccessArticle

Rapid Solar-Light Driven Superior Photocatalytic Degradation of Methylene Blue Using MoS₂-ZnO Heterostructure Nanorods Photocatalyst

by Ritika, Manjot Kaur, Ahmad Umar, Surinder Kumar Mehta, Surinder Singh, Sushil Kumar Kansal, H. Fouad and Othman Y. Alothman

Materials 2018, 11(11), 2254; https://doi.org/10.3390/ma11112254 - 12 Nov 2018

Cited by 77 | Viewed by 7348

Abstract

Herein, MoS₂-ZnO heterostructure nanorods were hydrothermally synthesized and characterized in detail using several compositional, optical, and morphological techniques. The comprehensive characterizations show that the synthesized MoS₂/ZnO heterostructure nanorods were composed of wurtzite hexagonal phase of ZnO and rhombohedral phase [...] Read more.

Herein, MoS₂-ZnO heterostructure nanorods were hydrothermally synthesized and characterized in detail using several compositional, optical, and morphological techniques. The comprehensive characterizations show that the synthesized MoS₂/ZnO heterostructure nanorods were composed of wurtzite hexagonal phase of ZnO and rhombohedral phase of MoS₂. The synthesized MoS₂/ZnO heterostructure nanorods were used as a potent photocatalyst for the decomposition of methylene blue (MB) dye under natural sunlight. The prepared MoS₂/ZnO heterostructure nanorods exhibited ~97% removal of MB in the reaction time of 20 min with the catalyst amount of 0.15 g/L. The kinetic study revealed that the photocatalytic removal of MB was found to be in accordance with pseudo first-order reaction kinetics with an obtained rate constant of 0.16262 min⁻¹. The tremendous photocatalytic performance of MoS₂-ZnO heterostructure nanorods could be accredited to an effective charge transportation and inhibition in the recombination of photo-excited charge carriers at an interfacial heterojunction. The contribution of active species towards the decomposition of MB using MoS₂-ZnO heterostructure nanorods was confirmed from scavenger study and terephthalic acid fluorescence technique. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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10 pages, 5572 KiB

Open AccessArticle

Enhanced Ferroelectric and Piezoelectric Properties of (1−x)PMN-xPT Ceramics Based on a Partial Oxalate Process

by Jinhwan Kim, Sanghyun Yoon, Jae-Hoon Ji, Young-Ho Ko, Kyung-Ho Cho, Sang-Kwon Lee and Jung-Hyuk Koh

Materials 2018, 11(11), 2247; https://doi.org/10.3390/ma11112247 - 12 Nov 2018

Cited by 5 | Viewed by 3582

Abstract

The pyrochlore phase in ferroelectric and piezoelectric materials is the main obstacle device application due to its poor electrical properties. Especially, the pyrochlore phase is frequently observed in the perovskite-based metal-oxide materials including piezoelectric and ferroelectric ceramics, which are based on solid-state reaction [...] Read more.

The pyrochlore phase in ferroelectric and piezoelectric materials is the main obstacle device application due to its poor electrical properties. Especially, the pyrochlore phase is frequently observed in the perovskite-based metal-oxide materials including piezoelectric and ferroelectric ceramics, which are based on solid-state reaction methods for fabrication. To overcome these problems, advanced innovative methods such as partial oxalate process will be investigated. In this method, crystalized magnesium niobite (MN) and lead titanate (PT) powders will be coated with a certain amount of lead oxalate and, then, the calcination process can be carried out to form the PMN-PT without pyrochlore phase. In this study, (1−x)PMN-xPT ceramics near the morphotropic phase boundary (MPB), with compositions of x = 0.25–0.40, have been prepared employing the partial oxalate method at various temperatures. The crystalline, microstructure, and piezoelectric properties of (1−x)PMN-xPT ceramics depending on the sintering temperature were intensively investigated and discussed. By optimizing the sintering temperature and compositions from the PMN-PT ceramics, the maximum value of the piezoelectric charge coefficient (d₃₃) of 665pC/N, planar electromechanical coupling factor (k_p) of 77.8%, dielectric constant (ε_r) of 3230, and remanent polarization (P_r) of 31.67 μC/cm² were obtained. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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9 pages, 3987 KiB

Open AccessArticle

Piezoelectric Energy Generators Based on Spring and Inertial Mass

by Sanghyun Yoon, Jinhwan Kim, Kyung-Ho Cho, Young-Ho Ko, Sang-Kwon Lee and Jung-hyuk Koh

Materials 2018, 11(11), 2163; https://doi.org/10.3390/ma11112163 - 01 Nov 2018

Cited by 5 | Viewed by 3348

Abstract

In this study, inertial mass-based piezoelectric energy generators with and without a spring were designed and tested. This energy harvesting system is based on the shock absorber, which is widely used to protect humans or products from mechanical shock. Mechanical shock energies, which [...] Read more.

In this study, inertial mass-based piezoelectric energy generators with and without a spring were designed and tested. This energy harvesting system is based on the shock absorber, which is widely used to protect humans or products from mechanical shock. Mechanical shock energies, which were applied to the energy absorber, were converted into electrical energies. To design the energy harvester, an inertial mass was introduced to focus the energy generating position. In addition, a spring was designed and tested to increase the energy generation time by absorbing the mechanical shock energy and releasing a decreased shock energy over a longer time. Both inertial mass and the spring are the key design parameters for energy harvesters as the piezoelectric materials, Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ piezoelectric ceramics were employed to store and convert the mechanical force into electric energy. In this research, we will discuss the design and performance of the energy generator system based on shock absorbers. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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9 pages, 2132 KiB

Open AccessArticle

In Situ Vapor Polymerization of Poly(3,4-ethylenedioxythiophene) Coated SnO₂-Fe₂O₃ Continuous Electrospun Nanotubes for Rapid Detection of Iodide Ions

by Xiuru Xu, Wei Wang, Bolun Sun, Xue Zhang, Rui Zhao and Ce Wang

Materials 2018, 11(11), 2084; https://doi.org/10.3390/ma11112084 - 24 Oct 2018

Cited by 3 | Viewed by 3004

Abstract

In this work poly(3,4-ethylenedioxythiophene) (PEDOT) coated SnO₂-Fe₂O₃ continuous nanotubes with a uniform core–shell structure have been demonstrated for rapid sensitive detection of iodide ions. The SnO₂-Fe₂O₃ nanotubes were firstly fabricated via an electrospinning [...] Read more.

In this work poly(3,4-ethylenedioxythiophene) (PEDOT) coated SnO₂-Fe₂O₃ continuous nanotubes with a uniform core–shell structure have been demonstrated for rapid sensitive detection of iodide ions. The SnO₂-Fe₂O₃ nanotubes were firstly fabricated via an electrospinning technique and following calcination process. An in situ polymerization approach was then performed to coat a uniform PEDOT shell on the surface of as-prepared SnO₂-Fe₂O₃ nanotubes by vapor phase polymerization, using Fe₂O₃ on the surface of nanotubes as an oxidant in an acidic condition. The resultant PEDOT@SnO₂-Fe₂O₃ core-shell nanotubes exhibit a fast response time (~4 s) toward iodide ion detection and a linear current response ranging from 10 to 100 μM, with a detection limit of 1.5 μM and sensitivity of 70 μA/mM/cm². The facile fabrication process and high sensing performance of this study can promote a wide range of potential applications in human health monitoring and biosensing systems. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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13 pages, 4962 KiB

Open AccessArticle

Functionalization of Silk with In-Situ Synthesized Platinum Nanoparticles

by Fan Zou, Ji Zhou, Jin Zhang, Jingliang Li, Bin Tang, Wu Chen, Jinfeng Wang and Xungai Wang

Materials 2018, 11(10), 1929; https://doi.org/10.3390/ma11101929 - 10 Oct 2018

Cited by 21 | Viewed by 4129

Abstract

After platinum nanoparticles (PtNPs) were in-situ synthesized on silk fabrics through heat treatment, it was determined that the treatment of the silk fabrics with PtNPs imparted multiple functions, including coloring, catalysis, and antibacterial activity. The formation of PtNPs on fabrics was affected by [...] Read more.

After platinum nanoparticles (PtNPs) were in-situ synthesized on silk fabrics through heat treatment, it was determined that the treatment of the silk fabrics with PtNPs imparted multiple functions, including coloring, catalysis, and antibacterial activity. The formation of PtNPs on fabrics was affected by the Pt ion concentration, pH value of solution, and reaction temperature. Acidic condition and high temperature were found to facilitate the formation of PtNPs on silk. The color strength of silk fabrics increased with the concentration of Pt ions. The PtNP treated silk fabrics exhibited reasonably good washing color fastness and excellent rubbing color fastness. The morphologies and chemical components of the treated silk fabrics were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. The PtNP treated silk fabric exhibited significant catalytic function and a notable antibacterial effect against Escherichia coli (E. coli). Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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16 pages, 4988 KiB

Open AccessArticle

In Situ Generation of Fluorescent Copper Nanoclusters Embedded in Monolithic Eggshell Membrane: Properties and Applications

by Lu Li, Min Huang, Xianhu Liu, Dengming Sun and Congying Shao

Materials 2018, 11(10), 1913; https://doi.org/10.3390/ma11101913 - 09 Oct 2018

Cited by 11 | Viewed by 3788

Abstract

Luminescent metal nanoclusters have attracted considerable research attention in recent years due to their unique properties and extensive usage in many fields. Three different synthetic routes were developed to in situ generate orange and red emitting copper nanoclusters embedded in monolithic eggshell membrane [...] Read more.

Luminescent metal nanoclusters have attracted considerable research attention in recent years due to their unique properties and extensive usage in many fields. Three different synthetic routes were developed to in situ generate orange and red emitting copper nanoclusters embedded in monolithic eggshell membrane (Cu NCs@ESM) using different reducing reagents including N₂H₄·H₂O, NH₂OH·HCl and Vitamin C at room temperature for the first time. The routes are extremely facile, low-cost and versatile. The obtained Cu NCs@ESM nanocomposites exhibit excellent photostability and chemical stability, laying the foundation for various practical applications. Fluorescent surface patterning was demonstrated based on the proposed strategy easily. Significantly, the Cu NCs@ESM shows selective fluorescence quenching response to Hg²⁺ ions and good catalytic activity for methylene blue (MB) reduction degradation making it ideal as portable sensing strip and recyclable catalyst. The work provides a general strategy for the fabrication of other various monolithic nanomaterials with potential applications. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 3681 KiB

Open AccessArticle

Magnetic and Mössbauer Spectroscopy Studies of Zinc-Substituted Cobalt Ferrites Prepared by the Sol-Gel Method

by Qing Lin, Jianmei Xu, Fang Yang, Jinpei Lin, Hu Yang and Yun He

Materials 2018, 11(10), 1799; https://doi.org/10.3390/ma11101799 - 21 Sep 2018

Cited by 46 | Viewed by 3906

Abstract

Zinc ion-substituted cobalt ferrite powders Co_1−xZn_xFe₂O₄ (x = 0–0.7) were prepared by the sol-gel auto-combustion process. The structural properties and magnetic of the samples were investigated with X-ray diffraction (XRD), superconducting quantum interference device, [...] Read more.

Zinc ion-substituted cobalt ferrite powders Co_1−xZn_xFe₂O₄ (x = 0–0.7) were prepared by the sol-gel auto-combustion process. The structural properties and magnetic of the samples were investigated with X-ray diffraction (XRD), superconducting quantum interference device, and a Mössbauer spectrometer. The results of XRD showed that the powder of a single cubic phase of ferrites calcined when kept at 800 °C for 3 h. The lattice constant increases with increase in Zn concentration, but average crystallite size does not decrease constantly by increasing the zinc content, which is related to pH value. It was confirmed that the transition from ferrimagnetic to superparamagnetic behaviour depends on increasing zinc concentration by Mössbauer spectra at room temperature. Magnetization at room temperature increases for x ≤ 0.3, but decreases for increasing Zn²⁺ ions. The magnetization of Co_0.7Zn_0.3Fe₂O₄ reached maximum value (83.51 emu/g). The coercivity decreased with Zn²⁺ ions, which were doped on account of the decrease of the anisotropy constant. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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9 pages, 2935 KiB

Open AccessArticle

Enhanced Photoelectrochemical Properties of Ti³⁺ Self-Doped Branched TiO₂ Nanorod Arrays with Visible Light Absorption

by Jingyang Wang, Xiantao Wang, Jun Yan, Qi Tan, Guijie Liang, Shaohua Qu and Zhicheng Zhong

Materials 2018, 11(10), 1791; https://doi.org/10.3390/ma11101791 - 20 Sep 2018

Cited by 7 | Viewed by 4035

Abstract

A novel Ti³⁺ self-doped branched rutile TiO₂ nanorod arrays (NRAs) was successfully grown on an F-doped tin oxide (FTO) transparent conductive glass by a combined hydrothermal and magnetron sputtering method. Surface morphology, structure, optical properties, and photoelectrochemical behavior of the branched [...] Read more.

A novel Ti³⁺ self-doped branched rutile TiO₂ nanorod arrays (NRAs) was successfully grown on an F-doped tin oxide (FTO) transparent conductive glass by a combined hydrothermal and magnetron sputtering method. Surface morphology, structure, optical properties, and photoelectrochemical behavior of the branched TiO₂ NRAs are determined. Using TiO₂ nanoparticles (NPs) deposited on the top of the nanorods as seeds, TiO₂ nanobranches can easily grow on the top of the nanorods. Moreover, the Ti³⁺ defects in the TiO₂ NPs and associated oxygen vacancies, and the nanobranches expend the optical absorption edge of the TiO₂ NRAs from 400 nm to 510 nm. Branched TiO₂ NRAs exhibit excellent photoelectrochemical properties compared to the pure TiO₂ NRAs, as revealed by photoelectrochemical measurements. This enhanced photoelectrochemical properties is induced by the increased surface area and expanded optical absorption range. Due to their favorable characteristics, these novel branched TiO₂ NRAs will provide a new path to the fabrication of hierarchical nanostructured materials. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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19 pages, 8087 KiB

Open AccessArticle

Thin Electric Heating Membrane Constructed with a Three-Dimensional Nanofibrillated Cellulose–Graphene–Graphene Oxide System

by Chuang Shao, Zhenyu Zhu, Chuwang Su, Sheng Yang and Quanping Yuan

Materials 2018, 11(9), 1727; https://doi.org/10.3390/ma11091727 - 14 Sep 2018

Cited by 17 | Viewed by 3983

Abstract

Nanofibrillated cellulose (NFC) and graphene oxide (GO) with reinforcing and film-forming properties were employed with graphene to develop a novel and thin electric heating membrane with heat dissipation controllability. A negative charge was found on the surface of GO and NFC in aqueous [...] Read more.

Nanofibrillated cellulose (NFC) and graphene oxide (GO) with reinforcing and film-forming properties were employed with graphene to develop a novel and thin electric heating membrane with heat dissipation controllability. A negative charge was found on the surface of GO and NFC in aqueous dispersions, which contributed to the homogeneous distribution of the graphene sheets. The membrane had a good laminated structure with three-dimensional interaction between GO and NFC, with embedded graphene sheets. Conductivity was characterized as a function of the amount of graphene, thus giving control over to the heating power by adjusting the ratio of graphene. Subsequent electric heating tests can remove irregularities on the GO and graphene sheet, improving the laminated structure further. The temperature on the surface of the membrane presented an exponential increasing regularity with time. Under the same power density and time, the stabilized temperature rise of membranes was higher when grammage was higher, which was characterized by the linear function of the power density. Low-grammage membranes (1 and 4 g·m⁻²) also exhibited regular and even stabilized temperature rises. The indicated structure and heating performance of the membrane, as well as the variation induced by Joule heating, would drive its applications. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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15 pages, 4186 KiB

Open AccessArticle

Composition, Structure and Morphology Evolution of Octadecylamine (ODA)–Reduced Graphene Oxide and Its Dispersion Stability under Different Reaction Conditions

by Tianjiao Bao, Zhiyong Wang, Yan Zhao, Yan Wang and Xiaosu Yi

Materials 2018, 11(9), 1710; https://doi.org/10.3390/ma11091710 - 13 Sep 2018

Cited by 15 | Viewed by 4098

Abstract

Octadecylamine (ODA) can solve the aggregation problem of graphene sheets in the chemical exfoliation method. However, no attempts have been made to investigate the evolution of ODA–reduced graphene oxide (ORGO) with reaction conditions and the modification mechanism, which is the core problem to [...] Read more.

Octadecylamine (ODA) can solve the aggregation problem of graphene sheets in the chemical exfoliation method. However, no attempts have been made to investigate the evolution of ODA–reduced graphene oxide (ORGO) with reaction conditions and the modification mechanism, which is the core problem to realize the controllable production and practical application of graphene. In this study, we treated graphene oxide (GO) with ODA under different reaction conditions to prepare ORGO. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, thermogravimetric analysis (TGA), and UV–vis spectrophotometry were employed to analyze the composition, structure, morphology and characteristics of the as–prepared graphene sheets. The results showed that the reduction reaction could occur under mild conditions, but the edge grafting reaction could only be activated by a higher temperature. Moreover, the ORGO created at 80 °C for 5 h and 120 °C for 0.5 h exhibited the optimized properties, both excellent dispersing stability and high heat resisting property, since they had more edge grafting chains and a suitable reduction degree. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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14 pages, 6694 KiB

Open AccessArticle

Fabrication of Mo-Doped WO₃ Nanorod Arrays on FTO Substrate with Enhanced Electrochromic Properties

by Bao Wang, Wenkuan Man, Haiyang Yu, Yang Li and Feng Zheng

Materials 2018, 11(9), 1627; https://doi.org/10.3390/ma11091627 - 05 Sep 2018

Cited by 17 | Viewed by 4085

Abstract

Well-oriented and crystalline WO₃ nanorod arrays (WNRAs) decorated with Mo were synthesized on fluorine doped tin oxide (FTO) substrate by the hydrothermal method. The effects of Mo doping, hydrothermal reaction time, and hydrothermal temperature on the morphologies and electrochromic properties of as-prepared [...] Read more.

Well-oriented and crystalline WO₃ nanorod arrays (WNRAs) decorated with Mo were synthesized on fluorine doped tin oxide (FTO) substrate by the hydrothermal method. The effects of Mo doping, hydrothermal reaction time, and hydrothermal temperature on the morphologies and electrochromic properties of as-prepared WNRAs were studied thoroughly. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and chronoamperometry techniques were used to characterize the structures and properties of obtained WNRAs. The results demonstrate that the average diameter of the as-prepared WNRAs ranged from 30 to 70 nm. During the decoration of Mo on the WNRAs, the growth density of as-prepared WNRAs decreased and the surfaces became rough. However, the decorated Mo on WNRAs synthesized at 180 °C for 5 h with a Mo/W mole ratio of 1:40 exhibited better electrochromic properties than single WNRAs. They exhibited high optical modulation (61.7%), fast bleaching/coloring response times (3 s/9 s), high coloration efficiency values (73.1 cm²/C), and good cycling stability. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 3690 KiB

Open AccessArticle

Synergistic Enhancement of Thermal Conductivity and Dielectric Properties in Al₂O₃/BaTiO₃/PP Composites

by Junlong Yao, Li Hu, Min Zhou, Feng You, Xueliang Jiang, Lin Gao, Qing Wang, Zhengguang Sun and Jun Wang

Materials 2018, 11(9), 1536; https://doi.org/10.3390/ma11091536 - 26 Aug 2018

Cited by 27 | Viewed by 5346

Abstract

Multifunctional polymer composites with both high dielectric constants and high thermal conductivity are urgently needed by high-temperature electronic devices and modern microelectromechanical systems. However, high heat-conduction capability or dielectric properties of polymer composites all depend on high-content loading of different functional thermal-conductive or [...] Read more.

Multifunctional polymer composites with both high dielectric constants and high thermal conductivity are urgently needed by high-temperature electronic devices and modern microelectromechanical systems. However, high heat-conduction capability or dielectric properties of polymer composites all depend on high-content loading of different functional thermal-conductive or high-dielectric ceramic fillers (every filler volume fraction ≥ 50%, i.e., f_filler ≥ 50%), and an overload of various fillers (f_{thermal-conductive} _filler + f_{high-dielectric} _filler > 50%) will decrease the processability and mechanical properties of the composite. Herein, series of alumina/barium titanate/polypropylene (Al₂O₃/BT/PP) composites with high dielectric- and high thermal-conductivity properties are prepared with no more than 50% volume fraction of total ceramic fillers loading, i.e., f_fillers ≤ 50%. Results showed the thermal conductivity of the Al₂O₃/BT/PP composite is up to 0.90 W/m·K with only 10% thermal-conductive Al₂O₃ filler, which is 4.5 times higher than the corresponding Al₂O₃/PP composites. Moreover, higher dielectric strength (E_b) is also found at the same loading, which is 1.6 times higher than PP, and the Al₂O₃/BT/PP composite also exhibited high dielectric constant (

ε_{r}

= 18 at 1000 Hz) and low dielectric loss (tan δ ≤ 0.030). These excellent performances originate from the synergistic mechanism between BaTiO₃ macroparticles and Al₂O₃ nanoparticles. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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11 pages, 2474 KiB

Open AccessArticle

Dielectric Properties and Switching Processes of Barium Titanate–Barium Zirconate Ferroelectric Superlattices

by Alexander Sidorkin, Lolita Nesterenko, Yaovi Gagou, Pierre Saint-Gregoire, Eugeniy Vorotnikov and Nadezhda Popravko

Materials 2018, 11(8), 1436; https://doi.org/10.3390/ma11081436 - 14 Aug 2018

Cited by 5 | Viewed by 3636

Abstract

This article is devoted to the investigation of the dielectric and repolarization properties of barium zirconate and barium titanate BaZrO₃/BaTiO₃ superlattices with a period of 13.322 nm on a monocrystal magnesium oxide (MgO) substrate. Synthesized superlattices demonstrated a ferroelectric phase [...] Read more.

This article is devoted to the investigation of the dielectric and repolarization properties of barium zirconate and barium titanate BaZrO₃/BaTiO₃ superlattices with a period of 13.322 nm on a monocrystal magnesium oxide (MgO) substrate. Synthesized superlattices demonstrated a ferroelectric phase transition at a temperature of approximately 393 °C, which is far higher than the Curie temperature of BaTiO₃ thin films and bulk samples. The dielectric permittivity of the superlattice reached more than 10⁴ at maximum. As the electric field frequency increased, the dielectric constant of the studied superlattice decreased over the entire study temperature range, but position of the maximum dielectric constant remained the same with changing frequency. The temperature dependence of the inverse dielectric permittivity 1/ε(T) for the studied samples shows that, in the investigated superlattice, both Curie–Weiss law and the law of “two” were followed. Additionally, the ε(T) dependences showed practically no temperature hysteresis with heating and cooling. Samples of synthesized superlattices had a relatively small internal bias field, which was directed from the superlattice towards the substrate. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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16 pages, 8177 KiB

Open AccessArticle

Removal of Zinc Ions Using Hydroxyapatite and Study of Ultrasound Behavior of Aqueous Media

by Simona Liliana Iconaru, Mikael Motelica-Heino, Régis Guegan, Mihai Valentin Predoi, Alina Mihaela Prodan and Daniela Predoi

Materials 2018, 11(8), 1350; https://doi.org/10.3390/ma11081350 - 03 Aug 2018

Cited by 24 | Viewed by 3486

Abstract

The present study demonstrates the effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions. The synthesized hydroxyapatites before (HAp) and after the adsorption of zinc (at a concentration of 50 mg/L) in solution (HApD) were characterized using X-ray diffraction (XRD), [...] Read more.

The present study demonstrates the effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions. The synthesized hydroxyapatites before (HAp) and after the adsorption of zinc (at a concentration of 50 mg/L) in solution (HApD) were characterized using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM, respectively). The effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions was stressed out through ultrasonic measurements. Both Langmuir and Freundlich models properly fitted on a wide range of concentration the equilibrium adsorption isotherms, allowing us to precisely quantify the affinity of zinc to hydroxyapatite nanopowders and to probe the efficacy of hydroxyapatite in removal of zinc ions from aqueous solutions in ultrasonic conditions. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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15 pages, 4206 KiB

Open AccessArticle

Research on Grain Refinement Mechanism of 6061 Aluminum Alloy Processed by Combined SPD Methods of ECAP and MAC

by Zhenwei Zhang, Junli Wang, Qinglong Zhang, Supeng Zhang, Qingnan Shi and Huarong Qi

Materials 2018, 11(7), 1246; https://doi.org/10.3390/ma11071246 - 20 Jul 2018

Cited by 19 | Viewed by 4525

Abstract

Equal channel angular pressing (ECAP) and multi-axial compression deformation (MAC) are severe plastic deformation (SPD) processes that produce bulk nanostructured materials with ultrafine grains. The grains could be observably refined by multi-pass of ECAP and MAC. This research proposed new routes of cyclic [...] Read more.

Equal channel angular pressing (ECAP) and multi-axial compression deformation (MAC) are severe plastic deformation (SPD) processes that produce bulk nanostructured materials with ultrafine grains. The grains could be observably refined by multi-pass of ECAP and MAC. This research proposed new routes of cyclic equal channel compression (CECC), which combines ECAP and MAC to increase the mechanical properties of 6061 aluminum alloy. The tests, which are conducted through electron backscattered diffraction (EBSD) and transmission electron microscope (TEM), were performed on the grain size, recrystallization distribution, misorientation distributions, dislocations, and secondary phase distributions of CECC-processed 6061 aluminum alloys on the purpose of exploring the mechanism of grain refinement. MEM is the short form for the CECC processing route of MAC + ECAP + MAC, which is one ECAP pass between two MAC passes. The tests results showed that the average grain size could reach to as much as 1.1 μm after two MEM deformation circles named MEM-MEM, with the non-annealing average grain size being 21 μm and recrystallization annealed average grain size being 28 μm. The dislocation cells, which could be transformed into sub-grains with the increase of the strain, were formed by the slip and the accumulation of dislocations. The secondary phase was Mg₂Si, which could prevent the refined grains from growing up again by pinning at the grain boundaries. Above all, the dislocation proliferation and secondary phases will both lead to the grain refinement. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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14 pages, 4449 KiB

Open AccessArticle

Preparation and Characterization of AgNPs In Situ Synthesis on Polyelectrolyte Membrane Coated Sericin/Agar Film for Antimicrobial Applications

by Liying Liu, Rui Cai, Yejing Wang, Gang Tao, Lisha Ai, Peng Wang, Meirong Yang, Hua Zuo, Ping Zhao, Hong Shen, Ahmad Umar and Huawei He

Materials 2018, 11(7), 1205; https://doi.org/10.3390/ma11071205 - 13 Jul 2018

Cited by 23 | Viewed by 4202

Abstract

Antibacterial materials are of great importance in preventing bacterial adhesion and reproduction in daily life. Silver nanoparticle (AgNP) is a broad-spectrum antibacterial nanomaterial that has attracted significant attentions for its ability to endow natural materials with antibacterial ability. Silk sericin (SS) has a [...] Read more.

Antibacterial materials are of great importance in preventing bacterial adhesion and reproduction in daily life. Silver nanoparticle (AgNP) is a broad-spectrum antibacterial nanomaterial that has attracted significant attentions for its ability to endow natural materials with antibacterial ability. Silk sericin (SS) has a great advantage for biomaterial application, as it is a natural protein with excellent hydrophilicity and biodegradability. In this study, we prepared AgNPs and polyelectrolyte membrane (PEM) modified SS/Agar films through the layer-by-layer adsorption technique and ultraviolet-assisted AgNPs synthesis method. The film was well characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy. Other properties such as water contact angle, wettability and tensile strength, the release of silver were also studied. The antimicrobial activity of AgNPs-PEM-SS/Agar film was investigated against Escherichia coli and Staphylococcus aureus as the model microorganisms by the inhibition zone and bacterial growth curve assays. The results suggested that the AgNPs-PEM-SS/Agar film had excellent mechanical performance, high hydrophilicity, prominent water absorption ability, as well as outstanding and durable antibacterial activity. Therefore, the prepared novel AgNPs-PEM-SS/Agar composite film is proposed as a potentially favorable antibacterial biomaterial for biomedical applications. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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15 pages, 4632 KiB

Open AccessArticle

Titanium Oxide (TiO₂)/Polymethylmethacrylate (PMMA) Denture Base Nanocomposites: Mechanical, Viscoelastic and Antibacterial Behavior

by Ali Alrahlah, H. Fouad, Mohamed Hashem, Abdurahman A. Niazy and Abdulhakim AlBadah

Materials 2018, 11(7), 1096; https://doi.org/10.3390/ma11071096 - 27 Jun 2018

Cited by 61 | Viewed by 5353

Abstract

Currently, polymethylmethacrylate (PMMA) is the most popular denture base material. Most fractures of dentures that occur during function are due to its insufficient mechanical strength. The major drawbacks of PMMA are insufficient ductility, strength, and viscoelastic behavior. The purpose of this study was [...] Read more.

Currently, polymethylmethacrylate (PMMA) is the most popular denture base material. Most fractures of dentures that occur during function are due to its insufficient mechanical strength. The major drawbacks of PMMA are insufficient ductility, strength, and viscoelastic behavior. The purpose of this study was to evaluate a polymethylmethacrylate denture base material modified with TiO₂ nanoparticles in terms of nanomechanical, creep-recovery, and relaxation. Additionally, the effects of addition TiO₂ nanoparticles on the thermal and antimicrobial adhesion behaviors were investigated. Differential scanning calorimetry and thermogravimetric analysis indicated that the effect of small amounts of TiO₂ nanoparticles (1 wt. %, 2 wt. %, and 3 wt. %) on the degradation behavior of PMMA denture bases was insignificant. The nanomechanical test results of the PMMA and PMMA/TiO₂ nanocomposites indicated that the hardness and modulus in the nanoscale range improved due to TiO₂ addition. At a 1200-nm penetration depth, the modulus increased by 10%, 16%, and 29% and hardness increased by 18%, 24%, and 35% with the addition of 1 wt. %, 2 wt. %, and 3 wt. % TiO₂, respectively. Furthermore, the creep-recovery and relaxation behaviors of PMMA were significantly improved due to the addition of TiO₂. The creep strain decreased from 1.41% to 1.06%, 0.66%, and 0.49% with the addition of 1 wt. %, 2 wt. %, and 3 wt. % TiO₂, respectively. The relaxation test results showed that the initial stress under 1% strain improved to 19.9, 21.2, and 22 MPa with the addition of 1 wt. %, 2 wt. %, and 3 wt. % TiO₂, respectively. The improvement in the nanohardness, modulus, creep recovery, and relaxation behavior of PMMA due to the addition of TiO₂ nanoparticles indicated the role of the nanoparticles in increasing the PMMA matrix stiffness by reducing its mobility and free volume. TiO₂ nanoparticles also improved the antimicrobial behavior of PMMA by significantly reducing bacterial adherence with increasing TiO₂ ratio. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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10 pages, 2538 KiB

Open AccessFeature PaperArticle

A Study of Quantum Confinement Effects in Ultrathin NiO Films Performed by Experiment and Theory

by Christos S. Garoufalis, Alexandros Barnasas, Alkeos Stamatelatos, Vagelis Karoutsos, Spyridon Grammatikopoulos, Panagiotis Poulopoulos and Sotirios Baskoutas

Materials 2018, 11(6), 949; https://doi.org/10.3390/ma11060949 - 04 Jun 2018

Cited by 20 | Viewed by 4137

Abstract

Ultrathin NiO films in the thickness range between 1 and 27 nm have been deposited on high-quality quartz substrates by direct magnetron sputtering under a rough vacuum with a base pressure of 2 × 10⁻² mbar. The sputtering target was metallic Ni; [...] Read more.

Ultrathin NiO films in the thickness range between 1 and 27 nm have been deposited on high-quality quartz substrates by direct magnetron sputtering under a rough vacuum with a base pressure of 2 × 10⁻² mbar. The sputtering target was metallic Ni; however, due to the rough vacuum a precursor material was grown in which most of Ni was already oxidized. Subsequent short annealing at temperatures of about 600 °C in a furnace in air resulted in NiO with high crystallinity quality, as atomic force microscopy revealed. The images of surface morphology showed that the NiO films were continuous and follow a normal grain growth mode. UV-Vis light absorption spectroscopy experiments have revealed a blue shift of the direct band gap of NiO. The band gap was determined either by Tauc plots (onset) or by the derivative method (highest rate of absorbance increase just after the onset). The experimental results are interpreted as evidences of quantum confinement effects. Theoretical calculations based on Hartree Fock approximation as applied for an electron-hole system, in the framework of effective mass approximation were carried out. The agreement between theory and experiment supports the quantum confinement interpretation. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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14 pages, 3016 KiB

Open AccessArticle

In Vitro Evaluation of 2D-Printed Edible Films for the Buccal Delivery of Diclofenac Sodium

by Georgios K. Eleftheriadis, Paraskevi Kyriaki Monou, Nikolaos Bouropoulos and Dimitrios G. Fatouros

Materials 2018, 11(5), 864; https://doi.org/10.3390/ma11050864 - 22 May 2018

Cited by 22 | Viewed by 3783

Abstract

Printing technologies have recently emerged in the development of novel drug delivery systems toward personalized medicine, to improve the performance of formulations, existing bioavailability patterns, and patients’ compliance. In the context of two-dimensional printing, this article presents the development of buccal films that [...] Read more.

Printing technologies have recently emerged in the development of novel drug delivery systems toward personalized medicine, to improve the performance of formulations, existing bioavailability patterns, and patients’ compliance. In the context of two-dimensional printing, this article presents the development of buccal films that are designed to efficiently deliver a class II compound (diclofenac sodium), according to the Biopharmaceutics Classification System (BCS), to the oral cavity. The preparation of drug-loaded inks was carried out based on solubility studies and evaluation of rheological properties, combining ethanol and propylene glycol as optimal solvents. Deposition of the drug was achieved by increasing the number of printing layers onto edible substrates, to produce formulations with dose variance. Thermal analysis, X-ray diffraction, and infrared spectroscopy were used to characterize the developed films. Drug loading and water uptake studies complemented the initial assessment of the films, and preliminary in vitro studies were conducted to further evaluate their performance. The in vitro release profiles were recorded in simulated saliva, presenting the complete release of the incorporated active in a period of 10 min. The effect of multiple layers on the overall performance of films was completed with in vitro permeation studies, revealing the correlation between the number of printed layers and the apparent permeability coefficient. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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13 pages, 3622 KiB

Open AccessArticle

Performance-Enhanced Activated Carbon Electrodes for Supercapacitors Combining Both Graphene-Modified Current Collectors and Graphene Conductive Additive

by Rubing Wang, Yuting Qian, Weiwei Li, Shoupu Zhu, Fengkui Liu, Yufen Guo, Mingliang Chen, Qi Li and Liwei Liu

Materials 2018, 11(5), 799; https://doi.org/10.3390/ma11050799 - 15 May 2018

Cited by 11 | Viewed by 4481

Abstract

Graphene has been widely used in the active material, conductive agent, binder or current collector for supercapacitors, due to its large specific surface area, high conductivity, and electron mobility. However, works simultaneously employing graphene as conductive agent and current collector were rarely reported. [...] Read more.

Graphene has been widely used in the active material, conductive agent, binder or current collector for supercapacitors, due to its large specific surface area, high conductivity, and electron mobility. However, works simultaneously employing graphene as conductive agent and current collector were rarely reported. Here, we report improved activated carbon (AC) electrodes (AC@G@NiF/G) simultaneously combining chemical vapor deposition (CVD) graphene-modified nickel foams (NiF/Gs) current collectors and high quality few-layer graphene conductive additive instead of carbon black (CB). The synergistic effect of NiF/Gs and graphene additive makes the performances of AC@G@NiF/G electrodes superior to those of electrodes with CB or with nickel foam current collectors. The performances of AC@G@NiF/G electrodes show that for the few-layer graphene addition exists an optimum value around 5 wt %, rather than a larger addition of graphene, works out better. A symmetric supercapacitor assembled by AC@G@NiF/G electrodes exhibits excellent cycling stability. We attribute improved performances to graphene-enhanced conductivity of electrode materials and NiF/Gs with 3D graphene conductive network and lower oxidation, largely improving the electrical contact between active materials and current collectors. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 5120 KiB

Open AccessArticle

Controllable Fabrication of Fe₃O₄/ZnO Core–Shell Nanocomposites and Their Electromagnetic Wave Absorption Performance in the 2–18 GHz Frequency Range

by Xiaodong Sun, Guangyan Ma, Xuliang Lv, Mingxu Sui, Huabing Li, Fan Wu and Jijun Wang

Materials 2018, 11(5), 780; https://doi.org/10.3390/ma11050780 - 11 May 2018

Cited by 28 | Viewed by 4155

Abstract

In this study, Fe₃O₄/ZnO core–shell nanocomposites were synthesized through a chemical method of coating the magnetic core (Fe₃O₄) with ZnO by co-precipitation of Fe₃O₄ with zinc acetate in a basic medium of [...] Read more.

In this study, Fe₃O₄/ZnO core–shell nanocomposites were synthesized through a chemical method of coating the magnetic core (Fe₃O₄) with ZnO by co-precipitation of Fe₃O₄ with zinc acetate in a basic medium of ammonium hydroxide. The phase structure, morphology and electromagnetic parameters of the Fe₃O₄/ZnO core–shell nanocomposites were investigated. The results indicated that the concentration of the solvent was responsible for controlling the morphology of the composites, which further influenced their impedance matching and microwave absorption properties. Moreover, Fe₃O₄/ZnO nanocomposites exhibited an enhanced absorption capacity in comparison with the naked Fe₃O₄ nanospheres. Specifically, the minimum reflection loss value reached −50.79 dB at 4.38 GHz when the thickness was 4.5 mm. It is expected that the Fe₃O₄/ZnO core–shell structured nanocomposites could be a promising candidate as high-performance microwave absorbers. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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10 pages, 2657 KiB

Open AccessArticle

Fast Response and Spontaneous Alignment in Liquid Crystals Doped with 12-Hydroxystearic Acid Gelators

by Hui-Chi Lin, Chih-Hung Wang, Jyun-Kai Wang and Sheng-Feng Tsai

Materials 2018, 11(5), 745; https://doi.org/10.3390/ma11050745 - 07 May 2018

Cited by 6 | Viewed by 3514

Abstract

The spontaneous vertical alignment of liquid crystals (LCs) in gelator (12-hydroxystearic acid)-doped LC cells was studied. Gelator-induced alignment can be used in both positive and negative LC cells. The electro-optical characteristics of the gelator-doped negative LC cell were similar to those of an [...] Read more.

The spontaneous vertical alignment of liquid crystals (LCs) in gelator (12-hydroxystearic acid)-doped LC cells was studied. Gelator-induced alignment can be used in both positive and negative LC cells. The electro-optical characteristics of the gelator-doped negative LC cell were similar to those of an LC cell that contained a vertically aligned (VA) host. The rise time of the gelator-doped LC cell was two orders of magnitude shorter than that of the VA host LC cell. The experimental results indicate that the gelator-induced vertical alignment of LC molecules occurred not only on the surface of the indium tin oxide (ITO) but also on the homogeneous alignment layer. Various LC alignments (planar, hybrid, multistable hybrid, and vertical alignments) were achieved by modulating the doped gelator concentrations. The multistable characteristic of LCs doped with the gelator is also presented. The alignment by doping with a gelator reduces the manufacturing costs and provides a means of fabricating fast-responding, flexible LC displays using a low-temperature process. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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18 pages, 52235 KiB

Open AccessArticle

Porous Polyethylene Coated with Functionalized Hydroxyapatite Particles as a Bone Reconstruction Material

by H. Fouad, Randa AlFotawi, Othman Y. Alothman, Basheer A. Alshammari, Musaad Alfayez, Mohamed Hashem and Amer Mahmood

Materials 2018, 11(4), 521; https://doi.org/10.3390/ma11040521 - 29 Mar 2018

Cited by 14 | Viewed by 4650

Abstract

In this study, porous polyethylene scaffolds were examined as bone substitutes in vitro and in vivo in critical-sized calvarial bone defects in transgenic Sprague-Dawley rats. A microscopic examination revealed that the pores appeared to be interconnected across the material, making them suitable for [...] Read more.

In this study, porous polyethylene scaffolds were examined as bone substitutes in vitro and in vivo in critical-sized calvarial bone defects in transgenic Sprague-Dawley rats. A microscopic examination revealed that the pores appeared to be interconnected across the material, making them suitable for cell growth. The creep recovery behavior of porous polyethylene at different loads indicated that the creep strain had two main portions. In both portions, strain increased with increased applied load and temperature. In terms of the thermographic behavior of the material, remarkable changes in melting temperature and heat fusion were revealed with increased the heating rates. The tensile strength results showed that the material was sensitive to the strain rate and that there was adequate mechanical strength to support cell growth. The in vitro cell culture results showed that human bone marrow mesenchymal stem cells attached to the porous polyethylene scaffold. Calcium sulfate–hydroxyapatite (CS–HA) coating of the scaffold not only improved attachment but also increased the proliferation of human bone marrow mesenchymal stem cells. In vivo, histological analysis showed that the study groups had active bone remodeling at the border of the defect. Bone regeneration at the border was also evident, which confirmed that the polyethylene acted as an osteoconductive bone graft. Furthermore, bone formation inside the pores of the coated polyethylene was also noted, which would enhance the process of osteointegration. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 6102 KiB

Open AccessArticle

Synthesis and Characterization of Highly Sensitive Hydrogen (H₂) Sensing Device Based on Ag Doped SnO₂ Nanospheres

by Zhaorui Lu, Qu Zhou, Lingna Xu, Yingang Gui, Zhongyong Zhao, Chao Tang and Weigen Chen

Materials 2018, 11(4), 492; https://doi.org/10.3390/ma11040492 - 26 Mar 2018

Cited by 29 | Viewed by 4101

Abstract

In this paper, pure and Ag-doped SnO₂ nanospheres were synthesized by hydrothermal method and characterized via X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectra (XPS), respectively. The gas sensing performance of the [...] Read more.

In this paper, pure and Ag-doped SnO₂ nanospheres were synthesized by hydrothermal method and characterized via X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectra (XPS), respectively. The gas sensing performance of the pure, 1 at.%, 3 at.%, and 5 at.% Ag-doped SnO₂ sensing devices toward hydrogen (H₂) were systematically evaluated. The results indicated that compared with pure SnO₂ nanospheres, Ag-doped SnO₂ nanospheres could not only decrease the optimum working temperature but also significantly improve H₂ sensing such as higher gas response and faster response-recovery. Among all the samples, the 3 at.% Ag-doped SnO₂ showed the highest response 39 to 100 μL/L H₂ at 300 °C. Moreover, its gas sensing mechanism was discussed, and the results will provide reference and theoretical guidance for the development of high-performance SnO₂-based H₂ sensing devices. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 2968 KiB

Open AccessArticle

3D Graphene-Nitrogen Doped Carbon Nanotubes Network Modified Electrode as Sensing Materials for the Determination of Urapidil

by Yanju Wu, Anxing Zhou, Huimin Yang, Fei Wang and Kui Lu

Materials 2018, 11(2), 322; https://doi.org/10.3390/ma11020322 - 23 Feb 2018

Cited by 4 | Viewed by 4163

Abstract

In this work, a three dimensional (3D) graphene-nitrogen doped carbon nanotubes (G-NCNTs) network was successfully fabricated on the surface of a glassy carbon (GC) electrode using the pulse potential method (PPM) in a graphene oxide-nitrogen doped carbon nanotubes (GO-NCNTs) dispersion. The morphological and [...] Read more.

In this work, a three dimensional (3D) graphene-nitrogen doped carbon nanotubes (G-NCNTs) network was successfully fabricated on the surface of a glassy carbon (GC) electrode using the pulse potential method (PPM) in a graphene oxide-nitrogen doped carbon nanotubes (GO-NCNTs) dispersion. The morphological and characteristics of GO-NCNTs and G-NCNTs nanocomposites were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy, Raman spectroscopy, and electrochemical experiments. The 3DG-NCNTs network was applied as a new voltammetric material for the fabrication of an electrochemical platform for determination of urapidil. Systematic electrochemical tests demonstrate that the 3DG-NCNTs network modified GC electrode can effectively increase the response to the oxidation of urapidil. Under the optimum conditions, the electrochemical response was linear with urapidil concentrations in the range of 1.0 × 10⁻⁸~2.0 × 10⁻⁶ mol·L⁻¹, while a low detection limit of 5.0 × 10⁻⁹ mol·L⁻¹ was obtained for urapidil. Moreover, the proposed sensing platform exhibited good results for sensitivity, reproducibility, selectivity, and stability, which makes it very suitable for use as an ideal inexpensive and rapid analytical method applicable for complex drug matrices. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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13 pages, 2923 KiB

Open AccessArticle

The Influence of the Interlayer Distance on the Performance of Thermally Reduced Graphene Oxide Supercapacitors

by Jun-Hong Lin

Materials 2018, 11(2), 263; https://doi.org/10.3390/ma11020263 - 08 Feb 2018

Cited by 10 | Viewed by 4120

Abstract

In this paper, cationic surfactant cetyltrimethylammonium bromide (CTAB) was employed to prevent the restack of the thermally reduce graphene oxide (TRG) sheets. A facile approach was demonstrated to effectively enlarge the interlayer distance of the TRG sheets through the ionic interaction between the [...] Read more.

In this paper, cationic surfactant cetyltrimethylammonium bromide (CTAB) was employed to prevent the restack of the thermally reduce graphene oxide (TRG) sheets. A facile approach was demonstrated to effectively enlarge the interlayer distance of the TRG sheets through the ionic interaction between the intercalated CTAB and ionic liquids (ILs). The morphology of the composites and the interaction between the intercalated ionic species were systematically characterized by SEM, SAXS, XRD, TGA, and FTIR. In addition, the performance of the EDLC cells based on these TRG composites was evaluated. It was found that due to the increased interlayer distance (0.41 nm to 2.51 nm) that enlarges the accessible surface area for the IL electrolyte, the energy density of the cell can be significantly improved (23.1 Wh/kg to 62.5 Wh/kg). Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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12 pages, 8617 KiB

Open AccessArticle

Influence of PEG Stoichiometry on Structure-Tuned Formation of Self-Assembled Submicron Nickel Particles

by Bingxue Pu, Liping Wang, Heng Guo, Jian Yang, Haiyuan Chen, Yajun Zhou, Jin Yang, Bin Zhao and Xiaobin Niu

Materials 2018, 11(2), 222; https://doi.org/10.3390/ma11020222 - 31 Jan 2018

Cited by 1 | Viewed by 3362

Abstract

Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and [...] Read more.

Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and hollow structures were prepared through different processing conditions with two parameters such as temperature and time. Based on scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometry (VSM), the submicron nickel particles show good saturation magnetization and excellent thermal stabilities with a possible growth mechanism for the variety of the structure-tuned formation. Importantly, the microwave absorption properties of the submicron nickel particles were studied. The lowest reflection loss of Ni-P₉/T₂₀₀/H₁₅ with a thin layer thickness of 1.7 mm can reach −42.6 dB at 17.3 GHz. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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16 pages, 3436 KiB

Open AccessArticle

Effect of Fluoride on the Morphology and Electrochemical Property of Co₃O₄ Nanostructures for Hydrazine Detection

by Tuantuan Zhou, Wanlin Gao, Qiang Wang and Ahmad Umar

Materials 2018, 11(2), 207; https://doi.org/10.3390/ma11020207 - 29 Jan 2018

Cited by 22 | Viewed by 4579

Abstract

In this paper, we systematically investigated the influence of fluoride on the morphology and electrochemical property of Co₃O₄ nanostructures for hydrazine detection. The results showed that with the introduction of NH₄F during the synthesis process of Co₃ [...] Read more.

In this paper, we systematically investigated the influence of fluoride on the morphology and electrochemical property of Co₃O₄ nanostructures for hydrazine detection. The results showed that with the introduction of NH₄F during the synthesis process of Co₃O₄, both Co(CO₃)_0.5(OH)·0.11H₂O and Co(OH)F precursors would be generated. To understand the influence of F on the morphology and electrochemical property of Co₃O₄, three Co₃O₄ nanostructures that were respectively obtained from bare Co(CO₃)_0.5(OH)·0.11H₂O, Co(OH)F and Co(CO₃)_0.5(OH)·0.11H₂O mixtures and bare Co(OH)F were successfully synthesized. The electrochemical tests revealed the sensing performance of prepared Co₃O₄ nanostructures decreased with the increase in the fluoride contents of precursors. The more that dosages of NH₄F were used, the higher crystallinity and smaller specific surface area of Co₃O₄ was gained. Among these three Co₃O₄ nanostructures, the Co₃O₄ that was obtained from bare Co(CO₃)_0.5(OH)·0.11H₂O-based hydrazine sensor displayed the best performances, which exhibited a great sensitivity (32.42 μA·mM⁻¹), a low detection limit (9.7 μΜ), and a wide linear range (0.010–2.380 mM), together with good selectivity, great reproducibility and longtime stability. To the best of our knowledge, it was revealed for the first time that the sensing performance of prepared Co₃O₄ nanostructures decreased with the increase in fluoride contents of precursors. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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46 pages, 12040 KiB

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Recent Advances and Perspectives of Carbon-Based Nanostructures as Anode Materials for Li-ion Batteries

by L. Selva Roselin, Ruey-Shin Juang, Chien-Te Hsieh, Suresh Sagadevan, Ahmad Umar, Rosilda Selvin and Hosameldin H. Hegazy

Materials 2019, 12(8), 1229; https://doi.org/10.3390/ma12081229 - 15 Apr 2019

Cited by 104 | Viewed by 8961

Abstract

Rechargeable batteries are attractive power storage equipment for a broad diversity of applications. Lithium-ion (Li-ion) batteries are widely used the superior rechargeable battery in portable electronics. The increasing needs in portable electronic devices require improved Li-ion batteries with excellent results over many discharge-recharge [...] Read more.

Rechargeable batteries are attractive power storage equipment for a broad diversity of applications. Lithium-ion (Li-ion) batteries are widely used the superior rechargeable battery in portable electronics. The increasing needs in portable electronic devices require improved Li-ion batteries with excellent results over many discharge-recharge cycles. One important approach to ensure the electrodes’ integrity is by increasing the storage capacity of cathode and anode materials. This could be achieved using nanoscale-sized electrode materials. In the article, we review the recent advances and perspectives of carbon nanomaterials as anode material for Lithium-ion battery applications. The first section of the review presents the general introduction, industrial use, and working principles of Li-ion batteries. It also demonstrates the advantages and disadvantages of nanomaterials and challenges to utilize nanomaterials for Li-ion battery applications. The second section of the review describes the utilization of various carbon-based nanomaterials as anode materials for Li-ion battery applications. The last section presents the conclusion and future directions. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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27 pages, 2905 KiB

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Two-Dimensional Layered Double Hydroxides for Reactions of Methanation and Methane Reforming in C1 Chemistry

by Panpan Li, Feng Yu, Naveed Altaf, Mingyuan Zhu, Jiangbing Li, Bin Dai and Qiang Wang

Materials 2018, 11(2), 221; https://doi.org/10.3390/ma11020221 - 31 Jan 2018

Cited by 37 | Viewed by 7559

Abstract

CH₄ as the paramount ingredient of natural gas plays an eminent role in C1 chemistry. CH₄ catalytically converted to syngas is a significant route to transmute methane into high value-added chemicals. Moreover, the CO/CO₂ methanation reaction is one of the [...] Read more.

CH₄ as the paramount ingredient of natural gas plays an eminent role in C1 chemistry. CH₄ catalytically converted to syngas is a significant route to transmute methane into high value-added chemicals. Moreover, the CO/CO₂ methanation reaction is one of the potent technologies for CO₂ valorization and the coal-derived natural gas production process. Due to the high thermal stability and high extent of dispersion of metallic particles, two-dimensional mixed metal oxides through calcined layered double hydroxides (LDHs) precursors are considered as the suitable supports or catalysts for both the reaction of methanation and methane reforming. The LDHs displayed compositional flexibility, small crystal sizes, high surface area and excellent basic properties. In this paper, we review previous works of LDHs applied in the reaction of both methanation and methane reforming, focus on the LDH-derived catalysts, which exhibit better catalytic performance and thermal stability than conventional catalysts prepared by impregnation method and also discuss the anti-coke ability and anti-sintering ability of LDH-derived catalysts. We believe that LDH-derived catalysts are promising materials in the heterogeneous catalytic field and provide new insight for the design of advance LDH-derived catalysts worthy of future research. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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