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

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Materials Best Paper Award 2013
Materials 2013, 6(2), 609-611; doi:10.3390/ma6020609
Received: 31 January 2013 / Accepted: 21 February 2013 / Published: 21 February 2013
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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 [...] 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
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Research

Jump to: Editorial, Review, Other

Open AccessArticle Mechanism of Catalytic Water Oxidation by the Ruthenium Blue Dimer Catalyst: Comparative Study in D2O versus H2O
Materials 2013, 6(2), 392-409; doi:10.3390/ma6020392
Received: 19 November 2012 / Revised: 5 January 2013 / Accepted: 23 January 2013 / Published: 30 January 2013
Cited by 4 | PDF Full-text (952 KB) | HTML Full-text | XML Full-text
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, [...] 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)RuIIIORuIII(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)
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Open AccessArticle Effect of Thermal Treatment of Veneer on Formaldehyde Emission of Poplar Plywood
Materials 2013, 6(2), 410-420; doi:10.3390/ma6020410
Received: 30 November 2012 / Revised: 23 January 2013 / Accepted: 24 January 2013 / Published: 30 January 2013
Cited by 3 | PDF Full-text (336 KB) | HTML Full-text | XML Full-text
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 [...] 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
Open AccessArticle Material Analysis of Coated Siliconized Silicon Carbide (SiSiC) Honeycomb Structures for Thermochemical Hydrogen Production
Materials 2013, 6(2), 421-436; doi:10.3390/ma6020421
Received: 26 December 2012 / Revised: 21 January 2013 / Accepted: 28 January 2013 / Published: 31 January 2013
Cited by 8 | PDF Full-text (1486 KB) | HTML Full-text | XML Full-text
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 [...] 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 Structure Analysis and Characterization)
Open AccessArticle Crystallographic Orientation Influence on the Serrated Yielding Behavior of a Single-Crystal Superalloy
Materials 2013, 6(2), 437-444; doi:10.3390/ma6020437
Received: 9 November 2012 / Revised: 10 January 2013 / Accepted: 29 January 2013 / Published: 31 January 2013
Cited by 4 | PDF Full-text (677 KB) | HTML Full-text | XML Full-text
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 [...] 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
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Open AccessArticle Electron Density Modification of Single Wall Carbon Nanotubes (SWCNT) by Liquid-Phase Molecular Adsorption of Hexaiodobenzene
Materials 2013, 6(2), 535-543; doi:10.3390/ma6020535
Received: 8 November 2012 / Revised: 3 February 2013 / Accepted: 5 February 2013 / Published: 15 February 2013
Cited by 3 | PDF Full-text (446 KB) | HTML Full-text | XML Full-text | Supplementary Files
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 [...] 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
Open AccessCommunication Absorption and Tensility of Bioactive Sutures Prepared for Cell Transplantation
Materials 2013, 6(2), 544-550; doi:10.3390/ma6020544
Received: 1 November 2012 / Revised: 22 January 2013 / Accepted: 24 January 2013 / Published: 15 February 2013
Cited by 1 | PDF Full-text (1046 KB) | HTML Full-text | XML Full-text
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 [...] 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)
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Open AccessArticle Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor
Materials 2013, 6(2), 551-564; doi:10.3390/ma6020551
Received: 27 November 2012 / Revised: 30 January 2013 / Accepted: 31 January 2013 / Published: 18 February 2013
Cited by 3 | PDF Full-text (386 KB) | HTML Full-text | XML Full-text
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 [...] 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)
Open AccessArticle Pore Narrowing of Mesoporous Silica Materials
Materials 2013, 6(2), 570-579; doi:10.3390/ma6020570
Received: 22 January 2013 / Revised: 7 February 2013 / Accepted: 16 February 2013 / Published: 20 February 2013
Cited by 1 | PDF Full-text (329 KB) | HTML Full-text | XML Full-text | Supplementary Files
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 [...] 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)
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Open AccessArticle Room Temperature Ferromagnetic, Anisotropic, Germanium Rich FeGe(001) Alloys
Materials 2013, 6(2), 612-625; doi:10.3390/ma6020612
Received: 4 December 2012 / Revised: 30 January 2013 / Accepted: 31 January 2013 / Published: 21 February 2013
Cited by 4 | PDF Full-text (961 KB) | HTML Full-text | XML Full-text
Abstract
Ferromagnetic FexGe1−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 [...] Read more.
Ferromagnetic FexGe1−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)
Open AccessArticle Structural and Electrochemical Investigation during the First Charging Cycles of Silicon Microwire Array Anodes for High Capacity Lithium Ion Batteries
Materials 2013, 6(2), 626-636; doi:10.3390/ma6020626
Received: 10 December 2012 / Revised: 4 February 2013 / Accepted: 19 February 2013 / Published: 22 February 2013
Cited by 11 | PDF Full-text (1867 KB) | HTML Full-text | XML Full-text | Supplementary Files
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 [...] 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)
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Open AccessArticle Supported Membranes Meet Flat Fluidics: Monitoring Dynamic Cell Adhesion on Pump-Free Microfluidics Chips Functionalized with Supported Membranes Displaying Mannose Domains
Materials 2013, 6(2), 669-681; doi:10.3390/ma6020669
Received: 18 October 2012 / Revised: 7 January 2013 / Accepted: 5 February 2013 / Published: 22 February 2013
Cited by 1 | PDF Full-text (1528 KB) | HTML Full-text | XML Full-text
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 [...] 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)
Open AccessArticle Utilization of an Ionic Liquid/Urea Mixture as a Physical Coupling Agent for Agarose/Talc Composite Films
Materials 2013, 6(2), 682-698; doi:10.3390/ma6020682
Received: 19 December 2012 / Revised: 26 January 2013 / Accepted: 20 February 2013 / Published: 22 February 2013
Cited by 5 | PDF Full-text (513 KB) | HTML Full-text | XML Full-text
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 [...] 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
Open AccessArticle Hierarchical Fibers with a Negative Poisson’s Ratio for Tougher Composites
Materials 2013, 6(2), 699-712; doi:10.3390/ma6020699
Received: 27 November 2012 / Revised: 9 January 2013 / Accepted: 15 January 2013 / Published: 22 February 2013
Cited by 13 | PDF Full-text (669 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] 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)
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Review

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Open AccessReview Semiconductor Nanocrystals as Light Harvesters in Solar Cells
Materials 2013, 6(2), 445-459; doi:10.3390/ma6020445
Received: 16 November 2012 / Revised: 14 January 2013 / Accepted: 16 January 2013 / Published: 4 February 2013
Cited by 27 | PDF Full-text (565 KB) | HTML Full-text | XML Full-text
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 [...] 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)
Open AccessReview Advances in Fabrication Materials of Honeycomb Structure Films by the Breath-Figure Method
Materials 2013, 6(2), 460-482; doi:10.3390/ma6020460
Received: 27 December 2012 / Revised: 16 January 2013 / Accepted: 28 January 2013 / Published: 4 February 2013
Cited by 24 | PDF Full-text (2242 KB) | HTML Full-text | XML Full-text
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 [...] 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)
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Open AccessReview Quantum Dots as Multifunctional Materials for Tumor Imaging and Therapy
Materials 2013, 6(2), 483-499; doi:10.3390/ma6020483
Received: 13 November 2012 / Revised: 10 January 2013 / Accepted: 22 January 2013 / Published: 5 February 2013
Cited by 9 | PDF Full-text (837 KB) | HTML Full-text | XML Full-text
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, [...] 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)
Open AccessReview Extraordinary Magnetoresistance in Semiconductor/Metal Hybrids: A Review
Materials 2013, 6(2), 500-516; doi:10.3390/ma6020500
Received: 4 December 2012 / Revised: 28 January 2013 / Accepted: 29 January 2013 / Published: 13 February 2013
Cited by 5 | PDF Full-text (534 KB) | HTML Full-text | XML Full-text
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 [...] 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
Open AccessReview A Review of Aspects of Oxidative Hair Dye Chemistry with Special Reference to N-Nitrosamine Formation
Materials 2013, 6(2), 517-534; doi:10.3390/ma6020517
Received: 5 January 2013 / Revised: 23 January 2013 / Accepted: 28 January 2013 / Published: 13 February 2013
Cited by 6 | PDF Full-text (212 KB) | HTML Full-text | XML Full-text
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 [...] 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 NOx 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)
Open AccessReview Solubilization of Hydrophobic Dyes in Surfactant Solutions
Materials 2013, 6(2), 580-608; doi:10.3390/ma6020580
Received: 14 January 2013 / Revised: 10 February 2013 / Accepted: 15 February 2013 / Published: 21 February 2013
Cited by 33 | PDF Full-text (779 KB) | HTML Full-text | XML Full-text
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, [...] 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)
Open AccessReview Advanced Strategies for Articular Cartilage Defect Repair
Materials 2013, 6(2), 637-668; doi:10.3390/ma6020637
Received: 7 January 2013 / Revised: 6 February 2013 / Accepted: 16 February 2013 / Published: 22 February 2013
Cited by 16 | PDF Full-text (1160 KB) | HTML Full-text | XML Full-text
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 [...] 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)

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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
Materials 2013, 6(2), 565-569; doi:10.3390/ma6020565
Received: 12 February 2013 / Accepted: 13 February 2013 / Published: 19 February 2013
PDF Full-text (25 KB) | HTML Full-text | XML Full-text
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 [...] 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

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