Materials

552 KiB

Open AccessArticle

Neural Stem Cell Spreading on Lipid Based Artificial Cell Surfaces, Characterized by Combined X-ray and Neutron Reflectometry

by Martin Huth, Samira Hertrich, Gabor Mezo, Emilia Madarasz and Bert Nickel

Materials 2010, 3(11), 4994-5006; https://doi.org/10.3390/ma3114994 - 22 Nov 2010

Cited by 1 | Viewed by 11224

Abstract

We developed a bioadhesive coating based on a synthetic peptide-conjugate (AK-cyclo[RGDfC]) which contains multiples of the arginyl-glycyl-aspartic acid (RGD) amino acid sequence. Biotinylated AK-cyclo[RGDfC] is bound to a supported lipid bilayer via a streptavidin interlayer. Layering, hydration and packing of the coating is [...] Read more.

We developed a bioadhesive coating based on a synthetic peptide-conjugate (AK-cyclo[RGDfC]) which contains multiples of the arginyl-glycyl-aspartic acid (RGD) amino acid sequence. Biotinylated AK-cyclo[RGDfC] is bound to a supported lipid bilayer via a streptavidin interlayer. Layering, hydration and packing of the coating is quantified by X-ray and neutron reflectometry experiments. AK-cyclo[RGDfC] binds to the streptavidin interlayer in a stretched-out on edge configuration. The highly packed configuration with only 12% water content maximizes the number of accessible adhesion sites. Enhanced cell spreading of neural stem cells was observed for AK-cyclo[RGDfC] functionalized bilayers. Due to the large variety of surfaces which can be coated by physisorption of lipid bilayers, this approach is of general interest for the fabrication of biocompatible surfaces. Full article

(This article belongs to the Special Issue Supported Lipid Membrane Surface Modifications and Applications)

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2445 KiB

Open AccessArticle

SAXS Studies of TiO₂ Nanoparticles in Polymer Electrolytes and in Nanostructured Films

by Aleksandra Turković, Pavo Dubček, Krunoslav Juraić, Antun Drašner and Sigrid Bernstorff

Materials 2010, 3(11), 4979-4993; https://doi.org/10.3390/ma3114979 - 22 Nov 2010

Cited by 5 | Viewed by 10443

Abstract

Polymer electrolytes as nanostructured materials are very attractive components for batteries and opto-electronic devices. (PEO)₈ZnCl₂ polymer electrolytes were prepared from PEO and ZnCl₂. The nanocomposites (PEO)₈ZnCl₂/TiO₂ themselves contained TiO₂ nanograins. In this [...] Read more.

Polymer electrolytes as nanostructured materials are very attractive components for batteries and opto-electronic devices. (PEO)₈ZnCl₂ polymer electrolytes were prepared from PEO and ZnCl₂. The nanocomposites (PEO)₈ZnCl₂/TiO₂ themselves contained TiO₂ nanograins. In this work, the influence of the TiO₂ nanograins on the morphology and ionic conductivity of the nanocomposite was systematically studied by transmission small-angle X-ray scattering (SAXS) simultaneously recorded with wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) at the synchrotron ELETTRA. Films containing nanosized grains of titanium dioxide (TiO₂) are widely used in the research of optical and photovoltaic devices. The TiO₂ films, prepared by chemical vapor deposition and e-beam epitaxy, were annealed in hydrogen atmospheres in the temperature range between 20 °C and 900 °C in order to study anatase-rutile phase transition at 740 °C. Also, grazing-incidence small angle X-ray scattering (GISAXS) spectra for each TiO₂ film were measured in reflection geometry at different grazing incident angles. Environmentally friendly galvanic cells, as well as solar cells of the second generation, are to be constructed with TiO₂ film as working electrode, and nanocomposite polymer as electrolyte. Full article

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2113 KiB

Open AccessArticle

Mechanisms of Texture Development in Lead-Free Piezoelectric Ceramics with Perovskite Structure Made by the Templated Grain Growth Process

by Toshio Kimura, Yuan Yi and Fumito Sakurai

Materials 2010, 3(11), 4965-4978; https://doi.org/10.3390/ma3114965 - 22 Nov 2010

Cited by 23 | Viewed by 9443

Abstract

The mechanisms of texture development were examined for BaTiO₃ and a (K,Na,Li)(Nb,Ta)O₃ solid solution made by the templated grain growth method, and compared with the mechanism in Bi_0.5(Na,K)_0.5TiO₃. The dominant mechanism was different in each [...] Read more.

The mechanisms of texture development were examined for BaTiO₃ and a (K,Na,Li)(Nb,Ta)O₃ solid solution made by the templated grain growth method, and compared with the mechanism in Bi_0.5(Na,K)_0.5TiO₃. The dominant mechanism was different in each material; grain boundary migration in BaTiO₃, solid state spreading in Bi_0.5(Na,K)_0.5TiO₃, and abnormal grain growth in the (K,Na,Li)(Nb,Ta)O₃ solid solution. The factor determining the dominant mechanism is the degree of smoothness of surface structure at an atomic level. Full article

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1588 KiB

Open AccessReview

Recent Progress of Ferroelectric-Gate Field-Effect Transistors and Applications to Nonvolatile Logic and FeNAND Flash Memory

by Shigeki Sakai and Mitsue Takahashi

Materials 2010, 3(11), 4950-4964; https://doi.org/10.3390/ma3114950 - 18 Nov 2010

Cited by 65 | Viewed by 16928

Abstract

We have investigated ferroelectric-gate field-effect transistors (FeFETs) with Pt/SrBi₂Ta₂O₉/(HfO₂)_x(Al₂O₃)_1−x (Hf-Al-O) and Pt/SrBi₂Ta₂O₉/HfO₂ gate stacks. The fabricated FeFETs have excellent data retention [...] Read more.

We have investigated ferroelectric-gate field-effect transistors (FeFETs) with Pt/SrBi₂Ta₂O₉/(HfO₂)_x(Al₂O₃)_1−x (Hf-Al-O) and Pt/SrBi₂Ta₂O₉/HfO₂ gate stacks. The fabricated FeFETs have excellent data retention characteristics: The drain current ratio between the on- and off-states of a FeFET was more than 2 × 10⁶ after 12 days, and the decreasing rate of this ratio was so small that the extrapolated drain current ratio after 10 years is larger than 1 × 10⁵. A fabricated self-aligned gate Pt/SrBi₂Ta₂O₉/Hf-Al-O/Si FET revealed a sufficiently large drain current ratio of 2.4 × 10⁵ after 33.5 day, which is 6.5 × 10⁴ after 10 years by extrapolation. The developed FeFETs also revealed stable retention characteristics at an elevated temperature up to 120 °C and had small transistor threshold voltage (V_th) distribution. The V_th can be adjusted by controlling channel impurity densities for both n-channel and p-channel FeFETs. These performances are now suitable to integrated circuit application with nonvolatile functions. Fundamental properties for the applications to ferroelectric-CMOS nonvolatile logic-circuits and to ferroelectric-NAND flash memories are demonstrated. Full article

(This article belongs to the Special Issue Advances in Ferroelectric & Piezoelectric Materials)

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602 KiB

Open AccessArticle

Solvent Vapor Treatment Effects on Poly(3-hexylthiophene) Thin Films and its Application for Interpenetrating Heterojunction Organic Solar Cells

by Tetsuro Hori, Varutt Kittichungchit, Hiroki Moritou, Hitoshi Kubo, Akihiko Fujii and Masanori Ozaki

Materials 2010, 3(11), 4939-4949; https://doi.org/10.3390/ma3114939 - 15 Nov 2010

Cited by 7 | Viewed by 7887

Abstract

The solvent vapor treatment (SVT) for poly(3-hexylthiophene) (PAT6) films and its application to interpenetrating heterojunction organic solar cells have been studied. It was found that SVT could improve the crystallinity and electrical characteristics of the PAT6 films. We fabricated organic solar cells with [...] Read more.

The solvent vapor treatment (SVT) for poly(3-hexylthiophene) (PAT6) films and its application to interpenetrating heterojunction organic solar cells have been studied. It was found that SVT could improve the crystallinity and electrical characteristics of the PAT6 films. We fabricated organic solar cells with an interpenetrating structure of PAT6 and fullerenes utilizing the SVT process, and discuss the improved performance of the solar cells by taking the film crystallinity, optical properties, and morphology into consideration. Full article

(This article belongs to the Special Issue Solar Energy Materials)

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396 KiB

Open AccessReview

Review of the Two-Step H₂O/CO₂-Splitting Solar Thermochemical Cycle Based on Zn/ZnO Redox Reactions

by Peter G. Loutzenhiser, Anton Meier and Aldo Steinfeld

Materials 2010, 3(11), 4922-4938; https://doi.org/10.3390/ma3114922 - 12 Nov 2010

Cited by 168 | Viewed by 14961

Abstract

This article provides a comprehensive overview of the work to date on the two‑step solar H₂O and/or CO₂ splitting thermochemical cycles with Zn/ZnO redox reactions to produce H₂ and/or CO, i.e., synthesis gas—the precursor to renewable liquid hydrocarbon fuels. [...] Read more.

This article provides a comprehensive overview of the work to date on the two‑step solar H₂O and/or CO₂ splitting thermochemical cycles with Zn/ZnO redox reactions to produce H₂ and/or CO, i.e., synthesis gas—the precursor to renewable liquid hydrocarbon fuels. The two-step cycle encompasses: (1) The endothermic dissociation of ZnO to Zn and O₂ using concentrated solar energy as the source for high-temperature process heat; and (2) the non-solar exothermic oxidation of Zn with H₂O/CO₂to generate H₂/CO, respectively; the resulting ZnO is then recycled to the first step. An outline of the underlying science and the technological advances in solar reactor engineering is provided along with life cycle and economic analyses. Full article

(This article belongs to the Special Issue Solar Energy Materials)

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246 KiB

Open AccessArticle

Photovoltaic Properties in Interpenetrating Heterojunction Organic Solar Cells Utilizing MoO₃ and ZnO Charge Transport Buffer Layers

by Tetsuro Hori, Hiroki Moritou, Naoki Fukuoka, Junki Sakamoto, Akihiko Fujii and Masanori Ozaki

Materials 2010, 3(11), 4915-4921; https://doi.org/10.3390/ma3114915 - 8 Nov 2010

Cited by 24 | Viewed by 11577

Abstract

Organic thin-film solar cells with a conducting polymer (CP)/fullerene (C₆₀) interpenetrating heterojunction structure, fabricated by spin-coating a CP onto a C₆₀ deposit thin film, have been investigated and demonstrated to have high efficiency. The photovoltaic properties of solar cells with [...] Read more.

Organic thin-film solar cells with a conducting polymer (CP)/fullerene (C₆₀) interpenetrating heterojunction structure, fabricated by spin-coating a CP onto a C₆₀ deposit thin film, have been investigated and demonstrated to have high efficiency. The photovoltaic properties of solar cells with a structure of indium-tin-oxide/C₆₀/ poly(3-hexylthiophene) (PAT6)/Au have been improved by the insertion of molybdenum trioxide (VI) (MoO₃) and zinc oxide charge transport buffer layers. The enhanced photovoltaic properties have been discussed, taking into consideration the ground-state charge transfer between PAT6 and MoO₃ by measurement of the differential absorption spectra and the suppressed contact resistance at the interface between the organic and buffer layers. Full article

(This article belongs to the Special Issue Solar Energy Materials)

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190 KiB

Open AccessArticle

Transparent Conducting Oxides for Photovoltaics: Manipulation of Fermi Level, Work Function and Energy Band Alignment

by Andreas Klein, Christoph Körber, André Wachau, Frank Säuberlich, Yvonne Gassenbauer, Steven P. Harvey, Diana E. Proffit and Thomas O. Mason

Materials 2010, 3(11), 4892-4914; https://doi.org/10.3390/ma3114892 - 2 Nov 2010

Cited by 376 | Viewed by 30162

Abstract

Doping limits, band gaps, work functions and energy band alignments of undoped and donor-doped transparent conducting oxides Zn₀, In₂O₃, and SnO₂ as accessed by X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) are summarized and compared. The presented [...] Read more.

Doping limits, band gaps, work functions and energy band alignments of undoped and donor-doped transparent conducting oxides Zn₀, In₂O₃, and SnO₂ as accessed by X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) are summarized and compared. The presented collection provides an extensive data set of technologically relevant electronic properties of photovoltaic transparent electrode materials and illustrates how these relate to the underlying defect chemistry, the dependence of surface dipoles on crystallographic orientation and/or surface termination, and Fermi level pinning. Full article

(This article belongs to the Special Issue Solar Energy Materials)

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672 KiB

Open AccessReview

Catalytic CVD Synthesis of Carbon Nanotubes: Towards High Yield and Low Temperature Growth

by Arnaud Magrez, Jin Won Seo, Rita Smajda, Marijana Mionić and László Forró

Materials 2010, 3(11), 4871-4891; https://doi.org/10.3390/ma3114871 - 1 Nov 2010

Cited by 139 | Viewed by 16495

Abstract

The catalytic chemical vapor deposition (CCVD) is currently the most flexible and economically attractive method for the growth of carbon nanotubes. Although its principle is simple, the precisely controlled growth of carbon nanotubes remains very complex because many different parameters influence the growth [...] Read more.

The catalytic chemical vapor deposition (CCVD) is currently the most flexible and economically attractive method for the growth of carbon nanotubes. Although its principle is simple, the precisely controlled growth of carbon nanotubes remains very complex because many different parameters influence the growth process. In this article, we review our recent results obtained on the synthesis of carbon nanotubes via CCVD. We discuss the role of the catalyst and the catalyst support. Our recent results obtained from the water assisted growth and the equimolar C₂H₂-CO₂ reaction are also discussed. Both procedures lead to significantly enhanced carbon nanotube growth. In particular, the latter allows growing carbon nanotubes on diverse substrate materials at low temperatures. Full article

(This article belongs to the Special Issue Progress in Nanomaterials Preparation)

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581 KiB

Open AccessArticle

Mapping Disorder in Polycrystalline Relaxors: A Piezoresponse Force Microscopy Approach

by Andrei L Kholkin, Dmitry A Kiselev, Igor K Bdikin, Andris Sternberg, Brahim Dkhil, Stephen Jesse, Oleg Ovchinnikov and Sergei V Kalinin

Materials 2010, 3(11), 4860-4870; https://doi.org/10.3390/ma3114860 - 28 Oct 2010

Cited by 16 | Viewed by 10516

Abstract

Relaxors constitute a large class of ferroelectrics where disorder is introduced by doping with ions of different size and valence, in order to maximize their useful properties in a broad temperature range. Polarization disorder in relaxors is typically studied by dielectric and scattering [...] Read more.

Relaxors constitute a large class of ferroelectrics where disorder is introduced by doping with ions of different size and valence, in order to maximize their useful properties in a broad temperature range. Polarization disorder in relaxors is typically studied by dielectric and scattering techniques that do not allow direct mapping of relaxor parameters, such as correlation length or width of the relaxation time spectrum. In this paper, we introduce a novel method based on measurements of local vibrations by Piezoresponse Force Microscopy (PFM) that detects nanoscale polarization on the relaxor surface. Random polarization patterns are then analyzed via local Fast Fourier Transform (FFT) and the FFT PFM parameters, such as amplitude, correlation radius and width of the spectrum of spatial correlations, are mapped along with the conventional topography. The results are tested with transparent (Pb, La) (Zr, Ti)O₃ ceramics where local disorder is due to doping with La³⁺. The conclusions are made about the distribution of the defects responsible for relaxor behavior and the role of the grain boundaries in the macroscopic response. Full article

(This article belongs to the Special Issue Advances in Ferroelectric & Piezoelectric Materials)

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Materials, Volume 3, Issue 11 (November 2010) – 10 articles , Pages 4860-5006

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