bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photonic Crystals on Erbium doped tellurite Thin Films for Broadband Enhanced Photoluminescence at Near Infrared
Authors: Lin Pao T. , Vanhoutte M. , Hu J. , Patel N. S. , Singh V. , Cai Y. , Camacho R. , Michel J. , Kimerling L. C. , Agarwal A. , Dimas Clara 
Published: November 2012

ABSTRACTTwo dimensional Er3+-TeO2 thin film photonics crystals (PhCs) are fabricated. These PhCs demonstrate broadband enhancement of PL emission at near Infrared (NIR). The PhC structures are written by dual beam focused ion beam (FIB). Highly uniformed patterns with smooth surfaces are observed. A pattern resolution better than hundred nanometers is achieved. PhCs arrays with photonic lattice constants from 350 nm to 1700 nm are examined in order to optimize the PL extraction efficiency. Strong photoluminescence around 1530 nm is observed by 488-532 nm lasers pumping. A confocal microscopy with spectrometer is used to capture the broadband PL signals from individual PhC array.The emission enhancement factor and spectral dependent extraction ratio are analyzed to find the interaction between PL lightwave and PhC structures. By optimize the PhC structures, 1500 um-1560 um broadband PL is successfully converted between the PL emission layer and the external cavity. A 60 % enhancement of surface extraction efficiency is achieved when PhC with periodicity a=800 nm is applied. When photonic lattice constants a are smaller than the critical periodicity 600 nm, the PL light becomes confined inside the thin film layer. Simulation is also performed by two dimensional finite difference time domain (FDTD) calculation in order to explain the experimental observed anisotropic PL enhancements.The broadband PL enhancement enables Er3+-TeO2 PhCs thin film as a potential light source for three dimensional integrated photonic circuits.
Biomimetic Hemo-compatible Surfaces of Polyurethane by Grafting Copolymer Brushes of Poly(ethylene glycol) and Poly(phosphorylcholine methacrylate)
Authors: Yang Dazhi , Feng Yakai , Behl Marc , Lendlein Andreas , Zhao Haiyang , Khan Musammir , Guo Jintang 
Published: November 2012

ABSTRACTPolyurethanes (PU) have been widely used as biomaterial in recent years, while thrombus may still occur when contacting with blood especially for extended period of time. Poly(ethylene glycol) (PEG) and phosphorylcholine (PC)-based polymers are commonly employed for surface modification to create protein repellent surfaces. PC-based polymers have been investigated as biomimetic materials because PC is the major component in the outer layer of cell membranes. In this study, the biomimetic copolymer brush of PEG-b-poly(2-methacryloyloxyethyl phosphorylcholine) on PU surfaces was synthesized via atom transfer radical polymerization (ATRP) with a surface initiator. The flexible PEG chain was 200 g·mol-1, while the poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) chain length was controlled by the ratio of monomer to sacrificial initiator in solution. The topology of the modified surfaces was characterized by the phase image of atomic force microscopy (AFM) to study the synergy effect between PEG chains and poly(MPC) chains. The unmodified and modified surfaces were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), water contact angle and platelet adhesion. The results demonstrated that efficient grafting of PEG-b-poly(MPC) brushes on the surfaces was achieved. The PU surfaces modified with PEG and phosphorylcholine zwitterionic brushes showed effective resistance to platelet adhesion and high hemocompatibility in vitro. These PEG and PC-grafted PU materials might be potentially applied in blood-contacting materials or devices due to their good mechanical and hemocompatible properties.
Nanotube-Enhanced Aerosol-Jet Printed Electronics for Embedded Sensing of Composite Structural Health
Authors: Zhao Da , Liu Tao , Zhang Mei , Chen Jen-Ming , Wang Ben 
Published: November 2012

ABSTRACTInnovative printing technology enables fine feature deposition (below 10μm) of electronic materials onto low-temperature, non-planar substrates without masks. This could be a promising technology to meet the requirements of present and future microelectronic systems. Silver nanoparticles (NP) ink is widely used for printed electronics; however, its electrical conductivity is low compared to bulk materials. In order to improve the electrical conductivity of printed tracks for the aerosol printing technique, we developed a novel carbon nanotubes (CNTs)/silver NP ink by mechanical stirring and sonication. The produced sample inks with different concentration of CNTs that were printed with Aerosol Jet® printing system. We found that the CNTs bridged the defects in some printed silver lines, thereby lowering the electrical resistivity by 38%. However, no further improvements were observed with a higher CNT concentration in the silver NP ink samples. We hypothesize that CNT bridges connects the defects thus decreasing the resistivity of printed silver lines when CNT concentration is under the percolation level. However, when it is above a concentration threshold, the resistivity of printed silver lines stops decreasing and even increases because of Schottky barrier effect.
Development of Objective Type Atomic Force Microsocopy for PSISCM-Nanoindentation Combined System.
Authors: Fujitsuka M. , Yamaguchi M. , Ueno S. 
Published: November 2012

ABSTRACTNanoindentation test is known as instrumented indentation test (IIT) in the nano range for hardness and material parameters (ISO14577). It is a simple and effective method for evaluating the mechanical properties such as elasticity/stiffness, hardness and adhesion. Generally IIT is the method that doesn’t have to observe the residual impression. However, it is necessary to observe the residual impression and surface of test piece to obtain the material behavior such as pile-up/sink-in, crack. In past work, the phase shifting interferometric scanning confocal microscope (PSISCM)-nanoindenataion combined system was developed to obtain the tilt of surface and the geometrical shape of residual impression that are deeper than one micron. This system is useful to obtain the geometrical shape of the surface of test piece in macro and micro range. However, it is well known that the results of nanoindentation test become unstable in the nano range.In this work, authors focused the geometry observation system for nanoindentation system. Confirmation the capability of PSISCM system and development of objective type atomic force microscopy to obtain the geometrical shape in nano range are examined. The AFM that has an excellent performance is developed by SII nanotechnology Inc. Japan, and it built into system. In many cases, it performs enough to observe the residual impression and the surface of the test piece. This system uses three methods to obtain the geometrical shape of surface in each range. Generally, AFM has the observation range at about several microns. It is difficult to search the small residual impression by only AFM. Before the observation of AFM, the observation area should be selected by using PSISCM. New measurement tool using PSISCM and AFM to obtain the surface geometry from macro range to nano range is proposed. This tool is very simple, quick and useful tool.
Surface Structure Characterization and Electrochemical Characteristics of Carbon-Coated Lithium Iron Phosphate (C-LiFePO4) Particles
Authors: Sun Xiangcheng , Sun Kai , Cui Bo 
Published: November 2012

ABSTRACTCarbon-coated lithium iron phosphate (C-LiFePO4) particles have been synthesized by a solid-state reaction process. Particles surface morphology, olivine-type phase structures and the carbon shell-core structures are investigated in details by transmission electron microscopy (TEM, HRTEM) imaging and electron diffraction (SAED) patterns. Homogenous features of carbon coating of the LiFePO4 particles surface are obviously revealed. HR-TEM imaging and X-ray photoelectron spectroscopy (XPS) confirmed an amorphous sp2 type conducting coating layer on the surface of LiFePO4 particles. Particles shape and size showed the clear single-crystal nature of the phospho-olivine type structures with the rough spherical features of 50-250 nm size range. The characteristics of sp2 type carbon-coating on the LiFePO4 particles surfaces allows improving the electrical conductivity and reducing the diffusion path of the lithium ions, as directly evidenced from electrochemical tests of charge-discharge cycling.
Temperature and Frequency Dependencies of Ferroelectric Properties in Rhombohedral Epitaxial Pb(Zr,Ti)O3 Films with Perfect (111) Orientations Grown on CaF2 Substrates.
Authors: Ehara Yoshitaka , Yamada Tomoaki , Iijima Takashi , Valanoor Nagarajan , Funakubo Hiroshi 
Published: November 2012

ABSTRACTPerfectly (111)-oriented rhombohedral Pb(Zr, Ti)O3 [PZT] films were successfully grown on (111) CaF2 substrates. These films have the polar-axis perpendicular to the substrate surface without non-180o domains. Well saturated polarization (P) –electric field (E) hysteresis loops were observed at various frequencies and temperatures. Temperature dependence of the saturation polarization (Psat.) was in good agreement with the estimated one by Haun et al. using phenomenological approach but did not strongly depend on the measured frequencies. On the other hand, the coercive field (Ec) increased with decreasing temperature and with increasing the measurement frequency.
Colloidal CuInS2 Based Nanocrystals /TiO2 Nanotube Arrays Composite Solar Cells Fabrication and Testing
Authors: Reddy Vanga R. , Wilson William , Eyi Rick , Wu Jiang , Manasreh M. O. , Dixion John , Wang Andrew 
Published: November 2012

ABSTRACTTo develop alternative and low cost photovoltaic technologies we have synthesized CuInS2 nanocrystals with tunable optical properties and characterization was carried out thoroughly with TEM, SEM, EDAX and XRD. Furthermore large self-organized arrays of TiO2 nanotubes were fabricated on Ti foil followed by simple electrochemical anodization technique and characterized their structure by SEM and then for the first time coupled both the nanocrystals and nanotubes to form a p-n junction type photovoltaic device. The current-voltage (I-V) characteristics of photovoltaic cells were measured to test the proof of concept. Some preliminary experiments showed that device generates some current upon illumination. However, in our case we fabricated a device without sandwiching any buffer or barrier layers in between nanocrystals and nanotube arrays. We have been optimizing our solar cells efficiency by improving quality of nanotubes and nanocrystals. Some of the interesting finding are presented and discussed.
Poly(lactide-co-glycolide)-Hydroxyapatite Composites: The Development of Osteoinductive Scaffolds for Bone Regenerative Engineering
Authors: Deng Meng , Cushnie Emily K. , Lv Qing , Laurencin Cato T. 
Published: November 2012

ABSTRACTRegenerative engineering represents a new multidisciplinary paradigm to engineer complex tissues, organs, or organ systems through the integration of tissue engineering with advanced materials science, stem cell science and developmental biology. While possessing elements of tissue engineering, regenerative medicine, and morphogenesis, regenerative engineering is distinct from these individual disciplines since it specifically focuses on the integration and subsequent response of stem cells to biomaterials. One goal of regenerative engineering is the design of materials capable of inducing associated cells toward highly specialized functions. For example, the interaction of cells with calcium phosphate surfaces has proven to be an important signaling modality in promoting osteogenic differentiation. A biodegradable polymer-ceramic composite system has been developed from poly(lactide-co-glycolide) andin situsynthesized hydroxyapatite based on the three-dimensional sintered microsphere matrix platform. We have systematically optimized scaffold physico-chemical, mechanical, and structural properties for bone tissue regeneration applications by varying several parameters such as solution pH, polymer:ceramic ratio, sintering time and sintering temperature. The bioactivity of composite scaffolds is attributed to their ability to deliver calcium ions to surrounding medium and allow for reprecipitation of calcium phosphate on the scaffold surface. Furthermore, the composite scaffolds have demonstrated increased loading capacity of osteoinductive growth factor (BMP-2) and a more sustained release profile due to a greater number of adsorption sites provided by the ionic calcium and phosphate groups as well as a larger matrix surface area.In vitrocell studies were performed to investigate the efficacy of this composite system to induce osteogenic differentiation of human adipose-derived stem cells. Cells cultured on the ceramic containing scaffolds exhibited significantly higher expression of osteoblastic markers and greater extracellular matrix mineralization than non-ceramic containing scaffolds, indicating the potential for the ceramic phase to promote osteogenic differentiation. In addition, loaded BMP-2 retained its bioactivity as a mitogen and osteoinductive agent during the differentiation of adipose-derived stem cells into mature osteoblasts.In vivoevaluation using a critical-sized ulnar defect model in New Zealand white rabbits demonstrated the ability of composite scaffolds to support cellular infiltration throughout the scaffold pore structure and vascularization of new tissue, as well as facilitate formation of newly mineralized bone tissue. The work described herein provides strong evidence for the potential of polymer-ceramic composite scaffolds to function as osteoinductive bone graft substitutes, and paves the way for future development of advanced tissue-inducing materials.
Preparation of Nanoparticle-containing Aligned Collagen Fibers for Dense Connective Tissue Repair and Regeneration
Authors: Cheng Xingguo , Desai Sapna A. 
Published: November 2012

ABSTRACTNanoparticles (NPs) loaded with human platelet-derived growth factor (h-PDGF) were prepared and characterized. These NPs were co-assembled with collagen to form highly aligned NP-collagen composite fibers by using an electrochemical process. PDGF can be released gradually from either NPs or aligned NP-collagen fibers. This investigation demonstrated a novel way to fabricate highly aligned composite fibers, which can locally release a growth factor in a controlled and gradual manner, potentially avoiding the fast clearance of the growth factor from the implantation site. Thus, the aligned NP-collagen fiber is a novel and promising implantation material for tendon/ligament repair and regeneration.
Preparation and In Vitro Characterization of Polycaprolactone and Demineralized Bone Matrix Scaffolds
Authors: Moloye Titilayo , Batich Christopher 
Published: November 2012

ABSTRACTCylindrical porous polycaprolactone (PCL) scaffolds containing 25, 35, and 50 wt% demineralized bone matrix (DBM) were fabricated using a salt-leaching method for application in bone engineering. In the present work, PCL-DBM scaffolds were monitored for calcium and phosphorus deposition in both deionized (DI) water and simulated body fluid (SBF) for time periods of 5, 10, 15, and 20 days at 37°C under constant rotation. An in vitro assessment of the bioactivity of synthetic materials using SBF under physiological conditions can be used as a barometer of scaffold behavior in vivo. DBM, an osteoinductive material, was used to gauge if there was a correlation between the concentration of DBM within a scaffold and the apatite formation on its surface. Biochemical assays, alizarin red S staining, and scanning electron microscopy (SEM) with elemental analysis of calcium and phosphorus were consistent in that they confirmed that PCL scaffolds containing 35 wt% DBM in SBF at 14 days post-immersion showed signs of early apatite formation.
Neuronal Outgrowth and Differentiation on Poly(glycerol sebacate)
Authors: Casey Meghan E. , Jedlicka Sabrina S. 
Published: November 2012

ABSTRACTThe importance of the extracellular mechanical environment in stem cell differentiation has been extensively studied over the last decade. In neuronal cell differentiation, matrix stiffness and neurite outgrowth have been correlated, highlighting the impact of matrix effects on neuronal cell morphology. In addition, on materials that approach the physiological mechanical properties of brain tissue, neurons from mixed phenotype primary cultures will prevail. However, if the same mixed culture is grown on polystyrene, glial populations are more prevalent. Enhancing the understanding of these differentiation processes will further expand the ability to design materials for neuronal implants that are conducive to neuronal survival, resist glial scarring and promote neurite outgrowth and cell connectivity. Specifically, elastomers such as poly(glycerol sebacate) (PGS) hold promise in neuronal tissue engineering, due to their mechanical tunability. PGS is biocompatible, biodegradable and possesses mechanical properties similar to that of living tissue. Neuronal cell differentiation was studied on PGS, using P19 embryonic carcinoma cells, which can be differentiated into a neuronal phenotype using retinoic acid. Varying cure temperatures of PGS including 120°, 140° and 165°C were selected, which equate to an elastic modulus of 0.07, 0.43 and 2.30 MPa respectively. Cells were characterized via immunocytochemistry. A primarily astrocytic population, with limited neuronal differentiation and neurite outgrowth were observed on the PGS 120°C. Cells grown on PGS 140°C demonstrated marked neurite outgrowth, with an increase in neuronal cells. Cells grown on the PGS 165°C exhibited the largest population of neurons, with significant neurite outgrowth. These results indicate that substrate mechanical properties do impact neuronal differentiation, but that a material with a Young’s modulus similar to that of neuronal tissue (PGS 120°C) may not necessarily be the most conducive to in vitro differentiation.
Ultrafast Charge Carrier Dynamics and Photoelectrochemical Properties of Hydrogen-treated TiO2 Nanowire Arrays
Authors: Wheeler Damon A. , Wang Gongming , Fitzmorris Bob C. , Adams Staci A. , Li Yat , Zhang Jin Z. 
Published: November 2012

ABSTRACTHere we report studies of photoelectrochemical (PEC) properties and ultrafast charge carrier relaxation dynamics of hydrogen-treated TiO2 (H:TiO2) nanowire arrays. PEC measurements showed the photocurrent density of the H:TiO2 was approximately double that of TiO2, attributed to increased donor density due to the formation of oxygen vacancies in H:TiO2 due to hydrogen treatment Charge carrier dynamics of H:TiO2, measured using fs transient absorption spectroscopy, showed a fast decay of ∼20 ps followed by slower decay persisting to tens of picoseconds. The fast decay is attributed to bandedge electron-hole recombination and the slower decay is attributed to recombination from trap states. Visible absorption is attributed to either electronic transitions from the valence band to oxygen vacancy states or from oxygen vacancy states to the conduction band of the TiO2, which is supported by incident photon to current conversion efficiency (IPCE) data. H:TiO2 represents a unique material with improved photoelectrochemical properties for applications including PEC water splitting, solar cells, and photocatalysis.
Synthesis and characterization of carbon nanotube\iron oxide hybrids
Authors: Souza Lígia P. , Ferreira Thais M. , Franco Juliana R. , de Oliveira Sergio , Geraldo Viviany , Munford Maxmiliano L. , Ferlauto Andre S. 
Published: November 2012

ABSTRACTIn this work, the synthesis of carbon nanotubes/hematite hybrids was investigated. The hybrids were produced by solvothermal method and a systematic study exploring different reaction parameters such as treatment duration, temperature and solvent was performed. Results from different characterization techniques demonstrate that the CNTs were effectively decorated with hematite (α-Fe2O3). The size and concentration of the NPs varies with the reaction parameters and the smallest obtained NPs have ∼100 nm diameter. It was demonstrated that translucent and homogeneous thin films made of the resulting hybrid material can be deposited on indium-tin oxide substrates by electrophoretic deposition or by vaccum filtration.
Breast Adenocarcinoma Cell Functions on Nanopatterned PLGA Surfaces
Authors: Zhang Lijuan , Webster Thomas J. 
Published: November 2012

ABSTRACTThe effects of poly (lactic-co-glycolic acid) (PLGA) surface properties on lung epithelial carcinoma cell functions were previously identified. Results demonstrated decreased lung epithelial carcinoma cell vascular endothelial growth factor (VEGF) synthesis on 23 nm surface featured PLGA compared to the PLGA nano-smooth substrates. To investigate the universality of nanopatterned PLGA on inhibiting cancer cell functions, here, breast epithelial adenocarcinoma cell, MCF-7, early functions were determined on different PLGA nanometer surface topographies. Moreover, the viability of healthy breast cells was determined by an MTT assay to investigate the effects of nanopatterning on healthy breast cell growth. Atomic force microscopy (AFM) verified the varied nanotopographies on the PLGA surfaces prepared in this study. Importantly, results demonstrated significantly decreased breast adenocarcinoma cell functions (including decreased proliferation rate and decreased VEGF synthesis) on 23 nm featured PLGA surfaces compared to the other PLGA surface topographies (specifically, nano-smooth, 300 nm and 400 nm surface featured PLGA surfaces). In contrast, healthy breast epithelial cell studies indicated a 24% higher cell proliferation on the 23 nm featured PLGA surfaces compared to all other PLGA samples. In summary, these results provided further insights into understanding the role surface nanotopographies can have on selectively inhibiting cancer cell functions for a wide range of anti-cancer applications.
PbS Nanoparticles: Synthesis, Supercritical Fluid Deposition, and Optical Studies
Authors: Wang Joanna S. , Ullrich Bruno , Brown Gail J. 
Published: November 2012

ABSTRACTLead sulfide (PbS) nanoparticles (NPs) of different sizes (2.0 nm - 14.4 nm) have been synthesized in our laboratory. By using those NPs, we formed colloidal films on glass and GaAs substrates employing a specialized supercritical fluid CO2 (sc-CO2) deposition method. The deposited films contain only the PbS NPs and the protecting group of oleic acids and require no polymer matrix. The NP films are solvent free, environmentally stable, and show good adhesion to the substrates. The sc-CO2 deposition process can deposit films ranging in thickness from a few monolayers, in well ordered arrays, up to 0.5 μm or greater. The photoluminescence (PL) properties of these nano-structured films were studied with Fourier transformation infrared spectroscopy from 5 K up to 300 K.