Materials

669 KiB

Open AccessArticle

Hierarchical Fibers with a Negative Poisson’s Ratio for Tougher Composites

by Yongtao Sun and Nicola Pugno

Materials 2013, 6(2), 699-712; https://doi.org/10.3390/ma6020699 - 22 Feb 2013

Cited by 76 | Viewed by 11705

In this paper, a new kind of hierarchical tube with a negative Poisson’s ratio (NPR) is proposed. The first level tube is constructed by rolling up an auxetic hexagonal honeycomb. Then, the second level tube is produced by substituting the arm of the [...] Read more.

In this paper, a new kind of hierarchical tube with a negative Poisson’s ratio (NPR) is proposed. The first level tube is constructed by rolling up an auxetic hexagonal honeycomb. Then, the second level tube is produced by substituting the arm of the auxetic sheet with the first level tube and rolling it up. The Nth ( ) level tube can be built recursively. Based on the Euler beam theory, the equivalent elastic parameters of the NPR hierarchical tubes under small deformations are derived. Under longitudinal axial tension, instead of shrinking, all levels of the NPR hierarchical tubes expand in the transverse direction. Using these kinds of auxetic tubes as reinforced fibers in composite materials would result in a higher resistance to fiber pullout. Thus, this paper provides a new strategy for the design of fiber reinforced hierarchical bio-inspired composites with a superior pull-out mechanism, strength and toughness. An application with super carbon nanotubes concludes the paper. Full article

(This article belongs to the Special Issue Advances in Bio-inspired Materials)

► Show Figures

Graphical abstract

513 KiB

Open AccessArticle

Utilization of an Ionic Liquid/Urea Mixture as a Physical Coupling Agent for Agarose/Talc Composite Films

by Ahmad Adlie Shamsuri and Rusli Daik

Materials 2013, 6(2), 682-698; https://doi.org/10.3390/ma6020682 - 22 Feb 2013

Cited by 30 | Viewed by 6683

Abstract

An ionic liquid, 1-n-butyl-3-methylimidazolium chloride (BmimCl) was blended with urea at 1:1 mole ratio to create a BmimCl/Urea mixture. The agarose/talc composite films containing the BmimCl/Urea mixture were then acquired through a gelation method. The weight ratio of agarose and talc was fixed [...] Read more.

An ionic liquid, 1-n-butyl-3-methylimidazolium chloride (BmimCl) was blended with urea at 1:1 mole ratio to create a BmimCl/Urea mixture. The agarose/talc composite films containing the BmimCl/Urea mixture were then acquired through a gelation method. The weight ratio of agarose and talc was fixed at 4:1, while the content of BmimCl/Urea was varied from 0 to 10 wt % relative to the overall weight of the composite films. The tensile stress and modulus results showed the optimum BmimCl/Urea content in the composite film lies at 8 wt %. The talc particles are embedded in the agarose matrix and there are no pullouts for the composite films containing BmimCl/Urea as demonstrated by SEM micrographs. The addition of BmimCl/Urea increased the glass transition temperature of the composite films, however, the thermal decomposition temperature decreased drastically. FTIR and FT-Raman spectra indicated the existence of interaction between agarose and talc, which improves their interfacial adhesion. As a conclusion, a BmimCl/Urea mixture can be utilized as a coupling agent for agarose/talc composite films. Full article

► Show Figures

Figure 1

Figure 1
Effects of 1-n-butyl-3-methylimidazolium chloride (BmimCl) content on (a) stress-strain behaviour; (b) tensile stress; (c) modulus; (d) tensile extension and (e) tensile strain of the agarose/talc composite films. Full article ">Figure 2
Scanning electron microscope (SEM) micrographs of the fractured surface of the agarose/talc composite films with (a) 0 wt %; (b) 2 wt %; (c) 4 wt %; (d) 6 wt %; (e) 8 wt % and (f) 10 wt % of BmimCl/Urea at magnification of 1000×. Full article ">Figure 3
Differential scanning calorimetry (DSC) thermograms of the agarose/talc composite films. Full article ">Figure 4
Thermogravimetric analysis (TGA) thermograms of the agarose/talc composite films. Full article ">Figure 5
Derivative thermograms (DTG) of the agarose/talc composite films. Full article ">Figure 6
Fourier transform infrared spectroscopy (FTIR) spectra of the agarose/talc composite films with various contents of BmimCl/Urea. Full article ">Figure 7
Chemical structures of the (a) agarose; (b) talc and (c) BmimCl/Urea. Full article ">Figure 8
Proposed interactional model for the talc–BmimCl/Urea–agarose in the composite films. Full article ">Figure 9
FT-Raman spectra of the agarose/talc composite films containing different amount of BmimCl/Urea. Full article ">

1528 KiB

Open AccessArticle

Supported Membranes Meet Flat Fluidics: Monitoring Dynamic Cell Adhesion on Pump-Free Microfluidics Chips Functionalized with Supported Membranes Displaying Mannose Domains

by Jochen Oelke, Thomas Kaindl, Andreea Pasc, Zeno Guttenberg, Achim Wixforth and Motomu Tanaka

Materials 2013, 6(2), 669-681; https://doi.org/10.3390/ma6020669 - 22 Feb 2013

Cited by 2 | Viewed by 6506

Abstract

In this paper we demonstrate the combination of supported membranes and so-called flat microfluidics, which enables one to manipulate liquids on flat chip surfaces via “inverse piezoelectric effect”. Here, an alternating external electric field applied to the inter-digital transducers excites a surface acoustic [...] Read more.

In this paper we demonstrate the combination of supported membranes and so-called flat microfluidics, which enables one to manipulate liquids on flat chip surfaces via “inverse piezoelectric effect”. Here, an alternating external electric field applied to the inter-digital transducers excites a surface acoustic wave on a piezoelectric substrate. Employing lithographic patterning of self-assembled monolayers of alkoxysilanes, we successfully confine a free-standing, hemi-cylindrical channel with the volume of merely 7 µL . The experimentally determined maximum flow velocity scales linearly with the acoustic power, suggesting that our current setup can drive liquids at the speed of up to 7 cm/s (corresponding to a shear rate of 280 s⁻¹) without applying high pressures using a fluidic pump. After the establishment of the functionalization of fluidic chip surfaces with supported membranes, we deposited asymmetric supported membranes displaying well-defined mannose domains and monitored the dynamic adhesion of E. Coli HB101 expressing mannose-binding receptors. Despite of the further technical optimization required for the quantitative analysis, the obtained results demonstrate that the combination of supported membranes and flat fluidics opens a large potential to investigate dynamic adhesion of cells on biofunctional membrane surfaces with the minimum amount of samples, without any fluidic pump. Full article

(This article belongs to the Special Issue Supported Lipid Membranes)

► Show Figures

Figure 1

1160 KiB

Open AccessReview

Advanced Strategies for Articular Cartilage Defect Repair

by Amos Matsiko, Tanya J. Levingstone and Fergal J. O'Brien

Materials 2013, 6(2), 637-668; https://doi.org/10.3390/ma6020637 - 22 Feb 2013

Cited by 99 | Viewed by 11370

Abstract

Articular cartilage is a unique tissue owing to its ability to withstand repetitive compressive stress throughout an individual’s lifetime. However, its major limitation is the inability to heal even the most minor injuries. There still remains an inherent lack of strategies that stimulate [...] Read more.

Articular cartilage is a unique tissue owing to its ability to withstand repetitive compressive stress throughout an individual’s lifetime. However, its major limitation is the inability to heal even the most minor injuries. There still remains an inherent lack of strategies that stimulate hyaline-like articular cartilage growth with appropriate functional properties. Recent scientific advances in tissue engineering have made significant steps towards development of constructs for articular cartilage repair. In particular, research has shown the potential of biomaterial physico-chemical properties significantly influencing the proliferation, differentiation and matrix deposition by progenitor cells. Accordingly, this highlights the potential of using such properties to direct the lineage towards which such cells follow. Moreover, the use of soluble growth factors to enhance the bioactivity and regenerative capacity of biomaterials has recently been adopted by researchers in the field of tissue engineering. In addition, gene therapy is a growing area that has found noteworthy use in tissue engineering partly due to the potential to overcome some drawbacks associated with current growth factor delivery systems. In this context, such advanced strategies in biomaterial science, cell-based and growth factor-based therapies that have been employed in the restoration and repair of damaged articular cartilage will be the focus of this review article. Full article

(This article belongs to the Special Issue Advances in Bio-inspired Materials)

► Show Figures

Figure 1

Figure 1
The structural organization of articular cartilage from the superficial zone to the deep zone and the calcified cartilage. The illustration on the left shows collagen fibers and chondrocytes of articular cartilage demonstrating the difference in their orientation and shape within the different zones. The histological image (haemotoxylin and eosin (H&E) staining) on the right is taken from the femoral condyle of a rabbit knee joint and demonstrates the distribution of chondrocytes within the different zones (scale bar represents 100 µm). Full article ">Figure 2
An illustration of the tissue engineering triad comprised of cells, scaffolds and biological signal molecules. (Scaffold scanning electron microscope (SEM) image reprinted with permission from [<a href="#B38-materials-06-00637" class="html-bibr">38</a>]. Copyright 2012 Elsevier). Full article ">Figure 3
Scanning electron microscope images of collagen-glycosaminoglycan scaffolds with two distinct mean pore sizes; 94 µm (A); 130 µm (B). The scale bar represents 100 µm. Full article ">Figure 4
An illustration of three scaffold characteristics that have a fundamental role in the response of cells. One important property is the microstructure of scaffolds that may influence cell infiltration (central scaffold SEM image reprinted with permission from [<a href="#B38-materials-06-00637" class="html-bibr">38</a>], copyright (2012) Elsevier). Magnified SEM image shows the microstructure of a collagen-based scaffold. The chemical composition is another important property that can alter cell-scaffold adhesion. The chemical structure represents a hyaluronic acid disaccharide unit, n~5000 (Reprinted with permission from [<a href="#B138-materials-06-00637" class="html-bibr">138</a>], copyright 1972 Nature Publishing Group). The mechanical property of the scaffold also plays an important role in cell response by influencing cell proliferation, differentiation and migration (the graph shows a typical stress-strain curve of a ductile material). Full article ">Figure 5
Scanning electron microscope image of a collagen scaffold incorporated with alginate micro-particles. The micro-particles can be seen adhered to the struts of the scaffolds. The scale bar represents a 5 µm length. Full article ">

1867 KiB

Open AccessArticle

Structural and Electrochemical Investigation during the First Charging Cycles of Silicon Microwire Array Anodes for High Capacity Lithium Ion Batteries

by Enrique Quiroga-González, Jürgen Carstensen and Helmut Föll

Materials 2013, 6(2), 626-636; https://doi.org/10.3390/ma6020626 - 22 Feb 2013

Cited by 26 | Viewed by 7157

Abstract

Silicon microwire arrays embedded in Cu present exceptional performance as anode material in Li ion batteries. The processes occurring during the first charging cycles of batteries with this anode are essential for good performance. This paper sheds light on the electrochemical and structural [...] Read more.

Silicon microwire arrays embedded in Cu present exceptional performance as anode material in Li ion batteries. The processes occurring during the first charging cycles of batteries with this anode are essential for good performance. This paper sheds light on the electrochemical and structural properties of the anodes during the first charging cycles. Scanning Electron Microscopy, X-ray diffractommetry, and fast Fourier transformation impedance spectroscopy are used for the characterization. It was found that crystalline phases with high Li content are obtained after the first lithiation cycle, while for the second lithiation just crystalline phases with less Li are observable, indicating that the lithiated wires become amorphous upon cycling. The formation of a solid electrolyte interface of around 250 nm during the first lithiation cycle is evidenced, and is considered a necessary component for the good cycling performance of the wires. Analog to voltammetric techniques, impedance spectroscopy is confirmed as a powerful tool to identify the formation of the different Si-Li phases. Full article

(This article belongs to the Special Issue Advanced Materials for Lithium Ion Batteries)

► Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
Cycling performance of the Si wire anode with C/10 current for four cycles. The battery was charged to 75% of its maximal capacity to reach long term stability. Full article ">Figure 2
(a) Silicon microwire array of the anodes. The wires are 70 µm long and have 1 µm of diameter. The wider parts are stabilizing planes; (b) Top view of a finished anode. The bottom 10 µm of the wires are embedded in Cu (visible at the right). Full article ">Figure 3
Scanning electron microscope (SEM) micrograph of the anodes after the second lithiation cycle. The wires were broken during the preparation of the sample for SEM (a cut in cross section), as confirmed with other micrographs, where the wires behind the cut fronts were complete (see <a href="#app1-materials-06-00626" class="html-app">Figure S1</a>). The length of the wires is nearly the same as in the not lithiated state. Full article ">Figure 4
Micrographs of different regions of the same lithiated microwires as shown in <a href="#materials-06-00626-f003" class="html-fig">Figure 3</a>. (a) Tips of the wires; (b) Middle section; (c) Section embedded in Cu; (d) Surface of the wires in the middle section; here the solid electrolyte interface (SEI) is visible. Full article ">Figure 5
X-ray diffractograms of lithiated Si wire anodes after one and two charging cycles. The vertical lines are a guide for the eye to identify the different peaks. The peaks marked with an asterisk could not be assigned to a single Si-Li phase; in those ranges many low intensity reflections of different Li-Si phases are possible. Full article ">Figure 6
Plots of the different time constants obtained by fast Fourier transformation impedance spectroscopy (FFT-IS) during the lithiation/delithiation process of the wires. The current density J during cycling is shown as reference. The plots are divided into six sections. Sections 1, 3 and 5 are obtained under constant current, and Sections 2, 4 and 6 under constant voltage. Full article ">Figure 7
Plot of the time constant τ3 with time in the range of constant current. The derivative of the voltage in those ranges is also shown. Full article ">

961 KiB

Open AccessArticle

Room Temperature Ferromagnetic, Anisotropic, Germanium Rich FeGe(001) Alloys

by George A. Lungu, Nicoleta G. Apostol, Laura E. Stoflea, Ruxandra M. Costescu, Dana G. Popescu and Cristian M. Teodorescu

Materials 2013, 6(2), 612-625; https://doi.org/10.3390/ma6020612 - 21 Feb 2013

Cited by 14 | Viewed by 5935

Abstract

Ferromagnetic Fe_xGe_1−x with x = 2%–9% are obtained by Fe deposition onto Ge(001) at high temperatures (500 °C). Low energy electron diffraction (LEED) investigation evidenced the preservation of the (1 × 1) surface structure of Ge(001) with Fe deposition. [...] Read more.

Ferromagnetic Fe_xGe_1−x with x = 2%–9% are obtained by Fe deposition onto Ge(001) at high temperatures (500 °C). Low energy electron diffraction (LEED) investigation evidenced the preservation of the (1 × 1) surface structure of Ge(001) with Fe deposition. X-ray photoelectron spectroscopy (XPS) at Ge 3d and Fe 2p core levels evidenced strong Fe diffusion into the Ge substrate and formation of Ge-rich compounds, from FeGe₃ to approximately FeGe₂, depending on the amount of Fe deposited. Room temperature magneto-optical Kerr effect (MOKE) evidenced ferromagnetic ordering at room temperature, with about 0.1 Bohr magnetons per Fe atom, and also a clear uniaxial magnetic anisotropy with the in-plane easy magnetization axis. This compound is a good candidate for promising applications in the field of semiconductor spintronics. Full article

(This article belongs to the Special Issue Compound Semiconductor Materials)

► Show Figures

Figure 1

Figure 1
Low energy electron diffraction (LEED) patterns of clean Ge(001) (2 × 1) − (1 × 2) (a) and of 12 ML Fe/Ge(001) deposited at 500 °C (b). In order to enhance the clarity, negatives of the original photographs are used. The energy used is represented on each pattern. Each pattern has one spot highlighted by a yellow circle, to estimate its approximate broadening; (c) LEED spot profile analysis of both images along the designated pink curves in (a) and (b). Black lines are intensity profiles, red curves are fits using Voigt profiles. Full article ">Figure 2
Ge 3d electron distribution curves (EDCs) for clean Ge(001) and for Fe/Ge(001) deposited at 500 °C. The experimental data (red markers) are simulated with a fit with two spin-orbit split Voigt doublets. The separate components are the blue and the green curve; the total fitting function is the black curve. Full article ">Figure 3
Fe 2p EDCs for all Fe depositions on Ge(001). Same comments as for <a href="#materials-06-00612-f002" class="html-fig">Figure 2</a> are applicable. This time the spin-orbit splitting is quite visible between the 2p3/2 and 2p1/2 components. Full article ">Figure 4
Magneto-optical (MOKE) hysteresis loop for a sample consisting of 12 ML Fe deposited in Ge(001) at 500 °C, with the linear polarization vector of the incident light in the plane defined by the [001] and [100] direction (blue curve), and in the plane defined by the [001] and [110] direction (red curve). (a) Maximum applied field 0.1 T; (b) Maximum applied field 0.2 T. Full article ">Figure 5
Atomic force microscopy images obtained at room temperature and in air on 12 ML Fe deposited on Ge(001) at 500 °C, amplitude signal. Full article ">

21 KiB

Open AccessEditorial

Materials Best Paper Award 2013

by Maryam Tabrizian and Ophelia Han

Materials 2013, 6(2), 609-611; https://doi.org/10.3390/ma6020609 - 21 Feb 2013

Viewed by 5882

Abstract

Materials is instituting an annual award to recognize the outstanding papers in the area of materials science and engineering published in Materials. We are pleased to announce the first “Materials Best Paper Award” for 2013. Nominations were selected by the Section [...] Read more.

Materials is instituting an annual award to recognize the outstanding papers in the area of materials science and engineering published in Materials. We are pleased to announce the first “Materials Best Paper Award” for 2013. Nominations were selected by the Section Editor-in-Chiefs and Editorial Board members of Materials from all papers published in 2009. [...] Full article

► Show Figures

Graphical abstract

779 KiB

Open AccessReview

Solubilization of Hydrophobic Dyes in Surfactant Solutions

by Ali Reza Tehrani-Bagha and Krister Holmberg

Materials 2013, 6(2), 580-608; https://doi.org/10.3390/ma6020580 - 21 Feb 2013

Cited by 239 | Viewed by 20263

Abstract

In this paper, the use of surfactants for solubilization of hydrophobic organic dyes (mainly solvent and disperse dyes) has been reviewed. The effect of parameters such as the chemical structures of the surfactant and the dye, addition of salt and of polyelectrolytes, pH, [...] Read more.

In this paper, the use of surfactants for solubilization of hydrophobic organic dyes (mainly solvent and disperse dyes) has been reviewed. The effect of parameters such as the chemical structures of the surfactant and the dye, addition of salt and of polyelectrolytes, pH, and temperature on dye solubilization has been discussed. Surfactant self-assemble into micelles in aqueous solution and below the concentration where this occurs—the critical micelle concentration (CMC)—there is no solubilization. Above the CMC, the amount of solubilized dye increases linearly with the increase in surfactant concentration. It is demonstrated that different surfactants work best for different dyes. In general, nonionic surfactants have higher solubilization power than anionic and cationic surfactants. It is likely that the reason for the good performance of nonionic surfactants is that they allow dyes to be accommodated not only in the inner, hydrocarbon part of the micelle but also in the headgroup shell. It is demonstrated that the location of a dye in a surfactant micelle can be assessed from the absorption spectrum of the dye-containing micellar solution. Full article

(This article belongs to the Special Issue Advances in Colorants)

► Show Figures

Figure 1

329 KiB

Open AccessArticle

Pore Narrowing of Mesoporous Silica Materials

by Frederik Goethals, Elisabeth Levrau, Els De Canck, Mikhail R. Baklanov, Christophe Detavernier, Isabel Van Driessche and Pascal Van Der Voort

Materials 2013, 6(2), 570-579; https://doi.org/10.3390/ma6020570 - 20 Feb 2013

Cited by 3 | Viewed by 7059

Abstract

To use mesoporous silicas as low-k materials, the pore entrances must be really small to avoid diffusion of metals that can increase the dielectric constant of the low-k dielectric. In this paper we present a new method to narrow the pores of mesoporous [...] Read more.

To use mesoporous silicas as low-k materials, the pore entrances must be really small to avoid diffusion of metals that can increase the dielectric constant of the low-k dielectric. In this paper we present a new method to narrow the pores of mesoporous materials through grafting of a cyclic-bridged organosilane precursor. As mesoporous material, the well-studied MCM-41 powder was selected to allow an easy characterization of the grafting reactions. Firstly, the successful grafting of the cyclic-bridged organosilane precursor on MCM-41 is presented. Secondly, it is demonstrated that pore narrowing can be obtained without losing porosity by removing the porogen template after grafting. The remaining silanols in the pores can then be end-capped with hexamethyl disilazane (HMDS) to make the material completely hydrophobic. Finally, we applied the pore narrowing method on organosilica films to prove that this method is also successful on existing low-k materials. Full article

(This article belongs to the Special Issue Advances in Mesoporous Materials)

► Show Figures

Graphical abstract

25 KiB

Open AccessNew Book Received

Atlas of Material Damage. By George Wypych, ChemTec Publishing, Year 2012; 310 Pages. Price $325.00, ISBN 978-1-895198-48-5

by Shu-Kun Lin

Materials 2013, 6(2), 565-569; https://doi.org/10.3390/ma6020565 - 19 Feb 2013

Viewed by 4101

Abstract

Atlas of Material Damage has 464 microscopic pictures, schematic diagrams, and a few graphs, which show how materials fail, how they are produced to not fail, and how they are designed to perform particular functions to make outstanding products. Findings presented by each [...] Read more.

Atlas of Material Damage has 464 microscopic pictures, schematic diagrams, and a few graphs, which show how materials fail, how they are produced to not fail, and how they are designed to perform particular functions to make outstanding products. Findings presented by each illustration are fully explained in the text and labeled. Full article

386 KiB

Open AccessArticle

Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor

by Dengjian Li, Weiguo Li, Dingyu Li, Yushan Shi and Daining Fang

Materials 2013, 6(2), 551-564; https://doi.org/10.3390/ma6020551 - 18 Feb 2013

Cited by 7 | Viewed by 6406

Abstract

The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model [...] Read more.

The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model for ultra-high temperature ceramics considering the effects of the thermal environment and external constraint was established based on the existing theory. The present work mainly focused on the adjustment of the stress reduction factor according to different thermal shock situations. The influences of external constraint on both critical rupture temperature difference and the second thermal shock resistance parameter in either case of rapid heating or cooling conditions had been studied based on this model. The results show the necessity of adjustment of the stress reduction factor in different thermal shock situations and the limitations of the applicable range of the second thermal shock resistance parameter. Furthermore, the model was validated by the finite element method. Full article

(This article belongs to the Special Issue Ultra-high Temperature Ceramics)

► Show Figures

Figure 1

1046 KiB

Open AccessCommunication

Absorption and Tensility of Bioactive Sutures Prepared for Cell Transplantation

by Dénes B. Horváthy, Gabriella Vácz, Tamás Szabó, Károly Renner, Kinga Vajda, Balázs Sándor and Zsombor Lacza

Materials 2013, 6(2), 544-550; https://doi.org/10.3390/ma6020544 - 15 Feb 2013

Cited by 3 | Viewed by 4972

Abstract

Biodegradable scaffolds are widely used to transplant stem cells into various tissues. Recent studies showed that living stem cells can be attached to the surface of absorbable sutures in vitro. Soaking the absorbable material polyglactin in a cell culture medium and thereby [...] Read more.

Biodegradable scaffolds are widely used to transplant stem cells into various tissues. Recent studies showed that living stem cells can be attached to the surface of absorbable sutures in vitro. Soaking the absorbable material polyglactin in a cell culture medium and thereby creating a stem cell biofilm on its surface may initiate the absorption process even before implantation; therefore, the physicochemical properties of the suture may be compromised in vivo. We found that pre-incubation of sutures in cell culture media in vitro results in tensile strength reduction and faster suture absorption in a rat model of muscle injury. Shorter incubation times of up to 48 h do not influence absorption or tensility; therefore, it is advisable to limit incubation times to two days for polyglactin-based cell delivery protocols. Full article

(This article belongs to the Section Biomaterials)

► Show Figures

Graphical abstract

446 KiB

Open AccessArticle

Electron Density Modification of Single Wall Carbon Nanotubes (SWCNT) by Liquid-Phase Molecular Adsorption of Hexaiodobenzene

by Mingxia Lu, Tomonori Ohba, Katsumi Kaneko, Kenji Hata, Motoo Yumura, Sumio Iijima, Hiroto Komatsu, Akira Sakuma and Hirofumi Kanoh

Materials 2013, 6(2), 535-543; https://doi.org/10.3390/ma6020535 - 15 Feb 2013

Cited by 12 | Viewed by 7758

Abstract

Electron density of single wall carbon nanotubes (SWCNT) is effectively modified by hexaiodobenzene (HIB) molecules using liquid-phase adsorption. UV-Vis-NIR absorption spectra of the HIB-adsorbed SWCNT, especially in the NIR region, showed a disappearance of S₁₁ transitions between the V1 valance band and [...] Read more.

Electron density of single wall carbon nanotubes (SWCNT) is effectively modified by hexaiodobenzene (HIB) molecules using liquid-phase adsorption. UV-Vis-NIR absorption spectra of the HIB-adsorbed SWCNT, especially in the NIR region, showed a disappearance of S₁₁ transitions between the V1 valance band and the C1 conduction band of van Hove singularities which can be attributed to the effective charge transfer between HIB and the SWCNT. The adsorption of HIB also caused significant peak-shifts (lower frequency shift around 170 cm⁻¹ and higher shift around 186 cm^‑1) and an intensity change (around 100–150 cm⁻¹ and 270–290 cm⁻¹) in the radial breathing mode of Raman spectra. The charge transfer from SWCNT to HIB was further confirmed by the change in the C1s peak of X-ray photoelectron spectrum, revealing the oxidation of carbon in SWCNT upon HIB adsorption. Full article

► Show Figures

Figure 1

212 KiB

Open AccessReview

A Review of Aspects of Oxidative Hair Dye Chemistry with Special Reference to N-Nitrosamine Formation

by David Lewis, John Mama and Jamie Hawkes

Materials 2013, 6(2), 517-534; https://doi.org/10.3390/ma6020517 - 13 Feb 2013

Cited by 29 | Viewed by 16371

Abstract

This review discusses a new aspect to the safety profile of oxidative hair dyes using data already in the public domain. These dyes contain secondary amines that are capable of forming potentially carcinogenic nitrosamine derivatives when exposed to atmospheric pollution. Numerous scientific articles [...] Read more.

This review discusses a new aspect to the safety profile of oxidative hair dyes using data already in the public domain. These dyes contain secondary amines that are capable of forming potentially carcinogenic nitrosamine derivatives when exposed to atmospheric pollution. Numerous scientific articles confirm the existence of secondary amines in hair dyes (and their intermediates), the possibility of nitrosation by atmospheric NO_x of secondary amines to give the N-nitrosamines, and the significant safety risks on N-nitrosamines. It is believed that such nitrosamine derivatives should be investigated more fully in the interests of consumer safety. Full article

(This article belongs to the Special Issue Advances in Colorants)

► Show Figures

Figure 1

534 KiB

Open AccessReview

Extraordinary Magnetoresistance in Semiconductor/Metal Hybrids: A Review

by Jian Sun and Jürgen Kosel

Materials 2013, 6(2), 500-516; https://doi.org/10.3390/ma6020500 - 13 Feb 2013

Cited by 25 | Viewed by 8843

Abstract

The Extraordinary Magnetoresistance (EMR) effect is a change in the resistance of a device upon the application of a magnetic field in hybrid structures, consisting of a semiconductor and a metal. The underlying principle of this phenomenon is a change of the current [...] Read more.

The Extraordinary Magnetoresistance (EMR) effect is a change in the resistance of a device upon the application of a magnetic field in hybrid structures, consisting of a semiconductor and a metal. The underlying principle of this phenomenon is a change of the current path in the hybrid structure upon application of a magnetic field, due to the Lorentz force. Specifically, the ratio of current, flowing through the highly conducting metal and the poorly conducting semiconductor, changes. The main factors for the device’s performance are: the device geometry, the conductivity of the metal and semiconductor, and the mobility of carriers in the semiconductor. Since the discovery of the EMR effect, much effort has been devoted to utilize its promising potential. In this review, a comprehensive overview of the research on the EMR effect and EMR devices is provided. Different geometries of EMR devices are compared with respect to MR ratio and output sensitivity, and the criteria of material selection for high-performance devices are discussed. Full article

► Show Figures

Figure 1

837 KiB

Open AccessReview

Quantum Dots as Multifunctional Materials for Tumor Imaging and Therapy

by Longfei Liu, Qingqing Miao and Gaolin Liang

Materials 2013, 6(2), 483-499; https://doi.org/10.3390/ma6020483 - 5 Feb 2013

Cited by 29 | Viewed by 8141

Abstract

The rapidly developing field of quantum dots (QDs) provides researchers with more options for imaging modalities and therapeutic strategies. In recent years, QDs were widely used as multifunctional materials for tumor imaging and therapy due to their characteristic properties such as semiconductive, zero-dimension [...] Read more.

The rapidly developing field of quantum dots (QDs) provides researchers with more options for imaging modalities and therapeutic strategies. In recent years, QDs were widely used as multifunctional materials for tumor imaging and therapy due to their characteristic properties such as semiconductive, zero-dimension and strong fluorescence. Nevertheless, there still exist the challenges of employing these properties of QDs for clinical diagnosis and therapy. Herein, we briefly review the development, properties and applications of QDs in tumor imaging and therapy. Future perspectives in these areas are also proposed as well. Full article

(This article belongs to the Special Issue Advances in Multifunctional Materials)

► Show Figures

Figure 1

2242 KiB

Open AccessReview

Advances in Fabrication Materials of Honeycomb Structure Films by the Breath-Figure Method

by Liping Heng, Bin Wang, Muchen Li, Yuqi Zhang and Lei Jiang

Materials 2013, 6(2), 460-482; https://doi.org/10.3390/ma6020460 - 4 Feb 2013

Cited by 76 | Viewed by 13336

Abstract

Creatures in nature possess almost perfect structures and properties, and exhibit harmonization and unification between structure and function. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special properties. Recently, honeycomb structure materials have attracted wide [...] Read more.

Creatures in nature possess almost perfect structures and properties, and exhibit harmonization and unification between structure and function. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special properties. Recently, honeycomb structure materials have attracted wide attention for both fundamental research and practical applications and have become an increasingly hot research topic. Though progress in the field of breath-figure formation has been reviewed, the advance in the fabrication materials of bio-inspired honeycomb structure films has not been discussed. Here we review the recent progress of honeycomb structure fabrication materials which were prepared by the breath-figure method. The application of breath figures for the generation of all kinds of honeycomb is discussed. Full article

(This article belongs to the Special Issue Advances in Bio-inspired Materials)

► Show Figures

Graphical abstract

565 KiB

Open AccessReview

Semiconductor Nanocrystals as Light Harvesters in Solar Cells

by Lioz Etgar

Materials 2013, 6(2), 445-459; https://doi.org/10.3390/ma6020445 - 4 Feb 2013

Cited by 70 | Viewed by 12123

Abstract

Photovoltaic cells use semiconductors to convert sunlight into electrical current and are regarded as a key technology for a sustainable energy supply. Quantum dot-based solar cells have shown great potential as next generation, high performance, low-cost photovoltaics due to the outstanding optoelectronic properties [...] Read more.

Photovoltaic cells use semiconductors to convert sunlight into electrical current and are regarded as a key technology for a sustainable energy supply. Quantum dot-based solar cells have shown great potential as next generation, high performance, low-cost photovoltaics due to the outstanding optoelectronic properties of quantum dots and their multiple exciton generation (MEG) capability. This review focuses on QDs as light harvesters in solar cells, including different structures of QD-based solar cells, such as QD heterojunction solar cells, QD-Schottky solar cells, QD-sensitized solar cells and the recent development in organic-inorganic perovskite heterojunction solar cells. Mechanisms, procedures, advantages, disadvantages and the latest results obtained in the field are described. To summarize, a future perspective is offered. Full article

(This article belongs to the Special Issue Photovoltaic Materials)

► Show Figures

Figure 1

677 KiB

Open AccessArticle

Crystallographic Orientation Influence on the Serrated Yielding Behavior of a Single-Crystal Superalloy

by Mikael Segersäll and Johan J. Moverare

Materials 2013, 6(2), 437-444; https://doi.org/10.3390/ma6020437 - 31 Jan 2013

Cited by 26 | Viewed by 6891

Abstract

Since Ni-based single-crystal superalloys are anisotropic materials, their behavior in different crystal orientations is of great interest. In this study, the yielding behavior in both tension and compression for , and oriented materials at 500 °C has been investigated. The direction showed a [...] Read more.

Since Ni-based single-crystal superalloys are anisotropic materials, their behavior in different crystal orientations is of great interest. In this study, the yielding behavior in both tension and compression for , and oriented materials at 500 °C has been investigated. The direction showed a serrated yielding behavior, a great tension/compression asymmetry in yield strength and visible deformation bands. However, the and directions showed a more homogeneous yielding, less tension/compression asymmetry in yield strength and no deformation bands. Microstructure investigations showed that the serrated yielding behavior of the direction can be attributed to the appearance of dynamic strain aging (DSA) and that only one slip system is active in this direction during plastic deformation. Full article

► Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
Tension and compression tests at 500 °C for <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>001</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>011</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>111</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math> directions. Full article ">Figure 2
Yield strengths for <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>001</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math>, <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>011</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>111</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math> directions at RT and 500 °C. RT yield strengths are taken from [<a href="#B5-materials-06-00437" class="html-bibr">5</a>]. Full article ">Figure 3
A sketch of the deformation band appearance on the specimen surfaces. Full article ">Figure 4
The <math display="inline"> <semantics> <mrow> <mrow><mo>〈</mo> <mrow> <mn>011</mn></mrow> <mo>〉</mo></mrow></mrow> </semantics> </math> specimen subjected to compressive stress; (a) a backscattered electron image of deformation bands at 1200 times magnification; (b) same deformation band as in (a) at 7000 times magnification; (c) EBSD map of such a deformation band, where each white segment corresponds to an orientation difference of 0.5°–1°. Full article ">

1486 KiB

Open AccessArticle

Material Analysis of Coated Siliconized Silicon Carbide (SiSiC) Honeycomb Structures for Thermochemical Hydrogen Production

by Martina Neises-von Puttkamer, Heike Simon, Martin Schmücker, Martin Roeb, Christian Sattler and Robert Pitz-Paal

Materials 2013, 6(2), 421-436; https://doi.org/10.3390/ma6020421 - 31 Jan 2013

Cited by 9 | Viewed by 7251

Abstract

In the present work, thermochemical water splitting with siliconized silicon carbide (SiSiC) honeycombs coated with a zinc ferrite redox material was investigated. The small scale coated monoliths were tested in a laboratory test-rig and characterized by X-ray diffractometry (XRD) and Scanning Electron Microscopy [...] Read more.

In the present work, thermochemical water splitting with siliconized silicon carbide (SiSiC) honeycombs coated with a zinc ferrite redox material was investigated. The small scale coated monoliths were tested in a laboratory test-rig and characterized by X-ray diffractometry (XRD) and Scanning Electron Microscopy (SEM) with corresponding micro analysis after testing in order to characterize the changes in morphology and composition. Comparison of several treated monoliths revealed the formation of various reaction products such as SiO₂, zircon (ZrSiO₄), iron silicide (FeSi) and hercynite (FeAl₂O₄) indicating the occurrence of various side reactions between the different phases of the coating as well as between the coating and the SiSiC substrate. The investigations showed that the ferrite is mainly reduced through reaction with silicon (Si), which is present in the SiSiC matrix, and silicon carbide (SiC). These results led to the formulation of a new redox mechanism for this system in which Zn-ferrite is reduced through Si forming silicon dioxide (SiO₂) and through SiC forming SiO₂ and carbon monoxide. A decline of hydrogen production within the first 20 cycles is suggested to be due to the growth of a silicon dioxide and zircon layer which acts as a diffusion barrier for the reacting specie. Full article

(This article belongs to the Section Advanced Materials Characterization)

► Show Figures

Figure 1

Figure 1
Siliconized silicon carbide (SiSiC) honeycomb structure used for testing. Full article ">Figure 2
(a) Scanning Electron Microscopy (SEM) images of polished cross section of Monolith 1 (untreated); (b) enlarged cutout of <a href="#materials-06-00421-f002" class="html-fig">Figure 2</a>a showing the coating of Monolith 1 and points where energy dispersive X-ray spectroscopy (EDS) were taken. Full article ">Figure 3
SEM image and EDS spectra of Monolith 2 after 1 cycle. Full article ">Figure 4
(a) SEM image of polished cross-section of Monolith 4 after 58 cycles (b) enlarged cutout of <a href="#materials-06-00421-f004" class="html-fig">Figure 4</a>a. Full article ">Figure 5
Specific hydrogen production over cycle number performed with Monolith 5. Full article ">Figure 6
X-ray diffractometry (XRD) patterns of coated SiSiC honeycombs, phases shown are SiC, Si3N4, Si and Fe3O4. Full article ">Figure 7
XRD patterns of coated SiSiC honeycombs, phases shown are SiO2, FeSi and ZrSiO4. Full article ">Figure 8
energy dispersive X-ray spectroscopy (EDS) mapping of Monolith 4. Full article ">

336 KiB

Open AccessArticle

Effect of Thermal Treatment of Veneer on Formaldehyde Emission of Poplar Plywood

by Koji Murata, Yashuhiro Watanabe and Takato Nakano

Materials 2013, 6(2), 410-420; https://doi.org/10.3390/ma6020410 - 30 Jan 2013

Cited by 28 | Viewed by 5850

Abstract

A large amount of poplar plywood is now being imported into Japan from China, and as a result, formaldehyde emitted from this plywood represents an undesirable chemical that must be controlled using a chemical catching agent. The aim of this study is to [...] Read more.

A large amount of poplar plywood is now being imported into Japan from China, and as a result, formaldehyde emitted from this plywood represents an undesirable chemical that must be controlled using a chemical catching agent. The aim of this study is to find an approach to reduce the formaldehyde emission of poplar plywood using thermal treatment without employing any chemicals. The experimental results obtained show that heating veneer sheets in the temperature range of 150 °C to 170 °C effectively reduced the formaldehyde emission of plywood, without diminishing the mechanical properties of the veneer. By applying Langmuir’s theory and Hailwood-Horrobin theory to the adsorption isotherm obtained in this study, the relationship between the formaldehyde emission of plywood and the adsorption properties of veneer as a material is discussed. When veneer sheets were heated in the temperature range of 150 °C to 170 °C, the amount of hydrated water (monomolecular layer) decreased slightly and that of dissolved water (polymolecular layer) did not change. It is hypothesized that the formaldehyde emission of plywood is related to the condition of the adsorption site of the wood. Full article

► Show Figures

Figure 1

952 KiB

Open AccessArticle

Mechanism of Catalytic Water Oxidation by the Ruthenium Blue Dimer Catalyst: Comparative Study in D₂O versus H₂O

by Dooshaye Moonshiram, Vatsal Purohit, Javier J. Concepcion, Thomas J. Meyer and Yulia Pushkar

Materials 2013, 6(2), 392-409; https://doi.org/10.3390/ma6020392 - 30 Jan 2013

Cited by 31 | Viewed by 8688

Abstract

Water oxidation is critically important for the development of energy solutions based on the concept of artificial photosynthesis. In order to gain deeper insight into the mechanism of water oxidation, the catalytic cycle for the first designed water oxidation catalyst, cis,cis [...] Read more.

Water oxidation is critically important for the development of energy solutions based on the concept of artificial photosynthesis. In order to gain deeper insight into the mechanism of water oxidation, the catalytic cycle for the first designed water oxidation catalyst, cis,cis-[(bpy)₂(H₂O)Ru^IIIORu^III(OH₂)(bpy)₂]⁴⁺ (bpy is 2,2-bipyridine) known as the blue dimer (BD), is monitored in D₂O by combined application of stopped flow UV-Vis, electron paramagnetic resonance (EPR) and resonance Raman spectroscopy on freeze quenched samples. The results of these studies show that the rate of formation of BD[4,5] by Ce(IV) oxidation of BD[3,4] (numbers in square bracket denote oxidation states of the ruthenium (Ru) centers) in 0.1 M HNO₃, as well as further oxidation of BD[4,5] are slower in D₂O by 2.1–2.5. Ce(IV) oxidation of BD[4,5] and reaction with H₂O result in formation of an intermediate, BD[3,4]′, which builds up in reaction mixtures on the minute time scale. Combined results under the conditions of these experiments at pH 1 indicate that oxidation of BD[3,4]′ is a rate limiting step in water oxidation with the BD catalyst. Full article

(This article belongs to the Special Issue Advanced Materials for Water-Splitting)

► Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
Mechanism of blue dimer (BD) water oxidation. Full article ">Figure 2
Kinetics of O2 evolution recorded with oxygen electrode immersed in (A) H2O and (B) D2O solution of the blue dimer[3,3] (0.1 mM in 0.1 M HNO3) after addition of 4 equiv of Ce(IV) to induce a single turnover as well as 20 equiv of Ce(IV). Full article ">Figure 3
(A) Stopped-flow UV-Vis measurement of BD[3,3] (0.1 mM) oxidation with 4 equiv and 20 equiv of Ce(IV) at pH 1 (HNO3) in H2O and in D2O; (B) Comparison of the absorbance traces at 480 nm in H2O and D2O for BD[3,3] with 4 equiv and 20 equiv Ce(IV) at pH 1. Full article ">Figure 4
Kinetic modeling of the reaction of 0.1 mM BD[3,3] with 4 equiv of Ce(IV) at pH 1 in (A) H2O and (B) D2O. Concentration profiles of BD[3,3], BD[3,4], BD[4,5], BD[3,4]′ and Ce(IV) are shown. Rate constants are given in <a href="#materials-06-00392-t002" class="html-table">Table 2</a>. UV-Vis absorbance kinetic results for these reactions are shown in <a href="#materials-06-00392-f003" class="html-fig">Figure 3</a>A,B. Full article ">Figure 5
(A) X-Band electron paramagnetic resonance (EPR) of 1 mM BD[3,4] mixed with 20 equiv Ce(IV) by hand in HNO3 and DNO3, pH = 1; (B) Resonance Raman of 1 mM BD[3,4] with 20 equiv Ce(IV) in HNO3 and DNO3, pH = 1 carried out in parallel with EPR measurements. Full article ">Figure 6
(A) X-Band EPR of 0.25 mM BD[3,4] with 20 equiv Ce(IV) in H2O freeze-quenched at different time intervals; (B) X-Band EPR of 0.25 mM BD[3,4] with 20 equiv Ce(IV) in D2O freeze-quenched at different time intervals; (C) UV-Vis absorbance curve at 481 nm showing times at which samples were freeze-quenched in H2O and D2O (The inflection points of both absorbance curves are shown in blue). Full article ">Figure 7
Resonance Raman measurements of 0.25 mM BD[3,4] with 20 equiv Ce(IV) in DNO3, pH = 1 freeze quenched at time intervals shown in <a href="#materials-06-00392-f006" class="html-fig">Figure 6</a>B. Full article ">Figure 8
EPR spectra of BD[4,5] freeze-quenched at higher concentration (0.5 mM, pH 1 in HNO3) in comparison with mixture of 60% BD[4,5] and 40% BD[3,4]′ prepared by manual mixing (1.2 mM, pH 1 in HNO3). BD[4,5] after subtracting 40% of BD[3,4]′ contribution is also shown (1.2 mM, pH 1 in HNO3). The shoulder on the main band is emphasized by arrows and the g-tensors are shown. G-tensor components at 2.038 and 1.996 shown by arrows are in agreement with those reported in <a href="#materials-06-00392-f005" class="html-fig">Figure 5</a>B in [<a href="#B9-materials-06-00392" class="html-bibr">9</a>]. Please note that the EPR intensity of BD[4,5] prepared by freeze quench(0.5 mM) was adjusted for comparison purposes. Full article ">Figure 9
(A) Resonance Raman measurements of 0.25 mM BD[3,4] with 20 equiv Ce(IV) in HNO3, pH 1 freeze quenched at some time intervals shown in <a href="#materials-06-00392-f006" class="html-fig">Figure 6</a>A; (B) Resonance Raman of 1 mM BD[3,4] and BD[3,4]′, pH 1 in HNO3. Full article ">

Journal Menu

Journal Browser

Materials, Volume 6, Issue 2 (February 2013) – 22 articles , Pages 392-712

Further Information

Guidelines

MDPI Initiatives

Follow MDPI