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Materials, Volume 3, Issue 3 (March 2010), Pages 1497-2195

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Research

Jump to: Review

Open AccessArticle Photoluminescence and Band Alignment of Strained GaAsSb/GaAs QW Structures Grown by MBE on GaAs
Materials 2010, 3(3), 1497-1508; doi:10.3390/ma3031497
Received: 1 January 2010 / Revised: 24 February 2010 / Accepted: 24 February 2010 / Published: 26 February 2010
Cited by 8 | PDF Full-text (447 KB) | HTML Full-text | XML Full-text
Abstract
An in-depth optimization of growth conditions and investigation of optical properties including discussions on band alignment of GaAsSb/GaAs quantum well (QW) on GaAs by molecular beam epitaxy (MBE) are reported. Optimal MBE growth temperature of GaAsSb QW is found to be 470 [...] Read more.
An in-depth optimization of growth conditions and investigation of optical properties including discussions on band alignment of GaAsSb/GaAs quantum well (QW) on GaAs by molecular beam epitaxy (MBE) are reported. Optimal MBE growth temperature of GaAsSb QW is found to be 470 ± 10 °C. GaAsSb/GaAs QW with Sb content ~0.36 has a weak type-II band alignment with valence band offset ratio QV ~1.06. A full width at half maximum (FWHM) of ~60 meV in room temperature (RT) photoluminescence (PL) indicates fluctuation in electrostatic potential to be less than 20 meV. Samples grown under optimal conditions do not exhibit any blue shift of peak in RT PL spectra under varying excitation. Full article
(This article belongs to the Special Issue Luminescent Materials)
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Open AccessArticle High-Pressure Study of Anatase TiO2
Materials 2010, 3(3), 1509-1514; doi:10.3390/ma3031509
Received: 28 January 2010 / Revised: 25 February 2010 / Accepted: 26 February 2010 / Published: 1 March 2010
Cited by 8 | PDF Full-text (1102 KB) | HTML Full-text | XML Full-text
Abstract
We report resistivity and thermo-electric power measurements of the anatase phase of TiO2under pressure up to 2.3 GPa. Despite its transparent appearance, the single crystal of anatase exhibits a metallic-like resistivity above 60 K, at all pressures. The rather high [...] Read more.
We report resistivity and thermo-electric power measurements of the anatase phase of TiO2under pressure up to 2.3 GPa. Despite its transparent appearance, the single crystal of anatase exhibits a metallic-like resistivity above 60 K, at all pressures. The rather high value of the thermo-electric power at room temperature points to complex transport mechanism in this phase. Full article
(This article belongs to the Special Issue Novel Thermoelectric Materials and Applications)
Open AccessArticle Toward High-Performance Coatings for Biomedical Devices: Study on Plasma-Deposited Fluorocarbon Films and Ageing in PBS
Materials 2010, 3(3), 1515-1532; doi:10.3390/ma3031515
Received: 8 January 2010 / Revised: 17 February 2010 / Accepted: 24 February 2010 / Published: 2 March 2010
Cited by 8 | PDF Full-text (482 KB) | HTML Full-text | XML Full-text
Abstract
High performance coatings tailored to medical devices represent a recognised approach to modulate surface properties. Plasma-deposited fluorocarbon films have been proposed as a potential stent coating. Previous studies have shown promising adhesion properties: the 35 nm-thick film sustained plastic deformation up to [...] Read more.
High performance coatings tailored to medical devices represent a recognised approach to modulate surface properties. Plasma-deposited fluorocarbon films have been proposed as a potential stent coating. Previous studies have shown promising adhesion properties: the 35 nm-thick film sustained plastic deformation up to 25% such as induced during the clinical implantation. In this study, the compositional and morphological changes of plasma-deposited fluorocarbon films were examined during ageing in a pseudo-physiological medium, a phosphate buffer solution (PBS), by angle-resolved XPS, FT-IR data and AFM images. The evolution of the ageing process is discussed: defluorination and crosslinking yielded an oxidized protective top layer onto the films, which showed further degradation. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
Open AccessArticle Influence of Yttrium on the Thermal Stability of Ti-Al-N Thin Films
Materials 2010, 3(3), 1573-1592; doi:10.3390/ma3031573
Received: 5 January 2010 / Revised: 18 February 2010 / Accepted: 3 March 2010 / Published: 4 March 2010
Cited by 12 | PDF Full-text (1429 KB) | HTML Full-text | XML Full-text
Abstract
Ti1-xAlxN coated tools are commonly used in high-speed machining, where the cutting edge of an end-mill or insert is exposed to temperatures up to 1100 °C. Here, we investigate the effect of Yttrium addition on the thermal stability [...] Read more.
Ti1-xAlxN coated tools are commonly used in high-speed machining, where the cutting edge of an end-mill or insert is exposed to temperatures up to 1100 °C. Here, we investigate the effect of Yttrium addition on the thermal stability of Ti1-xAlxN coatings. Reactive DC magnetron sputtering of powder metallurgically prepared Ti0.50Al0.50, Ti0.49Al0.49Y0.02, and Ti0.46Al0.46Y0.08 targets result in the formation of single-phase cubic (c) Ti0.45Al0.55N, binary cubic/wurtzite c/w-Ti0.41Al0.57Y0.02N and singe-phase w-Ti0.38Al0.54Y0.08N coatings. Using pulsed DC reactive magnetron sputtering for the Ti0.49Al0.49Y0.02 target allows preparing single-phase c-Ti0.46Al0.52Y0.02N coatings. By employing thermal analyses in combination with X-ray diffraction and transmission electron microscopy investigations of as deposited and annealed (in He atmosphere) samples, we revealed that Y effectively retards the decomposition of the Ti1-x-yAlxYyN solid-solution to higher temperatures and promotes the precipitation of c-TiN, c-YN, and w-AlN. Due to their different microstructure and morphology already in the as deposited state, the hardness of the coatings decreases from ~35 to 22 GPa with increasing Y-content and increasing wurtzite phase fraction. Highest peak hardness of ~38 GPa is obtained for the Y-free c-Ti0.45Al0.55N coating after annealing at Ta = 950 °C, due to spinodal decomposition. After annealing above 1000 °C the highest hardness is obtained for the 2 mol % YN containing c-Ti0.46Al0.52Y0.02N coating with ~29 and 28 GPa for Ta = 1150 and 1200 °C, respectively. Full article
(This article belongs to the Special Issue Advances in Materials Science)
Open AccessArticle Crystal and Electronic Structures, Photoluminescence Properties of Eu2+-Doped Novel Oxynitride Ba4Si6O16-3x/2Nx
Materials 2010, 3(3), 1692-1708; doi:10.3390/ma3031692
Received: 7 January 2010 / Revised: 12 February 2010 / Accepted: 5 March 2010 / Published: 8 March 2010
Cited by 13 | PDF Full-text (992 KB) | HTML Full-text | XML Full-text
Abstract
The crystal structure and the photoluminescence properties of novel green Ba4-yEuySi6O16-3x/2Nx phosphors were investigated. The electronic structures of the Ba4Si6O16 host were calculated by first principles pseudopotential method [...] Read more.
The crystal structure and the photoluminescence properties of novel green Ba4-yEuySi6O16-3x/2Nx phosphors were investigated. The electronic structures of the Ba4Si6O16 host were calculated by first principles pseudopotential method based on density functional theory. The results reveal that the top of the valence bands are dominated by O-2p states hybridized with Ba-6s and Si-3p states, while the conduction bands are mainly determined by Ba-6s states for the host, which is an insulator with a direct energy gap of 4.6 eV at Γ. A small amount of nitrogen can be incorporated into the host to replace oxygen and forms Ba4-yEuySi6O16-3x/2Nx solid solutions crystallized in a monoclinic (space group P21/c, Z = 2) having the lattice parameters a = 12.4663(5) Å, b = 4.6829(2) Å, c = 13.9236(6) Å, and β = 93.61(1)°, with a maximum solubility of nitrogen at about x = 0.1. Ba4Si6O16-3x/2Nx:Eu2+ exhibits efficient green emission centered at 515–525 nm varying with the Eu2+ concentration when excited under UV to 400 nm. Furthermore, the incorporation of nitrogen can slightly enhance the photoluminescence intensity. Excitation in the UV-blue spectral range (λexc = 375 nm), the absorption and quantum efficiency of Ba4-yEuySi6O16-3x/2Nx (x = 0.1, y = 0.2) reach about 80% and 46%, respectively. Through further improvement of the thermal stability, novel green phosphor of Ba4-yEuySi6O16-3x/2Nx is promising for application in white UV-LEDs. Full article
(This article belongs to the Special Issue Luminescent Materials)
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Open AccessCommunication Application of Diamond Nanoparticles in Low-Energy Neutron Physics
Materials 2010, 3(3), 1768-1781; doi:10.3390/ma3031768
Received: 4 January 2010 / Revised: 9 February 2010 / Accepted: 8 March 2010 / Published: 10 March 2010
Cited by 11 | PDF Full-text (174 KB) | HTML Full-text | XML Full-text
Abstract
Diamond, with its exceptionally high optical nuclear potential and low absorption cross-section, is a unique material for a series of applications in VCN (very cold neutron) physics and techniques. In particular, powder of diamond nanoparticles provides the best reflector for neutrons in [...] Read more.
Diamond, with its exceptionally high optical nuclear potential and low absorption cross-section, is a unique material for a series of applications in VCN (very cold neutron) physics and techniques. In particular, powder of diamond nanoparticles provides the best reflector for neutrons in the complete VCN energy range. It allowed also the first observation of quasi-specular reflection of cold neutrons (CN) from disordered medium. Effective critical velocity for such a quasi-specular reflection is higher than that for the best super-mirror. Nano-diamonds survive in high radiation fluxes; therefore they could be used, under certain conditions, in the vicinity of intense neutron sources. Full article
(This article belongs to the Special Issue The New Diamond Age?)
Open AccessArticle Tissue Equivalents Based on Cell-Seeded Biodegradable Microfluidic Constructs
Materials 2010, 3(3), 1833-1844; doi:10.3390/ma3031833
Received: 28 January 2010 / Revised: 6 March 2010 / Accepted: 11 March 2010 / Published: 15 March 2010
Cited by 5 | PDF Full-text (1550 KB) | HTML Full-text | XML Full-text
Abstract
One of the principal challenges in the field of tissue engineering and regenerative medicine is the formation of functional microvascular networks capable of sustaining tissue constructs. Complex tissues and vital organs require a means to support oxygen and nutrient transport during the [...] Read more.
One of the principal challenges in the field of tissue engineering and regenerative medicine is the formation of functional microvascular networks capable of sustaining tissue constructs. Complex tissues and vital organs require a means to support oxygen and nutrient transport during the development of constructs both prior to and after host integration, and current approaches have not demonstrated robust solutions to this challenge. Here, we present a technology platform encompassing the design, construction, cell seeding and functional evaluation of tissue equivalents for wound healing and other clinical applications. These tissue equivalents are comprised of biodegradable microfluidic scaffolds lined with microvascular cells and designed to replicate microenvironmental cues necessary to generate and sustain cell populations to replace dermal and/or epidermal tissues lost due to trauma or disease. Initial results demonstrate that these biodegradable microfluidic devices promote cell adherence and support basic cell functions. These systems represent a promising pathway towards highly integrated three-dimensional engineered tissue constructs for a wide range of clinical applications. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Open AccessCommunication Charge-Transfer Controlled Crystallization of a Model Oligomer for Donor-Acceptor-Polythiophenes
Materials 2010, 3(3), 1904-1912; doi:10.3390/ma3031904
Received: 25 January 2010 / Revised: 4 March 2010 / Accepted: 16 March 2010 / Published: 17 March 2010
Cited by 6 | PDF Full-text (306 KB) | HTML Full-text | XML Full-text
Abstract
A model donor-acceptor oligomer consisting of benzodithiophene-diketone and thiophene has been investigated with regard to its molecular packing and opto-electronic properties. The crystal structure suggests that the packing is dominated by charge-transfer interactions between the electron-rich part of the molecule and the [...] Read more.
A model donor-acceptor oligomer consisting of benzodithiophene-diketone and thiophene has been investigated with regard to its molecular packing and opto-electronic properties. The crystal structure suggests that the packing is dominated by charge-transfer interactions between the electron-rich part of the molecule and the electron-poor part. A series of observations corroborate this assumption, among them are a charge-transfer band in the film absorption spectra and exceptionally low π-π distances. A detailed analysis of the energetic levels of the present system reveals that only the HOMO level of the acceptor is shifted by conjugation to the donor. The results can contribute to the development of improved materials for organic electronics. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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Open AccessArticle A Mechanism of DC-AC Conversion in the Organic Thyristor
Materials 2010, 3(3), 2027-2036; doi:10.3390/ma3032027
Received: 5 February 2010 / Revised: 18 February 2010 / Accepted: 16 March 2010 / Published: 19 March 2010
Cited by 4 | PDF Full-text (641 KB) | HTML Full-text | XML Full-text
Abstract
The charge ordered organic salt θ-(BEDT-TTF)2CsZn(SCN)4 exhibits a giant nonlinear conduction at low temperatures. The voltage-current characteristics of this compound are similar to those of a thyristor device, after which we named it the organic thyristor. This material [...] Read more.
The charge ordered organic salt θ-(BEDT-TTF)2CsZn(SCN)4 exhibits a giant nonlinear conduction at low temperatures. The voltage-current characteristics of this compound are similar to those of a thyristor device, after which we named it the organic thyristor. This material shows current oscillation in the presense of dc voltage, which arises from a mechanism different from conventional oscillating circuits, because the oscillation appears in a sample that does not show negative derivative resistance. We have performed a standard circuit analysis, and show that the voltage-current curve is “blurred” in the high current region, and the oscillation occurs in the blurred region. This type of oscillation has never been reported, and a possible origin for this is suggested. Full article
(This article belongs to the Special Issue Organic Electronic Materials)
Open AccessArticle Synthesis and Properties of Octithiophene Dication Sterically Segregated by Annelation with Bicyclo[2.2.2]octene Units
Materials 2010, 3(3), 2037-2052; doi:10.3390/ma3032037
Received: 29 January 2010 / Revised: 13 February 2010 / Accepted: 16 March 2010 / Published: 19 March 2010
Cited by 14 | PDF Full-text (496 KB) | HTML Full-text | XML Full-text
Abstract
Octithiophene sterically segregated by annelation with bicyclo[2.2.2]octene (BCO) units was synthesized to study the unimolecular properties of longer oligothiophene dications. For the preparation of such longer oligomers, a new route for the synthesis of the monomer annelated with BCO unit at the [...] Read more.
Octithiophene sterically segregated by annelation with bicyclo[2.2.2]octene (BCO) units was synthesized to study the unimolecular properties of longer oligothiophene dications. For the preparation of such longer oligomers, a new route for the synthesis of the monomer annelated with BCO unit at the 3,4-positions of thiophene ring was developed. Attempted synthesis of octithiophene 1(8T) fully annelated with BCO units was hampered by low solubility of the product, and octithiophene 2(8T) having octyl groups instead of the BCO units at the second rings from the both ends of 1(8T) was synthesized to solve the solubility problem. Neutral 2(8T) has a lower planarity due to the steric repulsion between the octyl substituents and the neighboring thiophene units. However, dication 2(8T)2+, which was obtained as a stable salt by chemical two-electron oxidation with NO+SbF6-, has a planar quinoid structure, as judged from a linear correlation between the inverse chain length and the absorption energy for 1(nT)2+ (n = 3,4,6) and 2(8T)2+. Based on the comparison with the calculated absorption spectra and the result of ESR inactive properties, 2(8T)2+ appears to have a singlet ground state with open-shell biradical character rather than a closed-shell singlet structure. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
Open AccessArticle Thermal and Optical Properties of CdS Nanoparticles in Thermotropic Liquid Crystal Monomers
Materials 2010, 3(3), 2069-2086; doi:10.3390/ma3032069
Received: 10 December 2009 / Revised: 15 February 2010 / Accepted: 17 March 2010 / Published: 19 March 2010
Cited by 18 | PDF Full-text (1097 KB) | HTML Full-text | XML Full-text
Abstract
Two new mesogenic monomers, namely 3,3’-dimethoxy-4,4’-di(hydroxyhexoxy)-N-benzylidene-o-Tolidine (Ia) and 4,4’-di(6-hydroxyhexoxy)-N-benzylidene-o-Tolidine (IIa), were reacted with cadmium sulfide (CdS) via an in situ chemical precipitation method in ethanol to produce CdS nanocomposites. A series of different mass compositions of CdS with [...] Read more.
Two new mesogenic monomers, namely 3,3’-dimethoxy-4,4’-di(hydroxyhexoxy)-N-benzylidene-o-Tolidine (Ia) and 4,4’-di(6-hydroxyhexoxy)-N-benzylidene-o-Tolidine (IIa), were reacted with cadmium sulfide (CdS) via an in situ chemical precipitation method in ethanol to produce CdS nanocomposites. A series of different mass compositions of CdS with Ia and IIa ranging from 0.1:1.0 to 1.0:1.0 (w/w) were prepared and characterized using X-ray Diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), Polarizing Optical Microscopy (POM) and Differential Scanning Calorimetry (DSC), X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence Spectroscopy (PL). XRD showed that the broad peaks are ascribed to the formation of cubic CdS nanoparticles in both Ia and IIa. The average particle size for both nanocomposites was less than 5 nm with a narrower size distribution when compared with pure CdS nanoparticles. The analyses from POM and DSC demonstrated that mass composition from 0.1:1.0 up to 0.5:1.0 of CdS:Ia nanocomposites showed their enantiotropic nematic phase. On the other hand, polarizing optical microscopy (POM) for IIa nanocomposites showed that the liquid crystal property vanished completely when the mass composition was at 0.2:1.0. PL emissions for CdS: Ia or IIa nanocomposites indicated deep trap defects occurred in these both samples. The PL results revealed that addition of CdS to Ia monomers suppressed the photoluminescence intensity of Ia. However, the introduction of CdS to IIa monomers increased the photoluminescence and was at a maximum when the mass composition was 0.3:1.0, then decreased in intensity as more CdS was added. The XPS results also showed that the stoichiometric ratios of S/Cd were close to 1.0:1.0 for both types of nanocomposites for a mass composition of 1.0:1.0 (CdS:matrix). Full article
(This article belongs to the Special Issue Progress in Nanomaterials Preparation)

Review

Jump to: Research

Open AccessReview Azine- and Azole-Functionalized Oligo´ and Polythiophene Semiconductors for Organic Thin-Film Transistors
Materials 2010, 3(3), 1533-1558; doi:10.3390/ma3031533
Received: 1 February 2010 / Revised: 26 February 2010 / Accepted: 1 March 2010 / Published: 3 March 2010
Cited by 16 | PDF Full-text (970 KB) | HTML Full-text | XML Full-text
Abstract
In the organic electronics research field, several strategies have been used to modulate the transport properties of thiophene-derived semiconductors via sequential functionalization of their π-conjugated cores. This review summarizes the major design and synthetic strategies for tuning thiophene-containing small molecule and polymer [...] Read more.
In the organic electronics research field, several strategies have been used to modulate the transport properties of thiophene-derived semiconductors via sequential functionalization of their π-conjugated cores. This review summarizes the major design and synthetic strategies for tuning thiophene-containing small molecule and polymer properties by introducing electron-deficient nitrogen-containing azine and azole moieties. Several examples are presented which elucidate the structural, optical, and electronic consequences of incorporating these electron-deficient fragments in the conjugated skeletons, particularly relating to applications in organic thin-film transistors. Full article
(This article belongs to the Special Issue Organic Electronic Materials)
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Open AccessReview Preparation of Dispersed Platinum Nanoparticles on a Carbon Nanostructured Surface Using Supercritical Fluid Chemical Deposition
Materials 2010, 3(3), 1559-1572; doi:10.3390/ma3031559
Received: 31 October 2009 / Revised: 30 December 2009 / Accepted: 18 January 2010 / Published: 3 March 2010
Cited by 10 | PDF Full-text (6876 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a method of forming platinum (Pt) nanoparticles using a metal organic chemical fluid deposition (MOCFD) process employing a supercritical fluid (SCF), and have demonstrated the synthesis of dispersed Pt nanoparticles on the surfaces of carbon nanowalls (CNWs), two-dimensional carbon [...] Read more.
We have developed a method of forming platinum (Pt) nanoparticles using a metal organic chemical fluid deposition (MOCFD) process employing a supercritical fluid (SCF), and have demonstrated the synthesis of dispersed Pt nanoparticles on the surfaces of carbon nanowalls (CNWs), two-dimensional carbon nanostructures, and carbon nanotubes (CNTs). By using SCF-MOCFD with supercritical carbon dioxide as a solvent of metal-organic compounds, highly dispersed Pt nanoparticles of 2 nm diameter were deposited on the entire surface of CNWs and CNTs. The SCF-MOCFD process proved to be effective for the synthesis of Pt nanoparticles on the entire surface of intricate carbon nanostructures with narrow interspaces. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Development of Fabrication Methods of Filler/Polymer Nanocomposites: With Focus on Simple Melt-Compounding-Based Approach without Surface Modification of Nanofillers
Materials 2010, 3(3), 1593-1619; doi:10.3390/ma3031593
Received: 28 December 2009 / Revised: 12 February 2010 / Accepted: 1 March 2010 / Published: 4 March 2010
Cited by 23 | PDF Full-text (2448 KB) | HTML Full-text | XML Full-text
Abstract
Many attempts have been made to fabricate various types of inorganic nanoparticle-filled polymers (filler/polymer nanocomposites) by a mechanical or chemical approach. However, these approaches require modification of the nanofiller surfaces and/or complicated polymerization reactions, making them unsuitable for industrial-scale production of the [...] Read more.
Many attempts have been made to fabricate various types of inorganic nanoparticle-filled polymers (filler/polymer nanocomposites) by a mechanical or chemical approach. However, these approaches require modification of the nanofiller surfaces and/or complicated polymerization reactions, making them unsuitable for industrial-scale production of the nanocomposites. The author and coworkers have proposed a simple melt-compounding method for the fabrication of silica/polymer nanocomposites, wherein silica nanoparticles without surface modification were dispersed through the breakdown of loose agglomerates of colloidal nano-silica spheres in a kneaded polymer melt. This review aims to discuss experimental techniques of the proposed method and its advantages over other developed methods. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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Open AccessReview Biophysical Cueing and Vascular Endothelial Cell Behavior
Materials 2010, 3(3), 1620-1639; doi:10.3390/ma3031620
Received: 1 February 2010 / Revised: 25 February 2010 / Accepted: 4 March 2010 / Published: 5 March 2010
Cited by 9 | PDF Full-text (214 KB) | HTML Full-text | XML Full-text
Abstract
Human vascular endothelial cells (VEC) line the vessels of the body and are critical for the maintenance of vessel integrity and trafficking of biochemical cues. They are fundamental structural elements and are central to the signaling environment. Alterations in the normal functioning [...] Read more.
Human vascular endothelial cells (VEC) line the vessels of the body and are critical for the maintenance of vessel integrity and trafficking of biochemical cues. They are fundamental structural elements and are central to the signaling environment. Alterations in the normal functioning of the VEC population are associated with a number of vascular disorders among which are some of the leading causes of death in both the United States and abroad. VECs attach to their underlying stromal elements through a specialization of the extracellular matrix, the basement membrane. The basement membrane provides signaling cues to the VEC through its chemical constituents, by serving as a reservoir for cytoactive factors and through its intrinsic biophysical properties. This specialized matrix is composed of a topographically rich 3D felt-like network of fibers and pores on the nano (1–100 nm) and submicron (100–1,000 nm) size scale. The basement membrane provides biophysical cues to the overlying VECs through its intrinsic topography as well as through its local compliance (relative stiffness). These biophysical cues modulate VEC adhesion, migration, proliferation, differentiation, and the cytoskeletal signaling network of the individual cells. This review focuses on the impact of biophysical cues on VEC behaviors and demonstrates the need for their consideration in future vascular studies and the design of improved prosthetics. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Open AccessReview New Development in the Preparation of Micro/Nano-Wires of Molecular (Magnetic) Conductors
Materials 2010, 3(3), 1640-1673; doi:10.3390/ma3031640
Received: 19 January 2010 / Revised: 10 February 2010 / Accepted: 3 March 2010 / Published: 8 March 2010
Cited by 6 | PDF Full-text (3370 KB) | HTML Full-text | XML Full-text
Abstract
A lot of molecular (magnetic) conductors are prepared largely using charge-transfer (CT) salts of donor molecules with acceptor molecules or nonmagnetic or magnetic anions such as metal halides and oxides; their CT salts are usually obtained as bulk crystals, which are used [...] Read more.
A lot of molecular (magnetic) conductors are prepared largely using charge-transfer (CT) salts of donor molecules with acceptor molecules or nonmagnetic or magnetic anions such as metal halides and oxides; their CT salts are usually obtained as bulk crystals, which are used to elucidate the electrical conducting (magnetic) properties. In contrast, a small number of micro/nano-crystals of the molecular (magnetic) conductors, especially micro/nano-wires, are known, of which highly conducting nanowires are necessary as a key component in the development of the next generation of nano-size transistors and spin-transistors. Very recently, we succeeded in preparing highly conductive micro/nano-wires of CT salts between bent donor molecules developed by one of the author’s group and magnetic FeX4 (X = Cl, Br) ions: (1) by electrochemical oxidation of the bent donor molecules with a silicon wafer electrode coated with a phospholipid multi-lamellar structure as well as, (ii) by electrochemical oxidation of the bent donor molecules with a large arc structure, in the presence of NBu4FeX4 supporting electrolytes. This article reviews template-free and template-assisted methods developed so far for the preparation of micro/nano-wires of molecular (magnetic) conductors along with our new methods. The conducting properties of these micro/nano-wires are compared with those of the corresponding bulk crystals. Full article
(This article belongs to the Special Issue Organic Electronic Materials)
Open AccessReview Nanotechnology in Dental Sciences: Moving towards a Finer Way of Doing Dentistry
Materials 2010, 3(3), 1674-1691; doi:10.3390/ma3031674
Received: 20 December 2009 / Revised: 11 February 2010 / Accepted: 5 March 2010 / Published: 8 March 2010
Cited by 17 | PDF Full-text (1736 KB) | HTML Full-text | XML Full-text
Abstract
Nanotechnologies are predicted to revolutionize: (a) the control over materials properties at ultrafine scales; and (b) the sensitivity of tools and devices applied in various scientific and technological fields. In this short review, we argue that dentistry will be no exception to [...] Read more.
Nanotechnologies are predicted to revolutionize: (a) the control over materials properties at ultrafine scales; and (b) the sensitivity of tools and devices applied in various scientific and technological fields. In this short review, we argue that dentistry will be no exception to this trend. Here, we present a dynamic view of dental tissues, an adoption of which may lead to finer, more effective and minimally invasive reparation approaches. By doing so, we aim at providing insights into some of the breakthroughs relevant to understanding the genesis of dental tissues at the nanostructural level or generating dental materials with nanoscale critical boundaries. The lineage of the progress of dental science, including the projected path along the presumed nanotechnological direction of research and clinical application is mentioned too. We conclude by claiming that dentistry should follow the trend of probing matter at nanoscale that currently dominates both materials and biological sciences in order to improve on the research strategies and clinical techniques that have traditionally rested on mechanistic assumptions. Full article
(This article belongs to the Special Issue Dental Materials)
Open AccessReview Imogolite Reinforced Nanocomposites: Multifaceted Green Materials
Materials 2010, 3(3), 1709-1745; doi:10.3390/ma3031709
Received: 30 December 2009 / Revised: 2 February 2010 / Accepted: 1 March 2010 / Published: 9 March 2010
Cited by 18 | PDF Full-text (6361 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an overview on recent developments of imogolite reinforced nanocomposites, including fundamental structure, synthesis/purification of imogolite, physicochemical properties of nanocomposites and potential applications in industry. The naturally derived nanotubular material of imogolite represents a distinctive class of nanofiller for industrially [...] Read more.
This paper presents an overview on recent developments of imogolite reinforced nanocomposites, including fundamental structure, synthesis/purification of imogolite, physicochemical properties of nanocomposites and potential applications in industry. The naturally derived nanotubular material of imogolite represents a distinctive class of nanofiller for industrially significant polymer. The incompatibility between the surface properties of inorganic nanofiller and organic matrix has prompted the need to surface modify the imogolite. Early problems in increasing the binding properties of surface modifier to imogolite have been overcome by using a phosphonic acid group. Different approaches have been used to gain better control over the dispersal of nanofiller and to further improve the physicochemical properties of nanocomposites. Among these, polymer grafting, in situ synthesis of imogolite in polymer matrix, and spin-assembly are some of the promising methods that will be described herein. This imogolite reinforced nanocomposite of enhanced optical and mechanical properties, and with unique biological and electronic properties, is expected to become an important category of hybrid material that shows potential for industrial applications. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
Open AccessReview Injectable, Biodegradable Hydrogels for Tissue Engineering Applications
Materials 2010, 3(3), 1746-1767; doi:10.3390/ma3031746
Received: 19 November 2009 / Revised: 16 February 2010 / Accepted: 8 March 2010 / Published: 10 March 2010
Cited by 122 | PDF Full-text (1073 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogels have many different applications in the field of regenerative medicine. Biodegradable, injectable hydrogels could be utilized as delivery systems, cell carriers, and scaffolds for tissue engineering. Injectable hydrogels are an appealing scaffold because they are structurally similar to the extracellular matrix [...] Read more.
Hydrogels have many different applications in the field of regenerative medicine. Biodegradable, injectable hydrogels could be utilized as delivery systems, cell carriers, and scaffolds for tissue engineering. Injectable hydrogels are an appealing scaffold because they are structurally similar to the extracellular matrix of many tissues, can often be processed under relatively mild conditions, and may be delivered in a minimally invasive manner. This review will discuss recent advances in the field of injectable hydrogels, including both synthetic and native polymeric materials, which can be potentially used in cartilage and soft tissue engineering applications. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
Open AccessReview Hybrid Integrated Platforms for Silicon Photonics
Materials 2010, 3(3), 1782-1802; doi:10.3390/ma3031782
Received: 1 February 2010 / Revised: 3 March 2010 / Accepted: 11 March 2010 / Published: 12 March 2010
Cited by 85 | PDF Full-text (956 KB) | HTML Full-text | XML Full-text
Abstract
A review of recent progress in hybrid integrated platforms for silicon photonics is presented. Integration of III-V semiconductors onto silicon-on-insulator substrates based on two different bonding techniques is compared, one comprising only inorganic materials, the other technique using an organic bonding agent. [...] Read more.
A review of recent progress in hybrid integrated platforms for silicon photonics is presented. Integration of III-V semiconductors onto silicon-on-insulator substrates based on two different bonding techniques is compared, one comprising only inorganic materials, the other technique using an organic bonding agent. Issues such as bonding process and mechanism, bonding strength, uniformity, wafer surface requirement, and stress distribution are studied in detail. The application in silicon photonics to realize high-performance active and passive photonic devices on low-cost silicon wafers is discussed. Hybrid integration is believed to be a promising technology in a variety of applications of silicon photonics. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)
Open AccessReview Surface Engineering and Patterning Using Parylene for Biological Applications
Materials 2010, 3(3), 1803-1832; doi:10.3390/ma3031803
Received: 1 February 2010 / Accepted: 11 March 2010 / Published: 15 March 2010
Cited by 44 | PDF Full-text (2719 KB) | HTML Full-text | XML Full-text
Abstract
Parylene is a family of chemically vapour deposited polymer with material properties that are attractive for biomedicine and nanobiotechnology. Chemically inert parylene “peel-off” stencils have been demonstrated for micropatterning biomolecular arrays with high uniformity, precise spatial control down to nanoscale resolution. Such [...] Read more.
Parylene is a family of chemically vapour deposited polymer with material properties that are attractive for biomedicine and nanobiotechnology. Chemically inert parylene “peel-off” stencils have been demonstrated for micropatterning biomolecular arrays with high uniformity, precise spatial control down to nanoscale resolution. Such micropatterned surfaces are beneficial in engineering biosensors and biological microenvironments. A variety of substituted precursors enables direct coating of functionalised parylenes onto biomedical implants and microfluidics, providing a convenient method for designing biocompatible and bioactive surfaces. This article will review the emerging role and applications of parylene as a biomaterial for surface chemical modification and provide a future outlook. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Open AccessReview Application of Nanodiamonds in Biomolecular Mass Spectrometry
Materials 2010, 3(3), 1845-1862; doi:10.3390/ma3031845
Received: 21 December 2009 / Revised: 11 February 2010 / Accepted: 12 March 2010 / Published: 15 March 2010
Cited by 7 | PDF Full-text (852 KB) | HTML Full-text | XML Full-text
Abstract
The combination of nanodiamond (ND) with biomolecular mass spectrometry (MS) makes rapid, sensitive detection of biopolymers from complex biosamples feasible. Due to its chemical inertness, optical transparency and biocompatibility, the advantage of NDs in MS study is unique. Furthermore, functionalization on the [...] Read more.
The combination of nanodiamond (ND) with biomolecular mass spectrometry (MS) makes rapid, sensitive detection of biopolymers from complex biosamples feasible. Due to its chemical inertness, optical transparency and biocompatibility, the advantage of NDs in MS study is unique. Furthermore, functionalization on the surfaces of NDs expands their application in the fields of proteomics and genomics for specific requirements greatly. This review presents methods of MS analysis based on solid phase extraction and elution on NDs and different application examples including peptide, protein, DNA, glycan and others. Owing to the quick development of nanotechnology, surface chemistry, new MS methods and the intense interest in proteomics and genomics, a huge increase of their applications in biomolecular MS analysis in the near future can be predicted. Full article
(This article belongs to the Special Issue The New Diamond Age?)
Open AccessReview Collagen-Based Biomaterials for Tissue Engineering Applications
Materials 2010, 3(3), 1863-1887; doi:10.3390/ma3031863
Received: 2 February 2010 / Revised: 9 March 2010 / Accepted: 11 March 2010 / Published: 16 March 2010
Cited by 164 | PDF Full-text (284 KB) | HTML Full-text | XML Full-text
Abstract
Collagen is the most widely distributed class of proteins in the human body. The use of collagen-based biomaterials in the field of tissue engineering applications has been intensively growing over the past decades. Multiple cross-linking methods were investigated and different combinations with [...] Read more.
Collagen is the most widely distributed class of proteins in the human body. The use of collagen-based biomaterials in the field of tissue engineering applications has been intensively growing over the past decades. Multiple cross-linking methods were investigated and different combinations with other biopolymers were explored in order to improve tissue function. Collagen possesses a major advantage in being biodegradable, biocompatible, easily available and highly versatile. However, since collagen is a protein, it remains difficult to sterilize without alterations to its structure. This review presents a comprehensive overview of the various applications of collagen-based biomaterials developed for tissue engineering, aimed at providing a functional material for use in regenerative medicine from the laboratory bench to the patient bedside. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
Open AccessReview Polyoxometalates in Oxidative Delignification of Chemical Pulps: Effect on Lignin
Materials 2010, 3(3), 1888-1903; doi:10.3390/ma3031888
Received: 23 December 2009 / Revised: 8 March 2010 / Accepted: 12 March 2010 / Published: 16 March 2010
Cited by 10 | PDF Full-text (305 KB) | HTML Full-text | XML Full-text
Abstract
Chemical pulps are produced by chemical delignification of lignocelluloses such as wood or annual non-woody plants. After pulping (e.g., kraft pulping), the remaining lignin is removed by bleaching to produce a high quality, bright paper. The goal of bleaching is to remove [...] Read more.
Chemical pulps are produced by chemical delignification of lignocelluloses such as wood or annual non-woody plants. After pulping (e.g., kraft pulping), the remaining lignin is removed by bleaching to produce a high quality, bright paper. The goal of bleaching is to remove lignin from the pulp without a negative effect on the cellulose; for this reason, delignification should be performed in a highly selective manner. New environmentally-friendly alternatives to conventional chlorine-based bleaching technologies (e.g., oxygen, ozone, or peroxide bleaching) have been suggested or implemented. In an attempt to find inorganic agents that mimic the action of highly selective lignin-degrading enzymes and that can be applicable in industrial conditions, the researchers have focused on polyoxometalates (POMs), used either as regenerable redox reagents (in anaerobic conditions) or as catalysts (in aerobic conditions) of oxidative delignification. The aim of this paper is to review the basic concepts of POM delignification in these two processes. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessReview Freeze-Casting of Porous Biomaterials: Structure, Properties and Opportunities
Materials 2010, 3(3), 1913-1927; doi:10.3390/ma3031913
Received: 5 February 2010 / Revised: 24 February 2010 / Accepted: 16 March 2010 / Published: 17 March 2010
Cited by 64 | PDF Full-text (700 KB) | HTML Full-text | XML Full-text
Abstract
The freeze-casting of porous materials has received a great deal of attention during the past few years. This simple process, where a material suspension is simply frozen and then sublimated, provides materials with unique porous architectures, where the porosity is almost a [...] Read more.
The freeze-casting of porous materials has received a great deal of attention during the past few years. This simple process, where a material suspension is simply frozen and then sublimated, provides materials with unique porous architectures, where the porosity is almost a direct replica of the frozen solvent crystals. This review focuses on the recent results on the process and the derived porous structures with regards to the biomaterials applications. Of particular interest is the architecture of the materials and the versatility of the process, which can be readily controlled and applied to biomaterials applications. A careful control of the starting formulation and processing conditions is required to control the integrity of the structure and resulting properties. Further in vitro and in vivo investigations are required to validate the potential of this new class of porous materials. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
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Open AccessReview Targeted Delivery of Protein Drugs by Nanocarriers
Materials 2010, 3(3), 1928-1980; doi:10.3390/ma3031928
Received: 28 December 2009 / Revised: 16 February 2010 / Accepted: 15 March 2010 / Published: 17 March 2010
Cited by 41 | PDF Full-text (4132 KB) | HTML Full-text | XML Full-text
Abstract
Recent advances in biotechnology demonstrate that peptides and proteins are the basis of a new generation of drugs. However, the transportation of protein drugs in the body is limited by their high molecular weight, which prevents the crossing of tissue barriers, and [...] Read more.
Recent advances in biotechnology demonstrate that peptides and proteins are the basis of a new generation of drugs. However, the transportation of protein drugs in the body is limited by their high molecular weight, which prevents the crossing of tissue barriers, and by their short lifetime due to immuno response and enzymatic degradation. Moreover, the ability to selectively deliver drugs to target organs, tissues or cells is a major challenge in the treatment of several human diseases, including cancer. Indeed, targeted delivery can be much more efficient than systemic application, while improving bioavailability and limiting undesirable side effects. This review describes how the use of targeted nanocarriers such as nanoparticles and liposomes can improve the pharmacokinetic properties of protein drugs, thus increasing their safety and maximizing the therapeutic effect. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Open AccessReview End-Grafted Polymer Chains onto Inorganic Nano-Objects
Materials 2010, 3(3), 1981-2026; doi:10.3390/ma3031981
Received: 20 January 2010 / Accepted: 11 March 2010 / Published: 18 March 2010
Cited by 28 | PDF Full-text (991 KB) | HTML Full-text | XML Full-text
Abstract
Organic/inorganic nanohybrid materials have attracted particular scientific and technological interest because they combine the properties of the organic and the inorganic component. Inorganic nanoparticles exhibit interesting electrical, optical, magnetic and/or catalytic properties, which are related with their nano-scale dimensions. However, their high [...] Read more.
Organic/inorganic nanohybrid materials have attracted particular scientific and technological interest because they combine the properties of the organic and the inorganic component. Inorganic nanoparticles exhibit interesting electrical, optical, magnetic and/or catalytic properties, which are related with their nano-scale dimensions. However, their high surface-to-volume ratio often induces agglomeration and leads to the loss of their attractive properties. Surface modification of the inorganic nano-objects with physically or chemically end-tethered polymer chains has been employed to overcome this problem. Covalent tethered polymer chains are realized by three different approaches: the “grafting to”, the “grafting from” and the “grafting through” method. This article reviews the synthesis of end-grafted polymer chains onto inorganic nanoparticles using “controlled/living” polymerization techniques, which allow control over the polymer characteristics and the grafting density of the end-tethered polymer chains. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)
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Open AccessReview Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles
Materials 2010, 3(3), 2053-2068; doi:10.3390/ma3032053
Received: 26 December 2009 / Revised: 14 January 2010 / Accepted: 18 March 2010 / Published: 19 March 2010
Cited by 25 | PDF Full-text (1344 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE) doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP) that [...] Read more.
This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE) doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP) that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminescent properties. We discuss the synthesis, properties, and application of heavy metal fluorides; specifically LaF3:RE and PbF2, and group IIA fluorides. Particular attention is given to the synthesis of core/shell nanoparticles, including selectively RE-doped LaF3/LaF3, and CaF2/CaF2 core/(multi-)shell nanoparticles, and the CaF2-LaF3 system. Full article
(This article belongs to the Special Issue Luminescent Materials)
Open AccessReview Recent Progress on Enyne Metathesis: Its Application to Syntheses of Natural Products and Related Compounds
Materials 2010, 3(3), 2087-2140; doi:10.3390/ma3032087
Received: 28 December 2009 / Revised: 26 February 2010 / Accepted: 16 March 2010 / Published: 19 March 2010
Cited by 42 | PDF Full-text (996 KB) | HTML Full-text | XML Full-text
Abstract
Olefin metathesis using ruthenium carbene complexes is a useful method in synthetic organic chemistry. Enyne metathesis is also catalyzed by these complexes and various carbo- and heterocycles could be synthesized from the corresponding enynes. Dienyne metathesis, cross enyne metathesis and ring-opening enyne [...] Read more.
Olefin metathesis using ruthenium carbene complexes is a useful method in synthetic organic chemistry. Enyne metathesis is also catalyzed by these complexes and various carbo- and heterocycles could be synthesized from the corresponding enynes. Dienyne metathesis, cross enyne metathesis and ring-opening enyne metathesis have been further developed. Various complicated compounds, such as the natural products and the related biologically active substances, could be synthesized using these metatheses reactions. Skeletal reorganization using the transition metals and metallotropic rearrangement are also discussed. Full article
(This article belongs to the Special Issue Organometallic Compounds)
Open AccessReview Nitrogen Doped Carbon Nanotubes from Organometallic Compounds: A Review
Materials 2010, 3(3), 2141-2171; doi:10.3390/ma3032141
Received: 11 February 2010 / Revised: 1 March 2010 / Accepted: 15 March 2010 / Published: 22 March 2010
Cited by 49 | PDF Full-text (1171 KB) | HTML Full-text | XML Full-text
Abstract
Nitrogen doped carbon nanotubes (N-CNTs) have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded in a CNT. These properties include modified chemical reactivity [...] Read more.
Nitrogen doped carbon nanotubes (N-CNTs) have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded in a CNT. These properties include modified chemical reactivity and modified conductivity and mechanical properties. A range of methodologies have been devised to synthesize N-CNTs. One of the procedures uses a floating catalyst in which an organometallic complex is decomposed in the gas phase in the presence of a nitrogen containing reactant to give N-CNTs. Most studies have been limited to ferrocene, ring substituted ferrocene and Fe(CO)5. This review covers the synthesis (and properties) of N-CNTs and other shaped carbon nanomaterials (SCNMs) produced using organometallic complexes. It summarizes the effects that physical parameters such as temperature, pressure, gas flow rates, type and concentration of N source etc. have on the N-CNT type, size and yields as well as the nitrogen content incorporated into the tubes that are produced from organometallic complexes. Proposed growth models for N-CNT synthesis are also reported. Full article
(This article belongs to the Special Issue Organometallic Compounds)
Open AccessReview Light Converting Inorganic Phosphors for White Light-Emitting Diodes
Materials 2010, 3(3), 2172-2195; doi:10.3390/ma3032172
Received: 6 January 2010 / Revised: 23 February 2010 / Accepted: 15 March 2010 / Published: 22 March 2010
Cited by 176 | PDF Full-text (1095 KB) | HTML Full-text | XML Full-text
Abstract
White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue [...] Read more.
White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm) and nUV (380-400 nm) LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+) is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development. Full article
(This article belongs to the Special Issue Luminescent Materials)

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